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There are several types of wrecker beds used in the manufacture of tow trucks, or wreckers, from the simple single boom to the roll-back design. In heavy towing applications, the twin, swivel-type wrecker beds are commonly used due the ability of this type of wrecker to pull simultaneously in two different directions or at differing angles. The most familiar image that most people hold in their memory of tow trucks or wrecker beds is that of a vehicle being lifted at the bumper by a hook leading from the wrecker boom. In reality, the modern tow truck design does not lift with the boom at all; instead, the tow truck lifts and tows a vehicle by an apparatus known as a wheel lift, extending out from the rear of modern wrecker beds.
Though not typically used for the basic towing of a vehicle, most wrecker beds have a boom located in the center of the bed. The earliest versions of the wrecker boom consisted of a solidly-mounted steel boom that incorporated a swivel pulley mounted at the end of the boom. A large drum containing heavy steel cable was operated off of a power take off (PTO), powered by the engine, through the truck's transmission. The cable was routed up the boom and through the pulley, where it was fastened to a steel hook. The hook was attached to the vehicle being towed and the cable was spooled in on the drum, lifting the wheels of the vehicle off of the road and allowing it to be towed.
The modern wrecker beds contain one or more hydraulic booms that can be raised, lowered and swung left and right by hydraulic cylinders fed by a hydraulic pump on the truck's engine. The booms have steel cable running up and out of a pulley mounted on the end, similar to the earlier versions. This cable, however, is commonly controlled by an electric winch motor. The booms are used more for recovery of a wrecked vehicle and winching a vehicle up an embankment or similar obstacle. The actual lifting of the vehicle is accomplished by the use of a wheel lift, a hydraulically-operated apparatus mounted on the back of the tow truck.
Other versions of wrecker beds are roll-back units. These wrecker beds are a hydraulically-operated flatbed that tilts up to allow a vehicle to be winched onto the bed. Once in place, the vehicle and the bed are lowered back into a level position and hauled away. There are wrecker beds in many sizes, from those mounted on an average pickup truck to large units mounted on a semi truck chassis.