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 Spring Design – Change in Diameter with Compression Post Reply Forum
 Posted by: jalipa ® 09/24/2003, 08:21:07 Author Profile Mail author Edit Hi Guys, A handbook I’ve got states that a spring has a 3-4% change in diameter when compressed. I want to fit this spring in a fairly tight hole. Does anyone know how the change in diameter is calculated? I seem to recall that there was nifty little formula but I cannot find it. Can any one help? Thank you, J

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 Re: Spring Design – Change in Diameter with Compression Re: Spring Design – Change in Diameter with Compression -- jalipa Post Reply Top of thread Forum
 Posted by: gfought ® 09/24/2003, 09:00:13 Author Profile Mail author Edit I have checked several of my references and I don't recall seeing anything on the change in outside diameter of a compression spring under load. There are manufacturing tolerances that you have to allow for in your design that could be more or less 3-4%. eFunda is a good site for reference...

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 Re: Spring Design – Change in Diameter with Compression Re: Re: Spring Design – Change in Diameter with Compression -- gfought Post Reply Top of thread Forum
 Posted by: jalipa ® 09/25/2003, 03:41:59 Author Profile Mail author Edit I now have several formulas:- For a compression spring which has ends that are prevented from unwinding during compression the formula for expansion on diameter is as follows:-     change in dia= 0.05 * (p^2-d^2)/D     where d = wire dia           D = mean dia of coils           p = pitch of the coils when spring is in its                free state formula represents spring going from free height to solid length. Alternative version of the formula (from an Italian Spec....don't ask):- change in dia = p^2-d^2/20D and change in dia = p^2-0.8d^2pd – 0.2 d^2/10D J.

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