Reaper powered by a traction engine. Traction engines are mobile steam-powered road vehicles which can be used for haulage, agricultural purposes, or as a mobile power source. The earliest portable steam engines were not self-propelled but had to be pulled by teams of horses. Thomas Aveling, a Kentish farmer, is widely recognised as the father of the mobile traction engine as, dissatisfied with using horse power to move engines from place to place, he devised and built self-propelled steam engines at Rochester, Kent. He became a major manufacturer of the machines, specialising in steam road rollers, which were exported all over the world. Aveling and Porter continued to build traction engines until World War II.
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