The shock absorber is provided provide the damping of the
spring to prevent excessive flexing. In the leaf spring the friction between
the leaves provide the damping effect but sometimes it is not sufficient so we
used shock absorbers. In case of helical springs the whole damping effect is
provided by the shock absorber. The shock absorber controls the excessive
spring vibration and prevents the spring to vibrate even after bump.
The shock absorber absorbs the energy of the shock and
converted into vertical movement of axle by providing damping and dissipating
the same into heat.
There are basically two types of shock absorber
Friction types:
In these types of shock absorber whole damping effect is
provided by the friction force between two moving parts. These types of shock
absorber almost become obsolete due to it not-predictable damping characteristics.
Hydraulic types:
In this type of shock absorber hydraulic fuel is used to
resist the motion of the spring. It is work on basic principle of Pascal law
that when a piston force the fluid in a cylinder to pass through some hole, a
high resistance to the movement of piston is developed, which provides the
damping effect. The main advantage of this type of shock absorber is that the
damping is proportional to the square of the speed. So for small vibrations the
damping is also small, while for larger ones the damping becomes automatically
more.
Shock absorber ratio:
It is the ratio of the shock absorber resistance to upward
movement and to downward movement. It describe the percentage of the shock
absorber’s total resistance is in compression and what percentage in extension.
Most shock absorbers are designed for 50/50 ratio only. This ratio does not
notify the capacity of shock absorber. The actual damping rates are controlled by
the piston and orifices size.