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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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Unread postAuthor: MrCrowley » Sat Aug 27, 2011 7:16 am

pneumaticcannons wrote:ur reducers arent rated... doesent matter though as long as you keep it below 80 psi

You can get pressure rated reducers. Egoyte, look on the fittings to see if they say "NSF-PW", if they don't have that or a pressure rating written on them but instead only "NSF-DWV" then your fittings aren't rated for pressure.
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Unread postAuthor: Technician1002 » Sat Aug 27, 2011 10:21 am

Egoyte wrote:The removed one is a potato to the head - while wearing an incredibly strong helmet.


The reason for the rule is to prevent copycats. Not all spudguns deliver velocities helmets and eyewear is designed to withstand.

Damage is from a rotting apple picked up from under an apple tree.
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Unread postAuthor: saefroch » Sat Aug 27, 2011 10:38 am

I've launched a barrel and a spark plug, both by accident. On my first pneumatic cannon I built, the copper barrel was secured to a 3/4" nipple with some interesting use of tape. It held to 150psi, but not 200. It launched downrange at the target while I was once preparing to fire. I also recently launched the spark plug from the epoxy housing on my hybrid. I had only painted the outside of the spark plug to seal it up before pouring epoxy inside (which would have held it). I over pressurized, got up to 400psi or so and it detached.

Make a piston valve and get some proper pressure-rated fittings. You'll be amazed at the difference it all makes.
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Unread postAuthor: Egoyte » Sat Aug 27, 2011 12:33 pm

A C-battery... Taking out your window seems like one of the less-destructive ways that could've gone! Decidedly a live and learn scenario...

Technician: Aye, that'd be why I nixxed that one myself after thinking about it a moment. Our air cannon actually didn't launch at speeds "safe" for the helmet... The final shot destroyed the F5 hurricane rated protection, and made me deaf in one ear for about 4 minutes... So yeah. I'm with you. That one should not be emulated under any circumstances.

McCrowley and friends: See, I honestly hadn't thought of that (reducer ratings). My short-haired friend is the one with the prior past professional experience in PVC, and informed me of the "limit".

Makes more than enough sense though, I have to admit I was somewhat surprised to hear the tank at the end was rated, so it doesn't surprised me to hear the other parts we used aren't.

OK, well then, here's another question: The inside of the reducer is coated in an epoxy (we went over-board attaching it). Don't ask me which kind I didn't buy it, though your responses have guaranteed that I'll start paying closer attention to the details.

So... Just how likely has our precocious precious been to explode (or explosively depressurize) in our hands? I'll admit we've taken it to 110 against our own warnings...

The monkey is smarter than he allows himself to act, I swear. White-collar consultancy gets to be a boring life sometimes... Need to spice it up somehow.

Was about time to build a new one anyway... And yeah, you guys have given us some new idea... Don't worry, I'll not post all the fun ones. Rules are rules ;)

Sae: Aye, see, it's stories like this that drive home just how far you folks have come collectively whilst I was ignorant of your existence... My friends and I were well aware that one could safely create a machine like this that'd do 400 PSI, but we weren't aware that people had somewhat normalized the practice of doing it in their backyard...

Your story, and those like yours, have my utmost gratitude, good sir.
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Unread postAuthor: Technician1002 » Sat Aug 27, 2011 12:49 pm

The mention of accidental launches is another good point. I had an accidental launch. I launched the piston out of my ABS cannon once. I started to air it up and noticed it was leaking. I tried to re-seat the piston and got it pushed in just a little too far. The wimpy cord is not up to the task of preventing a piston launch.
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Unread postAuthor: jhalek90 » Sat Aug 27, 2011 1:04 pm

Why did you attatch the end cap with epoxy??? That may have made it weaker. A properly cleaned and solvent welded endcap is actually "welded" to the chamber. Much stronger than epoxy.
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jackssmirkingrevenge wrote:I wonder... if you put flammable vapours inside a lady... could you get her to diesel?

POLAND_SPUD wrote:Anything is possible with the proper 3-way valve.
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Unread postAuthor: Egoyte » Sat Aug 27, 2011 2:33 pm

Because I work with computers for a living.

So, basically meld the plastic together... Yeah, that does sound like a much better idea than "strong glue."
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Unread postAuthor: Egoyte » Sat Aug 27, 2011 2:51 pm

Man, yeah, the more of this site I read, the more instructables I see...

Incredible resource. So glad I found you guys. Learning me some new skills that my family already wishes I had less of. Much obliged :)
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Unread postAuthor: Crna Legija » Sat Aug 27, 2011 7:12 pm

Have a read though this to learn how to solvent weld correctly
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Unread postAuthor: Egoyte » Thu Sep 08, 2011 7:15 pm

Solvent welding is decidedly the plan for the next one.

Learned more than just that from going through spudfiles, here; We're going on a material run for our next cannon this weekend, after we finalize the plans.

Big. If our math's right (and we'll re-check it), should be able to do 300 PSI without a problem, and we're going to spring for a digital pressure readout and an electrically controlled valve, so we can roll out some cord and get far away from the damned thing.

I'll be sure to keep you apprised.

I actually was about to post our latest video with the same cannon from the top of the thread, but being an idiot, I put together three different shoots into one video... And one of the three violates the same policy I violated before. So... Crap.
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Unread postAuthor: jhalek90 » Fri Sep 09, 2011 7:45 am

I hope you dont plan on using 300 PSI in PVC pipe.... i dont care what the size. PVC is not intended for air pressure, of any sort. Even pressure rated PVC can fail.... and when it does, shards of sharp radiolucent (invisible to x-rays) plastic can embed them self in all sorts of soft targets. (your body.)

X-ray invisible shards in your body is not goin to end well for you.

On another note, hardware store galvanized, and "black" iron pipe is a GREAT choice for 300psi. Ive taken 1'' black iron pipe to much higher pressure than 300 psi. :-)

Good luck on your future venture.
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jackssmirkingrevenge wrote:I wonder... if you put flammable vapours inside a lady... could you get her to diesel?

POLAND_SPUD wrote:Anything is possible with the proper 3-way valve.
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Unread postAuthor: DYI » Fri Sep 09, 2011 11:06 am

jhalek90 wrote:I hope you dont plan on using 300 PSI in PVC pipe...



Egoyte wrote:we're going to spring for a digital pressure readout and an electrically controlled valve, so we can roll out some cord and get far away from the damned thing.


He's already clearly stated that he'll be remote firing, so any failure won't be any more than an expensive *thump* in the distance. Also, PVC is certainly NOT invisible on x-rays, as has been demonstrated on this forum in the past.
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Unread postAuthor: Egoyte » Fri Sep 09, 2011 2:05 pm

Yeah actually, the next one is PVC. Plans for the one after to start with metal.

As it is, the next one is basically conceived as the end-all PVC cannon, from our perspective (though I know it'll still be humble compared to some of the work around here), so if it in fact ends its life by exploding in a burst of shrapnel, I at least will see that as an appropriate all-consuming end.

From a distance. With a camera.

Good to know on the galvanized and iron pipes, that'll come in handy soon enough.
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Unread postAuthor: jhalek90 » Fri Sep 09, 2011 6:06 pm

DYI wrote: PVC is certainly NOT invisible on x-rays, as has been demonstrated on this forum in the past.


D_Hall wrote: The problem is that PVC is similar in density to flesh and as such it won't show up on X-rays at the emergency room.


Psycix wrote: Its only visible in the parts where the walls are parallel with the angle of view. The flat (perpendicular) pieces of pvc are hardly visible. (and the rays have to go through TWO wall thicknesses!)
This would mean that for optimal PVC shrapnel detection, you will need to make multiple X-ray snaps from different angles, as the shards will be invisible when the shard is perpendicular with the angle of view and clearly visible when its pointed straight toward the cam.



Polyvinyl Chloride, is radiolucent, to some degree. Not invisible, simply radiolucent. I stand corrected.

Back on topic.
If you do put 300 psi into PVC pipe, get ready for the loudest noise you've heard in a while. when it does explode, it will be violent.
Please video tape it!!! :-)
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jackssmirkingrevenge wrote:I wonder... if you put flammable vapours inside a lady... could you get her to diesel?

POLAND_SPUD wrote:Anything is possible with the proper 3-way valve.
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Unread postAuthor: Egoyte » Wed Sep 14, 2011 2:21 am

New video, same old cannon. Since the "hundreds of little glow sticks" thing didn't photograph well, we got four thick glow sticks that, arranged just so, barely fit into the chamber next to each other.

Much more visible, though the 720 HD version does it much more justice.

[youtube]http://www.youtube.com/watch?v=WWQXm-VzYDA[/youtube]
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