Flat/parabolic mono-leaf spring design --- where to start? 1

[acfixerdude]

I'm working on a design project and need to figure dimensions, type of material and curvature.

Are there any good reference sites that could help me out here? This was not covered in school, lol.

I'm basically designing something like the springs on this:

http://www.aliexpress.com/store/pro...angoo-jump-Bounce-Shoes/400707_453863523.html

but with metal instead of thermo-plastics.

Thanks for any tips.

 

[drawoh]

acfixerdude,

You should have covered curved beams in college. Roarks Equations for Stress and Strain will be a good reference for you. Springs like this are like cantilever beams. Beam equations are helpful.

Your deflections will be large. Double integration method is only accurate when deflections are less than 10% of the length. Consider read up on basic bending theory. A lot of FEA also is for small deflections. Watch out!

--
JHG

 

[drawoh]

acfixerdude,

I have analysed stuff like this, although it was not for shoes. If this thing is metal, it is going to be ultra stiff, to the point of being a structure, rather than a spring.

You need a material with a low elastic modulus. This is why beryllium copper is a popular material for springs. I can see why these things are made of (reinforced?) plastic. Large deflections on and off means high stresses and metal fatigue.

If someone bounces up high on these things and makes a bad landing, can you get sued?

--
JHG

 

[acfixerdude]

Thanks for the information gentlemen. The e-mail notifications of your replies ended up in my spam folder so I'm just now seeing it. I was going to use equations and model it similar to a cantilever beam but on the next page of the book I was looking at I found equations for a parabolic type beam with the force in the middle. Hopefully they are accurate. We'll be making the prototype springs out of carbon fiber composite (we have a bunch of prepreg just sitting in the freezer) and hopefully they'll be stiff and springy enough. Jeeze what an oxymoron.