Solar Car Aero Series - Wheel Covers
Solar Car Aero Series:
Beginner guide to Solar Car CFD (WIP)
Wheel covers (WIP)
A winning car (WIP)
Crosswinds and how to not flip your car (WIP)
Solar Car Wheels
Walking around Victoria Square after a race and looking at each of the Challenger cars, it’s very easy to sort the lower teams from the top of the pack - just look at the wheels.
Here’s a team I’m allowed to (lovingly) make fun of, my alma mater AUSRT in 2023.
And here are some good teams, Leuven in 2023 and Delft in 2019:
The AUSRT wheel is about as bad as it gets for drag, completely uncovered wheel spokes spinning around in a wide open fairing (AUSRT definitely weren’t the only team with wheels like this). The result is additional rolling resistance from aerodynamic damping inside the fairing, as well as a whole bunch of dirty flow making its way out through the wheel cut-outs and producing messy flow along the bottom of the fairing.
- Uncovered spokes are bad
- A wheel with a plate to cover up the spokes is okay
- A clamshell which encloses the spinning wheel is ideal, combined with something (foam, spandex, etc) which closes up the gap between the wheel and the fairing cut-out.
All of the top teams use a design like this, and for good reason.
The drag penalty of an uncovered spoked rim is huge.
Why then do the bottom teams often not design their wheels this way? My impression is that the teams at the bottom of the pack:
- underestimate the aero impact of uncovered wheels
- Are already struggling to get the car designed and built and have to prioritise
- Struggle to make a clamshell which doesn’t rub on the wheels (the fit on that Delft wheel above is unreal…)
In some senses, there’s not much more to discuss - there’s no doubt as to what the optimal design is, the top teams figured it out long ago. However, I do think that there’s still some small performance gains to be found here, and I want to drive home to the teams towards the back of the pack just how important the wheels are.
Work in progress: Wheel CFD Case