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HPA tank fill assembly

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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HPA tank fill assembly

Unread postAuthor: auxiliary » Mon Mar 28, 2011 8:30 am

I am thinking about building a small caliber high pressure semi automatic launcher and my plan is to use an HPA paintball tank as the air source. To fill the tank I want to build my own high pressure pump (separate from the gun). My hope is that this HPA tank and remote line combo:
http://www.paintball-online.com/shop/Product/Remote-Systems/Guerrilla-Air-48ci-3000-psi-HPA-Tank-and-Coiled-Remote-Combo-GPAPGR48A.aspx
will allow me to do that.

Can I remove the hose from the remote regulator and replace it with an 1/8th inch close nipple that threads directly into the gun, attach the tank to the regulator, and fill the tank through the fill nipple using the quick disconnect on the hose?

My worry is that the QD fitting is not compatible with the tank fill nipple and that the QD cannot withstand 3000psi.

Are there any paintballers out there who would know about this stuff?
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Unread postAuthor: saefroch » Mon Mar 28, 2011 8:40 am

Have you calculated how small your pump head would have to be to reach 3,000psi with your weight?

If the fill nipple is the same size thread as the QD, they'll be compatible. QDs rated to 3,000psi are available at McMaster, those at your local hardware store would probably fail at that pressure.

As far as I know, you cannot fill backwards through a regulator.
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Unread postAuthor: auxiliary » Mon Mar 28, 2011 11:51 am

The pump head will be .25 in in diameter. It will be a two way pump so it doesn't take so long.

The QD I am talking about is in the picture in the link that comes with the remote line. The slide check valve is apart of it too. I know the QD and check valve are rated to a high pressure (too at least 800psi) because they are attached after the tanks regulator, but I'm wondering if I can pump 3000psi of air through those connections. I'm thinking it might be possible because the hose itself is rated to burst at 10,000psi so I reasoned that the steel components are rated at about the same pressure.
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Last edited by auxiliary on Mon Mar 28, 2011 4:49 pm, edited 1 time in total.
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Unread postAuthor: Big-E » Mon Mar 28, 2011 12:16 pm

That would make sense; Many paintball players prefer HPA or nitrogen, especially if they play in winter. Most paintball approved setups will reg down the pressure to the level of co2, so long as your launcher can handle those pressures (around 800 psi or so) it would work fine. This assumes you leave the regulator on there. the 1/4" QD used for paintball are stainless, they are probably rated in the 2000-3000 PSI range.

I use a co2 cylinder and an air tool regulator on my pneumatic, but then again, I've never ran more than 300 PSI through it, It could handle more, I'm certain but I would use a steel chamber rather than the current copper one and get a paintball regulator before I push the pressure beyond that. Your cannon will only handle as much pressure as it's weakest component can handle.

That pump head sounds tiny, you can build good pressure with that, but it'll take a while to fill a 20 oz. tank unless you have a long stroke. since it's rated for HPA already, get a commercial PCP air pump if you can afford one. You would probably fill the bottle a lot quicker in the long run. Using a shock pump, I lost count of how many pumps it took to fill a 20 oz. bottle to 100 PSI, but it took quite a while. It has about the same size pump head you're describing.

Most regulators have unidirectional flow. Inline HPA regs on a bottle are going to have a fill port, since you need to fill the bottle to use it. So your diagram is correct, just don't mix up an inlet with an outlet. I just checked and that tank has a fill nipple, you should have no problem connecting the outlet directly with a close fit nipple, you could always use a flexible line, so long as it's rated for CO2 pressures, the paintball shop will have them.

Also make sure your pump (most specifically it's check valve) can handle those pressures; Don't want a partially charged cylinder blowing the pump handle through the ceiling now, do we? Make sure the check valve cant get stuck open accidentally too, happened to mine once and my pump handle was fully extended by nearly 300 PSI. Luckily my piston head leaks a bit so it rose slowly and I didn't end up like like BTB. I've since rebuilt my check valve, turns out the valve had a rough spot on it's guide stem that hung on an edge, I've since deburred and polished it to perfection, and no more issues.

Good luck and be careful with pressures that high :) :D
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Unread postAuthor: saefroch » Mon Mar 28, 2011 2:20 pm

With a .25" diameter pump head you should be able to comfortably reach 3,000psi, but then you'd be overlooking the issue of dead volume.

By a "two way" pump, I'm assuming you mean two-stage pump. How are you planning to handle the first stage? I'm just asking out of curiosity now...
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Unread postAuthor: turner » Mon Mar 28, 2011 3:00 pm

what pressures do you want the output and what do you want the connections to? all hpa paintball tanks fill from a nipple not connected to the output, and they use 1/8 quick disconnects. you do not need to fill through the remote line and stuff, the little fill nipple near the neck of the tank fill the tank from behind the regulator, and has a little check valve inside.
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Last edited by turner on Mon Mar 28, 2011 6:12 pm, edited 1 time in total.

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Unread postAuthor: auxiliary » Mon Mar 28, 2011 4:49 pm

saefroch: I have built a coaxial two stage pump before with copper fittings and this time around I'm going to use some thicker stronger stuff. How it works is there is a large cylinder with a narrow cylinder inside of it with a donut shaped piston for the large cylinder and a normal piston for the small one. When you pull up, the air in the large cylinder is compressed into the small cylinder. When you push down, the pre-compressed air goes into the tank. It sounds simple, but it's a pain to build, especially with the coaxial set up.

turner: The gun will run on 800psi (so the outlet pressure). I'll be using a stainless steel close nipple to attach the remote regulator to the gun. The gun will be custom machined out of a solid rod of metal (either SS or Aluminum).
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Unread postAuthor: turner » Mon Mar 28, 2011 5:50 pm

well if your going to use 800psi you wont need any regulators exept the one on the tank. Does the connection need to be flexible? you can just put an asa on the tank so that you can fit any 1/8npt male threads into.
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Unread postAuthor: saefroch » Mon Mar 28, 2011 7:34 pm

auxiliary wrote:coaxial two stage pump... ...donut shaped piston
I've considered building something of that nature before, but the machining difficulties have prevented me. How did you manage it? Can I see some pictures of the setup and/or a diagram?
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Unread postAuthor: jackssmirkingrevenge » Tue Mar 29, 2011 1:48 am

You will die of old age before pumping a 48 cubic inch tank to 3000 psi, I would seek to incorporate some sort of fridge compressor feed into your pump.
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Unread postAuthor: mark.f » Tue Mar 29, 2011 8:42 am

jackssmirkingrevenge wrote:You will die of old age before pumping a 48 cubic inch tank to 3000 psi, I would seek to incorporate some sort of fridge compressor feed into your pump.


Interesting, but I think your fridge compressor would die of old age and sieze up while you're trying to match it's flow with a .25" pump head. :P

@auxillary, if you've got the dough, I would suggest a much smaller HPA tank (like the size used on the AirForce Condor and Talon rifles) and a purpose-built three-stage PCP pump. If you were willing to either reduce your guns operating pressure or take a hit on shots/fill, you could use a smaller CO<sub>2</sub> tank at around 1100-1200 PSI.

I guess the real secret is that you definitely don't want to shoot until empty, and top off the tank between firings. :wink:
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