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A steam wagon (steam lorry or steam waggon) is a steam-powered road vehicle for carrying freight. It was the earliest form of lorry (truck) and came in two basic forms: ''overtype'' and ''undertype'' – the distinction being the position of the engine relative to the boiler. Manufacturers tended to concentrate on one form or the other. Steam wagons were a widespread form of powered road traction for commercial haulage in the early part of the twentieth century, although they were a largely British phenomenon, with few manufacturers outside Great Britain. Competition from internal-combustion-powered vehicles and adverse legislation meant that few remained in commercial use beyond the Second World War. Although the majority of steam wagons have been scrapped, a significant number have been preserved in working order and may be seen in operation at steam fairs, particularly in the UK. ==Design features== The steam wagon came in two basic forms. The ''overtype'' designs looked like a cross between a traction engine and a lorry. The front resembled a traction engine by having a cab built around a horizontal fire-tube boiler with a round smokebox and chimney (e.g. Foden). The back resembled a lorry in having a load-carrying body and being built around a chassis. (A traction engine is constructed around the boiler and has no separate chassis.) The ''undertype'' designs have the engine ''under'' the chassis (although the boiler - usually a vertical type - remains in the cab), and generally resemble motor lorries rather than traction engines. Undertype designs often had the benefit of a more enclosed cab, and a much shorter length for the same carrying capacity. The earliest examples of either type had steel or wooden wheels, later followed by solid rubber tyres. Various developments, such as fully enclosed cabs and pneumatic tyres, were later tried by companies in a bid to compete with internal combustion engine-powered lorries. Some wagons built to run on solid tyres were later converted to pneumatic tyres. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「steam wagon」の詳細全文を読む スポンサード リンク
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