This armoured fighting vehicle 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, polygonal 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.
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.[11] 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.[12] 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.[citation needed] Nevertheless, the vehicle could easily negotiate shell craters. Crews that believed that treads had to be as long as the hull, as with the heavy tanks, were surprised to see the Whippet, with shorter tracks, successfully exit holes.[13]
