����I built me a new toy. It might even be something that would interest you.



����It's an extremely simple and rather small but very effective air pressure cannon, built from PVC pipe and a few other scraps. To those of you that engage in building these sorts of cannons mine is undoubtedly small potatoes (excuse the pun), but what's notable about this one is the fact that it cost me nothing at all to build. That, and I got it completely airtight. First try.
����I had the pipe and the tire valve kicking around already, as well as one of the reducer pieces. The rest of the materials the local Home Depot was kind enough to... donate. Either way, you're looking at paying about fifteen dollars to build a cannon like this, including the cost of full lengths of both diameters of pipe.
����To pressurize the cannon air is pumped in through a heavy duty schrader valve (originally intended to find a home on the wheel rim of a truck) with a bike pump:

����The valve can take 150 PSI safely. The same rating applies for the ball valve, which is the heart of the operation:

����Ball valves have to be actuated mechanically and are the lowest-tech way to operate your cannon. They're cheap and plentiful, though, as well as tough as nails and rated for some truly insane pressures. This valve is a half inch model - I was originally going to use a three-quarters but all the valves I could find were too hard to open quickly.
����All of this is bound to a detachable half inch barrel (I have a three-quarters barrel, as well) with no less than five reducing pieces. The chamber pipe is two inches, and the valve is of course one half, but there are apparently no straight-through reducers in the western universe that go from two to half an inch in one go. Or even in two goes. I wound up using a two to one and a half reducer with a one and a half to one bushing inside that, a one inch bushing into a three-fourths bushing, and a three-foruths to quarter inch bushing. This is then, of course, attached to a male threaded adapter with a one inch length of half inch PVC. Even with all the parts the fittingswould have cost a hair under five bucks.
����The power of the cannon is nothing truly spectacular, in the scheme of things, but it's quite impressive to anyone who hasn't handled a pneumatic cannon pumped to 125 PSI before. It can throw a fifty caliber mustketball a good hundred yards if you angle it right, and can blast a ball of air dry clay clean through five stacked up AOL CD's. Punching holes in things aside, the three-quarter inch barrel can also fire paintballs to insane ranges and lob cratermakers a considerable distance.
����All in all, good clean fun. Plans and digrams will be coming up shortly.

~Zero

you could probably get stuf farther if you make the barrel longer. That is what i will try to do.

Very nice....But nick,wouldn't a longer barrel make it more accurate and less powerful?

no, it would make it more acurate and more powerful. The longer the barrel, the longer the gasses have to act upon the projectile. I was doing to experimenting with a cheap 15 dollar BB gun i bought at walmart. I made a really thick and heavyweight paper tube, and neatly put it on the end of the barrel. I was shooting at a pop can, and without the paper tube, it went through one side of the pop can. Then, with a different pop can, I put the paper tube on(which i will replace with metal, or plastic) and it went through only one side of the pop can, but made a large dent on the other side. I would try it with my 450 dollar glock, but it would be incredibly hard to tell any difference with the power.

That's a good cannon, but I'll stick to combustion based devices.

I'd guess that there's a point of diminishing returns on barrel length. At some point, the friction inside the barrel will overcome the rapidly dropping pressure of the gas. Most valves only get so big, so the airflow is limited. The chamber on my air cannon is actually a bit too large, and all the air isn't used in a single shot. I could always put a longer barrel on mine, though, since it's just screwed into the valve with teflon tape...

Thats awesome!!! I especially like how you used aol disks. I HATE AOL!!!!!!

I'm pretty sure Zero knows this but it's usefull information for those who dont understand the barrel length to pressure chamber idea.

If you have a pressure chamber that's 2" wide ID (Innder Diameter) by 12" long then you have a .5" wide ID barrel it should be 48" long to take advantage of the chamber's total volume.

Think about it.. you'll get it. And I have one of those ball valves, I should make an aircannon this week...

The trouble is, though, that the valve doesn't move the pressure from the chamber to the barrel, it just equalizes it. If your barrel is the same volume as the chamber, you start accelerating the load with the same pressure as the chamber, but you're down to half that by the time the projectile leaves the barrel. If you have a 120 PSI chamber and the barrel is twice the volume, you've still got 40 PSI at the end of the barrel.

I may upgrade my barrel just so I can fit tennis balls and cans...

quote:

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Originally posted by deadkennedy:
Thats awesome!!! I especially like how you used aol disks. I HATE AOL!!!!!!

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Profile for deadkennedy

Date Registered: 11-07-2002
Status: Regular
Total Posts: 62
Current Email: snowboardkid56@aol.com

����So his parents use it. That doesn't mean he has to like AOL.
����I know the barrel length principles, and I do intend to make a much longer barrel for this cannon. Mine is so short because A) I want to be able to fit the thing in a backpack for now and B) that's the lonest scrap piece of pipe I could find.
����I'll be doing some range testing and whatnot today.

~Zero

Indeed that is cool Zero...

-Firewall

I made one of those myself i while back, before i had the balls to do explosives, it wasnt nearly as good as that one though, well done

quote:

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Thats awesome!!! I especially like how you used aol disks. I HATE AOL!!!!!!

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I just got DSL, alot better then that AOL shit.

Could I just use a full paintball tank and screw that into the ball valve if I can find the right size to fit the tank?

And yes a longer barrel will make it more accurat but I'm not sure on if it will make it more powerfull. If you rifle it it might.

when you rifle it, it makes it a little bit less powerful, but much more acurate. i never thought of rifling my barrel. im gonna do that soon.

����A paintball CO2 tank will have far too much pressure behind it to safely apply to PVC. It would blow your cannon up pretty much as soon as you screwed it in. Most PVC cannons can take 125 PSI as the absolute maximum, and CO2 tanks put out 800 or so (and I hear from others that I'm wrong and they can put out even more than that).

~Zero

quote:

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Originally posted by Zero the Inestimable:
����A paintball CO2 tank will have far too much pressure behind it to safely apply to PVC. It would blow your cannon up pretty much as soon as you screwed it in. Most PVC cannons can take 125 PSI as the absolute maximum, and CO2 tanks put out 800 or so (and I hear from others that I'm wrong and they can put out even more than that).

~Zero

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I think it could put out far more than that cuz all 20 oz of co2 would come out at once(not in small amounts like in a pb gun) and turn to gas resulting in a boom.

CTR

all 20 oz's coming out would result in a rather large whoosh, frostbite on any skin that's touching the tank, and a rather cold cannon...

you'd have to first find a suitable size co2 (say... maybe... a 12g?) and crack that into your cannon... that should be safe.

On the CO2 subject, wouldnt it be possible to use a pressure regulator (Not sure if that's the name.) I have one on my aircompressor, it has an intake of up to 300PSI and can tune the output from 300-0PSI? You could find one that handles CO2 pressures and tuen it down to 120PSI for the PVC connection. Though I'd imagine it would take a lot of parts for conversion, and the trouble that even though 120PSI is being pumped, the volume in important too...

����If you use a full bore 20 ounce CO2 tank with no regulator the pressure between the chamber of the cannon and the tank would try to equalize. Once it got about a fourth of the way though that, however, the cannon would explode violently.
����You could indeed use a 12 gram, but you would have to work out how much volume you need in your chamber to keep the full charge of the 12 gram at 100-125 PSI. If your chamber were too small you would have the same problem as you would with a larger CO2 tank (though probably not as severe), and if your chamber were too large the cannon would not fire very far.
����The regulator idea works quite nicely, but it is hard to find a CO2 regulator that you can wind all the way down to 100 PSI. I've seen people's cannons that do this, though. When you open the valve the CO2 will continue to flow from the regulator, since the cannon's chamber is effectively at 0 PSI, so you'd have to remember to close the valve after each shot to avoid wasting CO2.

~Zero

regulator... if you want to spend 110 on a regulator for a cannon...

����That doesn't mention the pressure that the regulator limits to, or if it's adjustable.

~Zero

Update away!
http://krimzonpyro.com/zero/

Nice new cannon section: http://krimzonpyro.com/zero/Cannons/Zero_Cannons.html

Thanks for making the match rocket movie, saves me from making a movie of it!

i never made those match rockets before, becuase i thought that they were crap, but they work a lot better than i expected.

����The one I lit just before I took the movie went about ten feet until it hit the wall, with no sign of slowing down. That was probably the most impressive one I've ever made. They're not good for anything by any stretch of the imagination, but they're fun to play around with while you wait for webpages to load and such.
����Regarding cannons, it may take a while for me to complete range testing and whatnot. As I've mentioned before, there is now a sizable construction site directly in front of the entrance to the place where I normally blow things up. Generally I would not be worried about this, but there is one minor fact: Namely, the bridge that I have to climb down to get to the blast site is no longer there. I could swim on over to ground zero at this rate, but at the end of November that's not exactly my cup of tea...
����I'll have to wait for them to rebuild the bridge and roadbed before I can do any serious testing. All that aside, I did fire off a few empty CO2 cartridges in the pneumatic in my backyard. I can get about seven seconds of hangtime before the cartridge falls to earth, so I predict some fairly impressive ranges once I get the thing out into open ground. I've fired some cratermakers from it, too, but my fuses are too short and they explode in midair.
����In any event, I've been working on cannon diagrams and photographs, so I'll have lots more content for the cannons page after Thanksgiving. I intend to draw up plans for all of the cannons already on the page, and possibly a few more besides.

~Zero

hopefully they can built the bridge before new years.

the longer barrle idea w/ make it longer but less powerful. if he was using a combustible thing ie gunpowder then the longer barrel would make it more powerful. but since the air pressue decreses as the surface area of the pipe increase. those longer the barrel the less power since he is using a limited amount of air pressure.

as long as the pressure is greater on the inside the longer the barrel the stronger the gun

Keep in mind that I haven't technically taken a physics class, and I've been up for about 36hrs, but anyway here are my ideas:

The ideal barrel legnth would be whatever equals the volume of the pressure chamber. When the projectile is at the very end of the barrel, the gas in the barrel should equal the gas in the pressure chamber. If the volume of the barrel is less than that of the pressure chamber, not all the gas will be used in accelerating the projectile. If the volume of the barrel is greater than that of the pressure chamber, all the gas will be used in accelerating the projectile, but the projectile will essentially run into more resistance from friction than acceleration from pressure. Man, am I ever tired though.. just here waiting for the electric bed warmer to unfreeze my bed.

����That is correct. As long as there is more pressure behind the projectile in the barrel than there is ambient the projectile will be accelerated. To account for the real-world effect it is often preferable to build the barrel to contain slightly less total volume than the chamber, but that's nitpicking.

~Zero

����The plans for this cannon have been posted, thanks to Rat-Bastard: http://www.krimzonpyro.com/zero/Cannons/Zero_Cannons.html

~Zero

I don't know how many of you are seriously into paintball, but i am, and instead of using a co2 tank i would use a dual regulated adjustable output nitro tank. It'll cost you about 450 new. then you could make your own set of valves or easil modify an autococker to release air at a constant pressure as long as the trigger is pressed. Just screw around with the front assembly until you get it right. After all if you short stroke it, a similar phenomenon occurs(well, not really) Anyways after you have spent probably near a grand, you have a sweet ass cannon not worth nearly that much.

����I think I'll stick with my five dollar bike pump. If you're dead set on a self-powered cannon CO2 will work just as well as nitro and will cost a lot less.
����Your second suggestion is just a waste of a perfectly good autococker. It completely defeats the purpose of a cannon that can be built for less than twenty dollars.

~Zero