The function of the driving system of a special vehicle is to accept the torque output by the engine through the transmission system and generate the traction force of the road surface on the special vehicle through the adhesion between the driving wheels and the road surface to ensure the normal operation of the special vehicle. Transmit and bear the counter-forces in all directions exerted by the road surface on the wheels and the moments formed by them; In addition, the driving system strives to mitigate the impact and vibration caused by uneven road surfaces on the vehicle body, ensuring the smoothness of the special vehicle's driving. Moreover, it works in coordination with the special vehicle's steering system to achieve correct control of the vehicle's driving direction.
The driving system of a special-purpose vehicle mainly consists of the frame, axle, wheels and suspension. The engine power is transmitted to the rear wheels through a long drive shaft to achieve rear-wheel drive. This layout is conducive to improving the stability of the special vehicle during high-speed driving.
Frame
The vast majority of modern special-purpose vehicles are equipped with frames that serve as the overall framework of the vehicle, which are used to support and connect the vehicle's components and bear various loads from both inside and outside the vehicle. Nowadays, many sports cars adopt truss-type frames welded with steel pipes. This three-dimensional structure frame serves the functions of both the frame and the body. Some sedans and large buses have also removed the frame and replaced the function of the frame with the body.
Axle
The main function is to transfer the forces in all directions between the frame and the wheels. Currently, almost all coupes and sports cars are split axles, which are used in conjunction with independent suspensions (generally, heavy locomotives use integral axles). Axles also include steering axles, steering drive axles and support axles. Generally speaking, the front axles of all-wheel drive front-engine sports cars are all steering drive axles, which are responsible for both steering and driving. During the operation of a special-purpose vehicle, when the driver turns the steering wheel, it controls the steering joint through the corresponding transmission device to make the wheels swing left and right. The automatic recentering characteristic of the wheels during the operation of special vehicles is achieved through several positioning parameters such as the rearward tilt Angle of the main pin, the inward-tilt Angle of the main pin, the camber Angle of the front wheels, and the forward toe-in of the front wheels. Due to the complex physical properties involved, they are not introduced here for the time being.
Wheel
A wheel is mainly composed of a hub and a tire. Among the performance indicators of today's high-speed sports cars, tires are of vital importance as they reflect the grip characteristics of the sports car during high-speed driving. During the normal use of special-purpose vehicles, tires with strong grip should be selected based on safety principles. However, in rally races or GT touring car races that require high-speed drifting and cornering, tires with slightly weaker grip should be chosen to achieve fishtailing and cornering. For instance, the Michelin Slick tires used in the Dongfeng Xiaojinba fuel truck have almost no grip before being preheated.
Suspension
The main component of the suspension system is the shock absorber, which is mainly hydraulically controlled. The stability and comfort of special-purpose vehicle operation mainly depend on this component. The suspension and shock absorbers of supercars are all subject to absolutely precise testing and setting. They can also effectively lower the vehicle height to enhance the aerodynamic performance of the vehicle. Therefore, the tuning of the suspension system is extremely complex. In addition, some high-end recreational vehicles also adopt pneumatic control suspension systems, which mainly control the dynamic changes of gas according to the height of the vehicle body by a computer, thereby enhancing the comfort of the driver and passengers inside the vehicle.
