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1918 photograph of the three-wheeled steam tank

The Three-Wheeled Steam Tank was a project created in 1918, and it was one of several new concepts offered to the United States Army under a program begun enthusiastically the previous year. One of these was the Holt Three-Wheeled Steam Tank, which is not to be confused with the Engineer Corps' own steam tank, based on the British lozenge shape.


  • Armament: One 75mm howitzer, two 12.7mm machine-guns.
  • Armour: 16mm
  • Crew: 6
  • Dimensions: Length - 6.78m; Width - 3.07m; Height - 3m.
  • Power Plant: Two 2-cylinder steam, 75 hp.
  • Speed: 5 mph
  • Range: Unknown


It is not really a tank in the sense that we know today, as it has no caterpillar tracks. Instead, it is more of a tractor being driven backwards with two large wheels at the front and a roller trailing behind. The main wheels were each powered by the steam engine, which was fuelled by kerosene-fired boilers. The three-part rear roller was fitted with a frame structure, and it was used to aid trench-crossing. The tank itself had a very high box structure. Like the Tracked Steam Tank and the Pioneer Company's Skeleton tank, which were produced in the same year, only one prototype was ever built. Although very impractical, it was much more heavily armed than its competitors.


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