N/A Umarex 2x Co2 adapter: Seal issues, questions, solutions?

[proto57]

I have the Umarex 2 Co2 cartridge adapter, which is used to replace the single 88 gram Co2 tank in various air guns. It fits many makes and models, but I use mine on my .22 Umarex 850.

My issue is that, after piercing the Co2 carts, the seal around the piercing shaft leaks. I can back off the screw of the shaft a bit, and the leak then stops. It is suppose to seal when all the way in, though.

So of course I wanted to replace the seal, but could not find one online anywhere. I even called Umarex USA, and the screener put me on hold to ask my question of one of their "gunsmiths". He came back to say that they do not offer kits to rebuild these adapters, and only get the entire adapter from a suppler "overseas". They are made in Taiwan. I suggested that many people around the internet have or have developed leaks, and maybe they could take one apart, measure the seals, and offer a seal kit of their own. But, basically, I was out of luck.

So today I took the cap of the adapter apart, and among other things, thought that might be of interest to others. They way you disassemble it is to 1) first tap out the hinge pin in the screw toggle handle. Be careful to not lose the the little coil spring on the shaft. 2) Then you can unscrew the shaft from the piercer side, using the slot machined into the shaft next to the piercing point. 3) To remove the seal, you can insert a stiff needle... I used the point of a stainless steel safety pin. You push the point into the rim of the seal, pry it into the hole, and then you can pluck it out. Here are the parts:

As you can see, the seal is not a simple O-ring, but a stiff transparent plastic, shaped with a lip:

And here are the rough dimensions of this seal. They are not exact... this is very small, and flexible, making it difficult to measure exactly:

Not wanting to put that seal back in, as I know it does not work, I tried a small O-ring from an airgun rebuild kit. That O-ring is 8.45mm in diameter, with a ring thickness of 1.5mm. To my surprise, it works perfectly! Well, at least for now. Whether or not it will hold the Co2 for long term or not, or breakdown or wear prematurely, I don't know yet. So I was wondering if anyone recognizes the original seal I took out. I would imagine it is used for other Co2 sealing assemblies, because I doubt they tooled up for just this one adapter. I think that if the type and source of this is known, it will help many people with these adapters... and I will pass the information on to the staff at Umarex, too.

 

[marflow 777]

the seal is made of urethane and the Oring you used should have been also
i was looking for rebuild kits for these about a year ago and none showed up but i didn't need at the time, so it just got filed
a parts diagram should be offered and parts also offered by someone
knowing Umarex they will say send it in we will fix it and with that never sell you any parts because either they are greedy or believe we are that stupid

so, while you are at it see if you can get a parts diagram
i have saved this thread
mike

 

[proto57]

the seal is made of urethane and the Oring you used should have been also
i was looking for rebuild kits for these about a year ago and none showed up but i didn't need at the time, so it just got filed
a parts diagram should be offered and parts also offered by someone
knowing Umarex they will say send it in we will fix it and with that never sell you any parts because either they are greedy or believe we are that stupid

so, while you are at it see if you can get a parts diagram
i have saved this thread
mike

Good point... I'll call or write them and ask for a parts diagram.

Meanwhile hopefully someone recognizes the original seal... I did a giant search for urethane airgun seals, and scrolled through hundreds. None even have the "step" design in this adapter. But I searched for "with step" urethane seals, and there were some... but all offered to spec by manufacturers of seals. I'm guessing that is the case here... this seal was custom made for the makers of these adapters, and do not appear in any other gun nor accessory. Hope I'm wrong.

And by the way, since putting this together with the O-ring I had laying around, it seems not to have leaked. Or, not enough to drain the adapter. I'll let it sit a few days and see what happens. Wouldn't it be crazy if all one has to do is put in a regular old... proper material, of course... O-ring?

 

[marflow 777]

your thinking is right this seal was cast for this product and has no other cross over use
now we have been in this hobby long enough to know that a substitute can be found for many things
like a Oring instead of the wedge shaped seal in the IZH 46m breech
i have been using an Oring for the flat seal in the valve of the Diana Chaser
why they make a one-off use seal when they could have changed the hard surface is hard to believe
now your Oring works and that will be a cheap fix when someone else needs to fix these adapters and i would think that the factory replacement will be in the 5 to 10 buck range if it is available at all

so what have you done
you have proven or R&D a solution to a problem
now looking at The Oring Store an 8.45mm doesn't exist but an 8.5mm x 1.5 does but only in Buna
so, going back to inch in urethane a 009 would be a little over size in both CS and OD but are available in Urethane dura 70 at the Oring store
and for readers this is a very small Oring

an interesting thread

 

[proto57]

your thinking is right this seal was cast for this product and has no other cross over use
now we have been in this hobby long enough to know that a substitute can be found for many things
like a Oring instead of the wedge shaped seal in the IZH 46m breech
i have been using an Oring for the flat seal in the valve of the Diana Chaser
why they make a one-off use seal when they could have changed the hard surface is hard to believe
now your Oring works and that will be a cheap fix when someone else needs to fix these adapters and i would think that the factory replacement will be in the 5 to 10 buck range if it is available at all

so what have you done
you have proven or R&D a solution to a problem
now looking at The Oring Store an 8.45mm doesn't exist but an 8.5mm x 1.5 does but only in Buna
so, going back to inch in urethane a 009 would be a little over size in both CS and OD but are available in Urethane dura 70 at the Oring store
and for readers this is a very small Oring

an interesting thread

Thanks much, all good points. Interesting stuff. It would be great if all designers always considered these things, but what are you going to do? Adapt.

Hopefully this will be helpful to others. Yes probably an 8.5mm x 1.5 then... and what you said before, the one I probably put in was the wrong material, and may not last. I will look at your suggestions to replace it, so I will have them ready when the time comes.

 

[marflow 777]

there used to be a The 850 forum it was all about the Hammerli 850 which i have 2
they made me a believer that any Oring that is touch by CO2 should be urethane, buna will absorb CO2 and swell and fail over time but urethane will not absorb CO2 but i am a realist and understand that it is not a perfect world
the damn fact is a new Oring could last 10 years or more but the price of getting just 1 or 2 makes them very expensive
this hobby is not cheap i have the bags of Orings and stuff to prove that

 

[proto57]

Through some trial and error, I was able to finally figure out which size O-rings would work to seal the Umarex 2x CO2 adapter. I bought these from the O-Ring store... they are very nice, knowlegeable and helpful. But, unfortunately, the only polyurethane O-ring they had of the three was the one used to seal the piercing rod in the cap. The others need to be 2mm, and the largest CE for those that they had is 1.78 mm.

But it is really good the 8mm piercing rod seal is urethane, though, because that one is very critical, and has the moving piercing shaft rubbing on it. It NEEDS to be polyurethane. When experimenting and checking the size, I originally used a plain old nitrile one in there... yes, it seals the first time, but swells and degrades (of course). But when I put the urethane version in, it has worked fine and held up under about a half dozen changes of cartridges. It does not leak.

The seal in the cap is Buna-N, and does swell. But it seals until the next cart change, and then I just replace it from the stock I bought. And the old seal will shrink, and will work fine again after a day or so. Not ideal, and I do put new ones in each time, but that will work.

I found that I had a small leak in the part of the adapter you normally never open: The screwed in end by "gun end" of the adapter. It is practically invisible, as it is a close fit. I did wrap electrical tape around the smooth portion, and used a vice grip on it to remove. But I didn't have enough tape, and did get small scratches. I'm sure it will be fine, but try to avoid this if you can. There is like 600 pounds in this thing, and one would not want any score marks on it. And BTW, I would rather have urethane in that location, too... but it has stayed sealed for weeks, so I suppose that since it is not opened and removed, any swelling will not matter. Of course it could degrade over time, so I keep my spares handy.

Here are the numbers, dimensions and materials:

Cap seal:

2mm x 19mm (NBR)
Buna-N 70 Duro Metric O-Ring (N2.00X019)

Model: N2.00X019
2mm CS X 19mm ID
0.078" CS X 0.7481" ID

Cylinder End Seal:

2mm x 20.5mm (NBR)
Buna-N 70 Duro Metric O-Ring (N2.00X020.5)

Model: N2.00X020.5
2mm CS X 20.5mm ID
0.078" CS X 0.8071" ID

Piercing Rod Seal:

Model: U90008
Dimensions: 3/16"ID X 5/16"OD X 1/16"CS
Actual: 0.176"ID X 0.070"CS
Metric: 4.47mm ID X 1.78mm CS

And here is a picture labeled to show the places these go:

Luckily I don't have a valve seal leak. I am not sure of the seal that is used in there... a disk? The valve is easily removable, as the front piercer is slotted for a screwdriver. I just didn't want to mess with it, because it was working.

For putting in the 8mm poly seal in the cap, for the piercing rod, you need to drift out the rod on the black plastic screw handle. There is a little spring under there, note how it goes. It is a pain. I didn't feel I need it, so I just left the spring off. After the handle is off, you can unscrew the piercing rod from the inside with a screwdriver. Now you can fish out the factory poly seal using the point of a safety pin, or the like. I bent the last 1/6" of the safety pin point with a pliers.

To put the new O-ring in the groove in the cap's hole, it helps to screw the piercing rod in backwards, from the top. Screw it in far enough to give you a little "shelf" to push the O-ring against... this helps you fanagle it in there, without pushing it past the slot.

By the way, all the original seals are shaped, with different profiles. I guess they thought this would be more effective? But they all seem very inadequate. And also, I wonder if this was designed and machined FOR plain old O-rings, with a circular CE diameter, to begin with... I mean, they work fine, so?

Anyway, long story short, these sizes and materials work fine to sealing this adapter, and solving the problems that many have with them. If I or anyone comes across urethane version of the cap and end seals, though, we should post here.

 

[marflow 777]

the chasing of Orings is something that most of have to do at some point and some are easy to find, end of story
but as you have found out you can spend hours looking and looking again
your size info is very helpful for the next guy but the inability to buy what you want-need is so frustrating
thank you for your time a effort

 

[marflow 777]

so i just read this and it may help in the future
For o-rings used with CO2, **polyurethane and fluoroelastomers (like Viton) are good choices due to their high resistance to CO2 and good sealing properties. Nitrile (Buna-N) can also be used, but it's important to consider the specific application and temperature range.

now the Oring store has those min 75/80 dura in both 19 and 20.5mm ID