How do I calculate the energy density of a main-spring?

[lightspd]

Homework Statement

How do I calculate the energy density of either a main-spring (like in a clock) or a motor-spring?
Can someone show me values put into the correct formula for something like e.g. steel?

I did find some material properties like this: http://www.engineeringtoolbox.com/yo...lus-d_417.html

The motor-spring I am interested in is a type like this: http://www.sdp-si.com/Gateway/D220-T183.htm


Secondly, I would like to experiment with various materials (composites especially). If I make a plank of this material, how can I measure its properties to be able to put it into the correct formula for energy density of such a spring (if made into a spring)? I would have to take into account the breaking-point of the material of course (i.e. I bend the plank and at some point it either snaps or buckles).

I did study mech. engineering for a coupple of years but it is 20 years ago and I am rusty ;-)
I have googled and read a lot but am still stuck. Most stuff only relates to compression-springs but I need to work out spring constant of basically a beam (?) and not sure of to work out the breaking point (of the clockspring) when I know that a certain material will snap when it is deflected a certain amount.

Homework Equations

The Attempt at a Solution

Thanks and Regards,

 

[lightspd]

Bump!

nobody knows the answer to this?