The Christie M1931/ Medium Tank T3/ Combat Car T1 was the first of Christie's tanks to be accepted for production by the US Army, and was used in small numbers by the infantry at the Medium Tank T3 and the cavalry as the Combat Car T1.
In 1928 Christie produced the M1928, effectively a demonstration vehicle for his new suspension system (to become famous as the Christie suspension). This had four large road wheels on each side, each carried on a pivoting army that was supported by a large coil spring. Power came from a rear drive wheel. When tracks were in use, tongues on the back of the tracks engaged rollers in the drive wheel. When the vehicle was running on the road wheels alone chains linked the drive wheel to the rear road wheels. In either configuration the M1928 reached impressive speeds, with a top speed of 70mph on wheels and 41mph on tracks.
The Army decided to order a tank based on the M1928, equipped with a 37mm gun in a fully traversing turret. The first of these was delivered as the M1931, early in 1931, and was the first of seven to be produced by Christie for the US Army. When used by the infantry they were known as the Convertible Medium Tank T3, when used by the cavalry as the Combat Car T1.
During the development and production of the T3 the relationship between Christie and the US Army broke down, and although the Convertible Medium Tank T4 used Christie's convertible suspension system, it was built at the Rock Island Arsenal.
Our two main sources of information on the T3, Chamberlain and Ellis's Tanks of the World and Hunnicutt's History of the American Medium Tank disagree on the exact details of the development of the T3, although the overall picture is similar.
The M1931 was Christie's designation for the modified version of the M1928 when given a turret and proper military equipment.
Both sources agree that the Army received seven T3s built by Christie's US Wheel Track Layer Corporation, but give slightly different details.
Chamberlain and Ellis have the army place an order for five modified M1928s after a demonstration in October 1930. These were accepted as the convertible medium tank T3. Another two tanks were ordered by Poland, but not paid for, and went to the US Army as the T3E1.
Hunnicutt has Christie receiving a contract for one M1931, to be delivered in October 1930, followed by a contract for seven M1931s with the designation convertible medium tank T3 placed on 12 June 1931. The first T3 was delivered for tests on 9 October 1931, and the seventh was accepted in March 1932.
These two accounts can be made to fit with each other if, as sometimes happened, the contract of 12 June 1931 replaced a series of earlier contracts. The first would cover the single M1931, which after tests was found to need modifications. The second contract would cover the five T3s the army wanted, possibly including the modified M1931. The final contract of June 1931 would then cover the full price of the five T3s and the two Polish tanks.
The T3 was armed with a 37mm gun and coaxial .50in machine gun carried in a combination mount in a circular, vertical sided and flat roofed turret. Our sources disagree on the number of crew carried, with Hunnicutt giving it a crew of two - driver in the pointed nose and gunner in the turret, and Chamberlain and Ellis a crew of three. Photographic evidence supports Hunnicutt.
Both sources agree that the T3E1 was similar to the T3, but used a gear drive instead of chains when the tracks were removed. Chamberlain and Ellis say that two were delivered, and that they came from the Polish order. Hunnicutt says that one T3E1 was tested at Aberdeen. Again, these two accounts aren't directly contradictory.
Combat Car T1
The Combat Car T1 was the designation given to four T3s that went to the Cavalry at Fort Knox, Kentucky. At this point only the infantry was officially allowed to use tanks, and so all armoured vehicles in the Cavalry were known as combat cars. The Combat Car T1 had the 37mm gun from the turret replaced by a .50in machine gun
Both sources agree on the T3E2. After falling out with Christie the Army ordered five modified T3s from the American-La France and Foamite Corporation of New York. The new version was given a flatter and wider nose, which allowed it to carry a .30in machine gun for the driver. A larger two-man turret with sloped sides was introduced. This carried the same 37mm gun and .30in machine gun in the front, but also had one machine gun on each side and one on the rear, for a total of four in the turret and five overall. The T3E2 was given a more powerful 435hp Curtiss D-12 engine, which increased its top speed on tracks from 27mph to 35mph (although this was limited to a lower speed in use to avoid excessive wear).
Our sources differ on the T3E3. Chamberlain and Ellis have it as a new version, built by the American-La France and Foamite Company in 1936, and with controlled differential steering. Hunnicutt has the T3E3 as the designation given to the T3E2 after sixty minor modifications were carried out. This seems to be the more convincing account.
Hull Length: 18ft
Hull Width: 7ft 4in
Height: 7ft 6in
Engine: Liberty V-12 338hp
Max Speed: 46mph on wheels, 27mph on tracks
Armament: 37mm gun and one machine gun as tank, two machine guns as Combat Car
Armour: 5/8 to 1/2 in
Hull Length: 18ft 9in
Hull Width: 8ft
Height: 7ft 8in
Weight: 11.5 tons
Engine: Curtiss 12-cylinder 435hp
Max Speed: 58mph wheels, 35mph tracks
Armament: One 37mm gun, five machine guns