13 - meter semi - trailer wheelbase allowable error
If there are specific requirements, the wheelbase and wheelbase dimensions of the trailer directly affect the external dimensions, total mass, passability, driving stability and additional performance of the vehicle.
With the increase of wheelbase, the driving stability of the car is improved, but if the wheelbase is excessively extended, the minimum turning diameter of the car is increased, the mobility is reduced, and the stress of the frame becomes worse. The wheelbase is short, the total length of the semi is short, the minimum turning diameter and the longitudinal passing radius are also tiny. However, the wheelchair base is overly short, the driving stability of the trailer becomes poor, and the mass transfer is large when climbing or braking.
Therefore, various factors should be considered comprehensively when determining the wheelbase. In the design, not only the reasonable distribution of load mass of front and rear axles, the uniform force of the frame and the overall layout of the vehicle should be considered, but also the minimum turning radius of the car to ensure that the car can do stable steering, in the initial stage of steering, so that the semi-trailer rear wheel and front wheel trace of the relative offset to achieve the minimum. The wheelbase of a semi-trailer is the distance between the traction pin and the center of the rear axle. Based on previous design experience and some semi-trailer technology and Semi Trailer price parameter data at home and abroad, it is largely reasonable to take the ratio of frame length and wheelbase of the semi-trailer as 1.3-1.6.
The larger the wheelbase, the better the lateral stability, the larger the angular stiffness of the suspension, but if the wheelbase is overly large, the mobility becomes worse, therefore the width of the wheelbase should be determined according to the use requirements. In general, the semi-trailer wheel spacing is the same as the tractor wheel spacing to reduce the rolling resistance of the car on the soft road. The wheelbase of semi-trailer used at home and abroad is mostly 7000-10000mm, the wheelbase is commonly unified as 1820mm, and a modest amount of 2240mm is used.
2, the determination and selection of the front and rear overhang
The determination of the front suspension and rear suspension must ensure the reasonable distribution of the load of each axle of the trailer under uniform load. At the same time, the front and rear overhang also affects the driving stability and passability of the car. Select the principle of front and rear suspension, general hope in uniform load, rear axle load slightly greater than the front axle load (mainly consider braking, the front axle will not be overloaded due to mass transfer, and make the front axle steering light). Semi trailer before and after the suspension of the determination, but also directly affected by the traction pin to the center of the semi axle distance, according to the traction seat at the load and load of the rear axle reasonable distribution of the size of the suspension.
Normally the load distribution between the two places is 3:7 or 4:6. When determining the front suspension (the distance between the traction pin and the front part of the semi-trailer), it should ensure that the front part of the semi-trailer does not interfere with the rear wall of the rear cab of the spare tire frame in the process of vehicle steering, and maintain the 150-250mm spacing between the rear wall and the rear wall; in addition, when the car runs on the ramp, ensure that the front depression angle of the semi-trailer is greater than the slope Angle of the pier approach (typically 5.1-5.7). The rear suspension value of semi-trailer is typically 1500-2500 depending on the size of 4*2 or 6*4 tractors.
3. Determination and selection of axle load distribution
After the loading weight of the semi-trailer is known and the initial estimation of the assembly mass of each part of the semi-trailer, the axle load mass of the semi-trailer can be calculated. The mass distribution of axle load of semi-trailer can be obtained by assuming that the mass of each component and the loading mass of the semi-trailer on the frame are uniformly distributed loads to take the distance between the traction seat support points and the rear axle support points.
When the weight of the axle load is calculated, first of all, it is necessary to check whether the load at the traction pin meets the allowable load at the saddle of the tractor, and then it is necessary to check whether the load of the rear axle is overloaded. If one of the two cannot meet the requirements, the wheelbase should be adjusted until the requirements are met.