The Design, Fabrication, and Performance of the East African Trial Leveraged Freedom Chair

The Leveraged Freedom Chair (LFC) is a lever-powered, wheelchair-based mobility aid designed specifically for use in the developing world. Its drivetrain optimally converts upper body power in a wide range of terrains, giving the LFC operational capabilities that extend beyond those of currently available mobility products. In this work we present the design and analysis process used to create an LFC for trial in East Africa. All of the moving parts in the LFC are made from bicycle components and the entire chair can be fabricated without any machining processes. This allows the LFC to be manufactured for the same price as existing mobility aids and repaired anywhere in the developing world. Eight prototypes were produced in Kenya during August 2009, with six distributed to mobility aid users throughout East Africa. After four months of testing, the subject-averaged propulsion efficiency using the LFC was 20% greater than that of existing mobility products. Performance results and feedback from the subjects indicate that the LFC is ideally suited for active wheelchair users who require the seating and postural support of a wheelchair, and who desire to travel on rough terrain under their own power. Test subjects’ input was also used to codify future improvements to the LFC design, including narrowing the stance of the chair and lowering the rider’s center of gravity.