Boydell’s steam tractor, with its ‘footed’ wheel, was a practical attempt to enable vehicles to cross soft, uneven ground and the inferior roads of the 19th century.
Steam traction engines were also used to tow guns on other occasions during the second half of the 19th century. In the meantime, prompted probably by the Crimean War, J. Cowan proposed another use of steam traction for military purposes in 1855 in Britain by taking out patent No. 747 for a `Locomotive Battery for Field of Battle with a Steam Engine’ – a wheeled vehicle with a turtle-like iron carapace out of which protruded several guns and at the side of which were scythes for mowing down any troops that might attack it.
All he proposed was the adaptation of the existing steam tractor of James Boydell (first patented in 1846) to mount cannon behind a dome-like, iron outer casing and travel where other types of wheeled vehicles could not move. The Boydell tractor was a practical example, used in the Crimea, of a portable railway – in this case a vehicle which did not sink into the ground because its wheels were fitted with detached pivoted rails, or feet. These were laid down and then picked up as the wheel turned, to spread the vehicle’s load. Had it been built, the Cowen’s crews would almost have baked alive behind their armour, yet they might have survived against the enemy in this genuine proposal for a practical, self-propelled vehicle uniquely incorporating mobility, firepower and protection. Certainly the Boydell footed wheel triggered many inventors to begin experiments with `continuous tracks’.
Cowan’s vehicle was never built, but during the South African War of 1899-1902 the British Army used about 50 traction engines for towing supply trucks and guns. In 1900 two of the engines built for use in South Africa by John Fowler and Co. of Leeds were armoured, as were the trucks they towed, to protect them against Boer attacks when they were used for carrying supplies. Eventually the number of the armoured Fowler engines sent to South Africa rose to four. The armour of the Fowler engines and of the trucks was provided with loopholes through which rifles could be fired, and a field gun could be hauled onto a truck instead of being towed. In principle, there was only a small step from this to a steam-powered, gun-armed armoured fighting vehicle. Such a vehicle had in fact already been envisaged by Cowan and was depicted in 1883 by A. Robida in a French journal La Caricature.
The ideas of Robida, like those of Cowan, were never implemented, but 20 years later steam-powered armoured vehicles were the subject of a story by H. G. Wells, the science fiction writer, which was published in the Strand Magazine in December 1903 under the title `The Land Ironclads’. This story is often presented as a prophetic vision of future armoured vehicles and as having influenced, albeit indirectly, the development of the first British tanks several years later. In fact, Wells’ `ironclads’ did not represent an advance on Fowler’s armoured steam engines built three years earlier so far as their means of propulsion were concerned, and this was equally true of their armament, which still consisted of rifles. Nor did they foreshadow future armoured fighting vehicles in other respects, except for being envisaged to operate off the roads over broken ground. However, what was to make this possible was not very practicable, as it was based on the use by the `ironclads’ of Pedrails – another type of footed wheel devised around 1899 by B. J. Diplock. This wheel has been confused with the Pedrail track, which was not brought out by Diplock until 1910, and has led to the erroneous belief that Wells foresaw tracked armoured vehicles