Question About My Cannons Performance

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.
Explosive
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Sun May 17, 2009 12:00 pm

Hey guys, I'm new here and this is my first thread/post. So I figure I'll start by telling you my past with potato cannons then post my question, my friend and I decided we wanted to make one, he made one, I made one, they were cool, he ended up selling his first one, as it was glued with gorilla glue and we both knew that was asking for trouble. So he sold it and made a new one and I still had mine, which worked awesome, it was a blast, some little stuff happened barrel had to be cut, blasted a few to many end caps off and it just began to lack so I made another one, but here is the first one, as it sits now,

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And this is the new gun I built last year, but it's still unfinished as I could never get it to really fire well and said why waste time and money finishing a gun that fires like crap.

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Thats 2.5" barrel, and 4" chamber, the chamber is approx 19" long from the rear to the start of the reduction. And the spark plug is approx 10" into the chamber from the rear.

The issue, firing, it never fires consistently like my old one had, spray fuel, and click away and if you're lucky, it will randomly fire. usually requires at least 5-6 clicks before it fires, got bored yesterday and pulled it back out to try and trouble shoot, no luck, still requires tons of clicking and never consistent. Only idea I've had is to shorten the combustion chamber.

And for fuel,

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It's always worked awesome for me, back with my old gun and my friends we always used ether (starting fluid) But that gets expensive fast, and we would always end up pretty high by the time we got done shooting as you tend to inhale a lot of the exhaust vapors trying to blow the exhaust out of the chamber, so I started looking for alternative fuels and the air freshener has been awesome, was really consistent, great combustion, really launched the spuds far, one can last a VERY long time, not high after you shoot ect. And I hated hairspray for the residue it leavers in the chamber.

So, I figure you guys a little more experience than I and might be able to help.






~Thanks !
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qwerty
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Sun May 17, 2009 12:05 pm

propane gas or some other thing like butane
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jook13
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Sun May 17, 2009 1:59 pm

Well, these are neat cannons. I cant say it sounds too responsible to sell a cannon you feel was unsafe, but whatever.

A few things to help with your problems with consistancy.

1. Experiment with the amount of fuel you are using. Chances are you are flooding the chamber. Most of the time less is more.

2. Add a computer fan. A fan has tons of advantages. It will help to mix the fuel and air. It will help exhaust the spent fumes between shots. It will draw in air as you spray your fuel.

3. If you are feeling frisky, you could look into propane metering. Its not as tough as it sounds and it is the cadilac way of doing a combustion.

A good fuel to look into is called 321 dry. It is sold at walmart in the section with fingernail polish and thigs like that. Its main ingrediants are propane and butane and it leaves no residue, just a baby powder smell.
I like to play blackjack. I'm not addicted to gambling, I'm addicted to sitting in a semi-circle.
Explosive
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Sun May 17, 2009 2:19 pm

Yea, I had a feeling I was flooding it at first, but I'm not sure, I know a fan would help, my friend ended up putting one into his second gun, the only reason I didn't is that I just wanted the gun to be as simple as possible. Currently I'm doing 3, 1 second bursts of oust and gently blowing into the chamber as I seal the end cap, and it will fire, just not great. My guess was the chamber is big and the fuel isn't filling it. Just sitting in a little pocket at the rear.

Ps, I didn't sell that other gun, my friend did. He sold it to some idiots, who I've heard ended up shooting a kid with it. And then they tried to load some ridiculous ammo into it and the thing finally blew up on them. The gun seemed strong. We just knew pvc cement should have been used.
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