# Air cylinder help



## freedomverse (Feb 20, 2013)

I am building a well for a production I am helping with. I have the frame finished but am stuck on getting the movement needed. I think that air cylinders could be my answer after looking at the thread by footer, "Who says only God can make a tree?". This is what this well needs to do:



it splits in half to become two curved stone looking walls
it must roll and then not roll so the actor can sit or stand on it.
it must come together to form a well.
it needs to be easy enough for the women actors to do all shifting.
it is 17" tall and has a 5'6" diameter


Here is a very rough sketch:



My first idea was to install a electric scissor jack to the underside of the top of each well half. The bottom of the jack would attach to a piece of plywood with casters attached. When the jack was activated the casters would lower and lift the well. It did work but had two problems. First it was loud. Second, the jack was made cheaply and it's built in switch failed to stop it in time and it got stuck in the bottom position and the gears broke the next time the up button was activated. Since I cannot risk this happening on stage I am moving to plan b, pneumatics.
I guess I have a couple of questions. Each half of the well will be about 30 pounds or so after the art department gets done adding their rocky looking-ness to it. If I go with these air cylinders do I need one for each caster or is it possible to make one cylinder move a three casters mounted on a 2'x1.5' plywood? I think I only need about one inch of movement.
How do I determine what size tank I would need to be able to move each peice about 6 times each performance? 
Any other suggestions that might help. This would be my first dive into air powered stuff. I am also open to other methods of making this work.
This site has been so helpful the last couple of years as I have built props and scenery. Thank you all for sharing your knowledge. This is my first post.


----------



## JChenault (Feb 20, 2013)

Instead of going hi tech, have you considered a lift jack? If one side of the unit is not seen this might be a much easier , cheaper, quieter solution.

The wiki entry is not a great illustration. I will look for a better diagram ( or draw one myself)


----------



## Footer (Feb 20, 2013)

Pneumatic casters are not exactly an easy thing to do. There is a lot of math needed to figure out how much air is needed: number of moves, size of cylinders, weight of piece, PSI of system, the list goes on. On top of that, building the lifters is not exactly easy. The ones I did for that project are not the best example of how to do this. It worked, but there are many better ways. Wagon brakes, wedges, a lift jack... all good ways to do this. The way we did it worked, but that is with a professional scene shop and a LOT of trial and error.


----------



## viking33 (Feb 20, 2013)

Norcostco does sell a per assembled package for pneumatic casters. A little on the pricey side but the tutorial does a great job of explaining things. Automation direct usually has the best prices on any pneumatic cylinders.


----------



## freedomverse (Feb 20, 2013)

I thought of making a built in lift jack for each side. I have done this successfully before for other props. The only hurdle I can't seem to get over is how to operate it when the well halves are put together. I can't have the actors reaching way in to operate it because it is put together in full light. If there is a clever way to accomplish it I would sure consider it.


----------



## MPowers (Feb 20, 2013)

There are so many ways of solving this that it is hard to know where to begin. HOWEVER!!! A word of caution. You need to plan and install any pneumatics before the "art" department gets the unit. They need to build their art around your skeleton, not the other way around. You really don't want to try and "stuff their turkey".

A few methods you can use are:

-Pancake cylinders with a stem caster on each one. Unit frame rests directly on the floor. 
Pneumatic Cylinders - C-Series (SS, Compact) Overview
Cylinders ~ Fabco-Air, Inc. ~ Gainesville, FL 
WESCO Swivel Caster, 3 1/2 In, Mold On Rubber - Parts - 1GAC6|108457 - Grainger Industrial Supply
-Shop built diaphragm caster lifts. Unit frame rests directly on the floor. If you are interested and have time, I can provide plans to build.
-cylinder driven "stops" or rods to play against the floor or a caster wheel and act as a brake. If the wheels can't roll or turn, the unit is stopped.
-Hinged casters with a cylinder to push it level or tilt it off the floor. 

For casters, one source: Casters, Caster Wheels, Chair Casters, Discount Casters, Swivel Casters. Don't stint on the caster size or cost if possible. Larger casters roll easier and deal with rolling over small things on the floor. Smaller casters tend to swivel quicker but have more rolling friction and small things on the floor can act as a door stop. 

Operation is usually by a self contained air tank or CO2 cylinder and manual or electric valves. such as:
PARKER Manual Valve, Toggle, 1/8 NPT, 3 Way - Manual Air Control Valves - 3FEC1|414811000 - Grainger Industrial Supply
The valve is as small as a light switch and designed to be installed behind a panel so only the toggle sticks out. Easily hidden in any scenic unit. 
CO2 comes in high pressure cylinders so a very small cylinder can provide a lot of volume of gas at a usable pressure. 

Because your unit is so small and light, you don't need large casters, 1" to 2" diameter wheels would handle the load. If you have a talent riding the unit while in motion that could change. Also, the double crescent shape might mean 3 - 5 smaller casters spaced around the outer edge of each half circle to balance and support the load. 

Hope this helps get you started. More questions??? Ask.


----------



## freedomverse (Feb 22, 2013)

MPowers, I am inspired by the hinge idea. I am contemplating the use of smaller casters than what I have now like you recommend and attaching two of them together with a steel plate which will be attached to hinges which will attach to the well. If I make two of these (4 wheels for each well) and bolt another steel piece coming out perpendicular to each one that meets in the center I wonder if I could make the whole thing work using one Pneumatic cylinder for each well half. It is a bit cumbersome to explain so here is another example of why I am not in the "art" department.



The cylinder will need to have a certain stroke length which I will need to figure out. I am figuring one of the steel pieces will be longer and above the other so it can push it down.
I am also very interested in exactly what a diaphragm caster lift would be? I can't picture it. I would love to know more about it.

I am trying to button these plans down this weekend so I can order the appropriate parts.


----------



## MPowers (Feb 23, 2013)

It's probably too late to start diaphragm lift units for your project however, I'll try to explain what they are. 

Diaphragm caster lifts are a shop built device made from 6" schedule 80 PVC pipe, 3/8" thick PVC plate, and 1/16" thick sheets of gum rubber. There is a bit of machining work, and building them takes a bit of time. However it is an investment just as buying good casters, they will last many years and many shows. The Smallest thing I ever moved with them was a folding dressing screen for "Night Music" with a pneumatic knife gag built in, 50# total. The heaviest was a 10,000# motorized drawbridge stair for "La Mancha" (Rotating Rep, no fly system-the stair had to be completely self contained and the stair and it's operating mechanism had to be moved to and from the stage in 30 min or less, every day for 6 weeks.) One use that is similar in need to yours was a door and window unit for Irene Molloy's hat shop "Hello Dolly". Two windows flanking a practical door. The girls arrive and find the door locked. Minnie has a bright idea, the girls spin the unit au vista (spelling??) and now they're inside and can unlock the door. They hit the little toggle switch and the unit sets down on the floor, wheels up and is sturdy enough for the door to function easily. 

Not sure if I can describe it well, but I'll try. The 6" pipe is cut into 2" +- sections and 1/4" sections. The plate is cut into 8" squares and 6" discs to just fit inside the pipe, the gum rubber is cut into 8" discs. Using an edge slotting cutter on a router, machine a slot 1/4" wide 3/16" deep, about 1/4" from one end, around the inner circumference, of one of the 2" pipe sections. Cut a 2"-3" section out of the smaller piece of pipe you cut so it can act as a snap ring and fit in the groove you have machined.
Drill a hole in one edge of the square plate about 3" deep and a small connecting hole from one face to meet the first hole. Place the rubber on the square plate hole side, place the 2" pipe section on the plate with the groove away from the plate. Fasten the plate to the 2" pipe with the rubber captured between. Now if you push air in the hole on the side of the plate, it will inflate the rubber to fill the inside of the pipe section. Drill bolt holes in the corners of the square plate(to bolt the caster lift to the scenic unit) drill bolt holes in the 6" disc to match your caster. Bolt the caster to the disc. Insert the disc into the 2" pipe section and place the snap ring in the groove. Now tap the hole in the edge of the square plate for 1/8 NPT and screw in any of the types of push to connect air fittings, run a 1/4" air hose from the lift unit to a valve and to an air tank. Now when you open the valve, 10psi of air will provide 250 pounds of lift. Run the return port on the valve to an air muffler and when you toggle the switch "off", the air in the lift unit is pushed out by the weight of the unit pushing down. The entire unit is only about 1" thicker than your caster, doesn't require a lot of space under the scenic piece. Recommend working pressure 10psi = 250# lift, the load rating on an average theatre caster. Cost about $25 per unit not including the caster and air system components. 

I would be glad to post the detailed instructions with illustrations, here on CB if someone would teach this old geezer how to post an article.


----------



## freedomverse (Feb 23, 2013)

MPowers, I am super interested in trying this idea. I think I get the idea and am confident that I could do it. As they say a picture would be worth a thousand words. Could you post a picture?


----------



## soundman (Feb 23, 2013)

I first saw Air Lift Casters as MPowers is describing doing summer stock. Turns out they were made 'famous' in a TD&T article. Attached is the most helpful page from that article. I was able to build twenty over a week end with one other person. Maybe a man hour in each unit, we never needed to do a second batch but I bet we could get it down to around twenty minutes after all the jigs were built. I think we ordered all the parts from McMaster Carr. For air we used three main sources, direct connection to the scene shop air supply for any move we could, a 5 gallon air tank from the hardware store for any move that happened A Vista with a large unit and lastly we used a 68 CI 4.5K PSI air tank used in paint ball on a low profile unit.


----------



## MPowers (Feb 23, 2013)

freedomverse said:


> MPowers, I am super interested in trying this idea. I think I get the idea and am confident that I could do it. As they say a picture would be worth a thousand words. Could you post a picture?



Check the last two lines of my post.


----------



## scenerymaker (Feb 26, 2013)

Does anybody have a source for the gum rubber?


----------



## Footer (Feb 26, 2013)

scenerymaker said:


> Does anybody have a source for the gum rubber?



McMaster-Carr


----------



## freedomverse (Mar 7, 2013)

Here is an update of how things are turning out with the well. 

I actually picked up some schedule 80 pipe from a guy on craigslist with the intention of building the air lift casters that MPowers suggested and kindly provided incredibly detailed instructions. Since cost was nearly the same as my hinged caster idea and a lot less work was involved I decided to go with the hinged casters. When there are less deadlines to meet I can hardly wait to build a few air lift casters because they are incredibly versatile and hardly take up any vertical space.

Here are some pictures of what I did. I took them when mostly done. As we speak the artists are making them look like they are made of stone. The tank was actually mounted in the corner of each near the flat side, not in the center as pictured. It is plumbed to a air regulator and then to a pneumatic switch and finally to the cylinder itself. The exhaust is plumbed to a cheap valve to control the flow and then to old plastic container with a rag inside to control the noise. It is whisper quiet and works... well.  

I'll post a picture of the final product when it is finished.


----------



## MPowers (Mar 7, 2013)

Very nicely done! Congrats! This is an age old caster method with pneumatic power applied instead of stage hand foot power.View attachment 2 Mechanical caster lifts 4x8.pdf


----------



## BSchend (May 14, 2013)

This thread has been great for ideas and variations on the concept of lift jacks/air casters/etc. (Note to moderators, if you wish I can restart this question in a new thread if needed)

Most of the discussion for these items has centered on moving just the set piece with no actors. Would any of these methods still be viable with the additional weight of actors and still allow allow for movement? Total weight while on wheels would be roughly 150 of platform/wagon and 300-400 for two actors.

The reason I'm asking is that we will be doing a production of Big River in the fall, which has a pivotal "raft" used in multiple scenes. The raft has to be easily moved while on stage by the two actors playing Huck Finn and Jim with poles while riding the raft. Due to the constraints of the theater and stage the "raft" will have to serve double duty and be "docked" with a portion of the set when not in use. Using zero throw style casters for ease of movement causes a problem when the raft is supposed to be stationary. Wagon Brakes/Toggle clamps on one end could possibly do the job, but would still allow for a good deal of movement at the non-braked end.

The scenes where the "raft" is used as a "raft" begin quite quickly and going from stationary to rolling must be initiated by the actors (and vice versa when needed). I've toyed with the idea of 4 air lift casters with a simple toggle switch that one of the actors can hit to lift or lower the raft. I've never built such items before and don't have much history with non-wood fabrication. When I saw the solution freedomverse used for his well, I thought that might be perfect. An air tank hidden in a permanent "crate" on the raft could hide the tank and pneumatic cylinder and be activated just as easily as individual air casters (with less failure likely).

That falls to the question of whether on a roughly 4'x6' (no larger than 4'x8') carriage of 6" depth (essentially just a plain rolling platform) would the hinged method above hold the weight while in use? Also would the cylinder have enough pressure to keep the wheels lowered?

Thank you in advance for any thoughts or advice


----------



## FatherMurphy (May 14, 2013)

A recent tour through my neck of the woods had a number of rolling units that used an air tank on board to drive air cylinders that didn't lift/lower the casters, but instead lifted/lowered parking brakes. The cast would roll the unit onstage, hit one valve, the jacks would extend down to the floor with just enough force to secure the piece, but not lift it. Most of the weight stayed on the casters, so the cylinders could stay fairly small. A second valve would dump the air and release the jacks.

I didn't get a close look at the circuit, the retract might have been a spring action, instead of air.


----------



## Footer (May 14, 2013)

BSchend said:


> This thread has been great for ideas and variations on the concept of lift jacks/air casters/etc. (Note to moderators, if you wish I can restart this question in a new thread if needed)
> 
> Most of the discussion for these items has centered on moving just the set piece with no actors. Would any of these methods still be viable with the additional weight of actors and still allow allow for movement? Total weight while on wheels would be roughly 150 of platform/wagon and 300-400 for two actors.
> 
> ...



Option 2 is how we did it. http://vansandtdesigns.com/portfolio/big-river/

Sent from my Nexus 7 using Tapatalk HD


----------



## BSchend (May 14, 2013)

The "parking brake" option might work, as well. That's a good idea. Kinda makes me think of how they jack Formula 1/Indy cars for pit stops.

Did like the thought of using one cylinder to activate the hinged wheels instead of buying 4 separate ones for the "parking brake" option. At Wichita was it a full lift with the cylinders or just a friction stop?


----------



## Footer (May 14, 2013)

BSchend said:


> The "parking brake" option might work, as well. That's a good idea. Kinda makes me think of how they jack Formula 1/Indy cars for pit stops.
> 
> Did like the thought of using one cylinder to activate the hinged wheels instead of buying 4 separate ones for the "parking brake" option. At Wichita was it a full lift with the cylinders or just a friction stop?



Just friction. You really don't want the thing to lift and shake. It should be rather seamless. Everyone is staring at it when the brakes release. 

Sent from my Nexus 7 using Tapatalk HD


----------



## BSchend (May 18, 2013)

I guess my last question would be what cylinder bore size should I get for the stops? I'm guessing I only need a 1.5" or 2" stroke, but don't want to get too small a bore (or waste money buying too big a size either).

Thanks again for all the feedback.


----------



## kicknargel (May 19, 2013)

If you know how much force you need to exert (in the parking brake case, slightly less than the weight of the unit) you multiply the area of the cylinder bore in inches by the psi of the air pressure. For an example with easy math: a 2" bore has an area of (pi x r-squared) 3.14". At 100 psi, 314 lbs. (For a retracting cylinder you have to subtract the area of the piston, but that doesn't come into effect here.) 

If the piston is driving a lever mechanism, you'll need to add a multiplier of the length of piston throw verses brake throw.


----------



## beachbum (May 22, 2013)

I built about 30 of the pvc pipe/diaphram units 16 years ago and they have been in fairly constant use ever since with minimal maintenance. We generally use portable air carry tanks--about 5 gallon--from the auto parts store or Grainger filled to 120psi with a secondary regulator set for the load--rarely over 40 psi. This usually gets us through a full performance, although on a heavy movement show we have refilled at intermission. If you have the time to build them they are well worth it, as they can lift really heavy units. We have occasionally replaced the caster with a wood block with a rubber pad to make effective brakes/locks on rolling units.


----------

