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propane amount question

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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propane amount question

Unread postAuthor: isban » Wed Jan 31, 2007 4:44 pm

Hey all this is my first post here. I have a propane gun and I was wondering if there an optimum psi or ratio that the propane should be at in the chamber that gives the best performance.
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Unread postAuthor: Recruit » Wed Jan 31, 2007 4:53 pm

Yes there is a formula I dont remeber it off the top of my head. But it has to do with camber volumn.
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Unread postAuthor: MrCrowley » Wed Jan 31, 2007 4:55 pm

Propane=your meter should be 4.2% of your chamber volume
MAPP= " " " " 4.6% " " " "

I think thats it. :roll:
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Unread postAuthor: StealthSpud » Wed Jan 31, 2007 5:27 pm

Yeah Mr.Crowley I think that sounds right...mabye..
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Unread postAuthor: willarddaniels » Wed Jan 31, 2007 5:53 pm

Propane burns between 2.4% and 9.2% fuel to air mixture. Optimal is 4.02%
One way to figure it out is fill your combustion chamber (and lead tube up to where your projectilesits) with water, measure the volume of water and multiply by .04 This will give you the volume of propane you should use.
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Unread postAuthor: Pete Zaria » Wed Jan 31, 2007 5:56 pm

You guys got the ratios right: 4.0-4.2% propane, or 4.6% MAPP gas.

If you're using a meter system, this spreadsheet (called ProMeterEs) will show you what pressure to use to get a 4.2 or 4.6% mixture: http://www.spudfiles.com/forums/download.php?id=3213& .

All the math is done in volume, not length of pipe or anything. If you need to calculate the volume of your combustion chamber or meter pipe: http://www.online-calculators.co.uk/vol ... volume.php

For example, I have a 250ci (4" x 20") combustion chamber and a 7" x 3/8" meter pipe. I use two "shots" of propane at 65 psig each.

Peace,
Pete Zaria.
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Unread postAuthor: isban » Wed Jan 31, 2007 9:04 pm

wow thanks pete those links are really helpful
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