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Coil Spring Expansion

Coil Spring Expansion

Coil Spring Expansion

Does anyone have know of any formulae/info to calculate the diametrical expansion of coil compresion springs?

Have looked in all the usual places with no luck!

RE: Coil Spring Expansion

Hi richg1

I have a formula here for coil growth its:-

   O.D.solid= sqr root (D^2+ d + (p^2-d^2/(3.142^2)))

regards desertfox

RE: Coil Spring Expansion

Thanks desertfox,

I just need a clarification on the symbols.

Also is the last bit meant to read (p^2-d^2)/(pi^2)?



RE: Coil Spring Expansion

Hi richg1

yes you are correct with your assumption.

D= o.d of spring

d= wire dia

regards desertfox

RE: Coil Spring Expansion

what is p?

how do you account for different wire properties and hence expansion?


RE: Coil Spring Expansion

Hi EngineerPhil

The p is the pitch of the coils

regards desertfox

RE: Coil Spring Expansion

Hi desertfox,
Thanks for the formula.
I'm working on a problem with a coil spring binding in the ID of its housing. The above formula is very helpful but do you have anything that would take material properties into account?

RE: Coil Spring Expansion

I'm looking for the same formula, but I don't want to use it unless I know where it came from. Can you help me out with this? Is there a book I can reference or can you just derive or explain the equation? Also, I've heard that some spring materials contract as the deflection gets greater. Any insight into this? I appreciate any help I can get. Thanks.

RE: Coil Spring Expansion

O.D.solid= sqare root (D^2 + (p^2-d^2/(3.142^2))) + d


O.D. - Outside diameter
D - Mean diameter
d - wire diameter
P - coil pitch

DESIGN HANDBOOK Engineering Guide To Spring Design, 1987 Edition, Page 31, Associated Spring - Barnes Group Inc.

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