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Intro and first cannon build :D

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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Intro and first cannon build :D

Unread postAuthor: Glitch » Wed Feb 23, 2011 6:44 pm

Well i finally got to buiding one. Part of the costuming/prop rep community and for years have always wanted to. So here she is... The Elephante.
The barrel is 1 1/2 sch. 40 with a 2" air chamber at 2 feet long. I'm using a Rain-bird Sprinkler Valve as my opening, and in line I have a safety on/off switch, with the RED button as my trigger. The remote-line on the side, going to a External CO2 bottle and a Pressure gauge on the side of the air chamber. I usually run around 120 but im going to start messing around with pressures to see what gives me the best distances.

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Im already itching to build another one thats lighter and smaller. Some mods im looking to do is add a LED Armed light on the project box, and def. a Purge valve.
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Unread postAuthor: saefroch » Wed Feb 23, 2011 7:13 pm

I like it!
But of course, as with anything, there are some possible improvements.

-You have very large dead volume, which in this instance is the volume between the main valve and the projectile position
-I'm not sure if that end-cap is pressure-rated or not, but it looks rather sketchy to me
Even with the large dead volume, it's probably still pretty impressive. You'll also probably find that with higher pressure, the projectile travels farther.

Purge valve?
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Unread postAuthor: Gaderelguitarist » Wed Feb 23, 2011 7:54 pm

Well it's good to see that compactness was a big concern for you :D

Kudos though for thinking about using an on board compressor. Glitch, you will find that your valve is not the most efficient valve, especially considering that you have not even modified it for pneumatic action. Still, it looks like a decent build, and I look forward to see in what directions you spread.

Saefroch, I think the end cap looks ok. Thats what the pressure rated ones look like at my local Home Depot anyways.
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Unread postAuthor: Gun Freak » Wed Feb 23, 2011 7:56 pm

I think it's pressure rated also, although he did drill through one layer...
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Unread postAuthor: Glitch » Wed Feb 23, 2011 8:21 pm

It is pressure rated for the area im firing at. The gauge going Into my air chamber i wrapped with the tef. taping and used a glue to add to the sealing *I forget what its called, but the guy at HD said it would work good to help seal on the outside and inside for what i want to do* The purge valve yes, i saw it posted on another thread.

Saefroch -The purge valve yes, i saw it posted on another thread. It opens at a certain PSI so that the air chamber basically doesnt blow up in your face, or you manually open it. For the dead space, are you talking about chopping the barrel down? I have a ramrod for what I launch and get my projectiles about half to 3/4ths the way down the barrel usually.

Gaderel- How can I improve the valve? Are you talking about doing the pneumatic actuation method to it?

Thank you for the responses and suggestions ^^
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Unread postAuthor: Gun Freak » Wed Feb 23, 2011 9:02 pm

No, the dead space is the volume behind your valve leading to the barrel. The less dead space, the less time it takes for the air to get to your projectile, therefore better performance.
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Unread postAuthor: nadjatee1996 » Wed Feb 23, 2011 9:22 pm

-sigh- this makes me want to go down to my basement and start drilling/sanding/making away, too bad I still need a nipple, tube cutter and epoxy :(, quick question on a unrelated topic, you can make an easy detent by putting in an o ring between two pieces of pipe inside of a nipple right? I also read somewhere that cutting 2 slits on the top of bottom of a pipe, then putting the o-ring in the slits also makes a detent
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Unread postAuthor: saefroch » Wed Feb 23, 2011 9:51 pm

Oh, what you're calling a purge valve, I think we usually call a pop-off valve. Opens at a certain pressure or above, then vents down to a certain pressure and re-seals, yes? Good safety feature indeed.

When you ram the projectile down, there is all that volume through the elbow that the air expands into, but doesn't propel the projectile. It's like you're not ramming the projectile all the way down the barrel. To solve the problem, you'd have to move the valve from the chamber side of the 180 bend to the barrel side, so you can ram the projectile right up to the valve. All of my builds were done so that the projectile when loaded actually sits against the valve's piston, minimizing dead volume.
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Unread postAuthor: Crna Legija » Wed Feb 23, 2011 10:10 pm

Glitch wrote: I have a ramrod for what I launch and get my projectiles about half to 3/4ths the way down the barrel usually.

Gaderel- How can I improve the valve? Are you talking about doing the pneumatic actuation method to it?


make sure you ram your ammo the hole way down it will make your canon more powerful, dead space it the space in between you valve and ammo, in your cannon its the two 90* elbows.

this is how you mod a sprinkler valve
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Unread postAuthor: jackssmirkingrevenge » Wed Feb 23, 2011 10:32 pm

saefroch wrote:I like it!
But of course, as with anything, there are some possible improvements.

-You have very large dead volume, which in this instance is the volume between the main valve and the projectile position
-I'm not sure if that end-cap is pressure-rated or not, but it looks rather sketchy to me


Agreed, along with valve modding. Also, I would have attempted to incorporate the hangun frame, screwdriver, penguin and alarm clock into the design.
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Unread postAuthor: Gaderelguitarist » Thu Feb 24, 2011 1:46 pm

It might be irrelevant to modify your sprinkler valve for this cannon, considering you have a dedicated electrical system controlling your air source. If you plan on doing another build without an electric basis, use the link that -_- provided.

If you had moved your valve to the top of the construction, placing it directly behind the barrel, you wouldn't have as much of a dead space problem. The combination of dead space and valve opening time/ valve turbulence is really robbing your performance.
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Unread postAuthor: Technician1002 » Thu Feb 24, 2011 1:54 pm

Dead space is less loss than the undersized valve. The valve is NOT 1.5 inch. Between the dead space and limitations to flow when fired, I would recommend sticking with heavier projectiles. They accelerate slower and are a better match to the parameters of the launcher. It should do a decent job lobing spuds a fair distance.
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Unread postAuthor: Glitch » Thu Feb 24, 2011 6:27 pm

Hmm...thanks all for the advice. Thinking of the penguin mod i could jam the screwdriver into its head and use the alarm clock as a detonation timer. when it goes off...better move...

My next one Ive had a few ideas running through my head. I did see that video and that was 1 way i wanted to do. I wanted to make a AT4 or STINGER styled launcher, even though it goes completely against my compactness like i wanted, I think ill save it. Or something similar to this build but with bolt action and smaller. We shall see.....


I think my first True shot - Fruit Cup....
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