What is Shock Absorber | Function , Types of Shock Absorber 

Shock Absorber

Shock absorbers will not efficiently absorb road shocks if the suspension springs are highly rigid. They will be continuously vibrated for a longer time if springs are sufficiently flexible. To overcome this difficulty, a system having compromise between flexibility and stiffness should be used. Shock absorbers are used as a part of the suspension system. They provide more resistance to the motion of the spring and road wheel in order to damp out vibrations.

Read More : Telescopic Shock Absorber | Working, Diagram and Advantages

Purpose /Function of shock absorber:

(i) To control the vibrations on springs.
(ii) To provide comfortable ride.
(iii) To act flexible and to be rigid enough.
(iv) To resist the unnecessary motion of the spring.

Types of shock absorbers:

1. Mechanical shock absorber (friction type)
2. Hydraulic shock absorber.

Again the hydraulic shock absorbers are further divided into various types.
1. Van type
2. Piston type
a. Single acting
b. Double acting
3. Telescopic type.

shock absorber
shock absorber

Twin-Tube or Dual Tube Shock Absorber

It is the type of shock absorber in which 2 hollow tubes named primary tube and secondary tube or shell are used which are merged together in telescope type fashion i.e. primary tube inside secondary tube or shell.

  • The primary tube contains the moving piston, compression valve along with other assembly components and is filled with high viscosity index oil.
  • The secondary tube or shell contains the primary tube along with low pressure gas (mostly nitrogen gas).
  • This whole assembly of twin tube is surrounded by a coil spring that provides the stiffness and also helps this assembly to regain its initial position after actuation.

Mono-Tube Shock Absorber

It is the type of shock absorber in which instead of double tube, a single tube is used inside which the moving piston is placed.

  • High viscosity index oil along with the low pressure gas (nitrogen in most cases) is filled inside a single tube in a particular proportion.
  • The oil and gas filled inside this single tube is separated by a floating piston which is placed airtight inside the tube.
  • This whole assembly is surrounded by a coil spring same as twin tube shock absorber

Gas-filled mono-tube shocks

To prevent foaming and bubbles in the oil, which degrades shock-absorber performance, a gas-filled mono-tube shock has a chamber of high-pressure nitrogen above the oil chamber. This high-pressure gas makes it difficult for bubbles to form in the oil, even when the shock absorber moves in and out very quickly, as it might while traveling rapidly on a very rough or washboard road.

Gas-filled shocks are expensive, since they require strict manufacturing tolerances, but they are very resistant to fade and consequently are popular in off-road racing and rallying. Gas-filled shocks, by the way, are not the same as “air shocks,” which use an air chamber separate from the shock oil. An air shock is actually an air spring that raises or lowers the vehicle when air is added or removed through a valve.

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