Coil Spring Expansion

[richg1]

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!

 

[desertfox]

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

 

[richg1]

Thanks desertfox,

I just need a clarification on the symbols.

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

Cheers,

Richg1

 

[desertfox]

Hi richg1

yes you are correct with your assumption.


D= o.d of spring

d= wire dia

regards desertfox

 

[EngineerPhil]

what is p?

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

Phil.

 

[desertfox]

Hi EngineerPhil

The p is the pitch of the coils

regards desertfox

 

[ubergeek]

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?
Cheers,
Ubergeek

 

[louloizides]

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.

 

[israelkk]

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

Where:

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.