Spiral / Power Spring design?
Spiral / Power Spring design?
(OP)
Howdy,
I'm looking for any equations to help ballpark a spiral spring design. I'm working on a retractable lanyard for keys / tools, etc. I'd like to find some equations that will estimate pull force for a given mat'l thickness, O.D., I.D. etc. This is the same type of spring you would find in a tape measure, starter recoil,...
I've found computer programs for purchase that will do this, but I'm just looking for the equations.
Thanks for any info,
--> Karl
I'm looking for any equations to help ballpark a spiral spring design. I'm working on a retractable lanyard for keys / tools, etc. I'd like to find some equations that will estimate pull force for a given mat'l thickness, O.D., I.D. etc. This is the same type of spring you would find in a tape measure, starter recoil,...
I've found computer programs for purchase that will do this, but I'm just looking for the equations.
Thanks for any info,
--> Karl





RE: Spiral / Power Spring design?
Try this site:- http:/
desertfox
RE: Spiral / Power Spring design?
I think this is what I'm looking for. Thanks a bunch!
--> Karl
RE: Spiral / Power Spring design?
desertfox
RE: Spiral / Power Spring design?
RE: Spiral / Power Spring design?
Here is a mch better link on spring design, also it gives design on constant force springs on page 159.
http://
desertfox
RE: Spiral / Power Spring design?
From what I've seen, even an everyday tape measure doesn't rely on just the tape to pull it back. Mine has an additional flat spring contained in an inner casing. I'm not sure if its a normal constant-force spring or a power spring, since I never pulled it out of the casing.
The lanyard I'm working with uses a pre-stressed power spring. It looked like a spiral spring until it flew out of the casing and nearly decapitated me. The general equations for this type of spring are covered in the spring handbook.
Thanks again!