# Slow cylinder. Any suggestions?



## Spooky Dave

Hi all,

I'm experiencing a recent setback in one of my props. It's a pneumatic popup cemetery column (cemetery pillar trauma in another thread). I've hooked up the cylinder and it works fine, but quite slow. I'm a bit stumped.

Here's a picture.










This cylinder is WAY more than I need to lift what you see. It's just what I had on hand. The only weight addition to what you see in the photo will be a little bit of painted foam. This is a 2" bore 12" stroke double-acting cylinder. I could probably throw a couple of Shetland ponies on top and it should still lift. The problem is, it won't lift quickly. I don't know why.

I have even removed the flow restrictors (something I always use) for test purposes. No faster. It also happens to lift at about the same speed whether 40 PSI or 60 PSI. I could always keep upping the PSI, but I get the feeling it won't make much difference. Besides, I don't like to run my props at anything much higher than 80 PSI. And heck, this is nothing but a simple popup. No unfolding mechanisms, such as with some of my other props. Straight up and down. It should ROCKET up. But it doesn't. It seems to take a full second and a half to two seconds to travel those 12 inches. That's not fast enough for a good startle!

I don't need blink-of-an-eye fast, because this is a wooden frame after all. But I'd like to be able to fine tune this. Any thoughts?

As an aside, I bought about five of these big ol' cylinders a few years back at a steal. I made one other prop with one of them, and it, too moves slow. That one is a VERY heavy prop with lots of linkages, so I thought the weight and angles were the issue. Now, however, I'm starting to wonder if large cylinders have some sort of built-in flow restrictor?

Any thoughts? Somebody please help me get some more speed!

Dave


----------



## mattt1977

Looks to me like your using 1/4" air lines. The sluggish response could be from the restriction caused by these. A 2" x 12" cylinder requires quite a bit of air to move, and it just takes longer for 1/4" lines fittings and solenoids to fill the cylinder. I would use the largest air line fitting and solenoid that the cylinder can take. What size are the ports on the cylinder?


----------



## curley

Yea Matt I agree, also how far is the prop from the compressor, remember you will have a drop oh PSI, and a's Matt said I would go with 3/8 air line, remember it's not always the PSI but also the volume or CFM. I run all of my hoses 3/8 and it then breaks down to 1/4 at the prop... Also have you added and tool oil to the cylinder ? I lube all of mine... Let us know how it goes. Good luck


----------



## walterb

Dave I have the same cylinder with the same problem. It has to be an airflow issue as I had a resorvoir 2 feet from the cylinder. I think it may need a garden hose running into it.


----------



## niblique71

Although 1/4" air lines would slow a 2" cylinder down, it wouldn't slow it down as much as you describe, unless the weight was extreme. I suspect something else is going on. Do you have a water separator/filter on your setup?

EDIT: Although what I said below has value, it occured to me that you want to run this prop at lower air pressure. ALthough I don't know the exact math, I know that 80psi has a lot more than double the force of 40 psi. Therefore 80psi could transfer (lets say) 4 times the air (CFM) through a 1/4" line. You may in fact just need a larger selenoid and air lines to run at a lower psi. But read below to double check.

Before you try anything, I would keep testing your prop by upping the psi in 10lpsi increments. Just for an experiment. You might find that a higher psi will pass more air to your large cylnder once it reaches a psi that it likes.

I would then check your selenoids. Dirt and debris can restric the movememt of your selenoids and clog your muflers too. Both would have a detrimental effect on air flow. Try taking the muffler off (If they have one). You could also try switching the selenoids onto a prop that you know already works at the correct speed to test that they are OK. You could also take selenoids that you know are working fine and switch them to your 2" cylinder to further diagnose the problem.

If they work fine, check for binding on your prop. I noticed you had 2 anti rotate bars installed. You really only need one of your cylinder is rigidly mounted. You could have mechanical binding in that area.

If all of that checks out, here's another thing you could check. If you have an independant air regulator for each prop, your regulator for this prop could be clogged or faulty.

The only other thing I could think of is that your cylinder may have a bent shaft or faulty O rings on the internal piston. This is Highly unlikely though.

I always use a water separator at the beginning of the main air line, and empty my tank of water using the petcock at the bottom of your compressor EVERY TIME when I'm finished using it. The amount of water and therefore rust particals inside your tank could be reaching extreme levels if you aren't religious about doing this. Since I don't know your practices I thought I should mention this.

Good luck and feel free to ask any further questions


----------



## Spooky Dave

Thanks guys, excellent suggestions, all. I don't know why it didn't occur to me to look at the video from earlier tests (cemetery pillar trauma), but I did so not long ago and the prop moves much faster then. It's there if you want to check it out.

Which means that something I've changed between then and now has altered the speed. I think the 1/4-inch tubing is the big culprit. With the earlier tests I used my 3/8 line and only a couple feet of 1/4-inch at the very end. This time, the 1/4-inch is much longer. Also, I do have an independent regulator, and the two anti-rotate bars. You guys have given me lots to think about. If nothing else, I have a couple of air tanks that I can have on hand for storage. 

Thanks for the tips! I'll keep you posted!

Dave


----------



## walterb

Dave let me know if you get it working. I tried 3/8 line with no luck. I removed the regulator and took the pressure to 100psi. Try a bigger solenoid and larger tubes.


----------



## niblique71

My apologies for chiming in twice. I also noticed that your anti rotate bars are far away from the center of the cylinder. If they aren't well lubed with grapite or grease they will bind. If they were closer to the center of the cylinder AND 180 degrees from each other With the cylinder in the center of them, the mechanism would be a lot more reliable. The farther apart from center they are the more leverage they will have to bind the mechanism. I noticed a little deflection in the geometry of the top part in your test. Since your using wood for the guide holes, this could get worse with time and explain your difference in performance. This isn't to say that you'll completely solve the problem by changing your slider points. but it WILL help no matter what the final determination of the cause is.

If the size of the tubing is the actual reason for the slowness, You might still want to get a larger selenoid as well. Going to 3'8" tubing will help, but having all of the orafices match your tubing will really improve the airflow.


----------



## Spooky Dave

Again, thanks for the tips, all. I didn't get a chance to make it out and try any of these tonight, but I'll certainly do so tomorrow.

Here's the video of earlier tests. (Just scroll down a few entries for the video.) The anti-rotate bars were already installed, which gives me hope. This speed is perfectly acceptable to me. I just need to recreate it.

http://hauntforum.com/showthread.php?t=26878

Greg, I'll certainly lube the anti-rotate bars. Never even thought of that. (Oh, and Greg, if you look closely at the picture in this thread, you can see two of your incredibly awesome LED spotlights inside the column. They look great!)

Curly, I've actually never lubed any of my pneumatic cylinders and have wondered many times if I should be doing that. How do you apply the oil? Just drop it into the valves? Do you use an atomizer in the line? Walter I'll let you know what solves the problem. Like I said, I take comfort in the fact that I've managed to make this cylinder perform up to speed once. I can do so again!

Matt, you're right that these big cylinders take a ton of air. Cheap though they might have been, I'm beginning to think that I don't want huge cylinders unless I need the lifting power. This is too much headache.

I'll keep you all posted. Thanks so much for the wealth of ideas. You guys are the best!

Dave


----------



## Spooky Dave

p.s. Greg, your points are well-taken on the poor placement of the anti-rotate bars. I may yet consider moving them to center, and either side of the cylinder. If nothing else, I've learned what not to do in future props. I just placed them where it was convenient. Didn't think it through first.


----------



## Haunted Spider

I don't know if it is mentioned or if you have it in your set up, but sometimes in the 1/4 inch lines, you have a valve control that limits the air flow so you can keep it at 20 psi vs your other prop at 80 psi. Do you have one of those and is it turned down? 

The haunt I used to work at had a Skelerector from Scarefactory that had that issue when they bought it. Turned it up and it worked like a charm. Maybe the fix is that easy.


----------



## fritz42_male

Yet another option is to add a counterbalance system to counteract the weight of the lifting portion - most easily a spring.


----------



## Spooky Dave

Well folks, it was the valve. I tried eliminating the 1/4-inch line as much as possible, and it still seemed sluggish. Then, I tried bypassing the valve and at 60 PSI I thought my prop was going to self destruct it opened so quickly.

I had another, newer valve on hand (same 1/4-inch holes, though) and swapped it out. The new valve works much better. Still not as quick as bypassing the valve altogether, but I think I can be happy with these results, especially if I up the PSI a bit more.

Now I'm wondering what's going on with my other valve. It's not all that old. I'm wondering if it's because I never oil my pneumatic components/cylinders/valves. I'm starting to think that might be a severe oversight. 

Can anybody else give me some thoughts on the matter of lubrication for pneumatics? Is it necessary? I'm going to try and figure out why this other valve won't work. Thanks again, everybody, for your help.

Dave

p.s. I agree with Niblique that larger valve holes would be beneficial. Trouble is, I don't have any such valves, nor do they seem to be easy to find. I usually buy from Evilusions (though there store is largely down) and Monster Guts for valves. Neither of them seem to carry the 3/8-inch hole valves. Does anybody else buy these larger valves? They'd come in handy for some of those other large cylinders...


----------



## niblique71

Try Frightprops. I use them exclusivly for my pneumatics since they always have a HUGE selection of "in stock" items.

I found this 3/8 selenoid. http://www.frightprops.com/pneumatics/solenoid-valves/3-way-solenoid-valves/3-way-valve-with-3-8-inch-orifices-0920-0001.html

I don't know if that is the actual valve you will need. As far as lubrication, you can use pneumatic oil Used for air ratchet's and impact guns etc. I've never lubed any of mine but I think I'll start this year while they all seem to work. I would imagine that a miniscule amount of lube would be needed. I would asume that you just put a drop right into the selenoid where the main air supply would go on. I just don't know if it will clog the Mufflers.

PS, Check that the mufflers aren't clogged


----------



## Spooky Dave

Never heard of Frightprops, they look like a great resource. Thanks! 

p.s. I never use mufflers (like the hiss), and never empty water out of my tank. Booya! I'm such a rebel.  Heh, actually, I tried emptying water the first few times but none ever came out. The air is so DRY here in southern Utah that I've yet to see a drop come out of my compressor. It's been a while, though, so I should try again. I understand some areas that is a massive concern.

p.p.s. Yeah, I was thinking one or two drops into the solenoid or even the cylinder ports. Got the idea from my new pneumatic tool (finish nailer) where it says to use one or two drops every single day.


----------



## Spooky Dave

Hi Madmax,

Excellent suggestions! I checked out the following video about quick exhaust valves on Frightprops (http://www.frightprops.com/pneumati...w-controls/quick-exhaust-valve-0738-0336.html) and I am now a believer!

I'm going to have to experiment with those, or at least rig my valve to be single acting. Decisions, decisions... thanks, one and all! This prop is going to fast enough one way or another. Sweet!

Dave


----------



## Spooky Dave

Hey all,

Okay, so in case any inquiring minds would like to know, rigging the valve to run as single acting made a HUGE difference in the amount of PSI necessary to lift this quickly. Anything above 20 PSI and the action is too violent. So, yeah, safe to say speed is no longer a problem! 

I think I'd still like to have at least one quick exhaust valve at some point so that I can use both sides of the valve. I prefer to use air, not gravity, to reset my props. More control that way. For now, at least, it's great to see the prop zipping along again. Thanks for the tips, everybody. Now I'm quite curious to get the big monster prop out of storage and see if I can increase the speed there with similar tactics. I'd always assumed it was because of the weight of the prop. Perhaps not.

Anyway, haunt on! Thanks for the great advice.

Dave


----------



## oldpro

It sounds to me that its most likely an air flow problem .
Remove the cylinder and actuate it by hand ,if it moves freely by hand 
In both directions then prob not the cylinder. Next connect air to it and see how it responds with no weight.Also while the cylinder is off check your guides for drag.
It's best to have more air flow and volume than necessary and controll it with flow controlls


----------



## gadget-evilusions

Spooky Dave said:


> I usually buy from Evilusions (though there store is largely down)


I apologize for that. Our online store will be back up completely by the end of this month. We opened our own commercial haunted attraction this year, and that unfortunately interfered with us servicing our customers as we have in the past. This will not happen again. Once again, sorry, we will make it up to everyone.


----------



## halstaff

That's great news Brian. We missed you!


----------



## Darkmaster

*Thumbs up!*



Spooky Dave said:


> Hey all,
> 
> Okay, so in case any inquiring minds would like to know, rigging the valve to run as single acting made a HUGE difference in the amount of PSI necessary to lift this quickly. Anything above 20 PSI and the action is too violent. So, yeah, safe to say speed is no longer a problem!
> 
> I think I'd still like to have at least one quick exhaust valve at some point so that I can use both sides of the valve. I prefer to use air, not gravity, to reset my props. More control that way. For now, at least, it's great to see the prop zipping along again. Thanks for the tips, everybody. Now I'm quite curious to get the big monster prop out of storage and see if I can increase the speed there with similar tactics. I'd always assumed it was because of the weight of the prop. Perhaps not.
> 
> Anyway, haunt on! Thanks for the great advice.
> 
> Dave


Glad to hear it works now. Quick exhaust valves are nice and do exactly that. Allows quick response to moving in either direction, releasing the air in the opposite direction of movement.
Good work!


----------



## evil_ol_man

There's also...this....What size compressor are you using? How may props are you trying to power with that air compressor? What's the C.F.M. (Cubic Feet Per Minute) that the Compressor puts out? (It's higher at lower pressure.) I have been working with Compressed air since I was 12 years old (Air Tools.) If you are using a Small Compressor. I tried using one of those Pancake Compressors to power 2 props....they were slow....Why? Because the tank is smaller, and the CFM that the compressor flows is Low...When I decided to use my big compressor from my shop...OH BABY! EXAMPLE: My Pamcake Compressor flows 2.5 CFM at 90 PSI, and 3.5 CFM at 40 PSI at 1 H.P. with a 6 gallon tank. My Shop Compressor...5 H.P., 60 Gallon Tank, Flows 18.1 CFM at 90 PSI.... The CFM is the difference...Both Compressors will make over 125 PSI...the larger one...flows way more air...BUT if you don't have a need for a huge compressor or want the expense of having it, or don't have the space for it...then Add in a 10 Gallon (Or larger) air tank to the system, and see if this improves your prop performance. Also..Follow the other suggestion about moving your anti-rotation bars....


----------

