# NON-PERSONNEL Elevator



## rbashley (Sep 25, 2009)

I'm working on building an elevator in a trap door that goes from the stage floor to the basement. THERE WILL NEVER BE ACTOR ON IT!! And I have steel braces when not in use just in case a tech walks on top of it. There is NO WAY for a tech to get under it while it's in use. The new problem is that the designer wants to put about 200# on it for the first act and nothing on it for the second (no intermission to remove counter weight). I would like to motorize it. Any suggestions on low budget motor controllers? I'm looking at a 5Hp or 10Hp DC motor so that I can use it to move wagons later.


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## gafftaper (Sep 25, 2009)

TOS ruling from the Senior Team: It's okay to discuss motor control systems for elevators as long as discussion doesn't get into how to build the elevator itself. Stick to the OP's question and this thread will be allowed to continue. Drift into "how to build it land" and we will shut it down.


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## fredthe (Sep 25, 2009)

Thanks Gaff, I was holding off for that very reason.

The question is, what's your definition of low budget? I found a controller on Tecknowledgey - Motor Controllers, DC Series (mainly intended for such applications as electric vehicles) thats only $160. Not sure you're going to get much cheaper than that. But you can easily get to the $500-$1000 range.

Are you running the motor from batteries? If so, don't forget you'll also need a way to charge them. I'm assuming that you just want something that will allow you to control speed and direction, if not, let us know.

-Fred


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## Footer (Sep 26, 2009)

5hp or 10hp is way overkill for what you need. 1hp geared correctly would do what you need. I have lifted over 1000# onstage with 5hp. 

Few questions... what kind of power do you have on your stage? Single phase 120v, 208v 3 phase, 240v three phase? 

If you want to use an AC motor, you need to use a Varible Frequency Drive to control it. These can be picked up use, but even then it will cost you a few grand. Added to that you then need to control the VFD either using a PLC or limit switches (though limit switches should still be used with a PLC. 

There really is no cheap way to do motion control onstage. Its going to cost you at least 5k, and even thats lowballing it. 

Even after you get the motor you need to build a frame for it and mount it to a cable drum so you can use it to lift and pull. If you are going to use it for lifting you also have to install a brake. Its a lot more involved then just picking up a motor and bolting it in. 

There are other options for you though. One is electric or pneumatic actuators. You might also want to look into using a chain motor instead of counterweights. There are a few other options as well, but let us know what you money situation really is and we can get that figured out.


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## Traitor800 (Sep 26, 2009)

If 200# is all your lifting I would go with an ATV or Jeep Winch. I has all the parts you need and it can either be run off of an old car battery or you can find 120vAC-12vDC transformer to run it. Northern Tool has some decent prices on electric winches.
-Chris


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## icewolf08 (Sep 26, 2009)

I don't know what your budget is, but I would look into the Make It Move system by Creative Conners Inc. They specialize in creating automation systems for budget minded theatres. They would be happy to offer you professional advice on your project and can sell or rent you the equipment you need to run it. We have been using their systems for many productions and it works great. It has been updated (control software and such) since the last time we used it, and we haven't tried the new version, but it looks nice.


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## Footer (Sep 27, 2009)

Traitor800 said:


> If 200# is all your lifting I would go with an ATV or Jeep Winch. I has all the parts you need and it can either be run off of an old car battery or you can find 120vAC-12vDC transformer to run it. Northern Tool has some decent prices on electric winches.
> -Chris



NO. NO. NO. 

NEVER USE AN OFF THE SHELF BUMPER WINCH TO LIFT ANYTHING. 

Those winches are designed to PULL, not LIFT. What that means is they do not have the sufficient brake to hold the same amount they can lift. They are made to pull a jeep out of a ditch, and the worst that can happen is that the jeep falls back in the ditch if the winch fails. Chain Motors and winches designed for overhead lifting have brakes on them designed to stop 5x the load they can lift. You have to remember a winch moving 200# has to hold that 200# and deal with the forces exerted on the winch and cable when the load stops, otherwise known as a dynamic load. Truck winches are not designed to do that. 

We used a creative connors winch this summer to fly our plane for _The Drowsy Chaperon_ and it worked flawlessly. These motors are designed to do this type of thing. If you want to go with a turnkey solution, its the way to go. However, it will cost you about 2k for a 2 week rental. 

No matter which way you cut it, there is no way to add vertical motion control onstage on the cheap, I don't care if you are lifting a feather or a house. Horizontal movement is a bit easier onstage because you don't have to deal with keeping the load up when you stop. With a vertical system this is the major issue.


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## SHARYNF (Sep 27, 2009)

You just need to look outside of theatrical solutions a bit and you can find some reasonable solutions.

Here is a link to a DAVIT motor setup for lifiting a boat out of the water. Not all designs are just for pulling

Boat Lift Distributors : Hefty Hoist 3000 lb. Motor and Aluminum Gear Unit [AQUA3000] - $485.00 

with a 3000 lb rating, and some work attaching the unit, this should be able to do the trick

Sharyn


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## Footer (Sep 27, 2009)

SHARYNF said:


> You just need to look outside of theatrical solutions a bit and you can find some reasonable solutions.
> 
> Here is a link to a DAVIT motor setup for lifiting a boat out of the water. Not all designs are just for pulling
> 
> ...




Keep in mind with that solution you still need to install hard limits and E-stop switches at various points on the stage. Also, it runs very slow, 2.5ft a minute.


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## headcrab (Sep 28, 2009)

If you want to build the controller from scratch, or possibly the hardware, Automation Direct has nearly everything you need. They are aimed at the industrial automation market, but you should be able to get your stuff from them.


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## mjw56 (Nov 20, 2009)

this question is a little off topic but Footer mentioned a VFD for the AC motor. 
i recently took apart a broken ryobi drill (plug in not battery) and noticed that the wire runs through the switch and then to the motor. no converters of anykind. is that little switch a VFD or does that operate the motor under a completely different principle?


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## ajb (Dec 10, 2009)

mjw56 said:


> this question is a little off topic but Footer mentioned a VFD for the AC motor.
> i recently took apart a broken ryobi drill (plug in not battery) and noticed that the wire runs through the switch and then to the motor. no converters of anykind. is that little switch a VFD or does that operate the motor under a completely different principle?



Pretty much all tool motors are "universal" motors, meaning that they can actually run just as well on DC as on AC because of the way the field and armature windings interact. Since they're not synchronous (synchronous meaning that the motor's speed is tied to the frequency of the AC supply), they have the advantage that you can control their speed with simple pulse-width modulated DC (rapidly turning power on and off, the ratio of on time to off time determines the amount of power delivered to and therefore the speed of the motor) or phase-chopped AC power (just like a wall switch dimmer or dimmer rack). The trigger switch assembly in your drill in fact is most likely electrically equivalent to a wall dimmer, in fact, and you can use dimmers as very effective speed controllers for such motors. I'm not proud of it, but I once built a stage effect that used an electric drill with the trigger zip-tied down that was controlled just so.

EDIT: I should add the caveat that controlling an inductive load this way is less efficient than feeding it a proper sine wave and will cause excess heating, so transformers and motors should be derated by 50% or so when controlled by phase-chopping dimmers. Also, don't try it with any other sort of motor--some will tolerate it, others will get very, very unhappy--or in any sort of critical application. And finally, inductive loads will want a different sort of filter inline than resistive loads (like incandescent lights), so harmonics can be a concern and the reactance of the load can actually interfere with the dimmer's timing to various degrees.
 
VFDs are much more complex beasts designed to run more temperamental AC motors, and are essentially fancy switch-mode power supplies. They take the incoming power, convert it to DC (if it's not DC already), smooth and filter it, step voltage up or down if necessary, and then output through an H-bridge (to produce the positive and negative halves of the sine wave). The output is switched at somewhere around 10KHz-200KHz and pulse width is modulated according to a sine function of the desired frequency to generally approximate a sine wave. If the modulation frequency and resolution are high enough and the output smoothing well designed the output can get very close to a true sine wave, although cheaper units produce a distinctly stepped 'sine-ish' waveform.


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## mjw56 (Dec 10, 2009)

cool thanks. i bet no one at my engineering firm knows that much detail and we spec VFD's with explosion proof submersible trash pumps all the time for sewage pump stations


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