Team Members: Oyundari Altansukh, Kurtis Barth, Samantha Campbell, and Caroline Swanson
Faculty Advisor: Dr. Lily Laiho
QL+ Program Manager: Vanessa Salas
QL+ engineering students from Cal Poly tackled the Surf Leg Challenge. The QL+ Challenger is Operation Surf, a program that teaches veterans how to surf. Current prosthetics do not allow the user to squat due to stiff ankle design. The students were challenged to create a transtibial prosthetic that provides ankle flexibility to improve ankle mobility, while still being lightweight, adaptable, and water-proof.
The team spent three quarters researching, designing, fabricating, and testing a prototype that would fulfill the Challenge's requirements. Based on the biomechanics of surfing and customer requirements, they designed a transtibial prosthetic leg with four components: ankle, foot, post, and adapter. Their design uses rubber to provide a wide range of ankle movement. It also has a carbon fiber foot for flexing and balancing. It has an adjustable post and universal adapter so that various participants can use the product.
The team analyzed surfing biomechanics and multiple computer models. They chose a final design using a selection process that analyzes the strengths and weaknesses of each design. Using finite element analysis, the team chose materials that would meet the engineering specifications of the prosthetic leg and weights of the participants. In order to meet the weight range of users, they tested four different rubber durometers.
The foot was constructed using carbon fiber and manufactured in the composite lab. The foot has a high stiffness but allows for torsion and high-frequency damping. All the metal parts were made using Aluminum 6061. The metal shell was CNC lathed by Cal Poly and finished by the team on the mill. The posts were lathed by the team, and the baseplate and cross were cut with the water-jet. The carbon fiber was bonded to the metal using a 2 part flex epoxy. The cross was joined to the lower post through welding.
All materials were corrosion tested for one month and none of the materials showed significant corrosion effects. The foot was tested by a volunteer through QL+. She was able to confirm that the ankle provided the necessary mobility, however, she gave insight into adjusting the foot size and shape so that walking can be done more naturally. Through iterating, fabrication, error, and dedication, the team produced a transtibial prosthetic that could fit anyone from a teenager to an ex-marine with extreme mobility and flexibility.