P08002 Automated Parallel Bars Jeff Osborne Ryan Hellems Justin Knowles Justin Vowles Jessica Stalker ME ME, Lead ME ME ISE Project Introduction Working with the Physical Therapy clinic at Nazareth a system was developed to simplify the adjustment of their parallel bar system, which is used for neurological rehabilitation. The new design replaced the 3-independent hole-and-pin posts with one simple hand crank. The system also eliminates the hazards associated with uneven or unlevel bars, and allows for easier patient repeatability. Entire Current System Current System Customer Needs/Engineering Specs “They Said” “We Heard” Safe for patient and PT Ease of adjust Accuracy Reliability No pinch points or sharp edges No trip hazards Minimal vertical deflection (≤ 1.1“ at max height) Reasonable time to adjust (< 60 seconds) Ease of adjustment (torque < 8.5 ft-lbs) Ensure bar is always horizontal (+/- 0.05 degrees) Height indicator (16 in. range: 26-42 in.) Performance constant for life (288,000 cycles, 5 years) Preservation of current system (ability to “roll back”) Redesigned System Design Analysis Crank Tower Subsystem 4:1 gear ratio for belt drive provides 0.5 inch per revolution Ergonomically located hand crank, easy to turn Removable handle prevents incidental adjustment System FBD Torque to Raise Max Horizontal Deflection, plus contact deflection: 0.43 inches Max Von Mises 18635 psi [modeled with no clearance] Input force needed to raise bars with 6 inch handle and 4:1 gear ratio = 2.19 lbf Lifting Subsystem Deflection Test Results Three posts tied in series by a single 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 Conclusion: Inner posts were powder coated and plastic shims were added to reduce clearance and deflection. 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.