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Old November 14th, 2010, 13:17   #31
Delierious Designer of Dastardly Detonations
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Join Date: Dec 2001
Location: in the dark recesses of some metal chip filled machine shop
Originally Posted by ThunderCactus View Post
I think you should power your GBB pistols with oxygen instead of propane.
I actually had someone bitch me out for making a sh*tty adaptor because it wasn't threading onto a disposable oxygen bottle. Oxygen bottles have left handed threads that are otherwise similarly dimensioned to disposable propane bottles. A customer a few years ago wanted to use oxygen because the bottles are pressurized to 400psi (I think) instead of the 130psi on propane.

I was doodling around with the injector design around then and was considering how one might shoehorn enough oxygen into a propane bottle to make things dangerous and I couldn't come up with an easy way to get to a dangerous mix because the injector had such a small shot volume and air is about 80% inert gas.

The situation completely changes when it comes to a pure oxygen bottle pressurized to 400psi. Shooting 100% 400psi oxygen into a partially propane filled GBB mag can reach ideal gas mix conditions. All you need is a little liquid residue in a mag and you can reach high pressure (26atm!) ideal mix conditions.

As a bit of beer coaster estimation:

-room temp: 300k
-adiabatic flame temp of a propane oxy flame: 2800k
-plugging ideal gas law which works really well at high temps: 9.3x pressure factor

Some Gr 12 chemistry! Atoms indicated in lower case because I can't figure out subscript

-c3h8 + 5o2 ---> 3co2 + 4h2o (balanced formula for ideal combustion)
-6 moles on reactants : 7 moles for products
-assuming everything goes to vapor after combustion (pretty good assumption I think): 1.14x pressure factor

If you were working with reactants initially at atmospheric pressure you'd get a pressure of:

9.3 x 1.14 = 10.6 expansion factor = a mere 160psi

However you start off with things at 400psi (26.6atm!)

26.6atm x 10.6 = 282atm! = 4230psi!

Our crappy cast aluminum magazines are not engineered to contain a 4.2kpsi explosion...

Stay in school. All the stuff I used is high school level and it works in ideal gas situations far from condensation conditions.
Want nearly free GBB gas?

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