Dynamic Wrist Brace

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Dynamic Wrist Brace

• Brian Coleman
• Noah Hopson
• Steve Johnson
• Chris Knowlton

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Why the Brace?

• Snowboarding's 1 reported injury is wrist injury
• Breaking of the scaphoid bone occurs if the wrist
  is flexed beyond 60 degrees
• Low blood flow to the bone causes healing
  problems
• Potential for long term damage

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Team Mission

• Design a dynamic wrist brace system
• Prevents over extension of wrist (beyond 60
  degrees)
• Damps energy created by falling
• Allows non-damped movement

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Project Scope

• Review options to prevent scaphoid bone injury
• Generate possible design iterations
• Select the most robust design
• Develop a working prototype
• Test this prototype and compare to previous work
  and competitive products

5
Generating Customer Needs

• Must prevent injury
• Small
• Lightweight
• Un-obtrusive to normal movement

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Function Model
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Product Specifications

• Life cycle gt 1000 (1 fall 1 life cycle)
• Weight lt 1.5 lbs per brace
• Allow un-restricted movement (30 degrees down
  from level)

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Design Concept Rubber Bumper Compression

• Based on knee brace design with compression
  bumpers
• Advantages
• Light, unobtrusive
• Provide dynamic damping
• Disadvantages
• Unproven damping system

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Competition

• Flexmeter
• Developed by Dr. Marc Binet, MD in cooperation
  with Dupont Engineering
• Uses a plastic brace held to the wrist with nylon
  straps
• Brace contains a live hinge to at wrist joint to
  provide movement
• 52 volunteer physicians based in Publier, France,
  suggests a 60 reduction in snowboard wrist
  fractures with the use of the Flexmeter

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Previous Work

• A prototype fluid damper was constructed and
  tested

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Mathematical Model

• What are we trying to answer?
• What spring constant and damping coefficient
  values are required to dissipate enough fall
  energy to prevent injury?
• How?

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Mathematical Model Results

• Calculated K value is 1200 lb/in.
• Corresponding tensile strength is 1200 psi
• Lead to material testing of SBR, EPDM and
  polyurethane

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Pro-E Simulation

• Wrist brace was preliminarily designed in Pro-E
• Pro Mechanica was used to apply an impact force
• The energy absorption material was represented by
  springs and dampers

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Theoretical Results

• Simulated loading of 50lbs shows correlation
  between the math and ProE model
• 60 degree injury threshold is not broken

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Rubber Selection

• CES Material Selection Software
• Materials were eliminated based on calculated
  criteria
• Graphed materials based on the modulus of
  elasticity

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Testing

• Procedure
• Drop 50 lb cradle (containing brace) from 20in
  onto a hard stop
• Data Collection
• A linear potentiometer was used to measure the
  cradle position
• LabView was used to collect the position v. time
  and export an Excel file

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Test Fixture

• Vertical Drop Fixture
• Positioned determined by linear potentiometer
• High strength bearings used to eliminate binding

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Our Results
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Aesthetic Model

• Created using ProE model and rapid prototyping
  machine
• Representative of actual production brace

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Recommendations/Conclusions

• Re-design the hand section of the brace to more
  effectively distribute the load
• Add a hard stop at the 60 degree injury threshold
  to effectively reduce scaphoid bone injury
• Glove/Brace system must be unobtrusive and light,
  but effective
• Testing shows the Flexmeter offers very little
  protection from wrist injury
• Rubber bumper system provides more effective
  wrist protection than current products

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Questions???