AC Servo Winch

I have in my mind a concept for a piece of theatrical scenery which needs to fly up and down about 30', and be positioned repeatably to the resolution of
about 1".
The piece weighs less than 30 pounds, so 1 to 2hp AC servomotor with a single phase 120v power/speed control would be perfect. (I'd settle for single phase 240, but would really prefer to avoid three phase power.) Ideally, it has a few ways to specifiy commands:
1) Go to a position at a certain speed. 2) Spool at a certain speed.
I could build this pretty easy with a DC motor, H-Bridge, and optical encoder. But for once, I'd prefer to spend the money on an off-the-shelf solution.
So: Anyone have a line on an AC servomotor and drive that would be suitable, around (or under!) $1,000?
PART 2:
Anyone have a good source for slip rings? I need to send 12vdc (and maybe video, if I have my way) down the winch, too.
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E. Lee Dickinson wrote:

I know this is probably out of the ballpark, but how about a garage door opener? You could use a rotary limit switch instead of the standard kind on a garage door. I googled for one, and came up with this http://www.peteralbrecht.com/limitswitch.asp which would provide around 1/2" accuracy if used with a 6" diameter drum.
I don't actually know that much about garage door openers. Home Depot seems to be limited to 3/4hp max. Perhaps commercial units are available which have more power. Some boast about having quiet operation, and having "soft start", but of course that is all relative.
Joe Dunfee
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E. Lee Dickinson wrote:

> The piece weighs less than 30 pounds,
Here's a good intro to stage rigging with powered winches:
    http://www.branament.com/flying.php
Another article on safety issues:
http://crpit.com/confpapers/CRPITV15Bauer.pdf#search=%22theater%20winch%20programmable%22
There are commercial products for this sort of thing.
                    John Nagle
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On Sat, 02 Sep 2006 18:21:52 +0100, E. Lee Dickinson

IF you're buying a commercial winch, limit switches, an inverter & standard ac motor will be about half the price. If you want to send video & power down as well then you'll need one with two winch drums & coil the cable round the second drum, at which point it may well be far cheaper to rig a pulley travelling horizontally to take up the slack.
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I should have been a bit more specific about the motion. It needs not only to go to a commanded location, but go to a NUMBER of commanded locations. Anywhere along its travel. So I definately need the encoder that's part of servo systesm.
The other additional item I would probably need with an AC motor is a brake, which I can also spec as part of a servo.
I've found what seems like the right solutions at www.automationdirect.com, which has to be the only industrial supply store in the world which lists prices on the internet. It's going to be expensive.. probably around $1500 to $2000 for all the parts I'll need. But it's going to be a permanent piece of kit, and I've been wanting to get into some good scenic automation stuff for a while, now.
We'll see!
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On Sun, 03 Sep 2006 23:35:17 +0100, E. Lee Dickinson

Fair enough. Brakes are an easily specified item on a servo or convential motor though. Do you actually need 2hp?
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I doubt it. Half that or less, I suspect. I'm going to mock up my idea with a 1/3hp scooter motor I have laying around, to get a sense for speed and power.
Thanks for all the support and recomendations, everyone.
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Keep in mind that too much power is infinitely better than too little power from a smoke and misery perspective. What better way to showcase your technical ability than with a string of expensive and dramatic failures that bring an ongoing production skidding to a halt.
A scooter motor????? I get this horrible image of a little engine revving shrilly and belching smoke as a scenery bar shudders momentarily before plunging destructively to the stage. :)
Maybe it's because I'm all old and jaded, but a properly manufactured winch with built on motor shaft feedback or multi limit cam sounds like it would be the one stop fix for your requirement. A little bit of PLC programming to detect an end of travel reference point and pulse count to other positions would be nice. It could also be used to detect a stalled motor quickly and shut things off.
Go pro. It's cheaper in the long run.
--
Clive Mitchell
http://www.bigclive.com
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He did say "mock-up", and this will certainly mock a proper winch :-)
--
}:-) Christopher Jahn
{:-( http://home.comcast.net/~xjahn/Main.html
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On Sun, 3 Sep 2006 23:26:15 -0400, "E. Lee Dickinson"

In the old days weren't verticle props and curtains counter weighted with sand bags? Counter weights would reduce the motor size.
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wrote:

You might call around some shops that install automation. We got a guy to help us out for free, because what we wanted to do was so "cool" compared to the boring factory automation he usually does.
--
}:-) Christopher Jahn
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On 02/09/2006 the venerable E. Lee Dickinson etched in runes:

The cheapest solution by far is to use a low power three phase motor and a single phase to three phase converter from suppliers such as Allen Bradley, Lenze. Reversible with very good speed control and plenty of torque at low revs. I would recommend a magnetic limit switch such as those used on roller shutters.

Slip rings are not a good idea for video. Better to use a helical coil of cable around one of the suspension wires. If you can't get the correct cable then simply thread some normal cables through one of those helical garden hoses that can be bought at any DIY shed.
--
John B

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That sounds a fun task. (!)
I guess it might be possible with compressed air and a "rabbit" but trying to push cable through manually could be a demoralising task.
--
Clive Mitchell
http://www.bigclive.com
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On Sun, 03 Sep 2006 18:29:06 +0100, Clive Mitchell

PUR jacketed cable & a hot water pipe much easier.
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On 03/09/2006 the venerable Clive Mitchell etched in runes:

Yes, it was quite fun nad took the best part of half a day. The one time I did a homebrew job was for a video link between the cab and trailer of an articulated truck. One of those electrician's nylon fishwires came in very handy. It's also very important to have plenty of spare space in the pipe!
--
John B

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You could use one of these maybe: http://video.google.com/videoplay?docidQ25780462773187994
Torrance
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I wouldn't recommend the use of a retro encabulator in a theatrical environment. The non sinusoidal pulse ramulator can cause back-flux into the subdemonial transfactoriser causing reactive burden on any power factor correction capacitors utilised on highly inductive loads. The resultant omnidermal lag can cause dimmer racks to misinterpret the zero crossing point or even miss it completely due to the sustained high frequency hysteresis at low voltages. This can make the lights flicker a bit when the encabulator is going through it's EMF purge sequence, which is disasterous if a show is in progress.
--
Clive Mitchell
http://www.bigclive.com
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Clive Mitchell wrote:

This, fellow RATS, is why Clive is my hero. Preach, brother, preach!
Regards, Bert
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Bert Morris wrote:

and yet there is a typo dear self emasculated noggin-heads. chris
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Call Creative Conners. www.creativeconners.com/prod_pushstick.htm
They have winches and controllers that will do this, you can rent his equipment. (the 12v signal will have to be run in an additional cable and spool system)
Personally, after designing several "cheap" winch and controller systems, the best way to support a show is to buy or rent a system that is actually designed for the theatre. Yes you can make off the rack industrial parts work. But nothing beats a well engineered theatrical controller for getting cues to work every time.
Well designed slip rings are very expensive, but I have liked the ones I've bought from www.polysci.com, electro-tec, and Insul-8.
Ben
E. Lee Dickinson wrote:

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