Tanks in the Great War, 1914-1918

by J. F. C. Fuller

CHAPTER III
MECHANICAL CHARACTERISTICS OF TANKS

The following very brief account of the mechanical characteristics of tanks, it is hoped, will prove sufficiently simple and complete to give to the non-mechanical reader some idea of the tank as a machine.

The Mark I Tank (see [Frontispiece])

The first British tank made, and to be used, was the heavy machine, already described in the previous chapter, the Mark I tank, the general outline of which remained the standard design for the hulls of all British heavy machines up to the end of the war. As will be shown later, many mechanical improvements, making for higher efficiency and greater simplicity of control, were introduced from time to time, but the fact remains that the profile of the Mark V tank of 1918 was to all intents and purposes that of the Mark I of 1916, and surely this is a striking tribute to the genius of the designers who, without much previous data upon which to base their work, produced the parent weapon.

It is not proposed here to enter upon the general arrangement of the Mark I tank, but reference to two important points in design is of interest. The first is that this machine was fitted with a “tail,” consisting of a pair of heavy large-diameter wheels, mounted at the rear of the machine upon a carriage, which was pivoted to the hull in such a manner that the wheels were free to follow the varying contours of the ground. A number of strong springs normally kept the wheels bearing heavily upon the ground, whilst a hydraulic ram, operated by an oil pump driven from the engine, was intended to enable the carriage to be rocked upon its axis, in order to raise the wheels well clear of the ground on occasions when it was necessary to “swing” the tank.

The object of this “tail” device was to provide means of steering the machine and, to this end, the driver was provided with a steering wheel which, operating a wire cable over a bobbin or drum, altered the path of the “tail” wheels, and allowed the tank to be steered, under favourable conditions, through a circle having a diameter of about sixty yards. The disadvantages of this fitting far outweighed any virtues it may have possessed. Countless troubles were experienced with the ram and its pump; the wire steering cable was constantly stretching or slipping through the bobbin, thus affecting the “lock” of the tail wheels; the driver was subjected to great physical strain in overcoming the tremendous resistance offered by the road wheels; the whole device was very prone to be damaged by shell-fire in action. Against these indictments should be recorded the fact that the possession of a “tail” enabled the Mark I tank successfully to span and cross a wider trench than the later “tailless” machines of the same dimensions could negotiate, owing to the fact that as the wheels supported the rear of the tank over the point of balance, the risk of “tail dive” was considerably reduced. However, at the close of the operations of 1916, all tanks were shorn of their tails, and no subsequent models were fitted with them.

The second point of interest regarding this early machine relates to its sponsons. These, on both the male and female machines (armed with full length 6-pounder and Vickers machine-guns respectively) were planted upon and bolted to the walls of the hull and, for entraining purposes, these had to be removed and carried upon special trolleys which could be towed behind the tanks. It will readily be seen that this arrangement involved a considerable amount of labour, and rendered the process of entraining an extremely lengthy one; this led to an improved form of sponson being produced for the Mark IV machine.

The chief outstanding weaknesses of the Mark I machine, disclosed during the first appearance in action, were:

That the engine was provided with no silencer, consequently the noise, sparks, and even flames, which proceeded from the open exhaust pipes, passing through the roof of the tank, constituted a grave danger during the latter stages of an approach march. Many ingenious tank crews fitted to their machines crude types of silencers made out of oil drums, or adopted the plan of damping out the sparks by using wet sacks in relays, or covering the exhaust pipe with clay and mud.