Tank
With World War II the multi-turreted tanks proved impracticable, and as the single turret on a low hull design became standard, crews became standardized around a crew of four or five. In those tanks with a fifth crew member, usually three were located in the turret (as described above) while the fifth was most often seated in the hull next to the driver, and operated the hull machine gun in addition to acting as a co-driver or radio operator. Well-designed crew stations, giving proper considerations to comfort and ergonomics, are an important factor in the combat effectiveness of a tank, as it limits fatigue and speeds up individual actions.
History of the tank
The first American-produced heavy tank was the 43.5-ton Mark VIII (sometimes known as the "Liberty"), a US-British development of the successful British heavy tank design, intended to equip the Allied forces. Armed with two 6-pounder cannons and five rifle-caliber machine guns, it was operated by an 11-man crew, and had a maximum speed of 6.5 miles per hour and a range of 50 miles. Because of production difficulties, only test vehicles were completed before the War ended. The American-built 6.5-ton M1917 light tank was a close copy of the French Renault FT. It had a maximum speed of 5.5 miles per hour and could travel 30 miles on its 30-gallon fuel capacity. Again, because of production delays, none were completed in time to see action. In the summer of 1918 a 3-ton, 2-man tank, (Ford 3-Ton M1918) originated by the Ford Motor Company was designed. It was powered by two Ford Model T, 4-cylinder engines, armed with a .30 inch machine gun, and had a maximum speed of 8 miles per hour. It was considered unsatisfactory as a fighting vehicle but to have possible value in other battlefield roles. An order was placed for 15,000, but only 15 were completed, and none saw service in the War.