"Tractor-trailer" is a noun we frequently see. For example, in the question bank of the driver's license test, we frequently see "no tractor-trailer during the internship period", which refers to the behavior of pulling the rear carriage with a vehicle. In fact, tractor-trailer in addition to this level of verb meaning, also specifically refers to a very widely used in the logistics and transportation industry.
In general, tractor-trailer refers to a type of vehicle that has no driving capacity of its own and is mainly used to provide cargo loading space and load-bearing capacity. It relies on the traction power provided by the tractor in front to realize driving. With the continuous development of the automobile industry, more and more traction models emerge gradually.
In terms of types, tractor-trailers can be mainly divided into the following categories:
1. Semi-trailer.
At present, the semi-trailer is the most widely used type of car in domestic road transportation. Its axle is installed at the rear of the car, so it cannot independently realize stable standing. It is necessary to build the front section of the car on the traction car, and keep it upright by relying on the supporting force provided by the tractor. In other words, the tractor needs to install a special traction saddle at the rear of the body, which is used to bear part of the weight of the semi-trailer car and provide traction power at the same time. After the semi-trailer is detached from the tractor, special legs are needed for support.
Semi Trailer price can be subdivided into plate type, gooseneck type, concave beam type, bar type, panel type, van type, container type, tank type, dump type, skeleton type and other types. It has strong stability in high-speed driving, simple matching of main hangings, flexible application and strong bearing capacity, especially suitable for long-distance transportation and elevated-grade highway transportation. There is no steering.
2. Full trailer.
The full trailer is opposite to the semi-trailer. The biggest difference is that the full trailer can realize independent standing, and its axle installation distribution can bear the weight of the carriage evenly, so it can stand upright smoothly even if it is not connected with the tractor. The tractor in front only needs to provide traction power, so it can be connected with hooks.
A typical full trailer is typically composed of frame, cargo platform (top), traction bar (frame), steering device, suspension, braking system, signal system and so on. Compared with semi-trailer, full trailer has stronger driving stability in mountainous areas or rough roads, which is mainly due to the traction bar or traction frame between it and the tractor can swing up and down and left and right. However, the disadvantages are relatively obvious. Under the condition of high speed driving, the stability is poor, and it is easy to see accidents such as brake tail rejection and traction frame fracture, so it is mainly used for transportation in the field of wharfs, factories and ports.
3. Middle axle trailer.
As the name implies, the central axle trailer refers to a trailer whose axle is located in the center of the center of gravity of the carriage. When detached from the tractor, it cannot support its weight independently. It is mainly composed of the carriage, traction device and axle, and the connecting device with the tractor can swing from side to side, but cannot move up and down.
Compared with other trailers, the middle axle trailer has the characteristics of low center of gravity, light dead weight, simple structure, etc., but because it is only suitable for elevated grade highway application, it is more suitable for fixed special line transportation. According to the standard of GB1589, the central axle trailer has a certain advantage in the size of the outer profile, which may alter the status quo of the semi-trailer under continuous development.
4. Light tractor-trailer.
Different from other tractor-trailers, the main role of light tractor-trailers is not in the transport of goods, such as soiling-in trailers, that is, we frequently say RV, with passenger cars or light trucks can achieve traction, the application is more extensive and convenient.
Light tractor-trailer can be subdivided into light tractor-semi-trailer and light mid-axle tractor-trailer. From the functional point of view, the carrying capacity of light traction semi trailer is stronger and the driving is more stable; the light-duty mid-axle tractor-trailer can stand independently and stably, but the mid-axle carriage is easy to be offset in the transverse wind when the load is large at high speed.
Above is the current domestic more common four tractor-trailer models. It is worth noting that, no matter what kind of tractor-trailer, you must get the corresponding license qualification to drive, among which semi-trailer, full trailer, mid-axle trailer need A2 license, light tractor-trailer need C6 license. Although light tractor-trailers can be towed by passenger cars, at present only A2 driver's licenses are compatible with the quasi-driving version of C6 driver's licenses, and other types who want to drive tractor-trailers must apply for additional driving.