If I make a helical spring out of size X music wire, of length L and diameter D, with N number of turns, does anyone have a formula for the spring constant? This could be in pounds per inch or any other units you care to give. I don't need rocket science accuracy.
Thanks,
Will
Will Self wrote: (clip) does anyone have a formula for the spring constant (clip) ^^^^^^^^^^^^ I don't have a formula, and I don't even know where to look for it, but, if no one else provides one, I can suggest a way of deriving it. A coil spring is just a torsional spring wound into a helix, to make it more compact. So, if you think of your wire as a torsional spring, you can calculate how many degrees of rotation it will take to close it a certain amount. Then apply the formula for torque vs angular rotation (which I haven't looked up either.)
I would buy them if I could. I have pored over the MSC catalog looking for what I need. Of course, I can make some and then measure them, and in fact will probably do that, but a formula to guide at the outset will be a great help. I'm eager to try out Dave Baker's formula. Thanks, Dave!
I bookmarked this site years ago years ago and have found it useful on several occasions
If you have a good collecti> If I make a helical spring out of size X music wire, of length L and
Will this one work? I don't really understand spring rate calculations this but google turned this up on public side of efunda:
The standard equation for a helically wound spring with round cross section is :
k (expressed in pounds per inch) =(d^4 * G)/(8*N*D^3)
where d= wire diameter(inches), D = mean diameter of the coil(inches), N = the number of turns, and G = the modulus of rigidity(aka shear modulus) For steels this value is in the range 11e6 to 12e6 so using 11.5e6 lb/in^2 will get you close.
Richard Coke
I found those articles in HSM to be very good. Since the data is presented in the form of nomographs, it is very easy to zero in on your specific spring needs. I have made about 30 springs using them and have been impressed with their accuracy. There is also a formula and chart for sizing the mandrels for lathe winding a given diameter spring which is very good .
Randy
On 03 Aug 2003 20:40:01 GMT, snipped-for-privacy@aol.comma (Dave Baker) wrote something ......and in reply I say!:
PMFJI.
Can you parethn....pra... you know, put brackets in your formula? I tried applying it various ways and got crazy answers.
And do you mean dims in mm, but answer in lb/inch?
Thanks in advance.
****************************************************************************************** I could never _see_ myself as anything!Nick White --- HEAD:Hertz Music Please remove ns from my header address to reply via email !!
I can't honestly see what could need parenthesising but anyway
Let spring be as follows:
o/d 34mm wire diameter 4mm compressed length 28mm
d = 4mm D = 34-4 = 30mm N = (28/4) minus 1.7 = 5.3
rate = 4^4 / 30^3 / 5.3 * 60000 -->
rate = 256 / 27000 / 5.3 * 60000 =107 lbs/inch
Dave Baker - Puma Race Engines
On 12 Aug 2003 13:07:13 GMT, snipped-for-privacy@aol.comma (Dave Baker) wrote something ......and in reply I say!:
Thanks for the clarification. Your formula agrees with Richard Coke's, and my spring has a smaller D (6" not 13"). So my spring now rates at
950 lb/inch. Now _that's_ a spring!Sorry about all that.
****************************************************************************************** I could never _see_ myself as anything!Nick White --- HEAD:Hertz Music Please remove ns from my header address to reply via email !!
I hate it when my tape measure lies to me. I'm glad you got it figured out. Simple coil springs are one of those very basic yet very interesting devices that have endless applications.
Having an understanding of the principles of their design makes it a lot easier to select and use them whenever and wherever you need them. The equation used for compression springs can be applied to tension springs as well but you have to watch out for preload resulting from the coils being closely wound. The actual value of k doesn't change but the amount of force required to stretch the spring the first small distance to separate the coils can vary widely. Ahh, springs! Valve closers, catapults, pogo sticks.......
Richard Coke
On 13 Aug 2003 14:25:05 GMT, snipped-for-privacy@aol.com (Richard Coke) wrote something ......and in reply I say!:
Well, thanks for talking it through. And interestingly, I was just wondering about tension springs. I will have to do some looking up.
Measure twice post once
****************************************************************************************** I could never _see_ myself as anything!Nick White --- HEAD:Hertz Music Please remove ns from my header address to reply via email !!
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