Categories
Cold War Brazil MB-3 Tamoyo Cold War Brazilian Armor

MB-3 Tamoyo 3

Brazil (1987-1991)
Main Battle Tank – 1 Built

Already from the start of the Tamoyo project for the Brazilian Army, there were requirements for a new tank which was to be armed with a 105 mm or 120 mm gun. As the Tamoyo project progressed, a split seemed to form, as the Brazilian Army was not in the position to buy a more advanced tank with a 105 mm. As such, the project seems to have split with the 90 mm armed Tamoyo 1 and 2 meant for the Brazilian Army, and the 105 mm armed Tamoyo 3 meant for export.

Whereas the Tamoyo 1 and 2 could still be seen as much improved M41 Walker Bulldogs, even though they were new and independent designs, the Tamoyo 3 was a significantly more serious project than a mere M41 redesign, and could compete with the tanks on the South American continent and with tanks of a similar weight class. The Tamoyo 3 was the apex of the Tamoyo program, being a true main battle tank in South America, and arguably a much better vehicle for Brazil than its EE-T1 counterpart.

The Tamoyo 3 came from a program that was designed for Brazil first and export second, while the EE-T1 was built for Saudi Arabia first and Brazil second or even more as an afterthought. Sadly, due to financial issues in Brazil and some opposition from the Brazilian Army, Brazil would lose its opportunity to acquire the most realistic Brazilian-designed main battle tank and effectively shut down any possibility of a future locally designed main battle tank for decades to come, dooming Bernardini at the same time.

The Tamoyo 3 in its current state with a private collector. Source: Angelo Melliani

Designations

The Tamoyo had various designations to denote the stages of the project. The first stage of the Tamoyo was designated X-30, with the ‘X’ standing for prototype and the ‘30’ for its 30 tonnes weight. This designation was used until the first working prototype of the Tamoyo 1 was delivered in May 1984.

After the initial mock-up stage, the vehicle received a new designation: the MB-3 Tamoyo, named to honor the Tamoyo Confederation of the Tupinambá people. The Tamoyo Confederation was an alliance of various indigenous tribes of Brazil formed in response to the slavery and murder inflicted on the Tupinambá tribes by the Portuguese discoverers and colonizers. The Tupinambá people fought against the Portuguese from 1554 to 1575. A peace treaty between the two warring parties was signed in 1563, although the fighting did not completely end until 1567 after the Portuguese colonists were sufficiently strengthened to tip the scales in completely in their favor. The Tamoyo Confederation was effectively wiped out by 1575. Tamoyo means grandfather or ancestor in the Tupi language.

The MB-3 Tamoyo has 3 main sub-designations: Tamoyo I, Tamoyo II, and Tamoyo III (named Tamoyo 1, 2, and 3 in this article for ease of reading). The Tamoyo 1 refers to the Tamoyo meant for the Brazilian Army, armed with a 90 mm BR3 gun, DSI-14 500 hp engine, and a CD-500 transmission. The Tamoyo 2 was exactly the same as the Tamoyo 1, except that it used a modern HMPT-500 transmission. The Tamoyo 3 refers to the upgraded export version armed with a 105 mm L7, with an 8V-92TA 736 hp engine, a CD-850 transmission, and armored with composite armor instead of only steel. The Tamoyo 3 would eventually be proposed to the Brazilian Army as well in 1991, a year after the failure of the EE-T1 Osório.

The Tamoyo 2 would receive an additional designation in 1987. At some point, the Tamoyo 2 received the 105 mm turret of the then unfinished Tamoyo 3 for a military exposition. The sign next to the Tamoyo 2 called the vehicle the Tamoyo-II-105. In this article, it will be called Tamoyo 2-105 for ease of reading.

The 8 envisioned vehicles and the first prototype received individual designations as well. These designations went from P0 to P8 and had sub-designations regarding their models as well. The first working prototype was designated P0 and held the model designation TI-1, where ‘TI’ refers to Tamoyo 1 and the ‘1’ refers to the first Tamoyo 1 vehicle. There were also three support vehicles envisioned: bulldozer, bridgelayer, and engineering vehicle. These are denoted by VBE (Viatura Blindada Especial, English: Special Armored Vehicle)

Prototype Model designation
P0 TI-1
P1 TI-2
P2 TII
P3 TI-3
P4 TIII
P5 TI-4
P6 VBE Bulldozer
P7 VBE Bridge Layer
P8 VBE Engineering

Origin

The Tamoyo 3 program finds its roots from the previously developed 90 mm armed Tamoyo 1 and Tamoyo 2 projects meant for the Brazilian Army. At the time of these two projects, around 1984, the Brazilian Army sought a tank to counter the Argentinian TAMs, but at an affordable price as well. Initially, the concepts and requirements for the Tamoyo would have been quite similar to the Tamoyo 3 designed for export in 1987, but a lack of budget would temper these requirements into a more humble, albeit still capable vehicle.

The initial requirements laid out by the CTEx for the Tamoyo program were: a tank that weighed 30 tonnes (33 US tons, although this later seems to have increased to 36 tonnes (39.7 US tons) and was 3.2 meters (10.5 feet) wide for rail transport (same width as the Leopard 1), an operational range of around 500 km (310 miles), a ground pressure of roughly 0.7 kg/cm2 (10 lbs/in2), as high a percentage of locally-produced components as possible, and as much commonality of parts as possible with the M41 and the Charrua for logistical reasons. The Charrua was a locally designed tracked troop transport that was meant to replace the M113.

The Charrua. Source: Author’s collection

In addition, the vehicle had to use a conventional layout, with a 3 crew turret (there was no interest in autoloading systems). The national vehicle was to be armed with a 105 mm gun, while the export vehicle was to be armed with a 120 mm gun (that would become the Tamoyo 3), a stabilized gun, day/night sights, armor that should provide a high level of protection, diesel engines which gave the vehicles good power to weight ratios, and a fire extinguishing system.

Eventually, the requirements seem to have been reduced to a tank weighing 30 to 36 tonnes, 3.2 meters wide, an operational range of more than 500 km, a ground pressure of around 0.7 kg/cm2, parts commonality only with the M41 Walker Bulldog, and a national vehicle with a 90 mm gun. Overall, this was a more realistic vehicle for the Army’s budget, but their wish for parts-commonality with the M41 would eventually doom the Tamoyo 1 from its conception.

Bernardini recognized the disadvantages of the Tamoyo 1 and 2 tanks for the export market and decided to develop the Tamoyo 3 for export. In contrast to the Tamoyo 1 and 2 projects, where the Army seems to have provided a significant amount of funding, the Tamoyo 3 was Bernardini’s own endeavor and thus self-financed.

The Tamoyo 1. Source: Author’s collection

Concepts towards the Tamoyo 3

The development, or rather, the conception of the export Tamoyo seems to have run parallel to the Tamoyo development for the Army. Between 1979 and 1984, it seems that mainly the export Tamoyo concept designs were released, which were still designated X-30. The first of these was when the Tamoyo program resembled the Argentinian TAM. A sketch and explanation of the concept was presented in the newspaper O Estado de São Paulo on May 27th 1979.

The X-30 TAM

Division General Argus Moreira initially requested a tank with a front-mounted engine and rear turret, like the TAM. The tank and the project were designated X-30. An article in O Estado de São Paulo on May 27th, 1979 practically presented an improved copy of the TAM, although some of the combined requirements seem to have been somewhat unrealistic when one considers the TAM specifications. The new Brazilian X-30 tank was presented as a 30-tonne tank, armed with a 120 mm cannon, telemetric laser finder, a range of 600 km (370 miles), armor up to 70 mm (2.75 inch), NBC system, fire-extinguishing systems, 4 crewmembers, dual controls, and heat-treated armor angled at 20º to 50º. It was also supposed to be able to mount Brazilian copies of the Roland Surface-to-Air Missile system, although Brazil would never manage to successfully copy the SAM system.

To put these specifications in perspective, the TAM weighed 30.5 tonnes (33.6 US tons), had a 105 mm cannon, 590 km (366 miles) operational range, armor up to 50 mm (2 inch), a crew of four, and armor angled from 32º to 75º. The amount of road wheels of the X-30 is also exactly the same as on the TAM, suggesting more or less equal dimensions as well. The interesting part is that the X-30 effectively promised a better gun and better armor, while weighing as much as the TAM.

This presentation of the X-30 seems more of a propaganda article with the technician who gave the information to the journalist sketching a very impressive and capable vehicle that the Brazilian Army would most likely not have been able to afford in the first place.

The X-30 with the TAM lay-out. Source: Bernardini MB-3 Tamoyo – Expedito Carlos Stephani Bastos

The actual design of the X-30 TAM concept appears in an undated video of Bernardini where a shot briefly shows the design. The design resembles the sketch from the newspaper with some changes. The smoke dischargers are located on the front of the turret, there is no structure on the sides of the turret for the commander and loader hatches, the vehicle has an extra structure on the top of the hull which can be seen by the lower placed driver sights, and the vehicle has 3 return rollers instead of 4. The armament shown in the design of Bernardini is unknown. The sketch does not yet take the engine placement into account, although this might have to do with the drawing not being finished. The construction of a steel mock-up that used the front-engine configuration was already underway, but would never be finalized. The TAM-inspired design was very short-lived, as Bernardini and the CTEx opted for a traditional layout in less than 6 months.

The X-30 TAM design as shown in the video from Bernardini. Source: https://youtu.be/7oaZfsQYSMk

The Traditional Layout X-30

The front-mounted engine design was discussed with Bernardini, considering weight balancing, armor distribution, and the moments of forces and inertia. In the end, Bernardini and the Army decided to go for a traditional layout with a rear-mounted engine. A contract between the Army and Bernardini was signed and the development of a mock-up and prototype was initiated. The switch to the traditional design happened at some point between May 1979 and January 1980.

A concept sketch of the traditional X-30 was presented in the first issue of Jane’s 1980 International Defence Review. A description of the concept was given as well, stating that the drawing shows Bernardini’s project for a 30 tonnes medium tank, designated X-30, which was currently in the definition phase. It would have a Diesel engine of 520 to 745 kW (700 to 1,000 hp), an automatic transmission, have a range of 500 km (310 miles), and a ground pressure of about 0.7 kg/cm2 (10 lbs/in2). The last two specifications were based on the Brazilian Army’s requirements. According to the Brazilian correspondent, it was to be armed with either a 105 mm or 120 mm gun, although the current concept showed a Cockerill 90 mm gun. In addition, it was stated that the first prototype was estimated to be ready for trials in two years.

The concept sketch presented in Jane’s IDR. Source: Jane’s 1980 International Defence Review

This concept is estimated to be the first concept for two reasons. The first is the date when this concept was released, January 1980, which means that this concept was made about 6 months after the first TAM-inspired concept. The second reason is that this concept is nothing more than a mash-up of two tanks previously designed by Bernardini.

Jane’s concept mixes an enlarged X1A2 turret with the hull of an M41B. The concept derives in two major ways from the two vehicles it is based on. The first is that the hull is longer, as it has 6 road wheels instead of 5 on the M41, and the second is that the main gun looks like a lengthened EC-90 gun of the X1A2 with an added bore evacuator. Another difference is the driver’s hatch, which does not correspond with either vehicle.

X1A2 during ramp tests at the PqRMM/2. Source: Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivatives

It seems that this concept was already based on the specifications of the export version of the Tamoyo, which was the Tamoyo 3. There are a few interesting statements though. The first is the engine power, which is denominated in kW instead of hp. This was probably some kind of mix-up between units, as 520-745 kW translates to 700-1,000 hp, considering the given specifications are very close to the horsepower values which Bernardini presented for the DSI-14 and 8V-92TA engines.

The M41B, note the engine deck. Source: M-41 Walker Bulldog no Exército Brasileiro – Expedito Carlos Stephani Bastos

Overall, this concept seems to mainly suggest a potential export version of the X-30 instead of the X-30 for the Brazilian Army. This concept is potentially one of the first drawings of the X-30 in a traditional layout. The design itself is somewhat unimaginative, considering it is a mash-up of the X1A2 and the M41B, and the specifications are somewhat questionable as well.

An Artistic Interpretation

This concept was released in the press and abroad after the switch to the traditional layout. This concept dates back to at least April 1980, as the sketch is shown on the cover of the book Brasil Defesa – Os Blindados do Brasil. In this sketch, the X1A2 turret is a little bit altered, but uses a redesigned hull that resembles the final hull design much closer.

This concept retains a redesigned variant of the X1A2 turret, but the hull in this concept is different. The hull shares much fewer design features with the original M41 or the Brazilian M41B and M41C. The engine deck looks more like a main battle tank and resembles the Tamoyos which were built. The tracks of the concept do show a very clear resemblance with the M41 tracks. The gun on this concept is unknown, but it does seem to resemble a 105 mm gun, although this is pure speculation.

The artist’s rendition of the X-30. Source: Bernardini MB-3 Tamoyo – Expedito Carlos Stephani Bastos

Initial Component Selection

With the main development of the Tamoyo 1 and Tamoyo 2 completed by 1986, Bernardini set out to develop their export vehicle. To develop the new vehicle, Bernardini looked towards the United States for inspiration, which was developing vehicles of a similar concept.

In the early 1980s, the United States started looking for a new light tank to replace the M551 Sheridan. This program was known as the XM-4, for which the Commando Stingray, Teledyne Continental Motors ASP, Food Machinery and Chemical Corporation CCVL, the Swedish IKV-91, and the later Food Machinery and Chemical Corporation Armored Gun System (later known as the M8) were proposed. A range of components used for the XM-4 tanks can be found in the Brazilian Tamoyo as well.

The Commando Stingray in Thai service. The Stingray was one of the proposals for the XM4 program. Source: https://armoredwarfareid.blogspot.com/2016/05/the-temple-guardian.html

The Bernardini Engineers were most likely inspired by the XM4 tanks, as they were said to have been present during trials and followed the project’s developments. It is hard to not notice the similarities between some of the XM4 specifications of the Stingray and the XM8 and the eventual Tamoyo 3 (the final stage of the Tamoyo program, which was initially designed with export in mind). Both programs would use a low recoil force 105 mm gun, a Detroit Diesel 8V-92TA engine, an HMPT-500-3 transmission, had the same speed, the same operational range, and the same ground pressure.

The first influences of the XM-4 program can be seen in the Tamoyo 2, which was, for all intents and purposes, a Tamoyo 1, but with a modern HMPT-500-3 transmission instead of the old CD-500 transmission. The HMPT-500-3 transmission would also find its way into the Tamoyo 3 program as an optional component for Bernardini’s potential customers.

The HMPT-500-3 transmission at Bernardini. Source: Bernardini MB-3 tamoyo – Expedito Carlos Stephani Bastos

Bernardini decided to go for the Detroit Diesel 8V-92TA 736 hp engine and combine it with the CD-850-6A or HMPT-500-3 transmissions. The Detroit was said to have been able to receive an uprating towards 900 hp in the future, giving a potential hp to ton ratio of 29 instead of 23.75 (23 kW/t instead of 17.7 kW/t), but this was never implemented. The CD-850-6A was selected when General Motors was shutting down the CD-850 production, which would make obtaining licenses more viable for Bernardini. In addition, due to the extensive usage of the CD-850 in armored vehicle development, there was still a large market requiring spare parts for at least a couple of years. The CD-850 was effectively the flagship transmission of the Tamoyo 3 program.

Bernardini realized the inadequacy of the 90 mm F4 gun on the export market, and opted to arm the Tamoyo 3 with a 105 mm gun instead. Bernardini selected the Royal Ordnance 105 mm L7 LRF (Low Recoil Force) gun as the main armament of the export version. This gun finished development in late 1983 and could be mounted on vehicles such as the M41 Walker Bulldog, the Stingray, M47 Patton, and T-55s.

As the previously mentioned vehicles suggest, the 105 mm L7 LRF could be mounted on vehicles weighing around 20 tonnes. This was done by installing a muzzle brake, designed to allow the firing of APFSDS rounds (Armor Piercing Fin Stabilized Discarding Sabot) without damaging the sabot, and by facilitating a larger recoil stroke for the gun. This meant that, when the gun was fired, it recoiled up to 762 mm instead of the original 290 mm. The increased recoil length would have a few downsides, as the gun took up more space due to the recoil and the recoil could cause certain lighter and less wide vehicles to tip over when firing perpendicular to the hull and on a slope, as the center of mass would also shift. The last issue was not a problem for the Tamoyo 3 and it would not use a muzzle brake either.

The 105 mm L7 LRF on a test firing platform in the UK. Source: Jane’s Armour and Artillery 1985-86

The Tamoyo 3 Starts to Take Shape

With the main components of the Tamoyo 3 selected, the design of the tank could begin. The base hull design and suspension remained effectively the same with the Tamoyo 1, but from there, the vehicle got increasingly more advanced. The hull and turret were to be armored with composite and spaced armor, the 105 mm gun required a modern fire control system, modern fire prevention systems, NBC system, decreased thermal signature, and improved mobility.

Since the step from building effectively modernized post-World War 2 designs to designs that resemble 1970s technology is quite large, Bernardini hired two Israelis to consult them in new design concepts.

Israeli Influence

Bernadini visited Israel a number of times for consultation by General Israel ‘Talik’’ Tal, the mastermind of the Merkava tank. In addition, Bernardini also hired General Natke Nir (sometimes referred to as Natan Nir), who served as a colonel during the Yom Kippur War, for 6 months as a consultant for the design of armored vehicles. Natke Nir is credited by Flavio Bernardini for introducing spaced and composite armor concepts, improved protection against explosions, ammunition compartmentalization, mine protection, and the employment of tanks in combat situations. Although these consultancies were mainly focused on the Tamoyo 3, it would not be surprising if some concepts were or would eventually be carried over to the Tamoyo 1 as well.

General Natke Nir, picture taken in 1979.
Source: The National Library of Israel

Overall, it seems that the role of General Natke Nir was mainly to introduce Bernardini in what were the design standards of the day, and to tell them which designs would work and which would not based on his own experience. A practical solution that was suggested by Natke Nir was the addition of a number of small plates welded to the side of gunner periscope depression. The plates were meant to prevent machine gun fire from bouncing into the gunner’s periscope.

The steel plates, suggested by General Natke Nir, to prevent machine gun fire from bouncing into the gunner’s periscope, which was located where the gap is in the picture. Source: Bernardini MB-3 Tamoyo – Expedito Carlos Stephani Bastos

Gathering Components

Besides somewhat lacking the know-how of modern tank building, Bernardini and Brazil as a whole also lacked local Brazilian companies able to provide such high-grade components. Like Engesa before it, Bernardini started partnerships with a number of companies to gather the needed components to build their Main Battle Tank.

Among these companies were American, British, Brazilian, and German companies. The Americans would supply Bernardini with the transmissions, engine, and sights. It is unclear if Bernardini ever acquired the license to produce the CD-850-6A transmission or if this was to be done when they managed to sell the vehicle. The British provided the gun, the computers for the fire control system, and fire safety equipment. Bernardini and other Brazilian companies would mainly work on the steel, construction, and the suspension of the vehicle, while the German companies delivered most of the remaining components of the fire control system.

Country Company Component(s)
Brazil Bernardini Hull, turret, suspension components, composite armor, electric turret, and elevation drives
Brazil Themag Engenharia Electric turret and elevation drives
Brazil Universidade de São Paulo Electric turret and elevation drives
Brazil Eletrometal Torsion bars
Brazil Usiminas Steel
Brazil Novatracão Tracks and suspension components
Brazil D.F. Vasconcellos Driver’s day sights and potentially all other day sights (unknown if they supplied the driver’s night vision sight)
Germany-Brazil Moog-AEG-Siemens do Brasil Stabilization and elevation systems
United Kingdom-Brazil Ferranti Computers do Brasil Computers and programming for the fire control system
France Unknown Switches and connectors
United Kingdom Royal Ordnance Nottingham 105 mm L7A3 Low Recoil Force
United Kingdom Graviner Turret fire protection system (potentially the entire system including the engine bay as well)
United Kingdom Rank Pullin (General Electric Company UK in 1988) Optional supplier of periscopes and laser range finder (potentially telescopes)
United Kingdom Lucas Aerospace Generator and regulator
United States Unknown Turret slewing bearing and telescopes (telescope potentially from Kollmorgen)
United States General Electric Company US HMPT-500-3 transmission (optional)
United States General Motors Allison CD-850-6A transmission
United States General Motors Detroit 8V-92TA 736 hp Diesel Engine
United States Kollmorgen Corporation Installed periscopes and laser range finder (potentially telescopes)
Unknown Expectronics Unknown

It is important to note, like the EE-18 Sucuri and most likely the EE-T1 Osório, that a significant number of these components were on loan. Loaning components was done to save development costs while attempting to sell the vehicle. The loaned components were the Ferranti fire control system computer, turret stabilization, slewing and elevation system from Moog-Aeg Siemens, components from Detroit Diesel Alison, the generator and regulator from Lucas Aerospace, the sights from Kollmorgen, and supposedly the Rank Pullin sights. Of these, the Ferranti computer was to be returned on November 21st 1991.

Composite Armor Development

A big step in the development of the Tamoyo program was the integration of composite and spaced armor in the design of the Tamoyo 3. An interesting fact is that the Tamoyo 3 is in fact the only vehicle of the two Brazilian Main Battle Tanks to integrate composite armor. Although the Osório was planned to mount composite armor, a number of sources state that it never received a composite armor package. Some sources only mention the hull, which could suggest that the turret might have received a composite package, but no Brazilian source specifically states that the composite armor was ever successfully integrated on the Osório. The third prototype, known as the EE-T1 P3, which was meant to be the production vehicle prototype for Saudi Arabia, was planned to have composite armor installed, but the vehicle was never finished due to Saudi Arabia buying the Abrams and Engesa’s subsequent bankruptcy.

This leaves the Tamoyo 3 as the only Brazilian vehicle which is said to use composite armor on both the turret and the hull, but it is important to note that the integration seems to not have a particularly neat finish. There is a possibility that the supposed composite armor is a weight simulator, but sourcing does state that composite armor was integrated and the lack of proper finish could come from inexperienced instead. Only analysis of the existing Tamoyo 3 could definitively prove the integration of composite armor. Considering sourcing states the composite armor was installed, the writer will assume the same.

The base steel hull of the Tamoyo vehicles was meant to protect it frontally from 30 mm autocannon fire and 14.7 AP from at least the sides. If the base armor was actually capable of this remains somewhat doubtful. The composite armor package is said to have a line of sight thickness of about 300 mm and was installed on the front of the vehicle. The composition and effectiveness of the composite package is unknown, as are the overall thickness and the shape. Currently, it is thought that the package was mounted on top of a standard Tamoyo 1 style hull.

An approximation of the composite package on the front hull based on a Tamoyo 3 sketch, it is unknown how the plate under the composite was shaped. Currently, it is thought that it would be similar to that of a base Tamoyo hull. Source: Tecnologia Militar Brasileira and Author

The Bernardini technicians went to the United Kingdom, France, Germany, and Israel to gain more knowledge on composite armor, among other things. The eventual composition resulted from extensive testing at Marambaia Proving Ground and in Bernardini’s laboratories. The eventual Tamoyo 3 used a mix of composite and spaced armor, with the exact locations of these two types being unknown, with both types potentially integrated at the same places. The armor is very generally described as a frontal armor that puts special emphasis on the use of high-quality alumina and boron ceramics, special resins, carbon fibers and non-ferrous materials which were enclosed by high hardness steel plates to offer protection against large-caliber shaped charges.

Testing of the composite armor package by Bernardini against an unknown HEAT round. Source: Bernardini MB-3 Tamoyo – Expedito Carlos Stephani Bastos

During the initial phases of development, Bernardini also considered explosive reactive armor, but discarded it, as the base steel hull plate was too thin (the base frontal hull plates were 40 mm thick). The engineers also considered placing fuel tanks in advantageous positions to act as armor and also studied the use of kevlar in plastics against fragmentation.

Tamoyo 3 is Built and Presented

When the construction of the Tamoyo 3 prototype began is unknown. It is said that construction began somewhere after the Tamoyo 2 was completed, which was in 1986. The turret was the first to be completed, as the Tamoyo 2 hull with the Tamoyo 3 turret, known as the Tamoyo 2-105, was presented at a military exhibition sometime before May 10th 1987.

The Tamoyo 2 with the 105 mm gun during a military exposition in 1987. Source: Bernardini MB-3 Tamoyo – Expedito Carlos Stephani Bastos

On May 10th, 1987, the Tamoyo 3 was presented at the Cavalry Festival in Rio Grande do Sul. The vehicle was shown to the Army Minister at the time, Leônidas Pires Gonçalves (1985-1990), and the commander of the Comando Militar do Sul (Southern Military Region), General de Exército (equivalent to a four-star General) Edison Boscacci Guedes, by Flávio Bernardini. Interestingly, the Tamoyo 3 had not yet received its hull composite armor upgrade package, which was added somewhere between 1987 and 1991. The Tamoyo 3 was not tested by the Army at the time and would only be tested 4 years later.

Tamoyo 3 at the Cavalry Festival in Rio Grande do Sul. Source: Bernardini MB-3 Tamoyo 3

Looking at the pictures of what is called Tamoyo 3 by sourcing, something strange can be noticed. The vehicle presented at the Cavalry Festival has the exact same camouflage pattern as the Tamoyo 2-105 and also shares the exact same exterior appearance of other components. Another strange detail is that the hull bears the CTEx logo, even though the Tamoyo 3 was developed by Bernardini without Army help or funding, but this might also have been used to recognize the Army support to get the Tamoyo program off the ground in the first place.

Tamoyo 3 frontal picture at the Cavalry Festival in Rio Grande do Sul. Source: Bernardini MB-3 Tamoyo 3

Better pictures of the side rear might help in determining the vehicle precisely, as the Tamoyo 2-105 and Tamoyo 3 have a few external differences, like a hatch on the side rear which is round on the Tamoyo 2, but an ellipse on the Tamoyo 3. In addition, the engine deck of the Tamoyo 2-105 seems to have a more angled inclination than the Tamoyo 3, but this might just as well be the angle of the pictures taken or the lens used.

Another Tamoyo 3 frontal picture at the Cavalry Festival in Rio Grande do Sul. Source: Bernardini MB-3 Tamoyo 3

It might be possible that the actual Tamoyo 3 was finished later, maybe even as late as after the 1988 trials of the Tamoyo 1, as the Tamoyo 3 was not trialed here. But the Tamoyo 2-105, which was built at the time, was not tested either during these trials, so this is not a substantial estimate.

What is remarkable, however, is that the Tamoyo 3 was never tested outside of Brazil, even though it was an export vehicle. What is even more remarkable is that, in 1988-1989, the perfect opportunity for the Tamoyo 3 to prove itself against similar competitors took place in Ecuador. Ecuador considered buying a new tank and subsequently tested the TAM, Stingray, and the SK-105. These were all tanks in the same weight or doctrinal category as the Tamoyo 3, but for some reason, the Tamoyo 3 was either not sent by Bernardini, was not invited, did not meet the base requirements, or was simply not ready yet to be tested in Ecuador. This could suggest that the Tamoyo 3 was not completely finished by 1988 and seems to have missed the opportunity to say the least. The TAM is said to have won these trials by a landslide, scoring 950 out of a 1,000 points, but, as so frequently with South American countries, the tests did not result in any acquisition.

In any case, certain exterior details do suggest that the composite armor was an add-on to an existing standard Tamoyo base hull. The Tamoyo 3 has two distinct welding lines in the front side of the hull, which are around the same positions, and an angled upper front plate going off to the side on the base hulls. The Tamoyo 3 side became a longer flat plate of which the frontal parts were turned into a stowage box. It is possible that the armor underneath was altered to provide better stowage space, but no pictures of the inside of these boxes have been made.

The welding marks on the side hull. Source: Angelo Melliani

The Tamoyo 3 in Detail

The Tamoyo 3 weighed approximately 29 tonnes unstowed and 31 tonnes combat loaded. It is unknown if this was with or without the composite hull armor package. The vehicle was 8.9 meters (29.2 feet) long including the gun, 3.29 meters (10.8 feet) wide, 2.35 meters (7.7 feet) tall up to the turret top, and 2.5 meters (8.2 feet) tall including the commander’s machine gun. The hull of the Tamoyo 3 was 6.48 meters (21.25 feet) long and was operated by a crew of four. This crew consisted of the commander (right side of the turret in the middle), gunner (in front of the commander), loader (left side of the turret in the middle), and the driver (front left of the hull). The turret had two hatches, one for the commander and gunner and one for the loader.

The Tamoyo 3 in its current condition. Source: Angelo Melliani

Hull

The base hull of the Tamoyo 3 consisted of a welded homogenous steel construction. With the help of Adriano Santiago Garcia, a Captain in the Brazilian Army, ex-company commander on the Brazilian Leopard 1s, and former instructor at the CIBld (Centro de Instrução de Blindados, Armor instruction center), who knew someone present at the CIBld, the writer has been able to uncover a sizable amount of the base armor thickness values of the Tamoyo 3 by measuring the plate thicknesses. The base armor is heavier than the M41 Walker Bulldog and was meant to stop 30 mm rounds from the front, and 14.5 mm on all sides.

Tamoyo 3 Base Hull Armor
Location Thickness Angle from vertical Effective thickness
Upper Front 40 mm (1.6 inch) 65º-70º 95-117 mm (3.75-4.6 inch)
Lower front 40 mm (1.6 inch) 45º 57 mm (2.25 inch)
Sides 19 mm (0.75 inch) 19 mm (0.75 inch)
Rear ? ?
Top 12.7 mm (0.5 inch) 90º 12.7 mm (0.5 inch)

As previously mentioned, the composite armor package was meant to provide a line of sight thickness of 300 mm (11.8 inches). This does not seem to account for the entire front hull, as the composite package is thought to have become thinner at the upper parts of the upper front hull plate. The make-up and effectiveness of the composite armor are unknown.

Front view of the Tamoyo 3, note the external storage options on top of the composite armor and the raised driver’s hatch. Source: Angelo Melliani

The Tamoyo 3 had a headlight on each side of the front hull, together with what seem to be black-out markers next to them. Both the composite and the non-composite vehicle offered mounting points for spare tracks on the upper front hull plate. The composite Tamoyo 3 offered extra mounting points for tools and also two stowage bins that extended from the front hull top towards the fenders at the same angle as the composite armor plate. Two rear view mirrors were installed, each on a fender. The Tamoyo 3 with composite also offered two fire extinguishers on the bottoms of the stowage bins, and a siren on the right side of the upper front hull plate. The driver’s hatch was located on the front left and had 3 sights, of which the center sight could be replaced with a night vision sight. In an interior picture, the left sight is seen to have been made by D.F. Vasconcellos, but it is unknown if the center night vision sight was also from D.F. Vasconcellos.

Driver’s station, note the D.F. Vasconcellos plate on the left of the picture. Source: Angelo Melliani

Before it received its composite armor, the sights protruded from the upper front hull plate, while on the composite armor version, the entire driver’s hatch was raised with a construction. The driver’s hatch incorporated a sight while two other sights were installed on this raised construction. The hatch was a rotating one on both vehicles and the driver also had access to a hull escape hatch on the tank floor, located under the driver’s seat. The driver’s seat was adjustable in both height and distance and could be folded over to reach the escape hatch.

The driver used an adjustable steering wheel to steer the vehicle and could select the gear in neutral, pivot neutral, low, high, and reverse. The accelerator pedal was located on the right side and the brake pedal on the left side. The Tamoyo 3 also featured a hand throttle for independent acceleration of the accelerator pedal. A fuel tank selector was located on the right side of the driver, which allowed for the selection of fuel tanks. A total of 24 rounds of 105 mm ammunition were stowed to the right of the driver.

The ammunition stowage next to the driver, capable of storing 24 105 mm rounds. Source: Bernardini MB-3 Tamoyo

The gun travel lock was located on the top rear side of the hull in the middle. The rear of the Tamoyo 3 had a rear light and a black-out light on either side and also an infantry phone box located on the right rear, under the rear lights. In addition to the towing hook, two brackets were installed on this plate and on the lower front plate as well.

Rear view of the Tamoyo 3. Source: Author’s collection

The hull side provided mounting points for the installation of side skirts, which consisted of 4 sets of skirts on each side. The early versions of the side skirts were made from steel, but would later incorporate materials like rubber and aramid fibers to improve the effectiveness against certain projectiles.

The Tamoyo 3 before restoration, note the 4 side skirts. Source: Bernardini MB-3 Tamoyo n

Mobility

The Tamoyo 3 was powered by the Detroit Diesel 8V92TA water-cooled diesel engine in a separate compartment. This engine produced 736 hp at 2,300 rpm and 2,615 Nm torque at 1,500 rpm, which gave the vehicle a power-to-weight ratio of 25.5 hp/ton empty and 23.7 hp/ton combat-loaded (18.9 kW/t and 17.7 kW/t respectively). It used a General Motors CD-850-6A transmission which had 2 forward and 1 reverse gears. The low gear had a gear ratio of 3.50:1, the high gear had a ratio of 1.26:1, and the reverse had a ratio of 4.90:1. The General Electric HMPT-500-3 transmission was offered as an alternative. The 8V92TA and CD-850 powerpack gave the Tamoyo 3 a top speed of 65 km/h (40 m/h) and could be removed in less than 40 minutes. It had a fuel capacity of 700 liters (185 gallons), with 300 liters (80 gallons) each for the fuel tanks on the left and the right side of the tank, and 100 liters (26.4 gallons) for the frontal tank. The tank had an operational range of about 500 km (310.7 miles) with a fuel consumption of about 0.75 km per liter (1.76 miles per gallon).

The Detroit Diesel 8V92TA engine. Source: Bernardini MB-3 Tamoyo

The Tamoyo 3 used a torsion bar suspension with 6 road wheels and 3 return rollers on each side. The tank had a drive sprocket on the rear side, which likely shared the same dimensions as that of the M41, as it used the same tracks and had the same amount of teeth. It also had an idler wheel on the front. It had 3 additional shock absorbers installed, with 2 mounted on the front two road wheels, and 1 on the last road wheel. The torsion bars were previously developed by Eletrometal and Bernardini for the M41B program. These torsion bars were made from 300M alloy steel, which was also used for the torsion bars of the M1 Abrams. The idler wheel was mounted on the front side of the vehicle, while the drive sprockets were installed in the rear.

The Tamoyo 3 used Brazilian copies of the T19E3 tracks produced by Novatraçao. The suspension was protected by a side skirt. The T19E3 tracks had a width of 530 mm (20.8 inch), and a ground contact length of 4.51 meters (14.8 feet). This gave the Tamoyo a ground pressure of 0.74 kg/cm2 (10 lbs/in2) and a trench crossing ability of 2.4 meters (7.9 feet). The tank had a ground clearance of 0.5 meters (1.6 feet) and could climb a 0.71 meters (2.3 feet) tall vertical slope. It could climb a slope of 31º, and be operated on a side slope of about 17ºs. The vehicle had a fording capability of 1.2 meters (4 feet) and could neutral steer as well.

The Tamoyo tracks. Source: GOLPE FINAL NO DESENVOLVIMENTO DE BLINDADOS NO BRASIL LEILÃO – TAMOYO III

The engine allowed operation up to 51º Celsius without limiting the vehicle’s engine performance. The exhaust could have been mounted externally if requested, but would normally come out of the rear grills where it was used with cooling air to reduce the thermal signature. To better facilitate wading, an engine air intake could be used, passing through the turret or externally. A bilge pump was used to pump away any excess water.

Turret

The Tamoyo 1’s turret was armored with welded homogeneous steel plates presented at various inclinations and supposedly integrated a combination of composite and spaced armor. Where exactly the composite armor was placed is unknown. It is at least clear that either composite or spaced armor was used on the middle and front sides, as a weldline appears next to the commander’s cupola, which on the interior shows a plate bending towards the inside, suggesting a cavity. The exact armor thicknesses of the Tamoyo 3 turret are yet unknown, but could be acquired by measurements of the preserved vehicle at some point in the future.

The Tamoyo 3 turret, note the weld lines circled in red, suggesting there might be a cavity there combined with the plate on the interior bending inward. Source: Bernardini MB-3 Tamoyo

The turret that was mounted on the Tamoyo 3 was not meant to be the final turret. It had a very blocky look, almost akin to that of the Leopard 2A4 for example, resulting from Bernardini’s inexperience with composite materials. It is said that the final design would have been more ergonomic, although how this turret would eventually have looked remains a mystery.

Note the fairly blocky look of the Tamoyo 3 turret. Source: Angelo Melliani

The Tamoyo 3 had a turret ring of 2 m (6.6 feet), which was the same as the Tamoyo 1 and 2. The turret had 2 hatches, one for the commander and gunner, and one for the loader, which were located on the turret top on either side. The commander was located on the middle right of the turret, with the gunner in front of him, while the loader was located on the middle left of the turret.

The gunner had access to a periscope, which was located on the front right of the turret, and an emergency coaxial telescope for the 105 mm gun. The commander had access to 7 periscopes, of which at least one was the same as the gunner’s periscope for independent target acquisition. The loader also had access to a periscope.

The Gunner’s Kollmorgen periscope. Source: Bernardini MB-3 Tamoyo

External features of the Tamoyo 3 turret included a bolted-on turret top plate to facilitate the removal of the gun. On the front left, there seems to have been a cover for a potential mounting point of a meteorological station to measure temperature, wind speed and direction. The loader’s periscope was located behind the meteorological station, in front of the loader’s hatch. The gunner’s periscope was located on the front right in a dedicated depression of the turret.

The front top of the Tamoyo 3 turret. Source: Bernardini MB-3 Tamoyo

The commander’s station was located behind the gunner’s periscope and offered a rollable rail-mounting point for a machine gun. An unknown component was located between the loader and commander’s hatches. This might be an additional mounting point for a machine gun. The antenna’s were located behind the loader’s hatch to the left side and all the way to the rear right. A visible blow-out panel is seen on the rear left as well, with the ventilation and NBC (Nuclear, Biological, Chemical) system ventilation cover in the middle rear of the turret. A large stowage bin was mounted on the rear as well.

The rear top of the turret, note the blow-out panel left and the ventilation cover right. Source: Bernardini MB-3 Tamoyo

The turret had a number of lifting hooks spread out over the front and sides (6 in total) and also offered 3 handles to enable the crew to climb on the turret. A set of 4 smoke dischargers was installed on each side of the turret rear.

The coaxial machine gun was located on the left side of the 105 mm gun and could be fired by the gunner and commander stations and manually by the loader. The loader had access to 6 boxes of 7.62 mm ammunition in a stowage to the left, mounted on the top plate. An additional 10 boxes of 7.62 mm or .50 ammunition were stored on what seems to be on the floor of the turret basket, resulting in a total of 4,000 rounds of 7.62 mm ammunition.

The Tamoyo 3 had two types of ammunition stowage for the 105 mm gun. It had a rear stowage located in a blast-proof compartment, with an access door on the left rear of the turret and a blow-out panel on the top, which offered room for 12 rounds. The other type was a 6 round ready-to-use vertical stowage location on the turret basket. These stowages were open and did not protect the crew in case of an ammunition ‘cook-off’.

The rear turret stowage. Source: Bernardini MB-3 Tamoyo

Most of the control panels and fire control system computers and panels were located at both the gunner and commander’s stations. The outer turret basket and the area around the recoiling gun were covered as much as possible with steel mesh to prevent the turret monster from claiming its fair share of tribute from the crew.

Armament

The Tamoyo 3 was armed with a Royal Ordnance 105 mm L7 LRF (Low Recoil Force) gun packed in a thermal sleeve (the thermal sleeve was not mounted when it was presented in 1987). This gun was developed after late 1982 and would arm the Cadillac Gage Stingray, among others. By mid-1984, two prototypes were completed. The gun used a longer recoil stroke and could also use a muzzle brake to lessen the recoil forces of the gun. The Tamoyo 3 would not use the muzzle brake. These low recoil guns could be mounted on light vehicles such as the M41, but also on the T-55 and M47 Patton.

The breech of the 105 mm L7 LRF gun. Source: Bernardini MB-3 Tamoyo

The gun had an overall length of 6.8 meters and had a recoil stroke of 762 mm. It weighed 1,932 kg and had a recoil pull on the trunnions of 113.75 kN. The 105 mm cannon could fire every round developed for the L7, which makes it a bit challenging to determine which rounds would be used on the vehicle. This would vary from customer to customer, so the decision was made to use the ammunition presented in the source material and the 105 mm ammunition used by the Brazilian Army today.

Tamoyo 3 Ammunition
Round Capability Effective range Velocity Weight
L64 APFSDS (armor piercing fin stabilized discarding sabot) 170 mm at 60º from vertical at 2,000 meters. 2,500 meters
(2734 yards)
1,490 m/s 3.59 kg dart (Tungsten, 28 mm diameter)
APDS L52 (Armor Piercing Discarding Sabot)* 240 mm flat from vertical at 2,000 meters.
210 mm at 30º from vertical at 2,000 meters.
120 mm at 60º from vertical at 2,000 meters.
2,500 meters
(2,734 yards)
1,426 m/s 4.65 kg sub-projectile/6.48 kg projectile
HEAT M456 (High Explosive Anti Tank) 360 mm (13.8 inch) at 30º at any range. 2,500 meters (2734 yards) 1,174 m/s 10.25 kg (8 lbs) projectile
L35 HESH (High Explosive Squash Head)* A multipurpose round for both anti-armor and anti-personnel purposes. Also used as High Explosive. 732 m/s 11.26 kg (11.6 lbs) projectile
White Phosphorus – Smoke Smoke round 260 m/s 19.6 kg (11.9 lbs)

* Those with an asterisk denote the ones used by the Brazilian Army

The turret had an electric elevation and traverse system and offered a gun elevation of 15º and a gun depression of -6º. It had a maximum elevation speed of 266 mils/s or about 15º per second and a maximum traverse speed of 622 mils/s per about 35º per second. It was further armed with a coaxial and turret top 7.62 FN MAG machine gun, although the coaxial machine gun could be replaced with a .50 as an option. The Tamoyo 3 stored 42 rounds of 105 mm ammunition and at least 4,000 rounds of 7.62 ammunition. A searchlight was installed coaxial to the gun.

The 105 mm gun with a thermal sleeve. Source: Angelo Melliani

Fire Control System

The Fire Control System (FCS) is one of the main components which set the Tamoyo 3 apart from its predecessors when it comes to how modern the vehicle was. However, it is somewhat hard to determine how good the fire control system actually was, as a Bernardini transcript mentions that the option of fire on the move was still to be implemented. It is not clear if this option was ever finalized by the end of the project. Most of the data presented here comes from the description of this transcript and a table on the FCS system which appear in the book Bernardini MB-3 Tamoyo by Expedito Carlos Stephani Bastos and from Ed Francis from Armoured Archives.

The Tamoyo 3 used a Ferranti Falcon computer system as the brains of the FCS and used Kollmorgen sights and Moog-AEG components for its stabilization. The Ferranti Falcon FCS was considered in the British Chimera project in 1984 alongside the Marconi IFCS (used on the later Chieftains and the Challenger 1), DFCS, AFCS SFCS 600, EFCS 600, MFCS and the Belgian OIP LRS5. What is interesting is that the Ferranti Falcon was the cheapest of the FCS systems coming in at £25,000, apart from the MFCS which was based on the EFCS 600 and cost £15,000. Interestingly, the calculation error of the Ferranti Falcon was 0.2 mils (so +- 0.2 meters inaccuracy per kilometer) while the MFCS had an error of 0.1 mils. So not only was the Ferranti Falcon worse than the cheapest option of Marconi, it was also more expensive.

The base version of the Tamoyo 3 used second-generation image intensifier tubes for both the Commander and Gunner as day-night vision for their main periscopes. Depending on the need, the image intensifier could be upgraded to a third-generation providing a more sensitive tube due to the application of gallium-arsenide in the photocathode, enabling the sight to operate at much larger distances. Second-generation image intensifiers were first developed in the late-1960s, while the third-generation image intensifiers were first developed in the mid-1970s and started entering production in the 1980s. On request, the sights could also be used with thermal imaging instead. The main difference is that image intensifier tubes need some light to function while thermal imaging does not.

Gunner station:
1 – panoramic view window; 2 – gunner periscope control panel; 3 – main FCS laser rangefinder; 4 – ballistics reticle gunner sight; 5 – day / night switch; 6 – auxiliary gunnery system; 7 – elevation and rotation control; 8 – 10 5mm cannon trigger switch; 9 – coaxial machine gun trigger switch; 10 – on/off FCS computer switch. Source: Bernardini MB-3 Tamoyo

The FCS periscopes used on the base Tamoyo 3 were M220 periscopes from Koolmorgen, which were also used on vehicles of the American XM4 light tank program at the time. On request, the periscope could use image intensifier tubes or thermal imaging. The vehicle was also offered with the M20 periscope with image intensifier tubes or any other periscope the customer might have wanted instead. The M220 periscopes gave the commander and gunner an amplification of 8 times for both day and night vision. The sights had an 8º and 7º field of view for day and night respectively and a lens diameter of 6 mm. The deviation of the parallel image on the sight display was 0.15 mils at maximum (10 km, meaning +-0.15 meter inaccuracy at 10 km).

The Ferranti Falcon FCS on the Tamoyo 3 worked between 400 and 9,995 m (437 to 10,930 yards) and was a 2-axis stabilized system. That the FCS only started working beyond 400 m is very strange and seems to have something to do with the Laser Range Finders (LRF) of the time in general, which in turn also mostly function between 400 and 9,995 meters. The LRF had an inaccuracy of 0.45 mils, which meant that, at a range of 2 km, the accuracy can be about +- 0.9 meters or +- 4.5 meters at 10 km. The receiver, however, had an inaccuracy of 0.56 mils, which would result in an inaccuracy of +- 5.6 meters at 10 km.

The electric turret drive. Source: Bernardini MB-3 Tamoyo

The table also gives a mils error value for when the Tamoyo 3 tried to fire on the move. Note that this function was supposedly not yet finished according to the transcript of Bernardini. It is thus unclear if this number is accurate for the actual end product. According to the table, the FCS had an error of 1 mils while firing on the move at a speed of 20 km/h (12.5 m/h). When this is compared to a table in Technology of Tanks by Richard Ogorkiewicz, this means that the Tamoyo 3 stabilization and FCS would have been equivalent to that of a basic stabilizer of the 1960s.

Table from Richard Ogorkiewicz. Source: Technology of Tanks

As previously stated, both the commander and gunner had the same sights and both could fire the gun. They could search for targets at the same time and lay and fire the gun. It is unclear if the commander could also program his target in the system so that the gun would automatically lay on target at the push of a button when he overrode the gunner. In case the periscopes could not be used, the gunner had access to a coaxial telescope with 7x magnification.

The FCS system took the following variables into account: weather, type of ammunition, temperature of ammunition, tilt of the gun, turret angle, gun firing, range. The Tamoyo 3 was fitted with a selector for 5 different types of ammunition, but could be expanded on request.

The loader’s side of the turret with the ammunition selector on the left. Source: Tecnologia Militar Brasileiro

In the end, the effectiveness of the Tamoyo 3 FCS is somewhat uncertain. While standing still, it was a decent fire control system but had the interesting quirk of a not functioning LRF within 400 m, and firing on the move seems to have never been fully worked out. In the case firing on the move was properly implemented, it remains uncertain if it would still have had 1 mils of inaccuracy. In any case, based on the data available on the FCS, it was probably not a very good FCS during the 1980s and would have been more akin to FCS systems from the 1960s or 1970s.

Fire Protection System

One of the main systems marketed by Bernardini was its fire protection system. Although not much more special than what was in common use on other tanks of the time, it did represent one of the larger advancements for the company in crew safety, apart from the much-improved armor technology.

The fire protection system was designed and delivered by Graviner and offered 4 suppressors, of which 2 were installed in the engine bay and 2 in the turret. All 4 suppressors used HALON 1301 as extinguishing gas, which could be used in crew-operated spaces without risk to life. The suppressors in the engine bay contained 3 kg (6.6 pounds) of HALON, while the amount of the turret suppressors is unknown. The Tamoyo 3 would be sold with 2 external spare CO2 fire suppressors of 2 kg (4.4 pounds) each.

Tamoyo 3 interior, note the two fire extinguishers in the turret. Source: Bernardini MB-3 Tamoyo

The engine bay was protected independently from the crew compartment, which was controlled by the driver. The system could be activated manually or automatically depending on the setting the driver used, with the manual activation being done through an emergency switch which was protected to prevent accidental activation. Detection was done through a system that monitored the capacitance and resistance between the wire and insulation through temperature increase. A drop in resistance and rise of capacitance of the insulation sent off a warning signal or automatically activated the system. The fire detectors formed a protective mesh around the powerpack to better protect the engine from fires.

The turret fire protection system consisted of a control panel, 2 suppressors, and 4 infrared detectors. The infrared detectors could quickly pick up significant rises in temperature and send a signal for the fire protection system to start suppressing the fire. The system could be used in 3 settings: peace, war, and off. In peace mode, 2 detectors had to signal the presence of a flame before sending a signal which would first initiate one of the suppressors and after 5 seconds it would initiate the second suppressor if needed. The system only needed one detector to activate in war mode to discharge both suppressors. The fire protection system could be tested when it was turned off from the electrical system. Both suppressors were located on the loader’s side.

The loader’s side of the turret with the turret fire extinguishers. Source: Tecnologia Militar Brasileiro

Other Systems

Power to the electrics was provided by two 105 Amp 28 Volt Alternators next to the powerpack. These alternators could be accessed from the crew compartment through a special hatch. A single 500 Amp alternator could be chosen as an option. The Tamoyo carried 4 batteries connected in series-parallel to also provide power to the tank when the main engine was turned off, allowing the vehicle to still use the rest of its systems in a potentially limited capacity. To better protect against short-circuits, 2 main relays could be selected by the driver. As an optional component, 4 NATO standard TN-12-100 Batteries could be supplied. These are 12 volt batteries, each with 100 Ah, which could be interchanged with a large number of vehicles. The batteries could be accessed through the engine bay hull top hatch.

The Tamoyo 3’s radio system consisted of a KX16A power circuit breaker, an AK20 high-frequency distributor, a KO19 repeater box, a KO20 secondary controller for each crew member in the turret, two antennas on the turret top, and an AV-3 amplifier. The vehicle could receive any radio systems, such as the EB 11-204D, AN/PRC-84 GY, and AN/PRC-88 GY from any manufacturer. The radio was located in the turret rear and could be operated by both the commander and loader. The radio also included a mobile station for the crew to take with them when they had to exit the vehicle and intercoms for exchange of commands with the crew. The Tamoyo 3 also offered an external telephone on the rear of the vehicle for infantry and support units to communicate with the tank crew.

A number of other features were offered for the Tamoyo 3. These included a heater and an NBC system (Nuclear, Biological and Chemical filter). The heater would have been an independent system from the powerpack, although it is unknown how it would exactly have been implemented. The NBC system would include the addition of special seals on the hatches, turret ring and so on to seal the vehicle. The system would have a selector for the filter.

Engesa Enters the Fray

In 1982, Engesa broke the gentlemen’s agreement on which the Brazilian armored vehicle industry was founded. Engesa, which was supposed to focus exclusively on the development of wheeled armored vehicles, initiated the development of the EE-T1 Osório. Although the Osório was not directly developed for the Brazilian Army, Engesa still decided to use some of the initial requirements laid out by the Brazilian Army so that they could sell it to Brazil as well, but with a 105 mm gun instead. Engesa decided to increase the weight to make it more capable on the export market, but retain the 3.2 meter (10.5 feet) width.

The EE-T1 P2 Osório meant for Saudi Arabia, photo taken at the Marambaia proving grounds in Rio de Janeiro. Source: Author’s collection

The tank Engesa ended up with was a vehicle that outperformed the Tamoyo 1 in every aspect, except price. The Osório would outperform the later Tamoyo 3 as well in multiple aspects. In 1986, the Osório with 105 mm gun was trialed by the Brazilian Army. The Osório impressed the Brazilian Army so much that they practically seemed to have forgotten about their initial requirements of interchangeability. The Brazilian Government supposedly promised Engesa that they would buy 70 Osórios, but this would later increase to 150 or 300 Osórios according to sources. This decision effectively meant that the Army forwent the Tamoyo project which they had initiated, which was tailor-made to Brazilian requirements, and decided to go with the Osório.

The Overall Tamoyo Program and the Army

The fate of the Tamoyo 3 is somewhat tied to the earlier Tamoyo 1 and the appearance of the Osório. The now finished prototypes of the Tamoyo 1 were trialed by the Brazilian Army in 1988. Considering various Tamoyos, like the Tamoyo 2 and 3, were already finished around 1986-1987, this date seems to be quite late. Flavio Bernardini noted in one of his memoirs that the Tamoyo program was ‘’Empurrada com a barriga” (Eng: Put under the belly) by the Army, which is a saying suggesting that the Army seems to have somewhat deliberately postponed the trials.

The Tamoyo during tests. Source: Author’s collection

The second Tamoyo 1 (TI-2) was trialed by the Army in 1988, and subsequently rejected. The TI-2 was not fast enough and its acceleration was lacking as well. In addition, the oil filter was damaged and the gearbox was damaged due to cracking near the fixation points of the spur gears.

The Tamoyo driving up a ramp. Source: Author’s collection

This rejection presented a few major issues. The first was that neither the Tamoyo 1 nor the Tamoyo 2 could match the new requirements by the Army in their current configuration. Bernardini considered converting the Tamoyo 1 (TI-3) to a potential Tamoyo IV (4) version. The Tamoyo 4 would have used an MWM engine and ZF gearbox for its powerpack. This was viable since both MWM and ZF had sizable subsidiaries in Brazil at the time. The construction of a Tamoyo IV was never carried out.

The Tamoyo 3 “Under Consideration’’

What happened after the failed Tamoyo 1 trials seems to be one of the stranger affairs in tank acquisition projects of the Brazilian Army. By 1988, the Tamoyo 3 was said to have been completed, but for some reason, the Brazilian Army did not test the vehicle. In fact, the Brazilian Army would not officially test the Tamoyo 3 even once, seemingly obsessed with the Osório to such a degree that it would not consider the Tamoyo 3 until after the Osório program had definitely failed.

In 1991, the Tamoyo 3 was finally considered by the Army. The Tamoyo 3 would also face a brick wall, as the Army staff was split regarding it. One side was in favor of the Army sharing the costs of the evaluation of the Tamoyo 3, while the other side wanted to terminate the entire Tamoyo project and that the costs of the evaluation fall solely on Bernardini.

This was because the Tamoyo 3 was classified as a foreign vehicle instead of an indigenous design, since it used a lot of components that were not yet used in the Brazilian Army. These components included the L7 cannon, automatic fire extinguishing sensors, and the fire control system, among other components. The Army definitively canceled the entire Tamoyo project on July 24th 1991 without testing the Tamoyo 3 even once. With this decision, Brazil effectively shut down any possibility of an indigenous designed and manufactured main battle tank for the Army.

In a way, the Osório trials seem to have sent a signal to the Army that heavier main battle tanks, armed with guns over 90 mm, were the way forward. But this was the case for the Tamoyo 1 and not for the Tamoyo 3. Even worse, the Tamoyo 3 was only considered as late as 1991, a year after the Osório project failed and a year after Engesa filed for bankruptcy. This only further solidifies the notion that the Army decided it wanted the Osório from Engesa and not the Tamoyo 1 or the Tamoyo 3 from Bernardini.

The subsequent rejection and classification of the Tamoyo 3 as foreign seems to be hypocritical, as the Tamoyo 3 was effectively more national than the Osório. While both vehicles had almost no components that were interchangeable with other Army vehicles or components of the time, the Tamoyo 3 at least retained its suspension system, which would make it interchangeable with the M41C. This foreign marking of the Tamoyo 3 thus seems strange, as the Osório did not receive such treatment.

The reason for this hypocritical stance of the Army might have had to do with exterior factors, however. Brazil underwent a political shift in 1985. The country transitioned from a military dictatorship towards a democracy again. With this shift, the newly reformed democracy found itself in a 10-year-long battle against hyperinflation and economic disaster. To give an idea of the inflation which the democracy inherited from the military dictatorship, inflation rose to 658.91% between March 1984 and December 1985. The Brazilian economy would only start to recover from the rampant inflation around 1994. As a result of this crisis, the Brazilian government practically cut any acquisition of new material for the Brazilian Army. It is possible that the Brazilian Army would not have been able to afford the Osório initially either if it had been a success during the early 1990s and would only acquire it much later on, when the economy settled down and Engesa would have been well on its way to the Saudi Arabia order.

The cost of the entire Tamoyo 3 project is summarized in the table below, coming in at US$4.39 million in 1991. In comparison, the EE-T1 Osório project is estimated to have cost between US$50 to 100 million. The actual cost would likely be higher in theory, as design and engineering of the previous Tamoyo 1 and 2 projects should be considered as well. It is very likely that, as more components would be manufactured in Brazil, if the Tamoyo 3 was bought, the costs would have come down further due to serial production and not needing to import components. The 105 mm L7 could be made in Brazil, but Bernardini would need to acquire a machine for autofrettage, a form of cold working technique to strengthen the barrel interior so it can handle higher pressures.

Component US$ 1991 US$ 2021
105 mm L7 LRF 50,000 100,000
Turret bearing 40,000 80,000
Suspension 300,000 600,000
Final driver 100,000 200,000
Plates and profiles 200,000 400,000
Consultancy 100,000 200,000
Project engineering 2,300,000 4,600,000
Man hours 1,000,000 2,000,000
Ammunition 200,000 400,000
Total 4,390,000 8,780,000

Impact

Even worse is that the decision to close down the Tamoyo project seems to have sealed Bernardini’s fate as well, as the company closed its doors in 2001. If the Army had decided to acquire the Tamoyo tank, whether it would have been the Tamoyo 1, 2, 3, or 4, Bernardini would probably have lived on. The acquisition of the Tamoyo would mean much more than just buying the tanks. Maintenance support, supply of spare parts, further development and upgrade programs, and more nationally produced components would all give Bernardini a steady flow of income. More importantly, Bernardini’s survival and further development of the Tamoyo would have meant that the knowledge on designing tanks and all the advancements made in the field would have been retained in Brazil.

The Tamoyo 3 especially showed a lot of potential in this regard. Although the FCS system is what held back the Tamoyo 3 the most, it is unknown what the FCS would have looked like if it was finalized. In addition, the FCS could be modernized at a later point as well by Bernardini if the Army wanted. The turret would also likely have been redesigned to provide more ergonomic protection as well. Also, taking into account the promises of a 900 hp engine or a potential refit with a ZF transmission and an MWM engine of the Tamoyo 4 program, these would have brought the Tamoyo 3 a significant mobility upgrade as well. In any case, an acquisition of the Tamoyo 3 would have left the Brazilian Army with a promising and capable main battle tank and retain the company and the know-how to potentially build future tanks.

The seeming inability to buy the Tamoyo 3, or the Osório for that matter, is usually seen as a strategic mistake by the Brazilian Army and politics. It robbed the country of the most capable land-based system companies, on which it had spent two decades to reach their apex of building their own tanks. The failure of saving either Bernardini or Engesa has caused Brazil to be dependent on foreign designs and supplies yet again.

The Tamoyo 3 Story Continues

The Tamoyo 3 story did not end here, however. With the cancellation of the Tamoyo project, a large number of components were to be returned to their respective owners, as Bernardini had borrowed them until a sale of the Tamoyo 3 would be made. These included, among other components, the Ferranti FCS, Kollmorgen sights, and the stabilization systems. The current Tamoyo 3 is thus effectively stripped of a number of important systems.

It seems that Bernardini first applied for bankruptcy in 1995 and that the Tamoyo 3 was acquired by a company Brasrodas and ended up in a judicial auction. It was then bought by a private collector and was again auctioned with a starting bid of 125,000 Brazilian Real on February 2nd 2007. The Army then blocked the sale, as the vehicle was still in the Ipiranga factory and would need to move. It was stated in a number of reports that the current owner then considered donating it to the Army, which seemingly never happened. The tank was later put up for sale again for 250.000 Brazilian Real. It is unclear what happened after the sale.

The Tamoyo 3 in Ipiranga factory in 2007. Source: Bernardini MB-3 Tamoyo

What is known is that pictures of the Tamoyo 3 resurfaced on May 21st 2018. A restored Tamoyo 3 is shown and is supposedly in driving condition as well. The exact location and owner are unknown, although it is thought to be in Jundiaí in São Paulo state. Contact with organizations and the photographer have been attempted, but this did not yield many results. An issue with this is that the Tamoyo 3 is not open for public viewing, as it is part of a private collection. The flip side is that it would not have been better off in Army hands, as they do not treat their vehicles particularly well in the Conde de Linhares Tank Museum. In any case, the Tamoyo 3 is in good hands and has been particularly well cared for.

The Tamoyo 3 in its current condition. Source: Angelo Melliani

The writer would like to use this part to call out to any person who might know more about this specific Tamoyo 3 and its owner to get in contact with Tanks Encyclopedia so that a better account of the Tamoyo 3 with more detailed pictures and estimates like armor can be made.

Conclusion

The Tamoyo 3 was the apex of the Tamoyo program and can be seen as a true Main Battle Tank in South America. Its composite armor, modern FCS for Brazilian standards, and crew protection were only rivaled by the more expensive and export-focused Osório from Engesa in Brazil. Sadly, the Brazilian Army seems to have been fully captivated by the Osório at the time, and only remembered that they had another promising tank when the Osório failed in 1991.

The fact that the Brazilian Army never tested it even once, but also that it was never tested in, for example, Ecuador, shows that the Brazilian Army had no real interest in the Tamoyo project as a whole anymore, but also that Bernardini was seemingly not in the position to carry out the project by itself. The treatment of the Tamoyo 3 as a foreign vehicle seems hypocritical. Even though the initial goal of the Tamoyo program was for as much interchangeability as possible, this goal was what doomed the Tamoyo 1 and 2 from the start as underpowered vehicles. This argument should not have weighed as heavily, especially considering the love the Osório received.

The blame cannot be fully shifted on the Army, however. Brazil was in a significant financial crisis for years at that point and even an Osório acquisition at the time would have been doubtful if it had managed to secure the Saudi Arabia contract. The shift from military dictatorship to democracy did not make the situation better either when it came to the national defense companies. The subsequent end of the Cold War and flooding of dirt-cheap surplus equipment also prevented any potential Tamoyo revival from taking place when Brazil finally recovered in the mid-1990s. Brazil would, for example, acquire M60A3 TTS tanks for as little as US$165,000 a piece in 1996.

The Tamoyo 3 was a promising and most likely a more realistic vehicle for Brazil than the Osório. It might not have been a particularly impressive vehicle, but it would have fitted the Brazilian requirements and needs perfectly. A successful acquisition would have likely seen the Tamoyo 3 in service for as long as the Leopard 1A5BR would remain in service and would have saved Bernardini, and thus retained a tank building company with experience in the country. Instead, the Tamoyo 3 ended up like the Osório and is now what could have been instead of what is.

Tamoyo 3 when it was up for auction in the old Bernaedini factory, illustrated by Ardhya ‘Vesp’ Anargha, funded by our Patreon campaign.
Tamoyo 3 in its current state at the private collector, illustrated by Ardhya ‘Vesp’ Anargha, funded by our Patreon campaign.
Tamoyo 2-105 or potentially Tamoyo 3 when it was presented at the expo in 1987, illustrated by Ardhya ‘Vesp’ Anargha, funded by our Patreon campaign.
Specifications (MB-3 Tamoyo 3)
Dimensions (L-W-H) 6.48 m (21.3 feet) and 8.9 m (29.2 feet) with the gun pointing forward, 3.29 m (10.8 feet), 2.35 m (7.7 feet) to turret top and 2.5 m (8.2 feet) in total.
Total weight 29 tonnes empty, 31 tonnes combat-loaded (32 US tons, 34.2 US tons)
Crew 4 (commander, driver, gunner, and loader)
Propulsion Detroit Diesel 8V92TA 736 hp at 2,300 rpm
Suspension Torsion bar
Speed (road) 65 km/h (40 m/h)
Armament 105 mm L7 LRF
Coaxial 7.62 mm mg or .50 caliber MG HB M2
Anti-Air 7.62 mm mg
Armor Hull
Front (Upper Glacis) 40 mm at 65º-70º (1.6 inch) + around 300 mm composite and spaced armor
Front (Lower Glacis) 40 mm at 45º (1.6 inch) + potentially composite and spaced armor
Sides 19 mm at 0º (0.75 inch)
Rear ?
Top 12.7 mm at 90º
(0.5 inch)

Turret
Unknown Usage of steel, composite and spaced armor

Produced 1

Special thanks to Expedito Carlos Stephani Bastos, the leading expert of Brazilian armored vehicles https://ecsbdefesa.com.br/, Jose Antonio Valls, an Ex-Engesa employee and expert in Engesa vehicles, Paulo Bastos, another leading expert of Brazilian Armored vehicles and the author of the book on Brazilian Stuarts and the website https://tecnodefesa.com.br, Adriano Santiago Garcia, a Captain in the Brazilian Army and ex-company commander on the Leopard 1 and ex-lecturer on the Brazilian Armored School, and Guilherme Travassus Silva, a Brazilian with whom I was able to endlessly discuss Brazilian Vehicles and who was always willing to listen to my near endless ability to talk about them.

Sources

Blindados no Brasil – Expedito Carlos Stephani Bastos
Bernardini MB-3 Tamoyo – Expedito Carlos Stephani Bastos
M-41 Walker Bulldog no Exército Brasileiro – Expedito Carlos Stephani Bastos
M-113 no Brasil – Expedito Carlos Stephani Bastos
Jane’s armour and artillery 1985-86
Brazilian Stuart – M3, M3A1, X1, X1A2 and their derivatives – Hélio Higuchi, Paulo Roberto Bastos Jr., and Reginaldo Bacchi
L64 ammunition brochure
Moto-Peças brochure
Memoir of Flavio Bernardini
Angelo Melliani
Author’s collection
Tecnologia Militar Brasileira
Bernardini compra fábrica da Thyssen – O Globo, archived by Arquivo Ana Lagôa
The Centro de Instrução de Blindados

Personal correspondence
With Expedito Carlos Stephani Bastos, Expert on Brazilian armored vehicles
With Paulo Roberto Bastos Jr., Expert on Brazilian armored vehicles
With Adriano Santiago Garcia, a Brazilian Army captain and ex-company commander on the Leopard 1

Categories
Cold War Brazil MB-3 Tamoyo Cold War Brazilian Armor

MB-3 Tamoyo 2

Brazil (1986)
Medium Tank – 1 Built

With the initiation of the Tamoyo 1 project by Bernardini and the Brazilian Army in 1979, Brazil set off designing a new family of tanks for the country. The Tamoyo 1 was designed to have as many parts in common with the existing M41 Walker Bulldog fleet as possible. This meant that the Tamoyo 1 used a CD-500 transmission from the late 1940s/early 1950s and a 500 hp DSI-14 diesel engine. Effectively, the Tamoyo 1 was limited in its potential capabilities by the Army’s requests.

Sometime between 1979 and 1984, Bernardini decided that they wanted to offer the Tamoyo with a modern transmission as well. They secured the construction of a Tamoyo 2 in a contract with the Army, and installed a HMPT-500 transmission in the vehicle. In the end, the Tamoyo 2 would end up serving more as a testbed than anything else, and would be scrapped by the end of the Tamoyo program in 1991.

The Tamoyo 2 with the 105 mm gun during a military exposition in 1987. Source: Bernardini MB-3 tamoyo – Expedito Carlos Stephani Bastos

Designations

The Tamoyo had various designations to denote the stages of the project. The first stage of the Tamoyo was designated X-30, with the ‘X’ standing for prototype and the ‘30’ for its 30 tonnes weight. This designation was used until the first working prototype of the Tamoyo 1 was delivered in May 1984.

After the initial mock-up stage, the vehicle received a new designation: the MB-3 Tamoyo, named to honor the Tamoyo Confederation of the Tupinambá people. The Tamoyo Confederation was an alliance of various indigenous tribes of Brazil in response to the slavery and murder inflicted on the Tupinambá tribes by the Portuguese discoverers and colonizers. The Tupinambá people fought against the Portuguese from 1554 to 1575. A peace treaty between the two warring parties was signed in 1563, although the fighting did not completely end until in 1567, after the Portuguese colonists were sufficiently strengthened to tip the scales in completely in their favor. The Tamoyo Confederation was effectively wiped out by 1575. Tamoyo means grandfather or ancestor in the Tupi language.

A Tamoyo warrior, painted by Jean-Baptiste Debret. Source: https://artsandculture.google.com/asset/charruas-chief/jAFUsCu7mHJ5XQ?hl=fr&ms=%7B%22x%22%3A0.5%2C%22y%22%3A0.5%2C%22z%22%3A9.01566727112745%2C%22size%22%3A%7B%22width%22%3A3.954717967284%2C%22height%22%3A1.2374999999999998%7D%7D

The MB-3 Tamoyo has 3 main sub-designations: Tamoyo I, Tamoyo II, and Tamoyo III (named Tamoyo 1, 2, and 3 in this article for ease of reading). The Tamoyo 1 refers to the Tamoyo meant for the Brazilian Army, armed with a 90 mm BR3 gun, DSI-14 500 hp engine and a CD-500 transmission. The Tamoyo 2 was exactly the same as the Tamoyo 1, except that it used a modern HMPT-500 transmission. The Tamoyo 3 refers to the upgraded export version armed with a 105 mm L7, with an 8V-92TA 736 hp engine, a CD-850 transmission, and armored with composite armor instead of only steel. The Tamoyo 3 would eventually be proposed to the Brazilian Army as well in 1991, a year after the failure of the EE-T1 Osório.

The Tamoyo 2 would receive an additional designation in 1987. At some point, the Tamoyo 2 received the 105 mm turret of the then unfinished Tamoyo 3 for a military exposition. The sign next to the Tamoyo 2, calls the vehicle the Tamoyo-II-105. In this article, it will be called Tamoyo 2-105 for ease of reading.

The 8 envisioned vehicles and the first prototype received individual designations as well. These designations went from P0 to P8 and had sub-designations regarding their models as well. The first working prototype was designated P0 and held the model designation TI-1, where ‘TI’ refers to Tamoyo 1 and the ‘1’ refers to the first Tamoyo 1 vehicle. There were also three support vehicles envisioned: bulldozer, bridgelayer, and engineering vehicle. These are denoted by VBE (Viatura Blindada Especial, English: Special Armored Vehicle)

Prototype Model designation
P0 TI-1
P1 TI-2
P2 TII
P3 TI-3
P4 TIII
P5 TI-4
P6 VBE Bulldozer
P7 VBE Bridge Layer
P8 VBE Engineering

Origin

In 1979, the Brazilian Army released a set of requirements for a new national tank. The CTEx (Centro Tecnológico do Exército, English: Army Technology Centre), which Division General Argus Fagundes Ourique Moreira led, was responsible for the acquisition of funds from the Army for the project, and to give input in the selection of components, design, and companies working on the new tank. The CTEx effectively participated in this project to ensure that the Army would receive a feasible Carro de Combate Nacional Médio (National Medium Combat Car/tank, the Brazilian Army names all their tanks combat cars).

This project would be known under the designation X-30, with the ‘X’ standing for prototype and the ‘30’ for its 30 tonnes weight. One of the key requirements apart from weight and width, was a high level of interchangeability between components of the available Brazilian M41 Walker Bulldog fleet and the potential Charrua Armored Personnel Carrier from Moto-Peças, which was intended as an M113 replacement. The main components selected for this new tank were a CD-500 transmission, DSI-14 engine, a Brazilian version of the 90 mm F4 designated Can 90 mm 76/90M32 BR3, and a copied M41 suspension system. Of these main components, the transmission, engine and suspension were interchangeable with the upgraded M41B and M41C fleet of Brazil.

The X-30 mock-up. Source: Bernardini MB-3 Tamoyo – Expedito Carlos Stephani Bastos

The XM4 program

The main issue with the X-30 was the age of the CD-500 transmission. The CD-500 was already a 30 year old design by the time the development of the Tamoyo was initiated in 1979. Bernardini thus concluded that it was necessary to offer a modern transmission for the Tamoyo besides the CD-500. The company selected the HMPT 500-3 transmission, then used for the Bradley and the XM4 light tank project, among others, by the United States, and entered negotiations with General Electric.

In the early 1980s, the United States started looking for a new light tank to replace the M551 Sheridan. This program was known as the XM4, for which the Commando Stingray, Teledyne Continental Motors ASP, Food Machinery and Chemical Corporation CCVL, the Swedish IKV-91, and the later Food Machinery and Chemical Corporation Armored Gun System (later known as the M8) were proposed. A range of components used for the XM-4 tanks can be found in the Brazilian Tamoyo as well.

The Commando Stingray in Thai service. Source: https://armoredwarfareid.blogspot.com/2016/05/the-temple-guardian.html

The Bernardini Engineers were most likely inspired by the XM4 tanks, as they were said to have been present during trials and followed the project’s developments. It is hard to not notice the similarities between some of the XM4 specifications of the Stingray and the XM8 and the eventual Tamoyo 3 (the final stage of the Tamoyo program which was initially designed with export in mind). Both programs would use a low recoil force 105 mm gun, a Detroit Diesel 8V-92TA engine, an HMPT-500-3 transmission, had the same speed, the same operational range, and the same ground pressure.

The main difference was that the Tamoyo 3 was more heavily armored in both base armor configuration and with composite armor, causing the Tamoyo 3 to be about 10 tonnes heavier than the air-transportable XM4 projects. It is very likely that the Bernardini engineers followed the XM4 program while designing their own Tamoyo 3 for export, in an attempt to make it as interesting as possible for the export market and to design a proper main battle tank for South American standards. At the same time, it is also very likely that Bernardini came in closer contact with the HMPT-500-3 transmission through the XM4 program for the Tamoyo 2 as well.

The Tamoyo 2 Mock-Up?

According to Flavio Bernardini, at the time one of Bernardini’s CEOs, Bernardini also produced a mock-up of the Tamoyo 2. Although this is probably true, it does not make much sense. The only difference between the Tamoyo 1 and the Tamoyo 2 is the transmission of the vehicle. The rest of the design remained unchanged in the initial stages.

The Tamoyo 2 mock-up. Source: Bernardini MB-3 tamoyo – Expedito Carlos Stephani Bastos

Even more confusing, the picture of the mock-up is dated August 1983. In the picture, the lower hull is shown to be more or less completed, but the turret is a styrofoam mock-up. This styrofoam mock-up is almost exactly the same as the X-30 mock-up except for a few details, such as lifting eyes. In addition, the gun presented on the Tamoyo 2 mock-up is a dummy of the 76 mm from the M41. The rear side hull plate does look different from the eventual X-30 mock-up, as the rear part does not widen as gradually.

Another detail which makes this mock-up confusing is that the contract for the development of the Tamoyo 2 was signed in 1984 and not 1983. It is possible that Bernardini proposed this upgrade earlier on, which could explain the existence of the mock-up.

Finally, it is unknown what happened with the Tamoyo 2 mock-up. This makes it impossible to either fully prove or disprove that a Tamoyo 2 mock-up existed. For all we know, it was scrapped, or it was integrated with the current X-30 mock-up preserved at the CTEx.

The writer thus somewhat questions the existence of the Tamoyo 2 mock-up and suggests that it might just be the X-30 mock-up in early stages. This would not be unlikely, as the contract for the production of the Tamoyo prototypes between the Army and Bernardini was only signed in March 1984. The styrofoam turret suggests that, as of late 1983, no steel mock-up turret was available, and the slight change in the hull design suggests further development in this regard as well. This means that the general design of the hull and turret, and the mock-up itself, would have been finalized in the coming 7 months when the contract was signed for the prototype production in late March 1984.

Considering the mock-up in the picture is outfitted with tracks, it is also a possibility that the Tamoyo 2 mock-up was later converted to the Tamoyo 2. But this also seems somewhat unlikely, because it would not make sense to convert the Tamoyo 2 mock-up into the Tamoyo 2, but not do this for the Tamoyo 1 by converting the X-30 mock-up.

The writer cannot definitively prove his theory, and would like to add that he does not want to imply that Flavio Bernardini is wrong, as he was present at the time and involved with the project. The writer implies that the picture might have been labeled incorrectly and that, over the period of 20 to 30 years, the exact details might have faded. The writer thus questions the logic and practicality of designing a mock-up for basically the same vehicle, and provides an alternative chain of events to what might have happened. If the Tamoyo 2 mock-up existed, it is very likely that it was either scrapped or converted into the Tamoyo 2.

The Tamoyo 2 Project Begins

What is known is that Bernardini looked into a potential Tamoyo with an HMPT-500 transmission before March 27th, 1984. It is also very likely that Bernardini had already contacted and opened negotiations with General Electric for the transmission before this date as well. The construction of a Tamoyo 2 prototype was made official with the signing of a contract for the construction of 8 Tamoyo prototypes on March 27th, 1984. These vehicles included 4 Tamoyo 1s, a single Tamoyo 2, and three engineering vehicles.

The Tamoyo 2 hull under construction. Source: Bernardini MB-3 tamoyo – Expedito Carlos Stephani Bastos

With the contract signed, work on the Tamoyo 2 began. General Electric provided a single HMPT-500-3 transmission to Bernardini for testing, including all the technical support the company needed. The transmission was coupled with the Scania DSI-14 turbocharged V8 500 hp diesel engine. General Electric engineers visited Bernardini several times to assist in the installation and the initial testing of the transmission.

The HMPT-500-3 transmission at Bernardini. Source: Bernardini MB-3 tamoyo – Expedito Carlos Stephani Bastos

The hull of the Tamoyo 2 was completed around 1986 and was subsequently tested as a sample for a HMPT powered Tamoyo. According to sources, the Tamoyo 2 briefly received the same 90 mm armed turret as the Tamoyo 1, but would be presented with the turret of the Tamoyo 3 in 1987 before May 10th, at an exposition. The Tamoyo 2 thus effectively served as a testbed for both the transmission and the new 105 mm L7 armed turret meant for the Tamoyo 3 for export. In a way, the 105 mm armed Tamoyo 2 was the apex of the Tamoyo 2 program.

The Tamoyo 2 hull during tests at Bernardini. Source: Bernardini MB-3 tamoyo – Expedito Carlos Stephani Bastos

The MB-3 Tamoyo-II-105

The Tamoyo with the Tamoyo 3 turret was designated as MB-3 Tamoyo-II-105 when it was presented at a military exposition, together with the Charrua Armored Personnel Carrier. The sign which accompanied the vehicle stated that it had a 500 hp DSI-14 engine, an HMPT 500 transmission, a maximum speed of 67 km/h, could climb a ramp of 60 degrees and a 30-degree ramp from the side, had an operational range of 500 km, a 105 mm L7 gun, a coaxial machine gun, an advanced fire-control system by Moog AEG and Ferranti Computers, could fire a wide range of ammunition and weighed 31 tonnes combat-loaded.

The 105 mm armed Tamoyo 2 seems to have been short-lived though, as the Tamoyo 3 was already finished and presented on May 10th, 1987 at a Cavalry event in Rio Grande do Sul state, with the 105 mm armored turret. As far as it is known, only one 105 mm armed turret was built by Bernardini.

Effectively, the Tamoyo 2-105 was the cheap version of the Tamoyo 3. The Tamoyo 3 was offered with an HMPT-500 and a CD-850 transmission, albeit paired with a General Motors 8V-92TA 736 hp diesel engine instead. The Tamoyo 2 would also never receive the hull mounted composite armor package which the Tamoyo 3 was planned to receive (the Tamoyo 3 only received the armor package on the hull when the project was canceled). As such, the Tamoyo 2 remained as a test bed, and its development seems to have been canceled after the 105 mm turret was removed and mounted on the Tamoyo 3.

The Tamoyo 2 with the 105 mm gun during a military exposition in 1987. Note the Charrua Armored Personnel Carrier by its side. Source: Bernardini MB-3 tamoyo – Expedito Carlos Stephani Bastos

The HMPT-500-3 vs the CD-500-3

The HMPT-500-3 transmission offered a range of advantages over the CD-500-3. The most notable were horsepower, weight, and space. The HMPT-500-3 transmission could generate up to 600 hp, while the CD-500 was limited to 500 hp. For the Tamoyo 1 and 2, this would effectively mean a hp/tonne ratio increase from 16.67 to 20 hp combat-loaded. In addition, the HMPT-500 transmission occupied 0.62 m3 compared to 0.85 m3. The reduced size meant that the HMPT weighed 862 kg dry (without hydraulic fluid), while the CD-500 weighed 925 kg dry.

The HMPT was also a more efficient transmission over the CD-500. It, for example, determined the hp and torque ratio provided by the engine and the load required by the vehicle to provide better fuel economy, along with an infinitely variable transmission ratio to provide the best torque and hp ratio at as little rpm as possible over three gears (or ranges). Effectively, the higher the gear, the more efficient the transmission, but in every individual gear, the transmission also adapted to provide the most favorable transmission ratio. This meant that the transmission would always operate on the best torque output as possible, while the CD-500 transmission would only operate at maximum torque at a specific point of its gear. The HMPT transmission could also use the engine as a brake by reversing the hydraulic system.

The Tamoyo 2 in Detail

The exact weight of the Tamoyo 2 is uncertain, as there is no document that clearly specifies the weight of the Tamoyo 2. Two weights do recur in documentation, which are 29 and 30 tonnes (32 and 33 US tons) combat loaded. Considering the prototype was designated as X-30, it is quite likely that the actual combat weight was 30 tonnes. Considering the combat weight of the Tamoyo 3 was 31 tonnes (34 US tons) and the empty weight was 29 tonnes, it is estimated that the Tamoyo 2’s empty weight would be around 28 tonnes (30.9 US tons). The Tamoyo 2-105 would weigh 29 tonnes empty and 31 tonnes combat loaded.

The vehicle had a hull length of 6.5 meters (21.3 feet) and was 8.77 meters (28.8 feet) long with the gun pointing forward. It was 3.22 meters (10.6 feet) wide, and 2.2 meters (7.2 feet) tall to turret top and 2.5 meters (8.2 feet) tall in total. The Tamoyo 2-105 was 8.9 meters (29.2 feet) long with the gun pointing forward and 2.35 meters (7.7 feet) tall to the turret top and 2.5 meters (8.2 feet) tall in total.

The tank would have been operated by a four crew members, consisting of the commander (turret middle right), the gunner (turret front right, in front of the commander), loader (turret middle left), and the driver (front hull left).

The Tamoyo 2 hull, together with an M41B. Source: Bernardini MB-3 tamoyo – Expedito Carlos Stephani Bastos

Hull

The hull consisted of a welded homogenous steel construction. With the help of Adriano Santiago Garcia, a Captain in the Brazilian Army, ex-company commander on the Brazilian Leopard 1s, and former instructor at the CIBld (Centro de Instrução de Blindados, Armor instruction center), who knew someone present at the CIBld, the writer has been able to uncover a sizable amount of the armor thickness values of the Tamoyo 1 and 2 by measuring the plate thicknesses, which up to now had not yet been published. The armor is heavier than the M41 Walker Bulldog and was meant to stop 30 mm rounds from the front and 14.7 mm on all sides.

Location Thickness Angle from vertical Relative thickness
Hull
Upper Front 40 mm (1.6 inch) 60º 80 mm (3.15 inch)
Lower front 40 mm (1.6 inch) 45º 57 mm (2.25 inch)
Sides 19 mm (0.75 inch) 19 mm (0.75 inch)
Rear ? ?
Top 12.7 mm (0.5 inch) 90º 12.7 mm (0.5 inch)

The Tamoyo had a headlight and blackout marker on both sides of the upper front hull, with a siren installed behind the right set of lights. Two lifting eyes were welded on both sides of the side upper front plates. In the middle of the upper front plate, in between the sets of lights, were mounting points for a set of spare tracks. The driver was situated on the left side of the upper front plate, and had 3 vision blocks available. The driver’s hatch was a sliding hatch and the driver also had access to a hull escape hatch.

The Tamoyo 2 during a test drive. Note the lack of external equipment, such as headlights and towing hooks. Source: Bernardini MB-3 Tamoyo – Expedito Carlos Stephani Bastos

The hull side provided mounting points for the installation of side skirts, which consisted of 4 sets of skirts on each side. The early versions of the side skirts were made from steel, but would later incorporate materials like rubber and aramid fibers to improve the effectiveness against certain projectiles. The Tamoyo 2 does not seem to have mounted its side skirts.

The Tamoyo had two rear lights on the rear hull plate, and a towing hook on the lower rear plate. In addition to the towing hook, two brackets were installed on this plate and on the lower front plate as well.

The rear view of the Tamoyo 1. Source: Bernardini MB-3 Tamoyo – Expedito Carlos Stephani Bastos

Mobility

The Tamoyo 2 was powered by a DSI-14 turbocharged V8 500 hp diesel engine. This liquid-cooled intercooler engine provided 500 hp and 1,700 Nm (1250 ft-lbs) at 2,100 rpm. This engine gave the Tamoyo a power-to-weight ratio of 16.6 hp/ton (16.1 hp/ton for the Tamoyo 2-105). The Tamoyo 2 used a General Electric HMPT-500-3 hydromechanical transmission, which had 3 ranges forward and 1 for reverse. Combined, this powerpack gave the Tamoyo a top speed of 67 km/h (40 m/h) on level roads. It had a fuel capacity of 700 liters (185 gallons), which gave it a range of approximately 550 km (340 miles). The Tamoyo 2-105 had a range of 500 km.

The Tamoyo 2’s powerpack without transmission. Source: Bernardini MB-3 Tamoyo – Expedito Carlos Stephani Bastos

The Tamoyo used a torsion bar suspension with 6 road wheels and 3 return rollers on each side. It had 3 additional shock absorbers installed, with 2 mounted on the front two road wheels and 1 on the last road wheel. The torsion bars were previously developed by Eletrometal for the M41B program. These torsion bars were made from 300M alloy steel, which was also used for the torsion bars of the M1 Abrams. The idler wheel was mounted on the front side of the vehicle, while the drive sprockets were installed in the rear.

The Tamoyo used Brazilian copies of the T19E3 tracks produced by Novatraçao. The T19E3 tracks had a width of 530 mm (20.8 inch), and a ground contact length of 3.9 meters (12.8 feet). This gave the Tamoyo a ground pressure of 0.72 kg/cm2 (10 lbs/in2) and a trench crossing ability of 2.4 meters (7.9 feet). The tank had a ground clearance of 0.5 meters (1.6 feet) and could climb a 0.71 meters (2.3 feet) tall vertical slope. It could climb a slope of 31 degrees, and be operated on a side slope of about 17 degrees. The vehicle had a fording capability of 1.3 meters (4.3 feet) and could neutral steer as well.

Turret

The Tamoyo 2’s 90 mm turret was armored with welded homogeneous steel plates inclined at various angles. The turret was meant to protect the Tamoyo from frontal 30 mm and all-round 14.7 mm fire. Like with the hull armor, these armor values were uncovered with the help of the writer’s contacts in the Brazilian Army.

Location Thickness Angle from vertical Relative thickness
Turret
Gun Shield 50 mm (2 inch) 45º 70 mm (2.75 inch)
Front 40 mm (1.6 inch) Presented armor angle when firing at the front:
Front top: 60º
Front side: 67º
Front bottom: 45ºAngle of the front side when firing at the side:
20º
Presented relative armor when firing at the front:
Front top: 80 mm (3.15 inch)
Front side: 100 mm (4 inch)
Front Bottom: 57 mm (2.25 inch)Relative armor of the front side when firing at the side: 43 mm (1.7 inch)
Sides 25 mm (1 inch) 20º 27 mm (1 inch)
Rear (not including storage box) 25 mm (1 inch) 25 mm (1 inch)
Top 20 mm (0.8 inch) 90º 20 mm (0.8 inch)

The Tamoyo turret was practically shaped like a less ergonomic M41 turret, because of the usage of flat plates instead of an intricately shaped side plate. It had a turret ring diameter of 2 meters (6.5 feet). The turret had 2 hatches, 1 for the commander and gunner, and one for the loader. The hatch for the commander was located on the middle right of the turret, while the loader’s hatch was located on the middle left. The gunner was located in front of the commander and had a passive day/night periscope located in a depression of the turret top. In addition, the gunner also had access to a direct sight telescope coaxial to the main gun. The commander had 7 periscopes available, which were passive day/night sights. A laser range finder was mounted on top of the main gun.

The P1 Tamoyo (TI-2), note the laser range finder on top of the main gun. Source: Bernardini MB-3 Tamoyo – Expedito Carlos Stephani Bastos

A set of 4 smoke dischargers were mounted on both sides of the turret front. The Tamoyo also had 2 handles on each side, behind the smoke dischargers, to enable the crew to climb on the turret. A pickaxe was mounted on the right side of the turret, behind the handles. Various mounting points for boxes and tools were available on the rear side plate of the turret as well, including a lifting eye on each side on both the rear and front side plates. Finally, a storage box was mounted on the rear of the turret and a jerrycan was then mounted on both sides of the storage box.

The Tamoyo 1 at the CIBld, note the smoke launchers. Source: CIBld

The turret top configuration seems to have undergone some minor changes during the development. Two mounting points for antennas were located on each outer side on the rear top plate. In another turret design, the left mounting point was located just behind the loader’s hatch instead. In between the antenna mountings, was the inlet for the ventilation system, as the Tamoyo had a Nuclear Biological Chemical (NBC) system available. In the middle were the two hatches and in front of the loader’s hatch was another component of which its exact purpose is unknown. In a single picture of the Tamoyo 2 with the 105 mm turret, this location is outfitted with a meteorological system.

The turret was armed with the BR 90 mm gun and a coaxial 12.7 mm heavy machine gun. In addition, the commander’s station could be armed with a 7.62 machine gun for Anti-Air purposes. The turret had an electrical and manual turret drive and the gun had an elevation of 18 degrees and a depression of 6 degrees.

The armor of the 105 mm turret of the Tamoyo 2 is unknown. The base steel armor values might be somewhat similar or slightly thicker than the 90 mm turret, but this is pure speculation. The 105 mm turret was effectively an upscaled and flatter version of the original 90 mm turret but with composite armor.

Rear view of the Tamoyo 3. Not the smoke launchers on the rear of the turret side. Source: Author’s collection

Armament

The Tamoyo 2 was armed with a Brazilian copy of the GIAT 90 mm CS Super 90 F4 gun. The Brazilian designation for this gun was Can 90 mm 76/90M32 BR3. This gun was an L/52 gun that could handle a pressure of 2,100 bars and had a recoil stroke of 550 mm (21.6 inch). The gun had a recoil force of 44 kN for standard ammunition and 88 kN for APFSDS ammunition. The BR3 gun used APFSDS as its main anti-armor round due to the 52 caliber length and the incorporation of the single baffle muzzle brake, which allowed the firing of APFSDS projectiles. The BR3 would have had 5 types of ammunition available to it: canister, high explosive, high explosive anti-tank, smoke, and armor-piercing fin stabilized discarding sabot rounds.

Round Capability Effective range Velocity Weight
APFSDS (Armor Piercing Fin Stabilised Discarding Sabot) Heavy
NATO Single Plate: Point blank (60º 150 mm)
NATO Triple Plate: 600 m
(65º 10 mm, 25 mm, 80 mm to simulate side skirt, road wheel and side hull respectively)Medium
NATO Single plate: 1,200 m (60º 130 mm)
NATO Triple plate: 1,600 m
(65º 10 mm, 25 mm, 60 mm)
1,650 meters (1,804 yards) 1,275 m/s 2.33 kg dart (5.1 lbs)
HEAT (High Explosive Anti Tank) 130 mm (5.1 inch) at 60º from vertical or 350 mm (13.8 inch) flat at any range. 1,100 meters (1,200 yards) 950 m/s 3.65 kg (8 lbs)
HE (High Explosive) Lethal radius of 15 meters (16 yards) 925 meters (1,000 yards)
6,900 meters (7,545 yards) for long range HE
750 m/s
(700 m/s for long range HE)
5.28 kg (11.6 lbs)
Canister Training projectile 200 meters (218 yards) 750 m/s 5.28 kg (11.6 lbs)
White Phosphorus – Smoke Smoke round 925 meters (1,000 yards) 750 m/s 5.4 kg (11.9 lbs)

The Tamoyo had stowage for 68 rounds of 90 mm ammunition. In addition, it was armed with a coaxial 12.7 mm machine gun and could be armed with a 7.62 mm machine gun on the commander’s station for anti-air purposes, with 500 and 3,000 rounds of ammunition respectively. The Tamoyo 1 also had 8 smoke discharges, of which four were installed on each side of the front turret. The turret had an electric and manual traverse system and the gun had an elevation and depression of 18 and -6 degrees respectively.

The fire control system includes a computer with unknown usage, most likely to better integrate the usage of day/night sights and the laser rangefinder which were used by the Tamoyo 1. This could potentially also mean a lead calculator and the integration of a meteorological system, although these were features of the Tamoyo 3, which used a much more advanced fire control system. The electric fire-control system, turret rotation and gun elevation were produced by Themag Engenharia and the Universidade de São Paulo (University of São Paulo). It seems that the Tamoyo 2 did not have a stabilized gun (sources are not very clear), while the Tamoyo 3 did incorporate these features.

The Tamoyo 2-105 offered both a 105 mm gun and a much more advanced fire-control system. The Tamoyo used a 105 mm L7 LRF (Low Recoil Force) gun. The low recoil force enabled the Tamoyo to mount a high-velocity gun while preventing any negative effects the recoil might have due to the lightweight of the Tamoyo. The 105 mm Tamoyo also offered a much more advanced Fire-Control System compared to the original 90 mm Tamoyo. It had a fully electric drive system and was fully stabilized, with a hunter-killer system, passive day-night vision, laser rangefinder, and a more advanced firing computer. The FCS had a meteorological sensor, a ammunition temperature sensor, munition drop calculator, and an ammunition selector.

The 105 mm L7 would offer a large range of ammunition to the Tamoyos. A few rounds would be mentioned here which appear in sources.

Round Capability Effective range Velocity Weight
APFSDS L64 (Armor Piercing Fin Stabilised Discarding Sabot) 170 mm at 60º from vertical at 2,000 meters. 2,500 meters
(2734 yards)
1490 m/s 3.59 kg dart (Tungsten, 28 mm diameter)
APDS L52 (Armor Piercing Discarding Sabot) 240 mm flat from vertical at 2,000 meters.
210 mm at 30º from vertical at 2,000 meters.
120 mm at 60º from vertical at 2,000 meters.
2,500 meters
(2,734 yards)
1426 m/s 6.48 kg projectile
HEAT M456 (High Explosive Anti Tank) 360 mm (13.8 inch) at 30º at any range. 2,500 meters (2734 yards) 1174 m/s 10.25 kg (8 lbs)
HESH (High Explosive Squash Head) A multipurpose round for both anti-armor and anti-personnel purposes. Also used as High Explosive. 732 m/s 11.26 kg (11.6 lbs)
White Phosphorus – Smoke Smoke round 260 m/s 19.6 kg (11.9 lbs)

The turret had an electric elevation and traverse system and offered a gun elevation of 15º and a gun depression of -6º. It had a maximum elevation speed of 266 mils/s or about 15º per second and a maximum traverse speed of 622 mils/s per about 35º per second. It was further armed with a coaxial and turret top 7.62 FN MAG machine gun, although the coaxial machine gun could be replaced with a .50 as an option. The Tamoyo 3 stored 42 rounds of 105 mm ammunition and at least 4000 rounds of 7.62 ammunition. A searchlight was installed coaxial to the coaxial machine gun.

Other Systems

The electrics were powered by a main engine-driven main generator, which produced 24 volts. In addition, four 12 volt batteries were available in order to use the vehicle without starting the main engine. The Tamoyo could receive an NBC system and a heater as optional equipment. The NBC system could be mounted on the already existing ventilation system.

The vehicle used a radio which was also integrated with the M41C and the X1A2 tanks, capable of receiving the EB 11-204D and simpler frequencies. The radio also worked with AN/PRC-84 GY and AN/PRC-88 GY frequencies. The Tamoyo also had an intercom system for the entire crew, which could be linked to the radios. The Tamoyo is said to have had a bilge pump as well, which might have been optional.

Fate

The Tamoyo 2 would never be trialled by the Army and was effectively cancelled with the rejection of the Tamoyo 1. It seems that, after the Osorio trials of 1986, the Brazilian Army realised they wanted a tank like the Osorio and not the Tamoyo they initially thought they wanted. As a result, the trials for the Tamoyo 1 were delayed and, in 1988, it would be rejected due to bad mobility performance.

These mobility characteristics could mainly be blamed on the conception of the Tamoyo program from the very beginning by the Army, and not by Bernardini. The Army specifically wanted a vehicle with as much interchangeability with the M41 as possible. This effectively limited the hp/ton ratio of the Tamoyo 1, as it was limited to a 500 hp engine. Although the Tamoyo 2 did offer a higher horsepower potential, it would not be enough to pass the new Brazilian requirements.

By 1991, the construction of 2 Tamoyo 1’s and the Tamoyo 2 had cost a little under 2.1 million US dollars (4.2 US Dollars in 2021). This suggests that a Tamoyo 2 would have cost about 700,000 US Dollars (1.4 million US Dollars in 2021) to manufacture a piece during the prototype stages. The cost per vehicle might have been less if the vehicle had reached serial production.

In 1991, the Tamoyo 3 was trialed by the Army instead. The Tamoyo 3 would also face a brick wall, as the Army staff was split regarding the Tamoyo 3. One side was in favor of the Army sharing the costs of the evaluation of the Tamoyo 3, while the other side wanted to terminate the entire Tamoyo projects and that the costs of the evaluation should fall solely on Bernardini.

This was because the Tamoyo 3 was classified as a foreign vehicle instead of an indigenous design, since it used a great deal of components which were not yet produced in Brazil. These components included the L7 cannon, automatic fire extinguishing sensors, and the fire control system, among others. The Army definitively canceled the entire Tamoyo project on July 24th 1991. With this decision, Brazil effectively shut down any possibility of an indigenous designed and manufactured main battle tank for the Army.

The P1 Tamoyo (TI-2) during the 1988 trials. Source: Bernardini MB-3 tamoyo – Expedito Carlos Stephani Bastos

Tamoyo 3

With the rejection and cancellation of the Tamoyo project in 1991, the Tamoyo 2 seems to have been scrapped. The engine did survive and remained with Bernardini until their bankruptcy in 2001. The engine was put up for sale together with the Tamoyo 3 prototype. It is unknown if the collector who bought the Tamoyo 3 also bought the DSI-14 engine of the Tamoyo 2.

The Tamoyo 3 when it was put up for sale. Note the additional composite and spaced armor on the hull.Source: Bernardini MB-3 tamoyo – Expedito Carlos Stephani Bastos

Conclusion

The Tamoyo 2 was an attempt by Bernardini to offer a more modern and capable version of the Tamoyo 1. Although the Brazilian Army did not necessarily ask for it, it did agree with the development of the Tamoyo 2. It might be that the Brazilian Army did see potential in the better transmission, or just did not mind that one of the Tamoyo’s they wanted would receive a more modern transmission. The usage of such a new transmission would come with the benefit of getting more experience with modern components and enable more options for the Tamoyo 3 meant for export.

In the end, it seems that the Tamoyo 2 was a victim of its own conception and would only serve as a test bench. The limited horsepower which the transmission could handle was not in accordance with the new requirements set by the Brazilian Army after they trialled the Osorio in 1986. As such, the Tamoyo 2 was left in the cold and the Tamoyo 1 and 2 projects abruptly came to an end after 9 years of development for the Army and by the Army.

Tamoyo 2 testbed. An illustration by Vesp.
Tamoyo 2 testbed. An illustration by Vesp.

Specifications (MB-3 Tamoyo 2)

Dimensions (L-W-H) With 90 mm turret
6.5 meters (21.3 feet) and 8.77 meters (28.8 feet) with the gun pointing forward, 3.22 meters (10.6 feet), 2.2 meters (7.2 feet) to turret top and 2.5 meters (8.2 feet) in total.With 105 mm turret
6.5 meters (21.3 feet) and 8.9 meters (29.2 feet) with the gun pointing forward, 3.22 meters (10.6 feet), 2.35 meters (7.7 feet) to turret top and 2.5 meters (8.2 feet) in total.
Total weight With 90 mm turret
28 tonnes empty, 30 tonnes combat-loaded (30.9 US tons, 33 US tons)With 105 mm turret
29 tonnes empty, 31 tonnes combat-loaded (32 US Tons, 34 US tons)
Crew 4 (commander, driver, gunner, loader)
Propulsion DSI-14 turbocharged V8 500 hp diesel engine
Suspension Torsion bar
Speed (road) 67 km/h (40 m/h)
Armament 90 mm BR3 (temporary 105 mm L7 LRF)
Coaxial .50 caliber MG HB M2
Anti-Air 7.62 mm mg
Armor (with 90 mm turret) Hull
Front (Upper Glacis) 40 mm at 60º (1.6 inch)
Front (Lower Glacis) 40 mm at 45º (1.6 inch)
Sides 19 mm at 0º (0.75 inch)
Rear ?
Top 12.7 mm at 90º
(0.5 inch)
Turret
Front 40 mm at 60/67/45º (1.6 inch)
Gun mantlet 50 mm at 45º (2 inch)
Sides 25mm at 20º (1 inch)
Rear 25 mm at 0º (1 inch)
Top 20 mm at 90º (0.8 inch)
Produced 1

Sources

Blindados no Brasil – Expedito Carlos Stephani Bastos
Bernardini MB-3 Tamoyo – Expedito Carlos Stephani Bastos
M-41 Walker Bulldog no Exército Brasileiro – Expedito Carlos Stephani Bastos
M-113 no Brasil – Expedito Carlos Stephani Bastos
Jane’s armour and artillery 1985-86
Brazilian Stuart – M3, M3A1, X1, X1A2 and their derivatives – Hélio Higuchi, Paulo Roberto Bastos Jr., and Reginaldo Bacchi
Moto-Peças brochure
Memoir of Flavio Bernardini
Author’s collection
Bernardini compra fábrica da Thyssen – O Globo, archived by Arquivo Ana Lagôa
The Centro de Instrução de Blindados
Tecnologia & Defesa magazines with courtesy of Bruno ”BHmaster”

With Expedito Carlos Stephani Bastos, Expert in Brazilian Armoured Vehicles
With Paulo Roberto Bastos Jr., Expert in Brazilian Armoured Vehicles
With Adriano Santiago Garcia, A Captain of the Brazilian Army and ex-company commander on the Leopard 1

Categories
Cold War Brazil MB-3 Tamoyo Cold War Brazilian Armor

MB-3 Tamoyo 1

Brazil (1984-1991)
Medium Tank – 4 Built + 1 Mock-up

The development of a national tank in Brazil started as early as 1969, with the founding of the Centro de Pesquisa e Desenvolvimento de Blindados (CPDB) (English: Centre for the Research and Development of Tanks). The CPDB studied the possibilities of locally produced tanks and initiated its first project in the early 1970s, which would become the X1 light tank family.

Bernardini, the company which developed the X1 family together with the Parque Regional de Motomecanização da 2a Região Militar (PqRMM/2) (English: Regional Motomecanization Park of the 2nd Military Region), went on to develop the M41B. The successful development of the M41B gave Bernardini enough confidence and experience to initiate the development of a national tank together with the Army.

Before Engesa’s Osório rose to prominence, Bernardini initiated the development of their national tank in the late 70s. This project was called the MB-3 Tamoyo. The MB-3 Tamoyo started off as an improved version of the M41 Walker Bulldog, sharing as many components as possible to ease logistics, but would reach its apex as the Tamoyo 3, which could be classified as a full-fledged Main Battle Tank in South America. It is important to note that the Tamoyo’s were not conversions from the M41, but completely new designs.

Although the Tamoyo, and especially the Tamoyo 3, had much potential and fitted the initial requirements of the Brazilian Army, they were not selected and were overshadowed by the Osório. The Tamoyo’s were tested very late in comparison to the Osório, and it seems that this delay caused the Army to realise that they did not want the Tamoyo 1. They wanted a main Battle Tank like the Osório and the Tamoyo 3. In the end, the Tamoyo would end up as the most realistic tank for Brazil, but would never come to fruition.

The Tamoyo 1.
Source: Author’s collection

Designations

The Tamoyo had various designations to denote the stages of the project. The first stage of the Tamoyo was designated X-30, with the X standing for prototype and the 30 for its 30 tonnes weight. This designation was used until the first working prototype of the Tamoyo 1 was delivered in May 1984.

There is also the VBC CC XMB3 (Viatura Blindada de Combate – Carro Combate – X Médio Bernardini-3, Armored Fighting Vehicle – Combat Car – X Medium Bernardini-3) designation, which is seen at a sign accompanying the mock-up of the Tamoyo and is written on the sides of most variants of the Tamoyo as well. The X again denominates the prototype phase of the vehicle, and the MB refers to the designer and manufacturer of the vehicle. The 3 denotes that this is the third vehicle Bernardini ‘’designed’’, with the 1 being the X1, the X1A1 being the 1A, the X1A2 being the 2, and the X1A2 second production batch being known as 2A. What is interesting is that the M41B and M41C projects of Bernardini were not counted in the MB-X designation system of the company.

The X-30 mock-up with a sign stating VBC CC XMB 3 at the CTEx.
Source: https://foursquare.com/v/centro-tecnol%C3%B3gico-do-ex%C3%A9rcito-ctex/4e1486e514951daa08ab2fcc?openPhotoId=5139f29fe4b02b1b3eb660de

The earliest mention of the Tamoyo designation was recorded in November 1983, named to honor the Tamoyo Confederation of the Tupinambá people. The Tamoyo Confederation was an alliance of various indigenous tribes of Brazil in response against the slavery and murder inflicted on the Tupinambá tribes by the Portuguese discoverers and colonizers. The Tupinambá people fought against the Portuguese from 1554 to 1575. A peace treaty between the two warring parties was signed in 1563, although the fighting did not completely end until 1567, after the Portuguese colonists were sufficiently strengthened to tip the scales completely in their favor. The Tamoyo Confederation was effectively wiped out by 1575. Tamoyo means grandfather or ancestor in the Tupi language.

A Tamoyo warrior, painted by Jean-Baptiste Debret.
Source: https://artsandculture.google.com/asset/charruas-chief/jAFUsCu7mHJ5XQ?hl=fr&ms=%7B%22x%22%3A0.5%2C%22y%22%3A0.5%2C%22z%22%3A9.01566727112745%2C%22size%22%3A%7B%22width%22%3A3.954717967284%2C%22height%22%3A1.2374999999999998%7D%7D

It seems that after the first Tamoyo prototype was built on May 7th 1984, that the Tamoyo received its official designation MB-3 Tamoyo. The MB-3 Tamoyo has 3 main sub designations, these are Tamoyo I, Tamoyo II, and Tamoyo III (named Tamoyo 1, 2, and 3 in this article for ease of reading). The Tamoyo 1 refers to the Tamoyo meant for the Brazilian Army, armed with a 90 mm BR3 gun, DSI-14 500 hp engine and a CD-500 transmission. The Tamoyo 2 was exactly the same as the Tamoyo 1, except that it used a modern HMPT-500 transmission. The Tamoyo 3 refers to the export version, which was a much-upgraded version of the original Tamoyo. The Tamoyo 3 was armed with a 105 mm L7, had an 8V-92TA 736 hp engine, a CD-850 transmission, and was armored with composite armor instead of only steel. The Tamoyo 3 would eventually be proposed to the Brazilian Army as well in 1991, a year after the failure of the EE-T1 Osório.

The 8 vehicles which were planned, and the first prototype received individual designations as well. These designations went from P0 to P8 and had sub-designations regarding their models as well. The first working prototype was designated P0 and held the model designation TI-1, where TI refers to Tamoyo 1 and the 1 refers to the first Tamoyo 1 vehicle. There were also three support vehicles envisioned, which were a bulldozer, bridgelayer, and engineering vehicle. These are denoted by VBE (Viatura Blindada Especial, Special Armored Vehicle)

The Tamoyo TI-1, TI-2, TI-3, and TI-4 will be the four main vehicles of interest in this article. These are all Tamoyo 1s with slight variations between them, from the location of pioneer tools, to the mounting of a Laser Range Finder. It is important to note that the overall development of all the different Tamoyos is intertwined. Thus, there are a reasonable amount of references to other Tamoyo versions in this article. Please refer to this table of designations to prevent possible confusion of all the various designations that distinguish the individual vehicles from each other.

Tamoyo Type Prototype Model designation
Tamoyo 1 P0 TI-1
Tamoyo 1 P1 TI-2
Tamoyo 2 P2 TII
Tamoyo 1 P3 TI-3
Tamoyo 3 P4 TIII
Tamoyo 1 P5 TI-4
Engineering Tamoyo P6 VBE Bulldozer
Engineering Tamoyo P7 VBE Bridge Layer
Engineering Tamoyo P8 VBE Engineering

Genesis

The development of the Tamoyo can be traced back to the X1. The X1 was a modernization project of the M3 Stuart, carried out by the PqRMM/2 team, Biselli and Bernardini. Bernardini was responsible for the turret and the suspension. After the X1, the team would try to fix some of the vehicle’s flaws by designing the X1A1. The X1A1 was effectively a lengthened X1 tank with a hybrid M4 Sherman/18-ton M4 Tractor suspension and a redesigned turret. The X1A1 project ended up breaking the X1 even more and was canceled. Biselli left the X1 project around this time in the mid-1970s, making Bernardini fully responsible for the X1 family of vehicles and all future tank development.

The X1.
Source: Blindados no Brasil

The X1A1 was canceled, as it was too much effort to fix the old base M3 Stuart. The engineers would have needed to widen the Stuart hull, and would still retain issues inherent to the age of the hull. It was decided to develop a new tank, which was designated X-15. The X-15 would be the first fully designed tank in Brazil, which resulted in the X1A2 tank.

The X1A2 used the same suspension and a further developed turret of the X1A1. The X1A2 hull was wider than the X1A1, fixing the issues of the X1A1. The tank used several new components, of which the most notable were the EC-90 low-pressure gun, and the CD-500 transmission. Both the CD-500 transmission and the design concepts of the X1A2 turret were later incorporated in the Tamoyo 1 project. The X1A2 was Brazil’s first and so far only tank which was fully designed in Brazil and used in active service. The X1 family of projects and the X1A2 gave the engineers of Bernardini the experience and confidence to start developing the M41 Walker Bulldog upgrades.

The X1A2.
Source: Image Caiafa

The M41 Projects

With the success of the X1 family project, Bernardini and the Brazilian Army initiated the development of the M41 upgrade programs. This started much the same way as the other projects of the Brazilian Army. The first step was to remotorize the M41 with a locally produced Scania DS-14 V8 350 hp diesel engine. This upgrade was designated as M41B and included various other smaller upgrades beside the engine. The first M41B was built in 1978.

The M41B
Source: M-41 Walker Bulldog no Exército Brasileiro – Expedito Carlos Stephani Bastos

Bernardini had now gained enough confidence to start developing their own tank. A year later, Bernardini started the development of what would become the Tamoyo 1. Bernardini also went on to further develop the M41B upgrade into the M41C, parallel to the development of the Tamoyo. The first M41C was developed around 1980 and mounted the same engine, a turret with additional spaced armor, a rebored 90 mm low-pressure gun, and a multitude of other minor upgrades and upgrade packages. A single M41C would end up as a testbed for the high-pressure 90 mm armament of the Tamoyo 1.

The M41C armed with the 90 mm F4.
Source: M-41 Walker Bulldog no Exército Brasileiro – Expedito Carlos Stephani Bastos

The German proposals of 1976-1977

Beside the projects of Bernadini, the Germans also seemed to have some influence during the concept stages of the Tamoyo 1 development. Previous military relations between the US and Brazil had declined and, in 1977, Brazil and the US broke off their military agreements. This break was caused by the German-Brazilian nuclear energy cooperation and the lost usefulness of the military agreement for Brazil. Germany tried to capitalize on the declining relations by proposing a range of vehicles to the Brazilian Army.

Two of these vehicles were tanks, of which one was essentially a TAM tank for Brazil, and the other a 35-tonne tank. The TAM was still being designed by the Germans and Argentinians around this time, and the first prototype of the TAM was completed in September 1976 for Argentina. The 35 tonnes tank had a much more conventional layout compared to the TAM, as it did not have an engine located in the front of the vehicle. Brazil did not buy either of these tanks, preferring to rely on their own industry to build a new tank.

It is thought that the proposal by the Germans and the appearance of the TAM in Argentina influenced the initial concept stages and design requests by the Brazilian Army for the Tamoyo project. If this influence came directly from the German proposals or from the usage of the TAM in Argentina is unclear. Both factors probably contributed in varying importance to the requests of the Brazilian Army.

The TAM proposal for Brazil.
Source: Blindados no Brasil – Expedito Carlos Stephani Bastos

Bernardini

Bernardini SA Indústria e Comércio was founded by Italian immigrants in 1912. They manufactured steel safes, armored doors, and value transport vehicles. In the 1960s, Bernardini would come in contact with the Armed Forces by building the bodies for trucks for both the Brazilian Marine Corps and the Army. In 1972, the company was asked by the Army to participate in the PqRMM/2 project to develop the X1 tank with Biselli.

Bernardini’s participation in the X1 project solidified their position as the company responsible for building tanks in Brazil. The Brazilian defense industry was founded with a gentleman’s agreement to prevent competition between the various companies involved. Engesa initially focused on wheeled vehicles, for example. The main difference between the two companies was that Engesa was very much export-driven, while Bernardini carried out projects according to the needs of the Brazilian Army and then looked at potential export possibilities. In a way, Bernardini was much more dependent on the Army, while Engesa was dependent on selling their equipment abroad.

This difference in policy can be seen in the total amount of exports of Bernardini compared to the rest of the Brazilian defense industry. Bernardini exported 5% of their total production compared to 80 to 95% of the rest of the Brazilian defence industry. Although this made Bernardini less susceptible to failed export bids, it did make Bernardini dependent on an Army with an ever-tight budget.

Bernardini logo.
Source: http://www.lexicarbrasil.com.br/bernardini/

The X-30

The Brazilian Army staff was worried about the Argentinian acquisition of the TAM tank. The TAM effectively outclassed any vehicle the Brazilian Army owned in firepower, armor, and in the mobility department. In comparison, the most advanced tank of the Brazilian Army was the M41 Walker Bulldog, which was still in the initial stages of modernization. As a result, the Army staff decided that Brazil needed a new tank.

The specifications of the new tank were released around 1979 by the CTEx (Centro Tecnológico do Exército (CTEx, Army Technology Center), which was led by Division General Argus Fagundes Ourique Moreira. Division General Argus Moreira and the CTEx were responsible for the acquisition of funds from the Army for the project, and to give input in the selection of components, design, and companies working on the new tank. The CTEx effectively participated in this project to ensure that the Army would receive a feasible Carro de Combate Nacional Médio (National Medium Combat Car/tank, the Brazilian army calls all their tanks combat cars). This basically meant that they would get a tank, capable of dealing with the TAM and with a favorable price tag for the Army. For this project, the CTEx selected Bernardini as its partner.

Division General Argus Fagundes Ourique Moreira
Source: CTEx

A range of requirements for the new tank were put forward by the CTEx for both an indigenous and export version. What is interesting, is that the Army seems to not have completely abided by these requirements when they accepted the Tamoyo projects. The Army wanted a tank that weighed 30 tonnes (33 US tons, although this later seems to have increased to 36 tonnes (39.7 US tons) and was 3.2 meters (10.5 feet) wide for rail transport (same width as the Leopard 1), an operational range of around 500 km (310 miles), a ground pressure of roughly 0.7 kg/cm2 (10 lbs/in2), a high percentage of locally-produced components as possible, and have as many commonality of parts as possible with the M41 and the Charrua for logistical reasons. The Charrua was a locally designed tracked troop transport that was meant to replace the M113.

The Charrua.
Source: Author’s collection

In addition, the vehicle had to use a conventional layout, a turret with 3 crewmen (there was no interest in autoloading systems), the national vehicle was to be armed with a 105 mm gun, while the export vehicle was to be armed with a 120 mm gun, a stabilized gun, day/night sights, armor that should provide a high level of protection, diesel engines which gave the vehicles good power to weight ratios, and a fire extinguishing system.

As an interesting bit of information, although mainly for the Tamoyo 3, Bernadini visited Israel a number of times for consultation by General Talik Tal, the mastermind of the Merkava tank. In addition, Bernardini also hired General Natke Nir (sometimes referred to as Natan Nir), who served as a Colonel during the Yom Kippur War, for 6 months as a consultant for the design of armored vehicles. Natke Nir is credited by Flavio Bernardini for introducing spaced and composite armor concepts, improved protection against explosions, ammunition compartmentalization, mine protection, and the employment of tanks in combat situations. Although these consultancies were mainly focused for the Tamoyo 3, it would not be surprising if some concepts were or would eventually be carried over to the Tamoyo 1 as well.

General Natke Nir, picture taken in 1979.
Source: The National Library of Israel

How many Tamoyos did the Army want?

It is unknown how many Tamoyo’s the Army intended to acquire from Bernardini. A couple of estimations can be made to give some idea of the planned Tamoyo’s to be fielded by the Army. The first number is based on the German proposal of the TAM tank for Brazil, which was for at least 300 vehicles. This number also appears in other estimations of how many Osório’s the Army would potentially buy, which ranged from 70 to 300 Osório’s.

Another estimation can be made by basing it on the number of M41C’s Brazil operated at the time, and on the number of Leopard 1’s Brazil is operating today. 323 M41C’s were built by Bernardini for the Army. Although the Tamoyo 1 was meant to operate besides the M41C, it is quite likely that the M41C’s would be gradually phased out as more Tamoyo’s were delivered. This for example happened when the Army bought 378 Leopard 1’s in total. In an issue of International Defense Review, it is stated that the army has a requirement of 300-400 vehicles.

Although the exact number is unknown, both Brazilian and foreign sources, and previous and later events seem to suggest a number of around 300 to 400 vehicles. This is a sizable number compared to the 231 TAMs operated by the Argentinian Army.

The X-30 TAM

Division General Argus Moreira initially requested a tank with a front-mounted engine and rear turret, like the TAM. The tank and the project were designated X-30 (X for prototype and 30 for 30 tonnes (33 US tons)), and the first concept art was released to the public in the newspaper O Estado de São Paulo on May 27th 1979. The article practically presents an improved copy of the TAM, although some of the combined requirements seem to have been somewhat unrealistic when one considers the TAM specifications. The new Brazilian X-30 tank was presented as a 30-tonne tank, armed with a 120 mm cannon, telemetric laser finder, a range of 600 km (370 miles), armor up to 70 mm (2.75 inch), NBC system, fire-extinguishing systems, 4 crewmen, dual controls, and heat-treated armor angled at 20 to 50 degrees. It was also supposed to be able to mount Brazilian copies of the Roland Surface-to-Air Missile system, although Brazil would never manage to successfully copy the SAM system.

To put these specifications in perspective, the TAM weighed 30.5 tonnes (33.6 US tons), had a 105 mm cannon, 590 km (366 miles) operational range, armor up to 50 mm (2 inch), a crew of four, and armor angled from 32 to 75 degrees. The amount of road wheels of the X-30 is also exactly the same as on the TAM, suggesting more or less equal dimensions as well. The interesting part is that the X-30 effectively promised a better gun and better armor, while weighing as much as the TAM.

This presentation of the X-30 seems more of a propaganda article with the technician, who gave the information to the journalist, sketching a very impressive and capable vehicle that the Brazilian Army would most likely not have been able to afford in the first place. The construction of a steel mock-up that used the front-engine configuration was already underway, but would never be finalized. The TAM-inspired design was very short-lived, as Bernardini and the CTEx opted for a traditional lay-out in less than 6 months.

The X-30 with the TAM lay-out.
Source: Bernardini MB-3 Tamoyo – Expedito Carlos Stephani Bastos

The actual design of the X-30 TAM concept appears in an undated video of Bernardini where a show briefly shows the design. The design resembles the sketch from the newspaper with some changes. The smoke launchers are located on the front of the turret, there is no structure on the sides of the turret for the commander and loader hatches, the vehicle has an extra structure on the top of the hull which can be seen by the lower placed driver sights, and the vehicle has 3 return rollers instead of 4. The armament shown in the design of Bernardini is unknown, but is thought to be a 105 mm gun. The sketch does not yet take the engine placement into account, although this might have to do with the drawing not being finished. The construction of a steel mock-up that used the front-engine configuration was already underway, but would never be finalized. The TAM-inspired design was very short-lived, as Bernardini and the CTEx opted for a traditional layout in less than 6 months.

The X-30 TAM design as shown in the video from Bernardini.
Source: https://youtu.be/7oaZfsQYSMk

The Traditional X-30

The front-mounted engine design was discussed with Bernardini, considering weight balancing, armor distribution, and the moments of forces and inertias. In the end, Bernardini and the Army decided to go for a traditional layout with a rear-mounted engine. A contract between the Army and Bernardini was signed and the development of a mock-up and prototype was initiated. The switch to the traditional design happened anywhere between May 1979 and January 1980.

Transmissions and Engine

The first step in developing the new tank was the selection of a transmission. The Brazilian Army wished for the CD-500-3 transmission to ensure interchangeability with the M41 Walker Bulldog fleet and because of an envisioned M113 replacement. The M113 replacement was named Charrua and in development by Moto-Peças. The project would never go further than the prototype phase. Considering the CD-500 transmission was no longer in production, Bernardini thought that it could obtain the designs from General Motors Allison and start producing the CD-500 transmission and spare parts in Brazil.

CD-500 transmission.
Source: TM 9-1730B – Maintenance Cross-Drive Transmission model CD-500

Bernardini decided that it would be a wise decision to offer the X-30 with a more modern transmission as well. Bernardini started negotiations with General Electric to obtain the HMPT-500-3 transmission, as used on the M2 Bradley. The advantage of the HMPT-500 was that it would allow the use of more powerful engines up to 600 hp, and thus give the eventual Tamoyo more upgrade potential. The HMPT-500 Tamoyo would eventually be designated as Tamoyo 2 after Bernardini had requested permission for the funds to develop it in June 1984.

With the selection of the CD-500 and HMPT-500 transmission, Bernardini was effectively bound to the Scania DSI-14 V8 500 hp diesel engine. This was not necessarily bad regarding the logistical structure of the Brazilian Army, considering the interchangeability with the M41s, but it would limit the power to weight ratios of the Tamoyos severely and even cause significant issues in the end.

HMPT-500-3 transmission.
Source: https://grabcad.com/challenges/cydesign-part-5-general-dynamics-land-systems-hmpt-500-transmission

Arming the Tamoyo

The process of arming the Tamoyo began parallel to the process of rearming the M41C. Since the 76 mm ammunition was not being produced anymore by the United States, Bernardini and the Army decided that rearming the M41C was the way to go. The Army did some research in the possibilities on how to rearm the M41C, and after they tested a rearmed M41B with an EC-90 90 mm low pressure gun of the Cascavel, the Army decided that reboring the original guns to 90 mm would be the most affordable decision.

As such, the first batch of 76 mm guns were rebored at Engesa to have the same rifling as the EC-90 and were even cut down to the same caliber length as the EC-90 (later, they would discover that cutting the barrels from the original 4.5 meters (14.8 feet) to 3.6 (11.8 feet) did not provide any advantages). Both these cannons used the same low-pressure ammo as the EE-9 Cascavel and were designated ‘Can 90mm 76/90M32 BR1’ (shortened barrel) and ‘Can 90mm 76/90M32 BR2’ (long barrel).

M41C with the BR2 gun.
Source: http://www.lexicarbrasil.com.br/bernardini/

Parallel to the development of the BR1 and BR2 guns, the Brazilian Army and the CTEx also looked into arming the M41C with a GIAT 90 CS Super Gun, also known as the Super 90 of 90 mm F4. The Super 90 had a longer barrel than the EE-9 Cascavel’s EC-90 guns, which made them more fitting for firing kinetic ammunition. The low-pressure EC-90, the BR1, and the BR2 relied on HEAT ammunition to take out their opponents due to the lacking muzzle velocity in order to lessen the recoil of the guns. The Super 90 used a single baffle muzzle brake which allowed the gun to fire APFSDS ammunition.

A single Super 90 gun was purchased, together with about a thousand APFSDS rounds. The CTEx proceeded to test the gun and to take apart the APFSDS round in order to develop their own APFSDS round for local production. During these tests, the Brazilian Army determined that the Super 90 could also be mounted on the M41 Walker Bulldog. As a result, a single M41C mounted the Super 90 gun, potentially to one day arm the entire M41C fleet of Brazil or simply as an export option for Bernardini. In the end, this single M41C would be nothing more than a testbed for the Super 90 gun and ammunition.

The Brazilians copied the Super 90 gun and designated it ‘Can 90mm 76/90M32 BR3’. As this designation suggests, these guns were and could be converted from the 76 mm gun of the M41 Walker Bulldog. The BR3 gun was selected by the Army to arm the Tamoyo 1 and 2 tanks to take on the TAM tanks of Argentina. This decision makes it clear that the Brazilian Army originally did not intend to operate a tank with a 105 mm gun like the TAM, mainly due to budget constraints, but probably realized with the EE-T1 Osorio that the 105 mm was the new standard.

The BR3 gun during tests.
Source: Bernardini MB-3 Tamoyo – Expedito Carlos Stephani Bastos

Working towards a Mock-Up

From this point on, development becomes a bit vague. This mainly has to do with a lack of dates on when concept arts were made and when the first mock-up was actually built. There are about 3 concepts that are estimated to have been made before the mock-up was made. The writer proposes a certain timeline on the order of the designed concepts. This proposal is not confirmed by hard evidence or dates, but is speculation based on design steps taken in comparison with either previously developed vehicles or on how much the design has been worked out in the details. The date when the mock-up was finished is unknown, but can be estimated in between 1980 and 1984.

Jane’s Concept

A concept sketch of the X-30 was presented in the first issue of Jane’s 1980 International Defence Review. A description of the concept was given as well, stating that the drawing shows Bernardini’s project for a 30-tonne medium tank, designated X-30, which was currently in the definition phase. It would have a Diesel engine of 520 to 745 kW (700 to 1000 hp), an automatic transmission, have a range of 500 km (310 miles) and a ground pressure of about 0.7 kg/cm2 (10 lbs/in2), of which the last two specifications were based on the Brazilian Army’s requirements. According to the Brazilian correspondent, it was to be armed with either a 105 mm or 120 mm gun, although the current concept shows a Cockerill 90 mm gun. In addition, it is stated that the first prototype was estimated to be ready for trials in two years.

The concept sketch presented in Jane’s IDR.
Source: Jane’s 1980 International Defence Review

This concept is estimated to be the first concept for two reasons. The first is the date when this concept was released (January 1980), which means that this concept was made about 6 months after the first TAM-inspired concept. The second reason is that this concept is nothing more than a mash-up of two tanks previously designed by Bernardini.

Jane’s concept mixes an enlarged X1A2 turret with the hull of an M41B. The concept derives in two major ways from the two vehicles it is based on. The first is that the hull is longer, as it has 6 road wheels instead of 5 on the M41, and the second is that the main gun looks like a lengthened EC-90 gun of the X1A2 with an added bore evacuator. Another difference is the driver’s hatch, which does not correspond with either vehicle.

X1A2 during ramp tests at the PqRMM/2.
Source: Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivatives

It seems that this concept was already based on the specifications of the export version of the Tamoyo, which was the Tamoyo 3. There are a few interesting statements though. The first is the engine power, which is denominated in kW instead of hp. This was probably some kind of mix-up between units, as 520-745 kW translates to 700-1000 hp, considering the given specifications are very close to the horsepower values which Bernardini presented for the DSI-14 and 8V-92TA engines.

The M41B, note the engine deck.
Source: M-41 Walker Bulldog no Exército Brasileiro – Expedito Carlos Stephani Bastos

Overall, this concept seems to be mainly suggesting a potential export version of the X-30 instead of the X-30 for the Brazilian Army. This concept is potentially one of the first drawings of the X-30 in a traditional layout. The design itself is somewhat unimaginative, considering it’s a mash-up of the X1A2 and the M41B, and the specifications are somewhat questionable as well.

An Artistic Interpretation

This concept was released in the press and abroad after the switch to the traditional layout. This concept dates back to at least April 1980, as the sketch is shown on the cover of Brasil Defesa – Os Blindados do Brasil. In this sketch, the X1A2 turret is a little bit altered, but uses a redesigned hull that resembles the final hull design much closer.

This concept retains a redesigned variant of the X1A2 turret, but the hull in this concept is different. The hull shares much fewer design features with the original M41 or the Brazilian M41B and M41C. The engine deck looks more like a main battle tank and resembles the Tamoyos which were built. The tracks of the concept do show a very clear resemblance to the M41 tracks. The gun on this concept is unknown, but it does seem to resemble a 105 mm gun, although this is pure speculation.

The artist rendition of the X-30.
Source: Brasil Defesa – Os Blindados do Brasil

The Tamoyo Maquette

The next design was a wooden mock-up. This design might have been built between the concept sketch phase and the full-scale mock-up production phase, although this is not confirmed. This model is almost identical to the full-scale mock-up. The hull and turret shapes are effectively the same, although the gun is indistinguishable. This design is also the first design that incorporates side skirts.

Unusually, this vehicle has Tamoyo and Selva written on it. If this was done when the wooden model was originally built or if it received a repaint afterward, is unknown. It is not known where Selva comes from, but it might refer to the builder of the mock-up or to jungle, as Selva translates to jungle. This mock-up is preserved at the CTEx.

The wooden mock-up.
Source: Bernardini MB-3 Tamoyo – Expedito Carlos Stephani Bastos

The Full-Scale Mock-Up

A mock-up of the X-30 was built somewhere in between 1980 and 1984. This mock-up was a full-scale metal model which shared some components of the M41 Walker Bulldog to make production easier. It is important to note that the mock-up and the Tamoyo project as a whole were not lengthened M41s or converted M41s in any way.

The X-30 mock-up used the M41 suspension, Brazilian copies of the T19E3 tracks produced by Novatraçao, and an altered 76 mm gun of the M41 (with a muzzle brake of the Super 90). The design of the previous X-30 mock-up was practically unaltered. The X-30 was, in principle, the shell of the Tamoyo 1 without all the components like smoke launchers, sights, hooks and so on. The X-30 is preserved as a monument at the CTEx.

The X-30 mock-up.
Source: Bernardini MB-3 tamoyo – Expedito Carlos Stephani Bastos

The Tamoyo 2 Mock-Up?

According to Flavio Bernardini, then one of the CEO’s of Bernardini, Bernardini also produced a mock-up of the Tamoyo 2. Although this is probably true, it does not make much sense. The only difference between the Tamoyo 1 and the Tamoyo 2 is the transmission of the vehicle. The rest of the design remained unchanged in the initial stages.

The Tamoyo 2 mock-up.
Source: Bernardini MB-3 tamoyo – Expedito Carlos Stephani Bastos

Even more confusing, the picture of the mock-up is dated August 1983. The lower hull is more or less completed, but the turret is a styrofoam mock-up. This styrofoam mock-up is almost exactly the same as the X-30 mock up except for a few details, like lifting eyes. In addition, the gun presented on the Tamoyo 2 mock-up is a dummy of the 76 mm from the M41. The rear side hull plate does look different from the eventual X-30 mock-up, as the rear part does not widen as gradually.

Another detail that makes this mock-up confusing is that the contract for the development of the Tamoyo 2 was signed in 1984 and not 1983. It is possible that Bernardini proposed this upgrade earlier on, which could explain the existence of the mock-up.

Finally, it is unknown what happened with the Tamoyo 2 mock-up, while the X-30 mock-up was preserved at the CTEx. This makes it impossible to either fully prove or disprove that a Tamoyo 2 mock-up existed. For all we know, it was scrapped, or it was integrated with the current X-30 mock-up preserved at the CTEx.

The writer thus somewhat questions the existence of the Tamoyo 2 mock-up and suggests that it might just be the X-30 mock-up in early stages. This would not be very unlikely, as the contract for the production of the Tamoyo prototypes between the Army and Bernardini was only signed in March 1984. The styrofoam turret suggests that, as of late 1983, no steel mock-up turret was available, and the slight change in the hull design suggests further development in this regard as well. This means that the general design of the hull and turret, and the mock-up itself, would have been finalized in the coming 7 months when the contract was signed for the prototype production in late March 1984.

Considering the mock-up is outfitted with tracks, it is also a possibility that the Tamoyo 2 mock-up was later converted to the Tamoyo 2. But this also seems somewhat unlikely, because it would not make sense to convert the Tamoyo 2 mock-up into the Tamoyo 2, but not do this for the Tamoyo 1 by converting the X-30 mock-up.

The writer cannot definitively prove his theory, and would like to add that he does not want to imply that Flavio Bernardini is wrong, considering Flavio Bernardini was present at the time and involved with the project. The writer implies that the picture might have been labeled incorrectly and that, over the period of 20 to 30 years, the exact details might have been hard to remember. The writer thus questions the logic and practicality of designing a mock-up for basically the same vehicle, and provides an alternative chain of events to what might have happened.

The Tamoyo 1 Has Been Built

The first working prototype was delivered on May 7th, 1984, and received the official designation MB-3 Tamoyo. The Tamoyo used a high number of locally-produced components, with the suspension, gun, steel for the hull and turret, engine, and the electric turret drive being produced in Brazil. Bernardini specifically selected as many components as possible which could be manufactured in Brazil through license deals or subsidiaries in Brazil itself to make the Tamoyo as indigenous as possible, which included the CD-500 transmission. The prototype was successfully tested by the Army two days after completion in Rio de Janeiro.

Suppliers Tamoyo 1
Country Company Component(s)
Brazil Bernardini Hull, turret, suspension components, electric turret and elevation drives
Brazil Themag Engenharia Electric turret and elevation drives
Brazil Universidade de São Paulo Electric turret and elevation drives
Brazil Eletrometal Torsion bars
Brazil Usiminas Steel
Brazil Novatracão Tracks and suspension components
Brazil D.F. Vasconcellos Driver’s day sights (unknown if they suppied the driver’s night vision sight
Brazil Brazilian Army Funding
Sweden-Brazil Scania do Brasil DSI-14 500 hp engine
United States General Motors Allison CD-500-3 transmission
United States Unknown Turret slewing bearing

Interestingly enough, the CTEx and Bernardini had already signed a contract for the construction of 8 Tamoyo 1s on March 27th, 1984. This might suggest that the full-scale mock-up was finished not too long before March 27th and that the first working Tamoyo 1 prototype might have been built between March 27th and May 1984, although this is more speculation.

As stated, the contract covered 8 vehicles, of which 4 were Tamoyo 1s, 1 was a Tamoyo 2, and 3 were engineering vehicles (Bulldozer, Bridge Layer, and Recovery vehicle). The first working prototype was included in this contract. The Tamoyo 3, meant for export, was logically not included in this contract, although the Army did need to give permission to Bernardini to develop an export version. With the signing of the contract, Bernardini ordered 15 CD-500 transmissions for both the Tamoyo and the Charrua project, of which 5 CD-500’s were passed to Moto-Peças.

The Brazilian Cousin of the Stig preparing to test drive the Tamoyo 1 in 1984, note the X1A1 or X1A2 in the rear.
Source: Tecnologie & Defesa Magazine volume 14 with courtesy of Bruno ”BHmaster”

Building the Tamoyos

Bernardini had two locations available for the construction of the Tamoyo. The first was located in the Ipiranga district of the city of São Paulo in São Paulo state. This factory had a production floor of about 20,000 m2 and would focus on the production of components for the Tamoyo 1. The second factory was located in the city of Cotia, about 20 km from São Paulo city. This factory was meant to assemble the Tamoyos and produced the armament of the Tamoyo and M41C’s. The Cotia factory was bought from Thyssen in 1984 for an undisclosed amount of money. Bernardini estimated it could produce about 50 Tamoyo 1’s per year with these two factories.

A Tamoyo hull under construction together with a second hull to the left in the background
Source: https://youtu.be/7oaZfsQYSMk

The Cotia factory was equipped with the equipment to manufacture or rebore gun barrels with a length of up to 8 meters/67 calibers in length and a diameter of at least 105 mm. Bernardini could also manufacture cannons with a diameter from 20 to 60 mm and a length of 3 meters/25 calibers in length. In addition, Bernardini had 5 CNC machines available to produce the Tamoyo, which included 3 lathes and 1 milling machine. The company also had forging and further machining equipment, was capable of testing their torsion bars, could test their guns, and could simulate equipment wear. With this equipment, Bernardini would have been able to produce most of the essential components by themselves.

The turret ring bearings.
Source: Bernardini MB-3 Tamoyo – Expedito Carlos Stephani Bastos

The quality control was supported by the CTEx, which checked the gun barrels and breeches with the help of 3D design on computers. The performance of every individual gun was logged during the manufacturing process and the certification tests.

In total, 3 Tamoyo 1s were finished, while the fourth ended up as an empty ‘shell’, with only the hull and turret being produced. Three out of four Tamoyo 1s still exist to this day and are located at various institutions of the Brazilian Army.

The Tamoyo 1 in Detail

The exact weight of the Tamoyo 1 is a bit uncertain as there is no clear document that specifically mentions the weight of the Tamoyo 1. Two weights do recur in documentation, which are 29 and 30 tonnes (32 and 33 US tons) combat loaded. Considering the prototype was designated as X-30, it is quite likely that the actual combat weight is 30 tonnes. Considering the combat weight of the Tamoyo 3 was 31 tonnes (34 US tons) and the empty weight was 29 tonnes, it is estimated that the Tamoyo 1’s empty weight would be around 28 tonnes (30.9 US tons).

The vehicle had a hull length of 6.5 meters (21.3 feet) and was 8.77 meters (28.8 feet) long with the gun pointing forward. It was 3.22 meters (10.6 feet) wide, and 2.2 meters (7.2 feet) tall to turret top and 2.5 meters (8.2 feet) tall in total. The tank was operated by a four-man crew, consisting of the commander (turret middle right), the gunner (turret front right, in front of the commander), loader (turret middle left), and the driver (front hull left).

The Tamoyo 1 (TI-2) with a 90 mm round on the fender.
Source: Bernardini MB-3 tamoyo – Expedito Carlos Stephani Bastos

Hull

The hull consisted of a welded homogenous steel construction. With the help of Adriano Santiago Garcia, a Captain in the Brazilian Army, ex-company commander on the Brazilian Leopard 1’s, and former instructor at the CIBld (Centro de Instrução de Blindados, Armor instruction center), who knew someone present at the CIBld, the writer has been able to uncover a sizable amount of the armor thickness values of the Tamoyo 1 and 2 by measuring the plate thicknesses, which up to now had not yet been published. The armor is heavier than the M41 Walker Bulldog and was meant to stop 30 mm rounds from the front, and 14.7 mm on all sides.

Tamoyo 1 hull armor
Location Thickness Angle from vertical Effective thickness
Upper front 40 mm (1.6 inch) 65-70 95-117 mm (3.75-4.6 inch)
Lower front 40 mm (1.6 inch) 45 57 mm (2.25 inch)
Sides 19 mm (0.75 inch) 0 19 mm (0.75 inch)
Rear ? 0 ?
Top 12.7 mm (0.5 inch) 90 12.7 mm (0.5 inch)

The Tamoyo had a headlight and blackout marker on both sides of the upper front hull, with a siren installed behind the right set of lights. A set of tools was installed, on one version of the Tamoyo, on the right mudguard, although on a different Tamoyo, it seems that the engineers installed something resembling a fire extinguisher on both mudguards instead. This version with the fire extinguisher mounts the tools on the right side of the upper front plate. Two lifting eyes were welded on both sides of the side upper front plates as well. In the middle of the upper front plate, in between the sets of lights, were mounting points for a set of spare tracks.

The driver was situated on the left side of the upper front plate, and had 3 vision blocks available. The driver’s hatch was a rotating hatch and the driver also had access to a hull escape hatch. An unknown amount of 90 mm ammunition was stored on the front right of the hull, next to the driver.

The Tamoyo 1 (thought to be the TI-3) with pioneer tools on the fender.
Source: Bernardini MB-3 tamoyo – Expedito Carlos Stephani Bastos

The hull side provided mounting points for the installation of side skirts, which consisted of 4 sets of skirts on each side. The early versions of the side skirts were made from steel, but would later incorporate materials like rubber and aramid fibers to improve the effectiveness against certain projectiles.

The Tamoyo has two rear lights on the rear hull plate, and a towing hook on the lower rear plate. In addition to the towing hook, two brackets were installed on this plate and on the lower front plate as well.

The rear view of the Tamoyo 1.
Source: Bernardini MB-3 tamoyo – Expedito Carlos Stephani Bastos

Mobility

The Tamoyo 1 was powered by a DSI-14 turbocharged V8 500 hp diesel engine. This liquid-cooled intercooler engine provided 500 hp and 1700 Nm (1250 ft-lbs) at 2100 rpm. This engine gave the Tamoyo a power-to-weight ratio of 16.6 hp/ton. The Tamoyo 1 used a General Motors CD-500-3 cross-drive transmission, which had 2 gears forward and 1 for reverse. Combined, this powerpack gave the Tamoyo a top speed of 67 km/h (40 m/h) on level roads. It had a fuel capacity of 700 liters (185 US gallons) which gave it a range of approximately 550 km (340 miles).

A DSI-14 engine.
Source: Authors collection

The Tamoyo used a torsion bar suspension with 6 road wheels and 3 return rollers on each side. It had 3 additional shock absorbers installed, with 2 mounted on the front two road wheels and 1 on the last road wheel. The torsion bars were previously developed by Eletrometal for the M41B program. These torsion bars were made from 300M alloy steel, which was also used for the torsion bars of the M1 Abrams. The idler wheel was mounted on the front side of the vehicle, while the drive sprockets were installed in the rear.

The Tamoyo used Brazilian copies of the T19E3 tracks produced by Novatraçao. The suspension was protected by a side skirt. The T19E3 tracks had a width of 530 mm (20.8 inch), and a ground contact length of 3.9 meters (12.8 feet). This gave the Tamoyo a ground pressure of 0.72 kg/cm2 (10 lbs/in2) and a trench crossing ability of 2.4 meters (7.9 feet). The tank had a ground clearance of 0.5 meters (1.6 feet) and could climb a 0.71 meters (2.3 feet) tall vertical slope. It could climb a slope of 31 degrees, and be operated on a side slope of about 17 degrees. The vehicle had a fording capability of 1.3 meters (4.3 feet) and could neutral steer as well.

Turret

The Tamoyo 1’s turret was armored with welded homogeneous steel plates presented at various inclinations. Turret was meant to protect the Tamoyo from frontal 30 mm and all-round 14.7 mm fire. Like with the hull armor, these armor values were uncovered with the help of the writer’s contacts in the Brazilian Army.

Tamoyo 1 Turret Armor
Location Thickness Angle from vertical Effective thickness
Gun Shield 50 mm (2 inch) 45 70 mm (2.75 inch)
Front 40 mm (1.6 inch) Presented armor angle when firing at the front:
Front top : 60
Front side: 67
Front bottom: 45Angle of the front side when firing at the side:
20
Presented relative armor when firing at the front:
Front top : 80 mm (3.15 inch)
Front side: 100 mm (4 inch)
Front bottom: 57 mm (2.25 inch)Relative armor of the front side when firing at the side:
43 mm (1.7 inch)
Sides 25 mm (1 inch) 20 27 mm (1 inch)
Rear (not including storage box) 25 mm (1 inch) 0 25 mm (1 inch)
Top 20mm (0.8 inch) 90 20 mm (0.8 inch)

The Tamoyo turret was practically shaped like a less ergonomic M41 turret because of the use of flat plates instead of an intricately shaped side plate. It had a turret ring diameter of 2 meters (6.5 feet). The turret had 2 hatches, one for the commander and gunner, and one for the loader. The hatch for the commander was located on the middle right of the turret, while the loader’s hatch was located on the middle left. The gunner was located in front of the commander and had a passive day/night periscope located in a depression of the turret top. In addition, the gunner also has access to a direct sight telescope coaxial to the main gun. The commander had 7 periscopes available, which were passive day/night sights. A laser range finder was mounted on top of the main gun.

The Tamoyo (TI-2), note the laser range finder on top of the main gun.
Source: Bernardini MB-3 Tamoyo – Expedito Carlos Stephani Bastos

A set of 4 smoke dischargers was mounted on both sides of the turret front. It also had 2 handles on each side, behind the smoke dischargers, to enable the crew to climb on the turret. A pickaxe was mounted on the right side of the turret, behind the handles. Various mounting points for boxes and tools were available on the rear side plate of the turret as well, including a lifting eye on each side on both the rear and front side plates. Finally, a storage box was mounted on the rear of the turret and a jerrycan was then mounted on both sides of the storage box.

The Tamoyo 1 at the CIBld, note the smoke launchers.
Source: CIBld

The turret top configuration seems to have undergone some minor changes during the development. 2 mounting points for antennas were located on each outer side on the rear top plate. In another turret design, the left mounting point was located just behind the loader’s hatch instead. In between the antenna mountings was the inlet for the ventilation system, as the Tamoyo had an NBC system available. In the middle were the two hatches and in front of the loader’s hatch was another component with an unknown purpose. In a single picture of the Tamoyo 2 with the 105 mm turret, this location is outfitted with a meteorological system.

The turret was armed with the BR 90 mm gun and a coaxial 12.7 mm heavy machine gun. In addition, the Commander’s station could be armed with a 7.62 mm machine gun for Anti-Air purposes. The turret had an electrical and manual turret drive and the gun had an elevation of 18 degrees and a depression of 6 degrees.

The crew positions of the Tamoyo 1
Source: https://youtu.be/7oaZfsQYSMk

Armament

The Tamoyo 1 was armed with an unstabilized Brazilian copy of the GIAT 90 mm CS Super 90 F4 gun. The Brazilian designation for this gun was ‘Can 90mm 76/90M32 BR3’. This gun was an L/52 gun that could handle a pressure of 2,100 Bar (210 MPa) and had a recoil stroke of 550 mm (21.6 inch). The gun had a recoil force of 44 kN for standard ammunition and 88 kN for APFSDS ammunition. The BR3 gun used APFSDS as its main anti-armor round due to the 52 caliber length and the incorporation of the single baffle muzzle brake, which allowed the firing of APFSDS projectiles. The BR3 would have had 5 types of ammunition available to it: canister, high explosive, high explosive anti-tank, smoke, and armor-piercing fin stabilized discarding sabot rounds.

Tamoyo Ammunition
Round Capability Effective Range Velocity Weight
APFSDS (armor piercing fin stabilized discarding sabot) Heavy
NATO Single Plate: point blank (60 degrees 150mm)
NATO Triple Plate: 600 m (65 degrees 10 mm, 25 mm, 80 mm to simulate side skirt, road wheel and side hull respectively)Medium
NATO Single Plate: 1200 m (60 degrees 130 mm)
NATO Triple Plate: 1600 m (65 degrees 10 mm, 25 mm, 60 mm)
1,650 meters (1,804 yards) 1275 m/s 2.33 kg full projectile (5.1 lbs)
HEAT (high explosive anti tank) 130 mm (5.1 inch) at 60 degrees from vertical or 350 mm (13.8 inch) flat at any range. 1,100 meters (1,200 yards) 950 m/s 3.65 kg (8 lbs)
HE (high explosive) Lethal radius of 15 meters (16 yards) 925 meters (1000 yards)
6900 meters (7545 yards) for long range HE
750 m/s (700 m/s for long range HE 5.28 kg (11.6 lbs)
Canister Training projectile 200 meters (218 yards) 750 m/s 5.28 kg (11.6 lbs)
White Phosphorous – Smoke Smoke round 925 meters (1000 yards) 750 m/s 5.4 kg (11.9 lbs)

The Tamoyo had stowage for 68 rounds of 90 mm ammunition. In addition, it was armed with a coaxial 12.7 mm machine gun and could be armed with a 7.62 mm machine gun on the commander’s station for anti-air purposes, with 500 and 3,000 rounds of ammunition respectively. The Tamoyo 1 also had 8 smoke discharges, of which four were installed on each side of the front turret. The turret had an electric and manual traverse system and the gun had an elevation and depression of 18 and -6 degrees, respectively.

The fire control system included a computer with unknown usage, most likely to better integrate the usage of day/night sights and the laser rangefinder which were used by the Tamoyo 1. This could potentially also mean a lead calculator and the integration of a meteorological system, although these were features of the Tamoyo 3, which used a much more advanced fire control system. The electric fire-control system, turret rotation and gun elevation were produced by Themag Engenharia and the Universidade de São Paulo (University of São Paulo). The Tamoyo 1 did not have a stabilized gun, while the Tamoyo 3 did incorporate this feature.

Other Systems

The electrics were powered by a main engine-driven main generator, which produced 24 volts. In addition, four 12-volt batteries were available when the main engine was stopped. The Tamoyo could be fitted with an NBC system and a heater as optional equipment. The NBC system could be mounted on the already existing ventilation system.

The vehicle used a radio which was also integrated with the M41C and the X1A2 tanks, capable of receiving the EB 11-204D and simpler frequencies. The radio also worked with AN/PRC-84 GY and AN/PRC-88 GY frequencies. The Tamoyo also had an intercom system for the entire crew which could be linked to the radio. The Tamoyo is said to have had a bilge pump as well, which might have been optional.

Variants

The MB-3 Tamoyo series had 7 variants in total. Four of these were combat variants, while the other 3 were engineering variants. Practically nothing is known about the engineering variants, as no sketches of these vehicles exist and the projects were cancelled with the shutdown of the Tamoyo program.

Tamoyo 2

The Tamoyo 2 was effectively nothing more than a Tamoyo 1 with an HMPT-500-3 transmission, which was requested to be developed by Bernardini, so that the company could provide a more modern vehicle. This transmission would allow the usage of an engine with more horsepower, as the HMPT could handle 600 hp, compared to 500 hp on the CD-500. Eventually, the Tamoyo 2 would serve as a brief testbed for the 105 mm armed turret of the Tamoyo 3, but would end up being scrapped with the end of the Tamoyo program.

The Tamoyo 2 with the Tamoyo 3 turret, note the Charrua in the rear.
Source: Bernardini MB-3 Tamoyo – Expedito Carlos Stephani Bastos

Tamoyo 3

The Tamoyo 3 was the export version of the Tamoyo program, armed with a 105 mm L7, using a 736 hp engine, a CD-850 transmission, a much more advanced fire control system, and the incorporation of composite armor. The Tamoyo 3 was a serious attempt by Bernardini to try and sell the Tamoyo to the rest of the world. It was effectively a lighter Leopard 1, with potentially better frontal armor due to the planned composite armor package, and the usage of a low recoil 105 mm gun. The Tamoyo 3 would eventually be trialed and considered by the Brazilian Army as well in 1991, but failed due to economic issues and the increasingly cheaper stream of second-hand material after the end of the Cold War.

The Tamoyo 3, note the additional composite and spaced hull armor on the hull. The Tamoyo 3 would not receive the armor package for the turret before the project was cancelled.
Source: Bernardini MB-3 tamoyo – Expedito Carlos Stephani Bastos

Tamoyo 4

The Tamoyo 4 was a plan to convert the TI-3 Tamoyo 1 to a Tamoyo 4 standard. The Tamoyo 4 was supposed to receive an MWM engine and a ZF transmission in order to fix the issues of the Tamoyo 1 which came to light during Army trials in 1988.

Since Bernardini had already considered the possibility of a ZF transmission for 900 to a 1,000 hp engine on the Tamoyo 3, it is quite likely that the Tamoyo 4 would also sport these characteristics. It is possible that the Tamoyo would have received the same MWM TDB 834 12 cylinder 1040 hp diesel engine as the EE-T1 Osório. This upgrade would have roughly doubled the hp to ton ratio from 16.6 to 33.3 (although this number would probably be limited, as it might cause issues with other components). Even the 736 hp Detroit 8V-92TA Diesel engine of the Tamoyo 3 would have raised the hp to ton ratio to a respectable 24.5. The EE-T1 Osório had about 24.2. The Detroit engine could supposedly be upgraded to higher hp as well.

In the end, Bernardini would not convert the Tamoyo 1 (TI-3) to a Tamoyo 4. The program was scrapped in 1991, while the Tamoyo (TI-3) was already taken apart before for a potential conversion but would never be reassembled.

Bulldozer, Bridge Layer, and Recovery Tamoyo

These three vehicles were planned, but never realised. The vehicles were designated as VBE Bulldozer (Viatura Blindada Especial Bulldozer, Special Armored Vehicle Bulldozer), VBE Lança Ponte (Viatura Blindada Especial Lança Ponte, Special Armored Vehicle Bulldozer Bridge Layer), and VBE Socorro (Viatura Blindada Especial Socorro, Special Armored Vehicle Recovery). These vehicles were part of the contract of 1984 with the army and were designated as P6, P7, and P8. They were supposed to all receive the DSI-14 engine and CD-500 transmission. It is very likely that the actual development of these projects would only really be initiated when the Brazilian Army started to acquire the Tamoyo 1.

An Anti-Air Tamoyo?

An AA design of the Tamoyo is suggested in the Jane’s Armour and Artillery 1985-86 book. No evidence of the existence of such a vehicle exists in Brazilian sources. The vehicle was supposed to be armed with a Bofors 40 mm L/70 but no further information was given. It might be possible that this version was confused with another Brazilian vehicle, the Charrua. Besides being an APC, the Charrua was proposed as a multiplatform vehicle, including a Bofors AA gun which was actually built. It is also likely that the AA Tamoyo might just have been mentioned as a possibility if any customer showed interest in such a vehicle, mainly for marketing reasons.

Engesa Enters the Fray

With the signing of the March 27th, 1984 contract, the development of the Tamoyo project was secured with Brazilian Army backing. In the same year, the vehicle seems to have been successfully trialed as well. But it seems that the Army’s stance regarding the Tamoyo project changed in 1986.

In 1982, Engesa broke the gentlemen’s agreement on which the Brazilian armored vehicle industry was founded. Engesa, which was supposed to focus exclusively on the development of wheeled armored vehicles, initiated the development of the EE-T1 Osório. Although the Osório was not directly developed for the Brazilian Army, Engesa still decided to use some of the initial requirements laid out by the Brazilian Army so that they could sell it to Brazil as well, but with a 105 mm gun instead. Engesa decided to increase the weight to make it more capable on the export market, but retain the 3.2 meters (10.5 feet) width.

EE-T1 P2 Osorio.
Source: http://www.lexicarbrasil.com.br/engesa/

The tank Engesa ended up with was a vehicle that outperformed the Tamoyo 1 in every aspect, except price. The Osório would outperform the later Tamoyo 3 as well in multiple aspects. In 1986, the Osório with 105 mm gun was trialed by the Brazilian Army. The Osório impressed the Brazilian Army so much that they practically seemed to have forgotten about their initial requirements of interchangeability. The Brazilian Government supposedly promised Engesa that they would buy 70 Osórios, but this would later increase to 150 or 300 Osórios according to sources. This decision effectively meant that the Army forgot about the Tamoyo project which they had initiated, which was tailor-made to Brazilian requirements, and decided to go with the Osório.

Fate

The now finished prototypes of the Tamoyo 1 were retrialed by the Brazilian Army in 1988. Considering various Tamoyos, like the Tamoyo 2 and 3, were already finished around 1986-1987, this date seems to be quite late. Flavio Bernardini noted in one of his memoirs that the Tamoyo program was ‘’Empurrada com a barriga” (English: Put under the belly)’ by the Army, which is a saying suggesting that the Army seems to have somewhat deliberately postponed the trials.

The Tamoyo (TI-2) on trials with the Charrua in 1988.
Source: Bernardini MB-3 tamoyo – Expedito Carlos Stephani Bastos

The second Tamoyo 1 (TI-2) was trialed by the Army in 1988, and subsequently rejected. The TI-2 was not fast enough and its acceleration was lacking as well. In addition, the oil filter was damaged and the gearbox was damaged due to cracking near the fixation points of the spur gears.

The Tamoyo (TI-2) during the 1988 trials.
Source: Bernardini MB-3 Tamoyo – Expedito Carlos Stephani Bastos

This rejection presented a few major issues. The first was that neither the Tamoyo 1 or the Tamoyo 2 could match the new requirements by the Army in their current configuration. Bernardini considered converting the Tamoyo 1 (TI-3) to a potential Tamoyo IV (4) version. The Tamoyo 4 would have used an MWM engine and ZF gearbox for its powerpack. This was viable since both MWM and ZF had sizable subsidiaries in Brazil at the time. The construction of a Tamoyo IV was never carried out.

By 1991, the construction of the Tamoyo 1 (TI-2), the Tamoyo 2 (TII), and the Tamoyo 1 (TI-3) had cost a little under 2.1 million US dollars (4.2 US Dollars in 2021). This suggests that a Tamoyo 1 would have cost about 700,000 US Dollars (1.4 million US Dollars in 2021) to manufacture a piece during the prototype stages. The cost per vehicle might have been less if the vehicle had reached serial production.

In 1991, the Tamoyo 3 was finally considered by the Army instead. The Tamoyo 3 would also face a brick wall, as the Army staff was split regarding the Tamoyo 3. One side was in favor of the Army sharing the costs of the evaluation of the Tamoyo 3, while the other side wanted to terminate the entire Tamoyo projects and that the costs of the evaluation should fall solely on Bernardini.

This was because the Tamoyo 3 was classified as a foreign vehicle instead of an indigenous design, since it used a lot of components that were not yet produced in Brazil. These components included the L7 cannon, automatic fire extinguishing sensors, and the fire control system among other components. The Army definitively canceled the entire Tamoyo project on July 24th, 1991 without testing the Tamoyo 3 even once. With this decision, Brazil effectively shut down any possibility of an indigenous designed and manufactured main battle tank for the Army.

Rear view of the Tamoyo 3.
Source: Author’s collection

Even worse, this decision may have sealed Bernardini’s fate as well, as the company closed its doors in 2001. If the Army had decided to acquire the Tamoyo tank, whether it would have been the Tamoyo 1, 2, 3, or 4, Bernardini would probably have lived on. The acquisition of the Tamoyo would mean much more than just buying the tanks. Maintenance support, supply of spare parts, further development and upgrade programs, and more nationally produced components would all give Bernardini a steady flow of income. More importantly, Bernardini’s survival and further development of the Tamoyo’s would have meant that the knowledge on designing tanks and all the advancements made in the field would have been retained in Brazil.

What Happened?

In a way, the Osório trials seem to have sent a signal to the Army that heavier main battle tanks, armed with guns over 90 mm, were the way forward. On top of that, it seems that the Army then decided to put their trust in the Osório program, barely considering the export version of the Tamoyo, which was built in 1987. Even worse, the Tamoyo 3 would be trialed as late as 1991, a year after the Osório project failed and a year after Engesa filed for bankruptcy. This only further solidifies the notion that the Army decided it wanted the Osório from Engesa and not the Tamoyo 1 or the Tamoyo 3 from Bernardini.

Brazil also underwent a political shift in 1985. The country transitioned from a military dictatorship towards a democracy again. With this shift, the newly reformed democracy found itself in a 10-year-long battle against hyperinflation and economic disaster. To give an idea of the inflation which the democracy inherited from the military dictatorship: inflation rose to 658.91% in between March 1984 and December 1985. The Brazilian economy would only start to recover from the rampant inflation around 1994. As a result of this crisis, the Brazilian government practically cut any acquisition of new material for the Brazilian Army.

Remaining Tamoyo 1s

Three out of four Tamoyo 1’s still exist to this day. 2 of these are completed prototypes and one is a completed shell. These prototypes are kept at various Army institutions like the CTEx and the CIBld. This is an interesting decision, as this means that none of the Tamoyo vehicles are available to the public in museums like Conde de Linhares and Militar Comando Militar Do Sul. By not presenting the Tamoyo to the public, the vehicle itself becomes much more obscure and paints a picture of the EE-T1 Osorio being the sole Main Battle Tank of Brazil.

X-30 Mock-Up

The X-30 mock-up still exists to this day and is presented at the CTEx as a monument. The CTEx is located in Guaratiba in the state of Rio de Janeiro. It seems to have had a few repaints during its time there, having received a gray paint scheme and a modern orange green scheme.

The X-30 mock-up.
Source: Bernardini MB-3 tamoyo – Expedito Carlos Stephani Bastos

MB-3 Tamoyo 1 CIBld

One of the remaining Tamoyo 1’s is preserved at the CIBld, the Brazilian Armor Instruction Centre. This Tamoyo was most likely the first Tamoyo (TI-1) to have been built. This is because the second Tamoyo 1 is preserved at the CTEx and the third Tamoyo 1 was scrapped. When this Tamoyo arrived at the CIBld is unknown, but it has been on display at the CIBld Museum since at least 2010.

This Tamoyo does not have a fire extinguisher on both sides of the front hull, and it does not have a Laser range Finder. In addition, this Tamoyo can also be recognised by the single black-out marker next to the right headlight. This particular Tamoyo was used to obtain the armor thicknesses.

Recently, this particular Tamoyo 1 was restored in driving condition by the Army, which was made public on January 22nd 2022 with a video of it slowly driving into the workshop in Alegrete, Rio Grande do Sul State. According to contacts, the vehicle is basically a shell and is only repaired to drive around. Considering Brazil had to recently restore a number of M41C tanks of Uruguay which do have the DS-14 engine, it is definitely possible that the Tamoyo retained its original engine. The vehicle is thought to have been restored so it can drive during the 200 years of independence celebration parade on the 7th of September this year. It already made an appearance during the 100 years of tanks in the Brazilian Army celebration on November 8th 2021, but it was not yet in running condition as it was presented on the trailer of a truck.

The restored Tamoyo 1.
Source: https://youtu.be/U7Pi33r1t48

MB-3 Tamoyo 1 CTEx

The second Tamoyo (TI-2) is said to be preserved at the CTEx, but no pictures of the Tamoyo 1 at the CTEx have been found. What is known, is that this Tamoyo was trialed during the 1988 trials, and subsequently displayed at the EsMB (Escola de Material Bélico, School of Military Materiel) in Rio de Janeiro. The vehicle was then stored at the IPD (Instituto de Pesquisas e Desenvolvimento, Research and Development Institute), the overarching institute of the CTEx, until 2003. At the IPD is received an inscription LTCM 1 (Laboratório de Tecnologia e Conceitos Móveis 1, Mobile Technology and Concepts Laboratory 1) with the 1 referring to the “first vehicle”. In 2003, the vehicle went to the CTEx in Rio de Janeiro.

This version is easily distinguishable by its Laser Range Finder and its two fire extinguishers. In addition, it has a black-out light next to each headlight as well.

The Tamoyo 1 at the Escola de Material Bélico.
Source: Bernardini MB-3 tamoyo – Expedito Carlos Stephani Bastos

The MB-3 Tamoyo 1 IPD

The final remaining Tamoyo 1 is the fourth Tamoyo 1 (TI-4) at the IPD. This Tamoyo is effectively nothing more than a shell. The overall steel construction of the hull and turret was completed, but did not progress any further. It is likely that this Tamoyo was cancelled in 1991, together with the cancellation of the Tamoyo project. The hull has ‘’Aqui nascem os blindados brasileiros’’ written upon it, translating to: ‘The Brazilian armored vehicles are born here’.

The vehicle was displayed as a monument in 2003 at the IPD location in Marambaia in Rio de Janeiro. IPD was absorbed by the CTEx in 2005. What happened with the Tamoyo afterwards is unknown. The Tamoyo is probably still there, but might also be lost.

The uncompleted Tamoyo 1 (TI-4) at the IPD.
Source: Bernardini MB-3 Tamoyo – Expedito Carlos Stephani Bastos

Conclusion

The Tamoyo 1 was effectively a victim of its own conception. The Brazilian Army wanted a cheap vehicle that could share as many components with the M41C and the potential Charrua as possible. The Army had agreed to the specifications of the Tamoyo 1 in 1984, but only later seemed to have realized what their requirements for the Tamoyo 1 actually entailed for the program, and what they actually wanted in their future tank. The Osório was potentially the wake-up call for the Brazilian Army and the death of the Tamoyo projects.

The Tamoyo 1 could have been a vehicle that matched the Army requirements if the Army had requested for better components from the start and not delayed its trials until 1988 only to reject the obvious. The Tamoyo 1 concept in and of itself was not a bad one in the first place. It was cheap and it would have been able to take on the TAM. If the political and economical situation of Brazil had allowed it, the Tamoyo would have been an excellent vehicle in combination with the Charruas and the M41Cs.

In the end, the failure of the Tamoyo 1 program can be boiled down to 3 main issues. The lack of strategic vision of the Army regarding requirements, Engesa breaking the gentlemen’s agreement by building the Osório, and the economic and political situation of Brazil at the time.

The Tamoyo 1 itself was not an exceptional vehicle, and it is clear that the Tamoyo 3 would have been a much better and future-proof vehicle for the Brazilian Army. The tank can be summed up as a decent and realistic medium tank that was tailor-made for the Brazilian Army’s requirements at the time, but, like almost the entire Tamoyo project, ended up being overshadowed by the much more advanced and, for Brazil, unrealistic Osório Main Battle tank.

Illustration and artist impression of the X-30 with the TAM lay-out based on the sketch used in the newspaper. An illustration by Vesp.
The X-30 illustration based on the designs seen in a video from Bernardini. An illustration by Vesp.
The X-30 design as seen in Jane’s IDR. The design incorporates many elements of previous projects from Bernardini like the X1A2 style turret and the M41B like hull. An illustration by Vesp.
The X-30 mock-up, note the plaque with Bernardini’s logo wlded on the side of the hull and the CTEx logo on teh rear side. The turret mounted a 76 mm gun with the muzzle brake of the later 90 mm BR3 gun. An illustration by Vesp.
An illustration of the Tamoyo 1 without laser rangefinder. An illustration by Vesp.
Tamoyo 1 with laser rangefinder installed on the top of teh gun. An illustration by Vesp.
Illustration of the unfinished Tamoyo 1 (TI-4) as it remains at the IPD. An illustration by Vesp.

Specifications MB-3 Tamoyo 1

Dimensions (L-W-H) 6.5 meters (21.3 feet) and 8.77 meters (28.8 feet) with the gun pointing forward, 3.22 meters (10.6 feet), 2.2 meters (7.2 feet) to turret top and 2.5 meters (8.2 feet) in total.
Total weight 28 tonnes empty, tonnes combat-loaded (30.9 US tons, 33 US tons)
Crew 4 (commander, driver, gunner, loader)
Propulsion Scania-Vabis DSI-14 turbocharged V8 500 hp diesel engine
Suspension Torsion bar
Speed (road) 67 km/h (40 m/h)
Armament 90 mm BR3
Coaxial .50 caliber MG HB M2
Anti-Air 7.62 mm mg
Armor Hull
Front (Upper Glacis) 40 mm at 65-70 degrees (1.6 inch)
Front (Lower Glacis) 40 mm at 45 degrees (1.6 inch)
Sides 19 mm at 0 degrees (0.75 inch)
Rear ?
Top 12.7 mm at 90 degrees
(0.5 inch)Turret
Front 40 mm at 60/67/45 degrees (1.6 inch)
Gun mantlet 50 mm at 45 degrees (2 inch)
Sides 25mm at 20 degrees (1 inch)
Rear 25 mm at 0 degrees (1 inch)
Top 20 mm at 90 degrees (0.8 inch)
Production 4+1 mock-up
Special thanks to Expedito Carlos Stephani Bastos, the leading expert in Brazilian vehicles, please visit his website for further reading on Brazilian vehicles: https://ecsbdefesa.com.br/, Jose Antonio Valls, an Ex-Engesa employee and expert in Engesa vehicles, Paulo Bastos, another leading expert of Brazilian Armored vehicles and the author of the book on Brazilian Stuarts and the website https://tecnodefesa.com.br, Adriano Santiago Garcia, a Captain in the Brazilian Army and ex-company commander on the Leopard 1 and ex-lecturer on the Brazilian Armored School, and Guilherme Travassus Silva, a Brazilian with whom I was able to endlessly discuss Brazilian Vehicles and who was always willing to listen to my near endless ability to talk about them.

Sources

Blindados no Brasil – Expedito Carlos Stephani Bastos
Bernardini MB-3 Tamoyo – Expedito Carlos Stephani Bastos
M-41 Walker Bulldog no Exército Brasileiro – Expedito Carlos Stephani Bastos
M-113 no Brasil – Expedito Carlos Stephani Bastos
Jane’s armour and artillery 1985-86
Brazilian Stuart – M3, M3A1, X1, X1A2 and their derivatives – Hélio Higuchi, Paulo Roberto Bastos Jr., and Reginaldo Bacchi
Moto-Peças brochure
Memoir of Flavio Bernardini
Author’s collection
Bernardini compra fábrica da Thyssen – O Globo, archived by Arquivo Ana Lagôa
The Centro de Instrução de Blindados
Tecnologia & Defesa magazines with courtesy of Bruno ”BHmaster”

With Expedito Carlos Stephani Bastos, Expert in Brazilian Armoured Vehicles
With Paulo Roberto Bastos Jr., Expert in Brazilian Armoured Vehicles
With Adriano Santiago Garcia, A Captain of the Brazilian Army and ex-company commander on the Leopard 1

Categories
Cold War Brazil CCL X1 Cold War Brazilian Armor Cold War Ecuadorian Armor

CCL X1 with 60 HVMS

Brazil/Ecuador (1980s)
Light Tank – None Built

At some point in the 1980s, Ecuador sought to upgrade its fleet of M3A1 Stuarts by modernizing them with a new gun and engine. The country entered negotiations with the Brazilian company Bernardini, which in the mid-1970s had modernized the Brazilian M3 Stuart to X1 standard. The negotiations considered a refurbished M3A1 Stuart armed with a 60 mm HVMS gun, which also armed the Chilean M4 Sherman and M24 Chaffee, and a Detroit 6V53T engine. Although the project would never leave the concept stage, the X1 60 HVMS would have had the best anti-tank capabilities of the entire X1 family. Sadly, a limited budget and an order of 32 EE-9 Cascavels by the Ecuadorian Army seem to have put an end to the project.

An Illustration of what the X1 armed with the 60 mm HVMS might have looked like. Done by David Bocquelet, edited by Brian Gaydos.

The M3A1 Stuart in Ecuador

Ecuador received the M3A1 Stuart under Lend-Lease from the United States. With World War 2 in full swing and the United States at war with the Axis, the United States sought to secure its position on the American continent. Through multiple ways, the United States would successfully influence all the American countries to either side with the Allies or stay neutral throughout the conflict. Ecuador remained neutral for the majority of World War 2, only declaring war on Germany and Japan on February 2nd, 1945.

In their attempt to secure the American continent, the United States realized that most of the equipment of the armies and infrastructure of the American countries were seriously outdated. Thus, Ecuador would receive military materiel from the United States to modernize the country’s Armed Forces for the safety of the American continent, but also as a deterrent for any country on the continent itself to join the war on the Axis side.

Ecuador received M3A1 Stuarts, M3 Scout Cars, and machine guns through Lend-Lease. In exchange, the United States could use the Galapagos Islands (off the coast of Ecuador, in the Pacific) as a base during World War 2. Ecuador received 42 M3A1 Stuarts, which arrived in 1943, after the Ecuadorian-Peruvian War of 1941. Supposedly, the M3 Stuarts were delivered to Ecuador in a non-combat ready state. If this meant that the Americans had not delivered the ammunition with the tanks or if the Americans had done something else to make them non-combat ready is unknown. The reason for the United States to supposedly deliver them in this state was to prevent a revenge attack by the Ecuadorians on Peru after their defeat during the Ecuador-Peruvian War. It is unclear how far these statements on combat readiness are true, so it is wise to take them with a grain of salt.

M3A1 Stuarts in the Ecuadorian Highlands.
Source: https://guerrade1941.blogspot.com/2018/08/los-primeros-tanques-que-llegaron-de.html

The X1

The first X1 vehicle was developed and presented at the Brazilian Independence Day Parade on September 7th 1973. The X1 was a modernization project of the M3 Stuart, carried out by the Parque Regional de Motomecanização da 2a Região Militar (PqRMM/2) (English: Regional Motomecanization Park of the 2nd Military Region), alongside Bernardini and Biselli, two Brazilian companies. The PqRMM/2 was responsible for the development of the wheeled vehicles, but also for the tracked vehicles of the Brazilian Army at the time, and were under the supervision of the Diretoria de Pesquisa e Ensino Técnico (DPET) (English: Army Research and Technical Educational Board), which coordinated the projects.

The tracked vehicles were researched and developed by a team of engineers within the Army and PqRMM/2, which were part of the Centro de Pesquisa e Desenvolvimento de Blindados (CPDB) (English: Centre for the Research and Development of Tanks). The CPDB was a research group of Army engineers which analyzed the possibilities of locally produced tanks. The first goal was to develop a new family of light tanks using the M3 Stuart as its basis.

A Brazilian M3 Stuart approved for conversion, note the A on the side meaning Aprovado (English: Approved).
Source: Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivative

The reasons for the M3 Stuart modernization were the lack of new and cheap materiel from the United States (then involved in the Vietnam War), the fact that they were the most numerous vehicles to be converted, that they were cheap to run and maintain, and their lightweight made them perfect for fighting on the difficult terrains of Brazil and their neighboring countries if needed. But the most important reason was that they were relatively easy and low risk to convert in order to gain experience to eventually build a national Brazilian tank. The M41s which Brazil had at the time were their best vehicles and much more risky to improve with the lack of experience.

After having successfully developed the first X1, a pre-series of 17 vehicles was ordered. These vehicles would, due to extensive delays, finally be delivered in 1976. The X1 was armed with a 90 mm D-921 low-pressure gun and had a Scania-Vabis DS-11 A05 CC1 6-cylinder in-line 256 hp diesel engine.

The X1.
Source: Blindados no Brasil

Bernardini and Biselli

For the construction of the X1, multiple parties and companies were involved. The two most important companies which built the X1 were Bernardini and Biselli. Both companies manufactured truck bodies and Cash-in-Transit vehicles at the time and came in contact with the Brazilian Armed Forces by manufacturing trucks for the Brazilian Marine Corps and the Army. Since both companies had some experience in the manufacture of armored vehicles, and with Bernardini being a manufacturer of safes and armored doors, they were requested by the Brazilian Army to help build the X1. Biselli quit the X1 project altogether around 1976, leaving the X1 family fully in the hands of Bernardini. In 1982, Bernardini was contracted by the Brazilian Army to develop a family of vehicles on the M3 Stuart and X1 platform. This contract would result in a family of vehicles, for example, a recovery version and a mortar carrier.

It is important to note that since Biselli quit the X1 project entirely around 1976, they had nothing to do with the X1 60 HVMS project for Ecuador. In fact, every development of the X1 family undertaken after 1976 was done by Bernardini, and the intellectual property of the vehicle was completely signed off to Bernardini by the Army.

Company/Army

Component(s)

United States The M3 and M3A1 Stuart
Biselli Hull extension, engine installation, equipment installation, and track mounting
Bernardini Turret and suspension
CSN Steel armor
Novatração Tracks
DF Vasconcelos Periscopes
Scania-Vabis Engine
PqRMM/2 Stripping of the Stuart, revision of differential and transmission, radio installation, and testing
PqRMM/3 Overhaul and selection of M3 Stuarts

An X1 for Ecuador?

Very little is known about the X1 60 HVMS for Ecuador. According to sources, the negotiations for the conversion of an unknown amount of Ecuadorian M3A1 Stuarts were carried out at some point in the 1980s. In total, Ecuador had received 42 M3A1 Stuarts, but it is unlikely that all 42 vehicles were still in service, or even fit for refurbishment at all. It is estimated that Ecuador might have been interested in the conversion of around 30 M3A1 Stuarts. This estimation is based on an order of 32 EE-9 Cascavels which might have been ordered instead of the X1 60 HVMS.

EE-9 Cascavel.
Source: https://quatrorodas.abril.com.br/testes/grandes-comparativos-urutu-ee-11-x-cascavel-ee-9/

The Ecuadorian Army asked for the refurbishment of their existing M3A1 Stuart, rearming them with the 60 mm HVMS, and remotorizing them with a Detroit 6V53T diesel engine. It is thought that the vehicle would effectively be an X1 with changes to the turret to mount the 60 mm cannon and a new engine.

It is estimated that the negotiations between Ecuador and Bernardini started at some point between 1980 and 1984, and most likely from 1982 to 1983. The reason for this is that negotiations were done in the 1980s, and Bernardini received the intellectual property and the contract to develop a family of X1 vehicles in 1982. Considering the X1 60 HVMS never got much further than the concept stage, it is very likely that the negotiations were short and might even only have happened for about a year. The reason given for the cancellation of the project was due to changes at the top of the Ecuadorian Army.

A few factors can be taken into account which might have led to the cancellation of the X1 60 HVMS project and why it is thought that the project was canceled in 1983. From 1977 to 1984, Ecuador was cutting the Army’s budget every year, reaching its lowest point in 1984. The budget of the Ecuadorian Army was somewhat limited for the acquisition of armored vehicles. In addition, 32 EE-9 Cascavels, armed with 90 mm low-pressure guns, were bought from Engesa in 1983 and delivered in 1984. It is very likely that the EE-9 Cascavel order sucked up the budget of the Ecuadorian Army, and combined with another budget cut in 1984, the Army simply did not have the money to spend on the conversion of their M3A1 Stuart tank fleet.

In addition, another case can be made for the EE-9 against the X1. The EE-9 was a brand new vehicle, while the X1 would be converted from 40-year-old vehicles. As shown by the X1 conversion in Brazil, certain issues cannot simply be fixed due to the sheer age of the refurbished vehicle. It begs the question, why spend money upgrading something old which will still retain unsolvable issues, when one could buy brand new armored cars?

An Ecuadorian M3A1 Stuart in a military parade in 2018.
Source: https://guerrade1941-blogspot-com.translate.goog/2018/08/los-primeros-tanques-que-llegaron-de.html?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=nl&_x_tr_pto=nui

The 60 HVMS gun

The 60 mm Hyper Velocity Medium Support L.70 gun was developed in 1977 by the Israeli Military Industry and the Italian company OTO-Melara to provide the infantry with a towed or Infantry Fighting Vehicle-mounted gun that could provide excellent anti-tank fire and adequate anti-infantry support. It was tested by Israel on a modified M113 with a turret and by the Italians on the VBM Freccia prototype and on a modified VCC-80 Dardo, but was not accepted into service.

The 60 HVMS on a carriage during shooting tests.
Source: pinterest.com

In fact, the 60 HVMS IMI-OTO (known in Italy as the HVMS 60/70 OTO-Melara) had excellent anti-tank performance and was able to penetrate, with its M300 APDSFS-T (Armor-Piercing Fin-Stabilized Discarding Sabot – Tracer), 120 mm of Rolled Homogeneous Armor (RHA) angled at 60° at a 2,000 m range. This was the equivalent of the frontal armor of a Soviet T-62.
In one test, it allegedly managed to penetrate the side armor of two T-62s from side to side at 2,000 m. As an example, a 105 mm APDSFS-T projectile from the Royal Ordnance L7 penetrated the same armor at the same distance. However, the 60 mm gun weighed 700 kg with a total projectile weight of only 6 kg and a length of 62 cm, while the Royal Ordnance L7 weighed 1,200 kg with projectiles weighing around 18 kg and a length of about 95 cm.

The tungsten penetrator of the APDSFS-T projectile weighed 0.87 kg with a diameter of 17 mm and a total length of 292 mm. It had a muzzle velocity of 1,620 m/s thanks to the high-pressure barrel, giving it very good accuracy up to a 2,500 m range. The HE-T (High-Explosive – Tracer) projectile weighed 7.2 kg.

A Spanish language OTO-Melara poster on the APFSDS and HE rounds of the 60 HVMS guns.
Source: Foro Militar Genera

The Theoretical X1 60 HVMS Design in Detail

The specifications and design of the X1 60 HVMS are mainly based on the existing specifications of the X1, with adjustments for the 60 HVMS gun and the Detroit 6V53T engine, to give an idea of what a 60 HVMS armed X1 might have been.

The length measurements of the X1 turned out to be incorrect in the sources. As a result, all the length values were calculated and are reasonable estimates. The X1 60 HVMS would have weighed about 17 tonnes (18.7 US tons) and would be 7.24 meters (23.7 feet) long including the gun, compared with the 6.04 meters (19.8 feet) of the normal X1, with a 5.04 meters (16.4 feet) long hull, 2.4 meters (7.9 feet) width, and 2.45 meters (8 feet) high. Although the 60 HVMS was about 300 kg heavier than the original 90 mm D-921, the difference in weight would be compensated by the Detroit engine, which was about 300 kg lighter than the original Scania engine.

It would have had a crew of four, with the driver located on the front left of the hull, the co-driver on the front right of the hull, the commander/loader on the left side of the turret, and the gunner on the right side of the turret.

Brazilian X1s of the 6th RCB.
Source: Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivative

Hull and Armor

The hull of the X1 HVMS was to be a lengthened and modified M3A1 Stuart hull. As such, the overall protection for most of the X1 HVMS’ hull remained the same as that of the M3A1. The thickness of the plates which were used to lengthen the hull is unknown. The upper front plate of the X1 HVMS would have an armor thickness of 38 mm (1.5 inch) at 17º vertical, a middle front plate of 16 mm (0.6 inch) at 69º, and a lower front plate of 44 mm (1.7 inch) at 23º. Its sides were most likely about 25 mm (1 inch) thick. The rear armor and the lengthened parts of the side are unknown. Considering the original Stuart had 25 mm (1 inch) thickness on the sides and rear, it would not be unreasonable to assume that the lengthened structure was about 25 mm (1 inch) thick as well. The top plate would have been 13 mm (0.5 inch) thick and the floor plate would have gradually decreased in thickness from 13 mm at the front to 10 mm (0.5 to 0.4 inch) in the rear (although the thickness for the lengthened structure is unknown).

The rest of the X1 HVMS would have a very similar layout as the Stuart, like the original X1. The X1 had two headlights, one on each side of the front mudguards, two towing hooks on the front hull, and a .30 caliber hull machine gun on the right side. The driver had a two-piece hatch, while the co-driver had a single-piece hatch in the production versions of the X1. Depending on its variant, the X1 would either have a curved or angled rear plate, with the curved rear plate coming from the M3A1 Stuart.

Brazilian X1 with a curved rear plate.
Source: https://wwiiafterwwii.files.wordpress.com/2020/09/x1preservedtanks.jpg?w=809

Mobility

The X1 HVMS was to be powered by a Detroit 6V53T V6 turbocharged 260 hp diesel engine. This engine produced 260 hp at 2,200 rpm, giving the vehicle a horsepower per tonne ratio of 15.3. It would have used the same, but revised and using some locally produced components, 5 speed and 1 reverse transmission and differential as the original Stuarts. The X1 had a top speed of 55 km/h (34 mph) on roads and an operational range of 520 kilometers (323 miles).

The X1 HVMS would have used a copied and slightly altered VVS suspension system from the 18-ton M4 artillery tractor. It had 4 road wheels divided over two bogies, with 2 bogies per track, two return rollers on each side, a drive sprocket in the front, and an idler wheel on the rear. The 18-ton M4 suspension gave the X1 HVMS a ground pressure of 0.59 kg/cm2 (8.4 psi). The X1 had an on-ground track length of about 3.22 meters (10.6 feet) and could cross a trench of 1.2 meters (3.9 feet).

Turret

It is thought that the X1 HVMS would most likely have kept the BT-90A1 turret of the X1, although adjusted for the 60 mm HVMS gun. Considering the HVMS has a recoil weight of 500 kg compared to 200 kg for the D-921, the trunion of the turret would have most likely needed reinforcement. The recoil length of the HMVS, however, was shorter at 270 mm compared to 550 for the 90 mm.

The production versions of the X1 used the BT-90A1 turret, which used periscopes from Vasconcelos S/A. This company had previously provided periscopes for the VBB-1 4 x 4 wheeled vehicle. The turret was armored with 25 mm (1 inch) thick steel plates at various angles to protect it from .50 caliber machine gun fire at 200 meters (218 yards). It is suggested that the overall turret layout and the internal turret construction and components were more or less copied from the French H-90 turret. It had the exact same turret ring and its overall shape seems to match the H-90. In addition, in the first BT-90 turret, a lot of equipment was carried over from the H-90, such as the periscopes.

BT-90A1 turret front interior.
Source: Caiafa Master – https://youtu.be/p1lUgv5eMsg

The BT-90A1 turret had a mount for a .50 machine gun on the left side, in front of the commander’s cupola. The commander’s cupola’s structure was slightly raised from the turret top to provide the commander with a 360º view. The antenna of the radio sets was located behind the gunner’s cupola on the right side of the turret. In addition, the X1 could mount two smoke dischargers on both sides of the turret rear, although these seem to not have always been mounted on the vehicles.

BT-90A1 rear interior.
Source: Caiafa Master – https://youtu.be/p1lUgv5eMsg

Armament

The X1 60 HMVS was to be armed with the 60 mm HVMS gun. The HVMS gun would provide a couple of advantages over the 90 mm D-921 of the X1. Most notable was the heavily increased initial muzzle velocity of the APDSFS round for the HVMS gun of 1,620 m/s compared to 865 m/s for the HEAT round of the 90 mm gun of the X1. The APFSDS round would also retain its velocity much better due to better aerodynamic properties compared to the 90 mm round. The increased muzzle velocity combined with the small sub-caliber round would make the HVMS gun much more effective in the anti-tank role than the D-921 gun.

Since the D-921 gun fired its round with a much slower muzzle velocity, it became much less accurate as well. Not only did the gun need to fire the HEAT round at an angle to compensate for the lack of velocity, the gunner would also have to take the slower travel time into account while leading for a target. Overall, the longer the travel time of the round, the less accurate it gets.

Performance-wise, the HEAT round of the D-921 and the APFSDS round of the 60 mm HVMS were about equal in terms of penetration at 2,000 meters, at around 120 mm at 60º. However, the D-921 only had an effective range of 1,500 meters, meaning that the 60 mm HVMS would not only be more accurate, but also more effective at close ranges. All in all, the 60 mm HVMS was a much better anti-tank gun than the D-921, but compromised with a much lighter HE shell of 2.9 kg compared to 5.28 kg for the D-921.

Round

Capability

Effective range

Velocity

APFSDS-T (Armor-Piercing Fin-Stabilized Discarding Sabot – Tracer) 120 mm at 60 degrees from vertical at 2000 meters. 2,500 meters 1,620 m/s
HE (High Explosive)

It is unknown how many 60 mm rounds the X1 HVMS could have stored. The standard X1 stowed 18 rounds in the turret and another 10 in the hull. The X1 HVMS could probably have stored a little more. In addition to the 90 mm, the X1 mounted a turret top .50 caliber machine gun for the commander, a coaxial .30 machine gun, and a .30 machine gun for the co-driver in the hull.

An APFSDS round for the 60 mm gun.
Source: cartridgecollectors.org

Conclusion

Although the X1 60 HVMS was a very interesting project and would have greatly improved the anti-tank capability of the M3A1 Stuarts and the X1 family, it seems that the project lost to the EE-9 Cascavel. The basis of the X1 60 HVMS was 40 years old, which would make some issues unfixable due to the longevity of the platform. Combined with the decreasing budget of the Ecuadorian Army, the X1 60 HVMS was simply not meant to be. There was no money, the basis was too old, and the EE-9 was bought instead, dooming the project to obscurity.

An Ecuadorian EE-9 M7 Cascavel.
Source: https://www.infodefensa.com/texto-diario/mostrar/3074889/ecuador-mejorados-ee-9-cascavel

Illustrations

An Illustration of what the X1 armed with the 60 mm HVMS might have looked like. Done by David Bocquelet, edited by Brian Gaydos.

Specifications CCL X1

Dimensions (L-W-H) 7.24 meters (23.7 feet) long including the gun x 2.4 meters (7.9 feet) x 2.45 meters (8 feet) tall
Total weight 17 tonnes (18.7 US tons)
Crew 4 (Driver, Co-driver, Commander-Loader, Gunner)
Propulsion Detroit 6V53T V6 turbocharged 260 hp diesel engine
Suspension Bogie suspension
Speed (road) 55 kph (34 mph)
Operational range 520 km (323 miles)
Armament 60 mm HVMS gun
.50 machine gun
.30 coaxial machine gun
.30 hull machine gun
Armor

Hull

Front (Upper Glacis) 38 mm (1.5 inch) at 17 degrees
Front (Middle Glacis) 16 mm (0.6 inch) at 69 degrees
Front (Lower Glacis) 44 mm (1.7 inch) at 23 degrees
Sides (guess) 25 mm (1 inch)
Rear (guess) 25 mm (1 inch)
Top 13 mm (0.5 inch)
Floor 13 to 10 mm (0.5 to 0.4 inch)

Turret

25 mm (1 inch) allround

Production None (concept only)

Special thanks to Expedito Carlos Stephani Bastos, the leading expert in Brazilian vehicles, please visit his website for further reading on Brazilian vehicles: https://ecsbdefesa.com.br/, Jose Antonio Valls, an Ex-Engesa employee and expert in Engesa vehicles, Paulo Bastos, another leading expert of Brazilian Armored vehicles and the author of the book on Brazilian Stuarts and the website https://tecnodefesa.com.br, Adriano Santiago Garcia, a Captain in the Brazilian Army and ex-company commander on the Leopard 1 and ex-lecturer on the Brazilian Armored School, and Guilherme Travassus Silva, a Brazilian with whom I was able to endlessly discuss Brazilian Vehicles and who was always willing to listen to my near endless ability to talk about them.

Sources

Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivatives – Hélio Higuchi, Paulo Roberto Bastos Jr., Reginaldo Bacchi
Blindados no Brasil – Expedito Carlos Stephani Bastos
http://www.lexicarbrasil.com.br/
Personal correspondence with Expedito Carlos Stephani Bastos
Personal correspondence with Paulo Roberto Bastos Jr.
Engesa brochures and manuals
Cockerill brochures
TM 9-785 18-Ton High Speed Tractors M4, M4A1, M4C, and M4A1C – US Army April 1952.
Stuart: A history of the American Light Tank, Volume 1 – R.P. Hunnicutt
Tecnologia Militar Brasileira magazine
https://guerrade1941.blogspot.com/2018/08/los-primeros-tanques-que-llegaron-de.html
Anuario – Academia de Historia Militar Number 33, 2019

Categories
Cold War Brazil CCL X1 Cold War Brazilian Armor

CCL X1A1 Carcará

Brazil (1976)
Light Tank – 1 Prototype Built

At the beginning of the 1970s, the Brazilian Army started developing armored vehicles, starting with wheeled vehicles. After having successfully developed the prototype concepts which would become the EE-9 Cascavel and the EE-11 Urutu, the Brazilians looked to tracked vehicles. Like the previous wheeled vehicle projects, the engineers started small. They began by remotorizing readily available M3 Stuarts, and then started developing the vehicle that is known as the X1 light tank. The X1 was a modernization of the Stuart, which was armed with a low-pressure 90 mm gun, and would be developed into an entire family of vehicles.

One of these vehicles was a planned improvement of the X1 tank. The X1 had some limitations because of the components it used and some basic concepts. To fix these issues, the Brazilian Army engineers started the development of the X1A1, which was effectively a lengthened X1 with improved components.

The X1A1 in 1976.
Source: https://wwiiafterwwii.wordpress.com/2020/10/18/strange-stuarts-of-brazil/

The X1 Project

In 1973, the first X1 vehicle was developed and presented at the Brazilian Independence Day Parade on September 7 of the same year. The X1 was a modernization project of the M3 Stuart, carried out by the Parque Regional de Motomecanização da 2a Região Militar (PqRMM/2) (English: Regional Motomecanization Park of the 2nd Military Region), together with Bernardini and Biselli, two Brazilian companies. The PqRMM/2 was responsible for the development of the wheeled vehicles, but also for the tracked vehicles of the Brazilian Army at the time, and were under the supervision of the Diretoria de Pesquisa e Ensino Técnico (DPET) (English: Army Research and Technical Educational Board), which coordinated the projects.

The tracked vehicles were researched and developed by a team of engineers within the Army and PqRMM/2, which were part of the Centro de Pesquisa e Desenvolvimento de Blindados (CPDB) (English: Centre for the Research and Development of Tanks). The CPDB was a study group of Army engineers which analyzed the possibilities of locally produced tanks. The first goal was to develop a new family of light tanks using the M3 Stuart as its basis.

The reasons for the M3 Stuart modernization were the lack of new and cheap materiel from the United States (then involved in the Vietnam War), the fact that they were the most numerous vehicles to be converted, they were cheap to run and maintain, and their lightweight made them perfect for fighting on the difficult terrains of Brazil and their neighboring countries if needed. But the most important reason was that they were relatively easy and low risk to convert in order to gain experience to eventually build a national Brazilian tank. The M41s which Brazil had at the time were their best vehicles and much more risky to improve with the lack of experience.

After having successfully developed the first X1, a pre-series of 17 vehicles was ordered. These vehicles would, due to extensive delays, finally be delivered in 1976. At this point, various flaws of the X1 were already found and the X1A1 already developed.

The X1.
Source: Blindados no Brasil

Bernardini and Biselli

For the construction of the X1A1, multiple parties and companies were involved. The most important two companies which built the X1A1 were Bernardini and Biselli. Both companies manufactured truck bodies and value transport vehicles at the time, and came in contact with the Brazilian Armed Forces by manufacturing trucks for the Brazilian Marine Corps and the Army. Since both companies had some experience in the manufacture of armored vehicles, and with Bernardini being a manufacturer of safes and armored doors, they were requested by the Brazilian Army to help build the X1. After the X1 was successfully developed, Bernardini and Biselli started developing the X1A1 together with the PqRMM/2 and the CPDB engineers. Although Biselli would never fully commit to the project, Bernardini would commit and eventually become the tank counterpart to Engesa’s wheeled vehicles.

Company/Army Component(s)
United States The M3A1 Stuart
Biselli Most likely: Hull extension, engine installation, equipment installation, and track mounting
Bernardini Most likely: Turret and suspension
CSN Steel armor
Novatração Tracks
DF Vasconcelos Periscopes
Scania-Vabis Engine

Development

The exact starting point for the development of the X1A1 is unknown. Considering the first X1 was still extensively tested in 1974, and the X1A1 was first presented at the Independence Day Parade of 1976, it can be estimated that the vehicle might have been developed anywhere between 1975 and September 1976. Considering that the first X1 was developed and built in a span of just 2 months, it is not unlikely that the X1A1 started its development in early 1976.

The development of the X1A1 was meant to fix some issues identified on the X1. The most notable were the replacement of the massive idler wheel from the 18-ton M4 Artillery Tractor suspension, which had replaced the original M3 Stuart suspension on the X1, and the replacement of the M3 Stuart transmission with the transmission from the 18-ton M4.

The large ground touching idler wheel of the 18-ton M4, was a perfect solution to provide more track length while not needing a particularly large hull. The downside of these types of idlers is that they are made for relatively slow-moving vehicles, which the X1, at 55 km/h, was not. The high speed and weight of the X1 caused premature wear on the swing arms of the idler, which would eventually start to crack.

The X1. Note the on-ground track idler attached to a set of swing arms, and the two sets of bogies.
Source: https://wwiiafterwwii.files.wordpress.com/2020/09/x1preservedtanks.jpg?w=809

To fix this issue, it was decided to replace the ground-touching idler of the 18-ton M4 with the idler of the M4 Sherman. This meant that the idler would not provide the on-ground track length which was needed for the vehicle. As a result, an additional bogie was added, totaling three sets of bogies per side. In essence, a sort of 18-ton M4 Tractor/M4 Sherman hybrid suspension was created.

Because of the way a bogie has to be installed, the hull of the X1A1 had to be significantly lengthened compared to the M3 Stuart. The hull was lengthened by about 0.8 meters to accommodate the newly designed suspension and thus the required on-ground track length. The on-ground track length of the X1 was about 3.22 meters (10.6 foot), while the X1A1 was about 3.66 meters (12 foot) in comparison.

The 18-ton M4 Tractor/M4 Sherman hybrid suspension. Note the M4 Sherman idler and the three sets of bogies.
Source: http://www.primeportal.net/tanks/gino_marcomini/x1a2_carcara/

The lengthened hull brought a few extra advantages. A larger fuel tank was installed and more ammunition could be stored in the hull compared to the X1, increasing from 10 to 34 90 mm rounds.

The lengthened hull also enabled the engineers to design a larger turret bustle for the original BT-90A1 turret. In contrast to the initial turret of the X1, which was supposedly covered with 25 mm (1 inch) thick armor, the X1A1 turret would have 25 mm armor (1 inch) on the front and 12.5 (0.5 inch) mm armor on the rear parts of the turret. The extension of the turret bustle meant that an extra radio could be installed in addition to 24 90 mm rounds, compared to 10 rounds in the X1 turret.

All these changes caused the vehicle to increase in weight, which meant that larger brakes had to be installed to compensate for this increase. The X1A1 was finished somewhere before the Independence Day Parade of September 7th 1976. The vehicle would gain its nickname during a promotional film, when General Pedro Cordeiro de Mello, head of the PqRMM/2 and also the one who named the X1, named it Carcará, after an indigenous crested bird. It would be officially designated as Viatura Blindada de Combate – Carro de Combate MB-1A (VBC-CC MB-1A), (English: Armored Fighting Vehicle – Combat Car MB-1A, with MB meaning Medio Bernardini or Medium Bernardini). Considering the X1’s similar designations, it would most likely have also been referred to as Carro de Combate Leve X1A1 Carcará (CCL X1A1 Carcará), (English: Light Combat Car X1 Carcará), but this is more of an educated guess that cannot be actually confirmed. The X1A1 used EB11-376 as its vehicle number in the Brazilian Army, most likely being converted from an M3A1 Stuart which bore the same number and was owned by the CPDB.

A Carcará hawk.
Source: https://www.britannica.com/animal/caracara

Somewhere around this time, Biselli left the X1 family projects. Although the exact reasons are unclear, there are some statements that Biselli had some internal struggles, and Bernardini demanded more recognition for their efforts in the X1 project. In addition, it is also suggested that Biselli saw limitations in the defense industry and decided that focussing on the civilian industry was more profitable, while taking on more of a support role in the defense industry. With Biselli quitting the project, all tank development would be taken on by Bernardini, which would one day build the MB-3 Tamoyo main battle tanks.

MB-3 Tamoyo 3.
Source: Bernardini MB-3 Tamoyo

The X1A1 in Detail

Multiple characteristics are presented incorrectly in the sources. As a result, all the length values were calculated with ratios and are reasonable estimates. Most of the other values are rough estimates. The X1A1 weighed somewhere between 17 and 19 tonnes (18.7 to 21 US tons) and was 7.04 meters (23.1 feet) long including the gun, had a hull of about 6.04 meters (19.8 feet), 2.4 meters (7.9 feet) wide, and 2.45 meters (8 feet) tall. It had a crew of four, with the driver located on the front left of the hull, the co-driver on the front right of the hull, the commander/loader on the left side of the turret, and the gunner on the right side of the turret.

X1A1 on the left, next to an X1. Note the additional bogie and the lengthened turret.
Source: Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivatives

Hull and Armor

The hull of the X1A1 was a lengthened and modified M3A1 Stuart hull, recognizable by the curved rear plate. As such, the overall protection for most of the X1A1’s hull remained the same as the M3. The thickness of the plates which were used to lengthen the hull is unknown. The upper front plate of the X1A1 had an armor thickness of 38 mm (1.5 inch) at 17º vertical, a middle front plate of 16 mm (0.6 inch) at 69º, and a lower front plate of 44 mm (1.7 inch) at 23º. Its sides were most likely about 25 mm (1 inch) thick. The rear armor and the lengthened parts of the side are unknown. Considering the original Stuart had 25 mm (1 inch) thickness on the sides and rear, it would not be unreasonable to assume that the lengthened structure is about 25 mm (1 inch) thick as well. The top plate would have been 13 mm (0.5 inch) thick and the floor plate would have gradually decreased in thickness from 13 mm at the front to 10 mm (0.5 to 0.4 inch) in the rear (although the thickness for the lengthened structure is unknown).

The rest of the X1A1 had a very similar layout as the Stuart. It had two headlights, one on each side of the front mudguards, two towing hooks on the front hull, and a .30 caliber hull machine gun on the right side. The driver had a two-piece hatch, while the co-driver had a single-piece hatch.

The X1A1.
Source: Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivatives

Mobility

The X1A1 was powered by a Scania-Vabis DS-11 A05 CC1 6-cylinder in-line 256 hp diesel engine. A difference with the X1 is that the X1A1 uses more drive components from the 18-ton M4 instead of those of the M3 Stuart. This meant that the X1A1 had the same 3-speed transmission as the 18-ton M4. Another interesting detail is that the steering levers of the vehicle were mounted on the top of the hull instead of the bottom. The X1A1 had a top speed of potentially 50 to 55 km/h (31 to 34 mph) on roads and an operational range of 520 km (323 miles).

The X1A1 used a copied and altered VVS suspension system of the 18-ton M4 artillery tractor. It had 6 road wheels divided over three bogies, with 3 bogies per track, 3 return rollers on each side, a drive sprocket in the front and an M4 Sherman idler wheel on the rear. The newly designed 18-ton M4 Tractor/M4 Sherman hybrid suspension gave the X1A1 a ground pressure of 0.55 kg/cm2 (7.8 psi). The X1A1 had an on ground track length of about 3.66 meters (12 foot) and could cross a trench of 6.1 meters (4.9 foot).

Turret

The X1A1 turrets were practically the exact same turrets as the X1’s BT-90A1 turrets, except for the extended turret bustle. The front turret was armored with 25 mm (1 inch) thick steel plates at various angles to protect it from .50 caliber machine gun fire at 200 m (218 yards). The rear parts of the turret were armored with 12.5 mm (0.5 inch) thick steel plates. It is suggested that the overall turret layout and the internal turret construction and components were more or less copied from the French H-90 turret. It had the exact same turret ring and its overall shape seems to match the H-90. In addition, in the first BT-90 turret of the X1, a lot of equipment was carried over from the H-90, like the periscopes.

The X1A1 turret had a mount for a .50 cal machine gun on the left side of the turret, in front of the commander’s cupola. The commander’s cupola’s structure was slightly raised from the turret top to provide the commander with a 360º view. The antenna of the radio sets was located behind the gunner’s cupola on the right side of the turret. Placement-wise, there were a few differences with the original X1 turret. Spare tracks were mounted on the turret bustle sides, which might hint that the turret bustle sides are 12.5 mm thick as it uses additional tracks as armor. This placement of the spare tracks meant that the smoke dischargers were moved to the front of the turret, in a set of 3 dischargers on each side. A small light was also installed on the turret side of the commander’s cupola.

X1A1 during trials.
Source: Blindados no Brasil

Armament

The X1A1 was armed with the 90 mm D-921 low-pressure gun. The low-pressure gun allowed vehicles like the X1, but also the 5 tonne AML-90, to mount a gun on light platforms with significant armor penetration capabilities.

The trade-off with these types of guns is that Kinetic AP or APFSDS rounds are not really worth it from a penetration point of view compared to the HEAT rounds these guns fired. A 90 mm APFSDS round for the later Cockerill guns would penetrate 100 mm (3.9 inch) of armor at 60º from vertical at a range of 1,000 m (1,090 yards), compared to 130 mm (5.1 inch) at 60º for HEAT at any range. The D-921 did not even have AP rounds available for this reason.

The 90 mm D-921 gun.
Source: https://forum.warthunder.com/index.php?/topic/393523-panhard-aml-90-linx/

The X1A1 had access to HEAT, High Explosive Squash Head (HESH), and High Explosive rounds. The HEAT round was meant for anti-armor purposes and was the X1A1’s anti-tank round. The HESH round was mainly meant for bunkers, walls, and light vehicles, and not as ‘anti-armor’ ammunition. The HE round was used as a general-purpose support round. Another downside of these low-pressure guns was their limited combat range and decreased velocity. This meant that the gun became much less accurate at longer ranges compared to high-velocity guns, which could also outrange the low-pressure 90 mm guns.

Round

Capability

Effective range

Velocity

HEAT (High Explosive Anti Tank) 320 mm flat at any range. 1,500 meters (1,640 yards) 750 m/s
HE (High Explosive) Lethal radius of 15 meters (16 yards) 650 m/s

The X1A1 stowed 24 rounds in the turret, and an additional 34 rounds in the hull, for a total of 58 rounds of 90 mm ammunition. In addition to the 90 mm, the X1A1 mounted a turret top .50 caliber machine gun for the commander, a .30 coaxial machine gun, and a .30 machine gun for the co-driver in the hull.

Fate

In the end, after all the improvements done on the X1A1 in an attempt to fix the mistakes of the X1, the Brazilian engineers accidentally ‘broke’ the vehicle even more. Although most of the issues with the individual components were solved, some issues were unfixable, as they resulted from the simple fact that the basis of the X1A1 was a 30-year-old M3A1 Stuart. The torque converter also provided problems throughout the X1 family, as the quality of diesel used by the Brazilians was quite poor. This resulted in premature wear of the components.

The X1A1 during trials.
Source: Blindados no Brasil

The biggest issue though, and what really caused the engineers to break the vehicle more than they fixed the X1, was that the length to width ratio was off. The X1A1 was too long and too narrow. This made the X1A1 a very sluggish and hard to steer vehicle, which worsened the longer the vehicle was operated. An anecdote describes the steering issues of the X1A1. The X1A1 was the only vehicle of the X1 family to have its steering levers attached to the roof of the hull instead of the floor. In an instance, a driver had to apply so much force in order to turn, that he pulled out the lever from its fixation point. This problem was only worsened because the X1A1 also suffered from an increasingly problematic differential, on top of the length to width ratio of the vehicle.

The engineers analyzed how they could potentially fix these issues, but they quickly discovered it was not worth the resources. They would have had to widen each M3 Stuart to achieve the needed length to width ratio, and also adjust most of the components to fit in this new configuration. In addition, the fixed X1A1s would still suffer from the same issues as the other X1s, because the same old Stuart was still the base vehicle. As a result, it was decided that it was easier to start developing Brazil’s first and practically only serially produced tank in Brazilian service, which was completely designed in Brazil. This new vehicle became the X1A2 and would see limited service in the Brazilian Army, as the project was fairly quickly canceled for the much more promising M41 modernization projects.

The only produced prototype now serves as a gate guardian at the PqRMnt/1 in Rio de Janeiro.

The X1A1 as the PqRMnt/1in Rio de Janeiro.
Source: Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivatives

Conclusion

For all intents and purposes, the X1A1 itself was a failure. The Brazilian engineers literally found the limits to what one could do with an M3 Stuart. Even though the X1 program was a sort of trial and error program to gain experience, the X1A1 was a step too far in the modernization of obsolete vehicles. The significant mobility issues and the continued usage and wear of old M3 Stuart components would cause the X1A1 to be a very immobile vehicle.

It was not a complete failure though. The 18-ton M4 Tractor/M4 Sherman hybrid suspension would be carried over from the X1A1 to the X1A2, and the lengthened turret would also be carried over for at least the first X1A2 prototype. The X1A1 would, due to the significant problems, be the only vehicle in the X1 family that was lengthened this way with the M3/M3A1 Stuart as its basis. The X1A1 functioned more as a technology bridge between the X1 and the X1A2 than anything else. It was a useful unsuccessful project.

The X1A1 Light Tank.

Specifications CCL X1A2

Dimensions (L-W-H) 7.06 meters (23.2 feet) long including the gun x 2.4 meters (7.9 feet) x 2.45 meters (8 feet) tall
Total weight 17 to 20 tonnes (18.7 to 22 US tons)
Crew 4 (Driver, Co-driver, Commander-Loader, Gunner)
Propulsion Scania-Vabis DS-11 A05 CC1 6-cylinder in-line 256 hp diesel engine
Suspension Bogie suspension
Speed (road) 50-55 kph (31-34 mph)
Operational range 520 km (323 miles)
Armament 90 mm D-921 low-pressure gun
.50 machine gun
.30 coaxial machine gun
.30 hull machine gun
Armor

Hull

Front (Upper Glacis) 38 mm (1.5 inch) at 17º
Front (Middle Glacis) 16 mm (0.6 inch) at 69º
Front (Lower Glacis) 44 mm (1.7 inch) at 23º
Sides (guess) 25 mm (1 inch)
Rear (guess) 25 mm (1 inch)
Top 13 mm (0.5 inch)
Floor 13 to 10 mm (0.5 to 0.4 inch)

Turret

25 mm (1 inch) frontal part
12.5 mm (0.5 inch) rear part

Production 1 Prototype

Special thanks to Expedito Carlos Stephani Bastos, the leading expert in Brazilian vehicles, please visit his website for further reading on Brazilian vehicles: https://ecsbdefesa.com.br/, Jose Antonio Valls, an Ex-Engesa employee and expert in Engesa vehicles, Paulo Bastos, another leading expert of Brazilian Armored vehicles and the author of the book on Brazilian Stuarts and the website https://tecnodefesa.com.br, Adriano Santiago Garcia, a Captain in the Brazilian Army and ex-company commander on the Leopard 1 and ex-lecturer on the Brazilian Armored School, and Guilherme Travassus Silva, a Brazilian with whom I was able to endlessly discuss Brazilian Vehicles and who was always willing to listen to my near endless ability to talk about them.

Sources

Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivatives – Hélio Higuchi, Paulo Roberto Bastos Jr., Reginaldo Bacchi
Blindados no Brasil – Expedito Carlos Stephani Bastos
http://www.lexicarbrasil.com.br/
Personal correspondence with Expedito Carlos Stephani Bastos
Personal correspondence with Paulo Roberto Bastos Jr.
Engesa brochures and manuals
Cockerill brochures
TM 9-785 18-Ton High Speed Tractors M4, M4A1, M4C, and M4A1C – US Army April 1952.
Stuart: A history of the American Light Tank, Volume 1 – R.P. Hunnicutt
Tecnologia Militar Brasileira magazine

Categories
Cold War Brazil EE-9 Cascavel Cold War Brazilian Armor

CRM and EE-9 M2 37 mm

Brazil (1971-1975/1976)
Reconnaissance Vehicle – At Least 9 Built + 102 Ordered

Up until 1967, Brazil was dependent on foreign countries for armored vehicles. Throughout and in the aftermath of World War 2, Brazil received large numbers of cheap surplus armored vehicles from the United States, including the M3 Stuart and the M4 Sherman, as it had entered the war on the Allied’s side in 1942. In fact, Brazil had not undertaken any tank design since 1932, and those had only been conversions of tractors and cars into armored vehicles during the revolutions of 1924, 1930, and 1932.

Between 1932 and 1958, the Brazilian Armed Forces created a solid basis of technical institutes from which it could educate technical and research personnel. In turn, these helped the Brazilian automotive industry in developing its own automotive parts and helped in opening laboratories for the manufacturers. In 1967, Brazil set up a plan for the country to become more militarily self-sustaining. The flow of US material had decreased because of its entanglement in the Vietnam War and, after a study, Brazil recognised external dependence on arms suppliers as a serious problem for its political position in South America.

The plan to solve this became the start of the Brazilian defense industry. After the Army had remotorised various vehicles, such as the M8 Greyhound, with diesel engines, they set off developing Brazil’s first wheeled vehicle with serial production in mind. The 4 x 4 VBB-1 which resulted from this development was everything but revolutionary. It did provide the needed experience and confidence for the Brazilian engineers though. With the rejection of the VBB-1 because the Army wanted a 6 x 6 vehicle, Brazilian engineers started developing the vehicle which would become the most successful armored fighting vehicle Brazil ever developed: the EE-9 Cascavel.

An EE-9 M2 with a 37 mm gun.
Source: https://webkits.hoop.la/topic/procurando-imagens-do-ee-9-cascavel-magro?reply=471368445555157354

Genesis

The story of why the EE-9 Cascavel (English: Rattlesnake) was developed can be traced back to the Second World War. Brazil sent an expeditionary force, known as the Smoking Snakes, to fight in Italy alongside the Allies. During the Italian Campaign, the Brazilian forces were armed with US M8 Greyhounds. The M8 Greyhound turned into the most loved vehicle by the Brazilian soldiers, and after WW2, this love would remain embedded in the Brazilian Army. The positive experience with the M8 during WW2 caused it to be the most impactful vehicle for the Brazilian development of armored vehicles. As a result, most of the wheeled vehicles and the wheeled vehicle program can trace back their roots to the M8 Greyhound during the Italian campaign. This love for the M8 resulted in the development of Brazil’s EE-9 Cascavel some 25 years after WW2, a heavily improved and altered concept of the M8 Greyhound.

Soldiers of the Brazilian Força Expedicionária Brasileira (FEB) in Italy.
Source: https://tecnodefesa.com.br/75-anos-do-dia-da-vitoria-ordem-do-dia/

Although Brazil enjoyed its diplomatic relations with the United States well into the 1970s, the first steps to break free from the United States, from an Army materiel point of view, started in 1967. The United States got increasingly involved with the Vietnam War and, as a result, could not supply Brazil with the cheap equipment it once did. This severely undermined Brazil’s political power in South America. Not only were they seen as a United States proxy state, now with the military ties effectively cut loose, Brazil had no way to fight a prolonged war with its neighbors.

The Brazilian Army conducted a study regarding its dependency on the United States in 1967, which resulted in the Triennial Plan 68/70. The Brazilian Army recognized its external dependence as a serious issue and advocated for the encouragement of R&D (Research and Development) of locally designed and produced materiel. This would in turn cause the Diretoria General de Material Bélico (DGMB) (English: General Directorate of War Material) to further study armored equipment from all over the globe, with 4 x 4 and 6 x 6 vehicles in particular. By studying the wheeled vehicles of the United States, the United Kingdom, Belgium, Switzerland, the Netherlands, and Italy at the time, the DGMB called for the intensive adoption of wheeled armored vehicles. These vehicles required a relatively modest investment for their development, and as such, were more viable to develop instead of importing them. The study proposed the creation and adoption of a vehicle like the M8 Greyhound, but simpler.

PqRMM/2

From this point onward, the Parque Regional de Motomecanização da 2a Região Militar (PqRMM/2) (English: Regional Motomecanization Park of the 2nd Military Region) started taking the first steps towards developing armored vehicles for the Army. The PqRMM/2 was a group of army automotive engineers gathered to study, develop and produce armored vehicles in Brazil, and were the pioneers of the Brazilian defense industry.

The first step the PqRMM/2 team undertook was the motorization of Brazil’s M8 Greyhounds and M2 half-tracks with locally produced diesel engines. With the success of these projects, they continued to the next phase of the program and developed Brazil’s first wheeled vehicle with serial production in mind. The Viatura Blindada Brasileira 1 (VBB-1) (English: Armored Car of Brazil 1) was a 4 x 4 vehicle meant for reconnaissance and mounted a copy of the M8 Greyhound turret. The VBB-1’s concept came from the Belgian FN 4RM 62F, but its design was based on the M8 Greyhound. Although the VBB-1 seems to have successfully performed its tests when the vehicle was presented to the Army in 1969, the Army did not want a 4 x 4. It was briefly considered by the engineers to cut the hull in half and lengthen it to accommodate a 6 x 6 suspension, but the idea was almost immediately rejected, as the development of a new vehicle was deemed more effective.

Why the PqRMM/2 engineers developed a 4 x 4 for the Army in the first place is a bit strange, considering they knew that the army wanted a 6 x 6 like the M8 Greyhound. Nevertheless, the VBB-1 would lay the groundwork for the research of the 6 x 6 vehicle. Some components were carried over from the VBB-1 to the upcoming 6 x 6, such as the turret and engine. By starting from scratch, the team could implement all the lessons they learned from the VBB-1 project and thus get a better basis for future developments.

The VBB-1, note the influence of the M8 Greyhound like the turret..
Source: Blindados no Brasil

The VBR-2

For the development of the Viatura Blindada de Reconhecimento 2 (VBR-2) (English: Armored Reconnaissance Vehicle), the PqRMM/2 team followed the specifications of the Diretoria de Motomecanização (DM) (English: Directorate of Motomechanisation). The VBR-2 was pretty much a Brazilian copy of the M8 Greyhound. A single metal mock-up of the VBR-2 was made by the PqRMM/2 in early 1970.

Its overall shape was almost identical to the M8, with the raised hull construction for the driver being one of the most notable features. The hull construction was a bit more simplified though, with more flat plates like the VBB-1, but without some of the complicated shapes of the VBB-1. It mounted the same turret as the VBB-1, which was a copied M8 Greyhound turret but with a closed top. It was armed with a 37 mm cannon and a .50 cal machine gun.

The engine deck style also resembled the M8’s and came from the VBB-1 design as well. Considering the overall design features, it can be expected that the rear of the VBR-2 would also look like the M8, considering the VBB-1 and the later EE-9 Cascavel rear all share the same design.

VBR-2, note the VBB-1 turret and its overall blocky design, the VBR-2.
Source: https://www.cibld.eb.mil.br/index.php/historico-2/blindados-eb-parte-3

The CRR

The VBR-2 mock-up underwent various redesigns together with a redesignation to Carro de Reconhecimento sobre Rodas (CRR) (English: Wheeled Reconnaissance vehicle). The hull underwent some geometric redesigning, causing the vehicle to look less like a box because of the more angled side plates. Another difference in the hull design, which enabled the hull to receive an improved ergonomic design, was the redesign of the driver’s raised hull construction.

The VBR-2 had a raised construction that extended towards both sides of the hull to provide vision for both the driver and co-driver much like the M8 Greyhound. The raised hull construction was now located in the middle of the hull on the CRR and did not extend to both sides of the hull. This meant that the CRR did not have a co-driver, which reduced the crew to 3.

Another important step in the development of the CRR was the installation of the Boomerang suspension from Engenheiros Especializados SA, better known as Engesa. Engesa had previously modernized and delivered new trucks for the Brazilian Army with their Total Traction system. This patented traction system was the key for Engesa in the defense industry, mainly because it was identified as a system ‘of interest to National Security’ by the Army. Engesa also participated in the VBB-1 project by supplying the transfer box. With the VBR-2 built, the PqRMM/2 team sought a better suspension system for the 6 x 6 vehicle and found it in an invention from 1969.

The CRR during construction.
Source: Ford M-8 Greyhound no Exército Brasileiro – Expedito Carlos Stephani Bastos

The Boomerang Suspension

In 1969, Engesa invented the Boomerang suspension. The suspension was invented to enable trucks to transport oil from difficult terrain with bad infrastructure to the refineries. With this suspension, the trucks could traverse otherwise untraversable hills for conventional suspension systems, as the wheels would always stay in contact with the ground to provide maximum traction.

An EE-9 M2 showing the boomerang suspension.
Source: Engesa Brochure

The suspension system was a two wheeled-single axle driven suspension. The advantage of the boomerang suspension was that it could be fitted on existing differentials with a single axle. Normally, this meant that the single axle, designed for the torsion forces of a single wheel, was subjected to the torsion forces of two wheels. Through excellent engineering, half of the torsion forces of the two wheels were mitigated by the suspension system built around the original axle. This design not only enables the drive of two wheels by a single axle but with clever usage of gears and bearings on both the axle and tube around the axle, the suspension system can rotate around its axle for 360 degrees. This ability to rotate in extreme angles would enable the vehicles to traverse very difficult terrains and still provide maximum traction, as the suspension system curved with the terrain so that all the wheels were always in contact with the ground.

The boomerang suspension.
Source: Engesa manual

Engesa

Engenheiros Especializados SA, or Engesa, was the largest and the most famous company in the Brazilian armored vehicle industry. Engesa was founded in São Paulo in 1958 by José Luiz Whitaker Ribeiro. Initially, Engesa focused on oil prospecting, production, and refinement equipment. With the invention of Engesa’s total traction suspension system, they were hired to modernise and build trucks for the Brazilian Army.

In 1969, Engesa introduced its flagship boomerang suspension for its wheeled vehicles. Only a single axle was needed to drive the 4 wheels which were in constant contact with the ground, providing constant traction. At the time, this was a simple, sturdy, and relatively cheap construction. Although not fit for heavy vehicles, it was perfect for the armored vehicles that Engesa would start to manufacture in the near future.

With Engesa’s involvement in refitting the Army’s trucks with the Total Traction system and the development of their Boomerang suspension, they were contacted by the Army to help develop the wheeled vehicles together with the PqRMM/2 team. This joint development resulted in the EE-9 Cascavel and the EE-11 Urutu. The EE-9 Cascavel paved the way for Engesa to take its position as the leading company of the Brazilian Defense Industry.

Engesa Logo.
Source: https://en.wheelsage.org/engesa/logotypes/488339

The Cascavel is Born

With the installation of the boomerang suspension and the redesign of the hull, the basis was laid for what would become the EE-9 Cascavel. The mock-up of the CRR was built in early 1970 and presented to General Plínio Pitaluga, a veteran of the FEB. It seems that, almost immediately after the mock-up was finished, the PqRMM/2 engineers started the production of the first working prototype.

Nearing the end of the construction of the CRR prototype, a new turret was developed for the new 6 x 6 vehicle. The CRR mounted a redesigned VBB-1 turret with a turret bustle. The VBB-1 turret was a copy of the M8 Greyhound turret and was manufactured by Fundições Alliperti S/A and Avanzi. It is noted that the redesigned VBB-1 turret was manufactured by Companhia Siderúrgica Nacional (CSN) (English: National Steel Company). Although the CRR received the redesigned VBB-1 turret, the original plan was to mount copied and redesigned M3 Stuart turrets with an added turret bustle, which were also produced by CSN. But, by the time the CRR prototype was finished, the redesigned M3 Stuart turrets were not ready yet.

The finished prototype of the CRR with the VBB-1 turret and boomerang suspension.
Source: Ford M-8 Greyhound no Exército Brasileiro – Expedito Carlos Stephani Bastos

The prototype of the CRR was completed in 1971. It used a copied and redesigned M8 turret armed with a 37 mm cannon and a .50 machine gun on top of the turret. The turret was a fully enclosed turret designed by Engesa. The vehicle-mounted run-flat tires were previously developed by Novatracão for the VBB-1 project. The vehicle’s exhaust was located on the right side of the rear. The vehicle had a crew of 3. The driver was positioned in the middle of the hull and had a raised structure for his head and the sights. The remaining two crew members were the gunner and the commander/loader.

The CRR.
Source: Engesa brochure

The CRR was extensively tested by the Brazilian Army, tests which were overseen by the PqRMM/2. During the tests, the CRR prototype travelled over 65,000 kilometers and performed various mobility tests. The tests were successful, as the construction of a 5 vehicle pre-series was approved. The number of pre-series vehicles would increase to a total of 8 vehicles after the Diretoria de Pesquisa e Ensino Técnico do Exército (DPET) (English: Army Directorate of Research and Technical Education), which oversaw the PqRMM/2 developments, signed a contract with Engesa in June 1971 for the development and construction of the pre-series. Production of the 8 pre-series vehicles for the Brazilian Army began in 1972 and was finalized in September 1975.

The Finished CRR with the redesigned M8 turret on the right, and the CTRA (Carro de Transporte sobre Rodas Anfíbio, English: Wheeled Amphibious Troop Transport), a predecessor of the EE-11 Urutu, on the left.
Source: Engesa Brochure

With the signing of this contract, the CRR was officially carried over to Engesa. What is interesting is that the Brazilian Army, despite having developed the CRR, signed off all their intellectual property rights to Engesa. This effectively meant that the Brazilian Army itself would not directly profit from any sales of the future EE-9 Cascavel to other countries. This transfer to Engesa also meant that the CRR would be marketed as the EE-9 Cascavel.

The CRR during trials.
Source: Ford M-8 Greyhound no Exército Brasileiro – Expedito Carlos Stephani Bastos

The Snake Family

The EE-9 Cascavel was part of a family of wheeled vehicles, all named after snakes found in Brazil. These vehicles were the EE-3 Jararaca, EE-9 Cascavel, EE-11 Urutu, and EE-17/18 Sucuri, meaning jararaca, rattlesnake, crossed pit viper, and anaconda, respectively.

A ‘’Cascavel’’ or rattlesnake in English.
Source: https://pt.wikipedia.org/wiki/Cascavel#/media/Ficheiro:Cascavel_-_crotalus_durissus.jpg

The EE-3 was a 4 x 4 reconnaissance vehicle that could mount a wide range of turrets. The EE-9 was Engesa’s reconnaissance vehicle, but due to its mobility and the 90 mm cannon, it would be employed in all kinds of roles. The EE-11 was a troop transport but could be configured to perform all sorts of specialised roles, like Anti-Aircraft, mortar carrier, and ambulance. The EE-17 and EE-18 Sucuri were two 105 mm armed 6 x 6 wheeled tank destroyers.

Logos of Engesa’s Snake family.
Source: Blindados no Brasil – Expedito Carlos Stephani Bastos

The EE-9 was effectively the flagship of this family, even though Engesa thought the EE-11 would be their most successful vehicle. The EE-11 was successful nevertheless, but the Jararaca and the Sucuri were less of a success. The Jararaca was sold in very limited numbers, while the Sucuri was not even sold at all.

Top left: EE-3 Jararaca, top right: EE-9 Cascavel, bottom left: EE-11 Urutu, bottom right: EE-18 Sucuri.
Sources: Engesa brochure, Wikimedia, Forte.jor.br, Military-today.com

Cascavel Designations

With the transfer of the CRR to Engesa also came a new designation. The exact date of when the CRR was designated as EE-9 is unknown. But it is estimated to have been named EE-9 between 1972 and 1973, with EE referring to Engenheiros Especializados (English: Specialized Engineers) and the 9 to its weight in tonnes. The interesting part is that practically every Cascavel exported by Engesa weighed more than 10 tonnes empty. As such, the 9 in EE-9 refers to the 37 mm version of the Cascavel. The weight in a brochure, which is estimated to have been written between 1973 and 1974, refers to the Cascavel with a 37 mm gun as having a 9 tonnes combat weight.

The CRR was redesignated by the Army as well, with the completion of the pre-production batch, to Carro de Reconhecimento Médio (CRM) (English: Medium Reconnaissance Car). This designation is more of a vehicle classification, like the CRR, than a name. This effectively means that the prototype CRR, the pre-production CRM, and the production vehicles were all known and sold as EE-9’s.

What is interesting, is that Engesa seems to have skipped designating an M1 Cascavel, and immediately built M2 hulls after the CRM. It might be that the 37 mm Cascavels were unofficially seen as first production versions, but through hull classification were simply branded as M2’s.

Since the EE-9 Cascavel was built and developed for 18 years, it received upgrades and design changes over time. To keep track of these changes, a so-called Modelo or Model system was used. It is important to note that different guns or turrets did not mean that the Cascavel was a different model. The Cascavel M2 for example, used all three 90 mm turrets offered by Engesa (HS-90 turret with the French D-921 gun, ET-90 I turret with EC-90 gun, and the ET-90 II turret with EC-90 gun). It was mainly changes to the hull, and especially the transmissions, which caused the Cascavels (Portuguese: Cascavéis) to be classified as a certain model. The Modelos were then further subdivided in production batches or Séries. The differences between the series could be as small as different bolts or different tyre nozzles. The development of the Cascavel was a process of evolution, and certain manuals would be written specifically for a range of series of a certain model.

The enthusiast’s guide to Engesa’s Cascavel galaxy

Model Charatistics Date Sold numbers by Engesa
CRM The pre-production EE-9 with a manual Clark 280V transmission and a 37 mm gun, practically an improved M8 Greyhound. 1971 8
EE-9 M2 Interestingly, Engesa seems to have skipped designating a Cascavel with the M1 designation. As a result, the production Cascavels with 37 mm guns are also M2’s.
The first EE-9 to have a 90 mm gun as its main armament. Overall hull redesign, larger dimensions of the hull to mount the new 90 mm armed turrets. Used a manual Clark 280V Transmission
1974 Brazil: 157 of which at least 9 were originally armed with 37 mm.
Bolivia: 24
Chile: 83
Libya: 200
EE-9 M3 Effectively an M2 Cascavel, but with an automatic MT-540 transmission (the first Cascavel model with an automatic transmission). The first Cascavel model to receive the EC-90 gun. 1975 Libya: 200
EE-9 M4 The M4 was specifically designed, built and sold with the Detroit Diesel 6V53 engine. Overall strengthening of components and further evolution of the hull design. It used an MT-643 transmission. 1979 Brazil (CFN): 6
Colombia: 128
Cyprus: 124
Iraq: 364
EE-9 M5 Used the M4 design but was a cheaper version. It was sold with either an AT-540 or AT-545 transmission in combination with the OM-352A engine. 1981 Bovington Tank Museum: 1
Gabon: 14
Uruguay: 15
EE-9 M6 Automotive enhancements over the previous models. Used the AT-545 in combination with the OM-352A engine. 1982 Brazil: 37
EE-9 M7 The same as the M6, but used an MT643 transmission. This Cascavel was the final model designed by Engesa. It could mount every engine which Engesa sold with the Cascavel, although it only seems to have been used with the OM-352 and the OM352A engines. 1983 Brazil: 215
Ecuador: 32
Paraguay: 28
Suriname: 6
Zimbabwe: 90
Total: around 1,742 sold and less than 1,800 produced.

Arming the EE-9 Cascavel

In 1972, with the start of the construction of the pre-production Cascavels, came the discussion of what the future reconnaissance vehicles of the Brazilian Army should be armed with. Up until then, the reconnaissance doctrine of the Brazilian Army had not changed since their experiences in World War 2, and this old doctrine was still somewhat ingrained in the Army.

An analysis regarding the specifications for a reconnaissance vehicle was released on July 10th 1967. The requirements called for a vehicle which could penetrate its own armor at ranges up to 1,000 meters, fire in all directions (have a turret), a rate of fire of at least 3 shots per minute, and the armament did not have to be used for anti-air purposes. The issue with these requirements is that practically every gun of 20 mm and higher could perform this job.

With the initiation of the VBR-2 project, a discussion emerged within the Army. Recommendations were gathered on what to arm the coming generation of reconnaissance vehicles. The issue was that the Armies (plural) of Brazil, generals, and departments gave conflicting advice about what to arm the vehicle with. Aside from this, the Army also had to take export potential into consideration for Engesa. Since the Brazilian Army completely handed over the project to Engesa, they also wanted to keep logistics and profit for the company as advantageous as possible. By the end of 1972, the Brazilian Army had selected two ranges of potential cannons: 20 to 40 mm or the 90 mm. The Army referred to the FV107 Scimitar for the lower caliber cannons, potentially suggesting that they wanted an autocannon on the Cascavel, and not the 37 mm which they had used so far.

With the selection of the two ranges, a new discussion came at the forefront regarding the purpose of the reconnaissance vehicle. It was recognized that less than 4% of the missions performed by cavalry units during World War 2 were pure reconnaissance missions. The question then was which role would the future Cascavel perform the most and which of these guns was the most suitable. The 90 mm would perform best for anti-tank missions, while the 20 to 40 mm range would be more fit against personnel and overall perform an infantry fighting vehicle role, without being able to carry infantry. It was identified that the EE-9 would not be fit to fill the Infantry Fighting Vehicle role as it did not have the armor to reliably perform this role. At the same time, it was recognized that a 90 mm gun would give the Cascavel a better fighting chance against potential enemy armor. The reasoning was mainly from an isolation point of view, in which a Cascavel on a reconnaissance mission had to fend for itself and take out potential enemies, like tanks. It was determined that the 90 mm was the most suited for this role, considering most of Brazil’s neighbours operated the Shermans as their heaviest armored vehicles at the time, and employed a large number of AMX-13’s and SK-105’s as their other combat tank.

It took up to the second half of the 1970s for the Brazilian Army to completely make up its mind on which cannons should be used on the Cascavel. When this discussion still raged in 1977, the Cascavel with 90 mm gun was already used by Libya against Egypt, and multiple countries ordered the 90 mm cannon.

What might have steered the Brazilians towards eventually deciding to operate a 90 mm Cascavel only force were the trials in Portugal in 1973. Portugal was still in the War of Ultramar as it tried to maintain its colonial empire. Among the vehicles the Portuguese used to fight their opponents was the AML-90. The AML-90 was a 4 x 4 armored car which could be used for reconnaissance and was armed with the potent D-921 90 mm gun.

An AML-90.
Source: https://www.super-hobby.nl/products/Panhard-AML-90-Reconessance-vehicle.html

The Portuguese were approving of the EE-9 Cascavel, which boasted better mobility than their AMLs, but suggested that Engesa should retrial the vehicle when it was armed with the French D-921 gun. As a result, the Brazilian Army ordered the turrets and guns for both the single EE-9 of Engesa and the X1 tank program as well. Engesa retrialled the EE-9 in early 1974, but would not manage to sell the vehicle, as the Portuguese government was overthrown and the War of Ultramar ended. The Engesa team decided to pack up their vehicles and head straight to Libya, where they managed to secure a deal for 200 EE-9 Cascavels armed with 90 mm guns.

From this point on, an increasing number of countries started ordering the 90 mm Cascavel, and it is thought that the popularity of the 90 mm gun, in combination with the performance of the 90 mm gun, caused the Brazilian Army to finally opt for the 90 mm armed Cascavel.

Armoring the EE-9 Cascavel

Until 1968, armor studies were practically non-existent in Brazil. There had been some brief attempts during the revolutions of 1924, 1930, and 1932, but these were mainly of improvised nature. With the initiation of national armored vehicle development also came studies on what to armor the upcoming armored vehicles with. The PqRMM/2 team started off by evaluating all the steel compositions of the vehicles which were acquired by the Brazilian Army over time. The team discovered that the homogenous steel plate of the M2 Half-Track had been heat-treated on the outer side to provide a harder surface, while providing a more ductile surface on the inside to prevent shattering.

The team determined that the effort needed to carry out the necessary techniques for hardening was only justifiable for mass production. With mass-production of the future armored vehicles being expected, the team decided that the development of a dual-hardness plate or bimetal armor would be viable. This type of steel was previously developed in Sweden in 1930 and was known as duplex steel. It would find its first extensive usage on armored vehicles in Brazil. The main difference from other examples of face hardened armor is that two plates of varying carbon content were welded together in production to form a bimetal plate instead of bolting on a hardened plate afterward.

The steel for the bimetal plates was provided by Eletrometal and Usiminas. With Eletrometal providing the high-carbon outer plates and Usiminas the medium-carbon plates. The plates were joined, with 25% of the total plate thickness being high-carbon steel and 75% medium-carbon. The plates were laid on top of each other and subsequently welded around the edges. The bimetal plates were then forged together from 65 mm to about 30 mm thickness and then hot-rolled to the required thickness, This was followed by a quench, tempering, and hardening to the desired hardness. The high-carbon plate was hardened to 700 Brinell while the medium-carbon plate was 250 Brinell.

The average effectiveness of the bimetal plates was about 1.8 times the thickness of an equivalent homogeneous plate against 7.62 mm or 1.5 times the thickness against .50 machine gunfire. This meant that, against .50 machine gun fire, a 16 mm bimetal plate could be used instead of a 25 mm homogenous steel plate. These protection advantages over homogenous plates effectively meant that the Cascavel saved a lot of weight without compromising protection. The outer layer would shatter and blunt the incoming projectile, while the inner layer would relatively move with the bullet, slowing it down and stopping it without shattering.

An interesting tidbit of information according to an ex-Engesa employee who worked at the tempering station was that, at some point, the armor did not perform according to standards. It turned out that the tempering oven was not maintained properly, and the temperature control was faulty. This issue would remain for a few years until it was finally resolved. In order to keep building the armored vehicles, a lot of these plates were approved by quality check anyway, despite being faulty.

Trials in Portugal

In early 1973, Engesa trialled their vehicle in Portugal in an attempt to export it. As previously mentioned, Portugal was fighting against its uprising colonies in the War of Ultramar, also known as the Overseas War in English. At the time, the Portuguese Army was operating a mix of AML-90 and Panhard EBR armored cars in Africa. The Portuguese were impressed by the EE-9 Cascavel, which at that time was most likely still in its CRR configuration, but they suggested that Engesa should arm the Cascavel with the same turret and gun as the AML-90 and return to trial the vehicle again.

With Engesa wanting to arm the Cascavel with a 90 mm gun, the Brazilian Army opted to go for the 90 mm gun on the X1 project as well. They bought 53 turrets and guns from the French company SOFMA. Most of these turrets were ditched, as they did not meet the protection requirements of the Brazilian Army, and local turrets were designed and built as a result. Engesa would arm the EE-9 sent to Portugal with the French turret, but also developed their own turret.

The EE-9, most likely with the M2 hull design to solve some practical issues of the CRR configuration, and mounting an HS-90 turret and armed with a D-921 90 mm gun, was trialed again in early 1974. This EE-9 trialed in Portugal could be counted as being the first 90 mm armed EE-9 M2 Cascavel. The problem is that these designs were made before the later production variant of the EE-9 was known to have been built around 1975. For this reason, these projects will be seen as prototypes for both the 90 mm armed EE-9 M2, because of its armament, and as prototypes for the 37 mm EE-9 M2 because of the likely redesigned hull. Portugal would not acquire the EE-9 M2 because a Coup d’Etat put an end to the War of Ultramar.

The influence of Portugal in the success of the EE-9 should not be understated. After the failed attempt to sell the EE-9 Cascavel to the Portuguese, the Engesa team loaded the Cascavel and Urutu back in their freighter and set course to Libya. There, the EE-9 M2 would find success and manage to secure a deal for 200 Cascavels. This deal brought the necessary cash for Engesa to buy a large production plant, and by 1975, the first production Cascavels started rolling from the production line.

The request of the Portuguese to arm the EE-9 with a 90 mm gun effectively helped Engesa to secure a deal with Libya, which would eventually use the Cascavel in combat, generating more sales and making the Cascavel the success it was. At the same time, Brazil also started the development of locally produced turrets for the 90 mm guns for both the Cascavel and X1.

90 mm Turret Designs on the CRR hull

The switch from 37 mm towards the 90 mm would normally mean that the EE-9 Cascavel is an EE-9 M2. These projects were specifically designed on the early CRR hull or on a hybrid between the CRR and the pre-production vehicle which would be designated as Carro de Reconhecimento Médio (CRM) (English: Medium Reconnaissance Car). The problem is that these designs were made before the production vehicle of the EE-9 was built. For this reason, these projects will be seen as prototypes for both the EE-9 M2, because of their armament, and as prototypes for the 37 mm armed EE-9 M2, because of the hull. There were two designs: a CRR/CRM hybrid mounting the copied and lengthened M8 turret and armed with a 90 mm gun and a CRR with the French turret.

The CRR with HS-90 turret

The Brazilians made a design with the CRR hull mounting an HS-90 turret. This design was effectively the predecessor of the EE-9 M2 Cascavel. The HS-90 turret was ordered from France and had to be bought as a full package, including the D-921 gun. This Cascavel would have had a gun depression of 8 degrees and an elevation of 15 degrees. Aside from the 90 mm gun, it was also armed with a coaxial 7.62 machine gun. In addition to its armament, it would also be armed with 3 smoke launchers on each rear side of the turret. It could mount a turret top machine gun, night vision sights, radio and intercom, laser rangefinder, and an extra ammunition stowage as optional equipment. It is stated that the EE-9 sent to Portugal used this turret, but it is unlikely that the CRR hull was used for these trials.

The CRR with a HS-90 turret.
Source: Engesa brochure

The reason for this is that the HS-90 turret would not only be too big for the hull and come in collision with both the driver’s vision structure, but also with the engine bay covers. On top of that, the driver’s vision structure would make it virtually impossible to depress or even fire the gun on a flat angle. As such, it seems that the drive for the 90 mm turret caused the hull to be redesigned to resolve these issues.

A sketch detailing the collision issues of the HS-90 turret on the CRR hull.
Done by Godzilla.

The CRR/CRM Hybrid M8 Copy Turret

Another of the designs was effectively a hybrid between the CRR and the later CRM production vehicle. The main hull design change which hints towards it being a hybrid design is the altered headlight guard. On the CRR, the headlight guard was a simple square design, while in this design, it was curved, like on the CRM.

In addition, the copied M8 turret also received some changes which would be seen in the turret later used on the pre-production CRM. Compared to the original CRR turret, this turret had a ventilation inlet on the top of the turret and the antenna, which was originally on the left rear side of the hull, has now been installed on the turret as well. Apart from these 2 features, the turret also provided periscopes for the gunner, apart from the direct sight in the gun mantlet. The 90 mm gun would have a depression of 8 degrees and an elevation of 13 degrees and be installed in a turret with a turret diameter of 1.6 meter. It could mount a turret-top machine gun for anti-aircraft purposes.

In addition, a Perkins type 6357 6 cylinders in-line 142 hp diesel engine, along with a Chrysler type 318 HD V8 196 hp diesel engine, were offered. But Engesa also offered to fit in other engines, depending on the customer’s needs. It would use a 6-speed manual gearbox with five speeds forward and one in reverse. It would have been protected from the front with bimetal armor, protecting against .50 machine gun fire and from the sides from 7.62 mm fire. The exact weight and speed of this design are unknown but are estimated at around 10 to 11 tonnes and 95 km/h, depending on the engine selected.

The CRR with the redesigned M8 turret, armed with a D-921 90 mm gun.
Source: Engesa brochure

The CRM

By September 1975, the production of the pre-series of 8 vehicles, known as the CRM, was finished. The pre-series hulls still carried over much of the design of the CRR hulls. The CRM can be easily identified and distinguished from the CRR in two ways. The first is the redesigned headlight guards, which were now curved instead of simple squares. The second is the relocation of the antenna and most likely the radio set as well. On the CRR, the antenna is located on the left rear of the hull, while on the CRM, the antenna was moved to the turret.

The CRR on the left with the simple square headlight guards and the antenna on the hull, and the CRM on the right with the redesigned headlight guards and without an antenna on the hull.
Source: https://pt.wikipedia.org/wiki/EE-9_Cascavel#/media/Ficheiro:Cascavel1.jpg and Ford M-8 Greyhound no Exército Brasileiro – Expedito Carlos Stephani Bastos

When the CRM was delivered, it seems that the planned altered M3 Stuart copy turrets were still not finished. As a result, the CRM received a much more modernized version of the original CRR turret. The new turret incorporated a ventilation inlet on the left rear of the turret top with the antenna and, most likely, the radio sets moved next to it on the right side. The turret structure on both the commander’s and gunner’s side was also much improved compared to the CRR. A structure was welded on both sides which integrated 2 extra sights to enable a much better overview for the crew.

The CRM, note the added construction on the sides and the redesigned headlight guards.
Source: https://pt.wikipedia.org/wiki/EE-9_Cascavel#/media/Ficheiro:Cascavel1.jpg

The 8 vehicles were almost immediately tested after they were delivered. They had to drive back and forth for 32,000 kilometers between São Paulo to Alegrete. The CRM’s drivo 24/7 and only stop for fuel or if maintenance was needed. The CRM’s seemed to have performed well during these trials, as the CRM, and thus the EE-9 Cascavel, was accepted into service. 102 production vehicles were ordered by the Brazilian Army, all armed with the 37 mm gun.

A Bid for a National Turret

It seems that, around this time, a bid was opened by the Brazilian Army for a locally designed and produced turret to be mounted on the EE-9 Cascavel. Interestingly, of the pictures available, Bernardini built a turret with a 37 mm cannon, while Engesa had the turret with a 90 mm gun which was originally mounted on the X1 prototype. It is very likely that Bernardini also offered the 90 mm turret, as the 37 mm turret was effectively the production turret of the X1, but rearmed with a 37 mm cannon. It is unknown if Engesa built and offered a 37 mm turret. Both of these proposals were built on CRM hulls.

Bernardini’s Entry

As previously stated, Bernardini would have most likely entered the competition with both the 37 mm turret and the 90 mm turret. The turret which Bernardini offered was the production turret of the X1, which was designated BT-90A1. The Brazilian Army had previously bought 53 HS-90 turrets and D-921 90 mm guns. The issue was that the turret armor of the HS-90 was insufficient for the requirements of the Centro de Pesquisa e Desenvolvimento de Blindados (CPDB) (English: Center for the Research and Development of Tanks). As a result, Bernardini and the Brazilian Army started developing a local turret that was armored with 25 mm thick plates to protect the X1 from .50 cal machine gunfire. The design of the BT-90A1 turret was heavily inspired by the HS-90 turret, with the first prototype of the turret (BT-90) even using some components of the HS-90 turret. The main differences between the HS-90 and the BT-90A1 were the addition of a gun shield on the BT-90A1, improved armor, and the BT-90A1 overall being more bulky than the HS-90. The main difference between the 37 mm and the 90 mm turrets from Bernardini was that the 37 mm turret received a new gun shield and was altered for the 37 mm armament.

The CRM mounting Bernardini’s 37 mm turret proposal.
Source: https://armasonline.org/armas-on-line/antigos-equipamentos-do-exercito-brasileiro/

Engesa’s Entry

Engesa’s design was the turret which was briefly mounted on the X1 prototype. The turrets differed in a very minor way. The rear sides of the Engesa turret, on which the most rearward smoke launcher was installed, went inwards instead of being a flat plate. It is unknown if this turret used bimetal armor or not. The vehicle was armed with a 90 mm gun and a coaxial 7.62 mm machine gun. In addition to its armament, the turret also mounted 2 pairs of 3 smoke grenade launchers on both sides of the rear turret.

EE-9 Cascavel with Engesa’s X1 inspired turret, note the rear turret angling.
Source: http://www.warwheels.net/images/WFVBrazilHAUGH.pdf

Who Won?

It is unclear which company won this specific bid, as both the Engesa turret and the Bernardini turrets were never mass-produced. What most likely happened, was the switch from the D-921 gun to the license-produced EC-90 gun, which was based on the Cockerill 90 mm gun. Somewhere between 1975 and 1976, Engesa got a licensing deal with Cockerill for their 90 mm gun. This was an essential shift, as the forced purchase of both turret and gun from the French became increasingly expensive, and building a local turret would have been much cheaper. This turret design bid was most likely initiated around 1975 and probably ended when Engesa got the license deal in order. It is unclear if a new bid for an EC-90 armed turret was opened, but what is known is that Engesa would design the ET-90 turret which would be used on the Cascavels from that point on.

The EE-9 M2 37 mm

With the approval of the CRM by the Brazilian Army, 102 production vehicles were ordered. If these 102 vehicles were actually delivered is unclear. Pictures exist where at least 9 production vehicles, known as the EE-9 M2 Cascavel with 37 mm, are shown. According to statements from ex-Engesa employees, the order seems to have eventually been converted into an order for the 90 mm armed Cascavel M2 and the 37 mm EE-9 M2s were supposedly converted to 90 mm M2s. How many 37 mm M2’s were eventually built before the Brazilian Army switched the order is unknown. It is estimated that the Brazilian Army changed the order around 1976-1977.

The production model differed from the CRM in a couple of ways. The most notable two were the copied and redesigned M3 Stuart turrets, which were now finally delivered, and the removal of the raised driver structure on the hull. Another very important change was the slanting of the rear hull. This was done to fix the issue of the turret bustle colliding with the engine bay covers, and enabled the usage of low-profile turrets. It is thought that the mounting of the 90 mm HS-90 turret initiated the redesign of the hull to accommodate the turret. Another change was the removal of the exhaust pipe on the right rear side of the hull. The exhaust was now mostly located inside the Cascavel, with the exhaust coming out of the right rear side of the vehicle, above the rear wheel. In essence, the EE-9 M2 was a streamlining of the CRM and mounted the final turret.

The EE-9 M2 37 mm was unofficially called ‘Cascavel Magro’, meaning Skinny Rattlesnake, while the 90 mm armed Cascavels were unofficially known as ‘Cascavel Gordo’, meaning Fat Rattlesnake.

Note the integrated hull driver’s hatch and the redesigned M3 Stuart turret on the EE-9M2.
Source: https://webkits.hoop.la/topic/procurando-imagens-do-ee-9-cascavel-magro

The EE-9 M2 37 mm in Detail

The EE-9 M2 weighed about 9 to 9.5 tonnes (9.9 to 10.5 US tons). It was about 5 meters (16.4 feet) long, 2.3 meters (7.5 feet) wide, and the height was around 2.3 meters (7.5 feet). The EE-9 had a three-man crew, consisting of the commander/loader (turret left), gunner (turret right), and the driver in the middle front hull.

EE-9 M2s at a parade, most likely an Independence Day parade around 1975.
Source: https://webkits.hoop.la/topic/procurando-imagens-do-ee-9-cascavel-magro

Hull

The hull of the EE-9 M2 was manufactured from welded bimetal steel plates. The upper front plate was well angled at 60 degrees from vertical. The hull also features two covers which were mounted on the hull at the positions above the boomerang suspension, effectively functioning as mudguards and very minor spaced armor.

The front upper hull plate presented 16 mm (0.63 inch) of bimetal armor at an angle of 60 degrees. The sides and rear were 8.5 mm (0.33 inch) thick at varying angles, and the top and bottom hull were 6.5 mm (0.26 inch) thick. The front of the EE-9 was meant to protect from .50 machine gun fire at an unknown range, while the entire vehicle was protected from 7.62 mm AP rounds at 100 meters (109 yards), and standard 7.62 mm rounds at 50 meters (54 yards).

The EE-9 had two headlights externally mounted on top of both sides of the upper front hull plate. A rearview mirror could be mounted on both headlight guards. A black-out light was installed on the right side of the left headlight. Below the driver’s hatch was a foldable windshield, which the driver could use when driving with an open hatch. It is not completely clear in pictures, but it seems that the driver’s hatch was a two-piece hatch, with the front part being part of the upper front plate, while the back part was part of the top hull plate. The front hatch had three periscopes for the driver for 180 degrees of vision. These periscopes and other periscopes or sights would not have been active or passive night vision equipment unless the Cascavel was ordered with these devices.

The EE-9 M2, note the lengthened M3 Stuart turret.
Source:https://webkits.hoop.la/topic/procurando-imagens-do-ee-9-cascavel-magro

A ventilation inlet was installed on both upper hull side plates, these ventilation inlets are recognizable by their frustum shape. A siren was installed behind the ventilation inlet on the right side of the vehicle. The fuel tank cap of the Cascavel was located on the left side, in the middle of the upper side hull plate. The EE-9 had a large ventilation grille on the rear of the vehicle, reminiscent of the M8, and had a rear light on both sides of the ventilation grill. The engine could be accessed through two large hatches on the hull top rear.

The driver steered the vehicle with a steering wheel and had his gear stick on his right side, and his instrument panel to his left. The acceleration pedal was located on the right side of the steering wheel, and the brake was next to the acceleration pedal on the left. On the left side of the steering wheel was the clutch pedal.

Mobility

The exact engine which would have been used in the 37 mm EE-9 M2 for the Brazilian Army is unknown. There is a range of potential engines which could have been used, which include the following:

Engine

Fuel

Horsepower

Torque

Perkins 6357 6-cylinder in-line

Diesel

142 at 3,000 rpm

395 Nm at 1,350 rpm (291 ft-lb)

Chrysler 318 HD V8

Gasoline

196 at 4,000 rpm

411 Nm at 2,400 rpm (303 ft-lb)

Mercedes OM352

Diesel

125 at 2,800 rpm

353 Nm at 1,600 rpm (260 ft-lb)

Mercedes OM352A (turbocharged)

Diesel

156 at 2,800 rpm

431 NM at 1,800 rpm (318 ft-lb)

Of these 4 engines, the two most likely would have been the Perkins and the Mercedes OM352 engines. Both were diesel engines. The Perkins was mentioned in an early brochure, and the OM352A is said to have only been used and sold after the first Libyan batch of Cascavels. Considering the Brazilian Army and Engesa switched to the OM352A engine later on, it would not be unlikely that the first engine was a Mercedes. This is all the more likely when one considers Mercedes’ involvement with the motorization of the M8 Greyhound, the half-tracks, and the VBB-1. Sadly, a definitive answer cannot be given at present.

In the end, it probably would not matter too much which engine the EE-9 M2 had, as the Perkins and the OM352 seem to have been somewhat similar in overall performance if one takes the difference of rpm’s into account.

The M2 Cascavel had a top speed of 95 km/h (59 mph) and an operational range of 700 km (353 miles). It had a turning radius of 7.7 meters (8.1 yards) and it could ford a depth of 1 meter (3.3 feet). The Cascavel could climb a 35-degree slope, could climb a vertical obstacle of 0.65 meter (2.1 feet), cross a trench of 1.65 meters (5.4 feet), and had a ground clearance of about 0.5 meters (1.6 feet). The front-wheel could travel for 0.2 meters (0.66 feet), while the rear wheels could travel for 0.9 meters (3 feet). It used 11 X 20 run-flat tires with a diameter of 0.5 meters (1.6 feet). The EE-9 M2 had a distance between the front axle and rear axle of 2.8 meters, and a distance of 1.4 meter (4.6 feet) between the two rear wheels.

The EE-9 used a manual Clark 280V transmission with 5 gears forward and 1 in reverse. In addition, the Cascavel used an Engesa 2 speed transfer case, which allowed the Cascavel to be used in reduced and high gear. By putting the Cascavel in reduced gear, the Cascavel sacrificed horsepower for torque, making it more effective in climbing slopes. The vehicle was 6 x 6 driven, of which the rear 4 wheels were part of the boomerang suspension. The boomerang suspension, in combination with the Engesa 2 speed transfer case, enabled the Cascavel to cross challenging terrain and provide maximum traction in most situations. The power of the engine was distributed to a differential on the front side of the vehicle, and a differential in the rear. The rear differential drove the boomerang suspension with a single axle, which made the boomerang suspension such an ingenious design.

The Boomerang suspension used leaf springs for dampening. The two front wheels were used for steering. The wheels on the boomerang suspension all rotated at the same speed. The front wheels were dampened by large coil springs. The vehicle used hydraulic drum brakes, and was steered with hydraulics as well.

Transmission system of the EE-9 suspension.
Source: Engesa manual

Turret

The turret of the EE-9 M2 was a copy of the M3 Stuart turret. The engineers lengthened the turret to fit radios in the new turret bustle. The turret had two hatches which opened in the same way as on the previous VBB-1 and CRR turrets. In front of those hatches was a machine gun mount. Both the driver and gunner had periscopes around their hatches. An antenna was located on the right rear of the turret. An openable hatch with a vision sight incorporated was installed on both sides of the turret. A basket for stowage was mounted around the entire turret bustle. The commander was located on the left and the gunner on the right.

The armor of the turret is unknown. Considering it was a copy of the M3 turret, the protection levels might have been similar. An estimate of the EE-9 M2 turret protection would be that the front would have been armored with a plate of 51 mm (2 inch) thick at an angle of about 14 degrees from vertical. The gun shield would have been 38 mm thick (1.5 inch). The sides and rear of the M3 Stuart turret were 32 mm (1.26 inch) thick, and the top was 13 mm (0.5 inch) thick. It is worth considering that these are the armor values of the original M3 Stuart turret, and that the EE-9’s armor values might have differed.

The EE-9 M2 turret
Source: https://webkits.hoop.la/topic/procurando-imagens-do-ee-9-cascavel-magro

Armament

The EE-9 M2 used a 37 mm M6 cannon as main armament. The 37 mm M6 had a total length of 2.1 meters (6.9 feet) and a bore length of 1.98 meters (6.5 feet). The 37 mm cannon was able to fire the M51 APC round with 53 mm (2.1 inch) of penetration at 455 meters (500 yards) at a 30-degree angle, and 46 mm (1.8 inch) of penetration at 915 meters (1,000 yards) at a 30-degree angle. It could also fire the M74 AP, M63 HE, and M2 canister rounds. In addition to the 37 mm cannon, the EE-9 mounted a coaxial 7.62 machine gun on the right side of the turret, and a .50 caliber M2 machine gun on top of the turret. Interestingly, some pictures show the .50 machine gun mounted on the front top of the turret, while others show the .50 machine gun mounted on the top rear. The available ammunition of the EE-9 is unknown.

Fate

In the end, only 9 37 mm armed EE-9 M2s have been confirmed to have been built by Engesa. 102 were ordered, but it seems that the rapid developments on the export market of the EE-9 would quickly put an end to the M2 production order. By 1976, the order was probably converted to an EE-9 M290 mm order. The 37 mm EE-9 M2s were supposedly rearmed with 90 mm’s. How many 37 mm M2s were actually built and converted remains a mystery. If these 37 mm EE-9 M2’s ever were delivered to Army units and to which, is unknown. Some sources suggest that up to 50 M2s were built, but they are very vague about this number. It is at least certain that 9 were produced and were later converted to the M2 standard.

Although the 37 mm M2s did receive serial numbers, it is not known if they were operating in a unit or if they were still serving as parade vehicles. If the 37 mm EE-9 M2 was used in service, they would have served in the following mechanized platoon structure: 1 radio jeep, 4 reconnaissance jeeps, 2 EE-9 Cascavels, 1 Urutu, and 1 ammunition carrying jeep.

The EE-9 M2 of Brazil.
Source: Private collection

Conclusion

The EE-9 M2 37 mm seems to have been more of a stopgap than anything else. Although the Brazilian Army wanted the 37 mm armed EE-9 M2, debates within the Army were already heading towards either an autocannon or a 90 mm cannon-armed Cascavel. It was at least quite clear from the start that the rest of the world wanted the 90 mm Cascavel. Considering the EE-9 M2 was already ordered by Libya, the M2 37 mm was already outdated before it was even put into production for the Brazilian Army. Eventually, the Brazilian Army folded towards the 90 mm, and made the decision definitive when Engesa could build their own turrets instead of importing them.

As such, the 37 mm EE-9 M2 itself was an excellent platform with an outdated turret. The Portuguese recognized the capabilities of the EE-9 and were the ones to give the nudge to Engesa to go forward and arm it with a 90 mm. The 37 mm was an armament of the past, while the boomerang suspension and the bimetal armor provided excellent mobility in combination with protection. The Brazilians had succeeded in building their improved version of the M8 Greyhound and established the groundwork for what became Brazil’s most-produced armored fighting vehicle of all time.

Illustrations

The VBR-2, done by Godzilla.
CRR with the VBB-1 turret, done by Godzilla.
The CRR with the M8 copy turret, done by Godzilla.
How the CRR with HS-90 turret would have looked like, note the turret collisions. Done by Godzilla.
The CRR/CRM hybrid with the 90 mm armed M8 inspired turret. Done by Godzilla.
CRM with the modernised M8 inspired turret. Done by Godzilla.
CRM with 37 mm armed BT-90 turret of Bernardini.
The CRM with the 90 mm armed BT-90 inspired turret by Engesa. Done by Godzilla.
The EE-9 M2 37 mm Cascavel, done by Godzilla.

Specifications EE-9 M2 37 mm

Dimensions (L-W-H) 5 meters x 2.3 meters x 2.3 meters (16.4 feet x 7.5 feet x 7.5 feet)
Total weight 9 to 9.5 tonnes (9.9 to 10.5 US tons)
Crew 3 (Driver, commander, gunner)
Propulsion Most likely a Perkins Perkins 6357 6-cylinder in-line or Mercedes OM352
Suspension Boomerang suspension
Speed (road) 95 kmh (59 mph)
Operational range 700 km (435 miles)
Armament 37 mm M6
.30 caliber machine gun (Coaxial)
.50 caliber machine gun (Turret top)
Armor

Hull

Front 16 mm (0.63 inch)
Side 8 mm (0.32 inch)
Rear 8 mm (0.32 inch)
Top 6.5 mm (0.26 inch)
Floor 6.5 mm (0.26 inch)

Turret

Front 51 mm (2 inch)
Gun mantlet 38 mm (1.5 inch)
Sides 32 mm (1.26 inch)
Rear 32 mm (1.26 inch)
Top 13 mm (0.5 inch)

Production At Least 9, up to a hundred

Special thanks to Expedito Carlos Stephani Bastos, the leading expert in Brazilian vehicles, please visit his website for further reading on Brazilian vehicles: https://ecsbdefesa.com.br/, Jose Antonio Valls, an Ex-Engesa employee and expert in Engesa vehicles, Paulo Bastos, another leading expert of Brazilian Armored vehicles and the author of the book on Brazilian Stuarts and the website https://tecnodefesa.com.br, Adriano Santiago Garcia, a Captain in the Brazilian Army and ex-company commander on the Leopard 1 and ex-lecturer on the Brazilian Armored School, and Guilherme Travassus Silva, a Brazilian with whom I was able to endlessly discuss Brazilian Vehicles and who was always willing to listen to my near endless ability to talk about them.

Sources

Engesa EE-9 Cascavel 40 anos de combates 1977-2017 – Expedito Carlos Stephani Bastos
Ford M-8 Greyhound Exército Brasileiro – Surge o conceito de blindado 6×6 – Expedito Carlos Stephani Bastos
Blindados no Brasil – Expedito Carlos Stephani Bastos
Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivatives – Hélio Higuchi, Paulo Roberto
Bastos Jr., Reginaldo Bacchi
Engesa manuals
Engesa brochures
http://www.lexicarbrasil.com.br/
Dual Harness skin stops armor-piercing projectiles Article of Richard M. Ogorkiewicz
Sipri Arms Transfer Database

Stuart: A history of the American Light Tank, Volume 1 – R.P. Hunnicutt
Armored Car: A history of American Wheeled Combat Vehicles – R.P. Hunnicutt

Personal correspondence with Ex-Engesa Employees
Personal correspondence with Expedito Carlos Stephani Bastos
Personal correspondence with Paulo Roberto Bastos Jr.
Personal correspondence with Adriano Santiago Garcia

Categories
Cold War Brazilian Armor Foreign Vehicles In Brazilian Service WW2 Brazilian Armor

T17 Deerhound in Brazilian Service

Brazil (1944-1972)
Armored Reconnaissance Vehicle – 54 Purchased

With World War 2 in full swing and the United States at war with the Axis, the United States sought to secure its position on the American continent. Through multiple ways, the United States would successfully influence all the American countries to either side with the Allies or stay neutral throughout the conflict. Brazil was one of these American countries which joined the side of the Allies in August 1942, partially because German submarines sank multiple Brazilian ships close to the Brazilian coast and due to Getúlio Vargas’ pragmatic rule of Brazil.

One of the realisations of the United States in their attempt to secure the American continent was that most of the equipment of the armies and infrastructure of the American countries were seriously outdated. Brazil was no exception, as it still operated five Renault FTs and 23 L3/35 in a mixed squadron. During World War 2, Brazil would acquire aid in industry, logistics, army modernisation, and equipment through Lend-Lease. The latter was also done to help deter any neutral American nation from siding with the Axis.

Among the equipment Brazil received were 54 T17 Deerhounds, making Brazil the only country to operate the T17 in regular Army units. In fact, the T17 would be Brazil’s first 6 x 6 wheeled armored fighting vehicle and began the story of 6 x 6 wheeled vehicles in Brazil which still continues to this day with the EE-9 Cascavel and the Guarani APC. Sadly, the Deerhound has become a forgotten vehicle in the United States and it would meet an equal fate in Brazil, being overshadowed by the successful and beloved M8 Greyhound.

A Brazilian T17 Deerhound.
Source: https://cyberplasticmodeler.blogspot.com/2014/07/walkaround-vol11-t17-deerhound-6×6.html

The T17 Deerhound

The development of the T17 Deerhound was initiated after Spring 1941, when the British Purchasing Commission submitted their requirements for both medium and heavy armored cars which they wanted to receive as soon as possible. At the same time, the American Armored Force Board came forward with their specifications for a wheeled vehicle based on the British experience in Africa. The medium armored car was designated as T17, and both Ford and Chevorolet came forward with a design.

The Ford design is what is known as the T17 Deerhound today, with a 6 x 6 suspension system. The Chevrolet design was a 4 x 4 driven vehicle that was redesignated as T17E1 and would later be known as the Staghound. Ford’s design initially used two 90 hp Ford engines, but these were replaced with two Hercules JXD 110 HP petrol engines. Both engines used an individual transmission and linked up to a single transfer case. The T17 had, as a result, 8 forward and 2 reverse gears.

The first pilot was delivered in March 1942 but was rejected due to numerous mechanical defects and extensive failures in the axles and transmission. The second prototype would attempt to solve these issues, but would cause the vehicle’s dimensions and weight to become too excessive and it was rejected again. As a result, the contract of the T17 Deerhound was reduced to 250 vehicles. Originally meant for the British, which had named it T17 Deerhound, they rejected it as well. As a result, the 196 T17 Deerhounds were delivered to the Military Police units in the US with their guns removed, while, unknown to many, 54 T17s were delivered to Brazil through Lend-Lease.

The T17 at Aberdeen Proving Ground on December 4th 1942.
Source: Armored Car – R.P. Hunnicutt

The T17 in Brazil

The story of how Brazil ended up being the only country to receive and operate the T17 Deerhound in combat units is an interesting one. It seems odd that Brazil would order a rejected platform of vehicles, regardless of any lack of materiel or perceived urgency of acquisition. It seems even more odd as the M8 Greyhound was already in service and in use. The answer to this question is that Brazil did not order the T17 Deerhound to begin with. Brazil had ordered 54 M8 Greyhounds, which supposedly arrived in Brazil with the order number of the M8 and the needed documentation. But when the Brazilians started unloading the shipment, it turned out that the ordered M8’s were T17 Deerhounds instead. This was not the only instance either, as a Brazilian archive document requesting clarification from the United States about this issue, also talked about 105 mm M3 howitzers being replaced with 75 mm M1A1’s instead.

Considering the context of the T17 Deerhound project and it being rejected, it seems to suggest that the United States deemed the allocation of M8 Greyhounds to Europe of a higher priority than supplying them to Brazil. The T17 Deerhound was then the perfect vehicle to send instead, as it was still a 6 x 6, they had 250 rejected vehicles standing around, and it was a fairly similar but overall bad vehicle compared to the M8 Greyhound. It thus seems that the United States intentionally dumped the T17 Deerhounds in Brazil.

Brazilian sources are unclear as to when Brazil received the T17 Deerhounds, as they estimate the delivery of the T17 from 1943 to 1944. What is known is that 18 T17 Deerhounds were put into service in September 1944. It would receive the local classification of Carro Blindado de Reconhecimento or CBR (English: Armored Reconnaissance vehicle). The Deerhounds would serve as both reconnaissance and command vehicles.

5 T17 Deerhounds of the 3º RMM during an Independence Day Parade on September 7th 1944.
Source: https://caiafamaster.com.br/destaque/um-seculo-de-blindados-no-brasil-braco-forte-na-defesa-da-patria-aco-no04/

The T17 was delivered to 3 units, 2 were Regimento Motomecanizado’s (RMM) (English: Motomechanized Regiments) and the other was a Batalhão de Polícia do Exército (BPE) (English: Police Battalion of the Brazilian Army). The Regimento Motomecanizado’s would later be renamed and reorganized on May 17th 1946 as Regimento de Cavalaria Mecanizado (RCMec) (English: Mechanized Cavalry Regiment).

Markings would also start to be standardized around this time. From pre-1946, when they used a star in the colors of Brazil, it was replaced from 1946 to 1983 with the Cruzeiro de Sul, translated as Southern Cross. In addition, the registration of the vehicles was also standardized, with the EB10-XXX format. EB referred to Exército Brasileiro, the 10 to the type of vehicle, in this case, a reconnaissance vehicle, and the XXX (for example, 084) to which vehicle.

Drawing of the pre-1946 marking on the left, and the Cruzeiro de Sul on the right.
Source: Ford M-8 Greyhound Exército Brasileiro – Surge o conceito de blindado 6×6

From November 1953, the units would be redesignated as Regimento de Reconhecimento Mecanizado (RRecMec) (English: Mechanized Reconnaissance Regiment) until about 1968-1969, after which they would be designated as RCMec again, which they maintain to this day. Since sourcing mostly refers to the RRecMec and this was the longest period in which the T17 served under this regiment designation, the RRecMec designation will be used for future chapters.

2º RRecMec

One of the regiments to receive 18 Deerhounds was the 2º RMM, stationed in the Rio Grande do Sul state, at Porto Alegre. There, they would be operated along with M3A1 Stuarts, but also with M3A1 Scout Cars and Willys Jeeps. Practically, nothing is known about the T17s which served in the 2º RRecMec, except for a single one. EB 10-084, nicknamed ‘Tuiuti’, was retired in 1970, and turned into a monument in Jaguarão in Rio Grande do Sul state. If this particular T17 still exists is unknown. This is because none of the known surviving T17s have the same registration numbers or markings. There are three Deerhounds without any markings at all, so there might be a slim chance that one of these is the ‘Tuiuti’.

The Tuiuti on display as a monument.
Source: https://www.defesabrasil.com/forum/viewtopic.php?t=18372

3º RRecMec

The 3º RRecMec is, relatively speaking, a more documented regiment regarding the T17. 18 T17 Deerhounds were delivered to the then 3º Regimento Motomecanizado’s on September 4th 1944, stationed in Bagé in Rio Grande so Sul. There, they equipped the 3rd and 4th Esquadrão de Carros Leve (English: Light Vehicle Squadron) and served alongside 34 M3A1 Stuarts which were delivered around the same time.

T17 Deerhound of the 3º RMM during an Independence Day Parade on September 7th 1946. Note the old markings.
Source: Ford M-8 Greyhound Exército Brasileiro – Surge o conceito de blindado 6×6

With the switch to the RCMEC, the Deerhound would serve under a new composition of two reconnaissance squadrons consisting of T17s, M3A1 Scout Cars, and Willys Jeeps, a Light Tank Squadron of M3A1 Stuarts, a command squadron, and a service squadron. The 18 T17s would receive the registrations from EB10-126 to 136, and from 138 to 141. A single Deerhound, thought to be used as a command Deerhound, was designated EB10-123. Interestingly, this Deerhound is thought to have been one of the final T17s in service, as it was retired in 1972.

T17 of the 3º RCMec during exercises in 1947.
Source: Ford M-8 Greyhound Exército Brasileiro – Surge o conceito de blindado 6×6

1º BPE

Like with the 2º RRecMec, practically nothing is known about the service of the T17 within the BPE, which was located in Rio de Janeiro. The only thing that is known is that at least 3 T17s were delivered to the Military Police. If the BPE received 18 Deerhounds is unknown. What is known is that they used them in parades and that they were supposedly retired around the 1970s. The BPE might have been the last operator of the T17 Deerhound.

T17 Deerhounds of the BPE during an Independence Day Parade on September 7th 1966.
Source: Ford M-8 Greyhound Exército Brasileiro – Surge o conceito de blindado 6×6

The Brazilian response to the T17?

Although the T17 was certainly an upgrade compared to the Renault FT or the Fiat Ansaldo L-3, the Deerhound was not popular among the crews. The two Hercules JXD engines had to be synchronized, which was supposedly quite challenging. Because of this, the Deerhounds were usually not really usable. To make matters worse, driving the vehicle on a single-engine in order to get around the synchronization issue would damage the drive shafts. All in all, it seems that the errors which the first T17 prototype had were not really resolved or were simply unfixable because of the T17’s fundamental conception of two engines.

The transmission system of the T17 Deerhound.
Source: Armored Car – R.P. Hunnicutt

Fate

The exact fate of the T17 Deerhounds is unknown. At least 4 vehicles have survived, while the fate of the rest is uncertain. According to Brazilian sources, some of the 37 mm guns were used to arm the 37 mm VBB-1 project. But this is not necessarily presented as a fact. It would not be surprising if the Brazilian engineers used these guns, considering it would have been cheaper to repurpose the guns, and the T17 was practically retired when these projects started in 1970. It is thought that the other 50 T17s have either been scrapped or used as range targets.

The VBB-1.
Source: https://www.lexicarbrasil.com.br/exercito/

The remaining Deerhounds

As far as known, only four T17 Deerhounds still exist in the world. All of these Deerhounds are in possession of Brazil, being retired vehicles from the previous three regiments. The T17s are in mixed condition, with a single vehicle being the most complete, still having both engines, but missing a turret basket. One of the four vehicles is currently being restored by the Centro de Instrução de Blindados (CIBld) (English: Armored Personnel Training Centre).

The most complete T17 is located at the Museu Militar do Comando Militar Sul in Porto Alegre Rio Grande do Sul. This T17 has the registration EB10-170. Considering the 2º RRecMec was located in Porto Alegre, and the EB10-170 is not one of the 3º RRecMec designations, it is quite likely that this Deerhound came from the 2º RRecMec. What is interesting is that the EB10-170 registration is not on all pictures of this T17, suggesting that it might have been painted on at a later date and that the registration might not have been its original registration, or of any other T17 Deerhound at all.

The T17 located at the Museu Militar do Comando Militar Sul.
Source: Deerhound – Paulo Roberto Bastos and Hélio Higuchi

Another T17 was functioning as gate guardian at the 4º Batalahão de Logistica (English: 4th Logistics battalion) at Santa Maria, Rio Grande do Sul. This gate guardian has since been renovated by the CIBld, and is now presented at the Museu de Blindados do Centro de Instrução de Blindados in Santa Maria, Rio Grande do Sul. It has no registration. The hatches of this vehicle are supposedly welded shut, and as such, this vehicle has probably just received an exterior overhaul and is not in running condition.

The T17 located at the Museu de Blindados do Centro de Instrução de Blindados.
Source: Museu de Blindados do Centro de Instrução de Blindados

The third T17 is located at the 1º Parque Regional Manutenção in Rio de Janeiro. Not much is known except that, between 2005 and now, it seems that either the 37 mm gun has been removed or cut off. Considering that this Deerhound is located in Rio de Janeiro, it is quite likely that this vehicle originated from the BPE.

The T17 located at the 1º Parque Regional Manutenção.
Source: http://the.shadock.free.fr/Surviving_T17_T17E1_T18.pdf

The fourth Deerhound is located at the Parque Histórico Marechal Manuel Luís Osório in Tramandaí, Rio Grande do Sul. This vehicle also does not have any registration, but considering it is located close to Porto Alegre, it is quite likely that this Deerhound came from the 2º RRecMec.

The T17 located at the Parque Histórico Marechal Manoel Luis Osorio.
Source: Parque Histórico Marechal Manoel Luis Osorio

Conclusion

The Brazilians needed to modernize their Army and the US needed to supply the Brazilian Army with new equipment to strengthen their resolve on the Allied side. The T17 Deerhound seems to have been more of an equipment dump by the US, than military-aid. It is possible that the Brazilian Army may have ordered the T17 themselves, but either way, it was not much of an improvement. The T17 was not loved by its crews, and the mistakes which had made the US reject it were not fixed or were unfixable.

This was Brazil’s first 6 x 6 and it had made Brazil practically the only country in the world to have operated the T17 in regular Army units. Sadly, the T17 Deerhound ended up with an almost equally tragic story within the Brazilian Army, as it had with the US Army. A rejected vehicle, plagued with significant issues, and most of all, overshadowed by the successful M8 Greyhound.

Illustrations

The T17 Deerhound with the pre-1946 marking. Done by Vesp.
The T17 Deerhound with the Cruzeiro de Sul marking. Done by Vesp.
The Tuiuti of the 2º RRecMec. Done by Vesp.
The T17 located at the Parque Histórico Marechal Manoel Luis Osorio. Done by Vesp.
The T17 located at the 1º Parque Regional Manutenção without its main gun. Done by Vesp.
The T17 located at the 1º Parque Regional Manutenção with its main gun, and the T17 located at the Museu de Blindados do Centro de Instrução de Blindados. Done by Vesp.
The T17 located at the Museu Militar do Comando Militar Sul. Done by Vesp.

Specifications (T17 Deerhound)

Dimensions (L-W-H) 5.5 meters x 2.6 meters x 2.3 meters (16.4 feet x 7.5 feet x 7.5 feet)
Total weight, combat loaded 14.5 tonnes (16 US tons)
Crew 5 (Driver, Co-driver, Commander, Gunner, Loader)
Propulsion Two Hercules JXD 6-cylinder in-line 110 hp gasoline engine
Speed (road) 95 kmh (60 mph)
Operational range 400 km (250 miles)
Armament 37 mm M6
.30 M1919A4 machine gun (Hull)
.30 M1919A4 machine gun (Coaxial)
.30 M1919A4 machine gun (Turret top)
Armor

Hull

Front upper 19 mm (0.75 inch)
Front middle 19 mm (0.75 inch)
Front lower 19 mm (0.75 inch)
Side 19 mm (0.75 inch)
Rear 12.7 mm (0.5 inch)
Top 16 to 9.5 mm (0.625-0.375 inch)
Floor 6,5 mm (0.25 inch)

Turret

Front 32 mm (1.25 inch)
Gun mantlet 25 mm (1 inch)
Sides 32 mm (1.25 inch)
Rear 32 mm (1.25 inch)
Top 19 mm (0.75 inch)

Acquired 54

Sources

Ford M-8 Greyhound Exército Brasileiro – Surge o conceito de blindado 6×6 – Expedito Carlos Stephani Bastos
Fiat-Ansaldo CV-3 35 II no Exército Brasileiro – Expedito Carlos Stephani Bastos
Extermine o Inimigo – Dennison De Oliviera
Deerhound – Paulo Roberto Bastos and Hélio Higuchi
Armored Car: A history of American Wheeled Combat Vehicles – R.P. Hunnicutt

https://www.defesabrasil.com/forum/viewtopic.php?t=18372
https://caiafamaster.com.br/destaque/um-seculo-de-blindados-no-brasil-braco-forte-na-defesa-da-patria-aco-no04/
https://ecsbdefesa.com.br/carro-blindado-leve-t-17-deerhound-6×6-um-esquecido-no-exercito-brasileiro/

Categories
Cold War Brazil CCL X1 Cold War Brazilian Armor

XLF-40

Brazil (1976)
Tracked Self-Propelled Multiple Rocket Launcher – 1 Prototype Built

In 1973, Brazil began developing the X1 light tank, which was completed later that year. From there, the vehicle would spawn multiple variants, from bridge-laying vehicles to anti-aircraft vehicles. Another variant of the X1 combined the Brazilian research in rocket development, which had started in 1949, with the Brazilian advancements in the X1 project into a tracked self-propelled multiple rocket launcher vehicle, also known as the XLF-40. With this project, Avibras would gain a more prominent role within the defence industry and it would eventually lead to the renowned ASTROS 2 Artillery Saturation Rocket System.

The XLF-40 exhibited at the Escola Preparatória de Cadetes do Exército (EsPCEx) (English: Army Cadets Preparatory School) in Campinas, São Paulo State, in 1976.
Source: Lançador de Foguetes XLF-40 – A Artilharia Sobre Lagartas

Brazilian rocket development

In 1949, the Escola Técnica do Exército (ETE) (English: Army Technical School) initiated the Brazilian research of rockets, in line with developments from other major countries of the time. The first project was the 114 mm F-114-R/E rocket, which showed promising results. The F-108-R rocket system was then developed in 1956, which could fire multiple rockets and was mounted on a ¾ ton Willys Overland Jeep designated Fv-108-R.

The Fv-108-R Jeep.
Source: Uma realidade brasileira: Foguetes e mísseis no Exército Brasileiro 1949-2012 – Expedito Carlos Stephani Bastos

In 1961, the company Avibras Aerospacial SA was founded in São José dos Campos (SP) by engineers of the Centro Técnico da Aeronáutica (CTA) (English: Aeronautical Technical Center). Avibras would develop Brazil’s first solid synthetic propellant, which would propel them into the rocket and missile industry.

The first major step for Avibras and the CTA was their participation in the Experimental Inter-American Meteorological Rocket Network project or EXAMETNET. This was a project led by the United States to acquire meteorological data for the entire American continent. The US started working together with countries like Argentina and Brazil by providing them with the Arcas rocket to carry out measurements at heights between 20 to 80 km. With Brazil’s participation in the project, the CTA acquired the technology and design of the Arcas rocket and went on to start developing the Sonda 1. The Sonda 1 was a two-stage rocket for which the general idea and technology were copied from the Arcas, but were redesigned for a larger rocket. Although the Sonda 1 itself would not be a success, its design proved fundamental.

Sonda I
Source: https://pt.wikipedia.org/wiki/Sonda_I#/media/Ficheiro:Sonda_I_dimensoes.jpg

In 1965, the CTA transferred the technology of the Sonda rocket to Avibras. With this transfer, Avibras effectively became the most important manufacturer of rockets and missiles in Brazil, as Avibras was responsible for the manufacture of the Sonda 1. After the Sonda 1 project, the CTA started developing the Sonda 2, which was again manufactured by Avibras in the late 1970s. From this point onward, Avibras would, together with the CTA, Instituto de Pesquisas e Desenvolvimento (IPD) (English: Research and Development Institute), and the new Instituto Militar de Engenharia (IME) (English: Military Institute of Engineering), renamed after a merger between the ETE and IMT in 1959, started developing ground-to-ground and air-to-ground rocket systems. One of these rockets was the X-40, which was developed in 1972.

The X-40 was a 300 mm rocket (rockets are unguided, missiles are guided) with a length of 4.45 meters (14.6 feet), weighing 550 kg (1,213 lb), of which a payload of 150 kg (331 lb), and a range of 65 km (40.4 miles). It used a solid propellant as fuel and was manufactured by Avibras. An interesting fact was that this was the first time the Brazilian engineers had used computers to make the calculations for rocket development.

With the development of the X1 family, the promising results of the X-40 rocket, and seeing this as a way to provide more firepower and mobility to the Brazilian artillery units, the IPD initiated the design of a tracked self-propelled multiple rocket launcher, which received the designation Carro de Combate Lançador de Foguetes X-40 (English: Combat Car X-40 Rocket Launcher).

The X-40 rocket at the CTEx in Rio de Janeiro.
Source: FOGUETES NO EXÉRCITO BRASILEIRO 1949 – 2009

The X1 project

The first X1 vehicle was developed and presented at the Brazilian Independence Day Parade on September 7th of 1973. The X1 was a modernization project of the M3 Stuart, carried out by the Parque Regional de Motomecanização da 2a Região Militar (PqRMM/2) (English: Regional Motomecanization Park of the 2nd Military Region), together with Bernardini and Biselli, two Brazilian private companies. The PqRMM/2 was responsible for the development of the wheeled vehicles, but also for the tracked vehicles of the Brazilian Army at the time, and was under the supervision of the Diretoria de Pesquisa e Ensino Técnico (DPET) (English: Army Research and Technical Educational Board), which coordinated the projects.

The tracked vehicles were researched and developed by a team of engineers within the Army and PqRMM/2, which were part of the Centro de Pesquisa e Desenvolvimento de Blindados (CPDB) (English: Centre for the Research and Development of Tanks). The CPDB was a study group of Army engineers which analyzed the possibilities of producing tanks domestically. The first goal was to develop a new family of light tanks using the M3 Stuart as its basis. One of the vehicles which would form part of what we now know as the X1 family, was the XLF-40.

The first X1 during firing trials in 1974.
Source: Blindados no Brasil

The XLF-40

With the success of the X1 project and the completion of the X-40 rocket, the Brazilian Army decided to initiate the development of a rocket system for the X1. The IPD made the first sketches of the Carro de Combate Lançador de Foguetes X-40 (English: Combat Car X-40 Rocket Launcher), which were presented on July 20th, 1976. Further design and construction were immediately initiated in an attempt to build the new vehicle before September 7th of the same year, so it could make an appearance on the yearly Independence Day parade, together with the X1A1 and the XLP-10.

The sketches from the IPD, presented on July 20th 1976.
Source: Lançador de Foguetes XLF-40 – A Artilharia Sobre Lagartas – Expedito Carlos Stephani Bastos

The XLF-40 would receive three different designations during its development, with its proposal calling it Carro de Combate Lançador de Foguetes X-40, which would be simplified to Carro Lançador Múltiplo de Foguetes (Multiple Rocket Launcher Vehicle). Finally, it received the designation XLF-40. The X referred to it being a prototype, the L to Lançador (English: Launcher), the F to Foguetes (English: Rockets), and the 40 to the X-40 rockets used. Eventually, the full name would be Viatura Blindada Especial, Lancador de Foguetes, XLF-40 (VBE LF XLF-40) (English: Special Armored Vehicle, Rocket Launcher, XLF-40).

The development of the XLF-40 would be carried out by multiple companies, of which Avibras, Bernardini, and Biselli were the most important. Bernardini and Biselli were responsible for the conversion of the hull and installation of the suspension, while Avibras manufactured the rockets.

One of the requirements was that all the systems were completely operable from within the vehicle. The aiming and the launching of the rockets were controlled through radio systems. The rockets could be fired independently or in a volley. To provide a better surface to fire from, the XLF-40 had four outriggers, two on each side, which were operated by hydraulic pistons on each leveling system. These outriggers made the XLF-40 a more stable platform to fire from, increasing its accuracy. Another interesting development was the installation of the TRANSIT global positioning system to better locate the vehicle. This GPS system would help the crews to better estimate the firing arcs of their rockets and be more accurate. An M3A1 Stuart hull was selected to be converted to the XLF-40.

The XLF-40 would only be armed with its rockets and personal weapons for the crew, as the machine gun for the co-driver from the M3 Stuart was removed to provide the same dual hatch as for the driver. This meant that the co-driver had a larger space to enter or exit the vehicle. This style of hatches was first used on the X1 prototype vehicle, but would only be carried out on the XLF-40 and the XLP-10 vehicles. The construction of the XLF-40 prototype was completed in less than 2 months and was able to be presented during the September 7th, 1976 Independence Day Parade.

From left to right: X1A1, XLF-40, and XLP-10 on the September 7th, 1976 Parade.
Source: Lançador de Foguetes XLF-40 – A Artilharia Sobre Lagartas – Expedito Carlos Stephani Bastos

XLF-40 hull origin theory

In the X1 article, the writer proposed a theory to what may have happened with the X1 prototype after it was completed. This theory suggests that the hull might have been repurposed. Besides the X1, a bridge-laying vehicle designated XLP-10 and a rocket launching vehicle designated XLF-40 were built. Both these variants would use the two hatch opening for the co-driver instead of a hull machine gun. What is interesting is that the XLP-10’s and all production X1’s used a single front side plate and the XLP-10’s missed a characteristic hook on these plates. The XLF-40, though, used the exact same double front side plates design as the X1 prototype and also offered the hook. Additionally, both the X1 prototype and the XLF-40 were converted from an M3A1 Stuart, identifiable from the rear. Considering the X1 prototype was trialled in 1974, the XLF-40 was built in 1976 and the original Engesa turret of the X1 prototype was repurposed for the EE-9 project, it is very likely they repurposed the X1 prototype hull for the XLF-40 prototype. Just like the prototype turret, this makes perfect sense to not waste an otherwise perfectly fine hull and to cut costs in what was effectively a technology test bed.

A picture with the two plate front side plates encircled in red. This style was exclusive to the X1 prototype as all production vehicles used a single plate.
Source: http://www.gbnnews.com.br/2017/10/bernardini-um-historia-de-expertise-e.html#.YKLIoKHRZ1o & Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivatives

With these arguments, the writer hopes to have sufficiently proved his theory that the X1 prototype hull was repurposed for the XLF-40, but would like to reiterate that this is just a theory and only indirect evidence and photographs point towards this possibility. No direct evidence has been found to verify this theory.

XLF-40 in Detail

The XLF-40 weighed 16.6 tonnes combat-loaded (18.3 US tons) and 15 tonnes (16.5 US tons) without rockets. It was 5.98 meters (19.6 feet) long, 2.74 meters (9 feet) wide, and 2.54 meters (8.3 feet) tall. It had a crew of three, with the driver located on the front left of the hull, the co-driver on the front right of the hull, and the commander probably positioned somewhere under where the turret originally was positioned, although there is no confirmation of this.

The XLF-40 at Conde Linhares Military Museum in Rio de Janeiro.
Source: http://www.gbnnews.com.br/2017/10/bernardini-um-historia-de-expertise-e.html#.YKLIoKHRZ1o

Hull and Armor

The hull of the XLF-40 was a slightly lengthened and modified M3A1 Stuart hull. As such, the overall protection for the XLF-40 hull remained the same as that of the M3. The thickness of the plates which were used to lengthen the hull is unknown. The upper front plate of the XLF-40 had an armor thickness of 38 mm (1.5 inch) at 17 degrees vertical, a middle front plate of 16 mm (0.6 inch) at 69 degrees, and a lower front plate of 44 mm (1.7 inch) at 23 degrees. Its sides were most likely about 25 mm (1 inch) thick. The rear armor and the lengthened parts of the side are unknown. Considering the original Stuart had 25 mm (1 inch) thickness on the sides and rear, it would not be unreasonable to assume that the lengthened structure was about 25 mm (1 inch) thick as well. The top plate would have been 13 mm (0.5 inch) thick and the floor plate would have gradually decreased in thickness from 13 mm at the front to 10 mm (0.5 to 0.4 inch) in the rear (although the thickness for the lengthened structure is unknown).

The rest of the XLF-40 had a very similar layout as the Stuart. It had two headlights, one on each side of the front mudguards, two towing hooks on the front hull, two driver style double hatches and, as a result, no hull machine gun.

The XLF-40 had two hydraulic pistons on the front hull, one on each side. These pistons were fixed on a pivot, which allowed them to turn facing the ground when the pistons were utilized. The feet on which the XLF-40 was stabilized had a rotating bar attached to them and to the hull, which caused the pistons to face the ground as the rod of the piston made a complete stroke.

The front of the XLF-40, note the hydraulic cylinders and the rotating bar attached to the feet.
Source: https://wwiiafterwwii.files.wordpress.com/2019/08/launcher.jpg?w=809

The rear curved plate was altered to make room for the rear hydraulic cylinders. The hydraulic cylinder was mounted to the rear by cutting a hole in the curved M3A1 rear plate and sticking the cylinder through it. All the hydraulics of the XLF-40 were powered by the original M3A1 Stuart hydraulic system.

The rear of the XLF-40, note the curved M3A1 Stuart rear plate and the hydraulic cylinders sticking through it.
Source: https://www.nevingtonwarmuseum.com/uploads/9/1/7/5/9175276/3461844_orig.jpg

Mobility

The XLF-40 was powered by a Scania-Vabis DS-11 A05 CC1 6-cylinder in-line diesel engine. This engine produced 256 hp at 2,200 rpm, giving the vehicle a horsepower per tonne ratio of 15.4. It used the same, but revised and locally produced, 5 forward and 1 reverse gearbox, transmission, and differential as the original Stuarts. The XLF-40 would have a top speed of about 55 km/h (34 mph) on roads, but would most likely be much lower when it was armed with the X-40 rockets. The vehicle had an operational range of 520 kilometers (323 miles).

The XLF-40 used a copied and slightly altered VVS suspension system from the 18-ton M4 artillery tractor. It had 4 road wheels divided over two bogies, with 2 bogies per track, two return rollers on each side, a drive sprocket in the front, and an idler wheel on the rear. The 18-ton M4 suspension gave the vehicle a ground pressure of around 0.59 kg/cm2 (8.4 psi). It had an on-ground track length of about 3.22 meters (10.6 feet) and could cross a trench of 1.2 meters (3.9 feet).

Turret and Armament

The turret was replaced by a single plate on which the rocket frame and the needed hydraulics were mounted. This single round plate used the same 1.6 meters (5.25 feet) turret ring diameter as the rest of the X1 family. On the rear of the plate were two hatches for the crew, located in between the rocket rails.

The rotating plate with the two hatches and the launching platform on top.
Source: Lançador de Foguetes XLF-40 – A Artilharia Sobre Lagartas – Expedito Carlos Stephani Bastos

A frame was built on top of the plate, on which the hydraulic cylinders were located. The rods of these cylinders were fixed to the launching platform so that the rockets could be fired at the needed angle. The launching platform would rest on the frame during travel. Over the years, there seems to have been some development regarding the location of the hydraulic cylinders for the launching platform. The cylinders seem to have been placed much more forward from the launching platform in the early development stages. In later stages, the cylinders seem to have been placed much closer to the hinge point of the launching platform, potentially enabling the rockets to be fired from much steeper angles.

Resting on top of the frame was the launching platform, from which the rockets would be aimed and fired. The frame seems to have been constructed from heavily perforated steel profiles. The holes in the frame were probably meant to save weight, so that smaller hydraulics could be used. The launching platform was 5.5 meters (18 feet) long and between 1.8 to 2.4 meters (5.9 to 7.9 feet) wide. It had three rails from which a rocket could be fired. Each rail had two clamps attached to them in order to clamp the rocket to the rails during travel.

The XLF-40 with its launching platform at its most extreme angle.
Source: https://wwiiafterwwii.files.wordpress.com/2020/09/launcher2.jpg

Initially, the mounting point of the hydraulic cylinder was located in the middle of the launching rails but later seems to have been repositioned towards the rear of the platform due to the relocation of the hydraulic cylinder. The hydraulic cylinders enabled the launching platform to be angled and give the rockets the trajectory to hit their target. The rockets were fired perpendicular from the hull. This was done to provide the launching platform with the needed space to angle the rockets, which is seen to be done at a near 90-degree angle with the rockets aiming almost straight up the sky.

On the left, an XLF-40 firing, and on the right, the XLF-40 at Bernardini. Note the difference in hydraulic cylinder position.
Source: Lançador de Foguetes XLF-40 – A Artilharia Sobre Lagartas – Expedito Carlos Stephani Bastos

The XLF-40 was armed with 3 X-40 rockets. These rockets had a range of 65 km and used solid propellant as their fuel. The rockets were about 4.45 meters (14.6 feet) long and had a diameter of 300 mm. The rockets weighed 550 kg (1213 lb) each with a 150 kg (331 lb) payload. The rockets could be fired both simultaneously and independently from each other. The XLF-40 had no further armament.

Fate

After the XLF-40 was presented in the Independence Day Parade in 1976, Brazilians would continue testing and improving the vehicle until the early 1980s. It would be tested at the Marambaia Proving Ground in Rio de Janeiro, where it would fire its rockets towards the sea.

The XLF-40 would mostly end up as a testbed more than anything else. It would have a few issues, some of them with the launching platform, but these were said to never have been fully resolved. These issues were part of the reason why the project would not be progressed upon further. In 1981, with the knowledge acquired from the XLF-40 project, Avibras developed the ASTROS 1 rocket system for Iraq, which would eventually lead to the successful ASTROS 2 rocket system that is operated by the Brazilian Army, among others. The development of the ASTROS rocket systems probably contributed to the eventual cancellation of the XLF-40 as well.

With the cancellation, the XLF-40 was added to the Conde Linhares Military Museum collection in Rio de Janeiro at an unknown date.

The ASTROS 1.
Source: Uma realidade brasileira: Foguetes e mísseis no Exército Brasileiro 1949-2012 – Expedito
The XLF-40 at Conde Linhares Military Museum in Rio de Janeiro.
Source: http://www.gbnnews.com.br/2017/10/bernardini-um-historia-de-expertise-e.html#.YKLIoKHRZ1o

Conclusion

In the end, the XLF-40 can be described as a testbed for rocket systems for which potential military service would have been a bonus. It incorporated some relatively advanced technologies, such as the TRANSIT GPS, which would go on to enable Avibras to develop a much more advanced rocket system. The Brazilian Army did not seem initially convinced by the potential of rocket systems after the XLF-40. It would take Brazil until the 1990s to buy the ASTROS system, 10 years after its first conception. This might also have been because the need and money were not there for the expensive system.

The XLF-40 was fundamental for Avibras as a company, and paved the way for the successful ASTROS rocket systems, which were sold by Avibras to countries such as Saudi Arabia, Iraq, Brazil and Indonesia, among others. The ASTROS would become one of Brazil’s most successful and lucrative weapon systems, still being ordered to this day.

Illustrations

The XLF-40. done by Ardhya ‘Vesp’ Anargha.

Specifications XLF-40

Dimensions (L-W-H) 5.98 (19.68 feet) x 2.74 (9 feet) x 2.54 meters (8.33 feet)
Total weight 16.65 tonnes (18.35 US tons)
Crew 3 (Driver, Co-driver, Commander)
Propulsion Scania-Vabis DS-11 A05 CC1 6-cylinder in-line 256 hp diesel engine
Suspension Bogie suspension
Speed (road) 55 kph (34 mph)
Operational range 520 km (323 miles)
Armament 3 X-40 Rockets
Armor

Hull

Front (Upper Glacis) 38 mm (1.5 inch) at 17 degrees
Front (Middle Glacis) 16 mm (0.6 inch) at 69 degrees
Front (Lower Glacis) 44 mm (1.7 inch) at 23 degrees
Sides (guess) 25 mm (1 inch)
Rear (guess) 25 mm (1 inch)
Top 13 mm (0.5 inch)
Floor 13 to 10 mm (0.5 to 0.4 inch)

Turret

25 mm (1 inch) allround

Production 1 Prototype

Special thanks to Expedito Carlos Stephani Bastos, the leading expert of Brazilian armored vehicles https://ecsbdefesa.com.br/, Jose Antonio Valls, an Ex-Engesa employee and expert in Engesa vehicles, Paulo Bastos, another leading expert of Brazilian Armored vehicles and the author of the book on Brazilian Stuarts, and Guilherme Travassus Silva, a Brazilian with whom I was able to endlessly discuss Brazilian Vehicles and who was always willing to listen to my near-endless ability to talk about them.

Sources

Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivatives – Hélio Higuchi, Paulo Roberto Bastos Jr., Reginaldo Bacchi
Blindados no Brasil – Expedito Carlos Stephani Bastos
Lançador de Foguetes XLF-40 – A Artilharia Sobre Lagartas – Expedito Carlos Stephani Bastos
Uma realidade brasileira: Foguetes e mísseis no Exército Brasileiro 1949-2012 – Expedito Carlos Stephani Bastos
http://www.lexicarbrasil.com.br/
Personal correspondence with Expedito Carlos Stephani Bastos
Personal correspondence with Paulo Roberto Bastos Jr.
TM 9-785 18-Ton High Speed Tractors M4, M4A1, M4C, and M4A1C – US Army April 1952.
Stuart: A history of the American Light Tank, Volume 1 – R.P. Hunnicutt

Categories
Cold War Brazilian Armor Cold War Brazilian Wheeled Vehicles

VBB-1

Brazil (1969)
Reconnaissance Vehicle – 1 Prototype Built

Up until 1967, Brazil was dependent on foreign countries for armored vehicles. Throughout and in the aftermath of World War 2, Brazil would receive large numbers of cheap armored vehicles from the United States, including the M3 Stuart and the M4 Sherman, as it had entered the war on the Allied side in 1942. In fact, Brazil had not undertaken any tank design since 1932, and those had only been conversions of tractors and cars into armored vehicles during the revolutions of 1924, 1930, and 1932.

Between 1932 and 1958, the Brazilian Armed Forces created a solid basis of technical institutes from which it could educate technical and research personnel. In turn, these helped the Brazilian automotive industry in developing its own automotive parts and helped in opening laboratories for the manufacturers. In 1967, Brazil set up a plan for the country to become more self-sustaining. The flow of US material had decreased because of its entanglement in the Vietnam War and, after a study, Brazil recognised external dependence on arms suppliers as a serious problem for its political position in South America.

The plan to solve this would be the start of the Brazilian defense industry. The first steps were small, from its first tracked armored vehicle meant for serial production in 1965, called the VETE T-1 A-1 Cutia, to its very first wheeled reconnaissance vehicle with production in mind, designated VBB-1 in 1967. The VBB-1 kickstarted the development of wheeled armored vehicles in Brazil, with the EE-9 Cascavel being the most successful result.

The VBB-1.
Source: https://www.lexicarbrasil.com.br/exercito/

Development

The Viatura Blindada Brasileira 1 (VBB-1), (English: Armored Car of Brazil 1) was developed by the PqRMM/2 (Parque Regional de Motomecanização da 2a Região Militar, Regional Motomecanization Park of the 2nd Military Region), which was a group of Army automotive engineers gathered to study, develop and produce armored vehicles for Brazil. The PqRMM/2 developed its vehicles under the supervision of the Diretoria de Pesquisa e Ensino Técnico do Exército (DPET), (English: Army Directorate of Research and Technical Education). The PqRMM/2 was the birthplace of many of the concepts that resulted in the EE-9 Cascavel and EE-11 Urutu, among others. The first steps of the PqRMM/2, meant to gain experience, was the remotorization of vehicles like the M8 Greyhound and the M2 half-track, which received a diesel engine.

From the experience gained, the PqRMM/2 team initiated the development of a wheeled armored vehicle for reconnaissance. The reason for the PqRMM/2 to develop a wheeled vehicle was because of a study carried out by the Diretoria Geral de Material Bélico (DGMB), (English: General Directorate of War Material), which called for the intensive adoption of wheeled armored vehicles for the Brazilian Army, after having studied wheeled vehicles from various countries. These types of vehicles needed less investment, and were more feasible to develop instead of importing them. The study called for a vehicle like the M8 Greyhound, but simpler.

The reason why the DGMB wanted a vehicle like the M8 Greyhound is because of the experience Brazil had during World War 2 with the vehicle. Brazil sent an expeditionary force, also known as the Smoking Snakes, to fight in Italy alongside the Allies. The Brazilians would operate the M8 during the Italy campaign, and they loved the vehicle. The positive experience with the M8 caused it to be one of the, if not the most impactful vehicles for Brazilian development of armored vehicles. As a result, most of the important wheeled vehicles and the wheeled vehicle program can trace back their roots to the M8 Greyhound during the Italian campaign. The most well known Brazilian vehicle that was based on the M8 Greyhound, albeit heavily improved, was the EE-9 Cascavel.

Early designs

In 1967, the DGMB made a sketch of a 4 x 4 vehicle, armed with a 37 mm cannon which was mounted in a rotating turret. The vehicle needed to have a crew of 3 to 4 members, and was to be sufficiently robust and powerful as the M8, but simpler. This was requested in order not to overburden the PqRMM/2 team more than what they could achieve. The DGMB requirements were passed on to the higher-ups of the Army, which officially collected it under Officia 372, a requirement study for the PqRMM/2 to work from. Further demands were the use of as many off-the-shelf components as possible, in order to profit from the Brazilain automotive industry and to save costs (this would be a common theme for almost all of Brazil’s wheeled vehicles). In addition, the turrets were to be re-used from the obsolete T17 Deerhounds, of which Brazil owned 54 at the time. Finally, the plan was for the chassis to eventually be modified to suit APC, anti-infantry, and anti-air roles.

Sketch of the VBB-1 made by the DGMB in 1967.
Source: Blindados no Brasil

The concept of the 4 x 4 VBB-1 was inspired from the Belgian FN 4RM 62F Auto Blindée. This was one of the vehicles which was studied by the DGMB. Although the VBB-1’s concept was based on the Belgian vehicle, the guns were different. Brazilian doctrine at the time called for the usage of 37 mm guns on reconnaissance vehicles. It can be questioned to some extent if the DGMB might have been stuck in its ways regarding Brazil’s doctrine on the 37 mm, but on the other hand, the VBB-1 was never meant to be groundbreaking or match to its counterparts of the period. Although the concept was based on the Belgian vehicle, the overall design of the VBB-1 seems to have taken most of its inspiration from the M8 Greyhound.

In July 1968, the team led by Lieutenant-Colonel Pedro Cordeiro de Mello, who was the leader of the PqRMM/2, started designing the VBB-1. It would have a 4 man crew and carry spare tires on the sides of its hull. Somewhere around this time, the spare T17 Deerhound turrets got ditched from its development. The reason why is not confirmed by sources. It could be that the development team decided that, while developing a new vehicle with serial production in mind, designing it to mount a turret of which just 57 are available might not be the best decision. It was better to take advantage of the steel foundries and contract a factory to develop turrets. This would give the Brazilian industry experience with turret manufacture and gain another step towards independence. In July of 1986, the first scale model mockup was built. An interesting detail of this model is the complicated raised hull structure towards the turret. Another important detail are the spare tyres mounted on both sides in the middle of the vehicle.

First model of the VBB-1.
Source: Blindados no Brasil

A second model was made, which already simplified the hull construction a bit, and removed the spare tyres in the middle of the first model, replacing them with a continuous side armor plate instead. This was most likely done as the next step within the development of the VBB-1, as the PqRMM/2 had requested the development of so-called bullet-proof tyres, which would theoretically render the spare tyres obsolete in the grand scheme of operations. But it remains unclear if this model was designed with the bullet-proof tyres in mind, or if this model was designed alongside the first model as a proposal.

The model without the spare tyres.
Source: Blindados no Brasil

Development of indigenous run-flat tyres

On June 3rd 1968, Lieutenant-Colonel Mello requested the development of bullet-proof tyres known in Brazil under the acronym P.P.B. (Pneus à Prova de Balas), or run-flat tyres. These tyres were developed by Novatração and would be used for the VBB-1. The selected size of the VBB-1’s tyres was 9.00-20, which was the same size as those of the M8 Greyhound. The tyres were thus interchangeable and the prototypes were extensively tested on the M8’s. The first tyre was developed 3 months after the initial request, and used an outer protective tyre and a separate inner wall. The outer and inner tyre were pushed against the rim lips with an inner rubber ring, also known as a separator. Due to heating issues when used continuously for over 200 km (124 miles), the tyres were rejected.

The next step was a critical development for Novatração. Instead of using an inner tyre, Novatração decided they could use the outer tyre as the inner tyre and the separator ring as a run-flat tyre. This meant that if the outer tyre was punctured, the vehicle could still keep on driving on the separator ring. Another advantage was that crews could now easily field repair any puncturing without the need of removing the wheel from the axle and the outer tyre from the wheel, in order to be able to fix the punctured inner tyre. The new tyre was extensively tested from March 1969 on, and could travel for at least 500 km (311 miles) after it was punctured. Interestingly, the tyre was also tested for a year without any air in the tyre or repairs to the tyre, the tyres held up for 1,200 km (746 miles). The tyres were accepted and delivered in October 1969 to the PqRMM/2. Although the VBB-1 already received its run-flat tyres around March or April of 1969, as a picture dated April 1969, shows a VBB-1 with run-flat tyres.

The VBB-1 tyre on the left and its design by Novatração on the right, note the single outer tyre and the separator around the rim.
Source: Blindados no Brasil

Turret development

Parallel to the development of the tyres was the development of the turret. The initial idea of reusing T17 Deerhound turrets had been ditched, and the PqRMM/2 team opted for a locally produced turret. Sources do suggest that the 37 mm cannons of the T17 Deerhounds were used for the manufacture of the turrets. The new turret was practically a somewhat improved copy of the M8 Greyhound turret. The turret was cast by Fundições Alliperti S/A from SAE 5160 steel, and was further machined by the company Avanzi.

Various gun mantlets were cast by Alliperti and presented on October 25th 1968, along with other components of the turret. A simple gun mantlet with just the main gun hole and a vision hole was selected. This was a simpler gun mantlet than the M8 Greyhound’s mantlet, which was also proposed. Another important difference was that the turret would receive two hatches, instead of an open-top turret like the M8, and it also received a mount for a .50 calibre machine gun in front of the turret hatches. Alliperti produced 8 turrets in total.

Components of the turret and 2 of the proposed gun mantlets. On the left side, an M8 Greyhound like mantlet, and on the right, the simpler mantlet. The simpler mantlet was selected with an extra hole to the side of the 37 mm hole for direct vision purposes.
Source: Ford M-8 Greyhound no Exército Brasileiro

Hull

After the construction of the initial models, work began on building a steel scale model. This steel scale model would start showing clear features from the M8 Greyhound, with the driver and assistant driver’s hatch style being the most notable. The overall shape of the hull, especially the part towards the turret, seems to have been somewhat simplified. A very important detail is the armor values written on the sides of the steel scale model. These values are exactly the same thickness of 3/8 inch (9.5 mm) as the M8 Greyhound’s side armor plates. This might suggest that the overall armor values of the VBB-1 are the same as the M8 Greyhound armor values.

The steel scale model with the armor values written on the plates.
(This picture has been accredited to both the VBR-2 (a 6 x 6 project of the PqRMM/2) and VBB-1 by the writer Expedito Carlos Stehpani Bastos, but after asking the writer himself, he confirmed it was a scale model of the VBB-1, and not the VBR-2.)
Source: Blindados no Brasil

With the initial models and the steel reference scale model completed, work began on the construction of the hull somewhere between July and October 1968. The hull was constructed by the company Trivellato. It reached an advanced stage on October 25th, 1968, when it was photographed. Interestingly, at this point in time, the hull was constructed in accordance with the run-flat tyre concept. However, it is known that the VBB-1, of which a single vehicle was built, was initially delivered as per the spare tyre concept. The first more or less finished vehicle with run-flat tyres was photographed in April 1969, and the first run-flat tyres were made in March 1969. As the hull was initially constructed with the run-flat design, it seems that the PqRMM/2 team decided that it would use the spare tyre concept and cut the side parts of the hull for the spare tyres to be mounted. Somewhere in the early months of 1969, the spare tyre concept vehicle had been delivered, as it was presented to the Army in 1969, and early shooting tests were carried out in 1969, with both vehicles.

Why the PqRMM/2 team decided to cut the sides of the hull for the spare tyres and not wait until the run-flat tyres were delivered, is unknown. It is likely that they wanted to get the vehicle done, and the first set of tyres developed by Novatração did not meet the requirements. They probably weighed the chances of Novatração developing a tyre within specifications and the PqRMM/2 team being able to finish the first concept of the vehicle. With Novatração not having developed a new tyre yet, they went on to develop the spare tyre concept. In addition, an argument can be made that, even though Novatração would have developed a new tyre in time, nothing assured the PqRMM/2 team that that tyre would be significantly better. As converting it back to the run-flat concept would only entail removing the spare tyre mount and welding some extra plates to the side of the hull, the team probably decided that going through with the spare tyre concept was more effective.

The hull which is dated on October 25th 1968. Note the Greyhound tyres.
Source: http://www.geocities.ws/militaryzone_portugal/vbb.htm

The spare tyre concept

When the first version of the VBB-1 with the spare tyres on the side was finished is unknown. It is estimated that it was finished somewhere in between January 1st and March 1969. The reason is because the spare tyre vehicle was presented to the Army in 1969, and shooting tests were carried out with the VBB-1 in this configuration, but in March 1969, the first run-flat tyres were developed and the run-flat concept was first photographed in April 1969.

VBB-1 presented to the Army in 1969.
Source: http://www.geocities.ws/militaryzone_portugal/vbb.htm

Most of the components used for the VBB-1 seem to have been in advanced stages in October 1968. The turret was almost done, the hull was also nearing completion, and the engine was installed in the vehicle as well. Like the VETE T-1 A-1 Cutia before it, and many vehicles after it, the VBB-1 was built with components from numerous private companies. Mercedes-Benz was one of the most important companies involved in the development of early wheeled armored vehicles. Mercedes-Benz Brasil had provided the M8 Greyhounds with new diesel engines, transmissions and differentials during the first stages of the PqRMM/2. For the VBB-1, Mercedes-Benz would again deliver the diesel engine, transmission and a specially developed differential. The differential was an off-center differential which was specially designed by Mercedes-Benz for the VBB-1 project.

Company Component(s)
Mercedes-benz Engine, transmission, differential and other components
Trivellato Hull
Fundições Alliperti S/A Turret
Avanzi Turret
Novatração Run-flat tyres
Engesa Transfer box
Colméia Radiators
MANN Filters
ZF Friedrichshafen Hydraulic steering
DF Vasconcelos Optics
The VBB-1 spare tyre concept.
Source: Blindados no Brasil

The completed VBB-1 with spare tyres was presented to the army in the first quarter of 1969. Almost immediately after it was delivered, the armament and the vehicle were tested. If the tests included anything more than just firing is unclear. It can be expected that it was at least briefly tested and that it performed well enough for the project to carry on. In March 1969, the run-flat tyres from Novatração were finished and, in April 1969, the first picture of the VBB-1 without spare tyres was made.

Firing tests carried out in the first quarter of 1969.
Source: http://www.geocities.ws/militaryzone_portugal/vbb.htm

Run-flat tyre concept

With the development of the run-flat tyres in March 1969, the now finalized VBB-1 was presented in April 1969 in front of the Mercedes-Benz factory in São Paulo. The pride of Mercedes-Benz, or at least their attempt to capitalize on their participation with these Army projects, was shown in the form of a photo album which they had made. This photo album contained pictures of the M8 Greyhound that Mercedes had modernized, and pictures of the VBB-1. Mercedes-Benz Brasil would continue delivering its engines to the rising Brazilian defense industry, which would find their way into the EE-9 Cascavel, EE-11 Urutu, EE-3 Jararaca, and in trucks used for military purposes.

The completed VBB-1 in front of the Mercedes-Benz factory. On the left, a director of Mercedes-Benz Brasil. On the right, Lieutenant-Colonel Pedro Cordeiro de Mello, the leader of the project.
Source: http://www.geocities.ws/militaryzone_portugal/vbb.htm

The VBB-1

The VBB-1 weighed 7 tonnes (7.7 US tons) and was 5 meters (16.4 feet) long, 2.5 meters (8.2 feet) wide, and 2.3 meters (7.55 feet) tall excluding the turret mounted .50 calibre machine gun. Since the VBB-1 was inspired by the M8 Greyhound, its crew was positioned in a similar manner and it is most likely that the crew had the same tasks as in the M8. The VBB-1 was operated by a four-man crew, consisting of the Commander, Gunner, Driver, and Co-driver. The role of loader was most likely carried out by the Commander, like in the M8. The Co-driver would function as a Radio-operator, but if the VBB-1 ever had a radio set installed is unknown.

The VBB-1.
Source: Blindados no Brasil

The hull

The hull was manufactured of steel plates which were welded together. The VBB-1 had a similar style of hull/hatch construction to the M8 Greyhound for the Driver and Co-driver. In a way, the hull can be seen as two parts. A single large and relatively simple bottom hull, and a more complicated structure on top which contains the hatches for the Driver and Co-driver, and on which the turret is mounted.

Picture depicting the simple bottom hull and the more complicated top construction.
Source: Blindados no Brasil

The armor of the VBB-1 is unknown. If the PqRMM/2 team took over the side armor values of the steel mock-up is unknown. However, considering the values of the mock-up, which are the same as the M8 Greyhound, and Brazil’s relationship with the M8, it can be theorized that the armor values of the VBB-1 would be somewhere around the M8’s. The VBB-1’s frontal plate was well angled, at around 60 degrees from vertical. Its sides were flat, but started to angle heavily inwards on the bottom of the hull. The rear armor was practically flat. The more complicated structure of the upper hull used steel plates in complicated and unusual angles, especially on the front part of the hull attached to the sides of the Driver and Co-driver compartment. An interesting pyramid like shape was welded on the left hull side of the vehicle. This was most likely done to protect the spare tyres from frontal fire, and was retained during the conversion to the run-flat concept. It would be probable that this unusual pyramid shape would be either altered or removed altogether if the VBB-1 was ever produced, as its role for the protection of spare tyres was no longer needed and it would have been an overly complicated structure to construct in mass-production.

An example of the complicated angling of steel plates, with this plate being angled inwards, leaving an unusual cavity.
Source: Blindados no Brasil

The driver was positioned on the front left side of the vehicle, and the Co-driver on the right. The turret was located in the middle of the vehicle, and the engine in the rear. The VBB-1 had 2 front lights on both sides, and a black-out light on the left side, next to the front light. On the right side of the hull, the vehicle had a .30 caliber machine gun in a ball mount which was used by the Co-driver. It had a horn and something that resembled an antenna next to the Co-driver’s hatch on the right side of the hull. Behind the horn, the VBB-1 seems to have had pioneer tools. On the rear hull, the VBB-1 had a set of rear lights, including black-out lights.

Mobility

The VBB-1 was powered by a 6-cylinder OM-321 120 hp diesel engine built by Mercedes-Benz. This gave the vehicle a top speed of 90 km/h, with an operational range of 1,200 km (746 miles). It had a turning radius of 7 meters (7.7 yards), and could drive up a 60% slope. The transmission and differential were also produced by Mercedes-Benz, while the transmission box was built by Engesa. The VBB-1 used hydraulic steering.

The OM-321 engine mounted in the VBB-1 in late 1968.
Source: http://www.geocities.ws/militaryzone_portugal/vbb.htm

The vehicle was a 4×4, which meant that every wheel would support, very roughly, about 1.75 tonnes (1.93 US tons). The VBB-1 used 4 run-flat tyres, which were developed and made by Novatração. They were about 1 meter in diameter and used the 9.00 x 20 tyre size, which was also used for the M8 Greyhound.

Turret

The VBB-1 used an altered copy of the M8 Greyhound turret. In contrast to the M8, the VBB-1 turret was not open topped. It had a small plateau on the front side, upon which the mount for the .50 calibre machine gun was installed. Behind, two hatches were installed which folded open to the front. On the sides and the rear, the turret had vision blocks which could fold open if needed. The armor of the turret is unknown. Since it was a copy of the M8 turret, it can be expected that the thicknesses of the armor were potentially the same.

The VBB-1 Turret.
Source: http://www.geocities.ws/militaryzone_portugal/vbb.htm

An important development that the VBB-1 brought was the development and study of armor. Somewhere between 1969 and 1970, the DPET and the Instituto de Pesquisas Tecnológics (IPT) (English: Institute for Technological Research) would test the VBB-1 turret by firing at it with .50 calibre and 37 mm ammunition. The 37 mm cannon was fired at a distance of 500 meters (547 yards) and the .50 calibre at both 250 and 500 meters (273 and 547 yards). The 37 mm and .50 calibre from 500 meters (547 yards) were fired at the front of the turret, and the .50 calibre from 250 meters (274 yards) at the side of the turret. The turret armor managed to withstand both armaments.

The tested turret. Hits from 1. the 37mm cannon, 2. the .50 calibre from 500 meters, and 3. the .50 calibre from 250 meters.
Source: http://www.geocities.ws/militaryzone_portugal/vbb.htm

Armament

The VBB-1 used a 37 mm M6 cannon as main armament, which potentially came from the T17 Deerhound. The 37 mm M6 had a total length of 2.1 meters (6.9 feet) and a bore length of 1.98 meters (6.5 feet). The 37 mm cannon was able to fire the M51 APC round with 53 mm (2.1 inch) of penetration at 455 meters (500 yards) at a 30 degree angle, and 46 mm (1.8 inch) of penetration at 915 meters (1,000 yards) at a 30 degree angle. It could also fire the M74 AP, M63 HE, and M2 canister rounds. In addition to the 37 mm cannon, the VBB-1 mounted a .30 calibre M1919A4 machine gun on the right side of the hull, operated by the Co-driver, and a .50 calibre M2 machine gun on top of the turret. The available ammunition of the VBB-1 is unknown.

Fate

The VBB-1 was extensively tested during 1969 and 1970. It performed in beach trials, mobility trials, and firing tests. The vehicle performed well, but in the end would not be accepted. The reason is because the Brazilian Army wanted a 6×6 vehicle like the M8 Greyhound, and not a 4×4.

From left to right: Beach testing, tests in 1970, mobility test, and shooting tests.
Source: Blindados no Brasil and http://www.geocities.ws/militaryzone_portugal/vbb.htm

Why the PqRMM/2 developed a 4×4 instead of a 6×6 is a mystery. They most likely developed a 4×4 because it was easier and cheaper to build than a 6×6, and thus an excellent vehicle from which to gain experience. The PqRMM/2 briefly considered cutting the VBB-1 and lengthening the hull to create a 6×6 vehicle, but the idea was almost immediately discarded. It was easier and more effective to develop a new vehicle. One of the 8 VBB-1 turrets that were made was briefly used on the CRR prototype, which was a prototype of the EE-9 Cascavel. The VBB-1 is currently used as a gate guardian in front of the Centro Tecnológico do Exército (CTEx) (English: Army Technology Centre). Note that the VBB-1 presented at the CTEx seems to have a different gun than the VBB-1 originally had. It looks like a mock-up on which tubes are screwed together. Considering the state of the VBB-1, it is not unlikely that the 37 mm was removed.

The VBB-1 as a gate guardian at the CTEx. Note the missing vision block on the side of the turret.
Source: https://www.lexicarbrasil.com.br/exercito/

Conclusion

Overall, the VBB-1 seemed to have been a decent vehicle. It performed well in tests, but was outdated from its conception. The VBB-1 did not present anything new and was not better than its counterparts of its time. This is not surprising considering the goal of this project, the lack of experience of the engineers, and taking into account that this was the very first wheeled armored vehicle Brazil had ever developed with serial production in mind.

The Brazilian Army did not want the VBB-1, but a 6×6 instead. The development of the VBB-1 was critical for the future developments of the PqRMM/2 team and the future Brazilian defense industry. Not only did it give the engineers the experience to develop a 6×6 vehicle with a better hull design but, more importantly, it started the development and research of armor and the development of run-flat tyres. The VBB-1 was, most importantly, a vehicle which helped advance the development of Brazilian armored vehicles, and would be the stepping stone towards the famous EE-9 Cascavel and the EE-11 Urutu.

Illustrations

The VBB-1 spare tyre concept. Illustration done by Cut_22.
The VBB-1 run-flat tyre concept. Illustration done by Cut_22.
The VBB-1 as a gate guardian at the CTEx. Illustration done by Cut_22.

Specifications VBB-1

Dimensions (L-W-H) 5 m x 2.5 m x 2.3 m (16.4 feet x 8.2 feet x 7.55 feet)
Total weight 7 tonnes (7.7 US tons)
Crew 4 (Driver, Co-driver, Gunner, Commander)
Propulsion Mercedes-Benz 6-cylinder OM-321 120 hp diesel engine
Speed (road) 90 km/h (56 mph)
Armament .30 caliber machine gun (Hull)
.50 caliber machine gun (Turret top)
37 mm M6 cannon
Armor Unknown, probably somewhere in the region of the M8 Greyhound
Production 1 prototype

Special thanks to Expedito Carlos Stephani Bastos, the leading expert in Brazilian vehicles, please visit his website for further reading on Brazilian vehicles: https://ecsbdefesa.com.br/, and Guilherme Travassus Silva, a Brazilian with whom I was able to endlessly discuss Brazilian Vehicles and who was always willing to listen to my near endless ability to talk about them.

Sources

Personal correspondence with Expedito Carlos Stephani Bastos
Blindados no Brasil – Expedito Carlos Stephani Bastos
Ford M-8 Greyhound no Exército Brasileiro – Expedito Carlos Stephani Bastos
Armored Car – A History of American Wheeled Combat vehicles – R.P. Hunnicutt
Armor Magazine 1973 Jan-Jun
http://www.geocities.ws/militaryzone_portugal/vbb.htm

Categories
Cold War Brazil CCL X1 Cold War Brazilian Armor

CCL X1A2 Carcará

Brazil (1977/1978-1994)
Light Tank – 24 Built

At the beginning of the 1970s, the Brazilian Army started developing armored vehicles. They would start with wheeled vehicles. After having successfully developed the prototype concepts which would become the EE-9 Cascavel and the EE-11 Urutu, the Brazilians looked to tracked vehicles. Like the previous wheeled vehicle projects, the engineers started small. They first set off remotorizing readily available M3 Stuarts, and then started developing the vehicle that is known as the X1 light tank. The X1 was a modernization of the Stuart which was armed with a low-pressure 90 mm gun and would be developed into an entire family of vehicles.

An attempt to improve the X1 by fixing some of its design flaws was unsuccessful. The X1A1 was developed to improve on the X1, but in the process only got worse. It was too long and too narrow, which made steering a very difficult task. An extensive rebuilding program would have been required to bring the X1A1 to a usable state, something which was simply not worth it. Considering that both the X1 and X1A1 used the now 30 years old M3 Stuart as their basis, some of the flaws would never have been able to be fixed because of the age of the vehicles.

As a result, it was decided that the development of a completely new tank was the way forward. Capitalising on the experiences gained from the X1 and X1A1 projects, the designated X-15 project would use components and design principles from the previous conversions. It would, for example, use the suspension of the X1A1, but also the X1A1’s turret for the first prototype. The resulting tank of the X-15 project would be known as the X1A2 and be the first (and so far only) serially produced tank which was fully designed in Brazil and used in active service.

The X1A2.
Source: Image Caiafa

The X15

It is suggested that the development of a new nationally designed light tank began quite early. The exact date is unknown, but it might very well already have started with the development of the X1 in 1973, and might have really started to take steps after the failure of the X1A1. Somewhere during the project’s life, the vehicle received the X1A2 designation, most likely when it was decided that the X15 would use components from the X1 series.

The X1A1 in 1976.
Source: https://wwiiafterwwii.wordpress.com/2020/10/18/strange-stuarts-of-brazil/

Nevertheless, the Centro de Pesquisa e Desenvolvimento de Blindados (CPDB) (English: Centre for the Research and Development of Tanks), and the Instituto de Pesquisas e Desenvolvimento (IPD) (English: Research and Development Institute) were studying a light tank concept with two main goals in mind. The first was to abandon the overhaul and the conversion process of the M3 Stuart, which was a laborious task and reached its limit for the goals of the CPDB. The second goal was to create a vehicle which was able to steer properly.

The resulting project was designated X15, with the 15 referring to its planned weight of 15 tonnes (16.5 US tons). To save costs and time, the engineers decided that it would be best to take advantage of the efforts already made by integrating components from the X1 projects in the X15 design. The suspension and turret of the X1A1 were carried over, alongside other components. It supposedly had the same Scania diesel engine as the X1 and X1A1, but with improved horsepower from 260 hp to 280 hp.

The hull would keep many features from the X1A1, but feature an improved armor design with better ballistic shapes for the front hull. The X1A2’s hull was also wider than its X1 predecessors, from 2.4 meters to 2.6 meters (7.9 to 8.5 feet). This widening of the hull would result in a significant improvement in the overall mobility of the X1A2. The X1A2 also featured an Allison CD-500 transmission instead of an M3 Stuart or 18-ton M4 tractor transmission.

CD-500 transmission.
Source: TM 9-1730B – Maintenance Cross-Drive Transmission model CD-500

The X1A2 prototype

The exact date for when the first X1A2 prototype was finished is unknown, but there is proof that the X1A2 prototype hull was nearing completion in July 1978. Considering that a Deputy Chief of the Brazilian Army suggested the interruption of the X1 Pioneiro production for the X1A2 in July 1978, it can be reasoned that the X1A2 prototype was built between July 1977 and July 1978. As mentioned, this prototype integrated the suspension, turret, gun, and engine of the X1A1, while also using new components and design features to fix the issues of the X1A1. It was tested by the Parque Regional de Motomecanização da 2a Região Militar, (PqRMM/2) (English: Regional Motomecanization Park of the 2nd Military Region), after completion. After testing, the vehicle seems to have been accepted and the design of the production version was initiated.

The X1A2 prototype with the French DEFA D-921 gun. Note IPD and CPDB written on the side.
Source: Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivatives

The production version differed in some significant ways from the prototype. While the prototype seems to have had a 4-man crew, considering 2 sets of sights were installed on both the driver’s and co-driver’s side, the production version only had a set of sights for the driver. In addition, the hull machine gun was also removed. The now vacant space of the co-driver was supposedly filled with additional 90 mm ammo racks. Besides the removal of the co-driver role, the production version X1A2 was also armed with an EC-90 gun.

The EC-90 was a license-produced low-pressure 90 mm gun by Engesa. This gun was based on the Cockerill Mk.3 gun. The switch from the French DEFA (Direction des Études et Fabrications d’Armament) (English: Directorate of Armament Studies and Production) D-921 gun to the EC-90 had multiple reasons. The main reason was that the French company SOFMA (Société Française de Matériel d’Ármament) (English: French Society of Armament Materiel) would only sell their D-921 guns together with the turret, while the X1 family used a local design. The license production of the EC-90 gun made the X1A2 cheaper to produce. In addition to manufacturing costs, the Brazilian Army only operated their EE-9 Cascavels armed with the EC-90. The adoption of the EC-90 on the X1A2 would simplify logistics as well.

The same X1A2 prototype from a different angle, note the two sets of periscopes.
Source: Blindados no Brasil

Production

The X1A2 was produced in two production batches, with the first consisting of 10 vehicles and the second of 14 vehicles. Of these batches, only the first would enter active service, while the second batch mostly ended up as gate guardians and monuments. The first batch X1A2 was officially designated as Viatura Blindada de Combate – Carro de Combate MB-2 (VBC CC Medio Bernardini-2) (English: Armored Fighting Vehicle – Combat Car Medium Bernardini-2), while the second batch was designated as Viatura Blindada de Combate – Carro de Combate MB-2A (VBC CC Medio Bernardini-2A) (English: Armored Fighting Vehicle – Combat Car Medium Bernardini-2A). The reason for this difference was because the second batch used more locally produced components and featured a swing arm for the .50 machine gun, instead of a fixed mount. Interestingly, this swing arm seems to have been incorporated in the X1A2 prototype, but not on the first production batch.

Considering the X1’s similar designations, it would most likely have also been referred to as the Carro de Combate Leve X1A1 Carcará (CCL X1A1 Carcará), (English: Light Combat Car X1 Carcará), but this is more of an educated guess that cannot be actually confirmed. The Carcará was an indigenous crested hawk and was previously the nickname of the X1A1. The nickname most likely carried over from the X1A1 to the X1A2 because the X1A1 project was unsuccessful, and the X1A2 carried over many aspects from the X1A1.

A Carcará hawk.
Source: https://www.britannica.com/animal/caracara

The first production batch was delivered to the 6th RCB in Alegrete, Rio Grande do Sul State, where they would replace a squadron of M4 Shermans. The 6th RCB was the only unit to ever operate the X1A2.

The swing arm.
Source: Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivatives

Bernardini

For the construction of the X1A2, multiple parties and companies were involved. The most important company which built the X1A2 was Bernardini. Bernardini initially manufactured truck bodies and value transport vehicles, and came in contact with the Brazilian Armed Forces by manufacturing trucks for the Brazilian Marine Corps and the Army. With Bernardini being a manufacturer of safes and armored doors, they were requested by the Brazilian Army to help build the X1. After the X1 was successfully developed, Bernardini started developing the X1A2 together with the PqRMM/2 and the CPDB engineers.

Company/Army Component(s)
Bernardini Most likely: hull, turret, engine installation, equipment installation, track mounting and suspension
CSN Steel
Novatração Tracks
DF Vasconcelos Periscopes
Scania-Vabis Engine
Engesa EC-90 90 mm gun
PqRMM/2 Design support and testing
X1A2 during ramp tests at the PqRMM/2.
Source: Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivatives

The X1A2

Multiple characteristics are presented incorrectly in the book Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivatives and the Tecnologia Militar Brasileira Magazine. As a result, all the length values were calculated with ratios and are reasonable estimates. Most of the other values are rough estimates. The X1A2 weighed 19 tonnes (21 US tons) and the hull was about 6.06 meters (19.8 feet) long, 2.6 meters (8.5 feet) wide, and 2.45 meters (8 feet) tall. It had a crew of three, with the driver located on the front left of the hull, the commander/loader on the left side of the turret, and the gunner on the right side of the turret.

An X1A2 of the 6th RCB on a 7 September parade in Alegrete.
Source: Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivatives

Hull

The hull of the X1A2 was a completely new design with an improved ballistic shape on the front hull, compared to the Stuart based X1s. The overall hull design still bore much resemblance to the M3 Stuart in general design aspects. The thickness of most of the armor is unknown but is expected to not differ too much from the original M3 Stuart thicknesses. The frontal armor is said to be 50 mm (2 inch) thick but it is unknown if this is for the entire frontal hull. Most of the upper hull was protected by a 50 mm plate angled at about 60 degrees from vertical. On top of that was a small strip of armor right behind the drives periscopes, which slightly extended upwards. The thickness of this plate is unknown, but might also have been 50 mm angled at about 60 degrees from vertical. The lower hull plate is also estimated to have been 50 mm thick and was angled at about 45 degrees from vertical. Under the lower hull plate was another lower hull plate which was probably the same 50 mm thick but angled at about 60 degrees from vertical.

The side, rear, top, and floor armor are unknown, but probably did not differ much from those of the original Stuart, and are thus estimated to have been 25 mm thick. The rear armor is also estimated at 25 mm thick (1 inch). The top plate is estimated to have been about 13 mm thick (0.5 inch), and the floor plate between 13 mm to 10 mm thick (0.5 to 0.4 inch). What is known about the bottom plate, is that it is a dual plate against mines. These values are nothing more than the most likely estimations.

The X1A2 had a headlight on both fenders and a horn on the left fender. It seems that the large upper hull plate was also the access hatch to the Allison CD-500 transmission. It could be bolted loose and subsequently lifted from its position. The sides of the hull were used to mount pioneer tools and were also composed of integrated storage boxes. The X1A2 presents a large lifting hook on both sides of the side engine plate at the rear. On the left fender was presumably another storage box and the exhaust was located on the right rear fender. On the top rear hull were two hatches to access the engine and, in front of those, what looks like an air inlet grill for the engine.

The front hull, note the hatch for the CD-500 transmission.
Source: http://www.primeportal.net/tanks/gino_marcomini/x1a2_carcara/

Mobility

The X1A2 was powered by a Scania-Vabis DS-11 6-cylinder in-line 280 hp diesel engine. It used a three speed Allison CD-500 transmission, the only vehicle of the X1 family to use a different transmission than either the M3 Stuart or 18-ton M4 Tractor transmissions. The X1A2 had a top speed of potentially 60 km/h (37 mph) on-roads, 30 km/h (18 mph) off-road, 15 km/h reverse (10 mph), and an on-road operational range of 600 kilometers (373 miles) and off-road of 350 km (217 miles).

The X1A2 used a copied and altered Vertical Volute Spring Suspension (VVSS) system of the 18-ton M4 artillery tractor. It had 6 road wheels divided over three bogies, with 3 bogies per track, 3 return rollers on each side, a drive sprocket in the front and an M4 Sherman idler wheel on the rear. The newly designed 18-ton M4 Tractor/M4 Sherman hybrid suspension gave the X1A2 a ground pressure of 0.63 kg/cm2 (9 psi). The vehicle could climb a 0.8 meter (2.6 foot) vertical obstacle, and a hill at an angle of 40 degrees. The X1A2 had an on ground track length of about 3.66 meters (12 foot) and could cross a trench of 2.1 meters (6.9 foot).

The 18-ton M4 Tractor/M4 Sherman hybrid suspension. Note the M4 Sherman idler and the three sets of bogies.
Source: http://www.primeportal.net/tanks/gino_marcomini/x1a2_carcara/

Turret

The X1A2 turrets were practically the exact same turrets as the X1A1 turret. The front turret was armored with 25 mm (1 inch) thick steel plates at various angles to protect it from .50 caliber machine gun fire at 200 meters (218 yards). The rear parts of the turret were armored with 12.5 mm (0.5 inch) thick steel plates. It is suggested that the overall turret layout and the internal turret construction and components were more or less copied from the French H-90 turret. It had the exact same turret ring and its overall shape seems to match the H-90. In addition, in the first BT-90 turret of the X1, a lot of equipment was carried over from the H-90, like the periscopes.

The X1A2 turret had a fixed mount for a .50 cal machine gun on the left side of the turret, in front of the commander’s cupola (the second batch had a swing arm mount). The commander’s cupola’s structure was slightly raised from the turret top to provide the commander with a 360 degree view. The antennas of the radio sets were located behind the gunner’s cupola on both sides of the turret. Spare tracks were mounted on the turret bustle sides, which might hint that the turret bustle sides were 12.5 mm (0.5 inch) thick, as it required additional tracks as armor. This placement of the spare tracks meant that the smoke dischargers were moved to the front of the turret, in a set of 3 dischargers on each side. A small light was also installed on the turret side of the commander’s cupola. On the very rear of the turret was a storage box welded on the turret rear, right behind the spare track protected plates.

The turret could traverse 360 degrees in 12 seconds with a hydraulic drive. The base rangefinding is done through graticule rangefinding, but laser and coincidence rangefinders were offered as well.

Side of the X1A2’s turret.
Source: http://www.primeportal.net/tanks/gino_marcomini/x1a2_carcara/

Armament

The production X1A2s were armed with the license produced EC-90 90 mm low-pressure guns manufactured by Engesa. These guns were derived from the Cockerill Mk.3 guns. The low-pressure gun allowed vehicles like the X1A2, but also the 5 tonnes AML-90, to mount a gun with significant armor penetration capabilities.

The EC-90 gun schematics.
Source: Manual de Opercão 9110-733-604 – Torre ET-90 II e Armamento

The trade-off was that these guns would, for a long time, only be able to fire High Explosive Anti Tank (HEAT) ammunition because Armor Piercing (AP) rounds simply had too little muzzle velocity to compete with HEAT. Armor Piercing Fin Stabilized Discarding Sabot (APFSDS) rounds did later appear, but these did not provide any improvement in penetration compared to HEAT rounds. A 90 mm APFSDS round for the later Cockerill guns would penetrate 100 mm (3.9 inch) of armor at 60 degrees from vertical at a range of 1,000 meters (1,090 yards), compared to 130 mm (5.1 inch) at 60 degrees for HEAT at any range. This meant that the APFSDS round mainly served as a round against targets with HEAT countermeasures.

Engesa did develop an APFSDS round for their EC-90 gun on the EE-9 Cascavel on request from Iraq around 1985, but this round would never finish development and only a few test batches were ever produced. The main issue was that the APFSDS round needed to reach higher velocities than the low-pressure rifled guns were designed for. The fixation which kept the sabot together would get damaged when the round was fired. Another issue was the muzzle brake, as the then-current muzzle brakes of the EC-90 guns prevented the use of APFSDS rounds. A pepper pot style muzzle brake was used to solve this issue, but the downside was that the pepper pot muzzle brake was less effective in mitigating recoil. Why the development of the APFSDS round was eventually cancelled is unknown. An Engesa engineer who worked on the APFSDS round believed that they would have been able to fix the problems considering the round started development 8 years before Engesa’s bankruptcy. The employee also stated that the project just did not take off and interest in the round from Iraq was probably not large enough to complete its development.

An Engesa employee with an APFSDS round of the EC-90 at Engesa’s test range.
Source: Private collection

Contrary to common statements, the X1A2 was thus not able to fire APFSDS rounds in the configuration it used at the time. Not only were they not available at the time when the X1A2 was in service, the development of the APFSDS round was never completed by Engesa. It also did not have a muzzle brake that would support the APFSDS round. Since neither requirements were met, the X1A2 never used APFSDS in its loadout. In addition, by the time the APFSDS round could have been ready, interest had already completely shifted to the M41C and the main battle tank projects like the Osorio and Tamoyo.

The X1A2 had access to HEAT, High Explosive Squash Head (HESH), and High Explosive (HE) rounds. The HEAT round was meant for anti-armor purposes and was the X1’s anti-tank round. The HESH round was mainly meant for bunkers, walls and light vehicles, and not as ‘anti-armor’ ammunition. The HE round was used as a general purpose support round. The X1A2 also had access to a white phosphorus smoke round and a HEAT practice round.

Round

Capability

Effective range

Velocity

HEAT (High Explosive Anti Tank)

250 mm (13.8 inch) flat at any range.

2,000 meters (2,185 yards)

890 m/s

HESH (High Explosive Squash Head)

Meant for bunkers, walls and light vehicles.

2,000 meters (2,185 yards)

800 m/s

HE (High Explosive)

Lethal radius of 15 meters (16 yards)

2,000 meters (2,185 yards)

700 m/s

HEAT-TP (High Explosive Anti Tank – Training Projectile)

Training projectile

2,000 meters (2,185 yards)

890 m/s

White Phosphorus – Smoke

Smoke round

2,000 meters (2,185 yards)

695 m/s

The X1A2 stowed 24 rounds in the turret and an additional 44 rounds in the hull, for a total of 68 rounds of 90 mm ammunition. In addition to the 90 mm, the X1A2 mounted a turret top .50 caliber machine gun (750 rounds) for the commander, and a coaxial .30 machine gun (2,500 rounds). It has a gun depression of 8 degrees and elevation of 17 degrees. The X1A2 had 16 smoke grenades for its 6 smoke dischargers.

Service

The X1A2 was delivered to the 6th RCB in January 1981, with 10 X1A2s replacing the M4 Shermans of the 2nd Tank Squadron. The X1A2s operated together with the X1s of the 1st tank squadron, to which the X1’s were delivered in 1978.

X1A2’s of the 6th RCB.
Source: Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivatives

The fact that the X1A2 replaced the M4 Sherman and had a larger turret than the X1 led to a very interesting situation. Being used to the 3-man turret of the M4 Sherman, the fresh X1A2 crews tried to adopt the same practice in the X1A2 turret. The turret was very cramped and the practice was abandoned. According to veterans, the commander would have to exit the turret and re-enter the turret to use the radio in the turret bustle. In a real battle situation this would have been impractical and dangerous.

X1A2 crosses a bridge laid by the XLP-10 bridgelayer.
Source: Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivatives

The X1A2 would encounter various issues during its service life, with the 18-ton M4 tractor torque converter being the biggest issue. The torque converter used by the tank was not designed for a vehicle of the size and speed of the X1A2. What made matters worse was that it was lubricated by poor quality oil used in Brazil. The high concentration of sulphur and low flash point caused the component to wear out much quicker.

To fix this issue, Bernardini suggested replacing the 18-ton M4 torque converter with a TwinDisc converter from the US. Bernardini would acquire one torque converter from TwinDisc and it would be successfully tested. Bernardini ordered enough torque converters to refit the X1A2 fleet, but due to the M41C program, they were never installed.

The controlled differential also caused issues for the X1A2. The more wear the differential had, the harder the X1A2 became to steer. An additional downside compared to the M41 Walker Bulldog was that the entire turrets of the X1 family had to be lifted from the hulls to perform maintenance to the drive shaft of the tanks. Another issue that caused premature wear and difficulty in operation was the lack of instruction manuals for the X1 family as a whole.

X1A2 of the 6th RCB and three X1’s.
Source: Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivatives

Export Attempt

In the early 1980s, the Brazilian government and Bernardini attempted to export the X1A2 to Paraguay, which at the time only operated 21 M3 Stuarts and 3 Sherman Fireflies (the Stuarts being gifted to them by Brazil (12) and the United States (9), and the Shermans by Argentina, eventually replaced by 3 Sherman Repotenciados). As a sign of good will and in an attempt to make the Paraguayans more favourable towards the X1A2, the Brazilian government offered the revitalization of 15 M3 Stuarts. The M3 Stuarts would be upgraded to the X1P standard by receiving a general maintenance overhaul and the Scania-Vabis engine. These Stuarts are still in active service in the Paraguayan Army. Eventually, the X1A2 was never bought, potentially because the Paraguayans wanted to acquire the EE-9 Cascavel instead, of which 28 were delivered in 1985 together with 12 EE-11 Urutus. The X1A2 had a unit price of around 400,000 US Dollars in 1980 (about 1.3 million US dollars in 2021), against 243,600 US Dollars for the EE-9 in 1988 (about 560,000 US Dollars in 2021).

The X1A2 in Paraguay.
Source: Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivatives

Fate

The issues the X1A2 had, in addition to the upcoming M41C upgrades, would cause the Army to refrain from deploying the second batch of X1A2s. They were stored in São Paulo, where the vehicles continued to deteriorate until they were eventually discharged from service in 1989. A couple of these vehicles were turned into gate guardians and monuments, but others were scrapped.

The X1A2s would be gradually replaced from 1988 onwards by the M41C. The X1s, and probably X1A2s as well, were decommissioned in July 1994.

The M41C.
Source: http://www.lexicarbrasil.com.br

Conclusion

The X1A2 was an interesting step for the Brazilian defence industry. It was the first and so far only serially produced, albeit only in limited capacity, tank fully designed in Brazil to see service in the Brazilian Army. It had its issues, but most of these seem to be fixable or were almost fixed by Bernardini. The only real issue the X1A2 would have is the differential, but since it had an improved length to width ratio compared to the X1A1, the steering was already much better. The X1A2 was a promising vehicle if these issues were fixed, and more importantly, if it was not overshadowed by the M41C program.

If the X1A2 was developed a bit earlier, it would have most likely seen more service, and its early flaws would have been fixed. Considering the start of the X1 family only began in 1973 and the X1A2 was only developed from 1976 onwards, while the M41 upgrade programs started their development in 1978, it seems that the first successful attempt of developing a national tank was inevitably too late. The X1A2 is the logical end to the development of Stuart based light tanks with 90 mm guns, which started in 1973. The Brazilians tried to design their own tank and succeeded. From the experience of the X1 program, Bernardini started the development of the M41 upgrade programs and the development of Brazil’s first Main Battle Tank: the MB-3 Tamoyo.

Illustrations

The X1A2 Prototype. Done by Brian Gaydos.
The X1A2 production vehicle. Done by Brian Gaydos.
The X1A2 production vehicle with camouflage. Done by Brian Gaydos.

Specifications CCL X1

Dimensions (L-W-H) 6.06 meters (19.8 feet) long including the gun x 2.4 meters (8.5 feet) x 2.45 meters (8 feet) tall
Total weight 19 tonnes (21 US tons)
Crew 3 (Driver, Commander-Loader, Gunner)
Propulsion Scania-Vabis DS-11 6-cylinder in-line 280 hp diesel engine
Suspension Bogie suspension
Speed (road) 60 kmh (37 mph)
Operational range 600 kilometers (373 miles)
Armament 90 mm D-921 low-pressure gun
.50 machine gun
.30 coaxial machine gun
Armor

Hull

Front (Upper Glacis) 50 mm (2 inch) at 60 degrees
Front (Lower Glacis) 50 mm (2 inch) at 45 degrees
Sides (guess) 25 mm (1 inch)
Rear (guess) 25 mm (1 inch)
Top (guess) 13 mm (0.5 inch)
Floor (guess) 13 to 10 mm (0.5 to 0.4 inch)

Turret

25 mm (1 inch) frontal part
12.5 mm (0.5 inch) rear part

Production 24
Special thanks to Expedito Carlos Stephani Bastos, the leading expert in Brazilian vehicles, please visit his website for further reading on Brazilian vehicles: https://ecsbdefesa.com.br/, Jose Antonio Valls, an Ex-Engesa employee and expert in Engesa vehicles, Paulo Bastos, another leading expert of Brazilian Armored vehicles and the author of the book on Brazilian Stuarts and the website https://tecnodefesa.com.br, Adriano Santiago Garcia, a Captain in the Brazilian Army and ex-company commander on the Leopard 1 and ex-lecturer on the Brazilian Armored School, and Guilherme Travassus Silva, a Brazilian with whom I was able to endlessly discuss Brazilian Vehicles and who was always willing to listen to my near endless ability to talk about them.
Sources

Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivatives – Hélio Higuchi, Paulo Roberto Bastos Jr., Reginaldo Bacchi
Blindados no Brasil – Expedito Carlos Stephani Bastos
Jane’s Light Tanks and Armoured Cars of 1984
Worldwide Tank Fire-Control Systems – CIA
http://www.lexicarbrasil.com.br/
Personal correspondence with Expedito Carlos Stephani Bastos
Personal correspondence with Paulo Roberto Bastos Jr.
Caiafa Master
Engesa brochures and manuals
Cockerill brochures
TM 9-785 18-Ton High Speed Tractors M4, M4A1, M4C, and M4A1C – US Army April 1952.
Stuart: A history of the American Light Tank, Volume 1 – R.P. Hunnicutt
Tecnologia Militar Brasileira magazine