Technical Topic Presentation

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Technical Topic Presentation

• SPRINGS

Presented by John Helme November 15, 2006
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Whats the Problem?

• 3x7 curtains need to be extended and
  contracted.

Whats a Solution?

• Wrap the curtains around a shaft. Extend the
  curtains using a motor, retract the curtains
  using springs.

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Hook Law

• BRIDGEPORT, Conn The City Council approved a
  new ordinance requiring coat hooks in all public
  bathrooms.
• The councilman who offered the proposal says
  no one should have to leave their coat or other
  belongings on unsanitary floors.

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What we already know.

• Hooks Law
• F -kx
• F restoring force
• k spring constant
• x displacement of spring from equilibrium
• Potential Energy in a compressed spring
• U(1/2)kx2

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Combinations of Springs

• Two springs in parallel
• keff k1 k2
• Two springs in series
• keff k1k2/(k1 k2)

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Types of Springs
Compression
Extension
Torsion
Spiral Torsion
Power Torsion Clock, Constant Force
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Where do springs come from?

• Distributor McMaster-Carr
• Stock Sizes
• Manufacture
• Large quantities
• Sample kits
• Design assistance software, engineering
• Fabrication Shop
• Small quantities

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Distributor Price Sheet
www.mcmaster.com
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Design Software
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Fabrication Shop

• Pricing Equation
• Cost of material
• Setup time
• Manufacturing time
• Cost for secondary and finishing work like
  plating
• Profit
• Shipping

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Spring Fabrication
Parts Outside Housing Coil
Coil Length Extension length 36 Number of
turns Extension length/(ID of housing pi)
1.15 Minimum ID Number of Turns thickness of
Coil material 2 .25
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How Does the Window Shade Work?
Do not know. They are impossible to take apart
when a spouse is nearby. Good thing its early
in the design phase of the project.