Shock absorbers are an important class of components in your car. They protect the vehicle and the passengers from the unwanted jerks or jolts, vibrations because of bumps and wholes on the road. They make the movement of the vehicle smooth and make the ride comfortable for the passengers. There are different kinds of shock absorbers available and each of them has a distinct function according to the need of the vehicle. We discuss briefly a few of them.
The basic twin tube
The twin tube contains two nested cylindrical tubes – the working tube and the reservoir. Both the tubes contain hydraulic fluid. A piston is inserted into the inner tube and the piston cap has tiny orifices for the hydraulic fluid to get displaced when the piston moves back and forth. Thus, the shock energy converted into heat and gets removed. Twin tube shock absorbers can be as follows:
Gas charged twin-tube
In this, nitrogen gas is used in the reservoir instead of the hydraulic fluid. This is a major improvement over the basic twin tube as it gets rid of problems like aeration and foaming and also hydraulic fluid dripping out of the pipe caused by the action of the piston. Due to this prevention, overheating is reduced largely.
Position sensitive damping
The position sensitive damping system contains two extra grooves, so that the piston moves freely on the tube, if the vehicle is running on a smooth surface. At the same time, it also restricts the movements when the vehicle moves in a bumpy surface, where the upward and downward movement of the piston occurs with more intensity. This new advancement in the dampening system enables car designers to manufacture shock absorbers according to the size, weight, maneuverability, etc. of the car.
Acceleration sensitive damping
Acceleration sensitive damping can change the difference between smooth and bumpy riding. It can also react to bumps individually. Acceleration sensitive damping is achieved by making some changes in the compression valve. The important thing to note here is that, this damping mechanism just does not improve on the regular ‘control versus comfort’ trade off, but eliminates it. It also highly reduces the pitch of the vehicle while braking and roll during turning.
Unlike the bi-tube damper, the mono-tube shock absorber has no reservoir tube. There has to be an amount of displacement of the hydraulic fluid when the piston is pushed in. This is managed by making the fluid adaptable to pressures. This is achieved by filling the lower part of the tube with nitrogen gas. The hydraulic fluid and nitrogen gas are separated by a ‘floating piston’.
When the piston is pushed downward, pressure rises in the hydraulic fluid and nitrogen. However, as an act of displacement, the floating piston moves downward compressing the nitrogen gas.
Likewise, when the piston is pulled out, the hydraulic fluid flows with the piston and the floating piston is also lifted upwards. The resistance created this way offers outbound damping of the suspension.