2024-2025 SAE Baja Knuckles

Last year I was tasked with designing the knuckles for my school’s SAE Baja team. Previous years had used heavy welded “box-style” knuckles made from steel tubing. We previously failed to manufacture good parts as weld distortion often shifted the control-arm mounting points so they didn’t line up with the intended suspension geometry. They were also heavy, at roughly 10 lb per knuckle, and all the pickup points for the upper and lower A-arms and the steering tie-rod used heim joints.

My redesigned knuckles replaced the welded box construction with a machined-aluminum design. I performed ANSYS static-structural simulations for three representative load cases (vertical bump, side-load from steering, and combined braking/landing) and targeted a conservative design. The final geometry achieved a minimum safety factor of about 2.0 across all cases comfortably above our 1.5 requirement while still keeping mass low.

The new design weighed only about 4 lb per knuckle, cutting unsprung weight by roughly 60 % compared to the old design and improving suspension response.

A key focus was design for manufacturability. The knuckle was modeled to be machined primarily on a 3-axis mill, with one 4th-axis operation for the bearing bore. I designed fillets, tool-accessible pockets, and standardized hole sizes to avoid exotic tooling.

The final knuckles were not only much lighter and stronger, but also more dimensionally consistent, ensuring the suspension pickup points matched the CAD-defined geometry. The improved manufacturability simplified both fabrication and inspection and helped the team build a more predictable, better-handling Baja car.