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Published byMildred Day Modified over 9 years ago
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GROUP NINE Cross-Slope Compensation for Wheelchairs Alexander A. Abraham David Dar Marc C. Moore Advisor: Dr. Mark Richter
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The Problem ADA regulations specify no more than a 1.1º cross slope Not followed for construction purposes or in private environments Currently wheelchairs do not have a mechanism to prevent involuntary veering on cross slopes Subjects are forced to apply more torque on one wheel to maintain straightforward motion
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Design Criteria Add-on feature to current wheelchairs Cost-friendly Aesthetically appealing Light-weight Mechanically simple Robust, durable Must withstand 7.3 N*m of downhill torque
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The Solution A mechanism that restricts rotational movement of a front wheel Forces wheelchair to travel in a single direction without deviation Applied only when the subject deems it necessary
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Previous Design Considered Preliminary model of the caster wheel Caster features two surfaces separated by ball bearings Upper contingent smaller than lower contingent
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Previous Design Considered Ring with teeth along the radial and axial axes, which surrounds central post By default, the spring- loaded ring is suspended above the lower surface When activated, ring snaps down and locks with lower plate
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New Design One pin locking two plates together Spring-loaded Clean appearance Mechanically simple Add-on easy
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Concerns Solves problem Mechanism inadvertently activating Reliability - Mean Time Between Failure (MTBF) Ease of use Warning of hazards
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Work Completed Researched ADA regulations Researched wheelchair mechanics (lab visits, journal publications, etc.) Constructed initial 3-D model Consulted several times with Dr. Mark Richter (Vanderbilt University, MAX-Mobility) Submitted NCIIA proposal Established project website Dismissed initial design
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Nixed Work Developing caster model with radial and axial teeth Completing CAD model ourselves
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Current Work Completing mock-up model for new design Welding pin tubing to caster Attaching bike cables to pin Consulting with expert machinist Determining appropriate spring constant for loading spring Determining optimal composition of heat-treated torsional spring pin of final model
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Future Work Manufacture prototype from finished CAD model Analyze design effectiveness Re-design model and make adjustments accordingly Implement device alterations
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