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
Agenda
• Background
• Current Design Overview
• Design Concepts Selection Methods
• Part Drawings
• Engineering Analysis
• Prototype Construction & Demo
Background
What’s a rowing shell?
• A rowing shell is a small, lightweight boat used in crew racing
What’s a foot stretcher?
• The rower’s 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
Current Design
What’s right with the current foot stretcher?
• Lightweight (~ 1.5 lbs.)
• Durable
What’s wrong with the current foot stretcher?
• Adjustments must be made using tools
• Some adjustments can’t be made at all
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
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
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
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
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
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
Prototype Demonstration
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
Thanks for listening!
Any questions?
