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Design, manufacture, and test the gearbox, including gearbox housing and shafts, for the Northwestern's BAJA Society of Automotive Engineers (SAE) car.


A new lightweight and easy-to-assemble gearbox with improved torque, maximum velocity, and sealing.

Me about to race our car at the national endurance race.



​Analyze prior gearbox designs

Iterative gearbox calculations​​

Withstand tough driving conditions

Gearbox housing and shaft design

CAD (Gears, Shafts, Gearbox Housing)

Finite element analysis (Gears, Shafts, Gearbox Housing)

Writing NX CAM for gearbox housing

CNC machining gearbox housing (3-axis HAAS mini mill)

Grinding and refinishing gears

Turning custom titanium bearing race

Gearbox assembly and testing

Testing at BAJA SAE competition

Design Process


Design Parameters

The initial process began with analyzing prior gearbox designs and performance. Design goals were identified as the following:

  • Minimizing weight

  • Increasing torque

  • Increasing maximum velocity

  • Withstanding tough driving conditions

  • Simplify assembly and disassembly

Next, iterative gearbox calculations were performed to test the best combination of the following inputs:

  • Gearbox ratios

  • Gearbox geometry

  • Gearbox materials 

  • Shaft geometry 

Once the design parameters were solidified, Solidworks CAD models were created for the full gearbox assembly. 


FEA and Manufacturing

Following the CAD model design, finite element analysis was completed on the gears, shafts, and gearbox housing to test if the assembly and components could withstand the expected driving forces. Once the design was finalized, the following manufacturing steps were completed:

  • Wrote NX CAM for gearbox housing

  • Machined gearbox on 3-axis HAAS mini mill

  • Ground and refinished gears

  • Turned custom titanium bearing race

  • Turned titanium shafts (completed with help from teammates)


Final Design and Testing

The final gearbox allowed for much easier and faster assembly than prior designs which is especially important in BAJA races where quick work on the car is often required mid-race. The gearbox also successfully improved torque, maximum velocity, and sealing while minimizing weight. In addition, changing the shaft material from steel to titanium improved its strength-to-weight ratio. The gearbox withstood harsh conditions at the national race during dynamic races, including a sled-pull, and the four-hour endurance race without any failures, lasting over two times longer than the prior design.


Four years later, the gearbox is still running!

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