I need a CO2 tank for a CPM-1

[tkinva]

One of my CPM-1 CO2 tanks has died. Won't hold CO2.

Any suggestions about where to find another?

[spektr]

I have a CPM1 with 2 tanks and will bs opening up my slow leaker to fix it..... I will let you know what's involved. Are you sure the tank is leaking and its not the green o ring. Fill the tank and fill the cavity and see how bad it bubbles...... Tbese are notorious for the sealing o ring that rides on the threaded part of the pistol leaking.... Check that first......

[BEA]

I have a Walther CPM1 and it is a great AP. However, all my cylinders leak. The last time I attempted to address this issue I was unable to get any new O rings in order to do the repair myself. I was forced to send the cylinders in for a complete valve replacement at a cost of $60 each. This has been several years ago. It has just become to expensive to keep my CPM 1 going so it has been completely retired.

[tkinva]

I have a CPM1 with 2 tanks and will bs opening up my slow leaker to fix it..... I will let you know what's involved. Are you sure the tank is leaking and its not the green o ring. Fill the tank and fill the cavity and see how bad it bubbles...... Tbese are notorious for the sealing o ring that rides on the threaded part of the pistol leaking.... Check that first......

I'm going to try, as well.

I measured the opening of the tank with a caliper. About 14mm. So I ordered a 14mm Allen wrench.

The parts callout for the CPM-1 lists only one replaceable part for the tank: "O-Ring ø 14.0x3". So I ordered some o-rings this size. Amazon doesn't carry the magical green ones.

One-day delivery, so it will all be here today. Thanks, Amazon.

The adventure begins.

[spektr]

A Buna rubber Oring wont live. They are CO2 permeable and swell up when Co2 infiltrates their structure. The proper O ring is available
for 15 Pounds for ten of them. Ive got some on the way. Pm me and lets continue this

[Gwhite]

CO2 is tricky where O-rings are involved. The regular black nitrile O-rings (probably what Amazon carries) will absorb CO2 over time. If you ever drain the CO2 in the tank quickly, the gas in the O-rings will expand, and it can shred the O-rings.

The compound used for CO2 in most older air pistols is polyurethane. It's tough, abrasion resistant, but most importantly, it doesn't absorb significant amounts of CO2. It may also be hard to find in metric sizes in the USA.

Viton (FKM fluoroelastomer) is also supposed to be pretty good. McMaster Carr has them in metric sizes: https://www.mcmaster.com/o-rings/cross- ... er-rubber/

That size O-ring is going to be the main tank seal. There also has to be a valve seal, and that may be a custom part. Before you waste a lot of time, I'd fill a tank and put the business end in some water to see where the leak is. If it's from the valve, I'd check with Walther about getting new parts. Earl's is a good resource: http://carlwalther.com/

[BEA]

I am interested so please let me know when they arrive. This is good information to know. I was told by another source years ago that they o rings were not CO2 tolerant. I could not believe it to be true although I did not voice my skepticism. Please keep me posted.

[tkinva]

Update:

I was able to remove the valve assembly using the 14mm wrench. Not sure what to do next.

I have a feeling that the wrench was supposed to remove the inner part of the valve rather than the whole valve.

Note: This tank was not a slow leaker. It was a catastrophic failure. The tank was just sitting on a table and all of a sudden, it released all of its CO2. Very impressive.

[BEA]

Gwhite...good suggestion. I will do that.

[fc60]

Greetings tkinva,

Most interesting...

My older CP2 cylinders also have a 14mm hex.

How much effort was needed to remove the brass fitting?

Cheers,

David

[tkinva]

Greetings tkinva,

Most interesting...

My older CP2 cylinders also have a 14mm hex.

How much effort was needed to remove the brass fitting?

Cheers,

David

Hi David,

I clamped the allen wrench into a vise, slid the tank onto the wrench, then used a jar-opener which has a handle and rubber strap wrapped around the tank. This way, I was able to apply force to the tank without marking it up.

Unfortunately, the whole valve body came out instead of just the center section. I wonder how you tell it which part to unscrew.

[fc60]

Greetings tkinva,

The CP-2 valve can be removed with a slotted large blade screwdriver. The 14mm hex piece stays in the cylinder. I received extra valve assemblies with the pistol.

Your image suggests that it is serviced from the opposite side.

I was considering removing the 14mm hex piece and shortening the cylinder.

I was able to download the CP-2 parts diagram from Walther. It has now disappeared. Not sure if your pistol is still available for download.

CO2 seems to react with some o-ring materials. Might call a welding shop or beverage distributor to see what o-rings they use in the valves.

Cheers,

David

[tkinva]

Greetings tkinva,

The CP-2 valve can be removed with a slotted large blade screwdriver. The 14mm hex piece stays in the cylinder. I received extra valve assemblies with the pistol.

Your image suggests that it is serviced from the opposite side.

I was considering removing the 14mm hex piece and shortening the cylinder.

I was able to download the CP-2 parts diagram from Walther. It has now disappeared. Not sure if your pistol is still available for download.

CO2 seems to react with some o-ring materials. Might call a welding shop or beverage distributor to see what o-rings they use in the valves.

Cheers,

David

Hi David.

You have a CP-2. I have a CPM-1.

From your description, the C02 tanks are very different.

What works on your CP-2 tank won't work on a CPM-1 tank.

[crrmeyer]

Here is a link to the Walther CP series V2 air tank. I am not sure it is much use, but it shows the same shaped valve assy. This is from Earl's Repair Service, Inc. web ssite.

http://www.carlwalther.com/views/ev_cp_tank_v2.htm

[spektr]

That CP2 sketch is misleading, you so not remove the 14 mm boss.
Instead, you use a clutch screw driver to engage the smaller threaded valve core..... It looks like this. The screwdriver tip is a special from tacoma screw products, and costs all of 2.49 ish
The o rings are easy, but i need to unscrew the screw that has the flat O ring that seals the tank and I need a flat sided screwdriver and a bit of Kroil..... It comes apart really easily......

[spektr]

Ok disassemble the CPM1 valve assembly by holding the rectangular boss with a pair of needle nose pliers. The square machined knob unscrews with finger pressure. It slides out along with the spring. There is a flat bottomed urethane o ring McMaster Carr PN 1170N14 to replace. You might need to dig it out of the machined boss. The trick to changing it is to lube it putting it on the shaft. To compress the spring so you can get the o ring in it's groove, put the shaft and spring in the housing, put the housing on the table with a 1/4 drive socket under it to compress things. Compress the spring, stuff on the o ring into its shaft into position keeping the spring compressed... Screw rhe hex boss into place and you're almost done. Replace the o ring on the outside of the housing where it seals to the tank. The oring is mcmaster pn 1288n12. Lube it with assy lube and tighten it up.
The 14 mm o ring probably needs to be changed also, ill get the number later

Easy peasy

EDIT NOTE....... The PN was typed in incorrectly..... it IS 1170N14, NOT 1170N15 as originally posted.
Sorry

[tkinva]

Hi Spekter,

This is the info I was looking for.

Thanks.

[Bsquareng]

Looks like you solved your problem, but if you really want a new co2 cylinder (maybe to meet the 10 year rule) they are, or were, available by special order through the East Midlands Regional Range in the UK for L153.70 -- the price is at least 2 years old so ???

[spektr]

There is no 10 year rule for CO2 yanks. Rhey are in a siffeeent pressire vessel class. Thanks for the source Ill look ot over

[tkinva]

Ok disassemble the CPM1 valve assembly by holding the rectangular boss with a pair of needle nose pliers. The square machined knob unscrews with finger pressure. It slides out along with the spring. There is a flat bottomed urethane o ring McMaster Carr PN 1170n15 to replace. You might need to dig it out of the machined boss. The trick to changing it is to lube it putting it on the shaft. To compress the spring so you can get the o ring in it's groove, put the shaft and spring in the housing, put the housing on the table with a 1/4 drive socket under it to compress things. Compress the spring, stuff on the o ring into its shaft into position keeping the spring compressed... Screw rhe hex boss into place and you're almost done. Replace the o ring on the outside of the housing where it seals to the tank. The oring is mcmaster pn 1288n12. Lube it with assy lube and tighten it up.
The 14 mm o ring probably needs to be changed also, ill get the number later

Easy peasy

Hi spektr,

I finally finished repairing my two CPM-1 cylinders. It was an adventure.

I don't think that your number for the McMaster Carr PN 1170n15 is correct. It has an OD of over 6mm and won't fit, even with forcing into the opening on the hex boss. Part number 1170N14 fits beautifully on both the shaft and into the hex boss.

But that wasn't the problem. It was the overpressure relief system in the assembly at the end of the valve. There's a burst disc and a 3mm deep collar that creates a space for the disk to expand and burst. When the disc bursts, the CO2 follows a path that bypasses the O-ring.

The discs had burst on both of my defective cylinders.



I finally found some materials to replace the burst disc. I used what I had at hand. Obviously, the overpressure system will no longer work, but I can use the cylinders now. (I promise to stop overfilling the cylinders.)

I'm testing the cylinders by filling them with some CO2 and then leaving each one in a Ziploc bag overnight. If there's a leak, it will be obvious in the morning.