Clock Springs

[lgsabr]

I'm trying to make a retractable cord system using a clock spring (kind of a hobby/home project). I am looking for a pull of 10lbs and about 20' of release. I want to keep it fairly small, say under 4" diameter...so about 19 turns.?.? Can anyone help me get started with how to determine spring size (or if there is somewhere I can go that will allow me to pick the clock spring based on the parameters I described above)? I have an engineering background so I can do calcs if need be. Thanks

 

[MikeHalloran]

http://www.asbg.com/en/springs/flat-spiral-springs--power-springs

Mike Halloran
Pembroke Pines, FL, USA

 

[israelkk]

Clock spring is not able to rotate 19 rotations. The available spring types are "Constant force springs" or "Power springs". But without careful design check it is not possible to say if it can be done. Look at the following spring handbook:

http://www.scribd.com/doc/29044778/...board_MediumRectangle_BTF_300x250&url=http://

http://www.scribd.com/doc/29044778/...Physics&Document=29044778&FourGen=True&skip=0

 

[chicopee]

The torsion springs similar to the types used on overhead doors can do many turns but it will not be a spiral "clock" spring. Refer to Kent ME HDBK "Design and Production" for the springs mentioned above. This HDBK has design formuae to calculate the stresses and the number of turns from woundup to unwound positions for these springs. This HDBK could be your lucky book.

 

[ornerynorsk]

They already exist. You can purchase retractable power cords, pnuematic hoses, etc. If you really need to make one, you can double your number of available turns by gearing the spool, but it also reduce the force accordingly.

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

 

[ornerynorsk]

Just had a thought. You might want to get hold of a retractable laundry line and do some dissecting or reverse engineering. Much higher tension (in addition to the ratcheting stop) and available with much greater line payout capacity, if memory serves. I've seen some that are quite compact.

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

 

[MiketheEngineer]

I have a retractable electric cord system hanging from the ceiling in my garage - I think from Harbor Freight or the like. Looks like the air line recoil systems.

Has about 20' of cord and works great!! I love it. I think it was about $25.00

Might look into that.