Down Stream Single Stage Regulator?

[seakrakken]

Was there ever a Down Stream Single Stage Double Hose Regulator? The Mistral is an Upstream Single Stage. Did Aqua-Lung make a Downstream? The reason I ask is I had once seen a cut-away diagram by Aqua-Lung of three different types of regulators and it was shown as one of the three. In my limited experiance and reading I have yet to see one. I would think that such a reg would start out easy to breath and get progressivly harder to breath from as tank pressure dropped. That would be a sure-fire way to know it's about time to surface!

[Seahuntjerry]

Hi,
Yes there was a downstream single stage double hose regulator produced by Voit.
This was the Fifty fathom in Chrome or painted blue as used in SeaHunt.
Usually they breathe Hard to start around 2" with 2475 psi opening pressure.When the tank is lower its REALLY hard.
I did a dive on the Lct wreck in fifteen feet of water
In the Bahamas,Thundeball and Seahunt was shot on this site.
Jerry Inland Divers Vintage scuba divers club #2

[SeaRat]

Seahuntjerry is correct, AMF Voit did produce two downstream, single stage double hose regulators (the second was a plastic version called VRC-2 Blue 50 Fathom). They are described in Basic Scuba, by Fred Roberts as "VCR-2 50 Fathom (1959, 1960, 1961), Two Hose; Single Stage: Downstream Push-Pull, Lever Operated Seat." I have one interior that I have put into a Mistral box, and I have written about it both here and an another diving website.

The VCR-2 in both incarnations is an extremely easy breathing regulator, especially at high tank pressure. The reason that Seahuntjerry states that it is a hard breathing regulator is that the regulator's mechanism is improperly aligned inside the regulator box, and I believe this was intentional by AMF Voit. If it is correctly aligned, with the large hole pointed directly down the intake hose, this becomes one of the easiest breathing single-stage, two hose regulators ever conceived. It has a very powerful venturi effect. I think the reason AMF Voit oriented the small hole down the intake is that this was an inexpensive regulator, and it out-performed their most expensive regulator when configured correctly.

By the way, you cannot use a Mistral or other upstream, single stage regulator on a 3000 psi system; the seat will be damaged.

This is not true of the VCR-2 50 Fathom regulator. It has the same yolk as is used on the DA Aquamaster (without the cutouts, so it's actually a bit stronger). The DA Aquamaster was used for years by the U.S. Navy on 3000 psi tank systems. The VCR-2 50 Fathom regulator can also be used on 3000 psi systems, as there is no excess pressure on the seat. It is simply lifted, and may leak a little bit.

John

[SDM]

When these regulators were first introduced by Voit I almost immediatley aquired 20 of these new units for a very reasonable price from Art Stanfield who was Voit's sales manager.

Because of their simplicty and restricted air flow at low tank pressure I had planned on using them exclusively in my recreational scuba classes.

Almost immediately they began showing signs of wear on the blue finish. With in a short time the students began complaining of funny almost rust like taste in their mouths. I suspected tank rust, so I performed the paper test on all the tanks, but no culprit was idenified

Out of courosity I took one of the regulators apart and much to my suprise I discovered that the 4 screws that are described as part number D5440 were made of ferrous metal and had rusted into four globs of rust. It was very evident why the students were complaining!

I had considerable difficulty removing the screws since any form of penetrating oil was a no-no, but persistance won.

I informed Voit about the problems of ferrous metal and the consquence of contact with salt water. I suspect that these regulators were some how targeted towards the fresh water diver in isolated areas where contact with fresh water would be of little or no consquence and simplle ruggedness of the regulator would require little or no maintainance. I was informed that the rust deposits was an isolated case as it had never happed before. To placate me I was given a number of new parts, some cases, box clips and of course new SS screws # D5440 which I installed.

I used the regulators for about another year with out difficulty other than excessive wear on the blue coating.

I have often questioned if this was indeed an isolated case? Were they targeted for fresh water useage? Perhaps some day I will have the answer..

And of course what would the vintage diver of today do with out Fred's book? Probably use special regulator edition of SDM???

SDM

30

[seakrakken]

I'm glad you guy's are here! I thank you all for the great info. The VCR-2 50 Fathom sounds like a great reg. I wonder how many are still around and how many parts are available. Does anyone have an exploded view or diagram of one? I'm curious about the interior on this one.

[dave]

So a 50 Fathom like the metal variety with the chrome case is safe on a 3000 psi tank? I was always told that this reg was the same as a mistral and as a result the seat was prone to damage on 3000 psi tanks. Was I told wrong?

[SDM]

I can't believe what I am reading in this guest's post!

"So a 50 Fathom like the metal variety with the chrome case is safe on a 3000 psi tank?"

ANSWER; "It certainly is safe just don't turn on the air."

"I was always told that this reg was the same as a mistral..."

ANSWER;

1) NO
2) READ THE THE THREAD
3) Read and STUDY F.M. Roberts book "Basic Scuba."
4) Aquire and STUDY SDMs REGULATOR ISSUES:
February 1959
June 1962
June 1980
May 1971
<ATTEMPT TO COMPREHEND WHAT IS WRITTEN >

".....as a result the seat was prone to damage on 3000 psi tanks. Was I told wrong? "

1) These regulators were produced almost 50 years ago, and were probably designed 50 to to 55 years ago.

2) During that era the majority of the SCUBA tanks were designed for a lower pressure; 2250 for the 71.2 and 2150 for the 70 and the regualtors were therefore developed and designed accordingly.

3) The design parameters for this regulators and all other regulators of that era were established based on this critera.

4) The regulator is almost 50 years of age and has had considerable use over a 50 year period. Since there is no traceability on the regulator it would be impossible to determine if it has been used as a rental with uncountable cycles of use or had it been setting in the corner on a bench for 50 years with no useage.

5) Even if the usage factor is considered average, there is the factor of metal fatigue which can be associated with age.

6) Therefore, there is always a possiblity of damage to the various componets of a mechanical device such as a regulator, especially by those who operate in the dark devoid of even the basic knowledge of regulator operation.

After spending my evening answering this post I have a strong felling at Dave (?) does not own a Voit 50 Fathom regulator nor has he ever had one in his hands. So therefore this effort was a waste of my time responding and the readers reading the response.

But now we know......

or I hope we do,

SDM

30

[SeaRat]

Okay, I'll bite too.

The VCR-2 50 Fathom and the VCR-5 Blue 50 Fathom (plastic case) regulators have a downstream seat. The seat therefore is not flattened, but raised off the metal by the air pressure. It therefore is not damaged by higher pressures.

The V-55 Blue 50 Fathom (1962- ) is an upstream push-pull lever operated seat, and it will be damaged by higher pressures.

As stated above, there is time to factor into this situation; the yolks were designed for the 2475 psi tanks (2250 psi + 10% overfill). But, as I stated above, the same type of yolk was used on US Navy DA Aquamasters at 3000 psi. I own both Mistrals and the internal mechanism for the VCR-2 50 Fathom regulator. I have put a Mistral on a 3000 psi tank last year, and destroyed the seat (I have several). I put the VCR-2 50 Fathom on a 3000 psi tank and had no problems. DO NOT DO THIS WITH AN UPSTREAM, SINGLE-STAGE REGULATOR! You may have to disassemble an AMF Voit two-hose, single stage regulator to determine which one it is. I hope to post later the diagrams from the SDM article from February 1959 that I have to show what in looks like.

John

[seakrakken]

Good points made by both Gentlemen. I can appreciate the fact that the design criteria of the Regulators made in the 50's and 60's do not make them candidates for 3000 PSI. I can also appreciate that a Voit VCR-2 50 Fathom in prime condition has successfully worked at 3000 PSI. I can see how the Down Stream valve seat should prevent it from being obliterated by a higher tank pressure than it was designed for but, I can also forsee numerous other mechanical issues which might arise in the long run. All of the great info brought out in this thread has made me interested in making a VCR-2 50 Fathom my next addition to my tiny vintage equipment collection. This is the very best forum I've found on vintage gear and I will always come here to learn more from you guys. Sam please don't think that your post was a waste of time. I've yet to see anything you've said that wasn't valuable.

[Frank]

I took my newly restored 50 Fathom (painted version) for a first dive 8/22/04 in the shark infested waters of Mendocino and it worked like a charm. In shallow water (20 feet) I thought that it compared favorably to the DW Mistral. I was impressed, from what I had read I thought that it would not preform as well. I was using a 2250 psi tank. Franko

[SeaRat]

I hope to include the drawings from the February 1959 SDM article on the Voit 50 Fathom in this post. I am going to quote from that article here:

Voit's Engineering and Development Department, one of the largest and best staffed in the sporting equipment industry, is constantly experimenting to develop new products to fill existing needs, and to improve existing products to do a better job. After several years of experience with fine single stage and two stage regulators of the double hose type, plus an excellent single hose type regulator, Voit has developed and offers for the first time this year a new "50 Fathom" Regulator, describded on these pages. Proved in pressure chambers to 600 feet, and in actual use by a number of the country's leading divers, the new regulator checks out as an easy breathing regulator and simple to operate through minimum working parts, making it also easy to maintain. Finished in blue, with pearl gray hoses, it is also offered as the best appearing regulator...

PRINCIPLES OF "50 FATHOM OPERATION

Voit's new "50 Fathom" Regulator is of traditional double hose style, regulator behind the diver at the tank valve, and with non-return valves built into the intake and exhaust hoses. It is a single stage unit, with one high pressure valve to reduce tank pressure to breathing pressure, but it utilizes the Venturi principle, not in the hoses but within the body of the regulator. In addition to the unsual air-flow channel, there is a very fine second air hole. This design provides a compensating principle to make the air flow easier at any external pressure--compensates to provide easy breathing at all depths. The same reliable, constant easy breathing normally associated with a two stage regulator is thus achieved in Voit's single stage unit.

DETAILS OF REGULATOR FUNCTION

When the diver inhales, it creates a suction pressure in the cavity of the regulator which activates the diaphragm. This activates the straight lever, whichin turn activates the second, curved lever. This second lever then activates the toggle, which pulls away the seat disk assembly from its seat in the body of the regulator. This opens the holes in the body, allowing air to flow to the intake hoses and into the diver's lungs. One hole in the regulator bodiy is a very tiny hole with its axis in the direction of the box outlet. THis creates a jet effect, utilizing the Venturi principle and making breathing considerably easier than if there were just one hole and one air channel. THis size, location and combination of holes inthe regulator body are, of course, engineered to compensate and moderate the flow of air and to establish it at the amount and pressure for the required level. With only a half-dozen moving parts, Voit's new regulator is one of the simplest regulating mechanisms yet developed, the minimum parts designed for the surest performance and easiest maintenance.

You can see that this has some interesting statements in it. In the first part of the text, it describes the small hole as a "compensating" hole. This implies that it is compensating for the amount of air coming out of the large hole that goes down the intake hose.

But in the second part of this description, it shows the opposite, with the small hole oriented down the intake hose. This theoretically would provide greater velosity, and perhaps greater Venturi effect, but that is not the reality. I have experimented extensively with this regulator, in both positions, and it performs much, much better with the large hole oriented down the intake hose. To do this, however, you must remove the "DS455 dowl pin" and eithe not use it, or re-drill the Top Box Assembly to accept the Body in a different orientation.

The drawings show something very interesting too, and that is that the main amount of air is hitting the case, and not going down the intake hose. Re-alligning the body takes care of that, and prevides probably the best Venturi effect of any single stage, two hose regulator.




John

[seakrakken]

Great Post John, are there any internal pics available of your 50 Fathom? I really like to peak inside one.

[SeaRat]

SeaKrakken, and others,

I don't have photos of the inside of my 50 Fathom, but we had a similar discussion last October on the Scuba Forums website. You can go to this site, and read about our favorite regulators. On the first of three pages, they show the internal workings of the AMF Voit 50 Fathom (but in the wrong orientation). On the third page of this thread, one of the divers has taken me up on re-orienting the body, and I think you'll find his remarks enlightening. He also has a beautiful photo of the interior of the AMF Voit 50 Fathom after he modified it. Here's the thread:

www.scubaboard.com/showthread.php?t=37835

John

[Gomez' echo]

Thanks for all the information on the VCR-2 Voit 50 Fathom. I have had one for a while and would dive it a couple of times a year. It was not the best breather. I did the modifications as suggested in the above threads and found the reg to be almost as easy to breathe as my Royal AM. Thanks for the info. I did not however reinstall the pin after rotating the venturi hole toward the intake hose. I tightened the yoke nut as tight as possible. Does anyone think that the pin needs to be reinstalled in a new hole in the case back?

[Linda]

Outstanding photo!

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