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.