The suspension System of an automobile is one which separates the wheel/axle assembly from the body. The primary function of the suspension system is to isolate the vehicle structure from shocks & vibration due to irregularities of the road surface.

1. ER. PEEYUSH CHAUHAN
ASSISTANT PROFESSOR
DEPARTMENT OF MECHANICAL ENGINEERING
Email Id- peeyushchauhan1989@gmail.com

2. “The suspension System of an automobile is one which separates
the wheel/axle assembly from the body. The primary function of
the suspension system is to isolate the vehicle structure from shocks
& vibration due to irregularities of the road surface.”
The suspension system consists of a spring & damper
(including also spring, shackles, axles, wheels & stabilizer).

3. 1903- Mors from Germany fitted a car with shock absorbers.
1920 -Leyland used torsion bars in its suspension system.
1922-Unitary construction and independent front suspension were
pioneered on the Lancia Lambda.
1932-By this year ,the independent front suspension become more
common in popular cars.
1948-Triumph Mayflower introduced the combined coil
spring/damper unit.
1950-Ford adopted the McPherson strut independent front
suspension on MK 1 consul.
1959 -Use of independent rubber suspension.
1962 -Introduction of hydrostatic suspension.

4. 1. Spring-It absorbs road shocks or impacts due to bump in
road by oscillating. Tyres also provides spring effect , but to
a smaller extent.
2. Damper- They reduce the tendency of the carriage unit
to continue to “bounce” up and down on its springs.
Oscillation due to road shocks are restricted to a reasonable
level by damper.

5. 1. Spring
Springs are resilient members and as such act as reservoirs of
energy . They store the energy due to the sudden force which comes
when vehicle encounters a bump or a ditch .
This energy is released subsequently and with the action of
damper, the energy is converted into heat and bounce is
avoided. Springs used for suspension system should absorb
road shocks quickly and return to the original position
slowly.
The various types of automotive spring are-
1. Leaf or laminated Springs
(a) Full elliptic- Two semi elliptic springs connected to form
the shape of ellipse.

6. (b) Three Quarter elliptic- One semi elliptic spring
connected over a quarter elliptic spring.
(c) Semi-elliptic- Forming the shape of half elliptic.
(d) Quarter elliptic- Half of semi elliptic spring.
2. Coil Spring
3. Torsion Bar
4. Air & gas spring
5. Rubber Spring
2. Damper or Shock Absorber -Shock absorber, or
snubber, a device that controls unwanted spring motion through
a process known as dampening. Shock absorbers slow down and
reduce the magnitude of vibratory motions by turning the
kinetic energy of suspension movement into heat energy
that can be dissipated through hydraulic fluid.

7. A shock absorber is basically an oil pump placed between the
frame of the car and the wheels. The upper mount of the shock
connects to the frame (i.e., the sprung weight), while the
lower mount connects to the axle, near the wheel (i.e., the
unsprung weight).
Shock absorbers work in two cycles — the compression
cycle and the extension cycle. The compression cycle occurs as
the piston moves downward, compressing the hydraulic fluid
in the chamber below the piston. The extension cycle occurs
as the piston moves toward the top of the pressure tube,
compressing the fluid in the chamber above the piston.

8. Modern car mostly have following types of shock absorber:
1. Telescoping dampers
2. Rocking lever damper
1. Telescoping dampers:-
In this type f shock absorber the cylinder is filled with the
fluid prescribed by the manufacturer. There are valve
opening in the piston. The valve are opening are also at the
bottoms of the cylinder tubes. There are reservoir tube full
of fluids.
When the wheels meet bumps & pot holes of the shock
absorber lengthen & shortens. When this happens a piston
inside the cylinders of shock absorber moves up & down.

10. When the shock absorber is compressed , the fluids in the
cylinder passes upwards through the restricted valves of the
piston. At the same time the fluids passes down through a
small valves of the cylinder tube. By this arrangements the
piston is able to move against the resistance of the fluid.
Thus the shocks on the vehicle absorbs by fluids.
When the shock absorber is lengthen, the fluid from the top
position of the piston is forced downwards through the
piston valves. At the same time the fluid from the reservoir
tube enters through a valves at the bottom of the cylinder
tube. By this arrangements the process of the shock
absorbers being lengthened is made very slow. This takes
place after overcoming the resistance of fluid.

11. 2. Rocking lever damper:- Its working principle same as
telescopic damper but has two pistons which moves in the
cylinder while the oil is displaced through a valve.
The motion of the dual pistons take place due to the motion
of the wheels which is passed on the piston through the
rocker levers.

15. The front end suspension is more complicated than the rear
end suspension because the front wheels not only move up
and down with respect to the car frame but also swing at
various angles to the car frame for steering.
The Front End Suspensions may be of two types
1. Rigid axle front suspension.
2. Independent front suspension
1. Rigid Axle Front Suspension
This type of suspension was universally used before the
introduction of independent front wheel suspension. It may
use either two longitudinal leaf spring, or on transverse
spring, usually in conjunction with shock absorbers. These
assemblies are mounted similar to rear leaf spring
suspensions.

16. 2. Independent Front Suspension
In this type of suspension, each front wheel is independently
supported by a coil, torsion bar, or leaf spring. Most of the
passenger cars now use the independent front suspension in
which the coil spring system is the most common.
Types of Independent Front Suspension
1. Twin I-Beam Suspension System
2. Single I-Beam Front Suspension System
3. Independent Front End Suspension Using Torsion Bar
4. Parallelogram Type Independent Front Suspension
5. Struck and Link Type Suspension System
6. Trailing Arm Independent Front Suspension

17. 7. Sliding Pillar Types Suspension System
8. Vertical Guide Suspension System
9. Wishbone arm type Suspension system
1. Twin I-Beam Suspension System
The twin I-beam construction is another type, used on some
models of Ford trucks. Each front wheel is supported at the
end by a separate I beam. The ends of the I-beams are
attached to the frame by pivots.
The wheel ends of the two I-beams are attached to the
frame by radius arms, which prevent backward or forward
movement of the wheels. This type of suspension provides
more flexibility.

19. 2. Single I-Beam Front Suspension System
Single I-beam front suspension is employed in larger
vehicles. The I-beam has a hole in each end through which a
kingpin is assembled to hold the steering knuckle in place.
Each end of the I-beam is supported by a leaf spring.
3. Independent Front End Suspension Using Torsion Bar
This type of suspension system, a steel rod, known as a
torsion bar, act as a spring to hold the upper and lower
control arms parallel under load. The front end of the rod is
of hexagonal shape to fit tightly into an opening in the
lower control arm. When the wheels move up or down, the
torsion bar get slightly twisted. In this position it absorbs
vibrations.

21. 2. Parallelogram Type Independent Front Suspension
The figure shows the simplified diagrams of the
independent front suspensions using a coil, torsion bar and
leaf spring. Basically, the system is known as parallelogram
type independent front suspension. It consists of an upper
and lower link connected by stub axle carrier.
In general, the lower link is larger than the upper and they
may not be parallel. This arrangement maintains the track
width as the wheels rise and fall and so minimize tyre wear
caused by the wheel scrubbing sideways.

22. 5. Struck and Link Type Suspension System
This type of suspension system is unusually for integral
body construction because the loading points are widely
spaced. The normal top link is replaced by a flexible,
mounting and the telescopic damper acts as the kingpin.
This suspension system known as the Mac-Pherson System
has slight rolling action and absorbs shocks easily.
6. Trailing Arm Independent Front Suspension
Trailing arm independent front suspension maintains
constant track and wheel attitude with a slight change in
wheelbase and caster angle. A coil spring is attached to the
trailing arm which itself is attached to the shaft carrying
the wheel hub. When the wheel moves up and down, it
winds and unwinds the spring. A torsion bar has also been
used in certain designs in place of the coil springs.

25. 7. Sliding Types Suspension System
In this type suspension system, the stub axle can move up
and down as well as rotate in the frame members. Track,
wheel attitude and wheelbase remain unchanged throughout
the rise and fail of the wheel.
8. Vertical Guide Suspension System
In the vertical guide suspension system, the kingpin is
attached directly to the cross member of the frame. It can
slide up and down, thus compressing and expanding springs.

27. Coil Spring Front Suspension
There are 3 types of coil spring front suspension.
1. In the first type, the coil spring is located between the
upper and lower control arms. The lower control arm has
one point of attachment to the car frame.

28. 2. In the second type, the coil spring is located between the
upper and lower control arms. The lower control arms have
two points to the attachment to the car frame.

29. 3. In the third type, the coil spring is between the upper
control arm and spring tower or housing that is part of
front end sheet metal work.

31. Following are three types of rear end suspensions generally
found in vehicles.
1.Longitudinal leaf spring rear end suspension or
Transverse leaf spring rear end suspension
2. Coil spring rear end suspension
1. Longitudinal and Transverse Leaf Spring Rear End
Suspension
Longitudinal leaf spring and coil spring rear end
suspensions are widely used in modern vehicles. Transverse
leaf spring rear end suspension is used in conjunction with
the Hotchkiss drive, the leaf springs must be made strong and
resilient enough to transmit the driving thrust and torque to
resist sideways, in addition, to hold the spring weight of the
body.

33. The spring is clamped the rear-axle housing by U-bolts, its
each end is pivoted to the frame, by means of eyes formed in
the ends of the longest leaf.
One end of the longer leaf is secured to the front hanger by
a bolt and the other end to the rear hanger by spring
shackles. Both the hangers are bolted to the frame.
At the middle position of the spring length, the rebound
clips are placed. They are loose enough to permit the leaves
to slide on the other, and yet tight enough to permit the
leaves together when the spring rebounds. The spring eyes
are usually provided with bushings or some anti-friction
material, such as bronze or rubber.

34. 2. Coil Spring Rear End Suspension
The figure shows coil spring rear end suspension. This type
of suspension is always used in conjunction with torque
tube, torque reaction link, or torque rod drive. Therefore the
coil springs are not subjected to driving thrust or twist.
Stabilizers and radius rods are also used which relieve the
coil springs of all stresses except those acting in a vertical
direction. The stabilizer prevents excessive roll or sideways
when the car is concerning.
The radius rod keeps the rear axle and frame in lateral
alignment. The coil springs are seated in pan-shaped
brackets spring seats attached to the rear axle.

37. 1. Air Suspension System:-
A suspension system whereby air is used as the working
fluid and also the shock absorber, is known as an air
suspension system.
The electronics air compression system consist the
following components:-
1. Electric Air Compressor
2. A Microcomputer Control Module (MCM)
3. Four Air Spring with build-in solenoid valves.
4. Three Height Sensors (Two Front & One Rear)
5. The Air distribution System

38. The height sensor monitor the riding height. They signal
the control module of any change. If the height is too high,
the control module open the solenoid valves in the springs
with too much air. This allows some of air to escape,
lowering the car.
If the height is too low, the control module turn on the air
compressor. Then the control module open the solenoid
valves in the spring needing more air. Now more air flows
into the spring until proper trim height is restored.

43. This system works on compression of fluid with the help of
rubber washer or cups. There are four units fitted at four
wheels with independent suspensions, all the units are
hermitically sealed & connected to each other with the help
of pipes.
Whenever the wheel encounter a bumps, the tapered piston
of the unit is pushed upwards. The spring is actuated by the
fluid which is beneath & in the centre of rubber spring. This
upward movements of the tapered piston also forces the
fluid up through the interconnecting pipe to the other unit
on the same side of the car. The other side of the car is also
lifted, thereby the distribution of the shock of the bump
between the front & rear wheels of the car.

46. This system uses gas filled spring units (called hydragas
unit), one at each wheel. Each unit has a sealed chamber
containing a quantity of nitrogen gas at high pressure.
Below this chamber is a displacement chamber filled with
water based fluid.
When the wheel meets a bump, the fluid is passed,
compressing the gas. This action provide the springing
effect.
The two units on each side are also interconnected front to
back. Thus, when the left front wheel meets a bump a part
of the fluid from the left front unit is forced through pipes
to the left rear unit.

47. This action raises the left rear wheel also. There for shock
is distribution between the left front & left rear wheels &
consequently the side is improved.