SFSU ME Senior Project- Adjustable CG for Convertible Handcycle


This is the project website for the Adjustable Center of Gravity for Convertible Handcycle Senior Mechanical Engineering design project by Nicholas Celeste, Darren Guertin, and Lovy Saing at San Francisco State University from Spring 2012 - Fall 2012.

The links to the left chronicle the project, and all documentation, design meeting notes, and useful links can be found to help future students exploring a similar project.

Project Description:

       A device that adjusts the location of the center of gravity (CG) of a wheelchair user relative to the drive wheels of a hand-powered wheelchair is proposed. This device will attach to the frame of an existing wheelchair and allow the user to manually shift a wheelchair’s rear axle position relative to the user’s CG while sitting in the chair and without the use of any tools. By moving the rear axle relative to the user’s CG, traction at the drive wheels will increase, and this will improve the functionality of a removable handcycle frontend because the front drive wheel will be less prone to slipping on an inclined plane. Past efforts in handcycle technology have been limited by the inability of typical wheelchairs to adjust CG location in a quick and simple manner. Two methods of achieving CG adjustability were explored, and an adjustable axle position relative to the CG was determined to be the most practical and safest method. Detail of the design is documented, as well as results of prototype testing. The completed device, in the rear most position, triples the traction at the front wheel, increases static and directional stability, but increases the potential for tipping when turning on a declining plane. This project was constructed, tested, and completed within a budget of $630 and delivered at the end of the Fall 2012 semester.