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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

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