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The Vickers 6-Ton Tank or Vickers Mark E was the British light tank designed as a private project at Vickers. It was not purchaced by the British Army, but was picked up by a large number of foreign armed forces, and was copied almost identically as the Soviet T-26 and Polish 7TP. By the start of World War II it was the second most common tank design in the world, after the Renault FT-17.
The first Mark E was built in 1928, the design team including the famed tank designers John Carden and Vivian Loyd. The hull was made of rivetted steel plates, 1 inch thich on the front and most of the turrets, and about 3/4 inch thick on the rear of the hull. The power was provided by the Armstrong-Siddeley Puma engine of 80 to 95 horsepower (depending on the version), which drove the tank to 35km/h on roads.
The suspension used two axles, each of which mounted to a two-wheel bogie, to which a second set of bogies was connected with a leaf spring. Upward movement of either set of bogies would force the other down through the spring. This was considered to be a fairly good system and offered better than normal cross-country performance, although it could not compare with the contemporary Christie suspension. High strength steel tracks offered 5000 km of life, considerably better than most designs of the era.
The tank was built in two versions, the Type A had two turrets, each mounting a Vickers machine gun, while the Type B had a single turret mounting a single machine gun and short-barreled 47mm cannon in a single two-man turret. The Type B proved to be a real innovation, it was found that the two-man turret dramatically increased the rate of fire of either weapon, while still allowing both to be fired at the same time. This design, which they referred to as a duplex mounting, became common on almost all tanks designed after the Mark E.
The British Army evaluated the Mark E, but rejected it, apparently due to questions about the reliability of the suspension. Vickers then started advertizing the design to all buyers, and soon a trickle of orders started, eventually including USSR, Greece, Poland, Bolivia, Siam, Finland, Portugal, China and Bulgaria. A Thai order was placed, but taken over by the British when the war started. Vickers built a total of 153 (the most common figure) Mark E's.
Poland's examples showed that the engine tended to overheat due to poor airflow for the air-cooled Puma, which they addressed with the addition of large air vents on either side of the hull. For a new Belgian order the design was modified to mount the Rolls-Royce Phantom II water-cooled engine instead. This engine would not fit in the rear, and had to be mounted along the left side of the tank, requiring the turret to be moved to the right and rearward. One example of the resulting Mark F was tested by Belgium, but rejected. Nevertheless the new hull was used, with the older engine, in the sales for Finland and Siam.
The Mark E was also developed as a cargo vehicle, and purchased by the British Army in small numbers to haul their large 60-pounder artillery. Twelve were ordered by the Army as the Dragon, Medium Mark IV', while China purchased 23 and India 18.
Poland was generally happy with the design, and purchased 50 and licensed it for local production. Modifying it with larger air intakes, their own machine gun and a Diesel engine, the design entered service as the 7TP. Only the original 50, 38 sent assembled and 12 assembled locally, entered service. Out of 38 original two-turreted tanks, 22 were later converted to single turret version with a modified turret and the 47mm main gun.
The Soviets were also happy with the design and licensed it for production. However in their case local production started as the T-26, and eventually over 12,000 were built in various versions.
They were used in the following countries - in order of tanks' quantity:
See also: List of tanks.
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