How to calculate energy density of mainspring?

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To calculate the energy density of a mainspring or motor-spring, one must use material properties such as Young's Modulus and ultimate tensile strength, which can be found on engineering resources. The discussion emphasizes the need for specific formulas applicable to beam-like springs rather than compression springs. For practical experimentation with various materials, measuring properties like breaking point is crucial, especially when creating composite materials. A concrete example using acrylic illustrates the calculation of energy density, highlighting the importance of knowing material properties. The thread also seeks recommendations for resources focused specifically on mainsprings, as existing literature tends to concentrate on compression springs.
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Hi,

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 steel?

I did find some material properties like this: http://www.engineeringtoolbox.com/young-modulus-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.



Thanks a lot.

Regards
 
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A concrete example I would very much like to see is something like this:

Take an acrylic ruler. it is 30 cm long, 3 cm wide and 2mm thick. It weighs 20grams (just estimated for this example).
Acrylic has Youngs Modulus of 3.2 GPa and ultimate Tensile Strength of 70 Mpa (according to the page I posted ealier).

If I took this material and used 500cm of it and turned it into a mainspring (or motor-spring), then:

a) What is the energy density of the spring?

b) If I didn't have Youngs Modulus and Ultimate Tensile Strength, how could I work these out (and any other values that I might need)?Thanks and regards
 
Bump!

Sorry I have cross-posted this in the coursework forum, many reads but no answers :-(
Is no one able to help me with this?
When I google, I only find articles related to compression springs. Why is it so difficult to find stuff on main-springs?

Can someone recommend a good book on the subject? Not interrested at all in compression-springs, only main-springs and tensator springs and the like.

Thanks.
 

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