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Combustion chamber ratio

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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Combustion chamber ratio

Unread postAuthor: harrison300 » Fri Sep 14, 2007 6:37 am

Hey guys :)
i just made my second potato cannon and i went for a bigger option. this time i went with a 100mm (4") pipe as combustion with a 65mm (2.5")barrel. the combustion chamber from end to end is approx. 355mm (14") and the barrel is approx. 1m (39"). I attached my piezo bbq ignitor in the combustion chamber about 175mm (7") from the end cap the cemented the beast up. I then waited about 5 minutes and i was to eager to try this thing out so stuffed a apple down the tube, I grabbed some lynx deodorant (not the lynx dry just normal) sprayed in for about a second or two and clicked the button. nothing happened so i was pretty ticked cause my old one which had a much smaller diameter combustion chamber shoots 200m (218 yards). Anyways so i opened the combustion chamber and blow air and swung it in the air to get some oxygen back in. i then sprayed about 4 seconds worth of deodorant in. the apple came out but made a pi** weak noise and shot about 10m. Any ideas of how much i should use in this thing to make it go crazy far. :D
cheers guys harrison300
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Unread postAuthor: strangers » Fri Sep 14, 2007 6:47 am

Your using too much fuel, also for more distance get a longer barrel, about 6' long should do. Adding a chamber would help aswell to mix the fuel.
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Unread postAuthor: harrison300 » Fri Sep 14, 2007 6:50 am

too much fuel how so the first time i used like 1 seconds worth. 6" longer??? on the barrel and wat do u mean by a chamber? sorry kind of new at this
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Unread postAuthor: f.c » Fri Sep 14, 2007 6:50 am

you mean chamber fan don't you strangers.
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Unread postAuthor: Fnord » Fri Sep 14, 2007 9:56 am

I wouldn't go with a barrel much bigger than 4 feet, which would be the optimal ratio. Your gun will be quiet, but it will shoot faster.

After the glue has dried for 24 hours try fueling it with a propane torch. The burnz-o-matic brand torches will take about 20 secs to fuel up a chamber that size.(Just be careful not to trigger the igniter when you're injecting gas).
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Unread postAuthor: strangers » Fri Sep 14, 2007 8:12 pm

Yes I meant a chamber fan, and I meant too much fuel on the 4 second try most of it will liquify on the inside. I was typing realy fast before and didn't pay attention.
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Unread postAuthor: harrison300 » Fri Sep 14, 2007 8:34 pm

cheers guys aye is propane more dangourous then just the deodorant? and can any one give me an insight into this chamber fan?
thnx harrison300
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Unread postAuthor: strangers » Fri Sep 14, 2007 8:42 pm

Use the search function to find out about chamber fans and propane.
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Unread postAuthor: harrison300 » Sat Sep 15, 2007 12:42 am

link me to a good one buddy
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Unread postAuthor: turbohacker » Sat Sep 15, 2007 1:40 am

here is a good one to try...
http://www.spudfiles.com/spud_wiki/index.php?title=Main_Page

Please take some initiative and serch for yourself
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Unread postAuthor: jimmy101 » Sat Sep 15, 2007 10:25 am

harrison300 wrote:is propane more dangourous then just the deodorant?
thnx harrison300


With the roper amount of fuel they are identical. But it is a lot easier to get the proper amount of fuel with propane (or butane) than it is with any kind of a spray can.

So, a propane fueled gun will generally outperform a spray can fueled one just because it has the right amount of fuel. If you have a reasonably precise way to measure the fuel the gun will be much more consistent.

...and can any one give me an insight into this chamber fan?

Here is another good write-up on installing a chamber fan.
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