Suspension System: Spring, Shock, and Other Components

The basic principle of a suspension system is to restrict the vibrations from being transmitted to the various components of vehicle, to protect the person sitting inside the vehicle against road shocks, and to maintain stability of the vehicle in pitching or rolling when in motion.

The chassis of an automobile is assembled on the axles, with the help of springs. Obviously this is done to isolate the different parts of the machine against shocks. These shocks cause the vehicle to bounce, pitch, roll, or sway.

No one wants to have a ride which gives a roller coaster feeling. Everyone wants the ride to be smooth and comfortable, and this is what the suspension does for us.

Let's first see the factors for which a suspension system needs to be designed.

This turns the vehicle about its longitudinal axis. This phenomenon is called rolling. The amount the vehicle lifts determines the axis about which the vehicle will roll.

Different movements are caused due to sudden acceleration and applying of brakes, which are taken care of by the suspension system. On applying brakes to a moving automobile the vehicle tends to lower or dip. This relates to weight transfer, and one of the major factors that cause this is related to suspension characteristics.

Also, when in motion, the front of the vehicle will lift. The forces created by sudden braking and acceleration are absorbed by deflecting springs, wishbone arms, or by radius rods (parts of the suspension system).

While in motion, there are many forces which come into existence, like wind, cambering of road, etc. While turning, centrifugal forces create a force called side thrust. All these forces are generally absorbed by leaf springs or by fitting panhard rods.

The spring thus needs to be made of materials which provide it the strength to resist stress. The frequency of the front springing must be less than the rear one.

Unsprung weight means that parts of vehicle body which are not supported by springs. The weight of automobile components between the suspension and road surface is known as unsprung weight. These include the wheels, tires, brakes, steering knuckle, and the front axle and rear axle assembly.

The weight carried by the spring includes the frame body, engine, and the transmission system. The collective weight of these parts is called sprung weight.

Let's see what role unsprung weight plays in causing stress on springs. When the wheels come across a bump, the vibrations are also shared by other unsprung parts, which store the vibration energy and further transfer it to sprung parts. The weight of unsprung parts has direct proportion to the amount of shocks the body has to bear.

The springs are located between the wheels and the vehicle body. After the wheel hits a bump or pit, the spring deflects and is stretched outwards. 

It is then pulled back due to elasticity, thereby extracting the energy created due to bumps. The amplitude of spring deflection decreases gradually due to its internal friction and friction of suspension joints until spring comes to rest. The different types of suspension springs are listed here:

The suspension system is given great importance while designing the different parts of a vehicle. The nature of the material, its weight, and many other factors are considered depending upon the suspension system. The vehicle is said to be equipped with new techniques only if it satisfies the new demand for improved suspension systems.