Pickfords ballast tractor with exceptional load on specialist trailer. The tractor is a Scammell, and is connected to the trailer via a drawbar.
Heavy duty drawbar system on a truck
A drawbar is a solid coupling between a hauling vehicle and its hauled load. Drawbars are in common use with road trailers, both large and small, industrial and recreational.
The drawbar should not be confused with the fifth wheel coupling. The drawbar requires a trailer which either loads the drawbar lightly (for example a small boat trailer, or caravan, where a load of up to ~50 kg is part of correct trailer loading practice), or the load is the weight of the coupling components only (larger trailers, usually but not always with a steerable hauled axle, front or rear). The fifth wheel is designed to transmit a major proportion of the load's weight to the hauling vehicle.
Drawbars are not restricted to road haulage, nor to agricultural or similar use. A raillocomotive hauls its load through a drawbar and hauling force is transmitted between rolling stock via drawbars between units.
A drawbar is mounted or located on the tractive vehicle[1] and is used to accept the coupling of the load. The direction of haulage may be push or pull, though pushing tends to be for a pair of ballast tractors working one pulling and the other pushing an exceptional load on a specialist trailer.
Notes
^ With rail transport the tractive effort is "cascaded" through the train of wagons. Each wagon, even though unpowered, may be considered the tractive vehicle for the wagon(s) further away in the chain
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