Front Suspension and Steering:Double wishbone with unequal A-arm lengths is used. Front suspension is very significant and should allow large wheel travel (-50mm to 150mm). Suspension and steering behave as a coupled-system and are inter-dependent.

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It is needed to have target values to begin design.These values are turning radius and wheel-base.Hence, the track-width is found.

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The main objective of the front suspension is to provide the maximum wheel travel in bump and droop (-50mm to +150mm) is chosen. Moreover it should provide good amount of traction while it comes to cornering.

Suspension coupled with steering should provide better directional stability.Optimum values of all the geometric parameters like camber, caster, KPI etc. have to be considered.Double wishbone geometry with unequal arms was identified as the most suitable configuration. It ensures lesser camber variations hence large patch of tire will remain in contact with ground resulting in better traction.

During cornering inner wheel undergoes droop while outer wheel undergoes bump this decreases the contact patch of the wheels. This can be overcome using a unequal A-arm lengths.

Static camber of 00 is used but when the car is loaded with the drivers weight a small amount of negative camber is obtained. Because of negative camber gives better traction (larger contact patch) while cornering. Static camber setting can be done using Ball-joints.

Caster is maintained 00 throughout. Kingpin Inclination is given which gives self-centring effect for the steering and reduces positive camber gain on travel. Ground clearance of about 300mm is kept.Toe-angle variation is very less giving better stability.Static toe-angles can be varied using tie-rods. And toe-in is used for straight line stability however toe-out is used for manueurvability.

Roll-centre is kept high above the ground, close to C.G. such that roll-moment is less. So the rolling tendency of vehicle is negligible.

SHOCK ABSORBER:Coil over springs were used which could be adjusted for pre-loading. Motion ratio of 0.6 is to be used such that the spring compresses by 1/6th amount of wheel travel giving better ride quality.Optimum strut angle is chosen w.r.t. vertical to increase the effectiveness of the spring. However in the side view it is placed vertical.

Ride frequency of around 1.8 Hz is assumed (from literature) and the ride frequency of front is usually lower than the rear that is 2 Hz.

F = 1 / 2 * pi

Hence we find the required value of the spring.

Steering:Mainly, a steering system must provide a feel (of front tires) and a sense (of contact patch) to the driver. It must be rigid enough to undergo component deflections.Steering response of the vehicle is made fast by giving proper KPI, Caster and Trail values.Rack and pinion manual steering system has been chosen.There are many steering geometries, of which Ackermann geometry has been chosen. It is when a vehicle goes around a corner, the inward wheel turns bit more than the outward to effectively complete the cornering without slipping.

As can be seen from the graph the designed Ackermann is very close to the ideal Ackermann.

Toe-Angle variation a. BUMP b. ROLL c. STEER

Calculations:Ackermann condition:cot0 coti = R= Turning radius (mm)= 2223 mmo= Outer locking Angle= 29.280 i = Inner Locking Angle= 42.870

Percentage Change in Turning Radius: R = 2.249 %

Bump-steer and Roll-steerPosition of rack and the length of the tie rod was chosen so as to minimise the dynamic toe changes. A slight change in the position of inboard point of tie-rod either above or below the Ideal center will lead to roll steer. And a slight change in the position of inboard point of tie-rod either inward or outward to axis of line joining inner upper and lower wishbones will lead to bump steer.