Arboga mill converted to VFD control (pictures)

A standard pot is 270 degrees You could use a three to one gear drive.

Hmm ... that sounds rather specialized. For *one*, I would try one of the precision single-turn pots used in analog computer servo systems in the past. The pot is somewhat larger in diameter, a machined aluminum housing with dual ball bearings at the front, a resistance element consisting of fine resistance wire wound on a card which is fitted into a slot in the housing. There were typically eight-terminal blocks on the side -- three being the typical two ends and wiper, and the others were used for taps which could connect to the resistance element at any point.

You could stack a large number of elements in mechanical series, coupling from shaft to shaft with spring-loaded bellcranks and securing them together by rings which engage grooves on both housings.

Since these used almost the full 360 degrees (a tiny gap where the wiper runs from one end to the other end if stops are not installed), and you want 2.5 K from either side of center of a 90 degree travel, you want 5K total in that range, or 20K total for the whole resistance element.

Non-linear resistances were accomplished by either winding on a tapered card instead of a constant width card, or by fitting multiple taps and adding resistors in parallel with sections to reduce the voltage covered over that range.

Anyway -- these were *very* expensive pots. I used to work with them in the mid 1960s in a flight simulator built for the Navy.

I have a question -- why not get a typical 5K 270 degree pot, put a gear on the shaft, and drive it with another gear? Let's see, 270 degrees from 90 degrees is a 3:1 gear ratio -- so perhaps 16 tooth on the pot shaft, and 48 tooth on the input shaft.

If you need the input shaft to be concentric with the pot body, look into a planetary gear setup. Lock the ring gear, input shaft on the planets, and the pot shaft on the sun gear.

Good Luck, DoN.

That's one idea, but space restrictions preclude gearing. These pots do exist, I just can't find them. They're throttle pots for mobility scooters. There are hundreds of thousands of these things made and sold annually. The pots have to be coming from somewhere. :)

There's not even a mfg. product ID # on them that I've been able to find.

I'd like to find them to cut the cost to customers for repairs. Most manufacturers sell the complete assembly for ridiculous prices. (Like

Most funding agencies don't pay for scooter repairs. So any repairs are out-of-pocket for people who have very limited means in the first place. Medicare just recently started to cover a few scooters at all and those at only a very low level.

Is it possible to do a redesign and sell a conversion kit? Do you have a complete assembly that isn't worth repairing, or some good macro pictures?

Some possible clues/sources...

On this page about half way down:

- Specially for Electric Boat or Industrial Truck applications requiring quick direction change without relays.

- Two types of Speed/Direction control are offered (specify):

1. A toggle switch for direction change and a POT for speed.

- Needs 12V Key circuit; Optional Internal DC-DC Converter to produce 12V from HV Battery.

- 50A models use Wires or Quick-Connect lugs for power. 100A and up units use Copper Rods.

- Molex type header connector is used for control (POT and Key).

It sounds like they have them, maybe can clue you in where they get them from?

Maybe find some ideas/info here too:

Late but, maybe not to late.

Tungatan 10