PIMPRI CHINCHWAD POLYTECHNIC PROGRAM MECHANICAL ENGINEERING COURSE AUTOMOBILE

PIMPRI CHINCHWAD POLYTECHNIC PROGRAM: MECHANICAL ENGINEERING COURSE: AUTOMOBILE ENGINEERING (17526)

4. SUSPENSION SYSTEMS, WHEELS AND TYRES. CO 501. 1: Identify various components of Automobile. CO 501. 2 : Describe construction and working of various automobile systems.

SUSPENSION A vehicle runs on different types road conditions such as even, uneven, rough etc. • To isolate the passengers and other vehicle components from the irregularities of road surface, the vehicle chassis is not directly mounted on the axles. • Spring or suspension system is mounted between the passenger compartment and axle to isolate the chassis from axle. •

Objectives of suspension: �To safeguard the passengers against the road shocks and provide riding comfort. �To prevent the road shock from being transmitted to vehicle frame and other components. �Maintain stability of the vehicle by minimizing the effect of rolling and pitching. �To support vehicle weight.

Leaf spring/ conventional suspension

�Leaf springs are the most traditional type of suspension system. �They are used for light, medium and heavy commercial vehicles. �Leaf spring consists of following major components: �Leafs �Clamps �Shackle �U-Bolt

Independent Suspension �In independent suspension, all the road wheels are so connected to the frame that rise and fall of any wheel has no effect on the other.

Wishbone Type Suspension

Wishbone type Independent Suspension �It consists of upper wishbone and lower wishbone. �A coil spring with shock absorber placed inside it, is mounted between the wishbone structure. �Upper and lower wishbone arm are pivoted to the cross member of vehicle frame. �The vehicle weight is transferred from : Vehicle frame cross member coil spring Lower wishbone � This suspension resists up and down forces developed after bump, acceleration, braking, cornering.

Macpherson Strut Suspension:

Mac-Pherson…… � Mac Pherson suspension consists of a strut containing shock absorber on one side. � The strut is connected to the stub axle and wheel. � It consists of lower wishbone arm which is hinged to the frame cross member. � The load is transferred from the body member to spring strut to stub axle and lower wishbone arm. � This system is simpler than wishbone type and also reduces the unsprung weight. � This system provides maximum space in engine compartment. � It is most commonly used on all front wheel drive cars.

Trailing Link Suspension

Trailing Link Suspension…. . �A helical spring is used in horizontal position instead of vertical �One end of spring is fixed to cross member of frame while the other with one end of trailing link. �The othe end of trailing link is fixed with the shat which is carrying wheel hub. �When the vehicle passes over a bump, the wheel moves up and down and it winds and unwinds the helical spring by which vibrations are stressed.

Air Suspension

�Air suspension works on the principle of allowing or restricting the passage of compressed air through a small orifice. �They are often used in heavy load carrying vehicles requiring smooth suspension such as luxury buses. �The air suspension system consists of 4 air bags or bellows that support the sprung weight on the frame of vehicle.

Working �The air compressor sucks in atmospheric air through filter and pressurizes it. �Compressed air is stored in accumulator and can be withdrawn as per requirement. �If the pressure in accumulator exceeds a predetermined value, the air safety valve opens to bypass excess air.

Working… �The high pressure air passes to leveling valve via lift control valve �When the vehicle comes across a bump, based on the deflection of a particular air bellow, the leveling valve pumps in more air in that bellow. � the compressed air in the bellow or bag absorbs the vertical up and down vibrations. �Any excess air in the bellow can be released back by leveling valve in the pipeline.

Advantages: �It ensures constant vertical height irrespective of road surface. �It has constant frequency of vibration rather than metal springs which oscillate more rapidly. �It provides excellent ride comfort and noise reduction.

Limitations: �It offers high flexibility. Hence to improve the stiffness, air suspension is generally equipped with additional shock absorbers. �Failure of air compressor causes failure of entire suspension system.

Tyres: A tyre is a band of layers of iron , steel , rubber etc. mounted on the rim of a wheel and transmit the load and power to the road.

Desirable properties of tyre: �It should be strong enough to transmit vehicle load to the road. �It should be balanced, both statically and dynamically. �It should not wear away at the surface after long usage. �It should have adequate friction to roll on different types of road surface. �It should be light in weight to reduce unsprung weight. �It should be easily accessible for removing and mounting.

Conventional Tubed Tyre:

Components of tyre: �Tyre �Tube �Bead �Carcass �Tread �Valve

Tubeless Tyre:

Tubeless Tyre: �Tubeless tyre is an advanced version of conventional tubed tyre. �The tubeless tyre does not need separate inner tube. �The tyre have a special air retaining bead arrangement. �The tyre is directly mounted on rim and retains the air.

Avantages of tubeless tyre: �Improved safety �Ease of puncture repair �Slow leakage of air �Simple assembly �Better cooling �Lesser unsprung weight

Radial Ply & Cross Ply Tyre:

Factors affecting tyre life: �Inflation �Vehicle maintenance �Driving manners �Miscellaneous factors (like overloading, higher atmospheric temperature, road condition etc. )

Wheel alignment Positioning of steered wheel to achieve the following is called wheel alignment: 1. Directional Stability 2. Perfect rolling condition on steering 3. recovery after completing turn

Factors of wheel alignment �Factors pertaining to wheel: Balance of wheels, Inflation of tyres, Brake adjustment �Steering geometry Castor, Camber, King Pin Inclination, Toe-In, Toe-out �Steering Linkages �Suspension

Wheel Balancing �Static balancing �Dynamic balancing