OK, the subject came up, so I thought I'd Share

 

Coil springs are a wound up torsion bars.

The three things that change there spring rate is wire diameter, spring length (not the same as spring height) and coil pitch.

Wire Diameter is the thickness of the wire that the coil spring is made from.
It is generally stated in thousands of an inch; as in .625 or .810.
If a pair of springs have the same spring wire length but one .625 and the other .810
the .625 spring will be much softer

Spring Length is the length of the wire coiled into a spring .
If you have two springs with 15 inches of height, each with the same wire diameter
one will have 10 coils and the other will have 12 coils. The one with the 12 coils will be softer.

There are two reasons for this. The first is spring length; you have 20% more wire to put the weight through. The second is coil pitch; as you put the coils closer together it puts more leverage on those coils.

That's how they make variable rate coil springs, by putting some coils close together and other coils further apart.
 

Oh, and a spring's rate is measured in pounds per inch (in./lbs.).

If a spring's rate is 400 in./lbs., it takes 400lbs. to compress a spring 1 inch and 800lbs. for 2 inches of compression..

 

Page written by: Hair and edited by: rentalguy1  

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