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Bernardini MB-3 Tamoyo 2
introduction:
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The Tamoyo 2 emerged as part of Project Tamoyo 1, initiated by Brazil in 1979 to develop a new family of tanks. While the Tamoyo 1 shared parts with the M41 Walker Bulldog, the Tamoyo 2 was designed with a modern transmission, the HMPT-500. However, the Tamoyo 2 ended up serving more as a test than a full implementation and was discarded by the end of the Tamoyo program in 1991.For more information, I recommend reading the full article written by Darren Hazes on the website MB-3 Tamoyo 2 - Tank Encyclopedia.
Here are the highlighted details:
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The hull of Tamoyo 2 during tests in Bernardini.
- The Tamoyo 2 project began with Bernardini considering the possibility of a Tamoyo with an HMPT-500 transmission before March 27, 1984.
- Bernardini likely contacted and initiated negotiations with General Electric for the transmission.
- A contract was signed on March 27, 1984, for the construction of 8 Tamoyo prototypes, including 4 Tamoyo 1s, a single Tamoyo 2, and three engineering vehicles.
- General Electric provided a single HMPT-500-3 transmission to Bernardini for testing, along with technical support.
- The Tamoyo 2 hull was completed around 1986 and served as a testbed for an HMPT-powered Tamoyo.
- Initially, it briefly received the same 90mm-armed turret as the Tamoyo 1 but was later equipped with the Tamoyo 3’s 105mm L7-armed turret before May 10, 1987, at an exhibition.
- The Tamoyo 2 effectively served as a testbed for the transmission and the new 105mm-armed L7 turret intended for export on the Tamoyo 3, marking the pinnacle of the Tamoyo 2 program.
The MB-3 Tamoyo-II-105:
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- The Tamoyo with the Tamoyo 3 turret was designated as MB-3 Tamoyo-II-105 when presented at a military exhibition, alongside the Armored Personnel Carrier Charrua.
- The accompanying plaque listed its specifications, including a 500 hp DSI-14 engine, HMPT 500 transmission, a top speed of 67 km/h, the ability to climb a 60-degree slope and a 30-degree side slope, a 500 km operational range, a 105 mm L7 gun, coaxial machine gun, advanced fire control system by Moog AEG and Ferranti Computers, capability to fire a wide range of ammunition, and a combat-loaded weight of 31 tonnes.
- The Tamoyo 2 armed with the 105 mm gun had a short lifespan, as the Tamoyo 3 with the 105 mm armored turret was already finished and presented on May 10, 1987, during a cavalry event in Rio Grande do Sul state.
- Only one 105 mm-armed turret was known to be built by Bernardini.
- The Tamoyo 2-105 served as a cost-effective version of the Tamoyo 3, which was offered with an HMPT-500 and CD-850 transmission, paired with a General Motors 8V-92TA 736 hp diesel engine.
- The Tamoyo 2 never received the spaced armor package planned for the Tamoyo 3’s hull.
- Its development appeared to be canceled after the 105 mm turret was removed and mounted on the Tamoyo 3.
About changing transmission:
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HMPT-500-3 offered several advantages over the CD-500-3 transmission, standing out in terms of power, weight, and space. Here are the key points:
- Power: The HMPT-500-3 transmission could generate up to 600 hp, while the CD-500 was limited to 500 hp. This resulted in a significant increase in the hp/ton ratio in the Tamoyo 1 and 2 tanks, going from 16.67 to 20 hp when combat-loaded.
- Weight and space: The HMPT-500 occupied less space, with 0.62 m³ compared to the CD-500’s 0.85 m³. This led to a weight reduction, with the HMPT weighing 862 kg dry (without hydraulic fluid), while the CD-500 weighed 925 kg dry.
- Efficiency: The HMPT transmission was more efficient, continuously adjusting the relationship between engine power, torque, and vehicle load to optimize fuel economy. Additionally, it offered an infinitely variable transmission ratio in three gears, providing the best torque-to-power ratio at low RPMs possible. This ensured that the HMPT transmission always operated with maximum efficiency in terms of torque, while the CD-500 operated only at maximum torque at a specific point in the gear. Furthermore, the HMPT had the ability to use the engine as a brake by reversing the hydraulic system for this purpose.
in detail:
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| Parameter | Tamoyo 2 with 90 mm turret | Tamoyo 2 with 105 mm turret |
|---|---|---|
| Weight (empty) | Approximately 28 tonnes | 29 tonnes |
| Weight (combat-loaded) | 30 tonnes | 31 tonnes |
| Hull Length | 6.5 meters (21.3 feet) | 8.9 meters (29.2 feet) |
| Length with gun pointing | 8.77 meters (28.8 feet) | 8.9 meters (29.2 feet) |
| Width | 3.22 meters (10.6 feet) | 3.22 meters (10.6 feet) |
| Height to turret top | 2.2 meters (7.2 feet) | 2.35 meters (7.7 feet) |
| Total Height | 2.5 meters (8.2 feet) | 2.5 meters (8.2 feet) |
| Crew | 4 (Commander, gunner, loader, driver) |
Hull:
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- Front Upper: 40 mm (1.6 inches) thickness, angled at 60 degrees, equivalent to 80 mm (3.15 inches) relative thickness.
- Front Lower: 40 mm (1.6 inches) thickness, angled at 45 degrees, equivalent to 57 mm (2.25 inches) relative thickness.
- Sides: 19 mm (0.75 inches) thickness, not angled, equivalent to 19 mm (0.75 inches) relative thickness.
- Top: 12.7 mm (0.5 inches) thickness, vertically oriented, equivalent to 12.7 mm (0.5 inches) relative thickness.
The Tamoyo’s hull also featured headlights and blackout markers 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 upper front side plates. Mounting points for spare track assemblies were located in the middle of the upper front plate, between the light sets. The driver was positioned on the left side of the upper front plate and had access to three vision blocks. The driver’s hatch was a sliding type, and there was also an escape hatch in the hull.
The hull sides provided mounting points for the installation of side skirts, consisting of four sets of skirts on each side. Early versions of the side skirts were made of steel, but later versions incorporated materials like rubber fibers and aramid to enhance effectiveness against certain projectiles. The Tamoyo 2 does not appear to have mounted its side skirts.
At the rear of the hull, the Tamoyo had two taillights on the lower rear plate and a towing hook on the lower rear plate. In addition to the towing hook, two brackets were installed on this plate and also on the lower front plate."
Mobility:
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- Motor: The Tamoyo 2 was powered by a liquid-cooled intercooled turbocharged V8 diesel engine, the DSI-14, producing 500 hp and 1,700 Nm (1250 ft-lbs) of torque at 2,100 rpm. This engine provided the Tamoyo with a power-to-weight ratio of 16.6 hp/ton (16.1 hp/ton for the Tamoyo 2-105).
- Transmission: It used a General Electric HMPT-500-3 hydro-mechanical transmission with 3 forward gears and 1 reverse gear.
- Speed: The combination of the engine and transmission allowed the Tamoyo to achieve a maximum speed of 67 km/h (40 mph) on level roads.
- Fuel Capacity: The tank had a fuel capacity of 700 liters (185 gallons), providing it with an approximate range of 550 km (340 miles). The Tamoyo 2-105 had a range of 500 km.
- Suspension: The Tamoyo utilized 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 road wheels and 1 on the last road wheel. The torsion bars were made of 300M alloy steel, similar to those used in the M1 Abrams program. The idler wheel was located at the front of the vehicle, while the drive sprockets were installed at the rear.
- Tracks: The Tamoyo used Brazilian-produced copies of the T19E3 tracks by Novatração. These tracks had a width of 530 mm (20.8 inches) and a ground contact length of 3.9 meters (12.8 feet). This provided the Tamoyo with a ground pressure of 0.72 kg/cm2 (10 lbs/in2) and a trench-crossing capability of 2.4 meters (7.9 feet). The tank had a ground clearance of 0.5 meters (1.6 feet), could climb a vertical obstacle of 0.71 meters (2.3 feet), climb a gradient of 31 degrees, and operate on a side slope of approximately 17 degrees. It had a fording depth of 1.3 meters (4.3 feet) and could also be operated in a neutral steer mode.
Turret
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- Turret Armor: The Tamoyo 2’s 90mm turret was armored with welded homogeneous steel plates angled at various angles to provide protection against frontal fire of 30mm and a total of 14.7mm.
- Turret Front Armor Thickness:
- Gun Shield: 50mm (2 inches) at 45 degrees, equivalent to 70mm (2.75 inches).
- Upper Front: 40mm (1.6 inches) with a variable armor angle (Upper: 60 degrees, Side: 67 degrees, Lower: 45 degrees), resulting in a relative thickness of 80mm (3.15 inches) on the upper front, 100mm (4 inches) on the front side, and 57mm (2.25 inches) on the lower front when firing from the front.
- Sides: 25mm (1 inch) at 20 degrees, equivalent to 27mm (1 inch).
- Rear (excluding storage box): 25mm (1 inch) at 0 degrees, equivalent to 25mm (1 inch).
- Top: 20mm (0.8 inches) at 90 degrees, equivalent to 20mm (0.8 inches).
- Shape and Features: The turret had a shape similar to that of an M41 turret but less ergonomic due to the use of flat plates instead of a complex-shaped side plate. The turret ring diameter was 2 meters (6.5 feet).
- Hatches: The turret had 2 hatches, one for the commander and gunner, and another for the loader. The commander’s hatch was located in the middle-right of the turret, while the loader’s hatch was located in the middle-left.
- Periscopes and Vision: The gunner had a passive day/night periscope located in a depression on the turret’s top, in addition to a coaxial direct vision telescope for the main gun. The commander had 7 periscopes available, which were passive day/night views. A laser rangefinder was mounted above the main gun.
- Smoke Dischargers: A set of 4 smoke dischargers was mounted on both sides at the front of the turret.
- Armament: The turret was armed with a 90mm BR gun and a heavy 12.7mm coaxial machine gun. The commander’s station could be armed with a 7.62mm machine gun for anti-aircraft purposes.
- Turret Drive: The turret had both electric and manual turret drive, and the gun had an elevation of 18 degrees and a depression of 6 degrees.
- 105mm Turret Armor: The armor values of the Tamoyo 2’s 105mm turret are unknown, but it can be speculated that they are somewhat similar or slightly thicker than those of the 90mm turret. The 105mm turret was an enlarged and flatter version of the original 90mm turret but with composite armor.
Armament
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- Main Gun: The Tamoyo 2 was armed with a Brazilian copy of the GIAT 90mm CS Super 90 F4 gun. The Brazilian designation for this gun was Can 90mm 76/90M32 BR3. This gun was an L/52 caliber gun that could withstand a pressure of 2,100 bar and had a recoil stroke of 550mm (21.6 inches). 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-aircraft round due to its 52-caliber length and the incorporation of a single-baffle muzzle brake, allowing the firing of APFSDS projectiles. The BR3 was expected to have five types of ammunition available: cartridge, high-explosive, high-explosive anti-tank, smoke, and fin-stabilized armor-piercing, discarding sabot (APFSDS) rounds.
- Main Gun Ammunition Types:
- APFSDS (Stabilized Armor-Piercing, Discarding Sabot): Effective Range - 1,650 meters (1,804 yards), Velocity - 1,275 m/s, Weight - 2.33 kg (5.1 lbs).
- HEAT (High-Explosive Anti-Tank): Effective Range - 1,100 meters (1,200 yards), Velocity - 950 m/s, Weight - 3.65 kg (8 lbs).
- HE (High Explosive): Effective Range - 925 meters (1,000 yards), Velocity - 750 m/s, Weight - 5.28 kg (11.6 lbs).
- Practice: Training round with a range of 200 meters (218 yards), Velocity - 750 m/s, Weight - 5.28 kg (11.6 lbs).
- White Phosphorus Smoke: Smoke round with an effective range of 925 meters (1,000 yards), Velocity - 750 m/s, Weight - 5.4 kg (11.9 lbs).
- Main Gun Ammunition Types:
- Ammunition Storage: The Tamoyo had stowage for 68 rounds of 90mm ammunition. Additionally, it was armed with a coaxial 12.7mm machine gun and could be armed with a 7.62mm machine gun at the commander’s station for anti-aircraft purposes, with 500 and 3,000 rounds of ammunition, respectively. The Tamoyo 1 also had 8 smoke dischargers, with four 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.
- Fire Control System: The fire control system included a computer with an unknown purpose, likely integrating better use of day/night sights and the laser rangefinder used by the Tamoyo 1. This could also mean lead calculation and integration of a weather system, although these were features of the Tamoyo 3, which used a much more advanced fire control system. The electrical fire control system, turret rotation, and gun elevation were produced by Themag Engenharia and the University of São Paulo.
- 105mm Turret: The Tamoyo 2-105 offered a 105mm gun and a much more advanced fire control system. It used an L7 LRF 105mm gun (Low Recoil Force). The low recoil force allowed the Tamoyo to mount a high-velocity gun, avoiding negative effects the recoil could have due to the lightweight of the Tamoyo. The 105mm Tamoyo also offered a much more advanced fire control system compared to the original 90mm 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 fire control computer. The FCS included a meteorological sensor, ammunition temperature sensor, ammunition drop calculator, and ammunition selector.
Specifications (MB-3 Tamoyo 2)
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Dimensions
- With 90 mm turret:
- Length: 6.5 meters (21.3 feet)
- Length with gun pointing forward: 8.77 meters (28.8 feet)
- Width: 3.22 meters (10.6 feet)
- Height to turret top: 2.2 meters (7.2 feet)
- Total height: 2.5 meters (8.2 feet)
- With 105 mm turret:
- Length: 6.5 meters (21.3 feet)
- Length with gun pointing forward: 8.9 meters (29.2 feet)
- Width: 3.22 meters (10.6 feet)
- Height to turret top: 2.35 meters (7.7 feet)
- Total height: 2.5 meters (8.2 feet)
Total Weight
- With 90 mm turret:
- Empty: 28 tonnes (30.9 US tons)
- Combat-loaded: 30 tonnes (33 US tons)
- With 105 mm turret:
- Empty: 29 tonnes (32 US tons)
- Combat-loaded: 31 tonnes (34 US tons)
Crew
- 4 members (commander, driver, gunner, loader)
Propulsion
- DSI-14 turbocharged V8 500 hp diesel engine
Suspension
- Torsion bar
Speed (Road)
- 67 km/h (40 mph)
Armament
- Main: 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: Data not available (?)
- 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: 25 mm at 20º (1 inch)
- Rear: 25 mm at 0º (1 inch)
- Top: 20 mm at 90º (0.8 inch)
Produced
- 1 unit
Source:
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MB-3 Tamoyo 2 - Tank Encyclopedia
Blindados no Brasil – Expedito Carlos Stephani Bastos
Bernardini MB-3 Tamoyo – Expedito Carlos Stephani Bastos
