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Creature Revenge
09-24-2008, 11:45 PM
Wondering if anyone has ever worked with the Fright Prop item called the "Heavy Duty Pop-Up Mechanism." Essentially you attached a five-foot 2 X 4 or a 2 X 3 to it with a head and costume and set it to pop-up out of a grave or coffin. (You can see it here: http://www.frightprops.com/frightprops/props/Product.asp?ID=0782 ) It comes with a 1.5 inch bore cylinder already mounted on it. We're triggering it with a BooBox4. Our problem is this: It seems to take a lot of pressure to get the lift started, but once the prop gets about halfway up, it overcomes the force of gravity, flies up, and smacks VERY hard against the stop. We're using in-line flow control valves for the pressure adjustments (both up and down), but we can't find any settings that will give us a smooth, even lift. We've tried setting the compressor output anywhere from 50 to 100 psi, and it still does the same thing. Has anyone actually worked with this unit before? Is there a trick to getting a smooth up and down movement with this mechanism? Thanks in advance for any help.

Boo Crew Production
09-25-2008, 06:03 AM
I have not used there mechanisms, There could be several issues happening here. could be the items you have attached exceed the amount of weight it is intended to lift or the cylinder is under sized, or there are faulty components. I would recommend removing the items you attached, and see how it operates then. If you have the same issue, then there may be a faulty component, could be the valve, or the flow controls.

Hope this is of some help to you.

craigsrobotics
09-25-2008, 06:58 AM
appear to have any flow controls on the cylinder....if it does, try adjusting them, otherwise, your prop is either too top-heavy for the design, or there is a faulty component...try bypassing the valve and feeding air directly into the cylinder (lower the PSI FIRST and BE CAREFUL)...you shouldn't have to supply any more than 15 to 20 PSI for that size cylinder to react with weight on it...if the cylinder does not have flow controls, purchase them from Frightprops and USE THEM!!! They will save your components from failure and you will be able to control the movement more precisely and safely without the BANG after the prop moves past the center of gravity.:D

Creature Revenge
09-25-2008, 08:42 AM
Thanks for the replies, folks. Just to further clarify... Yes, I am using flow control valves. They are MFD in-line flow controls. Someone suggested moving them closer to the cylinder in the hose line. So we re-cut the lines and did that, but it had no effect. We've also tried turning the valves around to reverse the airflow through them, which also had no effect. (I don't think direction matters on these MFD valves.)

Regarding the weight, that's what we though the problem was. We originally had a very nice "Countess" figure on the end of the 2 X 3, which weighed about 12 lbs. We replaced it with a latex zombie mask, a pair of latex/foam hands, and a very light black gown on a 1X2 frame. All totalled, the weight is now maybe 3 lbs. The prop will now activate with less air pressure from the compressor, but we're still having the same problem of it slamming forward once it passes the center of gravity. The only thing we've been able to use that "somewhat" helps the situation is attaching a large screen door spring to the back of the rising 2 X 3. We use that to slow the prop down a bit as it nears its end of travel. It helps a little, but still doesn't work very well. The whole animation just looks "cheesy" instead of creepy or spooky. It looks too much like a "fun house" effect, which we don't want at all.

Any other ideas? Anyone? We're getting mighty close to set-up time and this effect just isn't working for us!

craigsrobotics
09-25-2008, 08:54 AM
the slamming, you could had a flow restrictor to the valve's exhaust port. The pressure will be great at the time of activation, but will slow or dampen when the cylinder reaches the end of its stroke....Play with the adjustments to stop the banging...we use this method sometimes, and it works great...

Creature Revenge
09-25-2008, 09:02 AM
Would the flow control valve on the down side of the pneumatic circuit act as the "flow restrictor" when the prop is rising? If so, are you saying I should adjust the "down control" to fine toune the "up control"? Or is this a separate piece of gear I need to add in the air line?

Jim Warfield
09-25-2008, 09:15 AM
Maybe a little electrical shut off switch positioned to activate (and kill the power to the valve) as it rises would help it to not slam.
you could mount a switch closely at the bottom of the hinge so very little travel would have to be had to make it shut off, then comes the time spent adjusting the distance. The wiring could be simpler if the valve is low voltage.
Your big spring could reset the cylinder if it had to be air powered to reset.
We work and fiddle with adjusting stuff and then the customer yawns seeing our efforts so then you drop a 49 cent plastic spider on their shoulder and they almost pass out from fear!
How much pure fun can we have?

beardedbil
09-25-2008, 09:20 AM
Have you tried contacting fright props? I know I have called Doug for last minute help and he has always been there willing to offer advice...

craigsrobotics
09-25-2008, 09:27 AM
it depends on whether or not your flow restrictors are directional...some restrict one direction, but allow full airflow in the other direction(ie in exhausting mode)...assuming they are not directional flow controls, what I was suggesting is to add a directional flow control to the exhaust output of the valve so the "exhaust" is restricted at the end of the cylinder's full stroke......you want to restrict the extended position of the cylinder, at which point the top port of your cylinder will be feeding air back to the valve through it's exhaust port(which is the flow you want to restrict to keep it from banging), and the bottom port of the cylinder will be sucking air through the valve from the compressor giving it its full push.

Determine if you have directional restrictors first...look on the side of the flow control, and there should be a diagram with one large arrow and one small arrow...this would tell you the direction that the air is restricted... They may just be "speed controls", and not DFRs, or directional flow restrictors, which restrict in BOTH directions of air flow.

Creature Revenge
09-25-2008, 09:29 AM
Yes, I've spoken to Doug a couple of times about this and he's been very responsive. A great guy. However-- oddly enough-- he doesn't seem to have a lot of experience with this particular prop activator himself. He was the one who suggested I move the flow control valves closer to the cylinder in the air line, which didn't help. The last I heard, he said he was going to run some tests at his warehouse to see if he could figure out a solution, but I haven't heard back from him. Since I'm running out of time here, I figured I'd post the question with the hopes that someone else out there has this same pop-up mechanism and has already conquered this problem.

Creature Revenge
09-25-2008, 09:38 AM
Determine if you have directional restrictors first...look on the side of the flow control, and there should be a diagram with one large arrow and one small arrow...this would tell you the direction that the air is restricted... They may just be "speed controls", and not DFRs, or directional flow restrictors, which restrict in BOTH directions of air flow.


It does not appear that the MFD valves are directional. There are no arrow markings for direction, and I've tried flipping them over but it doesn't appear to have any effect. Your suggestion of better controlling the exhast port of the valve sounds promising. This is our first year with pneumatics, so I'm afraid I don't fully understand how your suggestion translates into "which hose and valve goes where". Could you possibly provide a more step-by-step explanation for a pnematic novice. Thanks very much.

craigsrobotics
09-25-2008, 09:40 AM
nothing unique about this mechanism...it's basic pneumatics...you want the prop to rise fast, and lower slowly....you need to restrict the airflow on the upstroke, but at the end of the stroke (when the last bit of air has reached the valve's exhaust port), therefore, you need to move the inline restrictor closer to the valve, OR, use a directional flow restrictor, OR put a flow restrictor directly on the exhaust port of the cylinder....

craigsrobotics
09-25-2008, 09:46 AM
with what you already have, you could remove the flow control from the bottom cylinder port and install it on the valve's exhaust port, leave the other flow control inline on the top cylinder port airline, ...it doesn't matter how slowly the prop lowers, but you want that quick flow to the bottom port of the cylinder to give it that initial push, then at the end of the full stroke, the restrictor on the valve's exhaust will "catch" allowing it to dampen and not slam...be sure to reduce your PSI while testing this.

Creature Revenge
09-25-2008, 09:50 AM
with what you already have, you could remove the flow control from the bottom cylinder port and install it on the valve's exhaust port, leave the other flow control inline on the top cylinder port airline, ...it doesn't matter how slowly the prop lowers, but you want that quick flow to the bottom port of the cylinder to give it that initial push, then at the end of the full stroke, the restrictor on the valve's exhaust will "catch" allowing it to dampen and not slam...be sure to reduce your PSI while testing this.

The only confusion I'm having here is the wording: "valve's exhaust port". Do you mean add an in-line flow control to the exhasut on the solenoid?

craigsrobotics
09-25-2008, 09:53 AM
that's exactly what I'm suggesting...sorry, I get hung up on semantics sometimes...

Creature Revenge
09-25-2008, 09:56 AM
that's exactly what I'm suggesting...sorry, I get hung up on semantics sometimes...


Perfect. That sounds like a plan. That's the first thing I'll try tonight when I'm back in the garage. I'll let you know what happens.

craigsrobotics
09-25-2008, 09:57 AM
Good luck, and be careful...:)

SinisterControls
09-28-2008, 06:11 PM
Ideally you want to use meter out flow controls. These meter the exhaust coming out of the cylinder. The air coming into the cylinder is not restricted. Doesn't sound right at first, I know. But picture this. If you tried metering (restricting) the air going into the cylinder and the cylinder is positioned straight up and down vertically. Going up it would work fine. Now put air on the other port to send it down. It would drop like a rock as there would be no back pressure on the opposite side of the piston. You wouldn't even need air pressure, gravity will take it down. Same scenario with a meter out flow control and it will slowly release the air on the opposite side of the piston as you apply air pressure to the opposite side. Ideally the flow controls should thread right into the cylinder. With that said, what your describing sounds more like incorrect geometry rather than flow controls. Flow controls act the same throughout the cycle. Cushions are a whole other animal and those take effect at end of stroke only but flow controls are constant. It sounds like your going into and out of mechanical advantage and its binding in transition. Can you alter the position of the cylinder? Closer to fulcrum (pivot point) needs more force but less stroke, farther away will require less force but more stroke. A 1.5" bore cylinder has 1.76 in^2 of area (pi r^2) x 100psi is 177 lbs of force. That's a lot of force so that's why I suspect geometry over weight. I limit my supply to 60psi and keep my props much lower. The lower the safer.