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Revolving stage

Discussion in 'Scenery, Props, and Rigging' started by charlesb, Jan 15, 2009.

  1. charlesb

    charlesb Member

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    Hello,

    I am Charles Belcher from Dallas, Texas. I do an Extreme Christmas Light display at our house during the season.

    This year had around 60,000 lights synchronized to music via Light-o-rama software. We had around 300 channels of conventional LOR micro processor units and 3200 channels of DMX controlled automated fixtures, Colorado 3 wash lights, fog, snow, laser and LED X-Curtain eve and roof lights.

    We also had a 10' wide x 7' high LED tube grid pixel mapped to a Martin Maxedia Media Server which rendered text, flash files, jpg's and wmv files.

    The finale' of the 17.5 minute show was a live performance by Mr. and Mrs. Santa Claus on a 20' x 8' stage we built on the roof of our house!

    OK, you get the idea.

    Here is a link to this year's production:

    [media]http://www.vimeo.com/2735546[/media]

    Here is a link to the 2007 production.

    [media]http://www.youtube.com/watch?v=B_AKkAwxuo8[/media]
    ____________________________________________

    Now, on to the question. I want to build a 20' diameter revolving stage in the front yard for 2009. It will be divided by flats with a Christmas scene at the top of the show, then revolve to a setting with Mr. and Mrs. Santa Claus in rocking chairs, a fireplace and a Christmas tree. They will start decorating the tree then segue into a full blown rock and roll dance.

    The question is how best to accomplish this task. Specifically, I need to know what how to marry a DC motor to a gear reduction system in order to get to 1 RPM, then how to marry that to a rubber wheel on the rear outside of the turntable.

    I have a 20' diameter circle truss I can use and I can thrown some 12' truss on top of that as a sub-structure for the staging decks. I will cement a 3" or 4" pipe into the ground as the receiving unit for the pipe which will attach to the center hub.

    The center hub is the next problem for me. Without custom fabricating something out of aluminum and spending a bunch of money, is there something in the world, possibly another industry, that could work for this?

    I will need electric on stage, but I will run a line up through the center for that, then turn the set one direction then back the other direction to keep the cables from twisting. I will also use wireless DMX to control on stage fixtures.

    Any help would be appreciated.

    Thanks in advance.

    Charles
     
  2. Van

    Van CBMod CB Mods Premium Member

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    Occupation:
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    "Use the search, Luke"
    You should be able to adapt stuff from the drawings I posted in the Wiki on revolves.
     
    Last edited by a moderator: Jan 15, 2009
  3. lieperjp

    lieperjp Well-Known Member

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    Speaking of which... your drawing says, "See attached PDF for list" but there is not an attached PDF...
     
  4. charlesb

    charlesb Member

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    Van,

    Yes, I searched and read every thread on revolving stages I could find on this forum. I haven't seen the WIKI yet. I will look for that. The WIKI link above doesn't work for me.

    I didn't find any details on a gear box for reducing the DC motor RPM's down to 1 RPM, nor any detail on the mount and drive for the tire.

    Point somewhere and I am all over it.

    Charles
     
    Last edited: Jan 15, 2009
  5. Footer

    Footer Senior Team Senior Team Premium Member

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    I don't know if you will find your answer here too easily. What you want to do is a semester course at most grad schools. I am also concerned with the use of truss as your support structure. From the looks of it, you want the entire revolve to be supported by the center pivot? You might want to reconsider that, the amount of forces on that center shaft would be astronomical. You might want to look into some engineering books on how to slow down a motor. It is fairly easily done, but depending on your motor and what kind of reducer it already has on it, it can be easy or hard. 1 RPM is VERY slow in theatrical terms. To do what you want to do, you need to really know the engineering behind it. Let alone, attaching it to your roof. I hate to say this, but it might be time to hire someone to produce some drawings for you, or someone to help you along in person. Revolves are hard to build on a stage, automated revolves are even harder. I could not imagine doing it on a roof.

    The only piece of advice on the build is... www.mcmaster.com
    If you can build it with that, it can't be built.
     
    Last edited: Jan 15, 2009
  6. charlesb

    charlesb Member

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    Footer,

    This stage will be in the front yard. The 2008 stationary stage was on the roof.

    I understand your advice, but I would like to further clarify my idea. If it can be done in such a way as to not have to build a stage upon which you would place a turntable platter on those 60+ upside down casters, that would be preferred. So, my idea was to use this 20' diameter (20.5" box) truss that is available to me and put a center hub, cemented in the ground. I do understand the dynamics of that and figured I would or could place (4) tire assemblies on the underneath outside edge of the stage to help keep support and balance.

    If this idea is not feasible, then I will move to the upside down caster method. There is a McMaster in Dallas and that is certainly a good idea.

    Thanks for your thoughts.

    Charles
     
  7. Van

    Van CBMod CB Mods Premium Member

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    Is there a specific reason you want to use a DC motor as opposed to a three phase reversalbe motor ?
    As far as looking for advice on slowing it down to 1 rpm that's a simple matter of math. Motor reduction gears are availible at most places like McMaster or Grainger.
    The size of revolve you are talking about makes me think about the revolves used at a lot of auto shows, large diameter, heavy load, Lot's of expense.
     
  8. derekleffew

    derekleffew Resident Curmudgeon Senior Team Premium Member

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    [​IMG]
    Turntable Rentals by B and R Scenery

    Should be no more than $100,000 to buy, or $20,000 to rent.:lol:
     
  9. charlesb

    charlesb Member

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    Van,

    I can't use a 3 phase motor because the electrical service to my house is 240v single phase and I don't want the expense of a transformer on top of the necessary expense I will already have. I agree, the revolve will be much like an auto revolve.

    I want to try to utilize the 20' aluminum circle truss and the plywood that is available to me for free. That way I will not have to buy all of those casters to do a platter. I know this will be very heavy; probably around 3,000lbs and I am very concerned about it working from one center hub.

    Even if I cement a 4" pipe sleeve in the 6' in the ground, the stress will be enormous but, do you think that putting four tires in the N,S,E and West positions under the outer edge will work?

    I am just trying to bounce ideas off of people who have done these kinds of things before to see if I am barking up the wrong tree or not.

    Charles
     
  10. charlesb

    charlesb Member

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    That might be a little too much for a Christmas light display at my house!;)

    Charles
     
  11. Van

    Van CBMod CB Mods Premium Member

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    No I don't hink 4 tires is going to cut it. 8 maybe.

    There are reversing single phase 240 motors as well as a unit called a "Roto-Phaser" which give you 208 3 phase.
    I would not drive it with a tire, I'd be much more inclined to wrap a chain around the perimeter.
    I'm trying hard not to be Pedantic, I don't know what your level of Production Automation experience is, but have youi also taken into consideration all the control issues, dead-man switches, torque limiters, redundant control systems, and personel to properly and safely operate this unit? It sounds as if you are used to putting on quite the production. but to keep someone from losing a leg your're gonna need an operator and / or spotter.
     
  12. jwl868

    jwl868 Active Member

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    20' diameter structure in the front yard - you might want to check your zoning laws, too.


    Joe
     
  13. scenerymaker

    scenerymaker Member

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    You don't need incoming 3 phase power. A variable frequency drive will take your 240 volt, single phase power and turn it into the variable frequency, variable voltage control you need to drive your motor smoothly. Woodworkers frequently can get bargain saws, planers, etc. from factories that require 3 phase power that they don't have. Some of these guys get a bit extreme about thier hobby and the toys they want. Try looking in the power tools section of woodnet.net for some ideas on power. This is my first post on this forum, so if it's not appropriate to post about other forums, I apologize. Let me know and I won't do it again.

    I'm in the middle of building a 25 foot diameter turntable to hold up to 80 people (7 tons). I'm driving it with a VFD running a pair of 2 hp, 440 V, 3-phase motors from a 240 V, 1-phase source. Your dilema struck a chord with me.
     
  14. charlesb

    charlesb Member

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    Van, Joe, Scenerymaker

    Van,


    1) The only people who will ever be on stage are my wife and I; aka Mr. and Mrs. Santa Claus
    2) I have been in the concert sound and lighting business all my life both as a technician and business manager
    3) The chain drive idea is the second idea I had. I just thought I would have fewer parts and fewer things to go wrong with a tire drive
    4) I intended to place a dead-man's switches on both sides of the center wall as we will be on both sides of the stage when movement occurs and other than that power to the stage will be off. We will always be on stage during movement and no one will ever be on stage when it is not moving.
    5) If I have to go with 8 tires to support the stage weight, then I might be better off from a cost standpoint to go ahead with the 60 + upside down caster design.
    6) I can see this will be a project both on paper and in the front yard, which by the way...

    Joe,

    The small little town I live in (suburb of Dallas) is behind our Christmas show. In fact, the police increase the patrol on our street, the utility department turns off the street lights near our house so the Christmas lights don't get washed out, the public relations manager sends us a "Thank you for your community involvement" letter each year, etc.

    I built the 20' wide x 8' deep stage on my roof this year without a permit, so I think I am going to ignore the permit route.

    Scenerymaker,

    Your project is quite a bit larger than mine. Thanks for the wood working link.

    ___________________________________________

    Now both Van and Scenerymaker have suggested using an AC motor rather than a DC motor for this purpose.

    Can I ask why?

    Charles
     
  15. cdub260

    cdub260 CBMod CB Mods

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    At the Pageant we have several rolling turntables that we often incorporate into pieces of scenery that need to revolve. The largest of these was for a 12 ft. diameter rotating set. For each of these we have used a 1/2 hp, 90 volt dc motor. I don't recall off the top of my head what level of gear reduction we use, but we use a chain and sprocket set-up in order to connect the drive motor to the hardened steel shaft that acts as the center hub of the turntable. If you size you set up your gear reduction and drive sprockets right, and use a DC motor speed controller, you should have no trouble getting your speed down to 1 RPM. I have three sources foe these, Mcmaster/Carr, Grainger, and Minarik Automation and Control.

    Now for getting power to whatever we have built on the turntable, we use a brush system built around the center shaft. I don't see any reason why you wouldn't be able to do the same thing for your power. One caution here. Make sure you have enough clearance between your chain drive and the turntable disk for your electrics or you will have at best, an unexpected, but brief addition to your light show, and at worst, someone dead. You really need to consult with a Qualified Electrician if you decide to use a brush system for your power. That said, I believe this is a better, and if properly set up, safer solution than running a cord through the hub and limiting yourself to 180 degrees of rotation.

    A for your tire drive idea, we also have a permanently installed turntable, 20 ft. in diameter that uses this method. It uses 2 synched 3 phase, AC motors (I don't recall the horse power off hand.) and some serious gear reduction to drive 2 trailer tires. This equipment sits in a 3 ft. high crawl space under the turntable. Gala Systems built this turntable for us 25 years ago at a cost of tens of thousands of dollars. We recently did an upgrade of the control system, which also ran into the several thousand dollar range. Given what you're trying to do, I believe the chain drive will be a better, and more economical option.
     
  16. Footer

    Footer Senior Team Senior Team Premium Member

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    Re: Van, Joe, Scenerymaker

    Your center hub should not take weight. It is there just to act as a pivot. If it takes weight, it runs the possibility of bending or sheering off your pillow blocks. The amount of forces working on the center hub is pretty huge. Also, unless your yard is perfectly flat, you will get bucking to occur in the revolve. My suggestion is to build a perfectly level platform with a large load limit, say 500-1000 PLF. Then on top of this you will construct the revolve. There is a lot of force at work here, don't try to take shortcuts. I have spend 3 weeks building automated revolves for the stage and thousands of dollars, and still not got them perfect, and thats at theatres that already had the automation gear.
     
  17. charlesb

    charlesb Member

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    C.W. and Van,

    The last two posts offered some real insight into my project. Thank you both.

    In my business, we use Cat Entertainment for our generator rentals and they have a master electrician on staff here in Dallas that would help me figure out the brush configuration, but we are only going to turn the revolve one half turn each show anyway, so the cable up the center hub is really not a problem from a physical standpoint. In between shows, we will turn the revolve back to the original position.

    _________________________________

    C.W., I have a 90v dC motor with controls already so if I could use that, it would be easy for me and cost effective as well.

    Another guy I know who does an extreme Christmas display uses Merotac slip rings for electric to his carousels. Is this what you are referring to when you suggest using brushes to transfer electric?
    __________________________________
    Van,

    At work, we have scaffolding, aluminum I-beams and plywood forever so building a laser leveled stage with a large load-bearing surface would not be a problem.

    I am going to Northern Tool and Harbour Freight today to nose around and look at their spindle/hub assemblies before I give up on this idea and go to the caster design.

    Charles
     
  18. scenerymaker

    scenerymaker Member

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    Re: Van, Joe, Scenerymaker

    Short answer: I think they work better.

    Long answer: I've spent the last 40 years in industrial automation, so controlling 3 phase motors is pretty straightforward. Assuming you have enough power in your motor, if you want your motor to run at half speed, you run it at half frequency, thanks to the VFD. The problem I've had with DC motors is that when you add load to it, it slows down. There are DC speed controllers that monitor speed and increase the voltage to maintain speed. I've tried this twice, and both times, that speed control was unstable due to the varying loads I was imposing on them. They got replaced with AC drives that just worked.

    By the way, I'm driving mine with a 1/2" chain that goes all the way around the table. The chain is pulled with 2 gearmotors that are 90 degrees apart so they tend to locate the table and reduce the stress on the center pivot. It is sized to turn half a turn in 20 seconds, starting and stopping slowly so I don't pull the floor out from anybody standing on it. Some scenes will have 2 or 3 people, at least one will have more than 40, and some will have people jumping on or off as it turns. That big variation in load, along with my bad DC experience, are what made me use an AC system.

    Good luck.
     
  19. scenerymaker

    scenerymaker Member

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    Another thought on a spindle. Go to a junkyard and get the back axle out of a front wheel drive car. Most of them have a bolt-on spindle with a bearing-mounted flange the wheel bolts onto. The bigger the car, the stronger the bearing assembly will be. My bearing is on the other end of the technical scale. I have a 2" post welded to a disk taped to the floor. The theater owner won't let me bore holes in his stage floor. With most of my lateral load taken in the drive motors, I don't think it will be a problem. The bearing in my structure is a square hole lined with greased 2x4s ! I've used greased wood in outdoor sets before and they really work well.
     
  20. jwl868

    jwl868 Active Member

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    Re: Van, Joe, Scenerymaker

    Things got ugly near my neighborhood.

    Controversy outshining Christmas light display in Ross

    Joe
     

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