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How to calculate energy density of mainspring? 
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#1
Jan2413, 05:59 AM

P: 5

Hi,
How do I calculate the energy density of either a mainspring (like in a clock) or a motorspring? 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/yo...lusd_417.html The motorspring I am interested in is a type like this: http://www.sdpsi.com/Gateway/D220T183.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 breakingpoint 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 compressionsprings 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 


#2
Jan2413, 06:10 AM

P: 5

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 motorspring), 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 


#3
Jan3113, 03:07 AM

P: 5

Bump!
Sorry I have crossposted 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 mainsprings? Can someone recommend a good book on the subject? Not interrested at all in compressionsprings, only mainsprings and tensator springs and the like. Thanks. 


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