High Pressure Air Help aka Homemade Pygmy tank
A couple years ago I was looking for a small carry tank that I could take with me on hunting trips just in case I had to top off my rifle. The small carbon fiber tanks were easy to find, they have them all over ebay and other places for service in paintball. I think mine is 88 cu inches? I forget, it’s around 10 inches long and maybe 5 inches in diameter and rated for 4500 psi. The trouble comes in the valve. It came with a regulated valve suitable for paintball and of course for a spare air supply I wanted it unregulated. Easy enough to do, just take the guts out of the regulator. But the valve connection above the regulator was never meant for pressures above about 2000psi and now it will see 4500psi; so not a good idea. I took off the entire valve and bought a new valve from the Sherwood company, meant for a large gas tank/high pressure air cylinder assembly like you see in welding gas and hospital breathing gas… I think the one I got is rated for 2200 psi, near as I can tell from the manufacturer’s codes; definitely not 4500psi. The casting it is machined from is much beefier than the stock valve so I have no worries about strength in the casting; but I have no idea what kind of seal material is used in the O rings inside the valve. My plan was to machine down the threaded portion of the new valve to match the tank threads and use it on the cf tank since Airhog, who sells the same type of cf tank as their “Pygmy” tank, won’t sell me just their valve. Anyone on this forum have experience with servicing or rebuidling this type of valve and can advise me if the 4500psi will blow this valve or the seals? I don’t think there is too much difference in the traffic change, I don’t know of any O rings which are sensitive to normal air. However, I don’t know if Sherwood specifies use of back up elastomeric rings behind the O rings after only a certain rated pressure, or if they use it on all their valves to be safe and prevent extrusion of the O rings, and I don’t want to take it apart to look. I can post pics when I get home.
aloha,
walt
All Replies
Viewing 13 replies - 1 through 13 (of 13 total)
Looks great Walt. I have a carbon 44 cu ft SCBA tank on the way via the Yellow Forums. Other than Brancato and Airhog, do you have a cheaper source for SCBA fittings. I need a SCBA to SCUBA fill adapter and SCBA to Foster for filling my guns.
I also have a 102 cu in carbon paintball tank I’d love to convert to one of these SCBA valves as a pygmy tank. You planning to mod anymore of these valves?
Finished machining the SCBA valves… they come with a 7/8-14 thread, and the small carbon fiber paintball tank I bought has a 5/8-18 thread. Rather than build an adapter, I just machined the neck down to the 5/8-18. Sorry, I was in a rush and didn’t take pics of the project until it was done…
walt
Here is the valve screwed into an 88 cu in CF tank. I have pumped it up to 4200psi, which is the working pressure for all my 4500 psi tanks (about 10% reduction as a safety measure… even though the hydro pressure is 7500psi and the rated burst pressure is 12000psi)
Next to a condor tank for size comparison:
Great Picudo! My thanks again. I’ll let you know when they arrive…
aloha,
walt
Walt,
I shipped 2 valves yesterday by USPS, you should have them soon.
🙂
Thanks again Picudo, that’ll work great. If they close with a soft touch then they are probably fine. If they close with a hard sudden stop that’s a sign the O rings have taken a set and probably will leak or need to be serviced. No need to send all of them, you’ll probably need some for yourself someday.
aloha,
walt
I bought a 4 valve set of a guy in ebay for about $60, he didn’t want to sell the valves individually. So I’ll send you a couple of valves next week to see if you can get them working (the better looking ones). You can keep one for your own use.
Perhaps it would be better if I send you the 4 of them. Maybe somebody else wants another tank. I really don’t know in what condition those valves are in, maybe you’ll need to cannibalize one or two of them to get the others working.
In the mean time, I’ll look for a CF tank.
Thanks Walt!!
Nothing wrong with that.
Except, it’s aluminum, much heavier than CF. And, it’s 3000psi so if your modded gun runs best at 3200psi, you cannot get a good fill or topoff.
what is wrong with something like this
http://www.leisurepro.com/prod/AQUTP.html?srccode=cii_9324560&cpncode=23-47251686-2
you could buy this cheaper than you could make it
Well, since I’ll be rethreading the valves (yours and mine), see if you can find a cheap small carbon fiber tank as well, that way you may as well have a cf carry along for yourself too! I see plenty of them on ebay for under a hundred, for the paintball stuff. Or, wait until I do mine first and if it works out well, then go get one and we can duplicate it. The only problem comes in filling; I have my own compressor, so I’ve got no problems with the stuff I make; but if you are taking yours somewhere to get it filled, they may balk. if you have a footpump, no problem.
walt
No problem Walt!!
Hey I bought it used, so don’t expect to get a shiny new valve in the mail!! I’ll send it to you next week. Hope it will serve you well 😀
Thanks, Picudo. Someone else pointed out that same thread to me too. I don’t think there’s anything illegal about it when you are making one for yourself; only when selling it. I agree, one should not go about modifying HPA equipment and then selling them, there is a safety margin built into them and it’s there for a reason.
You are too generous with your valve! Let me know how much you want for it. I have to go dig up my sherwood valve, which was brand new when I bought it. Don’t know if it’ll work or not.
aloha
walt
Walt:
There is a guy that is doing just what you’re thinking
As you can see from the thread, there are some people that think that modifying a high presure valve (SCBA) is ilegal. So the guy that wanted to sell the valves is researching this possibility.
Anyway, I bought a USED SCBA valve on ebay, if you want, PM me and I’ll send it to you. It’s not in great condition, but I think you may be able to get it working.
Viewing 13 replies - 1 through 13 (of 13 total)
- You must be logged in to reply to this topic.
Welcome to the forum, glad you found your way here.
Sorry, no plans to mod any more of these valves. You can ask Picudo to sell you one, though, if you’d like to take on the project yourself.
aloha,
walt