Clutch Help Needed

[savarin]

I'm trying to make a clutch/friction drive for the slo-mo control on my telescope.
I've fabricated a proof of concept to see if it would work and it does with a very smooth motion.
but! (always one of these)





If I move the telescope by hand it overcomes the friction as it should but the shaft turns and unscrews the nut controlling the friction pressure.
Any ideas how I can prevent this from occurring considering that it will be a knurled large wheel not a nut so the tension can be varied with it.
One thought I've had is to use a deep groove bearing where the outer race is set in the arm and the inner race is a tight fit to the bolt.

 

[T Bredehoft]

If you had a nut instead of your Knurled large wheel, I'd suggest putting a set screw in it with a bit of nylon (plastic) between the set screw and the threads. Perhaps you could do something like that?

 

[kd4gij]

Just make 2 knurled wheels one as a lock nut

 

[JimDawson]

I think in this case a lock nut is the answer, maybe even a self locking nut would do. A heavy spring between the nut and the clutch would give you more control over the pressure also.

 

[savarin]

I'm just trying to consider future options.
I will want to adjust the free wheeling pressure at times, I have used two wheels as lock nuts in the past on a cantilever binocular mount.
They worked loose after a short while.
As this is a test I'm going down to try the bearing idea as I have one here.
Although I guess a set once to the pressure that works would also be viable.
I like the spring idea as a means of keeping the pressure set.

 

[savarin]

Hmmm, double post for some reason.
Problem solved, the bearing idea works.
Now need some stainless shaft for the new one..