Anyone know the formula for working out spring rates?

All knowing engineering friends mention it to me and then can't tell me the exact formula.....

Something to do with length, width of the spring and number of turns I think.....

[Edited on 13/5/03 by uberf1end]

Rate=Gd^4 over 8nD^3

where

G is modulus
d is wire diameter
n is number of active coils
D is mean spring diameter

all off the top of my head of course..

Alan B:
> Rate=Gd^4 over 8nD^3
> where
> G is modulus

'scuse my ignorance, but what is modulus?

Does it vary with materials or are they all (mostly) made out of the same stuff?

Ta,

- Greg H

Sorry,

G is modulus of rigidity, not to be confused with E, Youngs modulus

Indeed it is a material property and for regular spring steel it is..

11.5 x 10^6 psi

7.9 x 10^10 Newtons/m^2

(you check them though...)

Try this link??

http://www.rapidline.com/calc/suspension/pccoilsp.htm

Ah yes....MUCH better idea....

Cheers boys.

I'll download their freebie version...don't fancy paying for it though