Six-Ton Tank M1917

[David]

One of the nations that decided to adapt the famous FT-17-tank was the United States. But unlike other countries, they didn't make a carbon copy of the french design. Specimen vehicles were obtained, and with manufacturers drawings these were shipped to the United States.

Owing to the differences in the French (metric) and American engineering standards, it became necessary to carry out a virtual redesign, which also incorporated a number of improvements and changes. The steel-rimmed wooden idler wheels of French design were replaced with all-steel types, a bulkhead was constructed between the engine and crew's compartment, the Renault engine was replaced with a 4-cylinder Buda with the addition of a self-starter; and a new gun mount was installed that would permit the mounting of either a .30 cal machine-gun or 37mm gun. Other visible changes was an exhaust muffler on the left side and a somewhat different front at the drivers compartment.

Under the code name of Six-Ton Special Tractor initial orders were placed for 1,200 vehicles, this was later increased to 4,400. The principal contractors for building the vehicles were the Van Dorn Iron Works, Maxwell Motor Co, and C. L. Best Tractor Co, all working under the supervision of the US Ordnance Department. By 11 November 1918, a total of 64 vehicles had been completed, ten of which actually arrived in France before the war ended. A total of 950 of the Six-Ton Tank were built before production ceased, and were the standard US light tanks until 1931. (Under the Lend-Lease Act in 1940 329 of these vehicles were sent to Canada where they were employed as training machines.) Weight: 7.25tons; crew 2; 1 37mm gun or I MG; armour 0.25-0.6in; engine Buda 4-cylinder 42hp water-cooled; 5.5mph; 16ft 5in x 5ft 10,5in x 7ft 7in.

Later in the 20-ies, they were modified further, mainly by introducing a sort of shield over the mantlet, strengthening the protection of the turret even more. And some years later, in an attempt to modernize the design further, by replacing the old Buda engine, that had never been completely satisfactory, with an air-cooled Franklin engine. During 1929, arrangements were made to install this engine in a Six-Ton Tank: this was achieved by removing the Buda engine complete with clutch, radiator with fan and other minor parts, enlarging the engine compartment, and installing a modified Franklin air-cooled engine complete with clutch and with fan on a crank shaft. New idler track rims were fitted to reduce the noise which would arise from the increased speed of the machine. With an increased speed of 10mph and the noice reduced by 50% the trials of the machine proved successful. The War Department decided to modify 6 additional vehicles for service with the Mechanised Force newly formed in 1930. A more powerful Franklin engine was used with suitable modifications to the cooling baffles. After delivery of these six modified tanks, the first modified version was reworked accordingly. Modifications of the 6ton 1917 model were later discontinued due to a decision by the Chief of Infantry.

The left Six-tonner below can be seen in the Patton Museum in Fort Knox Kentucky, comes courtesy of Bruce Tyo, who took it "in 1975 when I was there for the Armor Officer Basic course". The right six-tonner can be seen at West Point, and that photo at was taken by mr Tyo during a visit in 1989.

The Six-tonner is also the one in the Patton Museum in Fort Knox Kentucky, and has been photographed by Mike Casale.