Semi-Automatic Combustion Cannon Concept

Boom! The classic potato gun harnesses the combustion of flammable vapor. Show us your combustion spud gun and discuss fuels, ratios, safety, ignition systems, tools, and more.
Bowman
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Sun Apr 15, 2012 3:28 pm

@al-xg that's a great idea, I'll defiantely try to incorporate that somehow, but I'm skeptical because it would require a complete redesign, because I design everything around the cycle of the bolt. But hey, it's a great idea, i'm almost done designing the fuel injector as well as a way to bring air into the chamber for the fuel-air mix. I will have it up in a little while.
Bowman
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Sun Apr 15, 2012 5:09 pm

Don't mean to double post. But I figured out a way to get air into the combustion chamber for a fuel mixture. And yes I've already redesigned the entire thing to incorporate this system. The entire purpose of this thread is for me to try and make this gun as efficient as possible.

Here's how it works (please excuse terrible animation). The propane is pumped into the combustion chamber (not in picture). Then it's ignited (not in picture), when it's ignited it creates pressure and moves the spring loaded "piston" in the rear of the chamber backwards which is connected to a valve that releases a certain amount of air from the air tank it's connected to into the chamber. So, the good part about this is that it only puts air into the chamber when the propane is ignited. This is good because it causes the explosion to propel forward. Kind of like what happend in this video (which I do not own and will never claim to do so):
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jackssmirkingrevenge
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Mon Apr 16, 2012 12:48 am

No need for an air tank. You can have the piston flow past some vents in the chamber like so:
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hectmarr wrote:You have to make many weapons, because this field is long and short life
Bowman
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Tue Apr 17, 2012 8:06 pm

Yes, that would work, and it will cut down on weight dramatically. I mean with my design I pretty much gave up and made it an turret mounted weapon only put this will definately make it to where it can be shoulder mounted. Thanks. I'm gonna see if I can get my new design of this gun up soon. Later...

EDIT: Question, why do you need to mix propane and air together? I know it's a good thing but what happens when you don't?
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MrCrowley
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Tue Apr 17, 2012 8:25 pm

Bowman wrote:EDIT: Question, why do you need to mix propane and air together? I know it's a good thing but what happens when you don't?
Propane needs an oxidiser to combust. The oxygen in air acts as the oxidiser for the reaction. If you fill a chamber with 100% propane and try to ignite it, nothing will happen.
Bowman
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Tue Apr 17, 2012 10:18 pm

I was thinking about just mixing the air and propane before I put it in the gun. Then building a custom tank on the gun itself that has a fan in it to mix the fuel before it's pumped into the combustion chamber and some kind of valve that allows you to refill it from a external source. Still working on the rest of the cannon in flash animation.
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