Scope
Established the analytical and architectural framework for the next-generation electric gearbox used in the Wisconsin Racing 225e Formula SAE vehicle. The team previously relied on a legacy custom gearbox design with minimal iteration; this project defined a data-driven redesign process to optimize ratio selection, durability, mass, and packaging constraints for the new electric powertrain.
The gearbox was wheel-integrated, requiring tight coordination between powertrain, vehicle dynamics, braking, and suspension subsystems.
Gear Design
Worked directly with the vehicle dynamics and lap time simulation teams to determine the optimal output gear ratio target based on acceleration performance, duty cycle expectations, and overall vehicle efficiency.
Using a target ratio of 11.8:1 and defined load cases, I:
- Applied ISO 6336 standards for gear strength and durability calculations
- Selected appropriate gear materials and heat treatment processes in collaboration with the gear-cutting sponsor
- Incorporated sponsor-driven module sizing constraints into the design space
Leveraging KISSsoft, I generated and evaluated 1000+ gear geometries to converge on an optimized configuration.
The down-selection process incorporated multiple system-level parameters, including:
- Flank and root life
- Maximum system outer diameter (packaging constraint)
- Hunting ratio
- Maximum specific sliding
- Tooth profile shift values
The final selected geometry achieved an output ratio of 11.76:1 while satisfying durability, packaging, and manufacturability constraints.
Housing & Packaging Design
The gearbox housing operated within significant spatial and structural constraints, as it was integrated inside the wheel shell. Key design requirements included:
- Direct wheel coupling
- Suspension arm mounting integration
- Sealing of internal geartrain components
- Proper interface with braking system components
- Minimization of unsprung mass
The housing architecture balanced structural rigidity with weight optimization while maintaining concentricity and bearing alignment requirements critical to gear life.
Multi-Level Structural & System Analysis
A layered validation approach was used to ensure performance and reliability:
Component-Level Analysis:
- Beam bending calculations to size planet pins while minimizing mass and deflection
- Wheel bearing sizing using load outputs from the vehicle lap time simulator
- Individual component strength validation using ANSYS
System-Level Analysis:
- Developed a full geartrain model in MASTA to evaluate system deflection and its impact on gear meshing performance and life
- Analyzed gear alignment sensitivity and load distribution across operating conditions
This multi-scale analysis methodology ensured durability targets were achieved without over-designing the system.
Summary
The analytical framework and optimized gearbox architecture established through this project were implemented in the 225e vehicle.
The next-generation drivetrain contributed to a significant reduction in vehicle mass and improved system performance relative to the legacy design.
This project demonstrated the value of integrating simulation-driven ratio targeting, standards-based durability design, and system-level deflection modeling to produce a robust and optimized electric drivetrain solution.