A semi-trailer is a trailer in which the axles are placed behind the center of gravity of the vehicle and are equipped with combined equipment that can transmit horizontal and vertical forces to the tractor. The semi-trailer frame is mainly composed of beams, welded I-beams, support beams, connecting beams, side beams, lock heads, traction pin connection equipment, panels, etc. It is necessary to introduce the nine main components of the semi-trailer.

1. Side beams are usually channel steel or bending parts. Now most trailers use channel steel, and there will be more side beams for light body hanging bending parts, because the requirement for strength is not too large. The support beam is the through beam, and most of them are now W beams.

2. For the fence car, the upper part refers to the fence board, gantry and so on. The fence is divided into flat plate and vertical corrugated board. Vertical corrugated board is a typical board, and its strength will be higher. The gantry can also be called a "front stop". Usually, the manufacturer will be detachable if it is not specially requested. Therefore, the gantry must be welded to death and two diagonal pulls are added for the goods that are often pulled heavy and easy to slide. . 

3. The traction pin is the main component that connects the semi-trailer and the tractor and accepts the traction force, and is connected with the traction seat. Usually forged from steel of chrome alloy construction. There are 50# traction pins and 90# traction pins for different cargo tonnage. Usually, the total weight of the trailer and the goods is limited to 50T. Below 50T, use 50# pins. Above 50T, use 90#. If it is above 90T, use 90# traction pins. 

4. The semi-trailer suspension is made of non-independent steel plate stamping rigid suspension, which is composed of tandem leaf springs and suspension supports, which are used to support the load and reduce the impact of the dynamic load of the vehicle. There are four commonly used suspensions: tandem leaf spring balance suspension, single-point suspension, air suspension, and rigid suspension (one line and two axles). 

5. The axle of the semi-trailer is a support axle. The axle is connected to the frame through leaf springs and tie rods and suspension equipment to support and transmit the force of the load between the frame and the wheels. 

6. The electrical system of the semi-trailer is composed of seven-core sockets, cables, gas circuits, various lamps, etc., which are used for lighting, safety warnings, and air supply for brakes. 

7. The supporting equipment of the semi-trailer is mainly used to support the trailer when it is detached, and is composed of outriggers, connecting brackets, etc. 

8. Semi-trailer protective equipment consists of side protection and rear protection to protect pedestrians and other vehicles from getting under the semi-trailer. This thing is also fuel-efficient when it is done well, and it is called a side skirt when the wind resistance is done well.

9. Other accessories on the semi-trailer include tool boxes, spare tire racks, gantry racks, stakes, etc. There are also some small accessories such as rope tighteners, rope hooks and other highly functional accessories, which should be selected according to their own product varieties.