7TP - Design

Design

The 7TP was the Polish development of the British Vickers 6-ton Mark E tank licence. Comparing to Vickers, the main new features of 7TP were: a better, more reliable and powerful diesel engine, a 37 mm anti-tank gun, thicker armour (17 mm instead of 13 mm on the front), modified ventilation, the Gundlach tank periscope, and a radio. About 132 tanks were produced between 1935 and the outbreak of the war, plus four iron prototypes. The designation 7TP meant "7 Tonne, Polish" (in fact its weight increased to 9 tonnes after the initial prototype).

The 7TP was the world's first diesel-powered tank. Japanese Type 89B I-Go Otsu also used diesel engines but since 1936 (earlier tanks had gasoline engines). The diesel oil used as fuel had an important advantage of being much less flammable than gasoline.

Like its British predecessor, the 7TP was initially produced in two variants: twin turret version armed with 2 Ckm wz.30 machine guns, and a single turret version, armed with 37 mm Bofors wz. 37 gun. After initial tests, it became clear that the twin-turret variant was obsolete and lacked firepower, so it was abandoned in favour of the more modern single turret design.

Prior to the outbreak of World War II most of the twin turret tanks were converted to single turret versions and only 24 twin-turret types remained in Polish service (as opposed to roughly 108 of the other type). It is to be noted that twin and single turret variants had no specific designations. In some modern books they are unofficially designated "7TP dw." and "7TP jw." (Polish abbreviations for dwuwieżowy - dual turreted; jednowieżowy - single turreted).

In 1938 Państwowe Zakłady Inżynierii also produced 13 prototype models of a better armored version of the 7TP - the 9TP. Although the 9TP never entered production, these prototypes were used in the defense of Warsaw in September 1939.