This Medium Mark A Whippet was intended for fast mobile assaults. Although the track design appears more "modern" than the British Tanks Mark I to V, it was directly derived from Little Willie, the first tank prototype and was unsprung. The crew compartment was a fixed square turret at the rear of the vehicle, and two engines of the type used in contemporary double-decker buses were in a forward compartment, driving one track each.
| Medium Mk A Whippet | |
|---|---|
| Type | Medium tank |
| Place of origin |  United Kingdom |
| Service history | |
| In service | 1918-1930s |
| Production history | |
| Designer | William Tritton |
| Manufacturer | Fosters of Lincoln |
| Produced | 1917-1918 |
| Number built | 200 by 14 March 1919 |
| Specifications | |
| Weight | 14 t |
| Length | 6.10 m (20 ft) |
| Width | 2.62 m (8 ft 7 in) |
| Height | 2.75 m (9 ft) |
| Crew | 3 |
| | |
| Armour | 14 mm |
| Main armament | 4 × 0.303 inch Hotchkiss machine guns |
| Secondary armament | none |
| Engine | 2× Tylor Twin 4 cylinder side-valve JB4 petrol engine 2x 45 hp (67 kW) |
| Power/weight | 6.4 hp/tonne |
| Transmission | 4 forward speeds and 1 reverse |
| Suspension | unsprung |
| Speed | 13.4 km/h (8.3 mph) |
Steering
When driving in a straight line the two engines were locked; turning the steering wheel gradually closed the throttle for the engine of one track and opened the throttle for the engine driving the other. The two engines were joined at their cross-shafts, from which the final drive to the tracks was by chains to sprockets on either side. When steering the clutches joining the cross-shafts were released, one engine sped up while the other slowed down, the turn being on the side opposite to that of the faster running engine. The steering effect could be increased by use of the brakes on one engine or another. This arrangement had the advantage over that of earlier tanks of being controlled by one man only, but called for great skill on the part of the driver, because one or both of the engines could be stalled if care was not exercised. Although in theory a simple solution to give gradual steering, in practice it proved impossible to control the speeds of the engines, causing the vehicle to take an unpredictable path. Drivers grew wary and stopped the vehicle and locked one track before every turn; this caused many track breaks, as the movement became too abrupt.
Other features
The fuel tank was in the front of the hull. The sides featured large mud chutes which allowed mud falling from the upper treads to slide away from the tank, instead of clogging the suspension.
Armament
Armament was four 0.303 in Hotchkiss Mk 1 machine guns, one covering each direction. As there were only three crewmen, the gunner had to jump around a lot, though often assisted by the commander. Sometimes a second gunner was carried in the limited space, and often a machine gun was removed to give more room, as the machine guns could be moved from one mounting position to another to cover all sides.
