Project Number: HXA 1503 Rehabilitative Adult Tricycle A Major Qualifying Project Report Submitted to the Faculty of the WORCESTER POLYTECHNIC INSTITUTE in partial fulfillment of the requirements for the Degree of Bachelor of Science in Mechanical Engineering by Eric Correia Jaime Espinola James Gruenbaum John Papa Date: April 28, 2016 Advisors: Professor Holly Ault Professor Allen Hoffman This report represents the work of WPI undergraduate students. It has been submitted to the faculty as evidence of completion of a degree requirement. WPI publishes these reports on its website without editorial or peer review. Abstract Each year, 800,000 people experience a stroke in the United States, and many develop hemiparesis, a weakness occurring on one side of the body. Exercise is proven to be helpful in recovery from stroke. The goal of this project was to develop a human-powered device that can aid in recovery from a stroke, while also serving a recreational purpose. This project resulted in the creation of a tricycle, which stores the pedaling energy of the strong leg with a spring in order to assist the weak leg in pedaling. Testing with force plates demonstrated that the force required to pedal the weak side with the highest spring constant was 49% lower than the baseline with no spring. The tricycle was a good proof of concept and with further modifications could be a viable tricycle in the future. i Acknowledgements The following people and organizations greatly assisted in the completion of this project, and we would like to thank them for their support: Scott Guzman: Scott is a WPI alumnus. He provided us with feedback about the feasibility of many aspects of our design and provided us with advice about how to improve the design. In addition, Scott performed all of the welding for the build, including the seat extender, frame, and the spring sprocket support plate. Scott’s welding was very helpful, as none of the group members had prior experience welding. Burt Seger: Burt owns a small machine shop in Jefferson, MA. His machining work greatly expedited the manufacturing process. In just two brief visits, Burt was able to machine both the spring sprocket plate and the handlebar extenders to our desired specifications. In addition, Burt was very hospitable, allowing us to run some of his machines, and giving us advice to assist us in our future careers. Worcester Earn-a-Bike: This organization allows volunteers to earn their own bike for free in exchange for performing work for the shop. The staff of Earn-a-Bike are very knowledgeable about bikes, and helped us install the brakes and sprockets to the tricycle. In addition, they sold us many of the components of our design for a reasonable price, including the BMX bike we used as part of the frame, and the cranksets we used to connect the spring sprocket mechanism. ii Authorship Abstract ...................................................................................................................................................... EC Introduction ................................................................................................................................................ EC Literature Review .................................................................................................................................... ALL Strokes .................................................................................................................................................... JE Goals for Rehabilitation .......................................................................................................................... JG Benefits of Recreational Therapy .................................................................................................... JE, EC Existing Therapies and Devices ........................................................................................................ JE, JP Mechanics Involved in Cycling ............................................................................................................. EC Mechanisms ............................................................................................................................... EC, JP, JG Goal Statement ............................................................................................................................................ JE Design Specifications ........................................................................................................................... JE, EC Power Adjustability ......................................................................................................................... JE, EC Ergonomics ...................................................................................................................................... JE, EC Cost .................................................................................................................................................. JE, EC Manufacturability ............................................................................................................................. JE, EC Safety ............................................................................................................................................... JE, EC Range of Motion .............................................................................................................................. JE, EC User Requirements ........................................................................................................................... JE, EC Stability ............................................................................................................................................ JE, EC Preliminary Design Concepts.................................................................................................................. ALL Design 1: Piston ..................................................................................................................................... EC Design 2: Motor ..................................................................................................................................... EC Design 3: Planetary Gear ........................................................................................................................ JG Design 4: Continuously Variable Transmission (CVT) .......................................................................... JP Design 5: Push Pedal ........................................................................................................................ JG, JE Design 6: Spring Resistance ............................................................................................................. JG, JE Analysis of Initial Design Concepts........................................................................................................ ALL Power Mechanisms ................................................................................................................................. JE Remaining Tricycle Components............................................................................................................ JE Tipping Analysis ..................................................................................................................................... JP Selection of Best Concepts ......................................................................................................................... JE Power Mechanism ................................................................................................................................... JE Remaining Design Components ............................................................................................................. JE Selection of Final Design ........................................................................................................................ ALL Propulsive Force Calculations ................................................................................................................ JG Performance Analysis ............................................................................................................................. JG Input Force Comparisons .................................................................................................................. JG, JE Mechanism Bounding Conditions .................................................................................................... EC, JP Size and Complexity Analysis ............................................................................................................... EC Decision Matrix ...................................................................................................................................... JE Final Design ................................................................................................................................................ JG iii Frame Selection and Modification .......................................................................................................... JG Spring Mechanism and Support Structure .............................................................................................. JG Spring ...................................................................................................................................................... JG Design Analysis ...................................................................................................................................