Automotive Suspensions

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COLLEGE OF ENGINEERING ROOR


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ALL TERRAIN VEHICLE

An All Terrain Vehicle is a versatile automobile that can

kinds of terrains viz. sand, mud, earth mounds, stones or kind of uneven surfaces.


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The critical areas of failure are generally:

1. Rear roll hoop members

2. Side impact members

3. USM(under set member).

Rear Roll Hoop Side I

The material selection for the pipe is very crucial as is its thickness.

The minimum thickness is recommended to be 3mm. Other values may als

and tested as per requirement till the satisfactory results(strength) are obta


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MATERIAL SELECTION FOR ROLL CA

A proper equilibrium should be acquired between the design requirement

weight. The available materials that fulfil the requirements are AISI 1018, 10and 4130.

Some of the materials with their properties are given in the following table

Table 1: Material property


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SUSPENSION SYSTEMSuspension is the term given to the system of springs, sh

absorbers and linkages that connects a vehicle to its wallows relative motion between the two.

Suspension systems serve following purposes:

1. They contribute to the vehicle's road

holding/handling and braking.

2. They keep the vehicle reasonably well isolated from

bumps, and vibrations, etc.

3. They support the vehicles sprung and unsprung mas


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TYPES OF SUSPENSION SYST1. Coil springs- A round spring steel rod wound into a coil.

2. Leaf Springs- Several flexible steel plates of graduated length stacked o

3. Torsion Bars-A straight rod of spring steel fastened to one end of the bodarm moves up & down, torsion bar twists to provide spring action.

4. Air spring- Rubber cylinder or air bag filled with compressed air. This air pacton.


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SOME IMPORTANT TERMS

1. Sprung mass: It consists of the weight of the vehicle

supported by the springs. eg. Roll cage, chassis, driv

2. Unsprung mass: It consists the weight of the vehicle supported by the springs. eg. Tires, drivetrain compo

3. Roll centre: It is the nominal point in the vehicle at w

cornering forces in the suspension are reacted to the

body.

4. Scrub radius: Distance between the king pin axis an

centre of the contact patch of the wheel.

5. Jacking force: Sum of the vertical force component

experienced by the suspension links.


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DESIGN OF ATV SUSPENSION SY

The design of suspension is done to meet the following

requirement:

1. Controlled movement of wheel during vertical suspeand steering.

2. Adjusting static roll centre adequately to minimize th

forces and tendency of vehicle to roll.

3. Limit the value of tire scrub (scrub radius) to improve

line ability of vehicle.

4. Adjustment of weight distribution in front and rear to

the vehicles jumping performance.


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TOOLS USED IN DESIGNING SUSPEN

1. CAD modelling of mac pherson strut in PRO-ENGINEE

ELEMENTS 5.0.

2. Computations done in SHARK analyser software by L

3. Stress analysis done in ANSYS 13.0


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CAD MODELLING


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MAC PHERSON STRUT


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SELECTION OF CONTROL A

1. Double wishbone unequal non parallel U+A arm.

2. To provide enough clearance or more working spa3. Also helps in mounting the shock arms near the ball

to minimize the bending moment produced by spru


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DESIGN OF FRONT AND REAR SUSPEN

I. Track width at front and rear is assumed independe

II. Baseline geometry is designed, several values fed i(Lotus suspension analyser) to get the results.

III. After optimization in SHARK, different suspension par

evaluated.

IV. Certain parameters are: toe gain -.27, static roll cking pin inclination 5.1deg etc.

V. Suspension travel calculated is 6 and 4 inches for bu

rebound respectively.


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SPRING AND DAMPERFOX FLOAT AIRSHOX having adjustable damping coefficchosen keeping design and terrain in mind. The dampe

integrated infinitely progressive spring rate. This provide

clearance adjustability according to terrain. The spring

calculated as 26N/mm for front and 29N/mm for rear a

sprung mass to unsprung mass ratio as 10:1 and wheel n

frequency as 1.95 for front and 2.1 for rear. The required

is calculated from the following formula:

k(wheel) = (M.R)^2 * k(spring)


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SUSPENSION ANALYSIS IN SHAFollowing are the graphs as a result of suspension analysis done


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Automotive Suspensions

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