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How much propane to meter?

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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How much propane to meter?

Unread postAuthor: Essohbe » Sat Dec 29, 2012 5:13 pm

How do you figure out how much PSI you need to meter your cannon at?
Is there data that I haven't found or is everyone just trial and error sort of approaching it? I saw some guy on YouTube make a meter and said it's got to be 80psi (ah...).
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Unread postAuthor: CS » Sat Dec 29, 2012 6:18 pm

http://burntlatke.com/calc.html

Use the first calculator to figure out your chamber volume. Use the second calculator to figure out how much propane you need.

http://www.spudfiles.com/spud_wiki/inde ... pane_meter

This is an article about propane metering. Go down to the part about ball valve + pressure gauge.
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Unread postAuthor: Essohbe » Sat Dec 29, 2012 11:49 pm

I don't know what the PSI is in the propane bottles, I forgot. I have no way of knowing allot of the other variables either.

I'll have to just trial and error this I suppose and hope I don't blow it up.

:P
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Unread postAuthor: POLAND_SPUD » Sun Dec 30, 2012 9:50 am

here is JSRs excelent video on fuel metering with a syringe
[youtube]http://www.youtube.com/watch?v=EoVDuh3ziNg[/youtube]
Works with propane too ;)



I made an app for android devices that calculates the exact volume of fuel you have to add. Works great
[youtube]http://www.youtube.com/watch?v=q1fmRgJYlzc&feature=player_embedded[/youtube]
You can find a link to it here>
http://www.spudfiles.com/forums/fueling ... 24760.html



You can calculate them without an app of course.
1.Just measure the volume of the chamber in mililiters (you can fill it with water to take measurment)
2. Multiply by 0.0419 for propane, 0.0322 for butane
3. The result is the amount of fuel you have to add (in ml)
4. If it is a hybrid you have to multiply the result by the mix numer
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Unread postAuthor: Essohbe » Sun Dec 30, 2012 12:03 pm

Thanks for the info. Then for my 18" chamber I need 155.1557mL by the math.

My question is about metering: How do I know what PSI will release that much volume of gas in mL into the chamber? I'm metering propane with a regulator and I need to know what kind of regulator to get because some let you regulate the pressure higher than others.

Know what I mean? If I need like 80psi then getting the wrong regulator that only lets in 30psi would not be the best for my cannon.

God I hate math :p
All I want to do is launch canned goods into the air :D Why does it have to be so hard? Lol.
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Unread postAuthor: POLAND_SPUD » Sun Dec 30, 2012 12:44 pm

well if you have to add 155.1557ml then calculate what pressure you need to inject enough fuel into the chamber


155.1557ml = X * Y
where X is meter volume in ml
and Y is pressure in bar (setting of the regulator)

if your meter (so X) is 50ml then 155.1557ml \ 50ml = 3.103114 bar (which is ~45.6 psi)

It is probaly correct unless I am missing something
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Unread postAuthor: Essohbe » Sun Dec 30, 2012 10:24 pm

Man, thanks for the help. I'm retarded. Seriously.

Alright so bsically I'll just measure the volume of the meter I make then I will plug that into the equation and find my ABR. How did you convert BAR to PSI?
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