Overwind protection for small constant force spring motor

[hydrobro]

I am using a 0.6 in-lb constant force spring in a spring motor assembly. I have heard that constant force springs should always have at least 1-2 turns on both the storage and output spools. Is that true for small springs? If I were to attach the ends of the spring with a single screw to the output and storage spool, would that be enough overwind protection? Any other attachment suggestions would be appreciated. I want to keep my assembly simple, so I am trying to avoid an overwind protection using string and spool.

 

[drawoh]

hydrobro,

Can you put up a picture of some kind?

When you say overwind protection, are you talking about making it strong enough that the user cannot break it, or are you talking about a mechanical stop?

Is the spring extended by people, or by a machine?

I keep a small spring scale at my desk. A small fish scale from a hardware store should work, although I bought mine at a scientific store, and it is marked in Newtons and grams. You can play with the scale and work out how much force a user will be willing to extert on your motor.

A good alternative to a solid mechanical stop would be for a well defined transition from extending spring to fully extended spring. If the user has good feel for when they have to stop pulling, they will stop pulling. Make the handle look flimsy. Remember that when you make things idiot resistant, the world will make a better idiot.

Check out forum280.

JHG