Where to purchase just a few gears?

Yep - both or more can be the same or one linear and the other log... one increasing as the other decreases...

Some are user build able - a short shaft on one with cuts in the shaft. It simply plugs into the back of the long shaft type and two mounting lugs are then attached... Look at pictures.

Allied might have pictures..

Martin

But those tend to be the single-turn (actually, around 270 degrees or so, not ten-turn or twenty-turn -- though I have seen a ganged ten-turn pot -- *once*.

Note that in the single-turn arena, there used to be some *very* nice ones. The pot is a machined aluminum body, nicely anodized, ball-bearing mounted shaft, with a groove into which the resistance card goes. For a tapered resistance, you can wind resistance wire on a contoured card (width changes as you go along, so more length of wire is needed to wrap around it).

There are also provisions for mounting extra taps below the wipers, brought out to a terminal block, so you can add parallel resistors to make a complex resistance taper.

These are designed to mount with the open end towards a plate which contains the final shaft (coupled by a crank pin), and more sections can be stacked on after those. I have seen stacks of eight or ten sections in complex applications. And -- the coupling is with rings around the join, with grooves on either side of the join so you can rotate the pots relative to each other.

The resistance element on these tends to be nearly a full 360 degrees. Still not the needed ten-turn ones, and awfully expensive for a volume control for your stereo, but for the application the best thing around.

I don't know whether these are still made. They were used for analog computing applications, mostly, and most of that has been displaced with digital.

Good Luck, DoN.

Have you considered just buying a two gang pot? These are available in multi turn form.

Ted

instrumentation

Several people have suggested this and my initial reaction was that I had never seen a ganged multiturn pot. Now I'm sure that they've been made and I'm sure that companies like Bourns would love an order to make a bunch again -- but for my one-off instrument panel, it's not going to happen that way. I have catalogs here from Newark, Mouser, and Digikey that I need to find the time to go through -- and of course there's a world of stuff available on-line. Since I've been assured that these are available, I'll investigate further.

Also, I have considered using independent pots with stepper motors turning them and I suppose that's what I'll have to do as a last resort -- but a few gears from Small Parts or PIC will probably be cheaper -- though both have fairly high cost in terms of creating mountings for them. I also like the idea of coupling the two shafts together and then turning them with a pulley or belt. As long as I provide an independent readout of the results this would also work -- I guess I'm trading mechanical engineering and machinist time here for additional electronics.

I think I have enough ideas to get into real trouble and I thank every one who's taken the time to make suggestions.

Norm

One other idea that struck me just this moment....(ouch!)

Turn the pots facing each other and couple them together with a sleeve on both shafts, end to end, with a gear or simply string pulley on the sleeve. Obviously you would have to turn them to the same value before tightening down the set screws..but they would be matched when turning and backlash would effect both of them equally.

Gunner...who has a feeling he is missing something here.....shrug... Liberals - Cosmopolitan critics, men who are the friends of every country save their own. Benjamin Disraeli

where I used to work, they had a big catalog from Boston Gear. must have been two inches thick. Not sure if they are still around but worth a try.

WM Berg also has stuff. Small Parts, Inc., has it too -- significantly smaller selection of gears but a no-hassle retail ordering policy.