[TowerTalk] Vacuum Variable Over Torque Protection?

[Dan Zimmerman N3OX]

>
> I don't have a remote turns counter and I'd like some kind of
>
protection against such a condition. Do any of you have any good
> over-torque protection methods I could try?


Some of the ceramic  and metal insulating flexible shaft couplings have the
shaft bushings just press fit into the metal spiders and knurled over.  They
seem to be intended to break away under excessive torque.

I'm sure there are plenty of shaft friction clutches out there, but I don't
know where to find them.

Something else I do routinely here is to use a small piece of clear PVC hose
as a shaft coupler.  It would wind up and shear before the capacitor broke,
so it would be sort of a "fuse" solution in the case of accidental overrun.
Since you are only doing a couple of turns near the middle, this might be
easy.

I'd rig limit switches if you routinely want to get near the ends.  The
vacuum variable I use in my magloop takes 20 turns to go from minimum to
maximum, and so a piece of 1/4-20 rod and a tapped bar between two
microswitches an inch apart is perfect.

For that application, I really do want to run all the way to one end or the
other since I can tune 5-21 MHz with it.

73,
Dan