# Efficiency Matters



## dominic81 (Nov 3, 2010)

Hey everyone. I'm new to the Forum and have read alot of other threads on the how to set up Pneumatics. But I feel with the level of experience that is out there we could focus on some important factors dealing with props. Most props that I have seen on the Market require above 100psi input. It seems that the thought process is big volume tanks to aide in prop lag. My question or guide for discussion is Has anyone ever used pneumatic controllers that take 3-15psi input signal's to volume booster's along with pneumatic regulators at the props to aide in Efficiency? What has been the best set up that seems to be the most efficient and cost effective. Just food for thought!!!!


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## HalloweenRick (Nov 25, 2005)

I think the real reason most of us use big compressors is so the compressor isn't working all night long. I run 2 air props (8" Head Popper and 7" Head Popper) and run them off a 17 gall 1.5hp air compressor I got from Northern Tool for $99. The problem with using a 3-4 pancake or small air compressor is that it takes to long to cycle and is on on the time. My props actually run at 75-80psi.


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## dominic81 (Nov 3, 2010)

Thanks for posting Rick. That's kinda what I'm after to better help others that are new to pneumatics. I found this site http://www.truetex.com/aircompressors.htm
it explains commpresor cycles at different conditions. I would be more interested to know what else is out there to keep the props running the most effciently throughout the night. If you got a setup that works feel free to share it with others.
"The more people we scare the happier we will be"
Keep this thread going we can learn from each other!!!!


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## Dead Things (Apr 4, 2009)

I have been using pneumatics for a couple of years now and I think part of the efficency comes from the cylinder. My understanding is the larger the bore size of the cylinder, the less PSI required. I would like to know what bore size folks use for differnt lifters (four bar, torso erector, etc)


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## jdsteel82 (Aug 27, 2010)

Good ole Pie are square, but really they are round!

Larger diameter pistons require less Psi to do the same amount of work, but for volume to equal volume of a smaller diameter piston you loose speed and stroke with a larger diameter. 
A smaller piston can travel faster over a longer stroke with no load, but as you load that cylinder you need to ramp up the feed pressure to maintain the velocity.

And for our Passion/Hobby...Velocity is usually keen. So where do you make the split?

I like playing with Festo fluidsim. there are free demo versions out there on their site just make sure you get the P version for pneumatic.


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## bfjou812 (Aug 15, 2008)

dominic81 said:


> Thanks for posting Rick. That's kinda what I'm after to better help others that are new to pneumatics. I found this site http://www.truetex.com/aircompressors.htm
> it explains commpresor cycles at different conditions. I would be more interested to know what else is out there to keep the props running the most effciently throughout the night. If you got a setup that works feel free to share it with others.
> "The more people we scare the happier we will be"
> Keep this thread going we can learn from each other!!!!


Thanks for that link, I haven't read all of it but I will. I've been involved in the maintanence field for 20 years , repairing production machinery, and have what I thought a pretty good understanding of pneumatics. 1 thing that I find is that people get confused with is the pressure vs. volume issue also the proper sizing of components when designing a system. And there is also electrical effiency. Thanks!!


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## dominic81 (Nov 3, 2010)

Bf that was my thought process on creating this thread. I work in the maintenance field for a Nuclear Plant and deal with pneumatics every day oddly enough the largest crap I see is all controlled with 3-15ps or pneumatic to electric controllers. This stuff still messes with my head. But what must be remember with any system know matter how large or small Supply is what it is Supply. So if a props needs 80psi that is Supply, Its your controls that will assist in how quickly you effect volume which is your compressor tank size. Make those props work for you, not you work for the props!!! So share those design setup what works great for one hopefully works just as well for the next!!!


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## corey872 (Jan 10, 2010)

An efficient system is one thing - and surely doesn't hurt. Though I would caution, most people 'haunt' one month (or really even just a few weeks) of the year. In that instance, 'cost effective' may be a better term. If a guy has a normal shop compressor and a few air cylinders laying around - they may not be strictly the most 'efficient', but if they are free, or low cost, then it is very cost effective.

I see this a lot over in the electronics side - using a resistor to drop 12 volts down to 3 for a LED is about the most inefficient way to do it, but the resistor is only a few cents and running the set-up a few weeks of the year isn't really going to put a dent in the electric bill for the few wasted watts, so overall it's very cost effective.


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## mroct31 (Nov 10, 2007)

Hum, 75-80PSI, most props needing 100PSI...what kind of props are you guys running that need this much PSI? I'd destroy my 2 graveyard pop ups, scissor skelly, TCT, dual cylinder grave escape and MIAB if I ran them at that high a PSI! My one compressor is set at 80PSI then the inline air pressure valves reduce that down to 20-40PSI at the most.


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## Dead Things (Apr 4, 2009)

Some of my props I have to use 100 PSI to get them moving. I have a pneumatic groundbreaker (a la casa fear), that runs on 30-40 psi, but my coffin leaper has to run at 100 or it won't move. I built the 4 bar as per most out there but the cylinder couldn't lift it once I had dressed out the prop, especially once the head went on. I had to move the cylinder off the "mast" onto the front "leg" to increase the mechanical advantage to the cylinder. 








Madmax, how/where is bore measured? The main body of the cylinder in this pic measures 1" but the piston measures 3/8". I see these steel 4 bar mechs out there and think "how the heck do they get them to move?"


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## Hellspawn (Oct 13, 2006)

when dealing with pneumatic props, I keep the prop that is mounted to the linkage as light as possible, for those props that require the additional air to get started, try using a heavy duty spring, I have a buddy who uses garage door springs to "aid" in the initial lifting of the prop and then the air does the rest of the work.

the most psi I run on a prop is 75psi and its only that much because the linkage itself was my first attempt at a pneumatic lifter, once I rebuild/re-design it this year, I fully expect it to need alot less pressure..


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## dominic81 (Nov 3, 2010)

Hey Hellspawn thanks for sharing on What your friend does with the garage door spring. Thats a pretty good idea, Send us an update on your re-design if you think of it I'm sure we all would be interested in the motion of the prop using aid from a mechanical lift.


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## Dead Things (Apr 4, 2009)

Yes, that is a good idea. I would have an easier time finding a large spring than a large bore cylinder. It would be nice if someone out there could weigh in on the bore size thing.


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## niblique71 (Dec 2, 2009)

Pneumatic and hydrolic cylinder bore sizes are measured by the piston/cylinder size within the cylinder and the stroke it has (travel distance from fully closed to fully open). The piston inside is much larger than the shiny shaft that you see on the outside. The larger the "Bore", the more leverage (lifting power) that a gas or liquid can impart on it, but conversly the more volume if air/liquid it consumes during each stroke. Any pneumatic contraption you design should be designed with at least a little knowlege of how much weight a cylinder can lift at a given air pressure. Most companies that sell cylinders can give you some basic info on how much a cylinder can directly lift at let's say 100psi. Once you know how much it can lift without any leverage, you can then mathmatically (or intuitively) calculate what size (Bore) cylinder you might need and a close approximation of it's mounting points to get the best leverage.
To put it more simply, I usually design my lifts out of wood scraps and bolts and experiment with mounting points. I then test the geometry by lifting it with my hands to get a close Idea of how much weight my cylinder might have to lift. Then I order my cylinder once I'm satisfied that I have covered my cylinder requirements. Once you've built a few of these contraptions you'll have a better idea of how/why some devices need more "Start" pressure. and some don't. It's all about geometry.


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## Dead Things (Apr 4, 2009)

Thanks for that, niblique. I have seen some calculation sites and one download for designing four bars but I really couldn't get them to buck as I am a hands on, have to see it type of learner. I think you are right, I just have to start building them and then I can begin to "intuit" it more. Just as aside, what is a common bore size that you use?


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## niblique71 (Dec 2, 2009)

3/4" to 1" to 1-1/4" sizes are very common. but there are so many applications that I doubt there really is a common bore size or stroke. 

Another thing to consider is your stroke. Why?? Because you can achieve the same movement with a 12" stroke cylinder as a 6" cylinder (Same bore), BUT because the stroke is so much longer on the 12" one, you can gain better mechanical advantage by moving your mounting points even thoug both cylinders can theoretically lift 80 lbs at 100psi (Straight lifting power before you mount it in a halloween prop)

Lets say you have a single pivot point type lift with a 6' long bar that you want to go from horizontal to almost vertical. with a 6" stoke cylinder you will have to mount the cylinder much closer to the pivot point reducing the mechanical advantage of the cylinder to lift it. However with a 12" cylinder you can move the mounting points further away from the pivot point therefore reducing the leverage against the cylinder. Both cylinders have the Same final result, but the 6" cylinder has to work much harder to lift your "bar" simply due to mechanical disadvantage of having to move it closer to your pivot point. I know it might sound redundant, but once again it's a simple understanding of geometry. 

Effective pneumatic props are all about finding balance of frame geometry, bore size, stroke, and air pressure. If your a graduate of Cal tech, then you can calculate everything ahead of time and just make it. If your like me??? You experiment using just enough knowledge to keep you from blowing up the neighborhood. Eventually you begin to figure out what should work and what won't.


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## Dead Things (Apr 4, 2009)

Well, I'm no Caltech grad, that's for sure! And my neighbours appreciate the fact that even though I could blow them up, I haven't . I see what you mean about mechanical advantage. I had the cylinder in the above pic mounted under the pivot point and I couldn't get it to lift the prop. I moved it to it's current location and it works ok, a little slow at the beginning but it still gets the job done. I guess I get hung up on what I see in others tutorials and wonder why mine doesn't work that way. I'll just have to trust the process, ask questions and experiment.
Thnks for the help!


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