Another Large Revolve on a Budget

[scrogers]

Yeah, some quick math does demonstrate the possible cost savings by reducing the overall revolve to 20ft. Unfortunately, there are some design decisions that have already gone into action that sorta require the 24ft span to move.

Obviously my costs have increased, but it sorta will be what it is...

As for driving the unit, I'm looking at some decent rope with knots at intervals that will be looped around blocks attached to the edges... and then people to pull... hard. I'm hoping with nearly 140 rather high-quality casters and some strong backs, I can get it to spin with at least some load on it...

 

[BillConnerFASTC]

Look at cost of double 3/4 ply versus more casters. My instinct says that with optimal spacing of 90 casters you'd be fine. I'd star with a ring maybe 10 or 11" from perimeter and maybe an inner ring of 3 casters - guessing that is 27 - 30" diameter. A couple of pieces of umhw supporting center - donuts around the pivot - and inner ring jumps out quite a bit. Lots of CAD fun playing with layouts.

I didn't see caster load rating - do you know? I'd think 4" was up around 300-400 minimum but would have to look. I suspect span will still be limiting factor.

 

[scrogers]

Well... I was starting to consider that as well. So, it looks like it's only about $125ish difference between getting two layers of 5/8 (one disk of AC facing down, one disk of CD facing up), and two layers of 3/4 (same deal, one disk of AC facing down, one disk of CD facing up). The only other reason I had been thinking of 5/8 over 3/4, is weight. By my calculations, two layers of 3/4 will be about ~450lbs more than two layers of 5/8. Since I know I'm going to be driving this thing manually, I was/am trying to keep the table weight down as well... but... maybe it's worth the extra 450lbs for the strength(?).

The Bleutec 4in rigid casters I'm using are rated to "330lbs" each, so I think (hope) I'm ok there...

Years ago when I was involved in constructing (but not designing) a 16ft revolve, I'm sure we only used about 50-ish casters. This thing was the 3-layer "bread-and-cheese-sandwich" method though, and was quite solid... but was REALLY heavy (still have horror stories about trying to load-in and strike the thing safely).

Yeah, after spending some more time with the math and CAD... if only 90 casters are used, there are a number of spans that are certainly over 3ft. I guess another option could be to get a few more casters to bring the total more like 100, and up the layers to 3/4 ply, and then play around with the spacing some more to sorta try and get the best of all worlds(?).

I'm having all sorts of fun playing with the caster layouts in CAD... and looks like there may need to be more.

 

[microstar]

I recently built a 7' diameter turntable with double 3/4" ply disk and 3.5" rigid casters attached to the bottom. A ball-bearing weight-supporting center hub. 3/4" rope spliced in a loop going around 2x4 "spokes" attached to the underside. Idler wheels to keep rope tensioned. About 350 pounds of load plus the turntable weight. Took one medium-sized person a fair amount of effort to rotate 180 degrees each time. It will be interesting to see how much force it will take on a rope to turn your 24' turntable. You might consider a backup plan to the knotted-rope method.

 

[scrogers]

I recently built a 7' diameter turntable with double 3/4" ply disk and 3.5" rigid casters attached to the bottom. A ball-bearing weight-supporting center hub. 3/4" rope spliced in a loop going around 2x4 "spokes" attached to the underside. Idler wheels to keep rope tensioned. About 350 pounds of load plus the turntable weight. Took one medium-sized person a fair amount of effort to rotate 180 degrees each time. It will be interesting to see how much force it will take on a rope to turn your 24' turntable. You might consider a backup plan to the knotted-rope method.

microstar,

This sounds very similar to the drive system I'm thinking (hoping) to make work on mine. Basically- spliced rope loop with knots, 2x4 blocks (or spokes) on the bottom of the disk, a couple tensioners... and then strong people. You say 3/4" rope, but what type did you end up with? I'm planning to do 4in casters facing up (attached to the floor). I've read about someone making essentially the same thing we're talking about work with a 16ft turntable (made of two layers of 1/2in ply though), and "1/2in rope" but not lots of detail there either. That was described as "easy for a young girl to spin very quickly with no load on the table" and "very manageable for a couple people even with set pieces and 15-20 people." Granted, I'm talking a much bigger disk, and potentially lots of set pieces and people...

I don't know, I'm now leaning more toward dual layers of 3/4 ply for strength, but do worry a bit on how well this "rope method" will scale up. I can easily throw people at the problem though, but, there's only so much room and so hard they can pull in sequence...

I know your table is much smaller than what I'm talking about, but any insight into how that worked out is appreciated. Thanks.

 

[BillConnerFASTC]

How much does it have to turn, as in how many 360 degree rotations until it can go reverse? And how fast do you envision?

 

[microstar]

microstar,

This sounds very similar to the drive system I'm thinking (hoping) to make work on mine. Basically- spliced rope loop with knots, 2x4 blocks (or spokes) on the bottom of the disk, a couple tensioners... and then strong people. You say 3/4" rope, but what type did you end up with? I'm planning to do 4in casters facing up (attached to the floor). I've read about someone making essentially the same thing we're talking about work with a 16ft turntable (made of two layers of 1/2in ply though), and "1/2in rope" but not lots of detail there either. That was described as "easy for a young girl to spin very quickly with no load on the table" and "very manageable for a couple people even with set pieces and 15-20 people." Granted, I'm talking a much bigger disk, and potentially lots of set pieces and people...

I don't know, I'm now leaning more toward dual layers of 3/4 ply for strength, but do worry a bit on how well this "rope method" will scale up. I can easily throw people at the problem though, but, there's only so much room and so hard they can pull in sequence...

I know your table is much smaller than what I'm talking about, but any insight into how that worked out is appreciated. Thanks.

I did not put any knots in the 3/4" natural Manila rope for my 7' turntable because with the small diameter, I figured the rope made sharp enough bends that it wouldn't be necessary, and we encountered no slippage. The idlers had to be strategically placed as well due to legs for the platforming spanning over the turntable unit. I think you will want the knots in yours. To me, one of your big problems (besides the friction of all the casters/getting all the weight moving) would be keeping enough tension on the slack side of the rope as all the pulling happens on the drive side. You also might have to bolt the 2x4 spokes in place as a lot of force will be applied, especially to the first one the rope knot makes contact with as it comes off the turntable. Unlike meshed gears, you really don't know how many knots will actually contact spokes as it's being pulled. The photos are from "The Game's Afoot".

 

[dbaxter]

Well, since we're talking turntables and "The Game's Afoot"... Our 7' turntable is (currently running) made from 3/4 ply with 1x4 radial supports where the casters are mounted. There are 12 six 1/2 high casters. Since this only goes back and forth, I had the luxury of fastening the pull rope at one point. The rotating wall has a pivot at the top to keep it square to its surround. One person can pull it while two people ride. The problem of keeping tension on the non-pulled side was solved by running the rope through a tear-drop shaped scrub brush mounted to the end guide.

 

[scrogers]

Thanks for the replies and sorry for the delay, I've been traveling.

So, as for rotations, the table needs to be able to spin a full rotation in a minute, at minimum. To be honest, I know my directors would like a full rotation in as little as 30 seconds, but they are also (slightly) aware this is likely unreasonable.

It certainly needs one full rotation in either direction, with preferably no restriction on direction or rotations. I've been involved with a revolve using a double-wrapped wire rope cable before, and honestly, the overlap/rotation issues with the cable... were huge.

Thanks so much for the Games Afoot pictures. The idea of the rope attached to the disk also good... but unfortunately not going to work for us with the multiple rotations likely needed.

I'm hopefully going to make tensioners out of boom-bases attached to the floor with short pipes. I actually read a similar description of this and then sliding PVC over the schedule 40 pipe like a pulley. I also agree that I'm going to likely need the knot method so it doesn't slip, and I may need to bolt, rather than screw the spokes/cogs to the disk due to the forces on the knots and blocks.

Unfortunately, I'm out of town and not going to be able to truly mock this up for a bit. I'm CADing this all out as much as I can for now and plan to put this all into action shortly.

Thanks again for any ideas and/or recommendations.

 

[lwinters630]

Hey all,

First, big thanks to all those out there who help post on these forums for all things tech theatre. CB has been an invaluable resource to me for years, and now looking for a little guidance...

I'm looking to build a 24ft turntable/revolve and I have experience building a couple different versions of a turntable, but am intrigued by a design I've recently come across.

http://theaterdad.blogspot.com/2011/06/how-to-make-revolving-stage.html

Before I found the above link, I was essentially planning for this sort of design. Two layers of ply oriented 90 degrees from each other to form the disk over a bed of casters on the floor in concentric circles. I'd love some input on a few things from this "theaterdad" method.

1- The above method is designed around a 16ft revolve, but, think it would essentially "scale up" to 24ft?

2- Theaterdad used two layers of 1/2in ply, and was all about keeping it light. I too am concerned about weight, for reasons mentioned next. I was planning to go 5/8in since mine will be larger. That said, it seems like eveyone does 3/4, but I'd love the weight savings of 1/2 or 5/8th. Thoughts?

3- What I really liked... was his manual operation method. The "cog rope cup" as he describes, basically takes a knotted rope and loops it around the edge of the disk, and catches on several "cogs" or grooved 2x4's (see his description). I really like this idea because- a) it's relatively inexpensive, b) appears rather simple, and c) is operable from off-stage, BUT, would it scale up to a 24ft table? Rope suggestions? Any huge risks?

4- I'm planning for rings of casters at 3', 6', 8'8", and 11'4" from the center. My questions is, if I use the commonly used pivot method described all over CB of two pipes with flanges set within each other with grease, will the center of the disk have enough support? I have used a car hub and bearing assembly before as well as a slightly different take on the sleeved pivot, but the sleeve doesn't provide any support (vs say a car hub). No one has had issues with not enough central support? I'm just worried with a central ring of 3ft of center (so 6ft diameter) from center and 5/8in ply.

Basically, I really wanted to go full automation for this show, but after pricing our everything from rentals, to construction etc, motorized automation is just out of the cards for us this show. That said, again, this rope method looks slick... but will it just be impossible to move a 24ft table, let alone how about when I get a thousand pounds of scenery on it, and 20-30 people(?). The blog mentions how easy it was for "a 16 year old girl" to spin the empty table at ridiculous speeds, and still no issues for a strong person when loaded up... I just worry I do all this... and then cannot move it...

Again, thank you all in advance for any thoughts, but just trying to get some experiences or input on the above ideas before I'm deep into a design that's potentially problematic from the beginning.

I am attaching some drawings that I received from Van but his links do not seem to be active, and other sources (can't remember which). I was going to build Les Mis revolve but ended up doing a different layout. I hope these help. Note fixed casters will work best.

 

[scrogers]

Thanks for all the PDFs and images. I had come across these plans before here on CB. While this does help with some numbers of casters etc, I think I have decided to go with the two large disks out of two layers of ply rather than the pie wedge method.

I have finally gotten to spend a lot more time in CAD, and I think I have finally settled on two layers of 3/4in ply (seams at 90 degrees) up from the 5/8in I was thinking. I have also upped the casters from 90 to about 120 (and now nearly double from my first post here). As noted from the posts above, to really get EVERY span below 2ft, the total number of casters is nearly 140, however, with a few adjustments, and allowing some spans to go only a few inches over 2ft, I can get the casters down to just about 120, and still feel very comfortable with the spans (I think the largest span is like 26-27in, and it's only in a few places).

So, I think with two layers of 3/4in ply (one AC one CD), and 120ish casters, this thing will be pretty sturdy.

As for moving the table... there will have to be some trial and error, but I'm planning to attempt this "rope knots and cup" method described here in this post and see where it gets me. Like I said, I can easily throw a couple strong back at this, but I can't really make motorized automation fit into the budget... so manual operation it will be. Hopefully, with the high-quality fixed (not swivel) casters placed regularly, with decent ply, and strong rope (and people) I can get this to move...

Thanks again for all the help and comments, and I always welcome more thoughts and ideas. Actual construction will begin early next week... and hopefully things come together...

 

[dbaxter]

Looking forward to the post-show report.

 

[scrogers]

Post installation update-

Well... The table is in. 122 casters on plates to make them at 7.5in so the final deck height is 9in off the floor. Two layers of 3/4in ply (AC lower CD upper) seams at 90 degrees. The thing is a beast, but from the brief initial testing.... it appears to work pretty well.

Issues? Plenty, mostly around the fact that the ply, while decent quality (and from a good lumber yard), was not PERFECTLY flat (especially the upper CD layer). This meant that every seam basically had to be "sewn" up with 1-1/4in screws every 3-6in throughout the entire table. I knew there would be lots of screws, but honestly, it took thousands to make the bottom smooth, which just took a considerable amount of time. We eventually got the process down using leveling blocks underneath, cut at the correct height, then placed on seams and 4-corner junctions with people standing on the deck while screwing everything together.

The caster assemblies were monotonous to assemble, as was the placement and alignment. The greased-pipe-sleeve-center-pin method seems to work well and most of those processes went according to plan.

Then... the maiden spin was a glorious thing. It is heavy, but one person (just pushing the edge) could easily spin 6-8 people, and two people could get it moving dangerously fast. The hardest part is getting it started while loaded down, but once moving, it doesn't take much to keep it moving and it actually takes quite a lot to get it to stop once moving fast. I have yet to really load it up, but all in due time.

Next big thing (aside from all the other rolling stair units, set pieces, and things that go on the table and set) for the table, is the movement. I am going to attempt the "rope and cup" method mentioned before, done by mounting 6in grooved 2x4 blocks spaced every foot or so with rope threaded through and knots every 3 ft or so spliced into a loop. I'll then make some tensioners and a return loop... and hope.... I'm thinking some nice 1/2in polyester rope since it doesn't have much stretch(?) As always, I welcome any suggestions...

Anyway, thanks again for all the interest, help, and support. I have some pics which I'll try and get up of both the process and mostly final unit... Crossing my fingers on the rope drive, but will also update down the line as that comes together...

 

[bobgaggle]

once you get it going can you post some photos of the drive system? I've heard of the knotted rope method but never seen it in practice...

 

[microstar]

I think I would opt for 3/4" instead of 1/2" as it would be much easier to grip when pulling.

 

[scrogers]

Well... it happened and ultimately, was a huge success. We succeeded in building a 24ft revolve with an off-stage manual rope drive system that was actually incredibly reliable, smooth, quiet, and relatively easy to operate (with strength). The drive system was ultimately about 120ft of 5/8in multiline rope spliced into a loop, with knots tied about every 6ft. I then made a series of notched blocks (really a beveled 2x4 sandwiched with ply), or "cups" as some have described, bolted around the edge of the table, and then two sheaves coming off the table and a third large return sheave providing tension. There were initially a number of issues with keeping the rope from slipping off the sheaves, but with the proper alignment, tension, and various guides in place, the system became rather reliable.

With nothing on the table, it was rather easy to move with one person. I credit this to the high quality (and number) of casters we used in the construction. This also made the unit nearly silent to operate. Once you loaded it up, the hardest part was getting it to start... and then stop. Ultimately, we had two strong backs operating it the entire show. While a little difficult to calculate, we estimate it was moving between 7000-8000 lbs at it's peak (2 times in the show- about 30+ people, plus 8-10 rolling pieces of scenery, wagons, and staircases, plus the weight of the disk itself). With that much weight, it didn't move very fast, and it took a lot to go, but go it did, and it was honestly slick. The final locking/brake system was constructed out of a 1.5ton scissor car jack placed 2-3 feet under the disk that was operated via a long shaft to a drill (to raise and lower the jack). This made it extremely stable when not moving.

The whole thing was dismantled yesterday back into 4x8 (or smaller) sheets and is safely stored until the next time we need it...

Thanks to all who guided, suggested, and chimed in here, it's a great place. I'll put in a couple pics below and am happy to chat more with anyone... It was quite the process. Thanks again!

 

[microstar]

Thanks for the wrap-up! Glad it worked out well. Great pictures.

 

[BillConnerFASTC]

Nice work!

 

[jwh78]

Do you have a pic of the car jack break mechanism?

Sent from my Nexus 7 using Tapatalk

 

[scrogers]

Do you have a pic of the car jack break mechanism?

Sent from my Nexus 7 using Tapatalk

It's sorta hard to see it exactly, but basically there is a low-profile scissor jack slid underneath the disk, and then a long shaft to a drill. This would raise and lower the jack in a couple seconds. In these pics (below) the unit is pulled out rather close to the edge, however, when we were actually using it in the show, the jack was probably more like 1.5-2ft under the disk. I actually took a little bit of sticky-backed sand paper and put it under the base on on the top of the jack to increase the friction when expanded. Not sure it did much, but couldn't hurt.

It actually worked amazingly well, and the only issues we had were the makeshift drive shaft coming apart at the point where the hook attaches (a drill press and bolts fixed this), and then one bit of operator error where the jack hadn't been lowered all the way and a passing block caught on the driveshaft while the table was spinning and sucked the whole unit under... This actually bent/mangled things up a bit, but we were able to hammer it all back into shape, no harm... Things were running smoothly by the time we hit the shows.

Hope it helps.