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Listen to what the man says!

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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Listen to what the man says!

Unread postAuthor: Mopardik » Mon Sep 26, 2011 11:46 pm

Like the title says. Well, not one man exactly, but the many regulars on this site. I recently completed the second version of my first combustion cannon. It was originally a spray n pray, but I've since converted it to metered propane with a mixing fan and dual spark ignition. I could not be happier with the results! Big power, and a shot with every click!
I just wanted to say that although sometimes the answers given on various questions on this site are somewhat curt, to say the least, there really is EVERYTHING needed to build an awesome cannon in the wiki, or with the search function. Seek and ye shall find! I have posted pics of mine in the showcase, if anyone wants to check it out. Many thanks to all those on this site that helped me (albeit unknowingly) to make mine a total hoot to play with! Well done, SpudFiles!
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Unread postAuthor: jackssmirkingrevenge » Tue Sep 27, 2011 12:50 am

That's certainly very uplifting to hear.

I think it's down to the type of individual who visits the site. If you're just seeking reinforcement for an existing idea or concept, you're not going to get far unless it was brilliant to begin with. Approaching the forum with an open mind and a will to do your homework makes the results speak for themselves.
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Unread postAuthor: jimmy101 » Tue Sep 27, 2011 5:00 pm

Mopardik

Thanks for the post. Your gun looks great (it is at
http://www.spudfiles.com/forums/second- ... t23389.htm ).

That's one serious barrel.

Did you put a small inner bevel on your spud cutter? That's about the last thing you can do, after metering and fan, to get the most out'a the chamber and barrel combo.

Now all you need is a bandolier for a dozen or so russets...
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Unread postAuthor: Mopardik » Tue Sep 27, 2011 9:16 pm

No problem, Jack. You and Jimmy are two of the "regulars" I was speaking of, whose posts helped me along the way. I spent many a night combing through old stuff on this board. Thanks again! Yeah Jimmy, it is quite a barrel, huh? Six feet of 2", to be exact. It gives me a nearly perfect ratio. I did put a bevel on it to help with cutting the spuds, but I did not cut an inner one. I can see how that would help with them sealing inside the barrel. Ha, one trick I missed! You can be assured I'm on it now, though! Also, my buds and I were actually joking about carrying this thing around with tater bandoliers and a bandana, Rambo style! And yes, we are dorks! :D
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Unread postAuthor: jimmy101 » Thu Sep 29, 2011 7:22 pm

The inner bevel actually does two things. It improves the fit and it boosts the static friction between the spud and the barrel.

It turns out, somewhat unexpectedly, that a combustion gun works a bit better with more static friction. The higher static friction delays the start of movement a bit and lets the chamber build up more pressure. Combustion is a pretty slow process and delaying the movement of the ammo by 5 or 10 milliseconds helps.

Only problem with the double bevel is that if the inner bevel is too much of the barrel's wall thickness then the spud is cut too tight and it will turn to mush when pushed with the ramrod.
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