Tractor is a typical heavy-duty traction engine, which provides power for traction or trailer load. These are divided into two categories: heavy and medium-sized military and commercial rear wheel drive semi tractors for towing semi trailers, and very heavy typical off-road capabilities, usually 6 × 6. Military and commercial tractor units, including ballast tractors.
Tractors are usually equipped with large displacement diesel engines to improve power, durability and economy; Several axes; And a multi speed ratio transmission (10, 13 or 18 gears) to achieve transmission flexibility.
The tractor trailer combination distributes the load on multiple axles and is more maneuverable than a rigid truck of the same size. The most common trailer attachment system is the fifth wheel coupling, which allows rapid switching between trailers performing different functions, such as bulk dump trucks and box trailers. Trailers containing different cargoes can be quickly exchanged between tractors, eliminating downtime when the trailer is unloaded or loaded.
The drawbar coupling was also found, especially in the special super heavy ballast tractor, and was used as a means to connect the intermediate fifth wheel trolley to tow multiple semi trailers.
