Graduation Year

2007

Document Type

Thesis

Degree

M.S.M.E.

Degree Granting Department

Mechanical Engineering

Major Professor

Stuart Wilkinson, Ph.D.

Keywords

Disabled mobility, Modified wheel, Shock reduction, Vibration reduction, Finite element analysis

Abstract

The objective of this study was to design and build an after-market suspension for the rear wheels of a manual wheelchair. Suspension for wheelchairs is important because it has been reported that the International Organization for Standards' requirements for vibration loads on wheelchair users (ISO 2631-1), are not meet by today's standard wheelchairs. Today's wheelchairs need to be able to absorb everyday shock loads, thereby minimizing the energy transmitted to the user. The chosen design is based around the concept of adding shock reduction material between the hub of the wheel, and the axel bolt that connects the wheel to the frame of the chair. The approach taken was to design a suspension system that resides between an oversized wheel bearing, and the axle. To do this, ball-race bearings with an inner diameter of 4" were chosen, and polyurethane rubber was used as the shock absorbing material. Pro-Mechanica, a finite element analysis program, was used to analyze the suspension system. Since the most common camber/tilt for wheelchair wheels is three degrees from the vertical, the anticipated loads were applied to the wheel at this angle. A prototype of the suspension system was constructed to verify that the design would work, but no tests were performed on it. This analysis showed that the suspension system should not fail when subjected to 10 times the static load. This load was considered large enough to encompass the forces that a wheelchair chair wheel is typically subjected to. There is room for further work in the area of weight reduction, and in the use of the suspension system on steeper wheel cambers.

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