old diaphragms and tilt valves

[duckbill]

I have just acquired two of my oldest single hose regs yet. One is a tilt valve, and is the first such that I now have.
I have a question about the diaphragm.
The regulator is a Healthways "SCUBA Star", marked 4-61. The diaphragm is unusual to me because it is not the thicker, more supple variety with which I am all too familiar. It is pretty thin, is a coated fabric, and has NO stretch to it at all. It could be decribed as "krinkly". It just kind of hangs in the second stage in no particular form because the stem on the tilt valve only touches it at one small point and exerts very little outward pressure on it. Is this normal for tiltvalve diaphragms? It is the hardest breathing regulator I have ever tried. I would guess that this is partly because of all the "slack" which must be taken up in the diaphragm before the rod stem is pushed over. Now, I was trying the reg when dry. Maybe when diving the water pressure from the outside will help that diaphragm to "shape up", so to speak, and there wouldn't be so much slack in it then. I can't dive test it until I get my neck fixed, so I'm just curious as this is all new to me.

[luis]

I do recall some tilt valve regulators had weird diaphragms.
In the early 70’s we were strongly suggesting the owners to remove them out of service.
I can’t remember anyone actually diving with one.

Just make sure that the first stage has a good (working) pressure relive valve or a second down stream second stage.
With out a relieve valve, if the first stage has any kind of leak the intermediate pressure will build up until the hose bursts. I have seen it happen. I don’t mean to point the obvious, but sometimes we forget with this old gear.

If I recall that regulator has an unbalanced piston first stage. A minute first stage leak is inconsequential with a down stream second stage, but not with this.

[Captain]

I have a Healthways Scubair 300 sonic which is a down stream second and it has the same type of diaphragm. It is also a hard breather. Healthways probably used that type diaphragm in all the regulators.

[duckbill]

Thankyou, both, for your informative responses.

luis said:

Just make sure that the first stage has a good (working) pressure relive valve

Yes, I'm aware of the necessity of a working pressure relief valve, but I don't know how to test it or determine if it is freed up. Any hints?

[luis]

The only way I have tested them is with an adjustable first stage (a Conshelf in that case).
I can’t remember what it was set to leak at, but it wasn’t to high. The hose in my IP gauge is good for 400 PSI and my gauge has a bleed valve that I can open quickly if needed.

[SeaRat]

Duckbill,

This Healthways Scuba-Star was the first single hose regulator I ever had (my second regulator). I bought it in about 1961, and used it for about four years. My first regulator was also a Healthways, the Healthways SCUBA double hose regulator. I bought another Healthways Scuba Star just to have that regulator around, and try it out again in a pool. I replaced the piston "O" rings, and found it still a very difficult-to-breathe regulator. The fabric diaphragm has nothing to do with that, as I explain below. The fabric diaphragm needed a coating of silicone lubriant to get back its viability, but it is now as good as it was new, and presents no resistence to breathing--that is inherent in the regulator design.

The Scuba Star is an unbalanced piston regulator, meaning that the interstage pressure varies with tank pressure. Unlike the diaphragm first stages, an unbalanced piston has the highest interstage pressure at full tank pressure, and it goes down from there. Thus, under normal conditions, this regulator delivers slightly less air at low tank pressure than at the beginning of the dive. Also, Healthways had a habit of putting a restrictor orifice into the regulator. This was the "R" reserve feature for these types of regulators. This was discussed extensively on a different thread here, but basically by putting a restrictor orifice into the system, at low tank pressure you would be warned by greatly increased suction pressure that your air supply was running out. You would be forced to go toward the surface to receive the next breath, in fact, at very low tank pressures. Both of these contributed to the "hard-to-breath" characteristic of these regulators.

There were some interesting design characteristics too. This is a very robust design, and I bought one off e-bay last year. It's diaphragm is still in excellent shape after 40+ years. It has a minimum of moving parts, and is very easy to service. But, it also has the same characteristics of all single hose regulators of the time: a very small exhaust valve. This meant very hard exhalation compared to the two-hose regulators of the time, and also kept any of these regulators from meeting the US Navy design requirements for approval for Naval forces. Inhalation characteristics of the Scuba Star were also hampered because this was before the concept of venturi assist was introduced to Healthways single stage regulators. There is no venturi action in the Scuba Star design. But a sixteen year-old high schooler did not notice that (there, I just gave you my age) when doing club dives.

Concerning testing the safety plug, Fred Roberts in Basic Scuba[/U] states, "...If the safety valve leaks, readjust by unscrewing screw (19) with 200 psig in cylinder until leakage can be heard or seen when submerged in water. Close cylinder valve, bleed air with purge button and advance screw clockwise 1/4 turn in, or until leak just stops." He goes on to say that the safety valve may be releasing air if the interstage pressure is set too high (using shims), or if there is a leak in one of the "O" rings on the piston. He simply recommends replacing the "O" rings and lubricating them with silicone grease. I took mine out to the tank, and mounted it to do these tests. However, I would recommend doing it on a full (2250 psi) cylinder, rather than at 200 psi, as the higher interstage pressure is at full cylinder pressure. I did it the way Fred explained, and it leaked a bit at full cylinder pressure. Use a Allen wrench to adjust the inner nut out to get the point of leakage, then adjust it in (clockwise) to set the safety valve higher than the interstage pressure normally is when operating. This is easy to accomplsh, and shows the robustness of the design. It doesn't inprove the breathing characteristics though.

The only thing that would help the breathing characteristics of the Scuba Star would be to be 16 again, and be so entralled with simply being able to breathe underwater that you don't realize that you can hardly breathe. Here's a photo of me in about 1961 diving with the Salem Junior Aqua Club in Hood Canal, Washington and using the Scuba Star regulator.


John

[nemrod]

One of my MR12s has the fabric crinkly diaphram and it is the easier of the two for breathing. James

[duckbill]

Nemrod, now isn't that funny! An MR-12 was the other reg which came in this SCUBA garage sale lot along with the SCUBA-Star I mentioned. I haven't taken the MR-12 2nd apart yet, but it looks to be a downstream push-pull type, so I would suspect it would breathe more easily than the SCUBA-Star with either type of diaphragm. Thanks for the info. My MR-12 also has the same type of thin diaphragm under discussion.

SeaRat,
Wow! Quite a lengthy and detailed response. I appreciate that very much. Thankyou.
Great picture,too. Thanks for sharing that. Nice to hear from someone who has had first-hand experience with the SCUBA-Star in it's own day.
Much food for thought. Thankyou for giving me the rundown on the overpressure valve adjustment procedure. I would suspect that a 200 psi cylinder pressure was desirable to avoid the inevitable should the untested valve not function at all!
I had to think through your explanation a bit. A valve mechanism can be either balanced or unbalanced; diaphragm, piston, or a combination of the two; and the seat can be either upstream or downstream. Any combination of these three features is incorporated into the design. So, when speaking of an unbalanced piston, it's seat can be either upstream or downstream. It is this which determines whether the IP will raise or lower as the cylinder pressure drops. A diaphragm could be used instead of the piston, and the IP characteristics would be the same either way.
Anyhow, what you said makes a lot of sense regarding how the SCUBA-Star is a hard breather. I'll be looking forward to trying it in the water first chance I get. It will be very interesting to me to experience what a truly hard-breather is like. If what inhalation feels like dry is any indication, I can surely appreciate the engineering behind the venturi assist!

[SeaRat]

Duckbill,

The MR-12 is a balanced, diaphragm first stage and downstream second stage. It does have a venturi assist (holes pointed toward the mouthpiece), primitive as it is, which is effective and provides for good breathing characteristics. It is amoungst the first single-hose regulators approved for US Navy use. The neoprene-impregnated nylon diaphragm has no resistance to inhalation, and should last for years if taken care of (I had one come back from the Philippeans with holes, but I think something was eating on it).

If you set the Scuba-Star's overpressure relief valve at 200 psi according to what Fred Roberts said, it will leak slightly at full tank pressure (my experience last night, at least). This is easily corrected by putting it on a full tank after having set it at 200 psi, and adjusting it a second time. I think Fred wanted it initially to be on a 200 psi tank because of safety concerns if it had already failed, and if someone adjusted it all the way out and lost the mechanism.

Concerning the piston, unbalanced pistons of that time period were invariable downstream mechanisms, and a pure piston. Apparently, the manufacturers have gotten creative in the last few years, and are mixing the designs. But this did not happen at that time.

Another point, the Dacor Dart had a diaphragm first stage, and downstream second stage. So not all these regulators were piston design.

I went from the Healthways Scuba-Star to an AMF Voit design which was the early Calypso design, which was a really nice regulator (balanced first stage with a downstream second stage and a real venturi assist). It was a really nice breathing regulator, and the design Hannes Keller took to 1000 feet off Catalina Island in his famous (or infamous) dive. While proving his concepts of decompression, he lost his buddy on the dive (Peter --I'll fill in the blanks later). The UN Navy did not approve the design due to a small exhaust (in the diaphragm of the regulator).

John

[SeaRat]

I just googled "Hannes Keller," and got these results:

www.visipix.com/sites-en/story/

www.divinghistory.com/kellerdive.htm

Peter Small was the diver who was lost with Keller, and Chris Whitaker, a support diver, was also lost. It is an interesting bit of diving history. Keller continued his research into deep diving, as can be seen on the first site.

This site shows the Calypso regulator Keller was using, and some of the equipment.

www.divernet.com/history/1202atlantis.htm

John

[JES]

SeaRat,

Great information, and thanks for posting the great vintage photo of you!

[duckbill]

Hey, SeaRat, thanks for the links on the Hannes Keller stories. I can't quite make out the regulator shown. Is it the old Calypso with the metal exhaust ports in front of the diaphragm- the one where the mushroom valve is mounted in the diaphragm itself?
Well, I dissassembled and cleaned my overpressure valve on the SCUBA-Star yesterday, checked the IP (was 115@1725psi & 100@300psi), then adjusted it as you mentioned you found in BASIC SCUBA.
Speaking of BASIC SCUBA, I have the 1963 2nd edition and found the section pertaining to the SCUBA-Star. I've also been enjoying reading through the rest of the text as well, and have a question for you. If you have the 1963 edition (may also be in the 1960 edition), could you check this out and see if I am correct in thinking that this is backwards? It can be found on p.159 in Table 3-16 "Trouble Shooting Waterlung (1959), Sport Diver (1960....", under "d. Incorrect adjustment of over pressure relief valve."
There it says to "Turn screw (18) counterclockwise (left) slowly until air flows continuously. Turn clockwise (right) until flow stops completely, then back off (left) 1/2 turn.The pressure relief valve should now be from 15 to 20 psig above the intermediate stage pressure of 110 psig."
Seems to me that when you screw the adjusting screw in to stop the air flow you would be at the IP. Then it would seem you would want to turn it IN further to RAISE it above the IP, not "back (it) off".... That backing it off would cause it to leak air again. What do you think?

[SeaRat]

Duckbill,

Yes, that was the early Calypso regulator that Hannes Keller was using for those dives. It is the one featured on page 184 of Basic Scuba. In one of the early 1960s USD catelogs, Hannes Keller was featured prominently on the Calypso regulator page.

Concerning the adjustment on page 159 of Basic Scuba, you are correct, and I agree that the text in not correct. In fairness, I think the Fred Roberts probably got this text from Sportsways though, and that it did not come from his own observations. And yes, my tatered copy of Basic Scuba is the 1963, second edition of the book.

John