Design and Development of Carbon Fibre Wheel Shells and Wishbones for a Formula Student Racecar - Daniel Crowe 2019
Monash Motorsport Final Year Thesis Collection
The Final Year Thesis, is a technical engineering assignment undertaken by students of Monash University. Monash Motorsport team members often choose to conduct this assignment in conjunction with the team.
These theses have been the cornerstone for much of the team’s success. The purpose of the team releasing the Monash Motorsport Final Year Thesis Collection is to share knowledge and foster progress in the Formula Student and Formula-SAE community.
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Carbon fibre wheel shells on Monash Motorsport racecar
Summary
This project sets out to design carbon fibre wheel shells and wishbones for the 2019 Monash Motorsport racecars. By utilising composite materials, these structural suspension components can be designed lighter, stiffer and more reliable than the aluminium and steel counterparts. This project undertakes advanced composite simulation using ANSYS Composite PrepPost. 3D printed titanium structural members were investigated for use in the carbon fibre wishbone assembly. Carbon fibre wishbone links were mechanically tested to validate the design and manufacturing methods. Overall, the carbon fibre wheel shells saved 3760 g and the carbon fibre wishbones saved 1717 g across each car.
Introduction
The Formula Student competition is the world’s largest student engineering design competition, where the aim is to design, manufacture, test and compete with an open wheel racecar across a series of events. Across the 2018 – 2019 period, Monash Motorsport has competed in the Formula Student UK, Formula Student Austria, Formula Student Germany, Formula SAE Australasia and Formula Student Sydney Competitions.
Each competition consists of a series of both dynamic (on-track) and static (off-track) events. The results from each event are calculated into points, with a maximum of 1000 points available at competition. Monash Motorsport utilizes a simple point-mass simulator to predict the effect that major concept changes, such as mass and power, have on the points scored at competition. The results of this simulator were used to drive the early design decisions of the 2019 combustion and electric cars – M19-C and M19-E. Based on the results of extensive tyre testing performed at the end of 2018, Monash Motorsport will move from the 10-inch Hoosier R25b tyres to the 13-inch Goodyear D2704 tyres. Currently, the tyres mount to a three-piece wheel assembly, consisting of two aluminium wheel shells and an aluminium wheel centre that mounts to the hub.
The 2019 suspension geometry consists of a double wishbone design, previously manufactured from AISI 4130 alloy steel. By utilizing carbon fibre, these structural suspension components can be designed lighter, stiffer and stronger than previous aluminium and steel designs, increasing the performance of Monash Motorsport’s 2019 Formula Student racecars.
The purpose of this project will be to:
• Design carbon fibre wheel shells to mount the 13-inch Goodyear tyres.
• To develop a manufacturing process encompassing mould design, the carbon fibre layup procedure and post-machining methods that can be performed in-house.
• Design carbon fibre wishbones utilizing 3D printed titanium bearing cups.
• Validate the adhesive bonding by mechanically testing the wishbone links in tension, compression and fatigue.
Conclusion
Carbon fibre wheel shells were designed with a minimum safety factor of 1.14. The final mass of the carbon wheel shells was 4280 g, saving 3760 g compared to the aluminium wheel shells. This corresponds to 3.0 points gained at the competition for M19-E and 3.8 points gained for M19-C. The number of carbon fibre plies varies from 10 to 16 plies. The layup shapes, orientation and sequence is detailed in this report. The simulated camber compliance is 0.16 °/g for the front and 0.20 ° /g. The mass of the carbon fibre wishbones and links design was measured at 3137 g, saving 1717 g compared to the steel wishbones. This corresponds to 1.9 points gained at the competition for M19-E and 2.3 points gained for M19-C as calculated by the points simulator. The wishbone links and adhesive bonding techniques used in the design and manufacture were mechanically validated in tension, compression, fatigue and buckling. The simulated camber compliance is 0.03°/g at the front and 0.04°/g at the rear. Thank you to CSIRO’s Lab 22 and MCAM for providing Monash Motorsport with titanium 3D printing services to make these designs possible.