page_title: M6 heavy tank
section_title: Development
hierarchical_section_title: M6 heavy tank / Development
caption_attribution_description: A U.S. Army M6 heavy tank in December 1941. Original caption: "Delivery of the first heavy tanks. This is the new fifty-seven-ton tank, known as the M-1 in the initial demonstration. Notice that the gun turrets are on the top, making it possible for the tank to take advantage of irregular land, sheltering the lower part and shooting from revolving turrets on top. In the turret are three-inch guns and a thirty-seven-millimeter antiaircraft gun."
context_page_description: The Heavy Tank M6 was an American heavy tank designed during World War II. The tank was produced in small numbers and never saw combat.
context_section_description: Because of limited budgets for tank development in the interwar years, at the outbreak of World War II the US Army possessed few tanks, though it had been keeping track of the use of tanks in Europe and Asia. Successful employment of armored units in 1939–40, mostly by the Germans, gave momentum to a number of US tank programs, including a heavy tank. The United States possessed a massive industrial infrastructure and large numbers of engineers that would allow for mass production of tanks.
  Following the Chief of Infantry recommendation from May 1940, the US Army Ordnance Corps started to work on a 50-ton heavy tank design. The project was approved in June and the vehicle received the designation Heavy Tank T1.
  Initially, a multi-turreted design was proposed, with two main turrets each armed with a low-velocity T6 75 mm (2.95 inch) gun, a secondary turret with a 37 mm gun and a coaxial .30 caliber (7.62 mm) machine gun, and another secondary turret with a 20 mm gun and a coaxial .30 caliber machine gun. Four .30 caliber machine guns were to be installed in ball mounts, two in the glacis (front) plate and two in the rear corners of the hull. The design was somewhat similar in concept to multi-turreted breakthrough tanks developed in Europe in the 1920s and throughout the 1930s, such as the 1925 British Vickers A1E1 Independent or the Soviet T-35 of the early 1930s, albeit on a much more powerful scale: the older tank designs were typically armed with a single light or medium-caliber main gun and multiple machine guns, and had armor only sufficient to protect from small arms fire. Later in the decade, however, European tank developers switched to single-turret designs.
  By October, the US developers reached the same conclusion as their European counterparts. The armament was changed to a single vertically stabilized 3-inch (76.2 mm) gun and a coaxial 37 mm gun in a single three-man turret with both manual and electric traverse. The turret had a commander's cupola identical to that of the M3 Medium Tank. Additional armament consisted of two .50 caliber machine guns in a bow mount (operated by the assistant driver), two .30 caliber machine guns in the front plate (fired electrically by the driver), one .30 caliber in the commander's cupola and one .50 caliber in a rotor mount for anti-aircraft use in the right rear of the turret roof (operated by the loader). The crew consisted of commander (seated in the turret left), gunner to the right of the gun, gun loader (turret), driver and assistant driver in the front left and right of the hull respectively, and another crewman in the hull to pass ammunition to the turret.
  One of the main challenges was developing a powerpack for such a heavy vehicle. The Wright G-200 air-cooled radial gasoline engine was selected by a committee formed by the Society of Automotive Engineers, but no suitable transmission was available. The committee recommended developing a hydramatic transmission, while a possibility of using a torque converter or an electric transmission was also to be checked.
  The project was first publicly disclosed in August 1940 when the Army awarded Baldwin Locomotive Works in Pennsylvania a $5.7 million contract for the production of 50 tanks. The Army envisioned building 500 of this type.
  The first T1E1 was delivered to the Army in December 1941. From 1941 to 1942, three prototypes were built. One with electric transmission and two with torque converter transmission. Variants with hydramatic transmission were never completed. The prototypes also differed in hull assembly method— one had a welded hull and two had cast hulls.
  On 26 May 1942, two variants with torque converter transmission were standardized as M6 and M6A1. Standardization of the electric transmission equipped T1E1 as the M6A2 was never approved, but the manufacturing of the vehicle was nevertheless recommended. It was proposed by the Ordnance Corps that 115 T1E1s would be built for the US Army for "extended service tests", between that and Services of Supply instruction to increase production with the balance g
caption: Side view
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