Improved Bike Crank

For this project, my team set out to design a child’s bicycle crank that would intentionally break at a specific deceleration force (12 N) to help prevent leg injuries. We explored three initial design concepts: carving out material from a slab, connecting blocks with diagonal supports, and using a lofted shape inspired by mountain bike cranks. After evaluating each concept’s feasibility with acrylic and PLA manufacturing constraints, we chose a design that carved out material from the center to reduce weight and control the break point under torsional loading conditions.

Through multiple rounds of hand calculations, FEA simulations, and physical prototyping, we developed a layered “acrylic sandwich” crank with inner cutouts meant to ensure failure occurred away from the mounting points. Unfortunately, due to differences between the real loading conditions and the FEA setup, failure still occurred at the mount on testing day. We would have appreciated a bit more time for testing, but it was still a valuable experience in designing for manufacturing and mass minimization.

Our report is linked here:

https://drive.google.com/file/d/1Z_YiAGMRvzfOiApskyTRoZo2qLcUaOYg/view?usp=sharing