In this article, you learn what is shock absorbers, types of shock absorbers and how they works.
Shock Absorbers and Types
If the suspension springs are rigid enough, they will not absorb shocks efficiently. If they are flexible enough, they will continue to vibrate for a long time even after the bump has passed.
Therefore, the springing device must be a compromise between flexibility and stiffness. Shock absorbers are provided as part of the suspension system of motor vehicles for this purpose.
When the vehicle wheel strikes a bump, the spring is compressed enough and only a little vertical upward motion is transferred to the frame. When the wheel comes down from the bump, the spring expands very rapidly.
If this rebound is not controlled the spring starts to vibrate heavily to control this vibration, at the shock-absorber, is used in the suspension system. Similarly, when the wheel falls over a hole, the spring expands and is unable to take the full vehicle load. The shock absorber takes part in this load.
In the case of a leaf spring suspension system, the friction between the leaves provides the damping effect. But because of the change in lubrication conditions, the amount of friction also changes, and hence the damping characteristics do not remain constant.
Therefore, additional damping is provided by means of the dampers or shock-absorbers. Frequently, the shock absorber housing is linked to the frame cross member and the shock absorber arm is connected to the spring, axle, or suspension control arm.
Mainly the shock absorbers are of two types Mechanical and Hydraulic
Types of Shock Absorbers
Following are the different types of shock absorbers:
- Hydraulic type shock absorbers
- Double acting shock absorbers
- Single acting shock absorber
- Friction type shock absorber
- Lever type shock absorber
- Telescopic type shock absorber
1. Hydraulic Type Shock Absorber
Hydraulic type shock absorbers are now used on all passenger cars. They increase resistance to the spring action by forcing a fluid through check valves and small holes.
2. Double Acting Shock Absorber
Double-acting shock absorbers offer resistance both during compression and rebound of the springs.
3. Single Acting Shock Absorber
Single acting shock absorber offers resistance only on the rebound.
4. Friction Type Shock Absorber
The friction type shock absorbers have almost become obsolete due to their non-predictable damping characteristics.
5. Lever Type Shock Absorber
The lever-type shock absorber is of indirect-acting type. It is bolted to the chassis through a lever and link. As the axle moves up and down, a double piston arrangement forces the oil through a valve.
6. Telescopic Type Shock Absorber
Telescopic type shock absorber is of direct-acting type. It is mounted between the axle and the frame.
A simplified diagram of the telescopic shock absorber is shown in Figure. Its upper eye is attached to the axle and the lower eye to the chassis frame. A two-way valve A is attached to a rod G. Another two-way valve B is connected to the lower end of cylinder C.
The fluid is in the space above and below the valve A, and also in the annular space between the cylinder C and tube D, which is connected to the space below the valve B. The head J has a gland H. Any fluid scrapped off by the rod G is brought down into the annular space through the inclined passage.
Working of Shock Absorbers
The shock absorber works as follows when the vehicle comes across a bump the lower eye moves up. Therefore, the fluid passes from the lower side of valve A to its upper side. But since the volume of the space above valve A is less than the volume of the rod G, the fluid exerts pressure on the valve B.
This pressure of the fluid through the valve openings gives the damping force. Thus, when the lower eye E moves down, the fluid passes from the upper side of the valve A to the lower side, and also from the lower side of the valve B to its upper side.
The shock absorber must be filled with shock absorber fluid at regular intervals as recommended by the manufacturer or when required by its condition. The modern telescopic shock absorbers are no longer serviced. If they leak or do not offer proper resistance to push and pull they should be replaced.
Testing of a Shock Absorbers
The shock absorbers should be tested by moving the front or rear of the vehicle up and down quickly. If the vehicle does not come to rest almost immediately, the shock absorbers must be removed for further testing. Often noise results from loose shock absorber arm-to-frame connections. These joints should always be kept tight.
In the case of damages to shock absorbers, the operation may become irregular and result in noisiness and vibration in dampening the effect. The noise may originate from other sources. Therefore, before replacing shock absorbers, inspect carefully the entire suspension system and the mountings of shock absorber on body and axle.
Check that shock absorber mounting eyes firmly locked on rubber bushes and that these are not worn. Replace worn or damaged parts. Other possible causes of noisiness are a distortion of pipes or due to bumps against obstacles, to stones thrown up by wheels.
The vibrations in the damping effect may occur either as an increase or reduction in damping ability. Generally, the first case is rare and originates either from thickening of fluid or from the closer matching of valves and setting, with a resultant increase in shock absorber resistance. The second case may be the result of breakage of some inner part, shortage of fluid or stuck valves.
So now, we hope that we have clear all your doubts about Shock Absorber. If you have still any doubts about “Types of Shock Absorber” you can contact us or ask in the comments.
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