Stage Revolve help!

tjmaller

Member
I was wondering if anyone had any advice on how to rig a manual set up for turning a stage revolve. I would prefer to get a motor but I don't know what kind of motor to buy that would be strong or safe to use. The revolve is about 18' in diameter and would have some set on it nothing too heavy and usually max 10 actors.

any advice would be greatly appreciated thank you.
 

MRW Lights

Well-Known Member
We're gonna need A LOT more information, but we can start with 18' + people and a set is gonna be a heck of a wheel to move. Depending on your construction... you'll need to map your wheels, static non swivel and get the angle right measured off of your center point. Additionally... how fast do you need it to move? (the answer is you don't want it to move fast), does it need to move in both directions? What's under it and is it level? What's it going to be made out of? Do you have room for operators around it and is it okay to see them? If motorized do you have the appropriate room for a drive system and the equipment with which to drive it?
 

tjmaller

Member
the entire turntable is built out of plywood. it only needs to rotate at walking speed. the stage is level and stage is 38' x 42'. needs to move in both directions. set on top will be mostly fake boulders and fake trees in the centre. The operators will need to be behind it as it will be on stage. I was hoping to run a chain or rope to an off stage position so that it could be turned from offstage. but A motor would probably be ideal. the wood will be 1.5 inch thick plywood. No trap system.
 

RonHebbard

Well-Known Member
Premium Member
the entire turntable is built out of plywood. it only needs to rotate at walking speed. the stage is level and stage is 38' x 42'. needs to move in both directions. set on top will be mostly fake boulders and fake trees in the centre. The operators will need to be behind it as it will be on stage. I was hoping to run a chain or rope to an off stage position so that it could be turned from offstage. but A motor would probably be ideal. the wood will be 1.5 inch thick plywood. No trap system.
@tjmaller Casters down, mounted on the turntable and wearing circles into your stage deck?
OR
Rigid, non swivel, casters mounted face up on your deck and wearing the underside of your turntable??
Toodleoo!
Ron Hebbard
 

MRW Lights

Well-Known Member
1.5" thick plywood would be roughly 3lbs /sq ft and with an 18' diameter is approximately 250 sq ft... meaning 750 lbs for the deck alone, without framing and without anything on top of it.... That's gonna take some muscle to move smoothly.... also your stage is only as level as when you try to put an 18' turntable on it... is it impossible no, but I think you're going to need a bigger conversation about feasibility, manpower and the goal of the turntable before diving into making it happen...
 

JAC

Active Member

bobgaggle

Well-Known Member
I think the most important question is, who is this for? High school, community theater, pro?

In high school I built a 20' turn table like you describe, two layers of 3/4" ply (OSB actually, don't recommend). I used home depot rigid casters mounted on 2x6's that were screwed to the deck. I used off cut 2x6's stacked up with a hole drilled in it and a chunk of 1 1/4" sch 40 pipe for a center pivot. This thing was my crowning achievement....it was terrible, but it worked, kind of.

It took 4 guys to move it. They laid down US in all black and just hand over hand grabbed the edge and pulled, we kept the lights off of them. I wouldn't recommend you do it this way, but for everyone involved it was awesome and we had the biggest turntable than any other school in our county had done (these things matter when you're a teenager)

however you go about it, harder wheels mean less friction, but more noise. Buy the best quality casters you can afford, and make sure you take your time to accurately plot your points so the caster plates are tangent to the circle.
 

Van

CBMod
CB Mods
Premium Member
Turntables are a PITA! if you do some searching on here you will find a TON of articles and post from folks talking about the advantages of motorized or not.

Some of the things to consider beyond all the questions and issues above:

If you want to drive the turntable one of the best ways is to run a roller chain around the perimeter. If you want to operate the turntable manually you will need a hand crank capstan of some kind. I suck at math but I know the formulas; you are going to need something that gives you enough mechanical advantage that you can easily manually operate the crank. <small drive sprocket> You are going to need something that drives the chain fast enough to move the circumference of an 18' diameter disc at walking speed, or 3-5 MPH <or 5-9 Kph, if you are @RonHebbard > (that's going to take a BIG sprocket)

One of the biggest issues with moving a turntable is that initial moment of inertia. A mass at rest wants to stay at rest. There are a ton of formulas that can tell you exactly how much force it's going to take to get that turntable to start moving then how much force it will take to maintain it at a given velocity. Most of them calculate a best case scenario and therefore you can add 25-50% to the force necessary due to friction. Suffice to say it take a big force to get 700 pound of plywood to start to rotate.

One good design I saw just had a two wheels sandwiching the outside edge of the turntable. there was an adjustment that would pinch the wheels together tighter to get better grip. Try as they might they could not get the wheel to stop screeching when they started it up. this is because a drive motor in a situation like this requires a soft-start. Remember that Electric motors are Instant Torque; instantly throwing 3HP at a wheel will make it skid on anything. <Another discussion to be had: AC or DC motor? PWM drive? etc, etc, etc.>

*** Safety ***
Say you've done all the calcs and you are ready to assemble your system. You've decided to drive it with a motor. Your voltage supply is correct. Your motor size is sufficient. You have a soft start motor controller or you have a ramp-able PWM programmed to provide the right start up torque. What about safety? As stated there are formulas for this but 700 pounds moving at 3-5 MPH <5-9Kph if you are Ron> has a butt-ton of kinetic energy. Now imagine you are an actor stumbling around in the dark and he manages to wedge himself between a set piece on the revolve and a flat on the stage. "Put the Candle Back!" Yeah you need brakes/braking system/ dead man stop. If it's an electric set up you should have at least Two dead man buttons in addition to the one on your operating console. If you are manually operated you need to devise a dead-man system in which all operators can communicate and stop the disc at a moments notice. Either way you HAVE to instruct the Actors and Stagehands of the danger involved and the situational awareness that MUST be maintained while working on on around a revolve.

I Operated a small manually operated revolve for a show back when I was a kid. Had whole ninja costume complete with Balaclava I had a pole that locked into a socket on the floor so I could push around the back side and the audience wouldn't notice me. It was small Only 10' in diameter and didn't have much on it and I was young strong and stupid. Yep, had an actor step between to opening for the revolve and the edge of the wall opening. Damn near killed him and me stopping that thing but I did it.


I don't know what kind of budget you have or where you are located but you might want to check out "Creative Connors" or one of the other moving scenery companies. They can supply you with the motors and control systems, Hell, they could probably rent you a whole revolve system, but I don't know what their pricing is like. I'm sure there are other folks in different regions that offer similar services. I'm hoping of of the other members chimes in.
 

bobgaggle

Well-Known Member
One good design I saw just had a two wheels sandwiching the outside edge of the turntable. there was an adjustment that would pinch the wheels together tighter to get better grip. Try as they might they could not get the wheel to stop screeching when they started it up. this is because a drive motor in a situation like this requires a soft-start. Remember that Electric motors are Instant Torque; instantly throwing 3HP at a wheel will make it skid on anything. <Another discussion to be had: AC or DC motor? PWM drive? etc, etc, etc.>
I'm familiar with that problem. I had a thought experiment a while ago about solving that in the home brew method, never had the opportunity to try it.

Usually your wheel is fixed directly to the output shaft of the gear reducer, I wonder if the wheel was on its own axle along with a v belt pulley. In between the wheel axle and bearbox is the v belt onto which you rig a tensioner/clutch. Maybe its just another pulley on a lever so the operator can gradually ease tension onto the thing and give you a poor man's soft start. Benefit is if he lets go there's no more power to the turntable, so de facto dead man. (could also be a detriment)

I don't know what prices are lately, maybe you don't save any money buying all the parts and labor to develop vs buying a variable speed controller...


Side note, when I've done the tire drive we used one wheel on the outside, axle pointed to the grid. 1/4"x 8 steel flatbar welded around the periemeter provided a skirt to hide the wheels and something to push the tire against. Didn't have an issue with deflection when we pushed the tire tight against it.
 

tjmaller

Member
I'm familiar with that problem. I had a thought experiment a while ago about solving that in the home brew method, never had the opportunity to try it.

Usually your wheel is fixed directly to the output shaft of the gear reducer, I wonder if the wheel was on its own axle along with a v belt pulley. In between the wheel axle and bearbox is the v belt onto which you rig a tensioner/clutch. Maybe its just another pulley on a lever so the operator can gradually ease tension onto the thing and give you a poor man's soft start. Benefit is if he lets go there's no more power to the turntable, so de facto dead man. (could also be a detriment)

I don't know what prices are lately, maybe you don't save any money buying all the parts and labor to develop vs buying a variable speed controller...


Side note, when I've done the tire drive we used one wheel on the outside, axle pointed to the grid. 1/4"x 8 steel flatbar welded around the periemeter provided a skirt to hide the wheels and something to push the tire against. Didn't have an issue with deflection when we pushed the tire tight against it.
thanks for your response but I am unsure of some of the terminology here to understand what is a gear reducer, v belt pulley and bearbox
 

bobgaggle

Well-Known Member
thanks for your response but I am unsure of some of the terminology here to understand what is a gear reducer, v belt pulley and bearbox
Its pretty common for regional theaters to have a DC motor, variable speed controller, and various gearboxes (not bearboxes, sorry for the typo) laying around that the master carp will cobble together into an automation rig for some widget that the director wants to magically move. Gear boxes turn the high rpm, low torque input from the motor into low rpm, high torque output for the needed application. Quite often, for a turntable, the simplest drive method is to slide a tire onto the output shaft of the gear box and find a way to shove that motor-gearbox-tire-assembly really hard against some concentric part of the turn table to get it to move.
 

tjmaller

Member
Its pretty common for regional theaters to have a DC motor, variable speed controller, and various gearboxes (not bearboxes, sorry for the typo) laying around that the master carp will cobble together into an automation rig for some widget that the director wants to magically move. Gear boxes turn the high rpm, low torque input from the motor into low rpm, high torque output for the needed application. Quite often, for a turntable, the simplest drive method is to slide a tire onto the output shaft of the gear box and find a way to shove that motor-gearbox-tire-assembly really hard against some concentric part of the turn table to get it to move.
thank you what I need help with is what to get to drive the revolve or how to set up a manual crack system. What type of motor? gearbox etc
 

tjmaller

Member
Turntables are a PITA! if you do some searching on here you will find a TON of articles and post from folks talking about the advantages of motorized or not.

Some of the things to consider beyond all the questions and issues above:

If you want to drive the turntable one of the best ways is to run a roller chain around the perimeter. If you want to operate the turntable manually you will need a hand crank capstan of some kind. I suck at math but I know the formulas; you are going to need something that gives you enough mechanical advantage that you can easily manually operate the crank. <small drive sprocket> You are going to need something that drives the chain fast enough to move the circumference of an 18' diameter disc at walking speed, or 3-5 MPH <or 5-9 Kph, if you are @RonHebbard > (that's going to take a BIG sprocket)

One of the biggest issues with moving a turntable is that initial moment of inertia. A mass at rest wants to stay at rest. There are a ton of formulas that can tell you exactly how much force it's going to take to get that turntable to start moving then how much force it will take to maintain it at a given velocity. Most of them calculate a best case scenario and therefore you can add 25-50% to the force necessary due to friction. Suffice to say it take a big force to get 700 pound of plywood to start to rotate.

One good design I saw just had a two wheels sandwiching the outside edge of the turntable. there was an adjustment that would pinch the wheels together tighter to get better grip. Try as they might they could not get the wheel to stop screeching when they started it up. this is because a drive motor in a situation like this requires a soft-start. Remember that Electric motors are Instant Torque; instantly throwing 3HP at a wheel will make it skid on anything. <Another discussion to be had: AC or DC motor? PWM drive? etc, etc, etc.>

*** Safety ***
Say you've done all the calcs and you are ready to assemble your system. You've decided to drive it with a motor. Your voltage supply is correct. Your motor size is sufficient. You have a soft start motor controller or you have a ramp-able PWM programmed to provide the right start up torque. What about safety? As stated there are formulas for this but 700 pounds moving at 3-5 MPH <5-9Kph if you are Ron> has a butt-ton of kinetic energy. Now imagine you are an actor stumbling around in the dark and he manages to wedge himself between a set piece on the revolve and a flat on the stage. "Put the Candle Back!" Yeah you need brakes/braking system/ dead man stop. If it's an electric set up you should have at least Two dead man buttons in addition to the one on your operating console. If you are manually operated you need to devise a dead-man system in which all operators can communicate and stop the disc at a moments notice. Either way you HAVE to instruct the Actors and Stagehands of the danger involved and the situational awareness that MUST be maintained while working on on around a revolve.

I Operated a small manually operated revolve for a show back when I was a kid. Had whole ninja costume complete with Balaclava I had a pole that locked into a socket on the floor so I could push around the back side and the audience wouldn't notice me. It was small Only 10' in diameter and didn't have much on it and I was young strong and stupid. Yep, had an actor step between to opening for the revolve and the edge of the wall opening. Damn near killed him and me stopping that thing but I did it.


I don't know what kind of budget you have or where you are located but you might want to check out "Creative Connors" or one of the other moving scenery companies. They can supply you with the motors and control systems, Hell, they could probably rent you a whole revolve system, but I don't know what their pricing is like. I'm sure there are other folks in different regions that offer similar services. I'm hoping of of the other members chimes in.
creative is way too expensive
 

tjmaller

Member
I think the most important question is, who is this for? High school, community theater, pro?

In high school I built a 20' turn table like you describe, two layers of 3/4" ply (OSB actually, don't recommend). I used home depot rigid casters mounted on 2x6's that were screwed to the deck. I used off cut 2x6's stacked up with a hole drilled in it and a chunk of 1 1/4" sch 40 pipe for a center pivot. This thing was my crowning achievement....it was terrible, but it worked, kind of.

It took 4 guys to move it. They laid down US in all black and just hand over hand grabbed the edge and pulled, we kept the lights off of them. I wouldn't recommend you do it this way, but for everyone involved it was awesome and we had the biggest turntable than any other school in our county had done (these things matter when you're a teenager)

however you go about it, harder wheels mean less friction, but more noise. Buy the best quality casters you can afford, and make sure you take your time to accurately plot your points so the caster plates are tangent to the circle.
high school low budget
 

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