DESIGN OF A SUSPENSION SYSTEM FOR A FORMULA ONE STUDENT RACE CAR

ABSTRACT

The formula one student race car design project is an ongoing project that seeks to provide a platform that will improve the learning experience of the student engineers. This builds the engineering design and project management skills of the student engineers involved in the development of the designs. Since conception three years ago, areas tackled have included the transmission, steering and chassis designs of the race car prototype.

This year saw the design and simulation of the suspension system of the FSAE race car. By the fact that the vehicle is performance oriented, the suspension design will ultimately play a great part in the overall vehicle performance, and as such, great insight was required during the design stage. The suspension system plays a vital role in transmitting power developed by the engine to the wheels, doing so as efficiently as possible, while damping out any road inconsistencies that may be present. This will determine the handling and the comfort of the vehicle once its manufacture has taken place.

Suspension systems come in various sizes and designs, each tailored to suit the vehicle for which it is being designed. This variants include the MacPherson strut; majorly used in passenger vehicles due to the simple and compact design that gives great comfort at an affordable cost, Leaf springs; used in heavy duty applications due to their robust nature, Double Wishbone; gives a better performance characteristics over the MacPherson strut and Leaf Spring suspension systems and as such they find use in most performance oriented applications including racing. The Multi-Link suspension system is a recent development of the double wishbone that gives a greater degree of adjustment.

For the design, the double wishbone variant with unequal arms was selected as it gave the best performance characteristics with the limited space available. It includes a heave spring, push rod mechanism, and a coil-over-oil spring and damper assembly that gave the required damping and spring rate for both the front and rear suspension systems.

The design heavily relied on the motion analysis of the links to describe how the suspension travel will affect the different suspension characteristics and how any adjustment will affect these characteristics, as well as carrying out a finite element analysis to determine the forces acting on all members and therefore determine all possible modes of failure [1] and design against them in an efficient way. This was done by using Autodesk Inventor’s dynamic Simulation and Stress Analysis.

This helped us come up with a suitable design that met all design considerations put forward. The static camber designed into the system was 3.1357° and 0.2588° for the front and rear wheels respectively while the minimum factor of safety was 2.0895 for the front suspension and 6.1958 for the rear suspension. The large value of the factor of safety was due to the fact that the links were designed against strain so as to maintain the integrity of the kinematics involved.