The pedrail wheel is a type of wheel developed in the early 20th century for all-terrain locomotion. They consist of a series of "feet" connected to pivots on a wheel. As the wheel turns, the feet come into contact with the ground, and rotate so they remain flat to the ground as the wheel moves over them. Pedrail wheels may be simple systems with the feet connected to a rigid wheel, but more complex systems including various built-in suspension systems were designed to improve performance on uneven ground. The system was used in agricultural machinery. Pedrail wheels should not be confused with dreadnaught wheels which have articulated rails attached at the rim for the wheel to roll over. Both designs were replaced by continuous track systems.
The pedrail wheel was invented in 1903 by the Londoner Bramah Joseph Diplock. It consists in the adjunction of feet to the rail of a wheel, in order to improve traction and facilitate movement in uneven or muddy terrain. Sophisticated pedrail wheels were designed, with individual suspension for each foot, which would facilitate the contact with uneven terrain. Bramah Joseph Diplock also invented the pedrail locomotive which was featured in the 7 February 1904 New York Times.
Fiction
, in his short storyThe Land Ironclads, published in The Strand Magazine in December 1903, described the use of large, armoured cross-country vehicles, armed with automatic rifles and moving on pedrail wheels, to break through a system of fortified trenches, disrupting the defence and clearing the way for an infantry advance: In War and the Future, Wells acknowledged Diplock's pedrail as the origin for his idea of an all-terrain armoured vehicle: Although Wells describes the pedrail wheels in detail, a number of authors have mistakenly taken his description to be of some form of caterpillar track. Diplock's version of an endless track was not designed until some ten years after the publication of Wells' story. The pedrail wheel played no part in the design of the first British tanks.
Chaintrack
In 1910 Diplock abandoned the Pedrail Wheel and began developing what he called the Chaintrack, in which fixed wheels ran on a moving belt, very like the caterpillar track as it is now understood. It was a complicated and high-maintenance system, and in 1914 Diplock eventually produced a version on a simpler, single wide track. With a body fitted, the machine could carry a ton of cargo and be pulled with minimal effort by a horse. It demonstrated the attributes of the caterpillar track: low friction and low ground pressure.
