Tank transporter

A tank transporter is a combination of a heavy tractor unit and mating semi-trailer, typically a Lowboy (trailer), used for transporting tanks. Some also function as tank recovery vehicles, the tractors of which may be armored for protection in combat conditions.

Used on the road, tank transporters limit the wear on tracks and drive trains of tracked vehicles. They also conserve fuel, are less damaging of road surfaces, and are overall more efficient moving tanks at high speeds than tanks operating at them even if they are capable.

Three chassis designs have been used, generally in this order over time as loads became heavier, although there are exceptions.

The lighter tanks of the inter-war period were carried on simple rigid flatbed lorries.

As the weight of tanks became too much for lorry chassis, separate trailers were developed. These carried the entire weight of the tank on their own wheels, putting no weight onto the tractor unit. They are pulled by a ballast tractor connected to a drawbar.

The simplest trailer designs have only two axles, but heavier loads frequently require more than this. Multiple wheels per axle are common, usually four, sometimes eight.

One advantage of ballast tractors is that they're capable of double-heading, where two tractor units are coupled to pull a particularly heavy trailer.

Some designs, such as the 1928 Aldershot design, grouped pairs of axles at each end of the trailer.

Others, such as the 70-ton Cranes trailer illustrated here beneath the Tortoise had five axles, spaced along the length of the trailer. The end-wheel designs have the advantages of better ability to cross rough ground and steering more easily. Those with axles throughout their length must have suspension that allows the axles to move and also allowing some steering. This makes them more complicated to manufacture. Placing the wheels at the ends also allows the chassis to dip down into a "well", giving a lower centre of gravity during transport. The Cranes' trailer had a frame split into two sections of two and three axles, with a further carrying bed above them. The outermost four axles had Ackermann steering for their wheels.

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