Semi-trailers are an indispensable tool in modern cargo transportation. There's complex engineering and physics involved in how it works, but in this article, we'll take a closer look at its core components: the carriage and traction system.

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1. Bracket: support system of semi-trailer

The bracket is the bottom structure of the semi-trailer and plays a role in supporting and balancing the cargo. It is usually constructed of a sturdy metal frame that has the appropriate strength to bear the weight of the cargo it carries. This frame is usually mounted with one or more axle sets, and the wheels are mounted on the axle sets.

Axle set: An axle set usually consists of one or more pairs of wheels, and each pair of wheels is called an axle. These axle groups are precisely arranged under the brackets to ensure an even distribution of cargo and reduce the load on the semi-trailer. This helps improve security and stability.

Air suspension system: Some semi-trailers are also equipped with an air suspension system that can be adjusted according to the weight of the cargo carried to maintain proper ground clearance and suspension balance.

2. Traction system: the link between the semi-trailer and the trailer

The traction system is the connection between the semi-trailer and the tractor (usually a truck). It has several key components:

Tow Head: The tow head is the structure at the front of the semitrailer that usually includes a special interface that connects to the tow vehicle's tow hitch. This interface is called the "fifth wheel" because it is the fifth connection point among the four wheels.

Fifth Wheel: A fifth wheel is a rotatable structure on a semitrailer that rotates on the tractor's tow hitch, allowing the semitrailer to turn. It is often used in conjunction with a mop head to provide a stable connection.

Connecting Rods and Support Legs: Some semi-trailers are equipped with connecting rods to ensure that the semi-trailer remains level when connected and disconnected. In addition, the support legs can support the semitrailer when it is not connected to the tractor, ensuring that it remains stable.

When the tractor is connected to the semitrailer, the tow hook will be inserted into the fifth wheel to ensure they are securely connected. This connection is reliable and safe, allowing the semi-trailer to follow the tractor and carry its cargo. At the same time, through the rotation of the fifth wheel, the semi-trailer can follow the path of the tractor when turning.

To sum up, the working principle of a semi-trailer involves the connection of the support structure of the bracket and the traction system, which work together to ensure that the goods are transported safely and smoothly. The principles of materials science, physics, and engineering behind this project have made semi-trailers an integral part of modern freight transportation.