The Medium Tank M1922 was a variant of the earlier M1921 adapted to use an experimental cable suspension system.
The M1921 was based on a specification issued by Brigadier General S. D. Rockenbach, chief of the tank corps, in 1919. The Ordnance department produced a design and then produced a mock-up. This was inspected, and an order for two prototypes issued in April 1920. Soon afterwards this order was altered, to allow the second prototype to use a flexible cable suspension system.
The M1922 was similar in overall layout to the M1921. It was powered by the same disappointing Murray and Tregurtha marine engine, which failed to produce the promised power levels. It used the same circular turret, which was armed with a 57mm main gun and coaxial machine gun and carried a smaller machine gun turret on its roof.
The suspension system used a flexible track system, with wooden track shoes 17in wide attacked to metal brackets, connected to a band. This ran over a series of small road wheels, which were held in place by a cable that ran between the road wheel assembly and similar wheels attached to the chassis. Suspension was provided by the tension in the cable. The wooden track shoes could move laterally, reducing the chance of shedding the track at higher speeds. The rear wheels were raised in an attempt to improve the tank's ability to climb out of trenches.
The M1922 was delivered to the Aberdeen Proving Grounds on 1 March 1923. The cable suspension system was a mixed blessing. It did provide better ride qualities than the standard suspensions of the day, and the M1922 was 5mph faster than the M1921, but the cables wore out too quickly and had to be replaced with more robust chains.
Like the M1921, the M1922 was used as an experimental vehicle, but any chance of it leading to a production vehicle ended when a new weight limit of 15 tons was imposed, to allow any new tank to use existing rail bridges and field pontoons. After the experimental work was complete the M1922 went to the Ordnance Museum.
Hull Length: 25ft 11in
Hull Width: 9ft 10in
Height: 9ft 11.5in
Weight: 25 tons
Engine: Murray-Tregurtha marine 6-cylinder engine, 250hp
Max Speed: 15mph
Armament: One 57mm gun and two machine guns
Armour: 3/8 to 1in