BT-7 Fast Tank
The BT (Bystrokhodniy Tank, “Fast Tank”) series of tanks began in 1931, with the purchase from the U.S. of two Walter Christie tanks, using his unique suspension system. This eventually lead to the BT-7, which entered production in 1936. To it’s crews it was also known as the Betka (“Beetle”) and Tri-Tankista (“Three Tanker”).
While the BT-7 was reasonably fast due to the use of an aircraft engine, it was also thinly armored (comparable to the Panzer II in thickness). When the BT-5 and BT-7 faced German panzers in the summer of 1941 it did not fare well, despite better armament and speed, because of poor deployment by the Soviets and an engine that tended to overheat.
One unusual feature of the BT series was that they were ‘convertible’ tanks; the treads could be removed and stowed on the sides of the tanks, allowing it to run on it’s rubber-rimmed roadwheels. The first pair of roadwheels were steerable (in fact, the BT series used car-type steering wheels rather than the two levers more common in tanks at the time). While this could be of use strategically, removing and replacing the treads were time-consuming (10-15 minutes to switch modes) and it is believed that the feature was seldom used in the field.
Some 2,000 BT-7’s were built. They are mainly important for paving the way for the later T-34, which also used the Christie suspension and a similarly shaped-body (though with better sloping and much thicker armor).
The BT-7 Model 1937 has a crew of three. The commander sits in the turret and fires the cannon and MG. Also in the turret is the loader. The driver sits in the body and fires the hull MG. The commander manually traverses the turret at 3 degrees per second. The BT-7 uses 16.5 gallons per hour at routine usage.
Subassemblies: Medium Tank chassis +3, full rotation Small
AFV turret [Body:T] +2, tracks +3.
Powertrain: 336-kW aerial HP gas engine w/ 336-kW tracked
drive train and 167 gallons fuel in standard fuel tank [body]; 16,000-kWs
batteries.
Occupancy: 1 CS Body, 2 CS Turret Cargo:
5.5 Body, 2.1 Turret.
| Armor | F | RL | B | T | U |
| Body | 5/150 | 4/50 | 4/45 | 4/35 | 4/35 |
| Tracks | 4/40 | 4/40 | 4/40 | 4/40 | 4/40 |
| Turret | 4/60 | 4/60 | 4/60 | 4/50 | 0/0 |
Weaponry
50mm Medium TG/45mm M-1934 [Tur:F] (188).
Ground LMG/7.62mm DT [Tur:F] (1500).
Ground LMG/7.62mm DT [Body:F] (900).
Statistics
| Size: 20’¥9’¥9’ | Payload: 1.6 tons | Lwt: 15.2 tons |
| Volume: 103 | Maint.: 52 hours | Price: $14,600 |
HT: 12
HP: 1500 [Body], 150 [Turret], 540 [Each Track]
| gSpeed: 33 | gAccel: 4 | gDecel: 20 | gMR: 0.25 | gSR: 6 | GP: Low (2/3) |
Design Notes
The design purchased 168 gallons of fuel tanks, 2,500 rounds of LMG
ammo and 195 rounds of tank gun ammo. The historical values have been used
instead. The design weight was reduced 7% to match historical weight and
gSpeed was reduced from the 47mph design speed. Turret armor is Expensive.
Some BT-7’s mounted a second DT MG (Ground LMG) facing to the rear.
The BT-7 could officially run at 45mph with the tracks removed.
Most BT-7’s lacked a radio. Those that were equipped with one had ammo capacity reduced to 132-146 45mm rounds.
While the aircraft engine provided a great deal of power, it tended to overheat in a ground vehicle. Any HT rolls involving the engines should be made at -3.
Variants
The BT-2 was armed with a 37mm M-1930 or M-1931 cannon (37mm Medium
Tank Gun) with 96 rounds and only a coaxial MG (2709 rounds). Turret armor
was DR 50 front, left, right and rear and DR 40 top. Speed was 37mph on
tracks and 66mph wheels. Weight was 11.2 tons. 396 were built.
The BT-5, of which 5,000 were built, was generally similar to the BT-7, but had less turret armor (use the BT-2 stats; some early BT-5’s, in fact, used BT-2 turrets) and only 72 or 115 45mm shells. It used a 261 kW engine and 105 gallon fuel tanks. Weight was 12.7 tons. Around 50 BT-5’s saw action in the Spanish Civil War and numbers were used against the Japanese in Manchuria.
The BT-7A replaced the 45mm cannon with a 76.2mm howitzer (76.2mm Very Short Howitzer). It carried 50 shells, 40 if radio-equipped. The BT-5A was similar, but based on the BT-5. Less than 200 were built.
Sources:
http://www.wwiivehicles.com/html/ussr/bt.html
http://www.onwar.com/tanks/ussr/data/bt7m37.htm
http://www.internetmodeler.com/2002/may/first-looks/EE_BT-7.htm
Armored Wargaming, Bruce Quarrie, 1988