Suspension is the term given to the system of springs, dampers and linkages that connect the body of the vehicle (the chassis) to the wheels. For a road car, the suspension is an optimisation of the vehicle’s handling and ride comfort for the driver. For a race car, it is maximising the handling and acceleration. The suspension design must be light weight, cost effective and must provide suitable handling characteristics for the Class 1 Formula student event. The task for the suspension team is to design a suitable suspension system incorporating previous teams’ designs to optimise the car.

After initial research, iterations of the kinematic design were carried out, with kinematic and dynamic analysis working hand-in-hand. Once this was set, using steady state hand calculations for the forces, the components were designed and analysed using FEA. The designs have been finalised and are ready for manufacture.

The main performance factors of the suspension system are;

1.     Roll centre location has to be along the central axis of the vehicle and as close to the centre of gravity height as possible, to reduce jacking and body roll.

2.     A balance of Anti-Features; Anti-dive on the front for improved stability, Anti-squat on the rear for improved acceleration. Values should not be equal to 0 or 100%.

3.     The optimum camber for the tyre used is -3° to 0°. The camber should be adjustable by +/-2°.

4.     Adjustable Toe at the front and rear. +/-2° of adjustability. Initial settings, Front Toe equal to 0-3° Toe out

5.     The driveshaft should be perpendicular to the vehicle’s centre plane.

6.     The rim size will be 13” as market research shows this is the optimum size. Two sets of tyres for wet and dry conditions

7.     The kingpin offset ideally is zero, packaging does not allow this. The offset should be as small as possible. Average is 5-7°.

8.     Front caster should range from 0-3° for self-centring torque.

9.     Spring should be as stiff as possible but allowing for the specified travel requirements

10.  Ride height as low as possible to minimise lateral load transfer. Must not ‘bottom out’.

11.  Roll stiffness is increased by spring and anti-roll bar stiffness. The distribution of stiffness front:rear is dependent on driver preference. If the roll stiffness is too stiff the inside rear wheel will be prone to lift.

12.  The best damper settings will control the body motion to keep the car fairly level but allow the suspension to follow the surface.

13.  Minimum wheelbase – 1525mm

14.  Smaller Track must be no less that 75% of the larger track

15.  Low frontal area

16.  Shorter wheelbase decreases the turning radius of the vehicle

17.  Low un-sprung mass

The proposed budget for the suspension team is £3380, with large savings coming from sponsorship and machining the components in-house at the University. If these were outsourced the price would increase dramatically. Budget restrictions will always be in place and this was no different with the team and University aiming for a cost of no more than £16,000.

The final design was developed alongside the chassis team, to ensure a perfect fit. This was achieved through a cohesive design process. The geometric model was analysed through the kinematic analysis and then the dynamic analysis. The components were designed and analysed using the calculations. This design process is cyclic and had to also work alongside the chassis team to ensure assembly will be feasible.