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Floating barrel combustion cannon

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
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Floating barrel combustion cannon

Unread postAuthor: Cpt Obvious » Mon Feb 06, 2012 5:33 pm

I'm designing a combustion cannon with a floating barrel and shell loaded, based off of the pneumatic cannon here http://www.pukindogspaintball.com/cannons/BECC.htm

My intention is to apply it to paintball (or airsoft as the case may be) but simplify the build and reduce build cost (palmers regs are expensive). Any suggestions or knowledge would be appreciated. Especially with the C:B ratio (I want decent range but not so fast I will injure somebody). I'm considering further modification (lower section storage for other shells, propellant can etc). When I get the parts and start the build I will post pictures, any and all input is appreciated.
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Unread postAuthor: jackssmirkingrevenge » Tue Feb 07, 2012 12:23 am

If you want a combustion that can be reloaded quickly without complicated on board fuelling systems, go with cartridges: http://www.spudfiles.com/forums/cartrid ... 20150.html fuelled with a syringe: http://www.spudfiles.com/forums/how-to- ... 22301.html

Otherwise you have to make something like this, good luck :) http://www.spudfiles.com/forums/say-hel ... 23700.html
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Unread postAuthor: Cpt Obvious » Tue Feb 07, 2012 1:30 am

I actually stumbled across your cartridge design before, a fantastic piece of engineering btw, but I decided against it for a few reasons.

The first being that I am not confident in my skill of building a reliable system to properly connect with the ignition contacts in the cartridge and still be easily interchangable. (looking close at the design I think I might be able to pull it off, but would it require more than just a simple piezoelectric ignitor?)

The second being I was intending to use a payload similar to the sabot round designed by the original designer above, and I forsee technical difficulties (like fast leakage around a payload of airsoft bb's). And on top of that even if the leakage was rather little, say 30 minutes into my scenario, or an hour, it seems to me a fizzle and weak round seems inevitable.

My thought for its application would be the shell would be loaded but no propellant in the combustion chamber until it was needed, then fired, and reloaded as needed. It would be similar to the grenade launchers or mortars in paintball and airsoft, but with improved range (the biggest airsoft 40mm grenades are very slow and become ineffective after about 15 yds).

As far as the complex build based off the C3, its rate of fire is higher, and probably more reliable than mine. But my goal in this project is to build a combustion version of the gentleman who I linked above, I will see if i can rework the design of my projectile to make it nearly airtight. If I can make it work your design would be a vast improvement and i'll be all over it like ugly on my sister.
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Unread postAuthor: jackssmirkingrevenge » Tue Feb 07, 2012 1:56 am

Cpt Obvious wrote:The first being that I am not confident in my skill of building a reliable system to properly connect with the ignition contacts in the cartridge and still be easily interchangable. (looking close at the design I think I might be able to pull it off, but would it require more than just a simple piezoelectric ignitor?)


Image

That's all there is to it. The bolt design ensures that no matter now the cartridge is oriented, it will always complete the circuit.

Another way to go about it is to have front and back contact points as I did here:

Image

The second being I was intending to use a payload similar to the sabot round designed by the original designer above, and I forsee technical difficulties (like fast leakage around a payload of airsoft bb's). And on top of that even if the leakage was rather little, say 30 minutes into my scenario, or an hour, it seems to me a fizzle and weak round seems inevitable.


Poppycock, your projectile doesn't have to be completely airtight. It would take weeks if not months for the gas to leak out. To be 100% sure, all you'd have to do is cover the mouth of the cartridge with a bit of tape.

As for sabots, I recommend this method, but using paper instead of foil to make it safer. The end result should be tight enough to seal the gas in for long enough. http://www.spudfiles.com/forums/sabots- ... 23677.html
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Unread postAuthor: Cpt Obvious » Tue Feb 07, 2012 2:13 am

ah I see, looks like I will rework my design, see how it stand up then.
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