self lock gear box

[Gabriel.1]

Hi,

I would like to use a stepper motor for pooling up and down a load, but I do not want to leave the stepper motor powered at hold position. Therefore I would need som mechanism what would allow transfer the stepper motor rotation up and down but the gravitational force from load would be blocked by some kind of lock.
I want to use a simple cord 2-4mm and a simple pulley, load would be like 5kg.

is there something like a self lock when pulled up ?

thanks

 

[IRstuff]

Almost any large downward gear ratio gear train tends to self lock.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

faq731-376 forum1529 Entire Forum list

http://www.eng-tips.com/forumlist.cfm

 

[GregLocock]

Specifically worm drives have to be very carefully deigned to avoid self locking.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[BrianE22]

Specifically for worm gears, the tangent of lead angle of the worm < coefficient of friction. We use .1 for C.O.F. and a lead angle of 5.7 degrees.