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Post by antique diver on Sept 22, 2022 21:01:29 GMT -8
Some years ago I "inherited" a few boxes of Scuba junk from a friend that had been in the regulator repair business for a long time, and was cleaning house before moving to Belize. Mostly just an ugly mess, but there were several totally disassembled double hose regs in there, and I eventually restored several nice regs from that stash. Among other nice surprises there were the complete makings of an Aqualung Overpressure scattered among the remains, and it caught my eye because the label had survived in excellent condition. The Overpressure came out in about 1954 or 55, was Gagnan's first production with a venturi system, and also his first single stage double hose. It was an attempt to make an easier breathing double hose than the earlier two stage regs had been. I put it together, devised some mouthpiece valves to replace the missing ones, and took it diving once. It did not breathe well, so I tinkered with it a few times without much improvement, and eventually put it away as a lost cause. After reading some other postings this year about how well they delivered air I decided to start over by trying different venturi jets and removing the small restricting mouthpiece valves. It made a huge difference on the bench. I was a bit concerned about the lack of one way valves in the air stream, but had dived some other regs that way in the past and figured I could manage a test dive.  I started out with clear plastic tubing for the inner air supply hose because it was more flexible, but later went back to the green oxygen hose like originally came on this reg. It makes the right hose just a little stiffer but hardly noticeable in the water.   Test dive in poor visibility with Seawolf nearby:  Having a long yoke available I put this antique pressure indicator on a banjo. I have always enjoyed this little gauge that loudly burps bubbles when air pressure gets low. (Some dive buddies have said it sounds more like a sound coming from the other end of a diver)  Okay, enough rambling. The Overpressure breathed very easily and smoothly unless I took a heavy gasp of air. That action gives quite a blast of air, but I found it was controllable by keeping the tip of my tongue at the roof of mouth to baffle the blast. I was satisfied with that, and figured it was time I tested my recollections of earlier dives with no mouthpiece valves. Flooding the hose loop seemed a little crazy, but it worked out as I remembered. It was accomplished by getting the regulator lower than the mouthpiece, which caused a free flow that pushed enough water out to take cautious breaths while lowering my left side and hose, and exhaling while continuing the left roll. Just like the old textbooks said! I must say that this is probable not a good regulator for a beginning diver, especially without the mp valves! |
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Post by SeaRat on Sept 22, 2022 22:02:24 GMT -8
I may be the only other diver on this board who regularly dives my Overpressure Breathing regulator. It is, in my opinion, one of the best-breathing regulators ever developed. And, mine has a mushroom valve in the inhalation side of the mouthpiece. I'll show you how below.  IMG_1235 by John Ratliff, on Flickr I too have a long yoke on this regulator, and a pressure gauge.  IMG_1254 by John Ratliff, on Flickr This is what mine looks like, with longer hoses than originally were on this regulator. The original hoses are still in use, but on my DA Aqualung regulator (Broxton). I like the longer hose a lot.  IMG_1234 by John Ratliff, on Flickr Here I'm using my Overpressure Regulator, shown in a reflection of my Pilot's window.  DX Overpressure Schematic by John Ratliff, on Flickr If you'll look at the schematic, you'll see that there is a washer in the intake near the mouthpiece, and a non-return valve.  IMG_2204 by John Ratliff, on Flickr Here is that disc in the mouthpiece. Note that I have added a non-return. Originally, there were two cones that went through the holes, molded into the non-return. But that mushroom valve melted away, and so I took another, cut off the center area so the Venturi tube would fit through, and sewed the valve onto the metal disc.  IMG_2203 by John Ratliff, on Flickr Here is what the other side looks like, with the knots on this side. By the way, I used dental floss rather than cotton-based thread. This produced a very good regulator, very reliable, and also very quiet. I have used it on a number of occasions over the years. I also put together a short video titled "Talking Underwater," about how we in the old days could talk to one another underwater. John |
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Post by antique diver on Sept 23, 2022 5:26:08 GMT -8
John, thanks for the info. My reg was missing that inhalation valve plate, and the good photo of it will allow me to make one from brass or maybe Delrin. I have a good selection of mushroom valves to experiment with. I had not thought of tying in place but that will likely be necessary to keep it in place.
I'm mainly hoping that this addition won't increase the cracking pressure by very much before the venturi becomes effective. I may try for a little larger cut out area and slightly larger valve. Right now it's extremely easy, just the way I like, and if I can't get similar results I could always just stick to the "valveless" approach... but I would feel a bit safer with the valve in place to keep the cans from flooding.
I agree that it is a nice breather and quiet like you say. Looking forward to some more diving on it with the valve in place!
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Post by nikeajax on Sept 23, 2022 7:54:56 GMT -8
Thanks for sharing gents! You can make a rivet for that plate by finding a piece of plastic that will fit through the hole then melting/flare the ends with something hot. I think you'd want to do it to the valve side before insertion, then the plate side.
Just a thought,
JB
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Post by antique diver on Sept 23, 2022 9:49:24 GMT -8
Thanks for sharing gents! You can make a rivet for that plate by finding a piece of plastic that will fit through the hole then melting/flare the ends with something hot. I think you'd want to do it to the valve side before insertion, then the plate side. Just a thought, JB JB, that's a good idea to try out, and easy to implement! Thanks for the input.  |
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Post by vance on Sept 23, 2022 15:38:45 GMT -8
I've had a couple of stock O-Ps. The hose in hose concept seems to work well, but I don't like the GUSH of air into your gob. It's similar to the MR-12 with the tube on the second stage. It makes me anxious.
It might just take getting used to. However I prefer a modulated venturi that provides what you need when you want it, regulated by how hard you pull.
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Post by scubalawyer on Sept 23, 2022 17:19:23 GMT -8
An O-P in good shape with original mouthpiece has been on my list of "must have, gotta have, really need" DH regs. Have never found one that is complete. Oh well, one of these days. M
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Post by antique diver on Nov 10, 2022 13:46:33 GMT -8
My Overpressure was missing mouthpiece valves and mounts, so I originally dove without them. Hose flooding and clearing went by the book (vintage diving manuals), but I was out of practice on that and felt a bit uncomfortable the first time or two. It really worked out fine, but in the interest of safety I wanted to at least try it with a one way intake valve to keep the can from flooding. Also the inhalation was almost a bit too "overpressure" (as was the common reputation of this reg) and I wanted to see if valve assembly might have just enough added resistance to tame the beast a little. Had to have something to hold the mushroom valve in place so made a mounting disc from delrin:  The valve had to have a center hole to accommodate the inner breathing hose, and I wanted to try to avoid tying or riveting the valve to the new delrin disc. Made a brass bushing and added an oring in the proper position to retain the center of the mushroom valve firmly against the disc. Slight changes altered the inhalation efforts and seal a bit, so it took several tries to get the correct fit of valve to disc and disc to metal mouthpiece. At one point I just about gave up and decided that I would just skip the mouthpiece valve. But a new day and fresh outlook had me start over, finally finding a good fit and good performance.  Following video shows inhalation cracking effort was easy and dropping quickly to about zero as the venturi became active. When you see the gauge needle fall a bit below zero it was during the exhalation. (I hope the link works. I was unable to figure out how to get it to show directly) i.imgur.com/1Bc2i5s.mp4The Overpressure behaved a little more gently with the valve in place, and I suspect it will dive just fine. I can also tweak the venturi a bit one way or the other with an adjustable nozzle I made a few years back. After experimenting with an exhaling valve in the mouthpiece I found it a bit too restrictive and will just let the duckbill do that job for now. Hope to hit the water again this month or next. |
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Post by SeaRat on Nov 10, 2022 14:12:15 GMT -8
'Glad to see someone else enjoying this unique regulator. I've got to get mine wet again soon, but the rivers here are a bit out-of-shape for diving.
John
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Post by vance on Nov 10, 2022 17:53:19 GMT -8
I always thought that the non-return valve issue was a non-starter. The difficulty of making one, and the amount of back-pressure with such a small volume of flow has got to be huge.
However, I have several old Spiro Mistral metal mouthpieces that need to be fitted with, at least, exhaust non-returns. So, I'm kinda interested. This might be a 3D printing job!
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Post by james1979 on Nov 11, 2022 5:21:45 GMT -8
I always thought that the non-return valve issue was a non-starter. The difficulty of making one, and the amount of back-pressure with such a small volume of flow has got to be huge. However, I have several old Spiro Mistral metal mouthpieces that need to be fitted with, at least, exhaust non-returns. So, I'm kinda interested. This might be a 3D printing job! If you have several, can you send me one for measurements and I'll send it back with wagon wheels? |
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Post by antique diver on Nov 11, 2022 7:02:31 GMT -8
I always thought that the non-return valve issue was a non-starter. The difficulty of making one, and the amount of back-pressure with such a small volume of flow has got to be huge. However, I have several old Spiro Mistral metal mouthpieces that need to be fitted with, at least, exhaust non-returns. So, I'm kinda interested. This might be a 3D printing job! If you have several, can you send me one for measurements and I'll send it back with wagon wheels?
Some regulators definitely inhale a bit easier without the incoming non-return valve, but I was interested in keeping water from the cans to make clearing water from flooded regulator and hoses easier. With air retained in the incoming hose and regulator cavity it is easy to blow the mouthpiece and exhaling hose clear by just turning into a position that places the regulator deeper than the mouthpiece. That should quickly cause the regulator to do the work of blowing water from the hoses with less physical maneuvering than old methods of hose clearing without mouthpiece NRV's. I haven't installed an exhaling side NRV due to the small size and resulting exhaling resistance. The inhaling resistance of this particular regulator is so low that the incoming NRV is not an issue. It remains to be seen how this works out during actual dives.
I look forward to hearing comments on the subject! |
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Post by james1979 on Nov 11, 2022 7:12:46 GMT -8
If you have several, can you send me one for measurements and I'll send it back with wagon wheels?
Some regulators definitely inhale a bit easier without the incoming non-return valve (I'll abbreviate to "NRV" for now), but I was interested in keeping water from the cans to make clearing water from flooded regulator and hoses easier. With air retained in the incoming hose and regulator cavity it is easy to blow the mouthpiece and exhaling hose clear by just turning into a position that places the regulator deeper than the mouthpiece. That should quickly cause the regulator to do the work of blowing water from the hoses with less physical maneuvering than old methods of hose clearing without mouthpiece NRV's. I haven't installed an exhaling side NRV due to the small size and resulting exhaling resistance. The inhaling resistance of this particular regulator is so low that the incoming NRV is not an issue. It remains to be seen how this works out during actual dives.
I look forward to hearing comments on the subject!I suspect that the "at least the exhaust" non-return is due to it having such a large impact in ease of clearing the loop. Regardless, I suspect that the intake NRV on the overpressure has negligible effect on the work of breathing due to the bulk of the air bypassing through the hose in hose nozzle. Speaking of the intake NRV for the overpressure, if you email me the measurements of your intake wagon wheel I can model that and run some off on the printer too. On the exhaust side, that is a small enough diameter mouthpiece that I imagine it will increase exhale work of breathing significantly.... question is whether it's "too much" Respectfully, James |
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Post by antique diver on Nov 11, 2022 7:56:25 GMT -8
I was wondering why you prefer to keep only the exhaust non-return valve (I'll abbreviate to "NRV"). Not arguing the point, just wanting some education on the subject.
Some regulators definitely inhale a bit easier without the incoming non-return valve (I'll abbreviate to "NRV" for now), but I was interested in keeping water from the cans to make clearing water from flooded regulator and hoses easier. With air retained in the incoming hose and regulator cavity it is easy to blow the mouthpiece and exhaling hose clear by just turning into a position that places the regulator deeper than the mouthpiece. That should quickly cause the regulator to do the work of blowing water from the hoses with less physical maneuvering than old methods of hose clearing without mouthpiece NRV's. I haven't installed an exhaling side NRV due to the small size and resulting exhaling resistance. The inhaling resistance of this particular regulator is so low that the incoming NRV is not an issue. It remains to be seen how this works out during actual dives.
I look forward to hearing comments on the subject! I suspect that the "at least the exhaust" non-return is due to it having such a large impact in ease of clearing the loop. Regardless, I suspect that the intake NRV on the overpressure has negligible effect on the work of breathing due to the bulk of the air bypassing through the hose in hose nozzle. Speaking of the intake NRV for the overpressure, if you email me the measurements of your intake wagon wheel I can model that and run some off on the printer too. On the exhaust side, that is a small enough diameter mouthpiece that I imagine it will increase exhale work of breathing significantly.... question is whether it's "too much" Respectfully, James I'll email you some photos and measurements of my inhalation wagon wheel/disc. The same diameter measurements would work on the exhale side, but without the 1/4" center hole that was necessary for the inner hose barb. An un-modified mushroom valve could be used on the exhale side, which could be made more like the conventional wagon wheel and have less impediment to exhaust flow. The disc I made is the same OD as the mouthpiece tube to maximize the working area, and it seals against the hose ID. The exhale side could probably be done the same way for maximizing exhaust area. As you stated, the inhaling valve hardly affected the inhalation effort since the inner hose carries the great majority of airflow. I forgot to mention this earlier, but inhalation effort is adjustable on my reg. I made a simple but effective way to adjust the venturi if needed. I'll post a photo later. |
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Post by SeaRat on Nov 11, 2022 8:59:16 GMT -8
Neither exhalation nor inhalation non-returns are necessary for the good working of the Mistral. It was designed without non-returns (La Spiro), and won't blow by without them. Performance is much better without them. As I said before, when I was in the U.S. Naval School for Underwater Swimmers, we did not use non-returns in the mouthpiece for much of the training. Bob Means and I put the non-returns in just before our pool harassment without the instructor's knowledge, which greatly helped us stay underwater when they ganged up on us. Bob and I were the last to be forced up, but that was really unusual work with the regulator (DA Aquamaster). Both Bob and I took off our masks and offered them to the instructors, and went through the pool harassment without masks too.
John
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