Gun not firing...

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.
Obctg
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Thu Jan 11, 2007 7:33 pm

i just built a new gun

the chamber is a 24"x4" PVC, with a stun gun wiht single electrodes in the middle and a 80mm chamber fan in the reare of the gun, at the bottom of the female cleanout adapter. i injected 4 seconds of propane witht he fan running and the gun did not fire. i then tried axe in differing amounts no more than 5 seconds worth, and alternated between fan on and off during fueling.

any help would be appreciated
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Bluetooth
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Thu Jan 11, 2007 7:37 pm

What are you putting the propane with? With my mini with a 13" 1.5" chamber I put like 4 sec of propane with a torch head in the back and close it and you cant just spray the axe on the fan.
garrettee
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Thu Jan 11, 2007 8:01 pm

I use a stun gun too. When I first tried it I had my electrodes too far apart, I'm sure you checked that. And the other thing I could suggest to check is your air fuel mixture, I know you spoke of fiddiling wih it, maybe you should try some more. Too much or too little propellant can cause misfire. That's all I personally know to to tell you. Good luck.
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benstern
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Thu Jan 11, 2007 8:20 pm

are you sure the fan is not blowing the propane out?
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Bluetooth
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Thu Jan 11, 2007 8:24 pm

Thats a very good point. Iay ouldway evernay oughtthay ofay atthay...
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frankrede
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Thu Jan 11, 2007 9:08 pm

enough with the pig latin loser.
Current project: Afghanistan deployment
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Bluetooth
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Thu Jan 11, 2007 9:24 pm

Thats wasn't nice :lol: . Ok I guess I might stop... Sometimes.
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frankrede
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Fri Jan 12, 2007 12:01 am

Lol, sorry I wa mad awhen I wrote that but pig latin is one of those things that set me off.
Current project: Afghanistan deployment
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Bluetooth
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Fri Jan 12, 2007 6:26 pm

I'm changing all the Pig Latin comments to English for you (I got other complaints).
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CpTn_lAw
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Fri Jan 12, 2007 6:39 pm

the people i see using combustion, use way too much fuel for their cannon...4 seconds is way too much. Try two sprays of 1/2 second. you will see the difference. i use a mini igniter. A good propane/butane - air mix could be ignited with a small spark. 4 % of gaz for 96 % of air. With 4 seconds of spraying, you get at least 10/12 % of gaz. usualy it works for most people cuz they have very hot sparks. But that doesn't solve the problem. It's like eating too much, and drinking a lot of Coca cola to disolve everything!! this isn't a solution, the real solution is, eat less....here, put less fuel and tell me if it did something....
Obctg
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Fri Jan 12, 2007 11:35 pm

are you taking in to account that my gun has a 301.3 cui chamber voulume
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CpTn_lAw
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Sat Jan 13, 2007 6:47 am

Yes i am, i had a 4" wide for 25" long chamber, and i was like spraying 3 seconds, the spark was there, but very purple and not intense. i sprayed two seconds, it ignited, but in a long WOOSH and continued burning inside for a second. I sprayed one second, and woaw, a loud wave of blue flame came out. 4 percent is very few compared to 5 seconds of spraying.
If there is a spark inside your chaber, the problem is only a matter of putting too much or not enough gaz. Here, trust me, you put too much.
Obctg
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Sat Jan 13, 2007 3:19 pm

what were u using as your fuel?
garrettee
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Sun Jan 14, 2007 11:55 am

I believe three days ago I said to check the air-fuel mixture. I won't do that again, sorry for bothering you.
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Pete Zaria
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Sun Jan 14, 2007 1:55 pm

@Obctg,
Try a can of starter fluid (hardware or automotive store). My cannon has a 250ci chamber and a 1/2 second spray in the middle of the chamber works fine. It doesn't take much of it at all.

Starter fluid has a good amount of power to it - it will blow apart coke bottle combustions (My friend learned that the hard way). But it's fine in PVC/ABS as far as I know. I've used it in my ABS gun a lot before I got a metered propane setup.

Peace,
Pete Zaria.
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