Modification of Automobile Spring
Coil spring is the most commonly used spring in suspension system because it is easy to make, high performance and low price. The physical definition of a spring is to store energy. When we apply a fixed force to the spring, it will deform. When we remove the force, the spring will tend to return to its original state. However, when the spring rebounds, the amplitude of the shock will often exceed its original length. Until there is friction resistance, the free vibration caused by spring rebound will be slowed down, which will slow down the free vibration of spring Tang’s work is usually the task of the shock absorbers.
The general spring is the so-called “linear spring”, that is, when the spring is under force, its compression deformation follows the “Hooke’s law” in Physics: F = KX, where f is the applied force, K is the elastic coefficient, and X is the deformation amount. For example, when a linear spring is subjected to a force of 40kg, it will cause 1cm compression. After that, every 1cm increase of 40kg force will increase the amount of compression. In fact, there is other pressure on the suspension spring, which is still under pressure even when the spring is fully extended, so that the spring itself can be fixed in the car.
In the traditional spring and shock absorber suspension design, the spring plays the role of supporting the vehicle body and absorbing the impact of uneven road surface and other forces on the tire. Here, the so-called other forces include the forces caused by acceleration, deceleration, braking, turning, etc. More importantly, in the process of eliminating the vibration, it is necessary to maintain the continuous contact between the tire and the road surface and maintain the tracking performance of the car. Improving the contact between the tyre and the road surface is our primary consideration for improving handling.
The most important function of the spring is to maintain the comfort of the car and keep the tire in full contact with the ground.
Using the wrong spring will have a negative impact on the driving quality and handling. If the spring is completely rigid, then the suspension system will not work. When the car jumps up on uneven road surface, the tire will leave the ground completely. If this happens during acceleration, braking or turning, the car will lose tracking. If the spring is very soft, it is easy to “sit on the bottom”, that is, the suspension travel will be exhausted. If the situation of sitting on the bottom occurs when bending, it can be regarded as that the elastic coefficient of the spring becomes infinite (there is no compressed space), and the body will produce an immediate weight transfer, resulting in the loss of tracking. If the car has a long suspension travel, it may be possible to avoid “sitting on the bottom”.
However, the relative body height will also become very high. A high body means a high body center of gravity. The height of the center of gravity of the body has a decisive impact on the handling performance. Therefore, too soft shock absorbers will cause obstacles in handling. If the road surface is absolutely flat, then we don’t need springs and suspension systems. If the road surface is rough, a soft spring is required to ensure that the tire is in contact with the road surface, and the spring travel must be increased. The selection of spring hardness is determined by the roughness of the road surface.
The more rugged the spring is, the softer the spring is. However, how soft the spring is is is a key issue. Usually, this requires experience accumulation, which is also an important topic for vehicle manufacturers and teams.
Generally speaking, soft springs provide better comfort and better tracking performance over rough roads. However, when passing through the general road, it will cause the suspension system to swing up and down greatly, which will affect the handling. In a car equipped with good aerodynamic components, the soft spring will change the vehicle height when the speed is increased, resulting in different handling characteristics at low speed and high speed.
For the front suspension system of small cut, the coil spring is divided into 9 coils and 10 coils. The former is dedicated to 4 cylinders and the latter is dedicated to 6 cylinders. In the case of not increasing the front counterweight, the general refitting does not need to be replaced, and a group of rubber pads can be added. However, after replacing the front bar and installing the winch, it is necessary to change more coil springs to ensure the vehicle handling and the life of the relevant mechanical parts.