Design and Analytical Calculations of Double Wishbone for Formula Student Race Car

The functional objective of the suspension system is to provide relative motion between the sprung and the unsprung mass. This is achieved by a spring to absorb the shocks and some kinematic linkages holding them together with particular degrees of freedom. Further for better handling the kinematics of the system is designed and optimized. This research focuses on the simulation, design, and analytical calculations of the kinematical linkage called A-arm. The double-wishbone suspension geometry was analyzed in Lotus Shark software to procure the most appropriate location of the hardpoints. A-arm was modeled in CATIA V5, Autodesk Fusion 360, and analyzed in ANSYS 16.0. Software results are correlated with the analytical calculations to obtain a feasible solution. Keywords—Double wishbone, A-arm, thickness calculation, rod end selection, vehicle dynamics, threaded joints, etc.


I. INTRODUCTION
The FS car's suspension controls the angle, position, and velocity of each wheel to maintain a high value of mechanical grip while transmitting the forces generated by tires to the chassis. A reliable method to determine the forces produced by the road loads in suspension members opted. In this paper, a detailed analytical calculation was explained for deciding the A-arm diameter using a set of calculations. The component is designed to be costeffective, durable, and lightweight. As the double-wishbone undergoes tension and compression forces, the yield and buckling need to be calculated, followed by the threaded joints calculation for the rod ends as the force being transmitted through these to the chassis. Fig1. Double wishbone II. PROBLEM STATEMENT The double-wishbone suspension system is independent. This design allows the race car engineers to control the wheel's motion throughout suspension travel, controlling the parameters such as camber angle, caster angle, toe, roll center height, and scrub radius.
They are a force transmitting and kinematic part, so dynamic stability is the most crucial factor. Designing by using lightweight material along with it being cost-efficient is the recent discovery many teams are trying to develop. In the era of upgrading trends, many teams are trying to evolve in a world full of research related to advanced materials.
In this fast-changing and technologically developed world, there is much-advanced software in use, but all that software is programmed on the necessary calculations. To correlate those results with calculations and further substantiate those software results, we need analytical calculation. Because sometimes that software is constrained to some limits. The paper explains the method to find the thickness of the a-arm by pen and paper calculation. These calculations require critical skill, and also, they are an essential set for sound stress engineers in the automobile industry.
Some teams want better design irrespective of cost, and some want a mediocre design with the economical product. But many teams are trying to get the intermediate between them, so to improve this, we need our work to be well developed from all angles and aspects. Hence analytical form is considered to be more cogent. The necessary steps in designing a vehicle's suspension are:

Fig2. Suspension Assembly
• Selection of the suspension type to be employed; • Selection of the wheels; • Establish the vehicle's dimensions: wheelbase and track width(s); • Model the suspension geometry; • Designing components. VII Load Transfer The inertia of a mass is its resistance to change its state. For the change of state of a body, it must experience acceleration in its motion direction. Acceleration, braking, or cornering is nothing but the change of state of the vehicle, which offers resistance for a while and results in load transfer in a direction opposite to the force causing the change. No doubt, this load transfer persists for a short duration of time, but its impact on the car's performance is much more crucial.

Parameter
Value ( Considering this as the inner diameter, the outer diameter was calculated by the following procedure:  The purpose of this paper was to find the diameter of the double-wishbone by analytical calculations. The force is calculated using basic concepts. This paper gives a clear idea of how the forces are taken into consideration. Material is selected based upon calculated forces. Double-wishbone is designed using suspension points and dynamic force applied considering the factor of safety. Design is validated by using Ansys 16.0 software. This design is fabricated and tested in the Formula Student race car in all dynamic conditions. No failure occurred at the time of testing, it can be concluded that forces calculations and design are up to the mark.

XI ACKNOWLEDGMENT
We would also like to thank Team Redline Racing for successfully designing and manufacturing the Formula Student race car.