[SML] Variable speed motor

[Loren Schreiber]

AC motors have pretty much supplanted DC motors in most industries. The 
cost of AC inverters (drives) has come down to the point that AC is 
actually a much more economical way to go.

In this case, it's not a simple matter of buying a variable speed motor. 
All commonly available motors (AC or DC) will need a gear box of some 
sort to drop the speed and increase the torque to something you can use. 
But that's not the end of it. If you are connecting a cable to this 
motor, then you will need a drum of some sort and the support structure 
(winch) to go with it. As others have mentioned, then there is 
electrical cabling ($$), controls, e-stop circuits, electrical 
enclosures etc., etc., etc. All this is fun stuff to design and build, 
but it sounds like you are on a tight schedule and a little behind the 
curve for developing your own system in house.

Others have mentioned Creative Conners as a source for a turn-key system 
that you can buy off the shelf. I heartily concur. However, a glance at 
the prices (and Creative Conners is very affordable when compared to 
other available systems) and I think, in this case anyway, you might 
just want to pull a rope. I have designed and built automated scenery 
movers for decades now, but these days it's just easier, cheaper and 
faster to buy a system like Creative Conners.

OK, that said, I know of a school that will rent a compact hand-cranked 
winch that would likely work in your situation. Most of your cost would 
be shipping to and from your theatre because winches are heavy. Let me 
know and I will put you in touch.

Loren Schreiber, Professor Emeritus
San Diego State University