The Three-Wheeled Steam Tank was a project created in 1918 and it was several new concepts offered to the United States Army

United States Army

The United States Army is the main branch of the United States Armed Forces responsible for land-based military operations. It is the largest and oldest established branch of the U.S. military, and is one of seven U.S. uniformed services...

 under a program begun enthusiastically the previous year. One of these was the Holt

Holt Manufacturing Company

The Holt Manufacturing Company traces its roots to the 1883 establishment of Stockton Wheel Service in Stockton, California, United States. Benjamin Holt, who was later credited with patenting the first workable crawler tractor design, incorporated the Holt Manufacturing Company in 1892...

 Three-Wheeled Steam Tank, which is not to be confused with the Engineer Corps' own steam tank, based on the British lozenge shape

Mark I tank

The British Mark I was a tracked vehicle developed by the British Army during the First World War and the world's first combat tank. The Mark I entered service in August 1916, and was first used in action on the morning of 15 September 1916 during the Battle of Flers-Courcelette, of the Somme...

.

Features

• Armament: One 75mm howitzer, two 12.7mm machine-guns
  Machine gun
  A machine gun is a fully automatic mounted or portable firearm, usually designed to fire rounds in quick succession from an ammunition belt or large-capacity magazine, typically at a rate of several hundred rounds per minute....
  
  .
• 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

History

It is not really a tank

Tank

A tank is a tracked, armoured fighting vehicle designed for front-line combat which combines operational mobility, tactical offensive, and defensive capabilities...

 in the sense that we know today as it has no caterpillar track

Caterpillar track

Continuous tracks or caterpillar tracks are a system of vehicle propulsion in which modular metal plates linked into a continuous band are driven by two or more wheels...

s. Instead it is more of a tractor

Tractor

A tractor is a vehicle specifically designed to deliver a high tractive effort at slow speeds, for the purposes of hauling a trailer or machinery used in agriculture or construction...

 being driven backwards with two large wheels at the front and a roller

Roller

The rollers are an Old World family, Coraciidae, of near passerine birds. The group gets its name from the aerial acrobatics some of these birds perform during courtship or territorial flights. Rollers resemble crows in size and build, and share the colourful appearance of kingfishers and...

 trailing behind. The main wheels were each powered by the steam engine

Steam engine

A steam engine is a heat engine that performs mechanical work using steam as its working fluid.Steam engines are external combustion engines, where the working fluid is separate from the combustion products. Non-combustion heat sources such as solar power, nuclear power or geothermal energy may be...

 which was fuelled by kerosene-fired boiler

Boiler

A boiler is a closed vessel in which water or other fluid is heated. The heated or vaporized fluid exits the boiler for use in various processes or heating applications.-Materials:...

s. 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

Skeleton tank

The Skeleton Tank was an experimental prototype tank built in 1918 by the Pioneer Tractor Company, Winona, Minnesota.The objective of this prototype was to develop a lightweight vehicle capable of crossing wide trenches in a manner similar to the then-conventional heavy British tanks...

, 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.