Classification of Suspension Systems
The suspension system is classified as:
Types of Suspension System
(1) Conventional or Rigid System
(2) Independent system
(3) Rear end suspension system
(a) Longitudinal leaf spring rear end suspension
(b) Transverse leaf spring rear end suspension
(c) Coil spring rear end suspension
(4) Front end independent suspension
(a) Wishbone type or parallel link type
(b) Mac-pherson strut type
(c) Vertical guide type
(d) Trailing link type
(e) Swing half axle type
(5) Interconnected suspensions
(a) Air or pneumatic suspension system
(b) Hydro elastic suspension system
(c) Hydrogas suspension system
(6) Self levelling suspension system
1. The conventional system, in which the road springs are attached to a rigid beam axle. Applications-Truck, buses,jeep.
2. The independent system in which there is no rigid axle beam and each wheel is free to move vertically without any reaction on the other wheel
The suspension system are again classified as:
3. Rear end suspension system
(a) Longitudinal leaf spring rear end suspension
(b) Transverse leaf spring rear end suspension
(c) Coil spring rear end suspension
Application : Motorcycle.
4. Front end independent suspension
(a) Wishbone type or parallel link type
(b) Mc-pherson strut type. Applications Light duty vehicle like swift, wagon R. i 10
(c) Vertical guide type.
(d) Trailing link type
(e) Swing half axle type
5. Air or pneumatic suspension system.
Application : Volvo buses.
6. Hydro elastic suspension system.
Function and Requirement of Independent Suspension System
1. Its have light moving parts help the wheel to follow the road irregularities.
2. The unsprung weight is low.
3. It absorbs road shocks or impacts due to bump in road by oscillating.
4. Tyres also provides spring effect, but to a smaller extent.
5. It set the parameters like camber, castor angle and king pin inclination for better steering qualities.
6. Axle should not tilt and wheel remains vertical.
7. It reducing the shocks to passengers and for comfortable ride also reduce additional stresses in the automobile frame and body.
8. It require more rigid subframe or chassis frame.
9. It require more frequent attention on misalignment of steering geometry with the wear of component.
Advantages of Independent Suspension System
1. It may provide softer suspension, because the low spring rate (stiffness) enable large wheel movement.
2. In this the engine and chassis frame can be placed relatively flower which means engine position can be moved forward so more space for passenger.
3. The unsprung weight is low. The weight of the chassis and body relative to that of the wheel and axle is known as the unsprung weight. Hence ride quality is improved.
4. The variation in caster angle is reduced.
5. The independent suspension reduces the tyre scrub and hence increases tyre life.
6. In case of independent suspension, steering geometry is not altered with spring deflection as in case of conventional rigid axle suspension where the effect is observable during braking or accelerating.
7. It is possible to locate the springs apart enough to obtain understeer conditions, which is always preferred to over steer condition.
Disadvantages:
1.The initial cost is high
2. It require more maintenance because of more number of bearing.
3. The unbalance wheel forces are easily transmitted to steering wheel.
Types of Front Wheel Independent Suspensions
(1) Mac-pherson strut type or single wishbone system
(2) Wishbone type or parallel link type or double wishbone type
(3) Trailing link type
(4) Vertical guide type
(5) Swing-half axle type
Mac-pherson Strut Type Suspension System:
● A Mac-Pherson, engineer introduces a single wishbone with a telescopic strut type independent suspension system.
● This system, consist of a telescopic strut type shock absorber, a single arm and a diagonal stay.
● The upper end of a strut is fixed to the underside of the cross member of body through a flexible mounting and a lower part of the strut is fastened at the bottom by a joint to the lower wishbone arm.
● The lower part of the strut aiso carries the stub axle, on which wheel is mounted.
● The rotary motion of the steering wheel is transmitted to the lower part of the strut and turn the whole unit
● A helical compressive coil spring with shock absorber surround the upper part of the strut which takes care of the road roughness shocks and vibration by absorbing the shock and protect the vehicle from the stresses transmitted to the body.
Applications : Maruti-zen, Maruti-800, Maruti alto and Maruti swift.
Advantages
1. It is simple in construction
2. Keep wheel camber constant.
3. Its maintenance is very easy
4. Its light moving parts help the wheel to follow the road irregularities.
Disadvantages
1. Increases tyre wear.
2. Quality of ride depends upon shock absorber
3. Special equipment is required to check steering angle accurately.
4. Cannot withstand heavy load.
Wishbone Type Suspension System
● It consists of two wishbone arm pivoted to the frame.
● The upper wishbone arm is shorter in length than lower arm.
● This help to keep the wheel track constant, so avoid the tyre scrub and thus reduces the tyre wear.
● A small change in the camber does occur with such arrangement.
● The wishbone type independent suspension system is most popular.
● The coil spring is located in between the lower wishbone and underside of the cross member:
◆ The weight of vehicle is transmitted from the body and the cross member to the coil spring through which it goes lower wishbone member
● A shock absorber is placed inside the coil spring and is attached to the cross member and to lower wishbone member.
● Because of "V' shape of arm, the wishbones not only position the wheels and transmit the vehicle load to the spring,but these also resist acceleration, braking and side forces.
● When the vehicle come across a bump and wheel is tended to move up, the lower and upper arm (control arm) moves up and the coil spring is compressed so shock absorber (damper) damps the vibrations set up in the coil spring due to road irregularities.
Advantages of Wishbone suspensions
1) In this type wheel track is constant, so it avoid tyre scrub, reduces tyre wear.
2) Right and left side suspension of vehicle is independent, so vehicle is stable on uneven surface or on the pot hole or digs
3) Because of V shape of arm, the wishbone not only positions the wheels and transmits the vehicle load to the spring also resists acceleration, braking and side forces.
4) It requires less vertical space compared to MacPherson, so less ground clearance and better vehicle stability.
5) Low spring rate.
6) Steering geometry is not altering with spring deflection
Difference between Rigid Axle Suspension and Independent Suspension
Rigid axle suspension → Independent suspension
1. The spring is attached to rigid beam axle. → There is no rigid axle beam.
2. Wheels moves (deflect) vertically having reaction on other wheel. Or Axle tile and wheel no longer remains vertical → Each wheel move vertically without any reaction on other wheel. Or Axle does not tile and wheel remains vertical.
3. Used for heavy vehicle like, truck. → Used for light vehicle like car at front.
4. More tyre scrub, reduces tyre life. → Less tyre scrub, increases tyre life.
5. Steering geometry alter/change. → Steering geometry not alter.
6. Provide slightly rigid suspension due to higher spring rate → Provide softer suspension due to low spring me (stiffness)
7. Wheels may wobble. → No chances of wheel wobble.
8. Road adhesion less → Road adhesion more.
