Armour - Tank - Britannica

Mobility

In spite of the progressive increases in weight, tanks’ speed and agility actually increased because they were provided with more powerful engines. After World War II, tank engines had an output of 500 to 800 horsepower, but, starting with the MBT-70, their output increased to 1,500 horsepower. Engines of this power were installed in the M1 and the Leopard 2, giving them power-to-weight ratios of more than 20 horsepower per ton.

Most tank engines of the immediate postwar years had 12 cylinders in a V-configuration and at first were of the spark-ignition gasoline type. But Soviet tanks already had diesel engines, and from the 1960s almost all tanks were diesel-powered. This increased their range of operation because of the greater thermal efficiency of the diesels, and it reduced the risk of catastrophic fires that could erupt if the armour was perforated by enemy weapons.

The development of gas turbines led in the 1960s to the use of one, in combination with a diesel engine, in the Swedish S-tank. After that, a 1,500-horsepower gas turbine was adopted to power by itself the M1 and M1A1. A gas turbine also powered the Soviet T-80, introduced in the 1980s. All other new tanks of the 1980s continued to be powered by diesels because of their greater fuel economy.

Since the speed of tanks over rough ground depended not only on the power of their engines but also on the effectiveness of their suspensions, the latter developed considerably in the postwar era. Almost all tanks adopted independently located road wheels, sprung in most cases by transversely located torsion bars. Exceptions to this were the Centurion and Chieftain and the Merkava, which used coil springs. To improve their ride over rough ground still further, most tanks built during the 1980s were fitted with hydropneumatic instead of metallic spring units.