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new to forum. Pneu Pneumatic

Built a pneumatic cannon? Then post it here! This section is for completed, finished cannons that you have built. Please include pictures and information.
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new to forum. Pneu Pneumatic

Unread postAuthor: pretzelperson » Sat Sep 08, 2007 6:40 pm

I have great concern with pneumatic PVC cannons and safety of chamber under pressure. Failure would be catastrophic and failure is unpredictable. Chamber on the pneumatic cannon is a size E medical oxygen cylinder rated for operational pressure of 2,200 PSI and I operate at about 5% max rated operational pressure. Weakest point is shraeder valve. I can pump it up to any pressure. I am limited only by my pump. High pressure and high volume = fun. I can screw in basically any size barrel. I have a 3", 1.5" and a 1". Took about 15 minutes to screw all the fittings together.
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Unread postAuthor: DYI » Sat Sep 08, 2007 6:49 pm

Well... That's great, but what the hell is this topic even about? I see no pictures, no questions, no specs (other than the fact that it operates at about 110 psi), not even some half-assed illogical statement about how science is wrong, and so are all of the respected senior members.

So what is the purpose of this thread?
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Unread postAuthor: turbohacker » Sat Sep 08, 2007 7:08 pm

DYI wrote:Well... That's great, but what the hell is this topic even about? I see no pictures, no questions, no specs (other than the fact that it operates at about 110 psi), not even some half-assed illogical statement about how science is wrong, and so are all of the respected senior members.

So what is the purpose of this thread?



@DYI, I have no problom seeing the pictures

Very nice cannon -especally for your first.
Maybe you could invest in a bicyle SHOCK PUMP. They are designed to reach pressures of over 300psi and are only about $25. The cannon you have here should be good for that.

P.S. Welcome to the forums!!! Just make sure to put your post in the proper place next time so as to keep these forum tidy as well as all the childeren happy.^^ (this post should be under cannon showcase)
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D_245%20EKOPA8.jpg
Standard SHOCK PUMP
D_245%20EKOPA8.jpg (32.72 KiB) Viewed 580 times
Last edited by turbohacker on Sat Sep 08, 2007 7:13 pm, edited 1 time in total.
<-- This is not a cat avatar

If it walks like a dog, sratches like a dog, and barks like a dog, than its probobly a...-TURTLE, it's a TURTLE!!! Cant you see?!!!

frankrede wrote:Great googlay mooglay!
Thats a beast!
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Unread postAuthor: Hubb » Sat Sep 08, 2007 7:12 pm

I see pictures, I'm assuming because it was edited. You should pump a lot more air into this thing (maybe a CO2 setup will allow for much higher pressures), then post up some damage pics of s**t you break.

I am also assuming that you were posting this as your cannon. It was posted in the wrong thread.

FYI: I have never had a problem with any type of pneumatic pvc cannon, but I always take safety precautions, such as a gauge, pop-off, etc.

Anyway, welcome to the forums.
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Unread postAuthor: DYI » Sat Sep 08, 2007 7:15 pm

Oh crap, sorry about that dude. I couldn't see anything at first.
Really sorry.

It looks good, what kind of tank is that you're using? You should really take it up to higher pressures to see what kind of damage it can do.
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Unread postAuthor: pretzelperson » Sat Sep 08, 2007 7:16 pm

Thanks. My pictures didn't post at first--they were too big so I had to resize them so I think that is what mislead DYI.

I though of a shock pump but it would take too long to pump up. I think a shock pump is high pressure and relatively low volume. There are plans here on the forum to make a high pressure pump. I may consider going that route as I think I could pump more volume.

The chamber is 4" dia and about 25" long. My big disappointment was the threaded fitting on top of the cylnder is only .5" and I was expecting it to be .75". I think the larger opening would have significantly improved the performance. I experienced that some ammo descintegrates when I open the ball valve. I think it is because the air is being forced through such a small opening at the top of the cylinder, but I'm not sure.
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Unread postAuthor: turbohacker » Sat Sep 08, 2007 7:22 pm

The ammo just tends to disenegrate because of the enourmous pressure that hits it instantly, not quite sure how to explain it. Try marbles :twisted:

Maybe get a burst disc (a union with a peice of somthing inside) It would improve your performance greatly.
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If it walks like a dog, sratches like a dog, and barks like a dog, than its probobly a...-TURTLE, it's a TURTLE!!! Cant you see?!!!

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Thats a beast!
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Unread postAuthor: MrCrowley » Sat Sep 08, 2007 7:23 pm

Welcome.
Please refrain from insulting our members in your first few posts. Unless he said something really bad that was uncalled for we don't need to hear it.

Nice cannon, I've moved it for you. You should get a better valve, you have a PVC barrel with a DWV fitting on it, I doubt it will hold extreme pressure so you may as well have fun with it at around 150psi with a better valve, better yet make a piston a valve and take it up around 400psi.
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Unread postAuthor: dongfang » Sat Sep 08, 2007 7:28 pm

Hi

Nice set of air cylinders there, but I also am a little confused abt what this is....

The spudding learning process is normally something like

a) You make a design

b) You build the thing

c) You evaluate, see how well it works

d) You reflect over what you imagined would happen vs. what really happened, then sometimes go back to a)

-- and most posts are related to one of these ;) It´s more or less expected :lol:

I´m seriously looking for a steel helmet and a pair of safety goggles for when I will take some of my PVC stuff to the rated pressure, 16 bar.

Regards
Soren

EDIT: Whoops, this is the showcase. Hmmmmm... OK.

How do you trigger the gun?

Regards
Soren
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Re: new to forum. Pneu Pneumatic

Unread postAuthor: MrCrowley » Sat Sep 08, 2007 7:36 pm

pretzelperson wrote:I have great concern with pneumatic PVC cannons and safety of chamber under pressure. Failure would be catastrophic and failure is unpredictable.


Unpredictable, yes. Catastrophic, not really.
I've had a PVC chamber blow on me and two other friends at 110psi and we were all safe, all three of us were within 1m of the chamber and one person was even holding it, next to his hip.

Success is not final, failure is not fatal, it's the courage to continue that counts.
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Unread postAuthor: thespeedycicada » Sat Sep 08, 2007 7:45 pm

cool very uhh colorful.Now paint it and put a modded sprinkler valve on it and itll be awsome the sprinkler alve is soooo much better than a ball valve.The power increase is amazing.
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Unread postAuthor: pretzelperson » Sat Sep 08, 2007 8:29 pm

MrCrowley wrote:Welcome.
Please refrain from insulting our members in your first few posts. Unless he said something really bad that was uncalled for we don't need to hear it.

Nice cannon, I've moved it for you. You should get a better valve, you have a PVC barrel with a DWV fitting on it, I doubt it will hold extreme pressure so you may as well have fun with it at around 150psi with a better valve, better yet make a piston a valve and take it up around 400psi.


Sure.

Thanks for moving the thread. As soon as I posted it I realized it was in the incorrect place.

The barrel is the "weak" link in the system, next to the shraeder valve. The valve is actually not a DWV fitting. I think a DVW fitting would be a plastic pvc fitting? It is a brass ball valve. The data on the valve indicates it is rated to 600 or 900 PSI, I don't remember. It is rated for gas.
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Unread postAuthor: Hubb » Sat Sep 08, 2007 8:43 pm

pretzelperson wrote:The barrel is the "weak" link in the system, next to the shraeder valve. The valve is actually not a DWV fitting. I think a DVW fitting would be a plastic pvc fitting? It is a brass ball valve. The data on the valve indicates it is rated to 600 or 900 PSI, I don't remember. It is rated for gas.


He was referring to the reducer bushing on the barrel. Anyway, you could always go for a metal barrel. I'm thinking we want to see some real power come from this thing (at least I do anyway :) ).

Also, have you heard of the GGDT? If not, check the wiki to get the download. The program will help you to maximize the performance of this thing. As far as a modded sprinkler valve goes, I think the ball balve in place is a better option, due to sprinkler valve only holding 120 to 150 psi.
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Unread postAuthor: MrCrowley » Sat Sep 08, 2007 9:57 pm

Yes hubb017 is correct, i was referring to the bell reducer on your barrel.
To get optimum performance I sugest you either

1) Get a metal barrel and take it up to 500psi+ and get good performance.

2) Build a metal piston valve and get a metal barrel for it and take it up to at least 400psi+ and get incredible performance

3) Keep the plastic barrel, swap it for a sprinkler valve and keep it around 135psi and get good performance.
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Unread postAuthor: pretzelperson » Sun Sep 09, 2007 7:10 am

You guys have given me a bunch of new ideas about how to take this thing to the next level. Thanks.

I downloaded the GGDT. Pretty cool. I'm not clear though how to account for the deduced fitting beween my air chamber and the valve. The bottle necks down to .5" and it opens back up to the 1" ball valve. I'm sure I am constricting flow from the chamber to the barrel.

The plastic barrels are left-over from my old PVC pneumatic. The large barrel is actually the old pressure chamber with one end cut off.

I think before I change the valve I need to learn how to build enough pressure inside the chamber. I have a little pancake air compressor, but it only goes to about 130psi. I can them pump with my bike pump to about 160psi.

There are decent plans on this forum to make a high pressure "bike" pump. The supplies are readily available here where I live. A local plumbing supply store has a nice check valve that would work well. I think if I made the pump about 4' long I would be able to pump enough volume with each stroke to pump my o2 cylinder up in a resonable amount of time. At current pressures there is no need for a metal barrel.

Any ideas about how much pressure a good shraeder valve will hold? The one I sued seems to be of decent quality. It has a metal flange on the back with a rubber gasket that is compressed onto the inside of the reducer fitting by the nut shown in the picture above.

Has it been determined at what pressure a potato comes out of the barrel as a mashed potato?
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