Why is the leaf spring of off-road vehicle opposite to the transport vehicle?

As we know, the elastic elements of independent suspension of passenger cars mostly use spiral springs, and the elastic elements of non-independent suspension mostly use leaf springs. Because the steel structure is simple and reliable, leaf springs are widely used, such as some off-road vehicles, pickup trucks or vans. While buses and trucks mostly use leaf springs. As the name implies, leaf spring is made of steel plate, also called leaf spring. In order to make full use of materials, leaf springs are made in the form of stress beams. There are two kinds, one is equal thickness, narrow at both ends and wide in the middle. This type of leaf spring is a traditional multi-leaf laminated leaf spring, which is composed of many pieces of steel with different lengths and the same width. Now, most buses and trucks use this kind of leaf spring.

The other is equal width, thin at both ends and thick in the middle. This is a common leaf spring. A small number of leaf springs refers to a variable cross-section leaf spring with only 1 ~ 4 leaves, and a variable cross-section leaf spring refers to a leaf spring with a thicker center along the length direction of the leaves, which gradually becomes thinner at both ends, or the width and thickness of the leaves gradually change. It is mostly used in light vehicles, and now some large and medium-sized buses tend to use this kind of leaf spring. The middle part of the leaf spring is fixed on the axle with U-bolts (also called riding bolts), and the lifting lugs at both ends are hinged on the bracket of the frame with pins. In this way, the axle is connected with the car body through the leaf spring, which plays the roles of buffering, vibration reduction and force transmission. The steel plates of multiple leaf springs are superimposed in an inverted triangle, with the top steel plate being the longest and the bottom steel plate being the shortest. The number of steel plates is related to the weight of the supporting vehicle and the shock absorption effect. The more steel plates, the shorter the thickness and the greater the stiffness of the spring. However, when the leaf spring is bent, the parts will slide and rub against each other to produce noise. Friction can also cause spring deformation, leading to uneven driving. Therefore, a few leaf springs appear in cars with low load capacity to eliminate the defects of many leaf springs. Some few leaf springs use only one leaf spring. Compared with many leaf springs, it not only reduces noise and friction, but also saves materials, reduces weight, is convenient to arrange, reduces the height of the whole vehicle and has good riding comfort. The cross section of steel plate with few leaf springs changes greatly, and the cross section is gradually different from the middle to the two ends, which makes the rolling process more complicated. In order to reduce the weight and the difficulty of rolling process, a fiber reinforced plastic (FRP) has appeared in recent years to replace steel plate, which can reduce the weight by more than half. This kind of fiber reinforced plastic is made of glass fiber and polyester resin. According to the calculation, a single leaf spring generally weighs about 1 1 ~ 20kg, while the glass fiber reinforced plastic spring weighs about 4kg, which is stable in operation and low in noise.