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Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Unread postAuthor: paaiyan » Tue Dec 04, 2007 9:13 am

Of course you can always go back a little further, to the origins of potato cannons, like the coke can tennis ball launchers of yesteryear. Cannons have definitely evolved over the years, and I think they will continue to do so. We have hybrids and high-pressure pneumatics now, but ask yourself, what comes next?

And back on topic, I still have a hard time believing this guys claims without pictures, and his statement about losing a 3 pound chunk of steel he launched in the burbs doesn't do anything for his credibility in my mind.
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Unread postAuthor: Zen/// » Tue Dec 04, 2007 9:51 am

the weak point is the ball valve rated for 600 psi.


:evil: Always keep it under the weakest part pressure ALWAYS!!!
:cussing:

Pictures+vid please.
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Unread postAuthor: jackssmirkingrevenge » Tue Dec 04, 2007 3:48 pm

Of course you can always go back a little further, to the origins of potato cannons, like the coke can tennis ball launchers of yesteryear. Cannons have definitely evolved over the years, and I think they will continue to do so. We have hybrids and high-pressure pneumatics now, but ask yourself, what comes next?


The first reference I ever found to spudguns was the Holman Projector fitted to British merchant shipping during world war two. Originally designed to fire hand grenades into the path of German bombers, in quieter times they were reportedly used to while away the boredom by firing potatoes at other ships within the convoy ("The Secret War 1939-45" by Gerald Pawl) - certainly advanced spudguns by any standards.
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Unread postAuthor: Ragnarok » Tue Dec 04, 2007 4:59 pm

I have to protest the behaviour of "Pics please!!!!" and "VIDEO!!!!" - or worse, just "VID!" - not only here, but in lots of places.

Come on, that reeks of n00b so much I had to get the Febreze out - not to mention the poor grammar and clipped sentences make it sound like you have to type quickly else you won't have time to get to the toilet before you wet yourself with excitement.

Please, expand on your sentences, and put some substance into your posts. Raise the bar a little. Lots of people would char-broil a newbie for doing what you do on occasion. Set a better example.

</rant>

Yup, JSR, you are certainly have had major effects on the high pressure revolution - but I can see it going further than just higher pressures. It's becoming high pressures in high volumes.

@paaiyan: Well, it's hard to know where it's going next. Power will advance, but it can only go so far without impractically large launchers or insane pressures you can't contain.
After that, I think the next step is likely to be enhancements to rate of fire across all fields, because you can only push the pressures so high with the materials available without spending a fortune.
I think I could possibly push a combustion to 1500 rpm if I had the time and money - thing is, I don't.

Accuracy is likely to be a late development. Normally if I can reliably hit a target at 10 yards, that's fine.
I'm not particularly interested in the main route for accuracy at the moment - darts - I don't like to invest much effort into ammo unless I can recover it reliably and mostly intact.
I prefer my power and range to be cemented in the launcher's performance, not the ammo's. A launcher is a one time cost, ammo isn't.

If I had looked forwards two years ago, I wouldn't have expected what I see today. What I will see in two years will surprise me less, but I still want it!!!
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Unread postAuthor: DYI » Tue Dec 04, 2007 7:16 pm

I would have to agree that we may reach the limits of what is practical with gas powered launchers in a few years. My detonation gun idea may turn out to be an advancement in velocity potential, but not particularly practical to operate. Most of us can't practically obtain pressures greater than 6kpsi, and most of us can't build guns that use shock heated hydrogen or detonations or extremely high pressure steam, so the limits are approaching. By the end of next year, I could see there being 5 or more launchers using 2000+ psi, and maybe the same number of hybrids using 10x or higher mixes, something that must have been absolutely unimaginable one year ago.

I'm inclined to believe the claim about the shot at 600 psi though. I've seen the picture of the oxygen bottle pneumatic, meaning that it likely does exist. But when I see a video of this thing, with the pump beside it, hydraulic QEV, 10' barrel, and an attached gauge reading 5kpsi and a sign beside it saying pretzelperson and spudfiles, I'll be convinced. Because this is quite a claim, the kind of thing that logistics prevents most people from doing.
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Unread postAuthor: VH_man » Tue Dec 04, 2007 7:27 pm

didnt mythbusters make a 5000PSI nitrogen cannon?

the valve was simply a spring-loaded ball valve and the thing could fire a 10 pound hunk of steel fast enough to do serious damage, even with the barrel about 6 inches long.

if anone remembers correctly the cannon shot itself bakward so fast that it smashed the hispeed camera to bits.

if you really fired that hunk of steel, i am doubting the current existence of your hands..........
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Unread postAuthor: DYI » Tue Dec 04, 2007 7:56 pm

The 3000 psi nitrogen cannon was a major improvement in the Mythbusters' cannon design. It's like they suddenly realised the extent of the materials available to them. The valve was not a spring loaded ball valve, but some sort of high pressure solenoid valve. And it didn't smash a high speed camera, it just smashed some random materials and then a concrete wall.

There were several reasons for its hideous recoil; the projectile weighed more than the cannon, the chamber was ridiculously oversized, meaning that the mass of the gases themselves contributed significantly to the recoil, and the cannon was not tethered. They developed a healthy respect for it after that incident, although using a high pressure vessel that had just been slammed into a wall faster than you could throw it is a rather questionable practice.

Do you really think that someone would actually hold a cannon composed of a medium sized oxygen tank, ten feet of steel barrel and charged to 600 psi and fire it from the hip? You seem to be making that assumption, but it was probably either braced on the ground or tied down to something.

All of this speculation is irrelevant however, if pretzelperson doesn't post some proof.
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Unread postAuthor: VH_man » Tue Dec 04, 2007 8:09 pm

haha i know ive made the mistake of firing heavy projectiles out of large cannons, completely forgetting about newtons laws............

but yes, PROOFF.
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Unread postAuthor: Novacastrian » Tue Dec 04, 2007 8:43 pm

I would think twice before firing anything over say 5 ounces in weight from my Hybrid- a 4x mix with a 1/2 ounce weight has enough recoil. (the gun weighs 4.4kg)
5 ounces would have recoil like a large centre fire rifle.
I believe that pneumatics would recoil more due to the fact that the gasses from a Hybrid cool down very quickly after combustion, am i right?

Oh yeah, Pictures and or a Video would be a great way to detail the existence of you launcher Pretzelperson.
*Pretzel Person posts proof pertaining to potato pusher* The new seven p's :D
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Unread postAuthor: ShowNoMercy » Tue Dec 04, 2007 8:45 pm

Completely off topic, but are there such thing as large caliber rim fire cartridges?
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Unread postAuthor: Ragnarok » Tue Dec 04, 2007 11:59 pm

There have been rimfire cartridges above .50 cal, but they are very rare these days.

Thinking even further into the future - not one or two, years, but ten or twenty, I can see a weird situation with my children, if I ever have any:

Teacher: Today, we're talking about things that go fast!!! Who can name something that goes fast?
Various Kids: Car! Motorbike! Train! Plane! Bird! Potato!
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Unread postAuthor: jackssmirkingrevenge » Wed Dec 05, 2007 12:06 am

ShowNoMercy wrote:Completely off topic, but are there such thing as large caliber rim fire cartridges?


The civil war era Spencer carbine fired a massive rimfire round:

Image

I don't think these are still manufactured though, the largest current rimfire round I can think of is the 9mm flobert made for "garden" shotguns.

Image
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Unread postAuthor: pyrogeek » Wed Dec 05, 2007 12:06 am

Rimfire cartidges are a design failure in my opinion. They don't burn that cleanly, duds are more common than with centerfire ammo, you can't reload them (with 22lr and such, it's not a cost stand point, but rather a matter of tailoring a round to your gun), the flame from the primer just start at the rear instead of getting shot into center mass of the powder like a normal primer would.
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Unread postAuthor: Infernal Maveric » Wed Dec 05, 2007 9:01 am

I have not read the whole topic, but only the first few posts so please excuse me if some of the things I bring up have been mentioned.

1. DO NOT USE PVC FOR THE BARREL!
2. DO NOT USE COPPER FOR ANY OF THE GUN
3. DO NOT STAND NEAR/HOLD THE GUN WHEN FILLING/FIRING
4. DO NOT USE A SPRINKLER VALVE
5. DO NOT ASSUME YOU WILL LIVE IF ANYTHING GOES WRONG.


Ok. Sorry about the caps, but this guy i asking for a Darwin award and a clean-up squad to find his body parts.

If you do (which I strongly advise AGAINST doing) build this gun then make sure that it is ALL pressure rated to the 17k PSI that you will (regrettably) be using.

A PVC barrel will explode much like a hand grenade at those pressures and kill at close to long range at those pressures.

A sprinkler valve can handle no more than 200 PSI, and 17,000 is almost 1000x times more than it is rated to.

The recoil of the gun will break your bones/kill you. Because if it has say 1000ft/lbs of force exhorted on the projectile, there will be 1000ft/lbs of force acting on your shoulder/chest. Big outchie.
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Unread postAuthor: Ragnarok » Wed Dec 05, 2007 9:47 am

@IM: I see some mistakes
1: 17,000 is only 85x times larger than 200, not 1000x
2: Recoil energy is not equal to muzzle energy. If you multiply muzzle energy by the mass of the projectile, then divide by the launcher's mass, that is accurate if you ignore the huge mass of the gasses. If any firearm had the same recoil energy as muzzle energy, you would have a problem.

Even the ultra heavy recoil .460 Wby Magnum cartridge only just has the same recoil energy as the .22LR has muzzle energy. (~110 ft lbs)

3: It's being done in an oxygen tank at only 5000 psi, if it's even going to happen at all, and if you'd read the topic, you'd know that.
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