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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