Tool-Free Adjustable Foot Stretcher

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Tool-Free Adjustable Foot Stretcher For Hudson
Rowing Shells Brent Davis Casey Haddock Audrey
Harper Jennifer Hoover Wes McGee Georgia
Institute of Technology ME 4182 Capstone
Design July 25, 2001
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Agenda

• Background
• Current Design Overview
• Design Concepts Selection Methods
• Part Drawings
• Engineering Analysis
• Prototype Construction Demo

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Background

• Whats a rowing shell?
• A rowing shell is a small, lightweight boat
  used in crew racing
• Whats a foot stretcher?
• The rowers shoes (and feet) are securely held
  to this part of the boat
• The rower pushes off the foot stretcher during
  the stroke to propel the boat through the water

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Current Design

• Whats right with the current foot stretcher?
• Lightweight ( 1.5 lbs.)
• Durable
• Whats wrong with the current foot stretcher?
• Adjustments must be made using tools
• Some adjustments cant be made at all

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Design Concepts

• Throwing out the bad
• Allow complete adjustment of angle of foot
  stretcher, as well as foot position
• Adjustments made without tools
• Use evaluation matrices for concept comparison
• Keeping the good
• Keep weight down and durability high

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Part Drawings

• 3D Layout Drawings
• Mechanical Desktop used to model parts and
  overall assembly
• All parts modeled to proper dimensions
• Visualize design before prototype manufacture
• Estimate weight of new design ( 2 lbs.)
• Export to finite element analysis software for
  engineering analysis

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Part Drawings

• 2D Part Drawings
• AutoCAD used to draft each part of foot
  stretcher
• 11 unique parts of varying complexity
• All parts drawn to proper dimensions
• Aid machine shop and welders in fabrication of
  foot stretcher parts
• DXF exports of drawings used for CNC

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Engineering Analysis

• FEA (I-DEAS)
• Shell mesh w/ 250 lb. force distributed over
  four locations
• Deflection and stress found to be negligible
  (0.00032 mm 34.1 kPa)
• Material Selection (CMS)
• Materials evaluated by strength, weight, and
  cost
• Aluminum alloy or magnesium suggested

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Engineering Analysis

• FEA Verification
• Hand calculations used to verify FEA results
• Deflection and stress calculated using simply
  supported beam under single load
• Deflection calculated to be 0.057 mm
• Stress calculated to be 23 MPa still below max
  stress for Aluminum
• Differences due to assumptions

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Prototype Fabrication

• Custom Parts
• CNC on Bridgeport mill used to machine parts
  from CAD drawings
• Wire EDM used to create clamps due to profile
• Tubular sections fabricated from stock aluminum
  tubing
• Pre-Manufactured Parts
• Quick-release skewers

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Prototype Demonstration
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Prototype vs. Design

• The Real World
• Prototype grossly overweight (5 lbs.)
• Fit and tolerances limited by machine shop
  capabilities
• Threads had to be cut on quick-release skewers
• Prototype Results
• Withstands force exerted by rower
• Easy to adjust, secure

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Thanks for listening! Any questions?