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Posted: Tue Oct 09, 2007 2:05 pm
by Brian the brain
and CO2 turns liquid at between 50 and 60 bar...not 5!!!
Posted: Tue Oct 09, 2007 3:08 pm
by Pete Zaria
As mentioned already, your twist rate on the barrel's rifling is far too tight - in fact, rifling that tight could cause a dangerous barrel blockage situation. Rifling more like 1 full twist in 10" will provide much better velocity and still yield good accuracy.
My question is, if you're designing a high-pressure, rifled barrel pneumatic, why not use a barrel from a "real" black powder gun, such as a .44 cal muzzle loader barrel? You could probably find one inexpensively on an auction site or gun show, and modify that to use with your pneumatic setup.
The "reducer valve" you mentioned to knock down the pressure of your HPA tanks down to a more reasonable pressure is called a regulator, not a reducer valve, and you're going to need a pretty hefty regulator for this project.
What kind of (main) valve are you going to use? For pressures this high a metal piston valve seems like the obvious choice.
Good luck.
Peace,
Pete Zaria.
Posted: Tue Oct 09, 2007 5:00 pm
by jackssmirkingrevenge
Brian the brain wrote:and CO2 turns liquid at between 50 and 60 bar...not 5!!!
According to
wikipedia:
Liquid carbon dioxide forms only at pressures above 5.1 atm
Posted: Wed Oct 10, 2007 12:25 am
by clide
Jack, that just means the pressure where it can turn to liquid at all, and that would be at a very low temperature (−56.6°C) for CO2 to be liquid at 5 bar. At room temperature it liquefies at over 50 bar.
Posted: Wed Oct 10, 2007 1:12 am
by jackssmirkingrevenge
Ah, you meant room temperature
Posted: Wed Oct 10, 2007 8:10 am
by Necrosis
Yay, the valve stress tested at 200 bars.
Well virtually anyway.
*edit* and a cross section render
Posted: Thu Oct 11, 2007 11:02 am
by Necrosis
Hmm, I've been wondering... What would be the best way to trigger the valve? I was thinking about using a strong magnet and an electro magnet..and a capacitor, But I do not know if this will work.
Does anyone know?
*edit* and a spring to push it back of course
Posted: Thu Oct 11, 2007 2:16 pm
by jackssmirkingrevenge
Necrosis wrote:I was thinking about using a strong magnet and an electro magnet..and a capacitor, But I do not know if this will work.
Does anyone know?
*edit* and a spring to push it back of course
have a read through
here 
Posted: Thu Oct 11, 2007 3:06 pm
by Necrosis
That's indeed where I got this idea from.
Not from that particular document, but from the stuff people at my favorite airgun forum have been telling me.
Posted: Mon Oct 15, 2007 8:14 am
by Necrosis
Bumpedy bump, Exactly how would I get the air into the chamber? with a schrader valve?
And if so, does anyone have the dimensions to such an apparatus?
*edit* New piston valve assembly thingy! whoo!