Question about possible pressure source

[just1chancefree]

Hey, I'm new to the forum and spudgunning so I hope I'm not asking an overly noobish question; however, I have searched and can't find anything about it so I want to see what you guys think. I'm looking to build a small, portable cannon to fire 2" diameter nerf pocket vortexes at around 200 fps. I need a pressure source that is very portable but not as compressed as CO2. Being an avid airsofter I'm considering using the same as what all gas airsoft guns use: i.e., un-ignited Propane. I could just use a regulator, but then I'd have to by a regulator and propane is cheaper than CO2 fills anyway. I have see discussion of using propane in combustion cannons, but why not use it un-ignited as a pressure source for pneumatic guns? (Propane Gas is 127psi @ 70 degrees, 196psi @ 100 degrees. The last page here has other useful information in determining the safety of using propane. http://www.npga.org/files/public/Facts_ ... ropane.pdf

[fullmetaljacket]

propane has been used un-ignited for pneumatic type launchers, just use it outside and away from possible sources of ignition

[An Apple Pie]

Here is one that DR made:
http://localhost/forums/viewtopic.php?t=15564

[just1chancefree]

Execlent, thanks a bunch guys. One other (hopefully) quick question: Anyone know where I can find the imputs in GGDT for propane as a "custom gas"? Thanks

[joannaardway]

Just a second, I'll check my "Book of Data" (never go anywhere without it).

Molar Mass: 44g/mol
Specfic heat capacity is listed as: .223 J/g/K - but you may need different units (I think you do, but I forget). Google may be able to convert it if you can't.
Heat capacity ratio: 1.13

Those are the ones I think you need, but here are a few more you may need:
Viscosity: 0.8 * 10^-5 Ns/m^2
Compressibility factor: .9848

[Gramanam011]

Wow, what is this "book of data" and how big is it? It seems it would be rather large to have the properties of propane.