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INTRODUCTION

Geu motorsports is the team of 25 member competing in formula student India competition .it is a student based competition whose main goal is to provide students the opportunity to gain experience in designing, building and racing the single seated race car in well-known racing circuits. The methodology chosen for calculating the suspension and steering points is both analytical and reverse engineering. The wheel travel is first assumed according to the standards of FSI rulebook. Being the first car of GEU motorsports the primary motto of our suspension design is to analyse the behaviour of ride when the I-centres are at the centre of the tire at both rear and front of the car. The results are discussed at the end and were quite satisfactorily positive.

VEHICLE DESIGN OBJECTIVE

The car must have high performance in terms of acceleration, braking and handling qualities. The car must also be low in cost, easy to maintain and reliable. The production rate is estimated to four cars per day for a limited production run and the prototype vehicle should cost below $36000. The challenge for the students is designed and build a prototype car that meets these goals. Each car will be compared and judged with other competing cars to determine the best overall cars. Our objective is to design that can be easier for production cum reliable with much higher affordability. The chassis has been designed such that its natural frequency is 35 Hz which maintains the higher damping capability. Weldments and grooving re done precisely to overcome the distortion and the material used for SLA suspension system is D & H 309 Mo. Mild steel is also used at some points of the suspension assembly such as in bracket manufacturing and at wishbone ends where bushings were installed.

COMPETITION EVENTS AND JUDGING OF THE CARS

The competition is divided into static and dynamic events. The static events are:

Presentation

Engineering Design

Cost Analysis

The dynamic events are

Acceleration

Skid pad

Autocross

Endurance and fuel economy

ACCELERATION EVENT

The objective of the acceleration event is to evaluate the cars acceleration in a straight line on flat pavement. The cars will be staged 0.3m behind the starting line and when the cars cross the starting line the time will start. The goal is located 75m ahead of the starting line. Each team will have two drivers, who can do two runs each, total of four runs.

SKID-PAD EVENT

The objective of this event is to measure the cornering ability of the car on a flat surface while making a constant radius turn. The skid pad layout will consist of two circles with a diameter of 15.25mm separated by 18.25m. The driving part will be 3m wide.

AUTOCROSS EVENT The objective of the autocross event is to evaluate the cars manoeuvrability and handling qualities on the tight course. The autocross course will combine the performance features of acceleration, brake and cornering.

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Straight - No longer than 60m with hair pins at the both ends and no longer then 45m with wide turns on the ends.

Constant turns - 23m to 45m in diameter.

Hair pin turns - Minimum of 9m outside diameter.

Slaloms - Cones in a straight line with 7.62m to 12.19m spacing.

Length - Approximately 0.805km.

ENDURANCE AND FUEL ECONOMY EVENTS

To evaluate the overall performance and to test the car reliability and endurance event is performed. This event is combined with a fuel economy event implying that the fuel economy will be measured during the endurance event. A single 22Km heat is made during which the teams will not be allowed to walk on their cars. A driver change must be made during a three minute period at the midpoint of the event. The layout of the endurance track is similar to the layout of the autocross track.

Straights - No longer than 77m with hairpins at both ends or no longer than 61m with wide turns on the end. There will be passing zones at several locations.

Constant turns - 30m to 54m in diameter.

Hairpin turns - Minimum of 9m outside diameter.

Slaloms - Cones in a straight line with 9m to 15m spacing.

Miscellaneous - Chicanes, multiple turns, decrease in radius turns etc. The minimum track width will be 4.5m. In both the autocross event and the endurance event the suspension design and steering geometry is of major importance.

JUDGING OF THE CARS

The cars are judged based on the performance in the static and dynamic events.

STATIC EVENTS

Presentation 75 points Technical Inspection No points Cost And Manufacturing 100 points Design 150 points ______________________________ Total 325 points

DYNAMIC EVENTS

Acceleration 75 points Skid-Pad 50 points Autocross 150 points Efficiency 100 points Endurance 300 points ______________________________ TOTAL POINTS 675 points

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RULES RELEVANT TO THE CHASSIS DESIGN

The major part of the Formula SAE Rules concerns the safety of the drivers. But there are few rules that will have to be taken into consideration when designing a chassis. WHEEL BASE AND VEHICLE CONFIGURATION:

The car must have a wheel base of at least 1525 mm. VEHICLE TRACK WIDTH:

The smaller track of the vehicle (Front or Rear) must be no less than 75% of the larger track. GROUND CLEARANCE:

It must be sufficient to prevent any portion of the car (Other than tires) from touching the ground during track events. WHEELS AND TIRES:

The wheels of the car must be 203.2 mm or more in diameter.

THE SUSPENSION SYSTEM

The suspension system is the crucial part of any car assembly as, it provides the support the tyre- wheel assembly and connects frame to the wheels to complete a chassis assembly. The suspension system has the following functions in a car assembly:-

1. Optimizing the handling of the vehicle 2. Controlling ride rates and squats in total ride 3. To provide comfort to driver and passengers 4. Controlling the wheel travel to a critical level

The goal of any car is to maintain the maximum achievable acceleration in the approximate directions .The main approach of the work done in our debut racing car is to control the squat to a critical level and maintaining the roll centre of the suspension arms near to the centre of gravity .the possible considerations are also been taken in reducing the cost of assembly and increasing the strength of the same.

SUSPENSION DESIGN ASPECTS

The purpose of the suspension is to make the job easier for the tires and give a predictable behaviour so that the driver will have control of the car. When designing a suspension there are number of factors that influence the behaviour of the suspension and a lot of these factors also interacts in a way or another. The factors taken into this work are as follows below:

WHEEL BASE

The wheel base has a big influence on the axle load distribution. A long wheel base will give less load transfer between the front and rear axle than a shorter wheel base during acceleration and braking. A long wheel base will therefore be able to fit with softer springs and will increase the level of comfort for the driver. On the other hand a shorter wheel base have the advantages of smaller turning radius for the steering input. The wheel base taken for present car is 1560 mm.

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TRACK WIDTH

The track width is of major importance when designing a vehicle. It has influence on the vehicle cornering behaviour and tendency to roll. The larger the track width is the smaller the lateral load transfer is when cornering and vice versa. The track width of our car is 1250mm for front and 1170mm for rear. As our primal motto is to make the vehicle for less turning radius. The lateral load transfer on the vehicle will be less as compared to vehicle on unequal or small track width.

KING PIN AND SCRUB RADIUS

The king pin axis is determined by the upper ball joints and lower ball joints on the outer end of the A-arm. This axis is not necessary centred on the tire contact patch. In front view the angle is called the kingpin inclination and the distance from the centre of the tire print to the axle centre is called scrub or scrub radius. The distance from the king pin axis to the wheel centre plane measured horizontally at the axle height is called spindle length.

The larger the Kingpin inclination angle is the more the car will be raised regardless of which way the front wheels are turned. If there is no caster present this effect is symmetrical from side to side. The raise of the car has a self-aligning effect of the steering at low speeds.

When a wheel is steered it will lean out at the top, towards positive camber the Kingpin inclination angle is positive.

If the driving and breaking force is different on the left and right side this will be introduce a steering torque proportional to the scrub radius which will be felt by the driver at the steering wheel.

CASTER AND TRAIL

In the side view the king pin inclination is called caster angle. The distance from the king pin axis to the centre of the tire print on the ground is called trail or caster offset. The effect considered in this work are:

The larger the trail is the higher steering torque is needed.

Caster angle will cause the wheel to rise and fall with steer.

Caster angle has a positive effect on steer camber. With positive caster angle the outside wheel will camber in a negative direction and the inner wheel in a positive direction causing both wheels to lean into the turn.

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INSTANT CENTRE AND ROLL CENTRE

Instant centre is the momentary centre which the suspension linkage pivot around as the suspension moves the instant centre moves due to the changes in the suspension geometry. Instant centres can be constructed in both the front and side view. If the instant centre is viewed in front view a line can be drawn from the instant centre to the centre of the tires contact patch. If done for both the sides of the car the point of the intersection between the lines is the roll centre of the sprung mass of the car. High Instant centres will lead to a high roll centre and vice versa. The lateral force generated by the tire generated a moment about the instant centre which pushes the wheel down and lift the sprung mass. This effect is called jacking.

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TIE ROD LOCATION

The location shall be such that bump steer effects are kept minimum. Bump steer is the change in toe angle due to wheel travel. The length of the lever arm from the outer tie rod end to the upper ball joint determine together with the steering rack ratio the total ratio from the steering wheels angle to the wheels steering angles. ANTI FEATURES:

The longitudinal weight transfer during study acceleration or braking is a function of wheel base, CG height and acceleration or breaking forces. The anti-effect in suspension describes the longitudinal to vertical force coupling between sprung and unsprang masses. The side roll centre is 22.91mm above the ground. Hence it is 2.49 mm close to the centre of gravity. To keep the centre of gravity close to the roll centre we will be using the mounting points near to the base of the frame. This will be helpful during cornering and for some part of lateral

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acceleration. The anti-features are calculated in terms of Anti dive and anti-squat of the vehicle that can be controlled with the help of suspension systems. The front and back braking distribution is taken as 65% for front and 35% for rear wheels hence the anti-dive force is derived is 33.552KN. The anti-dive experienced on the vehicle is 196%. The anti-dive is normally taken beyond 150% for the race cars. The calculated anti dive is quite high but, it is good for car because maximum weight is distributed in rear such that the rear mass will overcome the front dive features. The anti-dive feature are calculated and assumed for low mounting points. The reference of the force imparted by breaking is taken from the break calculation report.in practical aspect there was no problem in car while showing its anti-squat characteristics. The car gives the equilibrium behaviour over when the wheel are suddenly locked.

ACKERMAN STEERING

If both front wheel are tangent to concentric circles about the same turning centres. Which lays on a line through the rear axle the vehicle is said to have Ackerman steering. This result in the outer wheel having a smaller steering angle than the inner. If both wheels have same steering angle the vehicle is said to have parallel steer and if the outer wheel has the largest steering angle than the inner is called reverse Ackerman. Race car are often operated at high lateral acceleration and therefore all tires operate at significant slip angles and load on the curve inner wheel are much less than the curve outer wheels due to the lateral load transfer. Using a low speed steering geometry on a race car would cause the curve inner tire to be dragged along at much higher slip angles than needed and this would only result in raises in tire temperature and slowing down the car due to the slip angle induced drag. The angle for the steering mount has been taken by calculating the I-centre of the point on upright meeting at the mid of differential. The figure shows the following procedure. The geometric calculations are used widely for finding the position of steering mount on the uprights. The advantage of using this kind of geometric representation is that it sets the analogy with suspension designs and being I centre on differential it sets the symmetry along the vehicle. The angle of the mounting taken on the uprights are taken as 20 deg. This helps in adjusting the toe in and toe out of the steering of the vehicle.

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CAMBER

Camber angle is the angle between a tilted wheel plane and a thought vertical plane. Positive camber is defined as when the wheel is tilted outward at the top relative to the car. The camber angle has influence on the tires ability to generate lateral force. A cambered rolling produces a lateral force in the direction of the tilt. The figure shows the change in the chamber of air car at 1.8G acceleration. The change in chamber angle is quite satisfactory as the car will not show any Detachment of the wheel from the surface.

Toe

Toe adjustment can be used to overcome handling difficulties sin the car rear toe out can be used to remove the turn-in. minimum static toe is desirable to reduce rolling resistance and unnecessary tire heating and tire wear caused by the tire working against each other.

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Track width and wheel base

The track width and wheel base will have influences on the amount of load transfer between the front and rear axle during acceleration and the breaking and the load transfer from curve inner to curve outer wheel during cornering. The wheelbase should be as short as possible, but not shorter than 1525mm, to optimize the ability to make sharp corners. A larger track width will have the disadvantages of a narrower A-arm angle to allow required wheel angle, causing the A-arm taking up more forces in the longitudinal direction. The track width taken for front is 1560mm and for rear it is 1170mm the main cause of taken rear less is to make turning radius less and vigilante to perform at autocross event with effective handling.

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WORKING PRINCIPLE

Tyres and wheel assembly being the most important part of the car are to be provided with suspension systems that can provide supports to both drive train and the vibration occurring in chassis. It also helps in controlling the bump steer ratio of the steering systems. The suspension system also help to keep the optimal contact of the tyres on the road with a considerable wear and tear but, the most important consideration taken in this car is to maintain the comfort level for driver. The schematic figure of original suspension systems engaged in present car can be seen below.

The wheels and brake disks are connected to upright assembly that is self-designed and reduced in mass according to the weight percentage required by the brake assembly. The rod end joints are used to connect the a-arms or the control arms to the chassis whereas the spring damper system is used to connect the frame and lower and upper a-arms with correct motion ratios required. The push rod and pull rod assembly is taken as per the piston rod used in spring damper system. Hence the use of pushrod and pull rod defines the characteristic of the suspension assembly.

The uprights are the main members connected to the wheel assembly to support the arms and the rockers attached to the bell crank .the upright acts according to the wheel travel. The required wheel travel for FSAE is 2.6 cm hence to set as a slandered we have taken it higher than the required. The uprights transmits the wheel travel movement to the rocker arm which further gets transmitted to the bell crank which transmits the force according to the motion ratio taken or assumed. The spring damper system consist of two further classified into two parts

1. Coil over damper systems 2. Anti-roll systems

The coil over damper system is basic mechanism which is based on the principle of storing the energy and then damping it with help of any damping media. The spring will continue to compress till l the whole energy is dissipated. Dampers are used for energy dissipation control. They are used to slow down and reduce the amplitude of vibration occurring due to bumps imparted by road conditions and cornering. The anti-roll system consist of torsion bar with a lever on each end. The working depends upon the movements of each ends of bar, if they are not same them the anti-roll bar will be twisted. This assembly is both complicated and expensive and can be used where anti roll hoop of the frame is either small or not able to make spring damper system to work properly.

The pushrod and pull rod assembly taken in our design is according to the position of piston and cylinder assembly of the damper system. The chosen mechanism in current car did not have bell crank lever mechanism due to lack of available ergonomic level in the frame and constraints of rules provided by FSI. Following are the situations that are taken into consideration while designing the suspension design for GEU Motorsport

1. Bump situation

If the car goes through a restrictor or a threshold then the equal amount of change in movement will occur in both left and right wheel assembly. This will result in actuation of spring and damper assembly which will be displaced equally, of which one will be compressed and another will be released.

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2. Cornering situation

If the car drives through corners, its body will tend to roll to outside of a bend, as a result the wheel assembly will move the outer wheel up side with respect to the chassis and the inner wheel will move down. The load on the outside spring damper system will be greater than the inner system or the inner wheel will be partially unloaded.

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REQIREMENTS

To design the suspension system of GEU motorsports, a set of requirements were taken into the consideration that were formulated by team according to available information. The requirements can be split into following parts:-

1. High reliability 2. Low weight 3. Low centre of gravity of frame 4. Low yaw inertia 5. Low production cost. which includes the both prototypes and series of production of 1000 cars/

year 6. Must comply to FSI rules

The spring damper system’s specific requirements are

7. The motion ration has to set with the chosen dampers. 8. The spring damper must be adjustable to control the stiffness and wheel travel. 9. The setting of whole suspension system must be adjustable. 10. Friction has to be kept low. 11. The system should be free to play for full desired travel. 12. Minimum wheel travel as prescribed by FSAE rules

The car must be equipped with fully working suspension system with shock absorber at both front and rear assembly, with usable wheel travel of 50.8 mm with 1 inch jounce and 1 inch rebound with driver seated .the judges have right to disqualify the cars which do not have the requirements fulfilled.

13. Visibility as prescribed by the rule

Suspension mounting points must be visible at technical inspection, either by direct view or by removing covers. Ground clearance as prescribed by the rules

The ground clearance must be sufficient to prevent any position of car (other than tires) from touching the ground during track events and, with driver aboard there must be a minimum of 1 inch of static ground clearance under complete car at all time.

The rims

One of the first things to consider is what kind of rim that will be used. The dimension of the rim determine together with the brakes the space available in the rim for the placement of the ball joints.

The brakes

With the dimension known, the space left in the rim and the location of the lower ball joint can be estimated. The final placement of the lower ball joint is given by the packing of the rims.

The front view geometry

The possible location for the lower ball joint is now set by the space left after fitting the brake system to obtain proper roll camber characteristics the front view swing arm length, FVSA length, is calculated by using

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Side view geometry

The design of the side view geometry is based on the desired anti features for the front suspension of a rear wheel driven car the only anti-feature is anti-dive and this gives the wanted angle of the side view swing arm. A length of the arm, SVSA length determine the amount of longitudinal wheel travel during bump and drop.

CONTROL ARM PIVOT AXIS

In the front view upper control arm inner pivot point is marked as point and the upper ball joint a point. Projection on to the longitudinal plane is marked as point. Corresponding points for the lower control arm is. These points are then transferred into the side view. A line is drawn from the side view instant centre and through point and a bit further. This arbitrary point is marked as point. The same procedure is made for point giving the location of point. These points are than projected into the front view. In both the front and side view a line is drawn from point through point and beyond point. This is repeated for the lower control arm using points. The inner pivot points are wanted to be parallel with the car’s centreline. This is made by drawing a vertical line from point. This lines intersection with the line from point through point is the desired location of point in the front view. This is repeated for the lower control arm with the corresponding points giving point. Points are than projected into the side view and lines are drawn through point giving the axis of the inner pivot points. The points can be placed anywhere wanted as long as they still are on the lines.

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TIE ROD LOCATION AND ACKERMANN GEOMETRY

A span from 0% Ackermann to 100% Ackermann is wanted, negative Ackermann is used on high speed race cars only, and due to this tie rod have to be placed in front of the upper control arms. This will cause the compliance effects to work in a negative way. But if the tie rod were to be located behind the upper control arms it would result in too less adjustability of Ackermann geometry. According to our calculations the Ackerman percentage is 144% so that at tight turns the steering coordinate easily.

Front spring damper system

The main consideration in designing the front suspension system is to use low mounting point as it is not only beneficial for height of centre of gravity but also in using the waste space beneath the driver legs. The mounting points for suspension parts are also considered for the same. The spring damper are also attached on chassis at lower point to lower centre of gravity and also to work with utter accuracy to manifest required anti squat / anti dive. The various parts of the systems are described later in the report.

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FRONT BUMP SYSTEM

The bump system in the car includes the push rod assembly which is included in the spring and damper assembly with upright with required designs according to caster angle, camber angle taken. If the wheel is over through any bump, the wheel and upright are pushed down and causing the chassis system to push the piston and cylinder downwards.

BUMP MOTION RATIO

The coil over damper systems are compressed and extended in such a velocity range to work properly. The velocity of the damper is of course dependent on the velocity of the wheel and the suspension system. The ratio between damper travel and wheel travel is called motion ratio.

MR= Xdamper /Xwheel

Due to kinematic of suspension system the relation between wheel travel and damper travel is highly nonlinear. To analyse the kinematics of the system simulation graph is used . This model allows us to analyse the steering, wheel bump and body roll. The resulting motion ratio can be 0.5+- 1%.

DAMPERS

The dampers used in the car is custom made according to the calculated value. The stiffness and length of the spring damper system is adjustable. The shock absorbers can be mounted at any desired location because they are pressurised with fluid. To obtain the right damper velocities the motion ratio is taken minimum to 0.5 FSI rules require minimum wheel stroke of +25.4 mm. The minimum stroke of the damper is 28mm and the required is 26mm. the front and rear are the midget spring shocks as per the requirement of stiffness and damping coefficient.

The chosen shocks allows to create smooth ride so that the driver is seated with utter comfort level. The suspension mount is not multilink hence it is easy to assemble and manufactured. The damper has enough damping coefficient to overcome the body’s vibration.

REAR SPRING DAMPER SYSTEM

The rear assembly is a pull rod suspension system, the main reason to choose this mechanism is to simplify the differential and drive train assembly. The car doesn’t have bell crank mechanism as the rocker and other mechanism has tendency to make assembly more complicated. The rear spring damper systems are mounted on the upper a- arms to make ergonomic condition more suitable to handle the required weight distribution, lateral acceleration and the cornering conditions.

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REAR BUMP SYSTEM

One of the most important choices is to be made when deciding on a suspension concept is between pushrod and pull rod configuration. A schematic bump suspension system is visible in figure. It shows a rear view of the left wheel and right wheel and its upright, a vehicle body and suspension between. As can be seen the pull rod has been mounted in rear wheel assembly on the upper wishbone which can also be mounted with the help of bell cranks near the bottom of the chassis. The orientation of

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The spring damper can be chosen according to the (α) angle. The method used to finalize the suspension type is the statistical method and quality control method. The selected orientations are the common and are maximum in use. The main advantage of the chosen orientation is to lower the centre of gravity. Secondly, a pull rod in in tension, it can be lighter than equivalent pushrod that might fail due to buckling. The alternative is pushrod system, which can be in second figure. This concept is used in lower arm. Hence the front suspension system is a pushrod system which have connection between lower A-arm and chassis. The direct connection of system of spring damper causes the lowering of centre of gravity. The rod ends used in the control arm are strong and stiff such but cannot endure bending hence the connection rod will be directly mounted on the upright. During cornering the outside arm is in tension, while the lower one is in complete compression this compressive force is 1.8 times the lateral force on the tyre because of the leverage between the road surface and upper and lower wishbones.in case if the car drives over a bump the upper connections will be loaded with the compressive force and lower one with tensile force hence a pull rod assembly is used to increase performance during bump condition.

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DESIGN OF UPRIGHTS

Uprights are designed for attaching the suspension arms and spring damper system to assemble the wheel with the chassis system. The design of uprights are considered to be based on three point’s i.e.

1. Suspension arm points 2. Steering mounting points 3. Brake calliper mounting points.

The chosen design is according to the futuristic approach of our work to be done when the required caster and chamber will be changed. The designing of upright is done on SOLID EDGE by drafting method and then the solid works is used for the modelling of the same. The break mounting points were taken according to the geometry required by the braking systems and were mounted at rear of uprights so that less jerk will be felt for ride comfort. The steering and suspension mounting points were taken on the uprights required area of billet. Then then the front and the side view is generated with the help of the orthographic views. The 3D model is then created on the solid works by the help of ANSYS 14.5 the uprights were checked in static structural module for the FOS and shear stress and deformation when the component of force due to forces are:-

1. Tractive force is 50 KN 2. Lateral force is 25 KN 3. Vertical force is 50 KN

The figures shown shows the procedure and the approach use in designing the uprights.

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ANALYSIS OF UPRIGHTS

HUB DESIGNS

The hubs are the part connected to the uprights that provide the torque to transmit to the wheels with help of a drive shaft. The hub are designed such that they are both light weight and the suspension arms ends do not touch the alloy wheels forged surfaces. The hub design parameter consist of PDC diameter and the collar that has to mesh with the wheels collar with tolerance of -0.1mm. The biggest challenge is faced when the hub is to be selected for low weight but, there is requirement of weight in rear as well as front for equalising the distribution. Hence, the mild steel hub are considered for making it cost effective and reliable. The long bearing of NBC with a bearing lock and CV joint is used in assembling the hub with uprights. The small spring washers are used to make the assembly tight and worth working. STEERING MOUNTS AND POINTS Steering rack that has been selected is of 40 cm in length hence according to toe angle on uprights discussed earlier were used here to mount he steering rack. The mounting points was then updated to the mid centre of the upright so that the line of action of turning moment exerted on the wheel must not wobble during over steer or understeering effect.

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BRACKETS

The brackets are the major aspect of suspension fabrication as it provides required wheel travel with help of the chosen mechanism as shown in fig. the chosen mechanism for the suspension arms is the revolute that has the degree of freedom of one. Hence it is most considerable type of mechanism. The plate chosen for fabricating the brackets are of 5mm of thickness that has FOS of 3.5. the rubber bushing are used inside of the pipe of Mild Steel of thickness 5mm that is used to reduce the detect contact of metals and provides stability to the arms while breaking.

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Springs and Damper Calculations

The minimum wheel travel permitted in the competition is specified as 50.8mm and 25.444 jounce travel and 25.4mm rebound travel. Therefore the design is aimed for minimum possible wheel travel as for FSAE vehicle it is believed less wheel travel permits lower ride height and thus centre of gravity.

Deflection or sag calculation: Gravity = 9.81m/s^2 Mass on front wheels = 100kg Mass on rear wheels = 201.8kg Motion ratio front = 1:1 Motion ratio rear = 1:1 Spring travel = 70mm

Formulae

Front motion ratio = Minimum rebound wheel travel/front sag wheel travel Rear motion ratio = Minimum rebound travel/rear sag wheel travel Motion ratio = Wheel travel/spring travel

FRONT REAR

Spring rate

Sag Motion ratio

Wheel travel

Spring rate

Sag Motion ratio

Wheel travel

29.8N/mm 33.64 mm

0.77 53.9mm 39.4N/mm 38.18 mm

0.68 51mm

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FRONT REAR

Spring rate = 29.8N/mm spring rate = 39.4mm I.D = 43.18mm (1.70inch) ID = 43.18mm O.D max = 56mm OD = 56mm Free length = 127.00mm (5inch) Free length = 165mm Compressed length = 200mm Compressed length = 200mm Extended length = 270mm Extended length = 275mm FORMULA Number of coils: - Gd^4/8D^3R Where:-

D = mean coil diameter G = modulus of rigidity d = wire diameter of spring R = spring rate

FRONT REAR

d (in mm) N d (in mm) N

4 0.489 8 5.91

5 1.18

8 7.75

TESTING

Suspension of the fabricated car was manufactured in three ways i.e :-

1. Rig testing part 2. Road testing of damper on the vehicle. 3. Vehicle annual safety certification.

The method used here for testing the suspension of car by GEU motorsports is road testing of damper on vehicle. The damper in this testing is charged by stroking it to several cycle called as purging. If more than three stroke is taken to purge there is surely a sign of fault. The damper fluid used in the used damper is Gabriel which has high coefficient of damping. The cycles taken by the suspension’s spring and damper system is 1 to 1.5 cycles to form complete purging. Hence the fault percentage decreases by 75% while testing. The road testing was done for the present car by the following methods

1. Severe tests for short distance 2. Ride and handling tests public roads.

The severe test for long distance was done at 87km/hr. of speed for a distance of 500 meters. The results were satisfying as the wheel travel was nearly equal to 26.8 + 3mm with an error of 13% error.

Handling tests were done on the normal public roads for a distance of 1 km in which the driver has to change gear up to the overdrive gear. The speed reached was 110 km/hr. and the ride with steer handling were quite satisfactory with some slipping in the steering universal joints. The tilt tests were also satisfactory as the chamber change was low as possible and do not detaches form the Ground during operation.

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