2. INTRODUCTION
• The Automobile chassis are not mounted directly on the axle, they are mounted by the
help of springs. This is done to isolate the vehicle body from road shocks which may be
in form of bounces, pitch, Roll or sway. The parts installed to isolate the vehicle from
shocks are known worked as a combine unit named as suspension system.
OBJECTIVE:
1. To prevent the road shocks from being transmitted to the vehicle components.
2. To safeguard the occupants from road shocks.
3. To preserve the stability of vehicles in pitching or rolling , while in motion.
TYPES OF SUSPENSION SYSTEM:
1. Steel springs: Leaf springs, Tapered leaf springs, Coil springs, Torsion bar.
2. Rubber springs: Compression springs, Compression shear-springs, Steel -reinforced
springs, progressive springs, Face-Shear springs.
3. Plastic springs: Air springs, Hydraulic springs.
3. LEAF SPRING:
• Figure shown in the previous slide is showing a Leaf spring. The spring consist of a
number of leaves called blades. These blades vary in length. The composite spring is
based upon the theory of uniform strength. The blade on top has max length and it has
2 eyes by which it is attached to the body. The other blades are attached to the master
leave by means of clips made of steel.
• This spring is mounted on the axle by means of U-Bolt. One end of the spring is
mounted the frame with simple pin, While on the other end it is made with the help of
shackle, this shackle is movable . When vehicle come across some bump there is a
change in leaf length this is provided by this shackle which gives some flexibility at one
end.
• These spring may be cambered as shown in figure or these may be flat. Flat springs
reduce the tendency to of vehicle to dip or pitching. Use of longer leaf spring give
better suspension. Generally rear springs are kept longer than the front springs.
• Spring eyes are generally filled with phosphor bronze bushes for heavy use. For light
SUV and vans rubber has been use as bush. The rubber bushes are quite in operation
and also the wear on pin or bush is negligible.
• Zinc or other corrosion resistant material is inserted between leaves to prevent them
from corrosion . Regular lubrication of shackle is necessary for good results.
5. LEAF SPRINGS:
• HELPER LEAF SPRING:
• Helper springs are provided on many commercial vehicles in addition to the
main leaf spring . These helper springs come into operatin when the vehicle is
loaded heavily. As the load is increased these helper springs share the load. In
general helper springs are provided on rear leaf springs.
6. LEAF SPRING:
MATERIAL USED FOR LEAF SPRING:
• Chrome-Vanadium steel
• Silicon-Manganese steel
• Carbon steel
LEAF SPRING MANUFACTURING:
Each plate is first descaled by shot blast. It is then heated along approximately half its
length and on reaching a suitable temperature, it is given a suitable shape and camber
angle . Then it is sent for heat treatment process where it’s hardness is controlled so
that it can bear the loads in use.
7. COIL SPRINGS:
• Coil springs are mainly used with independent suspension, though they have also been
used in the conventional rigid axle suspension as they can be well accommodated in
restricted spaces. The energy stored per unit volume is also double in the case of coil
springs than the leaf springs. Coil springs do not have noise problem . These springs
takes shear as well as bending stresses. Helper coil springs are also used to maintain
progressive stiffness against increasing loads.
8. RUBBER SPRINGS:
• Advantages of using rubber springs:
1. It can store greater energy per unit weight than the steel.
2. Rubber springs has excellent vibration damping properties.
3. Number of bearings is reduced considerably for rubber suspension system.
4. Rubber is more reliable. A rubber suspension can not suddenly fail like the metal
springs.
TYPES OF RUBBER SPRINGS:
1. Compression springs
2. Steel-reinforced springs
3. Progressive springs
4. Face shear springs
5. Torsion shear springs
9. SHOCK ABSORBERS:
• The shock absorbers absorb the energy of shock converted into vertical movement of
axle by providing damping and dissipating eh same into heat. Thus it merely serves to
control the amplitude and frequency of spring vibrations. It cannot support weight and
has zero resilience. Therefore dampers is better term technically to describe the shock
absorbers.
• Principle of operation of hydraulic shock absorber is than when a piston forces the fluid
in cylinder to pass through some hole, a high pressure resistance to the movement of
piston is developed, which provides damping effect.
• So for small vibrations damping is small and for large ones it automatically becomes
large.
10. INDEPENDENT SUSPENSION:
• In this suspension system wheels are sprung independent of each other, so that tilting of
one does not effect the other .
• ADVANTAGES OF INDEPENDENT SUSPENSION:
1. Softer springs can be used without rolling effect.
2. Improved steering precision since wheel movements are not linked.
3. Since in this system there is no solid axle beam, which required clearance for it’s vertical
movements, the engine and chassis frame can be placed relatively lower which means
engine position can be moved forward resulting in more space for passengers.
• DISADVANTAGES:
1. Initial cost is high.
2. Greater maintenance is required because of large number of bearings.
3. With the increase in wear of component it will effect the wheel alignment .
4. More rigid sub-frame or chassis frame is required.
11. WISHBONE TYPE INDEPENDENT SUSPENSION:
• The figure shows the wishbone
suspension in front axle. It’s main
component is wishbone both on the
upper side and the lower side. In-
between the wishbones the spring is
placed. The vehicle weight is transmitted
from the body and cross-member to the
coil spring and it goes to lower wishbone.
• Shock absorber is used with the coil
spring. The wishbones are in shape of V
and these wishbones are moved together
when the vehicle overcomes some bump.
• They make the wheel track constant and
avoids the type scrub.
• This type of suspension can absorb
Acceleration, braking and cornering
forces.
12. MAC PHERSON STRUT TYPE SUSPENSION:
• Here is this type of suspension only one
wishbone is used in the lower side. A
strut carries Spring and absorber also
carries stub axle on its lower par which
the wheel is mounted
• There is a limitation in wishbone type
suspension that the camber of the wheel
changes while on bump. In this case this
thing is eliminated as we use one wish
bone and a lower arm which gives flexible
movement to the wheel.
• This type of suspension is used in
Maruti800.
