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Just built first potato gun and it won't fire.

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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Just built first potato gun and it won't fire.

Unread postAuthor: Kdmann64 » Tue Oct 11, 2011 10:58 am

Ok please bear with me. I am totallynewto this. I watched a video on YouTube then went and built a potato gun. Its all PVC with with a grill igniter. I loaded it and sprayed starter fluid in, screwed on back hit igniter several times and nothing. After I took the back off I did eventually get it to catch fire inside combustion chamber. I don't knw what I'm doing please give ,e some guidance.
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Unread postAuthor: Moonbogg » Tue Oct 11, 2011 11:01 am

Probably using too much fuel. it takes only a quick spray and thats it. Try venting the chamber with fresh air and then do just a single, quick spray. People tend to think that by adding tons of fuel it will be more powerful. All that will do is starve it of oxygen and it won't fire.
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Unread postAuthor: Kdmann64 » Tue Oct 11, 2011 1:09 pm

Good call, I got it fire. It's jot firing every time though. In think my combustion chamber may be too small or my igniter sucks. But at least I can make it fire. It will be a constant work in progress.
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Unread postAuthor: jackssmirkingrevenge » Tue Oct 11, 2011 1:23 pm

here's a helpful pointer in the right direction :)

[youtube]http://www.youtube.com/watch?v=0nM603eOQU4[/youtube]

the size of your spark gap might also be an issue.
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Unread postAuthor: 03cumminsguy » Tue Oct 11, 2011 1:30 pm

Sounds like too much fuel to me as well. Think Charmin "less is more"
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Unread postAuthor: saefroch » Tue Oct 11, 2011 2:59 pm

Meter. Spray 'n' prays are inherently unreliable... hence the name.

EDIT: Fixed for most epic typo ever.
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Last edited by saefroch on Tue Oct 11, 2011 4:48 pm, edited 1 time in total.
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Unread postAuthor: jsefcik » Tue Oct 11, 2011 3:04 pm

try adding in a chamber fan to help venting, i put one in my spray and pray and helps alots, never had a miss fire!!
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Unread postAuthor: Kdmann64 » Tue Oct 11, 2011 3:34 pm

Yeah my spark sucks, it's jumping all around and not going the way it is supposed to
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Unread postAuthor: Gun Freak » Tue Oct 11, 2011 4:31 pm

Spray 'n' prays are inherently reliable

lolwut
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Unread postAuthor: mattyzip77 » Tue Oct 11, 2011 4:43 pm

try aqua net hair spray for a full 5 second blast of it into the chamber. My bet is your using way too much fuel or to little. Also the potato gotta be packed in the barrel so its air tight. good luck n let us know how you made out!! You do not need to add a fan, and your spark gap should be 1/4 of a inch to 1/2 of a inch. Are you using screws for your spark electrodes????
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Unread postAuthor: saefroch » Tue Oct 11, 2011 4:49 pm

Doesn't matter where the spark is, so long as it's there. Middle of the chamber is ideal, but the difference is relatively small.
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Unread postAuthor: Kdmann64 » Tue Oct 11, 2011 5:27 pm

Where can I get a better spark generator. Mine is really rigged up and sucks actually.
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Unread postAuthor: mattyzip77 » Tue Oct 11, 2011 5:50 pm

try a flint sparker from a camping lantern, like 4 bucks at walmart, but a grill ignitor is 100 times better and should work!!!
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Unread postAuthor: sprayandprayboy » Tue Oct 11, 2011 6:35 pm

try this
http://www.ebay.com/itm/BBQ-Continuous- ... 2c5c08b52e

i just looked up grill igniter on ebay they can make a 1/2in spark
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Unread postAuthor: jsefcik » Tue Oct 11, 2011 8:19 pm

mattyzip77 wrote:try a flint sparker from a camping lantern, like 4 bucks at walmart, but a grill ignitor is 100 times better and should work!!!



matt i beg to defer, i think the flint sparker is better, i went through lots of the bbq igniters and still love my flint sparkers
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