Shock absorbers
are important part of vehicle's suspension, that are fabricated to reduce
shock impulse Shock absorber minimizes the effect of traveling on a rough
ground. Modern vehicles are designed with strong shock absorbers to tolerate
any type of bouncy conditions. If supposedly shock absorber is not used then
to control excessive suspension movement, stiffer springs will be required
thereby resulting in harsh ride. But the use of shock absorbers requires the
use of soft springs and hence smooth ride on bouncy conditions.
Types of Shock Absorber
There are different types of shock absorbers which are classified according
to their configuration and usage. Following are some of the important
varieties of shock absorbers:
Mechanism
Shock absorber are attached at the end of the piston rod and works against
hydraulic fluid in the pressure tube. The movement of the suspension up and
down force the hydraulic fluid through minute holes inside the piston.
However only small amount of fluid is forced inside the piston. The
insertion of fluid reduce the speed of the piston which in turn slows down
the piston, which in turn slows down spring and suspension movement.
The speed of the suspension and the number and size of the orifices in the
piston determines the resistance a shock absorber. Nowadays, shock absorbers
are made using this principle. That is faster movement of suspension means
more resistance shock absorber provides. Shock absorber designed on this
basis simply reduces the bounce, Roll or sway and Brake dive and
Acceleration squat.
Historical Evolution
In the early 20th century cars use heavy carriage springs. The use of
carriage springs though did not give smooth ride but nevertheless it was
useful for riding in rugged and bad quality roads. However one of the
company(pioneer vehicles) manufactured the shock absorber with new
designs that provided comfort riding and good driving control. In the
design wheels were allowed to pivot whereas the axle remained
stationary. The oscillating leaf spring was damped by device called a
shock absorber. In modern times lots new shock absorbers have been
designed that provide more stability and smoothness to the ride. |
Shock Absorber Working Principle
There are two cycles in which Shock absorber works:
Compression Cycle
In the compression cycle the piston moves downward and compresses the
hydraulic fluid in the chamber which is situated below the piston. In this
cycle or downward movement, the fluid flows to upper chamber from down
chamber through piston. Some of the fluid also flows into reserve tube
through the compression valve. Flow is controlled by valves in the piston
and in the compression valve.
Extension cycle
In the extension cycle the piston moves upwards toward the top of the
pressure tube. The upward movement results in the compressing of the fluid
in the chamber lying above the piston. The extension cycle generally (
especially in the case of cars and light trucks) provides more resistance
than compression cycle.
General Features Of Shock Absorbers
Some of the general features of the shock absorbers are as follows:
- Shock absorber has seals that keeps the oil in and contaminant out
- The metal used are stronger and harder. Modern shock absorber uses
sintered metal which provides durability and longer life.
- Flat metals are used for constructing most of the cylinders which are
welded at the seam.
- Nowadays lots of shock absorber so manufactured are velocity
sensitive.
Applications
Shock absorbers are engineered for various purposes. They are designed in
various shapes and sizes for meeting the needs of different industries. The
industries in which these shock absorbers are used are:
- Automobile and motorcycle suspensions
- Aircraft landing gear
- In various industrial machines
- In structural engineering to reduce the effect of earthquake and
resonance
Geometry of The Shock Absorber
Geometry of the shock absorber is one of the other major aspect that
needs to be considered while mounting shock absorber.
Leaf Sprung, Front Axle
For mounting front axle leaf spring the shock absorber should be as far
outboard as possible. The shock absorber so placed should have a slight
lean to the rear.
Leaf Spring, Rear Axle
Front axle leaf spring shock absorber should be mounted as far outboard
as possible. The shock absorber so placed should also remain
perpendicular to the travel of the suspension.
Angle of the Dangle
Some shock absorbers are mounted at angles that reduce the overall
dampening effect of the shock. This is because shock absorber will
travel less distance than that of the suspension system.
Other Locations
Some vehicle mount shock absorbers behind the solid axle |
