Dry chamber (mk17) or not (mk25)?

[evil_xander]

I have one MK25 I bought in 2005 when I started diving, had it serviced once because I wanted to, not because it needed service. Up to this day I have no problems with it, I don't dive ice (the coldest water it sees is about 8 deg C) or travel with it by plane, so I don't care too much if it's heavy or possibly problematic in ice water.

On this topic, I just got another one as it was an offer I couldn't refuse, plus I'm now in the process of assembling a twin tank setup...

 

[Jimmer]

DA, what are you opinions on what Atomic has done with the BP? I dont have any idea if they also tout the absurd 300CFM rating, but I so know several old school Scubapro addicts that wont dive anything other than Atomic now.

 

[beanojones]

I do reg repair for a shop that still has some very old 70's era Mk 5's in rental use. They have been heavily used and abused in salt water for decades and are just beginning to reach the point where I refuse to put some of them bac into service as I cannot get them to meet specs.

So yes, what you say is true...but the process takes about 40 years unless you seriously ignore and neglect the regulator.

The fact is chrome plated brass has an impressive record of performance in a salt water environment. Is titanium better - probably, but it will take about 40 years to really know for sure.

Envrionments differ. I have 'retired' a number of Mk10s, some mk15s, (and a greater number of G250/G200's), all due to corrosion. I imagine that the tropical Pacific, where gear does regularly die due to corrosion, is where Atomic made most of its early sales. Because we had all already lost gear to corrosion. I know that Apeks was a big favorite because of the environmental seal 1st stage, even though we never dive even slightly cold water. And when Aquialung added that feature to its 1st stages, after it added Apeks to its lines, they sold a ton of environmental kits. To people who dive in water that is cold if it is 75 degrees.

There is no getting away from Salt water on an island in the Pacific. The waves hit the shore and shoot salt water into the air. Everything gets coated in a layer of salt. Depsite the fact that we have no snow or ice, and thus no road salt, cars rust out here as badly as they do in the Northeast.

 

[optimator]

I have to throw in my antidotal experience on this one. I bought a MK-25 thinking I’d never go cold. Within 6 months I’m in a dry suit driving through a snow storm in Utah to go diving. 34 F water was waiting and at 60’ the probable happened and my regulator free flowed.

Next, I’m diving at Bainbridge Quarry in PA. My first dive goes fine, for my second dive I slip through several thermo clines to 90’ and 44 F water. Free Flow.

I returned to my LDS and they happily replaced my MK-25 with an MK-17. As a side note they gave my old MK-25 to a DM candidate who dove it in 48 F water and it free flowed at 30’.

Anyway – A plug for the MK-17, cause you just never know where your diving may take you, and a plug for superior service from local dive shops – they rock!

 

[halocline]

I do see a market for a smaller and lighter Balanced Piston first stage along the Mk 10 / Mk 10 Plus lines but with an updated dry sealed or christo lube filled ambient chamber. A Mk 10V would be a great compliment to a G250V and would kill off potential rivals like the still problematic and unreliable Sherwood SR1.

I like this idea, although as long as we're thinking of good projects for SP, let's go right for the return of the metal case 2nd stage, maybe with some lighter alloys. Getting back to the MK10V, would you see the old style HP o-ring-in-a-groove or a modified bushing system? I've been using true 90 duro polyurethane o-rings for the HP piston seal on my MK10 and it's working great, only about 5 PSI difference in IP between 3000-500 PSI supply pressure. With the stock SP o-ring its more like 10-15 PSI drop. The only thing I can attribute that to is a small amount of o-ring pinch under high supply pressure.

 

[pescador775]

Matt, is it convenient to order from your source or is a bulk order needed?

 

[DA Aquamaster]

I like this idea, although as long as we're thinking of good projects for SP, let's go right for the return of the metal case 2nd stage, maybe with some lighter alloys. Getting back to the MK10V, would you see the old style HP o-ring-in-a-groove or a modified bushing system? I've been using true 90 duro polyurethane o-rings for the HP piston seal on my MK10 and it's working great, only about 5 PSI difference in IP between 3000-500 PSI supply pressure. With the stock SP o-ring its more like 10-15 PSI drop. The only thing I can attribute that to is a small amount of o-ring pinch under high supply pressure.

I'd prefer to see old o-ring in a groove system. As long as the tolerances are tight enough, they work fine up to 3500-3800 psi. The current SP Mk 10 piston o-ring is much harder than the older hyperthane o-rings that came in the Mk 10 and is in fact the same as what is used in the Mk 25 piston stem o-ring.

 

[halocline]

Matt, is it convenient to order from your source or is a bulk order needed?

It's really convenient; I think you could just buy 1 o-ring, although shipping would kill you on that. It was a place called "oringsusa.com" or something like that. They have everything.

 

[pescador775]

Thanks, Matt and DA.

The follow on question concerns the AS 568 A standard sizing, like -112, etc. Can somebody throw me a bone here, sizes for MK10 and MK25 regs. I need the stem and piston (crown) sizes for each.

 

[halocline]

The HP o-ring is 010. The piston head for MK10 is 017, for the other BPs (MK5, 15, etc) its 022.