The second chapter of special automobile design basic knowledge

Special vehicle design basic knowledge

Chapter II General Arrangement of Special Purpose Vehicles

First, the principle of general arrangement

The task of the overall arrangement of special purpose vehicles is to correctly select the parameters of the entire vehicle and rationally arrange the working devices and accessories. The power-retrieving device, dedicated working device, other accessories and the selected chassis of the vehicle constitute an overall coordination and matching, and meet the requirements of the basic performance and special performance of the entire vehicle proposed in the design task book. In the overall arrangement, the following principles should be followed:

(1) Try to avoid changes to the position of the chassis assembly

  Because of the change in the position of some assembly components, it will not only increase the cost but also affect the performance of the entire vehicle. But sometimes in order to meet the performance requirements of the special working device, some changes need to be made, such as shortening the rear suspension of the original car chassis, the position of the fuel tank and the spare tire frame for proper adjustment. However, the principle of change does not affect the overall vehicle performance.

( 2 ) The requirements of the performance of the special working device shall be met so that the special function can be fully utilized.

  For example, the special function of gas unloading bulk cement tank vehicles is to use compressed air to fluidize the cement and transport the cement through pipelines to a cement warehouse with a certain height and horizontal distance. The main performance index of gas unloading cement is the residual cement ratio or remaining ash ratio. To reduce this index, the tank can be arranged at an angle with the horizontal line, as shown in the figure.

However, this arrangement will increase the center of mass of the vehicle and reduce the roll stability angle, so it can also be arranged horizontally, as shown in the figure. When carrying out the overall arrangement, comprehensive considerations must be taken from various aspects.

(3) Estimation and calibration of parameters such as loading quality and axle load mass distribution

In order to adapt to the load capacity and vehicle performance requirements of the vehicle chassis or assembly, some of the parameters to be dealt with after the initial completion of the general arrangement are the most important ones related to the determination of the loading quality and the allocation of the axle load quality for evaluation and verification. The parameters have a great influence on the overall vehicle performance. If it does not meet the requirements. The overall layout plan should be modified.

(4) The arrangement of the working device should be avoided to cause a concentrated load on the frame

For example, in the layout of the concrete mixer truck shown below , the arrangement of (a) forms a significant concentrated load, while in the arrangement of (b) , due to the use of a subframe with sufficient rigidity, Concentrating the load into a uniform load will help improve the strength and life of the main frame longitudinal beams.

(5) The total vehicle conditioning quality of dedicated vehicles should be reduced as much as possible, and the loading quality should be improved.

(6) Should meet the requirements of relevant laws and regulations

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