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problems with my spudgun in cold weather ...

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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problems with my spudgun in cold weather ...

Unread postAuthor: nightshot » Mon Dec 17, 2007 7:48 am

hi, i´m new in this forum....
well, my spudgun dont shot anymore... i think is cold weather ...
is this true ?

and sorry for my bad english xD ..
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Unread postAuthor: bigbob12345 » Mon Dec 17, 2007 9:22 am

It could be but give us more information about your gun so we can determine why its its not working and how cold is it
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Unread postAuthor: rna_duelers » Mon Dec 17, 2007 10:04 am

Try adding more fuel,as when air is cooler the air molecules are closer together so you might need to add some more fuel to equal the mixture out.

You might also get a lot of feed back saying don't use it because of its weakness to the cold.Just so you know PVC gets brittle when it's cold and it can crack and or shatter a lot more easily.
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Unread postAuthor: SilentJ20 » Tue Dec 18, 2007 2:07 pm

I know that my propane regulator gets all out of whack in the cold. I have to re-set the pressure back to nominal after every shot, and it leaks more due to the seals/parts not moving as well in the cold. Cheap regulator I guess.
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Unread postAuthor: Spitfire » Mon Jan 07, 2008 4:28 pm

Dont know bout not working. My combustion woks better when cold. or rainy.
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Unread postAuthor: Karatedude13 » Tue Jan 08, 2008 8:00 pm

It could just be the fuel you're using. I had lots of problems with butane in cool weather, but the same butane was unmatchable when it was warmer.
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Unread postAuthor: Novacastrian » Tue Jan 08, 2008 8:20 pm

Spitfire wrote:Dont know bout not working. My combustion woks better when cold. or rainy.


You get more air or oxygen for a given volume on cold days, that would explain why your cannon works better.

About the Butane, it has a very high evaporation temperature, so higher temps would allow for better fuel mixing.
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Unread postAuthor: Spitfire » Wed Jan 09, 2008 11:18 am

Novacastrian, true that bout the air volume. Just use deo, no problems there
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Unread postAuthor: Bubba05 » Sat Jan 12, 2008 10:48 am

I think you might have to chace down by trouble shooting mate.
I ve never had a drama with my combustions in the cold....they seem to love it.

Bubba
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Unread postAuthor: jimmy101 » Sat Jan 12, 2008 1:22 pm

Novacastrian wrote:You get more air or oxygen for a given volume on cold days, that would explain why your cannon works better.

About the Butane, it has a very high evaporation temperature, so higher temps would allow for better fuel mixing.


Lets see, call a hot day 95F (35C, 308K), call a cold day 30F (-1.1C, 272K).

The ratio of the number of gas molecules in a given volume (assuming constant pressure) is;.

n<sub>1</sub> / n<sub>2</sub> = T<sub>2</sub> / T<sub>1</sub>
308/272 = 1.13
So there is 13% more molecules in a given volume at 30F than at 95F. You need to add 13% more fuel on the cold day.

I kind of doubt that the drop in performance is because there isn't enough fuel in the chamber. Being off in the fuel stoichiometry by 13% just isn't going to make that much difference.

The most likely cause of bad performance in cold temp's is either poor mixing or the fuel source is supplying much less fuel when cold then it does when it is warm.
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Unread postAuthor: king edward » Tue Jan 15, 2008 4:47 pm

My cannon was left at my father in laws during our cold weather, I let my 70 year old mother have a go on it out the back of his house and it blew up!
luckily she was unharmed but it taught me a lesson :roll: :wink:
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