Traction can bear part of the vertical mass of semi-trailer, and plays the role of traction semi-trailer, and is the steering mechanism of semi-trailer at the same time. Traction is mainly composed of a seat plate, a separation - connecting mechanism and a support.

Traction is divided into fixed type, lifting type and moving type according to whether the support can move. According to the different degrees of freedom allowed, there are single degrees of freedom, two degrees of freedom and three degrees of freedom, according to its separate - connecting mechanism is different, and divided into splint type and hook pin type. Fixed traction seat fixed traction seat is a kind of widely used at present, its support is fixed on the traction vehicle frame, the traction seat is allowed to have a certain degree of freedom on the support.

Single degree of freedom traction seat also known as I axis traction seat. It can only swing about an octave along the Y-axis. This kind of traction seat has higher driving stability, suitable for high speed, light load and high center of mass semitrailers on good road surface, which are used in large sets.

Packing

Semi-trailer and high cargo platform, bulk freight semi-trailer, but the frame bears a large torque.

After the tractor is connected to the semi-trailer, the safety baffle shall be moved to one side first, and then the handle shall be pulled to make the locking block move forward to the l-shaped gap leaving the splint. The spring shall be compressed, and the front end of the splint shall be pulled together under the fixed spring to resist the locking block. Then drive the traction car forward, that is to complete the trailer off. The supporting device of the semitrailer should also be put down before the suspension.