A heavy duty wrecker is a variety of tow truck designed to haul extremely large vehicles. Like other tow trucks, the purpose of a heavy duty wrecker is to transport a disabled vehicle from one point to another without driving that disabled vehicle. It is instead pulled behind the tow truck or hauled on a flat bed mounted on the truck. Heavy duty tow trucks are sometimes known as "wreckers" because they very often haul "wrecks," or vehicles that are extremely damaged from car accidents or other incidents.
The primary use of a heavy duty wrecker is to haul large vehicles, so the tow truck itself will need to be quite large as well. It is likely that it will feature several axles and wheels to accommodate the extra towing strain, as well as the extra weight of the vehicle being towed, and the heavy duty wrecker is likely to feature a very large diesel engine designed to produce a significant amount of torque. Two general types of wreckers are commonly used: flatbeds and boom trucks. Flatbeds require the vehicle being towed to be pulled onto the truck's bed, which is done by tilting the bed at an angle using a lift and hauling the vehicle onto the bed using a series of cables.
Most heavy duty wrecker models use a boom, however, since many of the vehicles this type of wrecker will haul will be too large to be mounted on a flat bed. Freight trucks and big rigs, for example, are far too large to fit on a flat bed, so a boom is instead outfitted with a cable and pulley system that will hoist the truck's front wheels off the ground. Sometimes a hydraulic arm is used instead to support the front wheels and lift them off the ground so the vehicle can be towed, or a combination of the two systems may be used for the best safety and security.
The boom arm is controlled by hydraulic cylinders that can be operated using hand switches mounted on the side or in the cab of the truck. The strength and versatility of the hydraulic arms make the heavy duty wrecker an ideal choice for a variety of towing purposes, and the height and length of the boom arm will determine how large of a vehicle can be towed safely using the tow truck.