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The Christie Medium Tank M1919 was designed in an attempt to produce a tank that could operate on wheels or tracks, in order to reduce the number of vehicles breaking down before getting into action.
During the First World War J. Walter Christie had produced a number of designs for gun motor carriages, including the Wheel-and-Track 8in GMC (or M.1918), which could carry an 8in howitzer and used four road wheels that could be run with or without tracks.
After the war Christie used this experience to produce a series of tanks that could operate with tracks when in combat, or just on their road wheels when out of combat, in order to reduce the high number of breakdowns caused by failures of the tank tracks. His original idea was to produce a single chassis that could be used as either a tank or a truck, but this then evolved into the Christie Medium Tank M1919. On 22 November 1919 the Army ordered a single example of the M1919 from Christie's Front Drive Motor Company, but it took some time to sort out the details, and the final specification wasn't approved until 8 June 1920.
The M1919 had a simple box hull, split into driver, gunner and engine compartments. It had a circular, flat sided turret with a flat top, armed with a 57mm gun in a large ball mount, with a coaxial .30in machine gun (the same mount was used on the Ordnance Department's Medium Tank M1921 and Medium Tank M1922). On top of the main turret was a smaller dome shaped turret that carried a ball-mounted Browning machine gun. Both turrets had a 360 degree traverse. The M191 was powered by a 120hp Christie 6-cylinder engine.
The main selling point of the M1919 was its suspension. At this point Christie had yet to develop the 'Christie suspension' for which he became famous, and the M1919 used a different system. It had four large wheels at the corners, each given rubber tires. The drive wheels were at the rear. In the middle was a centre bogie with two further road wheels carried on coil springs. This bogie could be raised for trackless running or lowered if tracks were installed, and could take the entire weight of the vehicle. The tracks were 15in wide, and had teeth on the inside that engaged with holes in the frame of the rear drive wheels to provide power.
The M1919 was delivered to the Aberdeen Proving Grounds in February 1921 and underwent tests that lasted until 21 April, when Christie asked for them to the suspended while he made modifications to the design. During this period the M1919 was driven for 374 miles, of which 37.5 were on tracks. It had a top speed of 7mph on tracks and 13mph on wheels, quite creditable for the time, although slower than the Medium Tank M1921, which would reach 10mph in the following year.
The rebuilt tank was delivered to the Aberdeen Proving Grounds in March 1922 as the Christie Medium Tank M1921. In the gap Christie had modified the suspension, removed the turret and placed the main guns in the hull front, but the M1921 didn't impress, and tests ended in July 1924.
Stats
Production:
Hull Length: 18ft 2in
Hull Width: 8ft 6in
Height: 8ft 9in
Crew: 3
Weight: 13.5 tons
Engine: Christie 6-cylinder 120hp water-cooled engine
Max Speed: 7mph (tracks), 13mph (wheels)
Armament: 57mm gun and one machine gun
Armour: 0.25-1in