Post by rhwestfall on Jul 31, 2014 10:31:54 GMT -8
Healthways Scubair "B" labeled second stage... I know the "B" designation was for "balanced", but perhaps it was accomplished in the first stage it was packaged with.... as I said, I have not gotten into it much as I want to resolve my MR-12II issue first.
I have two different MR-12 second stage bodies from the AMF Swimaster era. One has the external "venturi tube", and one does not. I have enough parts to assemble one (wish i hade enough to do both and use one as an octo, but such is life). Which body would you use, and why? Thanks in advance for any input.
The AMF swimaster MR12-II single-hose, demand scuba regulator was tested by the Navy Experimental Diving Unit in accordance with MIL-R-24169A. The tests showed that the MR12-II is an easily operated breathing apparatus requiring low work rates. The MR12-II regulator is recommended for placement on the list of equipment authorized for Navy use. (Author)
My only reservation would be if you are doing ice diving, then be aware of my experience with it freezing into a free-flow at around 39 degrees F in a freshwater lake.
The image shows the retainer with the old o-ring: it only took about ten minutes to rassle th' ol' one out an' get th' new one in. I used an old nut-pick that I bent the end of. You don't want anything too sharp or small, 'cause ya gotta pull that sucker out without scratching things up. The trick is to push one end of the o-ring down deep inside, then, pull up on the opposite end, by hooking it from the bottom, not the top. Getting the new o-ring in is easier if you don't use silicone, use... spit! it's just slick enough, but not overly, you can rinse it off easily enough!
I’ll chime in on this topic, as I have been restoring/diving with Voit single hose regs for several years.
First, your reg is not a “hybrid” of any sort. You actually have a very early example of the original MR-12, which was produced in late 1968. There are no known existing records of production dates and corresponding serial numbers, but with your serial number being so low it indicates that it was among the initial factory run.
Let’s begin with the first stage. The yoke was designed for a maximum cylinder pressure of 2,400psi. I suggest not using it on cylinders containing more than 2,500psi or so for safety’s sake. The original spring base plate was made from plated brass. Voit changed this to a plastic version during 1969, and kept it the same throughout the remaining years. The poppet pin was 0.475” in length, allowing it to function normally with the poppet and poppet retainer assembly (balancing chamber) combination. As was noted, this balancing chamber did not contain a nylon back-up ring. In the early 1970s, the HP system was modified to permit the use of the back-up ring system. This necessitated a longer poppet pin, deeper internal shelf in the poppet, and longer poppet retainer assembly. When this new system was introduced, Voit also made other obvious changes. The yoke no longer had the stepped appearance, and it was thicker in construction. These particular heavy yoke regs are fine to use with cylinder pressures in the 3,000psi range. The phenolic gasket that was between the retaining nut and diaphragm was also eliminated.
The second stage initially bore the title, “Titan II MR-12”. The Titan II reg predated the new model by a few years, and the first stage was actually first used on the double hose Trieste model. The second stage performed so well on the USN breathing simulator, that it was paired with the new MR first stage. Hence, the name being Titan II MR-12. This created confusion with the two models, and the name was simply changed to MR-12. The name actually means Military Regulator 1 Hose 2 Stages. It has the great honor of being the first single hose regulator to meet the USN qualifications for breathing performance. Early models of the Titan II MR-12 did contain the tandem exhaust valves. The neoprene exhaust valves of the time were not always the best at sealing, so the two valves ensured that the reg breathed dry. The problem was that it increased the exhalation effort. When a better sealing valve was introduced, the tandem system was eliminated. BTW, when the USN tested the reg on the simulator, it did not have the tandem valves.
I can’t tell from the pictures, but the earliest regs also had a satin finish on the case assembly, with the shiny chrome on the cover. To me, this was very pleasing to the eye.
One other interesting difference was that the second stage poppet had a straight, square shank. This was changed rather early to the stepped version seen through the remaining years.
Finally, the LP and HP port plugs had a flattened top, with the wrench flats being 9/16” rather than the later 1/2” style.
The neckstrap assembly was also one piece, as compared to the two piece unit introduced in 1969-1970.
Updated with a Mares Abyss second stage diaphragm, and Aqualung or Mares first stage poppet assembly, the reg is actually a very nice breathing system. While serving as the Science Editor for Rodale’s Scuba Diving Magazine, I had the opportunity for such a modified MR12 (1971-1972) to be tested on Scubapro’s ANSTI breathing simulator. At 132ffw and with a 40rmv (respiratory minute volume), it easily exceeded the USN standards for the 1970s. In fact, that particular reg met the 132ffw standards down to 165ffw, and nearly to 198ffw.
I have made several dives with my restored Titan II MR-12 regs. I really enjoy them, and especially like diving with the first USN approved single hose model.
I hope that Mares continues making some version of the MR12 for many years. To me, it pays homage to the original.
Last Edit: Aug 21, 2015 4:48:06 GMT -8 by gregbarlow
Greg, excellent, thank you for all the info! I know someone with a Titan-II first stage that I'm hoping he will sell me, as a replacement for this one with the cracked yoke If I do get it, I'll just swap out, I hope, the parts I just rehabbed...