The Medium Tank T1 was the final attempt to produce an effective tank on the basis of the earlier Medium Tank M1921, but although it was briefly accepted as the Medium Tank M1 it never entered production.
The earlier Medium Tank M1921 and Medium Tank M1922 suffered from problems with their Murray and Tregurtha marine engines, which never produced as much power as expected. Attempts to find an alternative engine failed, and Packard were given a contract to design a new purpose-built tank engine. This engine was ready by the summer of 1925, and was installed in the M1921, which then became known as the Phase 1 medium tank. At the same time the M1921 was used for tests with a medium pontoon bridge, which proved that a 23 ton tank could operate with existing equipment.
On 11 March 1926 the development of two separate tanks was approved - a lighter 15 ton model and a Phase 2 medium developed from the M1921 Phase 1. The lighter tank later became the Medium Tank T2, while the Phase 2 became the Medium Tank T1.
The T1 kept the basic design of the M1921, but with changes suggested by the test programme. Both the drive and idler wheels were raised off the ground, at a height that produced a level return run. New forged steel open tracks were used, with a single narrow bar running the full width of the track and four teeth running forwards from the bar.
The suspension was protected by side armour. The T1 used a similar turret to the M1921. This had a circular plan, with vertical sides. From the front the roof had a flat centre and sloped sides, with a second circular turret mounted on the rear of the main turret. The main turret was armed with a 57mm gun and coaxial machine gun in a spherical mantlet, and the mini turret carried a second machine gun.
The T1 prototype was build using soft steel plate instead of armour plate, a move that reduced the cost of the armoured surfaced by 90%.
The T1 was built at the Rock Island Arsenal, and was completed by May 1927. It went to the Aberdeen Proving Ground in September 1927 for tests, where it performed reasonably well. The 200hp Packard engine was judged to be 'rugged and dependable', but it was still underpowered. Top speed was 14mph, only 4mph faster than the M1921 and significantly slower than the Christie tanks that were being developed at the same time.
The T1 was a popular design, with both the Aberdeen Proving Ground and the Tank Board concluding that it was an improvement over existing designs. On 24 January 1928 the Ordnance Committee recommended that it should be standardized, and on 2 February it was approved for production as the Medium Tank M1. This didn't last, and a few months later the standardization was withdrawn.
The T1 was used as an experimental vehicle. In July 1928 it was given a 75mm pack howitzer M1920 in place of the 57mm gun. Special ammo was provided with a reduced charge that also reduced muzzle velocity and recoil, making it more practical in the small turret of the T1. Tests were carried out against the 6-ton Renault FT type, with great success.
In April 1932 the T1 was given a 338hp Liberty engine, and redesignated as the T1E1. This increased top speed from 14mph to 25mph, but the rest of the power train hadn't been improved to cope, and so the new engine caused frequent breakdowns.
Hull Length: 21ft 6in
Hull Width: 8ft
Height: 9ft 4.5in
Weight: 22 tons
Engine: Packard 8-cylinder water cooled 200hp
Max Speed: 14mph
Armament: One 57mm gun, two machine guns
Armour: 3/8 - 1in