Pedrail wheel

The pedrail wheel is a type of wheel developed in the early 20th century for all-terrain locomotion. It was used in agricultural machinery and was considered as a possible technique for the development of the tank in World War I, but was ultimately replaced by the more robust continuous track mechanism. Pedrail wheels should not be confused with Dreadnaught Wheels which have articulated rails attached at the rim for the wheel to roll over (also known as endless railway wheels).

Definition
According to the 1913 Webster's Revised Unabridged Dictionary, a pedrail is: "A device intended to replace the wheel of a self-propelled vehicle for use on rough roads and to approximate to the smoothness in running of a wheel on a metal track. The tread consists of a number of rubber shod feet which are connected by ball-and-socket joints to the ends of sliding spokes. Each spoke has attached to it a small roller which in its turn runs under a short pivoted rail controlled by a powerful set of springs. This arrangement permits the feet to accommodate themselves to obstacles even such as steps or stairs."

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Invention
The pedrail wheel was invented in 1903 by the Londoner Bramah Joseph Diplock. It consists in the adjunction of feet (Latin radical "ped") 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
H. G. Wells, in his short story The Land Ironclads, published in The Strand Magazine in December 1903, described the use of large, armoured cross-country vehicles, armed with cannon and machine guns, and equipped with pedrail wheels, to break through a system of fortified trenches, disrupting the defence and clearing the way for an infantry advance:

""They were essentially long, narrow and very strong steel frameworks carrying the engines, and borne upon eight pairs of big pedrail wheels, each about ten feet in diameter, each a driving wheel and set upon long axles free to swivel round a common axis. This arrangement gave them the maximum of adaptability to the contours of the ground. They crawled level along the ground with one foot high upon a hillock and another deep in a depression, and they could hold themselves erect and steady sideways upon even a steep hillside.""

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In War and the Future, HG Wells acknowledged Mr. Diplock's pedrail as the origin for his idea of an all-terrain armoured vehicle: ""The idea was suggested to me by the contrivances of a certain Mr. Diplock, whose "ped-rail" notion, the notion of a wheel that was something more than a wheel, a wheel that would take locomotives up hill-sides and across ploughed fields, was public property nearly twenty years ago""

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World War I
During World War I, as trench warfare immobilized the front, a number of proposals were made for machines that could make their way across no-man's-land to enemy lines, and experiments were conducted with the Pedrail system.

The Royal Navy and the Landships Committee (established in February 1915), largely at Winston Churchill's urging, agreed to sponsor experiments and tests of armoured tractors as a type of "land ship". The initial Pedrail design coming from Murray Sueter's discussions with Diplock was for a 25 ton vehicle on two pedrail tracks carrying a 12-pounder gun in a turret. In March 1915, RE Compton redesigned it as a 40-foot long vehicle that could carry a storming party of 50 troops protected by 8 mm of armour plate. Churchill ordered the building of 18 experimental landships: 12 using Diplock pedrails, and 6 using large wheels. Construction failed to move forward, as the wheels seemed impractical, and the pedrails met with industrial problems. When these attempts had failed by July 1915, continuous tracks were tested, and they soon became the technique of choice for the development of the tank. The pedrail was considered as too weak for an all-terrain armoured machine, and "caterpillar" continuous tracks were ultimately preferred.

The Pedrail machine contract was initially with Foden but passed to Birmingham Carriage and Wagon (BCW) in April 1915. In order that it would be able to move through French towns and villages, the design was altered to articulate in the middle. It was also reduced in height and side armour increased to 12 mm to give better protection from rifle fire. BCW asked to be released from the contract so they could concentrate on other work, and so the contract — now reduced to one machine — passed on to Fosters of Lincoln. Work stopped on the Pedrail as it was too heavy and better designs were in the offing but the parts already constructed were used by Stothert & Pitt to assemble a flamethrower carrying vehicle for the Trench Warfare Department in 1916. Weighting 32 tons "unladen", it achieved 15 mph from two 100 hp engines.