thesisposted on 20.12.2018, 00:00 by David Tobin
Manual wheelchair users traditionally suffer from an increased risk of chronic shoulder injury and the inability to travel quickly or uphill independently. Beginning as a senior design project in fall of 2016, Wyoming Wheels is a geared, lever-action, manual wheelchair system designed to mitigate these challenges. For the 2017-2018 school year, the goal of the project was to create a functional prototype by optimizing the previous year's project. Specifically, the weight and noise output needed to be decreased, and the shifting, braking, and overall ergonomics of the chair needed to be improved. The total weight of the chair was reduced by 40% by replacing the original steel gears and handles with Delrin® plastic and lightweight aluminum. By combining a single planetary gear system with a 3-speed internally geared hub, the gearing and shifting systems were simplified and the sound output was reduced to that of a bicycle. A two-way pawl was designed to engage the planetary gear system as a clutch such that the gears are only driven when the lever action handles are engaged. This creates a default neutral setting, allowing the user to operate the chair normally when the handles are not engaged. The shifting interface was simplified by implementing a standard bicycle twisting shifter. An internal drum-brake system was added for improved stopping power and increased safety. The handle was re-designed to incorporate the twist shifter, brake lever, and pawl-clutch lever in a useful and ergonomic arrangement. This prototype was ultimately successful in meeting the desired objectives.