The center axle trailer is a new type of vehicle after GB1589. Its axle is installed in the center of the gravity center of the vehicle body. When the car is separated from the tractor, it cannot maintain balance independently. The center axle motor train belongs to the motor train. It is a vehicle type composed of a car and a center axle trailer. In short, it is a combination of one or more center axle trailers towed behind a car.

The common mid axle motor trains in daily life can be divided into the following categories:

1. Heavy truck+middle axle carriage

An automobile train composed of heavy trucks and center axle trailers belongs to a kind of freight train.

According to the requirements of laws and regulations, the length limit of freight train is 20m, which has obvious advantages compared with 13.75m for semi-trailer, 13.95m for container semi-trailer and 17.1m for articulated train.

The application of freight trains is relatively mature abroad, especially in Europe. In contrast, in China, due to differences in road conditions, vehicle technology and other fields, the application of freight trains is rare. Although some vehicle enterprises have also launched a lot of prototype vehicles of mid axle vehicle trains, they have been calm in the industry.

2. Mid axle vehicle carrier

The center axle vehicle transport vehicle belongs to a special freight train, which is specially used to transport cars or passenger cars. The main vehicle is a vehicle transport vehicle, and the trailer is a center axle vehicle transport trailer.

In terms of appearance, the center axle vehicle carrier is generally equipped with two cargo platforms, and both the main vehicle and trailer can load.

According to the provisions of the new GB1589, the length limit of the mid set vehicle transport train is 22m, which is 2m longer than the freight train.

At present, other major types of car carriers in China, such as flat tractor+semi-trailer can be loaded with 6 cars, long tractor+semi-trailer can be loaded with 7 cars, and mid axle vehicle carriers can be loaded with 8-11 cars.

3. Light truck+mid axle carriage

The light trucks referred to here mainly include light trucks, micro trucks, passenger and freight vehicles, pickup trucks, off-road trucks, special operation vehicles, etc.

Different from the form of heavy truck+center axle trailer, the main vehicle of this kind of freight train is generally hung with a blue card. The length of the mid axle carriage is generally about 7m, and the rated load is 2.4t. With the light truck in front, the loading capacity can reach about 4.5t, and the length is about 12m. Its length and loading capacity have far exceeded 6 × 8 Cargo box.

It is worth noting that although the license plate of this model is blue, it still belongs to the category of freight train. Once the mid axle carriage is towed, it must be driven by A2 license.

4. Passenger car+mid axle compartment

This type of vehicle belongs to passenger vehicle trains. Almost all kinds of passenger vehicles can form passenger vehicle trains with center axle trailers, among which the most commonly used are general passenger vehicles (sedans) at all levels, multipurpose passenger vehicles and off-road passenger vehicles. The middle axle cars towed by this model are generally single axle or double axle cars.

Since the introduction of C6 driver's license, it is allowed to drive passenger cars to tow middle axle carriages, but the total mass of the main vehicle+trailer must be less than (not including) 4500kg. If this standard is exceeded, only A2 driver's license can be used.

As mentioned above, although the mid axle motor train is widely used abroad, it is not mature in China. What are the reasons?

1. The purchase cost is higher.

Compared with ordinary trucks or semi trailers, the purchase cost and maintenance cost of middle axle trailers are higher, especially for middle axle motor trains. Under the influence of the epidemic, the living environment of the freight market is getting worse and worse. Many car owners are unable to get orders and make money. They prefer practical, low cost, high return models. The price of mid axle trains is high, and the transport scenarios are limited, so car owners naturally will not consider it.

2. Poor driving stability.

The wheels of the center axle trailer are in the middle of the carriage, and the body is easy to swing up and down or left and right when running. In addition, the connection point between the center axle trailer and the main vehicle is under the frame, which makes the movement of the rear trailer more flexible. When the speed is too fast or the road is slippery in rainy days, the tail flick is easy to occur, and in serious cases, the whole vehicle may even be out of control and roll.

3. High requirements for road conditions.

The middle axle trailer has a low chassis. Although it has advantages on the road with limited height, at the same time, the low chassis is easy to cause the vehicle to be unable to adapt to poor road conditions.

4. Driving is difficult.

Although theoretically, the middle axle truck train has a low chassis, a short wheelbase, and is simpler to drive than the full trailer, in practical application, many car owners report that the middle axle trailer is "difficult to turn", "always wobbles when driving", and "can only be driven with a little technology".

5. Pressure on other models.

At present, the domestic medium and long distance transportation market is dominated by semi-trailer, which can meet the transportation demand of most goods in terms of loading capacity, carrying capacity and applicable working conditions. The most important thing is that the semi-trailer market is very mature and has a relatively rich variety, and its position in the Jianghu may not be shaken in a short time.

Of course, since GB1589 has added the central axle motor train announcement, it shows that it still has certain advantages:

1. In terms of loading capacity, its maximum capacity can reach about 120 square meters, which is equivalent to two traditional 9 × 6 Compliance loading capacity of freight cars;

2. The chassis is low and the center of gravity is low. Under the same turning radius, the mid axle car train can do longer;

3. The trailer is flexible and suitable for express, less than carload, and dump transportation, especially in special line logistics;

4. One vehicle can be used for two purposes. The main vehicle can be used alone or the trailer can be used. The use form can be flexibly selected according to the transportation demand.

From the perspective of the development of the current domestic transport market, modularization and standardization are the major trends. Although there are still many problems in the middle axle trailer, its market coverage may also be improved to some extent with the implementation of policies, the progress of technology and the continuous improvement of related supporting facilities.