Technical Topic Presentation
SPRINGS
Presented by: John Helme
November 15, 2006
What’s the Problem?
3’x7’ curtains need to be extended and contracted.
What’s a Solution? Wrap the curtains around a shaft. Extend the
curtains using a motor, retract the curtains using springs.
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.
What we already know.
Hooks LawF = -kx
F = restoring force
k = spring constant
x = displacement of spring from equilibrium
Potential Energy in a compressed springU=(1/2)kx2
Combinations of Springs
Two springs in parallel:
keff = k1 + k2
Two springs in series:
keff = k1*k2/(k1 + k2)
Types of Springs
Compression Extension
TorsionSpiral Torsion
Power TorsionClock, Constant Force
Where do springs come from? Distributor – McMaster-Carr
Stock Sizes Manufacture
Large quantities Sample kits Design assistance – software, engineering
Fabrication Shop Small quantities
Distributor Price Sheet
www.mcmaster.com
Design Software
Fabrication Shop
Pricing Equation: Cost of material Setup time Manufacturing time Cost for secondary and finishing work like plating Profit Shipping
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”
How Does the Window Shade Work?
Do not know. They are impossible to take apart when a spouse is nearby.
Good thing it’s early in the design phase of the project.