Vintage Double Hose

Hi guys,

I have one of each of these second stages, and was hoping someone (Greg Barlow maybe?) can give me a run down on the difference between them? Is it just the venturi tube?

Thanks,
Jim

The only difference I have noticed is the addition of the "Vortex" tube. In my experience that tube makes for a really nice performing regulator with its controlled venturi effect. The design is simple, dependable and easy to maintain, with no complicated "balanced" second stage extra parts... they just aren't needed. The MR12-III appears to be the same body as the II, but came with a composite front cover which saves a little weight. I have several of these and like them just as much as any of my newer, fancier single hose regs.

Sounds good, I am going to get them rebuilt and use them this summer. They are really good looking regs. Does anyone know if it is possible to get a replacement nameplate for the MR-12? Mine is a little scuffed up.

Jim

antique diver wrote:The only difference I have noticed is the addition of the "Vortex" tube. In my experience that tube makes for a really nice performing regulator with its controlled venturi effect. The design is simple, dependable and easy to maintain, with no complicated "balanced" second stage extra parts... they just aren't needed. The MR12-III appears to be the same body as the II, but came with a composite front cover which saves a little weight. I have several of these and like them just as much as any of my newer, fancier single hose regs.

I completely agree. Other than the VAD (Vortex Assisted Design), I am not aware of any other differences. The orifice diameter remains the same, as does the LP poppet assembly. The III did utilize silicone in the second stage diaphragm and exhaust valve.

My "modern gear" dives are handled by Mares regulators. The Proton Metal second stages offer excellent WOB, and are very simple in construction. Compared to most modern designs, they offer little that can wrong. While I still use some Mares MR12 first stages on deco/stage cylinders, I now favor the V16 and V42 first stages for backgas due to their superior hose routing.

Greg

Hi Greg,

I have heard that the MR-12's can be rebuilt with current Mares parts. Is there a breakdown somewhere that lists what parts are required for a rebuild?

Thanks,
Jim

Jimmer wrote:Hi Greg,

I have heard that the MR-12's can be rebuilt with current Mares parts. Is there a breakdown somewhere that lists what parts are required for a rebuild?

Thanks,
Jim

Jim,

Yes, the Mares MR12 III parts can be used to rebuild the first and second stages of the MR12 and MR12 II models. However, the parts are available on a limited basis.

There is some very good news, though. Bryan is a Trident dealer, and Trident produces 2nd stage reproduction purge valves and LP seats that work well. The purge valves are stock #RP34, they are called Clear 26mm Purge Valve. The LP seats are #AA88, and are called Small Regulator Seat. The Mares Abyss 2nd stage diaphragm is the correct part.

Bryan's reproduction 1st stage diaphragms for the DAAM/RAM work perfectly. You can use either an AquaLung (new, blue teflon) HP poppet, or a Mares Tri-Material version in the HP chamber. The HP balance chamber uses a standard -006, 70-80 durometer O-ring. A custom made pin will need to be created if you use the AL or Mares HP poppet. Let me know which version you are planning to use, and I will send you the dimensions. Send me your regular email address, and I will send you the factory service manual for the MR12, along with a chart that gives the standrd O-ring sizes.

Greg

Greg, I ordered the parts you listed from Trident. If you want to write up a little about both parts I'll use it for the description in the store and get them up for sale.

There is some very good news, though. Bryan is a Trident dealer, and Trident produces 2nd stage reproduction purge valves and LP seats that work well. The purge valves are stock #RP34, they are called Clear 26mm Purge Valve. The LP seats are #AA88, and are called Small Regulator Seat. The Mares Abyss 2nd stage diaphragm is the correct part

Greg, would a Titan/Conshelf service kit not work also? Based on what you posted I would assume it would with the exception of needing a new pin.

The same exhaust valve part number in 29mm will work in any later model conshelf as well, to include the XI, XII, XIV, and later. That means we can order parts out of the VDH store to repair our single hose USD regs as well. I have used that exhaust valve before, if you really want to make it seal like a waterproof bag, then put a -006 O-ring over the stem of the exhaust valve after you install it. That will keep a little rearward seating pressure on it. Mine are dry as a bone with those exhaust valves and those O-rings backing them up. Incidentally, the older USD regulators featuring a 7/8" exhaust valve work great with the 26mm valve that Greg uses in the MR-12.

Also, I concede that the MR-12III is the best regulator ever made, and I say that as a USD guy. It's the only non USD regulator that I even own.

Herman wrote:Greg, would a Titan/Conshelf service kit not work also? Based on what you posted I would assume it would with the exception of needing a new pin.

Herman,

I would assume that to be the case, except for the O-ring needed on the HP valve assembly. The Voit design uses a removable unit that is sealed in the body by a -908 O-ring. I use a 90 durometer version due to the pressure variation.

I have used the AL HP diaphragms with great satisfaction.

Greg

After getting my 1st MR-12, I've found myself wanting more. I popped on another 2nd stage on eBay and wanted to confirm that since it doesn't have a VAD (photo on the right), that this is the MR-12 and not the MR-12 II?



On another note, what's the diameter of the purge button of the later model?

Ed,

That's correct, it is an MR-12 if it doesn't have the Vortex tube. A rebuilt MR-12 second stage makes for a mighty fine octopus on a Phoenix equipped Voit Navy (just a thought). As for your other question, I'll look into my MR-12 repair manual when I get home. Hopefully there will be a purge button diameter given, if not I'll measure one.

Thanks USD! And they will be the octos on my PRAMs

pm sent

antique diver wrote:The only difference I have noticed is the addition of the "Vortex" tube. The design is simple, dependable and easy to maintain, with no complicated "balanced" second stage extra parts... they just aren't needed.

Greg Barlow wrote:I completely agree. Other than the VAD (Vortex Assisted Design), I am not aware of any other differences. The orifice diameter remains the same, as does the LP poppet assembly. The III did utilize silicone in the second stage diaphragm and exhaust valve.

Greg

Greg,

Hope you don't mind if I resurrect an old post. I've two questions on the MR-12 II vs. III, and I figure attaching to this post might help other folks who are working on MR-12s.

First, do you have any idea how much the larger, wider exhaust tee of the III decreases the WOB on exhalation compared to the II's smaller tee? I've seen posts where you list WOB numbers, and I'm guessing the Navy produced something back in the day.

Second, do you happen to know for a fact that the Trident "A145-69mm, Round black diaphragm" won't work for an MR-12? My trusty digital micrometer tells me it is more-or-less the same width as the old MR-12 II diaphragms (or thereabouts). But since you haven't suggested them as replacments, I suppose the geometry is off in some way. The lip, I'd guess. Or maybe my micrometer figure is wrong ("measure twice, buy once").

Thanks.