P 08002: Raising the Bars Ryan Hellems Justin Knowles Justin Vowles Jeff Osborne Jessica Stalker Dr. B. De. Bartolo Project Lead ME ME ME ISE Project Advisor Customer: Nazareth Physical Therapy Clinic, JJ Mowder Sponsor: This material is based upon work supported by the National Science Foundation under Award No. BES 0527358. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author and do not necessarily reflect the views of the National Science Foundation
Project Rationale • The physical therapy clinic at Nazareth uses parallel bars to aid in walking rehabilitation for stroke and other neurological patients. • Peg and pin system is difficult, time consuming, and inaccurate when adjusted. • Redesign needs to simplify raising and lowering of parallel bars, and insuring they remain level.
Key high level customer needs • Must be safe – – – • Must be easy to use – – – • Support patient load without drop (350 lbs) Stable upright supports No pinch points or sharp edges No trip or snag hazards Accurate height adjustment <9 Lbs force to raise Reasonable time to adjust (90 s) Bars remain level along full length Reliable for 5 years of service
Current System
Selected Concept Existing Parallel Bars Hand Crank Tower Lifting System Drive Shaft w/cover
Design Details – Lifting System • Three posts tied-in series by singular drive shaft • 1: 1 perpendicular miter gears transmit rotation from drive shaft to ACME rod • 5/8 -8 ACME Rod supports vertical loads, transmits weight to outer post. • ACME nut welded to inner post rides up/down rotating threaded rod
Design Details – Hand Crank Tower • 4: 1 gear ratio for belt drive provides 0. 5 inch lift per revolution • Ergonomically located hand crank, easy to turn • Removable handle prevents incidental adjustment
Testing & Lessons Learned ACME Nut Alignment Test • Results: Nuts not square, rod contacts shaft wall – Corners of the acme nut were turned down from the as-built to a standard sized hole. – Half-part chamfer was added to keep the part square to the shaft as it was welded. Miter Gear Alignment Test • Results: Too much movement of gears, bad mesh – Thrust plates redesigned to tighten some tolerances – Snap rings added to prevent any gear travel – Split ring collars added to restrict motion of drive shaft
Testing & Lessons Learned Ease of Installation Check • Results: Uneven floor, drive shafts not straight, need to calibrate towers to ensure level – Added universal joints with slot for drive shaft length and set screws for angular adjustment – Changed bearing design Full Extension Deflection Test • Results: Current system better than redesigned at max height – Limit functional max height to 42” – Powder coat inner post – Proposed plastic shim at top of outer post
Budget Lifting System - $310. 03 Drive Shaft System - $371. 30 Hand Crank Tower – $327. 04 Powder Coating - $235. 00 Misc. Hardware - $80. 00 Shipping & Handling – $132. 37 Total Cost - $1, 455. 74
Project Evaluation Strengths – Easy to use • central location to adjust both sides; saves walking – Easy to adjust • Low torque requirement - ergonomics – Ability to revert to previous set of parallel bars if design is unacceptable or customer is dissatisfied – 16 gauge steel cover to protect against rotating drive shaft • can withstand 250 individual falling or jumping on it – Professional looking – powder coating won’t rust over time
Project Evaluation Weaknesses – Lack of safety cover for hand crank tower • exposed belt and sprockets poses pinch point – Lack of height indicator – Sprocket misalignment may cause premature belt wear – Too much deflection from clearance between inner and outer posts
Current State Of Design • Design does not meets all customer needs – Lacks height indicator & safety covers for hand crank towers • Design does not current meet all engineering specs – Horizontal deflection is still unknown, close to spec without powder coating, expect better results – Torque to raise needs quantification – passed usability trial • Budget: Below target • Schedule: – Schedule slipped, due to long lead time at powder coaters, delay of assembly and testing – Successful prototype had unrealized flaws – Partial installation scheduled for this afternoon; target completion next week during clinic downtime • Future Improvements – Easy to convert to electric drive in future – Tighter tolerances on posts, looser control of ACME nuts
Acknowledgements • Guide: Dr. Beth De. Bartolo • Corporate Contact: Nazareth Physical Therapy Clinic – JJ Mowder-Tinney – Lindsey Pendleton A special thanks to: – – – – Rob Kraynik Steve Kosciol Dave Hathaway Paul Gaylo Frank Lucisano (welding) Andrew Cappella (welding) Dr. Daniel Haines (Manhattan) Brian Kolenich (Bailey)
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