Medium Tank Mk A

Designed for speed and mobility (at a breakneck 8.3 mph!), the Medium Tank Mk A appeared on the Western Front in late 1917. The tank was powered by two gasoline engines, one for each track, that were originally used in London buses. Steering of the tank was accomplished by changing the rate of each engine independently as needed to change the rate of the tracks. At speed, this proved difficult to accomplish with any degree of control, and at rest the torque on the tracks frequently caused the tracks to break. Nevertheless, the tank was used to good effect offensively to plug gaps in the line and to dash into rear areas to wreak havoc with German defenses.

The turret is mounted to the rear of the chassis (with the engine in front). It does not rotate, and so there is a LMG mounted in all four sides of the superstructure. Initially the tank was crewed with three: commander, driver, and gunner. The difficultly in manning all four guns often led to the tank being crewed with an additional gunner.

The Mark A tank burns 3 gallons of gasoline per hour at routine usage. It had a historical range of 160 miles. A full load of fuel and ammo costs $67.

Subassemblies: Small Tank chassis +3; Large Weapon turret [Body:T] +2, two tracks +2.

Powertrain: Two 33.6-kW standard gasoline engines with 67.2-kW tracked drive train and 60-gallon standard fuel tank.

Occ.: 3-4 CS Body

Cargo: 8 Body

Armor F RL B T U

Hull: 4/40 4/40 4/40 4/40 4/40

Cupola: 4/40 4/40 4/40 4/40 4/40

Tracks: 4/35 4/35 4/35 4/35 4/35

Weaponry:

4xGround LMG/.303 Hotchkiss [Turret:R,L,F,B] (5,400 rounds).

Statistics:

Size: 20'x8.5'x9' Payload: 0.72 tons Lwt.: 14 tons

Volume: 48 Maint.: 82 hours Cost: $5,975

HT: 12. HPs: 2,000 Body, 120 Turret, 400 each Track

gSpeed: 8 gAccel: 2 gDecel: 20 gMR: 0.25 gSR: 5

Ground Pressure Low. 2/3 Off-Road Speed.

Design Notes:

A Light Tank Chassis was chosen for the design and then doubled for weight, cost and HPs. This design path was chosen since chassis more closely matched the space required, arrived at a better weight match with the historical value once doubled, and weakened the tracks to mimic the historical problems with track damage. Overall design weight was increased 8% to the historical. Fuel capacity is based on a rough calculation between maximum range, top road speed, and design fuel consumption. Other sources listed much lower ranges (40-80 miles) and are probably more accurate; nevertheless, best-case range and speed are listed above. Design gSpeed was 21 mph; it was lowered 60% to the historical. Armor is riveted; historical thickness is 0.2" to ½" (DR 40 was used overall to increase design weight).

Variants:

None. The nickname "Whippet" was sometimes applied generically to any light tank.

From the Aerodrome for GURPS