Power spring, spiral spring - Moment and Stress equations

Try contacting Kern Liebers in the UK (or Germany). They used to produce springs for me, almost that exact spring, and they are experts in this field.

I was using them as balance springs for vertical roller shutters. They also produce them for inertia reel seat belts.

Design Handbook, Engineering Guide to Spring Design, 1987 by Associated Spring (SPEC) Barnes Group Inc.

P.Orlov Ed.Mir volume3,"design engineering".-

I have the four volumes titled "Fundamentals of Machine Design" by Orlov, but they do not have anything on springs. Maybe it's some other book you are referring to.

I think those Mir books are long out of print. In case you have the information I would be obliged if you could try to scan just the relevant figure and equations (relating to torque and stress calculation only) as an image file which could be copied and included when posting in this thread.

Pardon the delay -- I've been travelling, and no internet access. Thanks anyway for your response. Regards, =Teesquare=

Certainly is a different book:"Ingeniería de diseño" which i translated "engineering design" and three are the volumes or tomes the fourth chapter in third vol. is full for diff.springs types.I need know if you refer to spiral or helicoidal types or ("wounded","wounded up", "..reverse.." are not clear expressions to me (i am spanishspeaker)There is a reference to some spring i never saw wires made "multiple souls spring" is the best translation for that i can do.You tell me and i´ll see to send you.-

Thank you for your response. I attach an image from a German catalogue which shows the kind of spring. In the free condition it is "S" shaped as shown on the right, and after the flat spring section is curled in the opposite direction to get all the coils on one side, the assembly is put into a casing (shown on left).

In the assembled condition the spring is already under bending stress with the coils concentrated near the outer casing. When the inner "arbour" is rotated, the winding shfts to the inside and the spring provides a reaction torque. I think you must be familiar with this -- only a language or translation difficulty. If there are equations in your book for Moment (or Torque) at the arbour, and bending stress in the spring, please try to copy them as an image. You need not try to translate all the words as I may be able to guess from the symbols. If there is a numerical example it wll help.

I will be travelling and may see your reply only after a week.

Thank you again, =TeeSquare=

Very different than i thought,even without information about these springs like for toys you could use some information i found here:http://www.newcombspring.com/torsionsprings.html -good luck!

here is a PHD thesis that appears to get into the calculations of power springs and you might be able to use some of it. Good luck

http://scholar.lib.vt.edu/theses/available/etd-71298-181211/unrestricted/whothesis.pdf

If looking for software, go to www.spiral-spring.com

They offer software that uses Finite Element Analysis (FEA) to calculate the spring performance. It is really the only way to handle prestressed power spring design because the other software available does not compare.

If you are also looking for specific design help, they offer consulting services.

There is also some information about the basics of power springs.