Winter Sports Wrist Brace

1
Winter Sports Wrist Brace

• Design, Manufacture, and Test
• Matt Anderson
• Summer 06

2
Introduction

• Scaphoid fracture most common snowboarding wrist
  injury
• Beyond 60 degrees rearward rotation fractures
  occur

3
Objectives

• Design a brace to prevent wrist from rotating
  beyond 60 degrees
• Provide limited wrist movement to increase user
  compliance

4
Concepts

• Leaf spring
• Hydraulic Damper
• Air Spring

5
Concept Selection

• Leaf spring
• Limits wrist movement forward and rearward
• Reaction force dependent on deflection

6
Concept Selection

• Hydraulic Damper
• Limits wrist movement rearward only
• Reaction force dependent on velocity of fall

7
Concept Selection

• Air Spring
• Limits wrist movement rearward only
• Reaction force dependent on deflection

8
Concept Selection

• Hydraulic damper adapts to users weight and
  travel velocity

9
Damper Components
Fluid Chamber
O-Ring Grooves
Accumulator Piston
Piston
10
Math Model

• 50 lb weight dropped from 26 in results in impact
  velocity of 11.81 ft/s
• Required damping coefficient determined for
  overdamped system
• Solution to an overdamped system

11
Math Model

• 0.75 in piston assumed
• Calculations to determine displacement for 60
  degrees of rotation

12
Math Model

• Initial velocity used to graph response of system
• Max displacement less than allowable displacement
  of 0.562 in

13
Math Model

• Required damping coefficient determined to be 300
  lbs/ft
• Equivalent damping coefficient for hydraulic
  damper required
• Damping proportional to square of
  velocity

14
Math Model

• Equivalent damping coefficient determined using
• Work performed by damper
• Pressure drop across orifice
• Force on piston
• Work performed by viscous damper
• Damping coefficient used to determine required
  orifice diameter of 0.02 in

15
Test Apparatus

• Designed to drop 50 lb from height of at least 26
  in
• String potentiometer used to measure deflection
• Labview utilized to record deflection as function
  of time

16
Test Apparatus
17
Test Method

• Determine voltage output at contact position
• Raise falling weight and measure distance from
  bottom of weight to top of brace
• Start Labview program
• Release weight from starting height
• Convert output voltages to displacements

18
Test Results

• First round of tests showed very little damping
  capability
• Caused by air inside cylinder
• Filled cylinder inside oil bath to alleviate
  problem

19
Test Results

• Second round of tests showed very promising
  results
• Max displacement matched math model

Theoretical
Experimental
20
Test Results

• Tests prove that brace is capable of preventing
  rotation beyond 60 degrees

21
Future Recommendations

• Conical compression spring to limit space
• Accumulator spring
• DFA/DFM
• Plastic injection molded components
• Integrate brace into winter glove

22
Conclusion

• Scaphoid fractures can be prevented by limiting
  rotation to 60 degrees or less
• Maximum displacement test results matched math
  model
• Hydraulic damper capable of preventing
  over-extension of wrist
• Hydraulic damper adapts to user weight and travel
  velocity
• Brace should be integrated into a winter glove
  using injection molded plastic components

23
The End

• Special thanks to Dr. Farris and Dr. Blekhman
• Questions?