Transmission Cooling System - Bruin Racing Baja SAE
What?
In UCLA Baja's 2022 vehicle transmission, power is transferred from a set of drive sheaves to a set of driven sheaves via a belt. Keeping the transmission cool is critical to prevent a dissimilar-material press fit in the transmission from failing, and to avoid aluminum and belt material degradation.
Given a recent rules change that prevented firewall cutouts and air intakes that extended past the car's roll hoop, we chose active cooling as a means of keeping transmission temperatures under control. I worked with one other engineer to design, simulate, and manufacture this new system.
How?
Assuming all drivetrain inefficiency went to heat generation, SolidWorks Flow Simulation was used to model airflow within the transmission cover and transmission temperature trends. Given the transmission's unknown resistance to flow, pump best practices dictate prioritizing pressure buildup over outright air flowrate. As a result, a centrifugal blower design (which is good at both generating pressure and moving air) was selected.
SolidWorks and its Flow Simulation tool were used to design and optimize the volute blower casing and impeller, and prototype fit-check parts were FDM 3D printed out of PLA. Finalized parts were SLS 3D printed out of nylon given the material's low brittleness, high glass transistion temperature, and good surface finish.
Results
When tested on a stationary car, the blower was able to build enough pressure to push air through the transmission cover at the flowrate required for cooling as determined through simulation. Unfortunately, last-minute motor controller issues prevented the cooling system from being run at competition -- an important lesson in leaving more than enough time to test in real-world conditions. On the upside, the system was very well received by competition design judges.
SolidWorks CFD Walkthrough
For future student engineers to build off of our work, my teammate and I put together a tech talk on using SolidWorks Flow Simulation to analyze rotating components. Feel free to look through our slides below!