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Post by SeaRat on Oct 28, 2022 16:12:55 GMT -8
The first stage is the mechanics of the Titan (another one) from aqualung, not a bad horse. Aqualung would celebrate tue 50 years birthday of the Mistral, and present a double hose. First they thought of using a commercial version of the Mentor but the Mentor failed passing the restrictive EN 250 for the européen market. Aqualung decided to find another way. Why did the Mentor fail to pass EN 250? Did it also fail US standards? It could have had a market in the US, maybe? We have a thread here on the Mentor. Ryan Spence, of Flashback Scuba, has one and posted about it, starting an interesting discussion. vintagescuba.proboards.com/thread/881/aqualung-mentor-photos-etcI have the PDF of the Mentor Technical Maintenance Manual. You can also get it at Ryan's Flashback Scuba website: www.flashbackscuba.com/museum/Aqualung%20Mentor/Aqualung%20Mentor.htmlHere's a photo from Ryan's site: These regulators were all hand-made at Aqualung. Three apparently went to the U.S. Navy Experimental Diving Unit, but I have yet to see their test results for this regulator. In the manual, it does say that if the regulator is breathing hard, "6. Nozzle (49) is in too far." and "6. Set nozzle flush with cone." Now, looking at the photos of the Mentor, I think it would have problems passing the exhalation resistance that the EU has set for regulators, due to the rather small exhalation mushroom valve in the case. But that's just my opinion. Okay, my thoughts are confirmed by this article in Historical Diver. John
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Post by spirou on Oct 29, 2022 2:00:59 GMT -8
The first stage is the mechanics of the Titan (another one) from aqualung, not a bad horse. Aqualung would celebrate tue 50 years birthday of the Mistral, and present a double hose. First they thought of using a commercial version of the Mentor but the Mentor failed passing the restrictive EN 250 for the européen market. Aqualung decided to find another way. Why did the Mentor fail to pass EN 250? Did it also fail US standards? It could have had a market in the US, maybe? hello with regard to the EN250 standard we consider an equivalent air flow for a breathless diver at 150 ft with a pressure of 500 psi in the bottle of another regulator pay the price like the micra for example (I use Google translation)
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Post by spirou on Oct 29, 2022 2:08:25 GMT -8
About the venturi effect he is very strong, I must post a little video , for me clamping ( en français le bridage) like on others dh comes in my mind from the inhalation valve in the mouthpiece. I dive since few month without this valve and the regs breath like ( my felling) a single hose when the regs are well placed
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Post by spirou on Oct 29, 2022 2:18:49 GMT -8
Why did the Mentor fail to pass EN 250? Did it also fail US standards? It could have had a market in the US, maybe? We have a thread here on the Mentor. Ryan Spence, of Flashback Scuba, has one and posted about it, starting an interesting discussion. vintagescuba.proboards.com/thread/881/aqualung-mentor-photos-etcI have the PDF of the Mentor Technical Maintenance Manual. You can also get it at Ryan's Flashback Scuba website: www.flashbackscuba.com/museum/Aqualung%20Mentor/Aqualung%20Mentor.htmlHere's a photo from Ryan's site: These regulators were all hand-made at Aqualung. Three apparently went to the U.S. Navy Experimental Diving Unit, but I have yet to see their test results for this regulator. In the manual, it does say that if the regulator is breathing hard, "6. Nozzle (49) is in too far." and "6. Set nozzle flush with cone." Now, looking at the photos of the Mentor, I think it would have problems passing the exhalation resistance that the EU has set for regulators, due to the rather small exhalation mushroom valve in the case. But that's just my opinion. Okay, my thoughts are confirmed by this article in Historical Diver. John Hello in a little book on the Mistral, it is written, that mentor was a specific demand for the replacemet of the SNARK III whit limitations.
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Post by spirou on Oct 29, 2022 2:23:21 GMT -8
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Post by vance on Oct 29, 2022 7:34:54 GMT -8
About the venturi effect he is very strong, I must post a little video , for me clamping ( en français le bridage) like on others dh comes in my mind from the inhalation valve in the mouthpiece. I dive since few month without this valve and the regs breath like ( my felling) a single hose when the regs are well placed So, without the inhalation non-return valve in the mouthpiece, you felt it breathed very well. If the restriction of air flow is caused by the Mistral's mouthpiece or its non-return design, I wonder if overall performance would be improved by using a different mouthpiece like a DSV or standard USD EZ? Has anyone tried this?
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Post by SeaRat on Oct 29, 2022 8:22:48 GMT -8
I personally rejected the New Mistral because it would not fit on any of my doubles. With the little hose connecting the first and second stages, if I attempeted to mount the regulator on my doubles manifold, the second hose kept me from doing so.
I have never even breathed off the New Mistral, although my LDS has one on display. I should ask her if I could mount it on a single tank and take a few breaths.
John
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Post by luis on Oct 29, 2022 15:00:22 GMT -8
[/div] [/quote] I have a couple of the new Mistrals. One of them, I have used a few times, including for some chest mounted experiments. There are pictures around somewhere of those dives. The cracking effort on the new Mistral can be adjusted to a very respectable low level. The issue is that it has "zero" venturi assistance. If you look at the two pictures above you can see the second stage port (on the first picture) is pointing at an angle from the tip of the poppet screw. If you look at the second picture, the tip of the poppet screw is what is pointing down the horn. The gas flow is totally directed against the side of the case. All the flow hits the inside of the case. When I say there is "zero" venturi flow assistance, I am not exaggerating. I am not only talking about observation, but I have instrumented it and measure zero flow assistance. I have kept the one working unit I have with the hopes of some day adding a little tube to direct the flow with the hope to create some flow assistance. The space is very tight, so I may have to solder a copper tube. Someday I may get back to it. The trick is going to be attaching a tube to direct the flow without choking the flow... The other new Mistral I have is a new in the box, one of the special edition ones. I keep on thinking that someday it may become a collectors item... I keep on dreaming...
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Post by SeaRat on Oct 29, 2022 15:14:14 GMT -8
[/div] [/quote] I have a couple of the new Mistrals. One of them, I have used a few times, including for some chest mounted experiments. There are pictures around somewhere of those dives. The cracking effort on the new Mistral can be adjusted to a very respectable low level. The issue is that it has "zero" venturi assistance. If you look at the two pictures above you can see the second stage port (on the first picture) is pointing at an angle from the tip of the poppet screw. If you look at the second picture, the tip of the poppet screw is what is pointing down the horn. The gas flow is totally directed against the side of the case. All the flow hits the inside of the case. When I say there is "zero" venturi flow assistance, I am not exaggerating. I am not only talking about observation, but I have instrumented it and measure zero flow assistance. I have kept the one working unit I have with the hopes of some day adding a little tube to direct the flow with the hope to create some flow assistance. The space is very tight, so I may have to solder a copper tube. Someday I may get back to it. The trick is going to be attaching a tube to direct the flow without choking the flow... The other new Mistral I have is a new in the box, one of the special edition ones. I keep on thinking that someday it may become a collectors item... I keep on dreaming... [/quote] Luis and Frederic, How about using an old Mistral orifice and modifying the hole to accept it as a screw-in, pointed directly at the inhalation horn of the New Mistral? Fred Roberts was very kind in his words about the old Mistral’s orifice, and it would be in the same Mistral family. Roberts talks Venturi001 by John Ratliff, on Flickr John
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Post by luis on Oct 29, 2022 15:30:08 GMT -8
If you hold one of the new Mistral in your hand (with the cover off), you will see there is no space for anything like that. The reason I am thinking of a copper tube is because it may be able to be formed to fit, but there is no space for threads. That is why I mentioned soldering it to the second stage body. If you look at the second picture, you can see the slopped section of the housing is very close to the gas opening on the second stage. If it was easy... I would have already done it... I understand venturi flow dynamics very well... what is always hard, is packing 2 pounds of hardware in a one pound box... (that is old engineering saying)
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Post by SeaRat on Oct 29, 2022 16:32:56 GMT -8
If you hold one of the new Mistral in your hand (with the cover off), you will see there is no space for anything like that. The reason I am thinking of a copper tube is because it may be able to be formed to fit, but there is no space for threads. That is why I mentioned soldering it to the second stage body. If you look at the second picture, you can see the slopped section of the housing is very close to the gas opening on the second stage. If it was easy... I would have already done it... I understand venturi flow dynamics very well... what is always hard, is packing 2 pounds of hardware in a one pound box... (that is old engineering saying) Luis, I know you know about Venturi; I put that into the post for other, non-engineers like me. You gave me a laugh when you said, "If it was easy...I would have already done it..." I get that. I like your thought of a soldiered copper tube. Now, one other thought; we being who we are we are not beholden to any particular case. What about routing that LP hose into an old Mistral regulator box/mechanism? It would be an Old/New Mistral. Now, about the Mentor, I think that originally it was designed with a much larger mushroom in mind. I'll bet that it was downsized for cost purposes, to use an existing mushroom rather than a super large one like the Snark III had/has. If you look at the area around the mushroom, you can see that a much larger mushroom valve could easily have been accomodated, along with a large wagon wheel/spider apparatus to hold it. I think someone made a decision that rather doomed it, but that could be pretty easily overcome to make it quite a nice regulator, not one confined to 25 feet of water in a pool. John
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Post by vance on Oct 29, 2022 17:17:51 GMT -8
Not having one to look at, it's difficult to know, but what about a whole new second stage body design, with the orifice(s) on or near the top so the air jet is directed down the intake horn? Maybe with a bleed jet or two as well?
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Post by SeaRat on Oct 29, 2022 17:21:49 GMT -8
I have just confirmed my suspicion about the exhaust valve for the Mentor. Here's the parts diagram for the Mentor: Mentor Parts Diagram by John Ratliff, on Flickr Note that the part number for the #21 Exhaust Valve in "107822." And here's the parts diagram for the Glacia: Glacia Second Stage Parts Diagram by John Ratliff, on Flickr Note that the part number for the #22, Exhaust Diaphragm is also "107822." The exhaust valve numbers are the same for both regulators, and so I assume that they came from the same place. I think that cost saving measure cost the Mentor it's rating from the Navy EDU. Single hose regulators have a different environment for the exhaust valve than do double hose regulators. I think for single hose regulators (Aqualung especially) in most positions they are opening into air, whereas because of the case orientation of the top box of any double hose regulator, the exhaust mushroom is opening into water. John PS, does the valve insert, #10 and lever, #14 on the Glacia look suspiciously like the New Mistral’s valve parts?
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Post by luis on Oct 29, 2022 18:33:30 GMT -8
Hi John, Now you gave me a laugh… cost savings… not really. If you look at that regulator, you can tell there was no cost savings anywhere. You don’t even want to know how much we paid (the tax payers) for those regulators. The good thing is that it was a very limited production, and in part that is why they cost so much. They were hand crafted and they were beautiful (I say "were", because they have seen some abuse by now). Seriously, cost was not an issue… Making custom mushroom valves is not that big of a deal… They made custom diaphragms, etc. (even the hoses I think are custom made and they are not cheap). For the resources that Aqua Lung has, if they used a valve they had, is just because there was no need for a different one. Plus, there are a lot of mushroom valves available from the re-breather world. The accessibility of larger mushroom valves is trivial. Now I am sure you would know that if you add a larger mushroom valve, ten you have to detune the cracking effort to avoid a free-flow (in some position) when the top edge of the exhaust is higher than the center of the demand diaphragm. I have done that design trade-off myself, when designing the Argonaut. Lots of opinionated divers (OK only a few) thought I should have used a larger mushroom valve, but the trade-off is not good and most of the resistance is not there anyway. BTW, I do see some restriction in the flow area on the round-to-square transition on the horn… I am just saying… The horn is often the smallest flow cross-section, specially with a metal can, due to fabrication limitations. I have played with a Mentor and it is a beautifully crafted regulator. The 25 ft limitation has absolutely nothing to do with the regulator. That was just all they needed to certify for. They only had one purpose for this regulator and it is just for training, before getting into re-breathers. They use re-breathers for actual missions…
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Post by luis on Oct 29, 2022 18:42:13 GMT -8
Not having one to look at, it's difficult to know, but what about a whole new second stage body design, with the orifice(s) on or near the top so the air jet is directed down the intake horn? Maybe with a bleed jet or two as well? I assume you are referring to the new Mistral and not the Mentor. The real problem with the new Mistral is the case (the housing). The housing is relatively small and the horn is directly opposite to the opening for the second stage body. Designing a new second stage is always a possibility, but it would be tricky in the existing housing.
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