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Rotating Set

Discussion in 'Scenery, Props, and Rigging' started by Synchronize, Sep 9, 2008.

  1. Synchronize

    Synchronize Active Member

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    My highschool is putting on Fools this Fall and me and the other set builder have been faced with a building a rotating set. Short background of my highschool. We are in the middle of a corn field; this place has no love for the arts. Or Drama Department has no funding coming from the school so everything we put into a show is what we make from the last show. Also, our stage is in an auditeria (auditorium/cafeteria) so we have nothing fancy.

    We're both definatly excited about it just because its something new but I was wondering if you could throw your ideas at me.

    The other guy just wants to build a platform that has a central pivate point with casters around the outside of the platform so that it can be pushef from the back side by stagehands. I am a little more ambitious and want to make it motorized. Idealy there would be a such thing as a DMX turntable that we could just run to the lightboard and controle on a channel or two; unfortunatly I don't think there is one. I'd still like to run it through the lightboard so that I can control it back in the booth. I was thinking either something like this mounted in the center with casters around the outside and have that turntable spin the set on the casters. But better yet I was thinking having this in the center and casters around the outside with some sort of motor driven caster that spins it on that turn table.

    Now, keeping in mind that we have limitied to no funding and that this will probably be coming out of my pocket just because I think it would be cool, what do you all think?
     
    Last edited: Sep 11, 2008
  2. Footer

    Footer Senior Team Senior Team Premium Member

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    The other guy has it right. First and foremost....

    NEVER EVER RUN AUTOMATION OFF OF DMX. YOU CAN USE DMX TO SIGNAL A CUE FOR AUTOMATION, BUT NEVER DIRECTLY CONTROL AUTOMATION WITH DMX. IT WAS NOT DESIGNED FOR THIS PURPOSE.

    Depending on the size of the revolve, its going to take some serious power to get this thing started, much much much more then that motor will provide. I usually will run turn tables off of at least a 3hp 208v 3 phase motor with a 30 to 1 ratio and geared to at least a 5 to 1. To correctly automate this so it will actually run can easily cost you 10k.

    I would build the platforms as usual, if you want to use swivel casters that makes this easier but not as versatile. Do a search for revolve and look for a post by Van, he has a great set of drawings for an easy revolve.
     
  3. cdub260

    cdub260 CBMod CB Mods

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    Actually, if the turntable isn't too big this could be done with a 1/2 hp, 90 volt, DC motor. This will probably run in the realm of $300. The gearing is the tricky part, and beyond my area of expertice, so I won't give any advice on that aspect. The controller for this set-up is a little pricy coming in at just under $600.

    We've been using this set-up for rotating scenery for at least 20 years, probably longer. All of our rotating set bases have been in use for a minimum of 15 years, with only minor maintenance issues. Of course, the largest piece of scenery we've ever rotated with this set-up had a 12 ft. diameter, so there are limitations. Also be aware, that while I use this set-up I've never actually built one.

    If this is a set-up that you're going to keep, it may be worth the hassle and expense. If it's for a single show, never to be used again, I wouldn't bother trying to motorize the turntable.
     
    Last edited: Sep 9, 2008
  4. bobgaggle

    bobgaggle Well-Known Member

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    I designed a production of Jekyll and Hyde that had a 24' turntable in it. It took four "ninjas" to move it, but I didn't have to deal with a motor and a gearbox, and controls and safeties. Seriously, when you build anything, simpler is better. The more variables you have, the more likely you're going to hear, "Oh, S**T! ITS NOT MOVING" coming out of your headset midshow.

    But since you want to do it, get some help. Seriously, you're going to kill yourself if you try to build it and rig up the motor everything else yourself. Do any of the "drama dads" have any experience with this sort of thing? Get their help.
     
  5. Van

    Van CBMod CB Mods Premium Member

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    As stated DMX is not the proper control protocol for this project. I'll try and post a decent response this evening.
     
  6. Synchronize

    Synchronize Active Member

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    First off: HAHAHA drama dads? Last time somebody's dad came in he ended up knocking three bicks out of a wall in the props closet. We don't let them come around anymore. My friend and I do everything when it comes to tech at our school. We build the sets, I take care of lights, he takes care of sound. I really want to make this amazing because my friend has put so much time, sweat, and blood into our productions over the past three years. Its his senior year and after this he will probably never touch theatre tech again.

    [user]bobgaggle[/user] mentioned too many variables. The thing is that I like to be in control. I think that three stage hands pushing this thing in a circle is more variables than something that I can control in the booth. Either way, if something goes wrong it will end up falling on me and my friend.

    Unfortunatly it cant be a permanent thing becaue our next production is Oklahoma! and there isnt exactly need for a rotating barn center stage...

    But anyway I appreciate the help that has been given so far.
     
  7. cdub260

    cdub260 CBMod CB Mods

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    Most of our rotating scenery is on rolling wagons with the motor and gearing built into the wagon.
     
  8. Van

    Van CBMod CB Mods Premium Member

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    This is exactly why trying to control a turntable from the booth is a great way to get someone killed. A motor driven turntable is a great thing and if done correctly a really cool thing but if done incorrectly it's an accident waiting to happen. The Turntable for Les Mis, for instance, is operated from backstage, there is a deadman switch, if the ASM, or stagehand in control senses any problems one release of pressure on the button stops the whole thing dead. Turntable control systems can often times incorporate computer aided cueing systems, but they are always controlled directly by a human with a hand on a switch.

    Now you can argue that you'll have perfect control over the turntable by using DMX as an indexing system, in a manner similar to the way a colorscroller works, but you'd be wrong. As I said earlier I'll be hapy to post some more in depth help later on, but please if you are going to make an arguement that you can remotely control a turntable via DMX, then let me know now and I won't waste my time trying to stop you.
     
  9. DaveySimps

    DaveySimps CBMod CB Mods Premium Member

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    As stated before, controlling a turntable for DMX or a long distance is just not safe under any condition. It may seem like we are caught up on this, but you cannot understimate how much of a safety concern proper control is.

    ~Dave
     
  10. soundman

    soundman Well-Known Member

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    Lets say you don't you use DMX and attempt to do it another way.

    First and foremost you will need a motor. I didn't catch the size of the turn table but 2-5 HP should be the ball park for a small to medium turn table Depending on the drive method. Now you need a way to connect the motor to the turn table. Keep in mind that a motor with out a controler will rotate at 1750 RPM with very little torque. Now you need a gear reducer to slow it down and add some power. Ideally you will do some math and figure out the best one for your application but the idea should be to keep the motor running as close to 60 hertz as possible. Speaking of hertz that is how you control the speed at which the motor runs, by changing the frequency the AC is being fed to it at. The lower the frequancy the slower and more whinny the motor.

    Spining a tire against it like a carnival ride might be the easiest way but that is not always ideal. Roller chain to a sprocket is another way but that puts alot of torque on a little area. not the best way. All of the options so far do have the benefit of endless rotation though.

    Most people opt to use a winch system. This has the disadvantage of only being able to do as many revolutions as there is cable on the drum but aircraft cable is cheap so it is not a big deal. For the turntable I was a part of we had the steel come off the drum through a set of tensioning pulley around a disc which drove the pulley through another set of tensioning pulleys and back on the winch.

    Now that you have a set up that can make something move you have to come up with a way to control it. We opted for a dual system. We encoded the winch drum and used limit switches on the platform. The limit switches were there to provide the hard stop commands and the encoders were there to help govern the speed. Our set up could not stop quick enough from the speed the director wanted to just use limit switches and the PLC (programmable logic controller) was not relable enough to count all of the clicks on our home built encoder. The way the code was written was that when the go button was pushed the motor would turn in the proper direction as determined by a switch at the control board. It would accelerate to not jar the performers on it and run at that speed for so many counts. After it hit the correct number of counts it would start to decelerate until it hit the limit switch when it would turn off. The reason to go with an encoder over a simple clock was that the speed was changing and the encoder would always give us a rough position of the turn table and a closk would be a guess.

    We choose to use a PLC because my accomplice and I have had some experience writing ladder logic and could get one for free which saved us about 2 grand. We had E stop switches set up on either side of stage and next to the stage mangier. The switches would kill power to the 120 volt line feeding the PLC which would kill the run signal to the drive unit. Upon reboot the PLC would reset to the default state NOT sending its last command.

    Does that sound simpler than have 3 people spin something? Its so much easier to tell a human to do something than to try and come up with a machine to do it. There is a reason the machines haven't had their uprising yet.
     
    Last edited: Sep 11, 2008
    Van and (deleted member) like this.
  11. scottmcleod

    scottmcleod Member

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    +1 to the DMX Comment. Not what it's used for. Put an ASM/stagehand on a headset, and give them the controller for it.

    http://www.google.ca/url?sa=t&sourc...b-ozf7vyck_1oUVWA&sig2=kY8Ng3pATo-xszhh0IOnIA

    That link should take you to a PDF of a 20' turntable, Motor, & Construction drawings.

    Dan K. R. Potts (MIT Post-Grad Researcher) is the source of the document.

    The maths are sound.

    Budget: 3000$ Is what I'm building mine on, not including wood for the deck.

    The entire stage in my theatre has to be built up 8". We're building the rotating deck over 4 days with a total of 3 carpenters in November. Electricity is being run in December, and the automation should be operational come January 1st when the director needs it.

    Don't cheap out with automation. Do you have the insurance or liability when someone comes and sues you because their son/daughter lost an arm/leg/finger/whatever when your contraption ran amuk because of a "bad cue".

    2 people is not enough to run a show involving a mechanised revolve. Don't be a freakin' superhero. TEACH some people stagecraft, and direct them. That's what a TECHNICAL DIRECTOR does.

    I learned VERY quickly in high school that that's a short way to have a show crash and burn. Build a team, train them well, and you'll have more than enough people "doing things for you" to feel like you're still "in control", if you're such a control freak.

    Just my $0.02, and from my experience.

    -S
     

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