The difference between the front and rear heights of the semi-trailer after the tractor is engaged with the semi-trailer
When the user determines the tractor model, the designer should determine the height of the load-bearing surface of the semi-trailer according to the height of the plane above the tractor saddle at full load. The height of the load-bearing surface of the semi-trailer is mainly from the front and rear height of the longitudinal beam and the total suspension. The height of the tire and the type of the tire are determined. Generally, the front and rear heights of the longitudinal beam of the semi-trailer are determined when designing the frame, and the tire model is related to the selected axle and axle load, so the suspension assembly can be adjusted during design. The height of each steel plate bracket is used to adjust the height of the bearing surface of the semi-trailer.
However, in the design process, due to the large number of new tractor models, the announcement parameters provided by the tractor manufacturers do not have the height of the plane on the upper side of the tractor saddle, and the owner cannot provide this parameter. Therefore, when the semi-trailer manufacturer is designing, Only some experience can be used to estimate the height of the plane above the saddle of the tractor. Therefore, after the tractor is engaged with the semi-trailer, it is prone to the abnormal phenomenon of low front and high height or the situation of high front and low back limit. The difference in the size of the front and rear height difference of the semi-trailer is also different. It is completely designed by personal experience. This will cause the axle load of each axle of the semi-trailer to be uneven when transporting cargo, and the brakes of each axle are not synchronized during braking. The shaft axle is braked and locked in advance, causing the tire tread to wear or wear rapidly. This is especially true when the semi-trailer is driving at high speed under no-load conditions.
In view of the above situation, the design requires that after the tractor and the semi-trailer are engaged, when the horizontal section is in a straight line, the semi-trailer should be high and low, and the difference between the front and rear heights (see Figure 6) should be based on the front and rear panels of the main vehicle. The stiffness of the spring and the stiffness of the leaf spring of the semi-trailer are determined. Considering the factors such as the forward thrust and the forward shift of the center of gravity during full-load braking, it should be ensured that the semi-trailer is 10mm-40mm higher than the rear at full load.
