Spray and pray + chamber fan= Fire

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.
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sprayandplay08
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Thu Jun 12, 2008 1:48 pm

I put a chamber fan in my cannon and fired it and opened the cleanup to find a ball of flames that was my fan
TurboSuper
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Thu Jun 12, 2008 1:55 pm

Looks like some fuel got stuck to the fan and ignited.

I guess some oxygen remains in the chamber after all...

I'll bet you were using hair spray or deodorant.
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sprayandplay08
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Thu Jun 12, 2008 2:07 pm

i was using rightguard extreme deodorant[/u]
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iisthemuffin
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Thu Jun 12, 2008 2:14 pm

i thought rightguard didnt work anymore?

well i mean you are using a COMBUSTION cannon...which means there is an EXPLOSION inside of the chamber...which will of course make a FIRE...and depending on where you got the fan from there could have been oil on it...or maybe you just sprayed onto the fan...its not too hard for that to happen
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sprayandplay08
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Thu Jun 12, 2008 2:21 pm

my can of right guard extreme is over 1 yr old i never used until now
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starman
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Thu Jun 12, 2008 2:31 pm

TurboSuper wrote:Looks like some fuel got stuck to the fan and ignited.

I guess some oxygen remains in the chamber after all...
Or rushed in when the clean out was opened.
sprayandplay08 wrote:my can of right guard extreme is over 1 yr old i never used until now
Hopefully, this isn't an indication of your hygienic habits in general.... :wink:
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sprayandplay08
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Thu Jun 12, 2008 2:53 pm

I'm allergic to the brand
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psycix
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Fri Jun 13, 2008 5:07 am

Normally a fan doesnt get up in flames. There was some fuel sticked to it and surprisingly enough there was enough oxygen left in the chamber to start a small fire.

Any pics? :D
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jimmy101
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Fri Jun 13, 2008 1:44 pm

There wouldn't be enough oxygen left in the chamber to sustain a fire for more than a few milliseconds. What probably happened was you had liquid fuel (is there any ethanol or isopropanol in the rightgaurd?) one the fan and/or chamber walls. So the gun was overfueled. When fired, and at the instant the ammo exited the barrel, you had little if any oxygen left in the chamber but a small flame persisted somewhere. (EDIT: Or, you had a glowing ember.)

After the ammo left the barrel the hot combustion gases continue to expand until the chamber reached 1 ATM. The gases cooled as they expanded and continued to cool after you reached 1 ATM. The cooling gases in the gun collapsed and sucked fresh air in through the barrel. The fresh air plus the small residual flame fully ignited whatever the liquid fuel was.

If the gun is properly fueled this won't happen. Run the fan longer after fueling to get all the volatiles to vaporize. This probably means decreasing the length of time you spray in the fuel.
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