Quick Question (Fuels)

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.
NatoHub
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Tue Jun 10, 2008 11:52 am

I recently bought some starting fluid for my combustion cannon (basic cannon). It is highly flammable, but for some reason my cannon will not fire with it. I spray it in, put on the cap, and try to light it, but it rarely fires. I figured it would work better than hair spray (hair spray works well, but starting fluid is cleaner). What am I doing wrong? Is there a method?
:?

Quote from can: "Contains diethyl ether and petroleum hydrocarbons."
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MaxuS the 2nd
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Tue Jun 10, 2008 11:57 am

Sounds like your fuel:air ratio is way off.
You're either putting too much or too little into the chamber, experiment with it. When you spray it, is it a fine mist?
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Tue Jun 10, 2008 12:02 pm

I've tried spraying different amounts in, but somehow it's not working.
It's a pretty fine mist. I'm honestly confused, hair spray works...
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starman
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Tue Jun 10, 2008 12:02 pm

MaxuS the 2nd wrote:Sounds like your fuel:air ratio is way off.
You're either putting too much or too little into the chamber, experiment with it. When you spray it, is it a fine mist?
Yes, what max said!....probably using too much....be sure you air out your chamber between attempts.
NatoHub
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Tue Jun 10, 2008 12:04 pm

I've tried using just quick sprays, and I have been airing it out. I'll try using a small amount later. I know I'm not using too little, that's for sure.
NatoHub
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Tue Jun 10, 2008 12:13 pm

Ok, I just did a quick test.
For some reason, I spray in a small amount, put on the cap, ignite, nothing happens. But then when I take off the cap and try to ignite it, it ignites.
???
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frankrede
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Tue Jun 10, 2008 12:19 pm

That means you are spraying too much, try a 1/4 second tap of spray
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psycix
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Tue Jun 10, 2008 3:44 pm

A rule of thumb: When your cannon doesnt fire, and your spark gap works, youve got too much fuel, not too less.
Till the day I'm dieing, I'll keep them spuddies flying, 'cause I can!

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nibbler125
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Sat Jun 14, 2008 10:36 pm

i dont know why but it wont light for me nither i guess it just dosent work
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Carlman
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Sat Jun 14, 2008 11:01 pm

nibbler125 wrote:i dont know why but it wont light for me nither i guess it just dosent work
no your both just not doing it right.

other people have used it in he past to great success

i even lighted my mini with primer lol
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TheTrooper
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Sat Jun 14, 2008 11:05 pm

i even lighted my mini with primer lol
Theres always stories like that where people just finished a combustion cannon, so when they go to dry fire it the newly applied glue, is still giving off flammable fumes, ignites and usually singes their eybrows.
NatoHub
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Sun Jun 15, 2008 7:23 pm

no your both just not doing it right.

other people have used it in he past to great success
Yeah...Which is why I'm confused. I've tried everything.
Oh well, hair spray might be worse for the cannon, but at least it works.
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Carlman
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Sun Jun 15, 2008 7:56 pm

TheTrooper wrote:
i even lighted my mini with primer lol
Theres always stories like that where people just finished a combustion cannon, so when they go to dry fire it the newly applied glue, is still giving off flammable fumes, ignites and usually singes their eybrows.
yes but i purposly but primer in my chamber lol
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psycix
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Mon Jun 16, 2008 3:39 pm

Primer, the spudder's emergency fuel :D
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jimmy101
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Mon Jun 16, 2008 5:29 pm

Like frankrede said, try the shortest tap you think you can do consistently, 1/4, 1/2, ... seconds.

Blow LOTS of air through the gun between failed attempts, you need to get any "high boilers" to evaporate and exit the gun.

If you can't get it to fire with a very short spurt then move the aerosol can back from the breech of the gun a measured distance, perhaps a foot or more. It may be that the nozzle on the starter fluid can gives a much tighter spary pattern than does a hair spray nozzle. That would make sense since the starter spray is designed to get well directed into an opening that is only an inch or two across, whereas the hairspray nozzle is designed to fan out and cover a persons head.
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