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Noob Questions...of course

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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Unread postAuthor: mopherman » Sat Mar 08, 2008 9:32 am

Rokmonkey wrote:
LikimysCrotchus5 wrote: Just about all the parts you get a the hardware store (Home Depot, Lowes, Ace, etc..) are SCH 40.


I wish, all of it is DWV crap..

It is, but its SCH40 DWV crap. Sch 40 is just a thickness rating. If its pressure rated, it'll say so.
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Unread postAuthor: Ragnarok » Sat Mar 08, 2008 1:20 pm

bigbob12345 wrote:so no matter what, for a combustion the best C:B is 0.8:1

I have to disagree - as a basic combustion is likely to produce less pressure than a propane combustion, the barrel needs to be shorter.
Just like a higher pressure in a pneumatic can support a longer barrel, a lower pressure can only support a shorter barrel.

The ideal ratio for it may not be 1.5:1, but a 0.8:1 ratio can only be supported by a full fat combustion (i.e. metering, chamber fan, decent ignition) - a spray n' pray doesn't have the required oomph to handle that ratio.
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Unread postAuthor: bigbob12345 » Sat Mar 08, 2008 1:22 pm

Okay for a spray and pray it may be 0.9:1 or 1:1 but it is in no way 1.5:1.
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Unread postAuthor: Ragnarok » Sat Mar 08, 2008 1:25 pm

bigbob12345 wrote:Okay for a spray and pray it may be 0.9:1 or 1:1 but it is in no way 1.5:1.

1.5:1 wouldn't surprise me too much. I'd be more surprised by a ratio less than 1:1 - in fact, 1:1 would be a bit unexpected.

Spray and pray is a lot less efficent than advanced - usually under half the "power" I would say.
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Unread postAuthor: bigbob12345 » Sat Mar 08, 2008 1:30 pm

i am going to have to disagree there making a gun advanced maybey ups the power by at most 15% if you didnt add a chamber fan, if you added a chamber fan maybey 30% increase.
i know for a fact that it is under 1.2:1 because I extended the barrel on my spray and pray from 1.6:1 to 1.2:1 and it got quieter and poer increased a lot.
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Unread postAuthor: Ragnarok » Sat Mar 08, 2008 2:15 pm

bigbob12345 wrote:i know for a fact that it is under 1.2:1 because I extended the barrel on my spray and pray from 1.6:1 to 1.2:1 and it got quieter and poer increased a lot.

I think you're misinterpreting the data there.
What we do know, assuming your information is correct, is that it's higher than 1.6:1, and probably closer to 1.2:1 than it is to 1.6:1 - but that second assumption well not be true.

It's perfectly possible that it's 1.3:1. That would still mean your 1.2:1 would appear more powerful than 1.6:1, but your assumption would be wrong.

Without more data points, you can't actually make the assumptions you have.
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