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Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Unread postAuthor: rp181 » Sat Nov 29, 2008 4:37 pm

Of course school's will hate it. Not only does it open up liabilities on there part, but its illegal on your part.
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Unread postAuthor: D_Hall » Sat Nov 29, 2008 5:05 pm

rp181 wrote:
No, there isn't. And only a damned fool would try.


McMaster, catalog page 471. Flow control, up to 2000psi.

Yeah, technically true, but I think we both know he meant pressure control.
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Unread postAuthor: D_Hall » Sat Nov 29, 2008 5:08 pm

One thing you have NOT mentioned.... Why do you need 300 psi? What EXACTLY are you trying to do? There are very few things that 300 psi can do that 150 psi can't also do with a bit larger tank and a longer barrel.

IOW, it sounds like your 300 psi argument is arbitrary and causing you all sorts of grief for - I suspect - no good reason.
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Unread postAuthor: MrCrowley » Sat Nov 29, 2008 5:13 pm

If he's making a small bore sniper, 300psi is a reasonable ask for decent power. Maybe maintaining a small chamber, barrel and valve while upping the pressure to the couple of hundreds is more practical for him compared to upping the chamber, barrel and valve.
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Unread postAuthor: Ragnarok » Sat Nov 29, 2008 5:38 pm

D_Hall wrote:Hint: CO2 is roughly twice as dense as water.

That doesn't sound right to me. I'm not arguing your point about hiw anti-siphon tubes work, but I was almost certain that CO2's density in it's liquid phase was anywhere from ~0.6 g/cc at 30 degrees C, down to ~1.15g/cc at -50 degrees C (it's ALL over the place with temperature)

It's about ~1.55 g/cc in it's solid form, I know that fairly well.
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Unread postAuthor: D_Hall » Sat Nov 29, 2008 7:17 pm

Hmmm... going off old memories....

A quick google indicates that you're correct.

Which is making me question my memory. What's odd is that I *KNOW* that the anti-siphon tubes in my collection are straight tubes. I know that because I personally fabricated and installed them. I also know that they deliver gas no matter what position the tank is held in as I did some pretty extensive testing on that front.

I've also seen the anti-siphon tubes installed in bulk tanks. Again, they're straight tubes about half the length of the bottle.

Hmmm.....


edit: OK, I'm seeing a SG of 1.18 at 1 atm and boiling. Haven't had much luck in finding desity at 58 bar / 850 psi. There is this link though...
http://www.warpig.com/paintball/technic ... mics.shtml (notice discussion halfway down the page)
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Unread postAuthor: Ragnarok » Sat Nov 29, 2008 7:58 pm

D_Hall wrote:I *KNOW* that the anti-siphon tubes in my collection are straight tubes. I also know that they deliver gas no matter what position the tank is held in as I did some pretty extensive testing on that front.

I wasn't questioning the part that tanks are less than half full - well, MOST tanks at least - I also have some ex CO2 fire extinguishers, when those were in use, they got a much higher fill, because they needed to be space efficent - and also because they WANTED to be getting liquid CO2 out.

Note to those that don't know: The point of a CO2 extinguisher is not to suffocate the fire with CO2 - no, the point is to get everything very cold, so there's not enough heat to sustain combustion. Indeed, usually dry ice crystals can form in use.

Oh, while I'm on the subject, if you ever have to use one, do NOT:
- touch the nozzle or the bottom of the extinguisher, because you WILL freeze your hand to it and have to have it surgically removed.
- direct the jet at anyone, because it can cause frostbite or even a form of "the bends."
- Use it on liquid fires, because you will spread flaming {insert liquid on fire here} across the room.
- expect it to be quiet. It's not.


Haven't had much luck in finding desity at 58 bar / 850 psi.

Yeah, I have no idea about that. It probably increases somewhat given the way it reacts to temperature, but twice the density of water sounded on the high side. It may be right though, but I recalled seeing something in a data book that listed CO2's density in liquid form - at least at 1 atm - at around the same as water, depending on temperature.
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Unread postAuthor: D_Hall » Sun Nov 30, 2008 12:30 am

Ragnarok wrote:Note to those that don't know: The point of a CO2 extinguisher is not to suffocate the fire with CO2 - no, the point is to get everything very cold, so there's not enough heat to sustain combustion. Indeed, usually dry ice crystals can form in use.

Oh, while I'm on the subject, if you ever have to use one, do NOT:
- touch the nozzle or the bottom of the extinguisher, because you WILL freeze your hand to it and have to have it surgically removed.
- direct the jet at anyone, because it can cause frostbite or even a form of "the bends."
- Use it on liquid fires, because you will spread flaming {insert liquid on fire here} across the room.
- expect it to be quiet. It's not.

There was a time in my life (read: military days) in which I was a firefighter by profession. Of course, that was 20 years ago (Gawd, am I really that old??) but....

...let's just say that CO2 extinguishers are great for cooling down beer.
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Unread postAuthor: THUNDERLORD » Sun Nov 30, 2008 1:01 am

... A *FULL* CO2 tank is less than half full of liquid CO2...


Maybe off-topic a bit but this one made me wonder, If a 12 or 8 gram CO2 cartridge is only half fluid as well?

Because If so maybe they could be contained in another vessel half the size?!! :)
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Unread postAuthor: frankrede » Sun Nov 30, 2008 1:11 am

Enough is enough, come one guys enough spoon feeding this fool.
Sounds like a troll to me.
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Unread postAuthor: Ragnarok » Sun Nov 30, 2008 1:13 am

THUNDERLORD wrote:Maybe off-topic a bit but this one made me wonder, If a 12 or 8 gram CO2 cartridge is only half fluid as well?

I believe that CO2 bulbs have a greater percentage fill.

And as has been said, the density of CO2 changes dramatically with temperature, so the liquid volume expands and contracts - there has to be some volume for that to expand into if the temperature goes up, otherwise it would be highly dangerous to have them around.

No point in making them half the size if they then explode into shards the moment the temperature goes over 80 or 90 degrees F.

@D_Hall: Best uses I've found are freezing gum out of clothes, and solidifying the remains of a rotten mattress that had welded themselves to the floor so that it could be smashed off with a sledgehammer.

We had a lot of spare black CO2 extinguishers in stage crew after health and safety decided that the black variety was unsafe, so they all had to be red instead. The black ones no longer counted towards requirements, so they got used up in training newbies in fire safety, or odd stunts like that.
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Unread postAuthor: john bunsenburner » Sun Nov 30, 2008 3:06 am

I am not quite sure ho any of the above helps me at all..All i was asking was if you guys from expierience know the following: If using bulk tanks with regulators as power sources sums up after time making it far better to just buy a strong compressor. That was all i needed to know. And i want 300psi because i want a gun with a barell of 1meter that has some decent power and because the easyest and fastest valve i decided to make as a begginner was a hammer valve. So just please answer my question, then you can do what ever you like so again for reference:

Will using bulk tanks with regulators as a power source for a sniper rifel sum up over time making it more economical to invest in a compressor(internet/ebay) or will the minimal price of bulk tanks(30l, 30$, 3kpsi) be so low that it will not sum up, either because of an infrequent need of new ones(they last long) or because bulk tanks are so cheep it would take a long time for the price to some up?

@rp181: I was really just joking there!

@frankrede: How am i being spoon fed if people are mostly talking about old memories and the physical propoties of CO2?

I hope some one will answer this yes or no question for me, i am just not as experienced and i am hoping to learn from others that have more experience than me. Sorry if i did this in a manner people do not like for what ever reason.
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Unread postAuthor: MrCrowley » Sun Nov 30, 2008 3:11 am

John, I've aleady told you several times:

If a bulk nitrogen tank is only $30 for 30L, THEN GO WITH IT. Compared to the ridiculous cost and low pressure of a compressor, there is no other option that seems worthwhile.

We've already answered your question.
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Unread postAuthor: john bunsenburner » Sun Nov 30, 2008 3:37 am

Ok thank you, ill go get one in the coming week(s) depends when i get rid of the horrible cold i have...
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