How to built a motorized turntable...


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Ok so this is a follow up to a previous post about which motor i should use to power it...

Well now the question is the best way to build it. I have seen a few of them....pu a few road tours together...but i'm having a hard time trying to figure out exacly how to put it on paper.

Any Suggestions would be greatly appreciated on how to build one of these.

It will have rougly a 20ft diamiter.
How high do you need it? I would suggest depending on weight every 60 to 90 degrees have some dumb casters to take up some of the weight. just fastern them so they have the proper angel. If it will be higher than a few feet what about a trussel /\/\/\/\type construction and have that rest on the caster and put the deck on it
I suggest going to the library and checking out a few stagecraft and/or scenic design books. I've seen turntable design sketches in some books. I'm pretty sure they followed the same principles as platform construction (that is spans no greater than 4 feet for plywood). And as ship pointed out on the other thread, there is the issue of the center pivot.

Another consideration is whether you need to conceal the sides of the revolve from the audience. If cable-driven, the cable will show, and if direct driven, the drive wheel may leave a mark on the side.

Do people have to stand on it? if not could you fly it in and put the motor on the pipe in the ceiling and then just make sure when you lower it that its a fraction off of the ground and have a black rope going to it or something. I doupt any of this will work if people are on it but if they're not then that may work.
I checked the book that I have (forgot to write down the title/author – its pretty generic). It notes that two key items in the revolve are getting the point of rotation at dead center, and getting the wheels exactly perpendicular to the diameter. For the center pivot, the example showed a short pipe bolted to the floor. A smaller diameter pipe connected to the revolve fit into the large pipe. (There may well be some standard "hardware" for this.) I'm also under the impression that there in no weight bearing down on this center pivot.

To access and install this center pivot, the construction must be such that there are no structural members through the center point of the revolve. The text also implied that a built-up stage floor is often used around a revolve to hide the drive system. The same text also implied that the cable driven systems are used on relatively small revolves, but the text didn't suggest other options either.

I suppose one could even mount the motor and wheel assemble under the revolve such that the drive wheel was on the floor and pushed the revolve around. But, it seems that the electrical cable could get twisted with that arrangement. And if something goes wrong with the motor/drive, it may act as a brake, preventing manual operation.

Lubrication of that center pivot bearing will be needed and may make a mess of the floor below.

The revolve will probably need a lot of wheels. Partly so that you don't have long spans, partly to minimize friction, and partly because the revolve/set weight will be so heavy and each wheel assemble can only take so much weight.

Another detail that was not clear at all was how to make the curved sides of the revolve. (Okay, its probably standard carpentry, but its way out of my league.) If they bear the force of the drive mechanism, they will need to be sturdy and hold the circular shape.

Another thing to consider when you design this is how you will assemble it. Unless its highly modular, you may have to build it in place. You'll have to have the wheels in place before you add the platform/structure. Remember, the weight of this is going to be at least 1,000 lb, and probably more. If the wheels are to be added after its built, be sure to design the revolve so that it can support itself if jacked up and blocked up on any edge. (That's also safety issue, working beneath it if its blocked up. Probably a really bad idea.) On the other hand, if you take the modular approach, make sure you can fit the pieces onto your truck/through the door/up the steps (if built off-site) and that they are "light" enough to be handled by whoever you have to move them. More that I think about it, you probably need to assemble the wheeled frame and pivot first, then make sure it turns and that all the wheels are adjusted right, and then add the top deck.

As some other people have mentioned there are stage books with this in. I have an old second edition copy of "Scene Design And Stage Lighting" by W Oren Parker, Harvey K Smith. They are now upto edition 8 or 9. Some courses use this as a standard text so it might be in a local library. Or else you can buy it on etc. I had a quick look and only Oren Parker's name is on the latest edition with some other authors.

My edition has a good segment on revolves/ turntables and shows basic construction details.

I know you were talking about motorised revolve but this book shows another option. As well as stage crew pushing the revolve around there is a third option. Instead of an electric motor you can use a hand winch and cable. Basicaly under the revolve there is a circle of plywood near the circumference of the revolve. The continuous winch cable is taken one full turn around the plywood then through a spring loaded pulley tensioner upto an off stage winch / windlass . The winch can be single or double handed. It will take quite a few turns of the winch to move the revolve so you could always use the football players or someone who is a grinder on a yatcht.

Before some of you say this is too old fashioned it is still in use today. A community theatre I am involved with is getting one built for their next show. The director has used this method in the past. The theatre has a flat floor so with this method the stage won't have to be built up as high as if a motor was under there.

Some of the advantages are it's safer then an electric motor as the human operator can see if there is a problem and stop it straight away. An electric motor will just grind away until somone hits the stop button .
It needs less hight as you don't need to fit a motor under it
Easier to maintain, just the revolve it self, the cable, pulleys and the winch.
There is no wiring of a control box that would have to be done by an electrican. The school might be happier with this then an electric revolve because of safety, maintenance , and cost issues.

This is just an idea. But at least the book should answer some of your questions.

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