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Semi Combustion?

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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Semi Combustion?

Unread postAuthor: freder » Mon Feb 23, 2009 3:13 pm

[youtube]http://www.youtube.com/watch?v=j5beZq9m2JA[/youtube]

I saw this and probably watched it 30 times and all the other vids of this gun but I still don´t understand it :?

Does anyone know how this guys cool gun works that good?
I mean he seams to just push something near his spray/gas and it fires each time and almost perfect...
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Unread postAuthor: sputnick » Mon Feb 23, 2009 3:18 pm

I have see semi automatic combustions before, it was a french one that had a tank of pre mixed air and butane compressed in a fire extinguisher bottle, then injected into a smaller chamber.

That does not look like the case here, it looks like hes just holding it upside down, squeezing the blue thing and firing...

Why not try PM'ing him and asking... you never know, he could divulge his secrets :wink:

I will be watching this thread...
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Unread postAuthor: Radiation » Mon Feb 23, 2009 3:52 pm

The problem with any semi auto combustion is exactly what you see here, they're weak as hell. If he could get this gun to decent performance I'd be impressed. Not knocking his design, it's quite a feat. It's just hard to get enthusiastic when I could throw the ball further than that, faster too.
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Unread postAuthor: freder » Mon Feb 23, 2009 4:17 pm

@ spudnick: This guy is frensh and he built that what you discribed
:lol: And thanks. now I understand how his other gun works :D this is probably a prototype

@ rediation: i agree on that with the performance.


[youtube]http://www.youtube.com/watch?v=PICgEsKW4yA[/youtube]

this is the gun spudnick meant, i think 8)
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Unread postAuthor: SPG » Mon Feb 23, 2009 4:33 pm

But that's not a semi in that video it's just a plain old combustion you can see him reloading it each time. All he's got in there is a butane gas canister (the blue bit he pushes on) usually used to refill a ciggie lighter. He vents using a return vavle in the end cap. If you look very closely you can see him pushing on the switch for the fan, just before he refills.

Here's his thread http://patator.frbb.net/vos-machines-et ... -t4240.htm

For that sniper rifle it is a straight bolt action combustion. He has a fire extinguisher filled with a pressurised fuel/air premix, which he uses to fill the chamber, then he loads a BB, then fires, then flushes out the combustion gases with a quick squirt of fuel/air mix, then repeats. It's not a hybrid though as the pressure of the pre-ignition fuel/air mix equalises with atmospheric pressure as he's reloading.
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Unread postAuthor: Radiation » Mon Feb 23, 2009 4:46 pm

Hell my gun can do that (when vent is opened) and it will put a dart through 3 two by fours.
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Unread postAuthor: psycix » Wed Feb 25, 2009 3:34 pm

I notice a muzzle flash coming out at the back of the gun. Especially for the one-before-last shot.
This could indicate venting holes. Maybe he just has a fan and some holes covered by some flaps.
For injecting fuel, I think he measures just by counting seconds while pressing down on something like a butane lighter refill can.
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Unread postAuthor: ramses » Wed Feb 25, 2009 5:53 pm

maybe he just forgot to close a ball valve vent or something, because it wasn't present in the video after (where any damage to the back would have made the muzzle flash again)

or perhaps his camera had the shutter closed during the actual combustion
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Unread postAuthor: starman » Wed Feb 25, 2009 7:54 pm

He has a clear combustion chamber and that motor sound you hear is him refreshing the chamber...actually sounds pretty cool. He probably does have some sort of a check type valve door on the rear there....it didn't close very well on one of his shots.

Does anyone have any idea what he's using for ammo there? I can't really tell...looks light and soft...maybe campfire marshmallows?

Yeah it's really a toy but I like to concept overall.
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