Pneumatic Ball Puncher

[PVCMike]

Originally Posted by Al Skierkiewicz

Mike,
125 psi is the working pressure at which integrity with pressure is guaranteed. It does not relate to mechanical failure of the device with no load.

Hi Al, i understand that

Originally Posted by Al Skierkiewicz

125 psi is the working pressure at which integrity with pressure is guaranteed.

I have never seen any documentation from the manufacturer or anyone else for that matter suggesting that this guarantee is under the condition that there is a minimum load applied to the cylinders. A mechanical failure of the cylinder, operated as intended and within the specified psi, unmodified and undamaged/not worn, would be a product or design failure by the manufacturer. These cylinders are designed to be operated under the specified pressure and are not subject to the condition of a minimum load to be safe. Yes they will actuate very fast (especially smaller diameter cylinders) but especially when restricted to 60psi (again less than 50% working pressure) we are well within the scope of intended and safe use specified by the manufacturer.

[Animal Control]

If you punch it too hard with too much pressure and not enough padding between the cylinder and ball you will puncture the ball.

[cmrnpizzo14]

Originally Posted by yara92

can you Explane how this works

Essentially what you do is actuate the larger piston so that the air travels through the solenoid into the cylinder. The smaller cylinder is acting like a latch and is blocking the large cylinder from extending. Once the air is in the cylinder and the cylinder is supposed to be extended you retract the smaller cylinder out of the way ("unlatching" the large cylinder. Then the large cylinder will extend much more rapidly than it would have without the latch because the extension speed will not be dependent upon the air flow through the solenoid. It is basically a way to get around the air flow problem that many people experience with the solenoid.

If you want a more detailed explanation we did something like this on our 2010 bot. PM me and I can try to explain it better.

[Dr.Gusta]

Okay would something like the rough drawing below work? A ram is pulled back by a pneumatic piston, the surgical tubing wants to pull the ram back. To fire it the pressure in the pneumatic piston would be released allowing the surgical tubing to pull the ram out and hit the ball. The only thing I am really kind of worried about is the sergical tubing will loose a lot of force trying to pull the piston out even though there is no pressure. Thoughts? Ideas?https://docs.google.com/file/d/0B7jE...p=docslist_api

[Dr.Gusta]

There it should be fixed now. Sorry I forgot to make it public.https://drive.google.com/file/d/0B7j...it?usp=sharing

[Steven Smith]

If I understand the drawing correctly, you would essentially have an outer tube to contain both a pneumatic cylinder and a firing pin. The firing pin is mounted to both the end of the pneumatic cylinder, and a bolt that travels in a slotted groove in the outer cylinder. The pneumatic cylinder compressed, extending the latex, and then is "triggered" by allowing the pneumatic cylinder to extend again (possibly driving it back into the firing pin, but with the assist of the latex tubing). This essentially looks like a pinball launcher to me.


As noted before, two issues you may struggle with are:
-Insufficient speed on your ramming arm, as larger cylinders can often move more slowly
- Too much speed on a relatively small ramming head, which at best will lead to lower accuracy, or at worst could damage the ball.

I'd mock up something simple and see where it gets you (prototype). If you like the idea of the pinball tube, I think you may get more "oomph" from actuating it from the outside, with a mechanism that can run the bolt connected to the latex tubing backwards until it reaches a breaking point... slip off to allow the shot, then catch it back at the starting point.

I do think you would be wise to consider a few other designs that might be simpler (backup plan), but it might still be worth prototyping your original design to see what comes of it.

Steven

[Dr.Gusta]

I think you slightly miss understand but you have the basics down. The piston will pull the surgical tubing tight and the ram into the arm. In order to fire both sides of the piston will be opened thus causing the sergical tubing to actually pull the piston open. So all of the firing power comes from the tubing and none from the piston. Hope that makes more sense.

[Dr.Gusta]

So the pneumatic piston will have no pressure in it at all allowing the sergical tubing to retract and fire the ball.

[Steven Smith]

I might be missing your intent again, but I think you might be underestimating the impact that keeping your cylinder connected will have.

PIC

When you compress that cylinder down to (edit lol: umm "Rooster") your firing mechanism, you will have ~60psi (or less if you regulate it further down) holding it in that position until you go to fire it. When you fire it, yes the latex tubing will pull it out, but it is forced to exhaust the entire contents of that piston chamber either back through the solenoid valve (worst case) or through a seperately actuated solenoid valve Tee'd in at the cylinder. Either way, you are limited to an 1/8" valve size, which means it takes a non-zero amount of time to exhaust it.

Essentially, your piston will act as an air damper for your firing mechanism. This is why many people considering pneumatics as a way to store energy in a spring (or otherwise) are looking to use a "trigger" that will allow the latex tubing to fire without the cylinder slowing it down.

Thanks,

Steven

[Dr.Gusta]

So ay that makes a lot of sense. That is what I was kind of worried about. So like a Solenoid will be needed to "pull the pin" and fire it then the piston will extend again and the pin put back in to the shooter again. I like that. Time to prototype a surgical tubing launcher then incorporate pneumatics later.

[Al Skierkiewicz]

Originally Posted by cmrnpizzo14

Essentially what you do is actuate the larger piston so that the air travels through the solenoid into the cylinder. The smaller cylinder is acting like a latch and is blocking the large cylinder from extending. Once the air is in the cylinder and the cylinder is supposed to be extended you retract the smaller cylinder out of the way ("unlatching" the large cylinder. Then the large cylinder will extend much more rapidly than it would have without the latch because the extension speed will not be dependent upon the air flow through the solenoid. It is basically a way to get around the air flow problem that many people experience with the solenoid.

If you want a more detailed explanation we did something like this on our 2010 bot. PM me and I can try to explain it better.

Cam,
The cylinder moves out to the machanical stop but it doesn't have any higher pressure air or greater volume. When the mechanical stop is removed, air still needs to flow behind the piston and that air passes through the fittings as if the primary valve was opened. Or am I missing something?

[jijiglobe]

Someone on my team talked about using multiple solenoids to actuate a single piston. This would bypass the problems of solenoids not letting enough air through in enough time. Does anyone know if this is a thing you can do? It seems a little sketchy.

[MechEng83]

Originally Posted by jijiglobe

Someone on my team talked about using multiple solenoids to actuate a single piston. This would bypass the problems of solenoids not letting enough air through in enough time. Does anyone know if this is a thing you can do? It seems a little sketchy.

R90: The outputs from multiple valves may not be plumbed together.