In the freight industry, trailers can be divided into three types: semi-trailer, full-trailer and centre-axle trailer. Among them, full-trailer and semi-trailer appear relatively early in China, and owners are familiar with them. However, centre-axle trailer is not well known in China, and owners have relatively little contact with them.

After the update of GB1589, the centre-axle trailer has become a model encouraged by the policy, and its market popularity has also continued to rise. Many automobile enterprises have also applied for the centre-axle trailer model.

So, according to the requirements of laws and regulations, how long can a centre-axle trailer be? This is determined according to the model of the trailer with central axle.

The overall length of the centre-axle trailer shall not exceed 12m, the width shall not exceed 2.55m, and the height shall not exceed 4m;

The maximum length of the outline of the transport train of the centre-axle vehicle can reach 22m, and the width and height limits are the same as those of the centre-axle trailer;

The maximum outer length of the centre-axle freight train is 20m, and its width and height are the same as that of the centre-axle trailer.

As for the total mass limit, the limit of one-axle centre-axle trailer is 10t, the limit of two-axle centre-axle trailer is 18t, the limit of three-axle centre-axle trailer is 24t, the maximum gross weight limit of four-axle centre-axle freight train is 36t, the maximum gross weight limit of five-axle centre-axle freight train is 43t, and the total weight limit of six-axle centre-axle freight train is 49t.

In the above models, the centre-axle trailer is similar to the semi-trailer, except that the installation position of the axle is different, and the types of goods loaded and transported are generally unlimited;

The central axle vehicle transport train refers to the central axle car transport vehicle, which is specially used to transport small passenger cars such as sedans and vans;

Center-axle freight trains are more widely used in the field of general cargo transportation, such as express, less-than-truckload and light-weight cargo transportation. The upper loading structure is mainly box-type, with a volume of up to 120 square meters, and the loading capacity is very considerable. Especially after the emergence of drop-and-drag transportation, the center-axle freight trains are flexible, which can quickly realize the trailer replacement, and improve the loading and unloading and transportation efficiency.

In addition to the advantages in loading capacity, the centre-axle trailer also has the characteristics of low center of gravity and low chassis, which can improve the driving stability, reduce the carriage height to a greater extent, and improve the cargo loading space within the scope of compliance; Secondly, centre-axle trailers have a relatively strong turn-through ability, because their axles are in the middle of the carriage, with short wheelbase and small turning radius, so centre-axle trailers can often do longer under the same turning radius.

Because of this, the popularity of mid-axle trailer is very high in foreign countries, and it has almost become the main model of trailer in Europe and America. However, since the promotion of mid-axle trailers, the domestic market has received little response to it. What is the reason?

It is mainly based on differences in national conditions. It is understood that in the European and American freight markets, the operation of road transport vehicles requires fast loading and unloading, high efficiency of short loading and unloading, universal hitch-and-drop mode, good traffic order, special vehicles for special use, high illegal cost of overloading and overrunning, and almost standardized operation. In addition to its sparsely populated land and wide road space, the length of the centre-axle trailer is extended to 25m with a higher loading rate, These factors have promoted the development and application of central axle vehicles to a certain extent.

In addition, the disadvantages of the mid-axle trailer that cannot be ignored have also become the factors restricting its development in China, such as high purchase cost, high requirements for road conditions, high driving difficulty, unstable freight market, limited application scenarios, and immature product technology, all of which make car owners flinch.

It is worth mentioning that, at present, the exploration of the central axle trailer in China is still at the initial stage, and the transportation environment is also gradually improving. According to the advantages of the central axle trailer itself, and the gradual formation of the special vehicle, modular and standardized transportation trend, the central axle trailer may occupy a certain market space in the future, and the market coverage of various matching accessories will also further increase.

The Darong concave axle (eccentric bridge) is specially designed for mid-axle trailers. The connection between the axle beam and the wheel end presents an inverted door structure, which can further reduce the vehicle chassis height and center of gravity, ensure the load-bearing capacity, broaden the cargo loading space and improve the driving stability.