Design and Validation of the Unsprung Masses of a Formula SAE vehicle

This work describes the development process of the unsprung components of a formula-styled race car that participated in the 2018 Formula SAE Italy and Formula Student Spain competitions representing the Politecnico di Torino. The report is mostly focused on the mechanical design of structural elements, considering performance and packaging constraints and the ease of manufacturing and assembling (DFMA). A comprehensive description of the design process is included, highlighting the integration between the different disciplines and technical divisions of the PoliTo Racing Team (Squadra Corse Polito), with a focus on the wheel uprights as the element in which converge the transmission, cooling, suspension and brake systems. Detailed 3D CAD models were used to achieve the integration between parts and as input for structural FEM analyses before the definitive technical specification. Next, the production and validation of the designed parts are addressed. The whole process is compared to the standard V-model approach for complex project development including practical considerations. Particular attention is paid to the study of the wheel uprights using Altair Optistruct to realize linear static structural analyses. The radial stiffness data of the wheel bearings was used to implement the constraints for the stress analyses, avoiding the use of rigid elements for eliminating the motion of the bearing seats. This allowed obtaining a more accurate assessment of the stresses and compliance compared to the traditionally used boundary conditions that artificially stiffen the analyzed parts. In the case of the braking system, an analytical model was used to calculate the braking forces and estimate the brake rotor temperatures in exercise. This was followed by a thermo-mechanical study to define the final geometry of the brake rotors. Track tests on both the 2017 and 2018 formula student cars allowed to collect data about the temperatures experienced by the rotors and calipers to correct the initial models for future development. In the end, the manufacturing and assembly processes are described, followed by an assessment of the performance achieved. A failure of the brake discs after the first competition starting from one of the laser-cut holes revealed that this process should be avoided if high precision and good surface finish are not guaranteed. Finally, some recommendations for future development are done based on the observations.