"Alan Nishioka" wrote in message
ups.com...
On Jul 13, 7:12 am, msg wrote:
Please view these photos of a three-turn planetary drive
pot that uses a conventional "stackpot" formfactor
athttp://www.cybertheque.org/homebrew/rcvr/images/antennas/pot.jpg
Resistance = 1K

Interesting. I've never seen a pot like this.

So the turns ratio is determined by the shaft diameter to ball
diameter ratio?
And the wiper arm is connected to the ball carrier?
So this assumes the metal to metal, shaft to ball won't slip, but the
ball will turn in the carrier, causing the carrier to have 1/3 the
rotation of the shaft?

Sorry, this doesn't help you at all...
Alan Nishioka
The ratio, is determined by the shaft diameter, to the internal diameter
of the casing in which the balls sit.
If (for instance), you have a 3mm shaft, and 10mm balls, the casing has to
have an internal diameter of 26mm, and the ratio is 26/3 = 8.66:1. The
drive can be made remarkably good (the same system is used on some micro
focussers for telescopes, which carry significantly more torque than
needed for a pot). Units like the 'Williams optics feathertouch focusser',
use exactly this drive.

Best Wishes