SpudFiles

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Some questions to help us help you:

- what are you trying to achieve in terms of performance? Specific range, specific penetration... what would you like your launcher to be able to do, and what sort of range do you have to shoot over?

- what's your budget?

- what facilities do you have available in terms of tools, materials and skill level?

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I made a cannon, using 9 feet of 4' and a 2' ball valve, and it has power. It cost about $50. If you're willing to spend more, you could build a piston valve or buy a 2' sprinkler valve which are usually $50.

millons70 wrote:I made a cannon, using 9 feet of 4' and a 2' ball valve, and it has power. It cost about $50. If you're willing to spend more, you could build a piston valve or buy a 2' sprinkler valve which are usually $50.

For 30 bucks on ebay , get a dust collector plenty of power nd easy to build a good powerful cannon:)

What size dust collector for $30? And would it be better than a super easy "flick" 2 inch ball valve?

millons70 wrote:What size dust collector for $30? And would it be better than a super easy "flick" 2 inch ball valve?

1.5 ,, they are a lot more powerful trust me! Just a couple brass fittings nd pvc pipe nd a barrel nd booom away!

I would make a basic combustion cannon first.

A large bore (say 2-3") will give you plently of power, you will get some experience with PVC construction and ballistics in general.

When you say the big thing for you is noise, do you mean you want more or less? both a pneumatic with a fast valve and a combustion are pretty loud.

Due to muzzle flash, a combustion of the same size can be much louder than it's companion air cannon while the combustion provides less power.

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Satasaurus wrote:Thanks for the replies guys. I'm pretty sure I'm gunna go with a combustion but I'm still pretty torn. I guess I could always just build both.

Nobody is forcing you to build just one

A couple other things I was thinking of are: is there any safe way to make a combustion cannon also pneumatic. Basically I was just thinking maybe I could put a ball valve in between the combustion chamber and the barrel and just always leave it open when I'm using it as a combustion cannon? Or would that be dangerous?

That would work, but if you're making it out of PVC I would be a bit worried that the repeated shock of combustion firing would make it possible that it would then be less safe if filled with compressed air.

Also, is schedule 80 pvc a lot better then schedule 40?

For a combustion, 40 is more than enough.

Finally, how loud are we talking about with the combustion cannons? Neighbors calling the cops loud? Cap gun loud? Thanks again.

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Pretty loud. Even if built with an efficient configuration (small chamber and long barrel). If noise is an issue, you might want to consider making a suppressor.

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If you were to go with a combustion, the C:B ratio can be anywhere between 0.8:1 (the chamber is 80% the volume of the barrel) and 1.5:1 (the chamber is 150% the volume of the barrel). It all depends if you've got a barrel or chamber volume that is fixed.

Let's say you've got a 5 foot length of pipe you're going to use as your barrel. It's volume is, say, 1000 cubic inches for simplicity's sake. So if you're stuck with a fixed barrel volume you should shoot for a C:B ratio around 1.5:1 for the fastest velocities. Again, to keep things simple, let's say you use the same diameter pipe for your chamber (not recommended). So a 7.5 foot length of pipe would give you a volume of 1500 cubic inches for your chamber. And so we get a 1500:1000 C:B ratio, or 1.5:1

For a fixed chamber volume the best C:B ratio is around 0.8:1. So if your chamber is 800 cubic inches you would want your barrel to be 1000 cubic inches. So, 800:1000.

There's some good threads floating around that go into much greater detail on C:B ratio's, but first, check out Burnt Latke. It might be a good idea to run some numbers to figure out how big your cannon is going to be while also performing optimally. I trust you know how to calculate the volumes of cylinders. Good luck.

When I was in middle school, which was a long time ago, I made a pvc combustion, hair spray cannon. My friend and I went to a closed (for business) open pit gravel mine to shoot it. We were at least 150 yards from the closest backyard, which was forest. Also we were shooting the opposite direction. Cops were called, and though he was cool, actually taking a few shots with it himself, he confiscated the launcher. So yea, they're loud.