Constant Force Springs 1

[clevelandENG]

New to site but so far I love it.

I have a small and maybe a unrealistic problem. I would like to get a small kids car or a small go-kart to take off from spot at a fast pace using a constant force spring. The normal forces would be around 200 to 400 pounds (with weight of driver).

The spring would have tight tension and released to get a shaft moving. One problem is I can’t find a formula for constant force springs and if this is possible with this load.

 

[GregLocock]

http://www.smt.sandvik.com/sandvik

In general when asking questions like this it is advisable to do a google search and an advanced site search before posting.

Otherwise you will be eaten by bears.





Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[btrueblood]

I think you really mean motor or clock springs? Try using the following terms in google: power springs, motor springs, clock springs. Constant-force springs (e.g. metal tape measure) aren't intended to produce torque on a shaft.

Spring design - best reference I know is A. M. Wahl, Mechanical Springs, published by Spring Manufacturer's Institute.

 

[StressGuy]

Greg,

Your link gave me a 404 error.

Now, this may not be quite what you're looking for, but if you want to produce a constant spring load, you can do it with a pair variable springs.

http://www.anvilintl.com/ps_hanger/index.php?CAT=21

I can't get the link to paste correctly. Click the link for the figure 81-H, then go to page two for the writeup on how the spring works.

Edward L. Klein
Pipe Stress Engineer
Houston, Texas

"All the world is a Spring"

All opinions expressed here are my own and not my company's.

 

[Cockroach]

Wow GregLocock, eaten by the bears? I was more inclined to think of it as a shark feast! So true though.

An excellent reference is available from the Spring Institute website. The book is written by Wahl, one of the more influencial engineers on the subject. It is date around the fifties/sixties, but an excellent bible on the subject. I totally, totally recommend it as a reference for all mechanical engineers.

You name the spring, and the book discusses it in detail.

Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada

 

[israelkk]

clevelandENG

The strongest constant force spring from SPEC Associated springs Co. has 7 lb force with 1" wide strip 0.014" thick strip and a 33" extended. It is impractical to have a 200 or 400 lb constant force spring/ However, you can try to work with 30 or 60 of SPEC springs in parallel.

http://www.asraymond.com/