Semi trailer is a trailer whose axle is placed behind the center of gravity of the vehicle and is equipped with a coupling device that can transfer horizontal and vertical forces to the tractor. It has no driving force and needs to be connected with the tractor with the help of the traction pin to realize driving with the help of the driving force of the main vehicle.

      Compared with full trailers, semi trailers are mainly used for long-distance cargo transportation, and can be subdivided in types. Different types of semi trailers are suitable for different goods. For example, the dump semi-trailer is suitable for the transportation of bulk goods such as coal, ore and construction materials, the low flat semi-trailer is suitable for the transportation of vehicles, machines and other heavy-duty goods, the warehouse grid semi-trailer is mainly used for the transportation of agricultural and sideline products and other light bubble goods, and the tank semi-trailer is mainly used for the transportation of liquids, bulk materials and bulk cement, The van semi-trailer can be used for the transportation of household appliances, light textile goods, building materials and drawing plate goods.

       What are the components of a semi-trailer? Generally speaking, semi-trailer can be divided into frame, top loading, traction pin, suspension system, traveling mechanism, electrical system, support device, protective device and trailer accessories.

      1. Frame, the main structure for loading goods, is composed of girder, welded I-beam, support beam, connecting beam, side beam, lock head, traction pin connecting device, panel, etc.

      2. Top loading refers to breast board, gantry, etc., and auxiliary frame to load goods.

      3. Traction pin, which is an important component connecting the semi-trailer and the tractor and bearing the traction force to drive the trailer forward.

      4. Suspension system is a device used to connect the frame and axle. It is mainly used to support the load and slow down the impact of vehicle and cargo dynamic load. It can generally be divided into steel plate suspension, single point suspension, air suspension and rigid suspension. There are differences in performance, and it needs to be selected according to the purpose of the vehicle.

       5. The traveling mechanism mainly refers to the axle system, steel ring and tire. Its main function is to bear and maintain the vehicle running, and support and distribute the load between the frame and wheels. At present, the axles that have done well in China are mainly BPW, Fuhua, Darong, York, etc. among them, the Darong axle with the highest cost performance is the most popular among users because of its reliable quality and low price.

       6. The electrical system, composed of cables, gas circuits and lamps, is mainly used for lighting, braking and safety warning.

      7. The supporting device is used to support the trailer when the semi-trailer is uncoupled.

       8. Protective devices can generally be divided into side protection and rear protection.

       9. Trailer accessories, such as tool box, spare wheel carrier, plug-in and other small accessories.

      Compared with the monobloc transport vehicle, the semi-trailer has better comprehensive economic benefits, can improve the transport efficiency by 30-50%, and can reduce the transport cost by 30-40%, which has played a certain role in promoting the organization form of the transportation industry.