Argon cylinder / no valve / 1st stage

[-JD-]

JD, this looks great indeed!
The 1/8"NPT is slighty smaller then the HP port's UNF7/16. But there is not enough difference to put an adaptor in between. So I guess I will reproduce the fitting's body: outside thread UNF7/16, inside the check valve. The Foster fitting (I think this is the coupling) I will leave away and make an even shorter filling adapter.
The great advantage of this check valve is the fact that it is located inside the thread which makes the whole thing much shorter and also smaller in diameter.
I hope I can get this Foster fitting in Switzerland or at least in Europe.

Unfortunately, I have only found those style fittings in 1/8" NPT, 1/8" BSP(P), M10x1, & M8x1. No 7/16-20UNF.
This Chinese supplier has all 4 sizes for < US$4 each delivered to US addresses: US $1.89 5% OFF|New Paintball Air Gun Airsoft PCP Air Rifle 8MM Quick Plug Connector Check Valve One Way Foster Stainless Steel Fill Nipple|fill nipple|pcp paintballpaintball fill nipple - AliExpress

 

[Agro]

JD, great, thanks a lot. I ordered some of those and will rebuild the housing. I'll post the output here.

 

[happy-diver]

Magnificent!

 

[Agro]

I rebuilt the non return valve, using the paintball parts, works great and is smaller, thanks for the information.

The M5 screw incl. sealing ring prevents the water from entering the valve which would be no good if we refill the cylinder. And if non return valve should fail the M5 screw also prevents of air loss.

The filling adapter (DIN) seals the same way as the M5 screw.

The inner parts are out of the paint ball filling adapter. There is a M7x0.5 thread which is quite unusual.

 

[-JD-]

Nice.

What did the seat on the interior/female side of the original paintball non-return valve look like? Did you need to replicate it in your fitting?

Would counterboring and using o-rings (LP/HP port style) on the M5 screw and fill adapter give you a more reliable captive seal vs the face-sealing compression washer?

It looks like you are using a "rubber" washer and a metal washer with the screw, doesn't that leave a gas leak path along the screw shaft and out the metal-metal junction? (I could easily be mis-reading your pictures, though.)

 

[Agro]

Yes I did replicate the interior/female part, see pdf. Cylinder 6.5x13mm, part of it M7x0.5

I am using a USIT ring. No idea about the english name, sorry Usit-Ring, NBR, 70° Shore A, US kaufen - im Haberkorn Online-Shop

Perfect sealing and very flat, 1mm only. An o ring groove is larger. I realy wanted to make everything as small as possibel.

The metal-metal junction on the screw is no junction (male thread and head are made out of one part), so no sealing problem.
The metal-metal junction on the filling adapter does have a gap between male and female thread. But this gap is inside the sealing area so it does not have to be closed. The adapter's body is sealing vs. the non-return-valve's body, that's the point. No matter if body has a gap towards the thread.
But anyway the screw which goes into the filling adapter is fixed by Loctite, so it is sealed as well, even if this is not necessary. It is necessary to be fixed, not to be sealed.

 

[-JD-]

Ok, I see that the USIT ring seals against both surfaces. It had not seen one before. Handy.

So the PCP non-returns just seal on a flat shoulder, not a knife-edge. Good to know If I ever do something similar, finding a M7x0.5 tap might be extra fun over here in imperial world, though.

Thanks for the clarifications.

 

[Agro]

BAER HSSG Einschnittgewindebohrer Form D - MF 7 x 0,5 Cheap

 

[-JD-]

Surprisingly, Amazon will sell me a tap and die, delivered tomorrow for $12.50 (https://www.amazon.com/0-5mm-Metric-Thread-Right-Hand/dp/B07L6851X1)
Must not actually be all that uncommon. Good to know if I go that route. I actually have some ideas where this might work well for me.

 

[Agro]

I tell you about my experiences. Filling was fine about 10 times but suddenly airflow was reduced, looked like a restriction. I found it. When filling the 2 brass parts are pressed together (spring gets pressed) this makes a nearly perfect sealing brass-to-brass. I solved it by a t-drilling into the brass part (the one having the sealing on it). Now it works fine again.
No idea why filling worked fine for several weeks and all of a sudden it was blocked.
Apart from that it workes fine, I am happy.