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Post by luis on Feb 28, 2008 3:19:07 GMT -8
Is that squishy little translucent dome which is over the first stage diaphragm just decorative? I don't feel any fluid under it, so I don't think it is environmentally sealed....or is it? If it isn't, can it be filled with silicone fluid and sealed? I think you are referring to the outer environmental diaphragm. It is mostly a clear silicon rubber membrane. It transmits the ambient pressure to the button under it and that button has a push rod that pushes on the diaphragm. You could remove that button/ push rod and fill it with fluid, but why make a mess? This new style dry seal chambers seem to work fine and they are clean and easy to deal with. To adjust the IP all you have to do is remove the ring with a spanner wrench and you can access the adjustment screw with a hex key (Allen wrench), no need to mess with any fluids or silicon grease. This is something I wrote recently at ScaryBoard (http://www.scubaboard.com/forums/regulators/222315-advantages-non-enviro-sealed-diaphragm-1st-stage.html ) on this subject:
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Post by duckbill on Feb 28, 2008 9:38:38 GMT -8
Thankyou, Luis. I didn't know about dry-chamber seals. I'm trying to picture this. Does the push rod pass through the IP adjustment allen keyway then?
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Post by luis on Feb 28, 2008 10:17:01 GMT -8
Thankyou, Luis. I didn't know about dry-chamber seals. I'm trying to picture this. Does the push rod pass through the IP adjustment allen keyway then? Yes. Take a look at item 31 (“load transmitter”, catchy name) on the Titan, or item 45 (piston) on the Conshelf. The old Conshelf Supreme has a chamber that you can fill with 2 oz. of silicon fluid (look below item 39). I just won one in eBay. If I decide to use it for a spare or pony bottle, I may change the chamber to a dry chamber.
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Post by duckbill on Feb 28, 2008 12:45:08 GMT -8
That is great information! I have a Conshelf Supreme but never went through the hassle of getting silicone fluid for it so I could overhaul it. I wonder if the dry kit has any disadvantages compared to the fluid type. It would be interesting to know if Aqua-Lung did something for the dry kit to assure that the surface areas of the inner and outer diaphragms match, as you mentioned in your SB post. Congrats on your win. I've never heard a bad thing said about the Supreme.
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Post by SeaRat on Feb 28, 2008 17:30:26 GMT -8
Duckbill,
I think I looked into that, and yes the first stage can be environmentally sealed and protected.
I'm going to back away a bit from my statement about the venturi effect on the New Mistral, as I remember testing it at the LDS, and it breathed quite nicely there. It would initiate a flow that I needed to breath-back into the mouthpiece to stop. So it could be that the small case, along with the rounded sides, provide the flow distribution toward the intake hose. I will have to use one in the water to make a final determination, but that is a good possibility. It's kinda like what BroXton Chuck was saying about the DA Aqua-Lung, that pointed the released air at the case instead of down the hose. Only, with a much smaller area, and much smoother surface, the New Mistral may be better at it.
Concerning the small diaphragm, it is not the size of the diaphragm that matters so much (the Trieste II has a smaller one too), but it's flexibility and responsiveness. Note that the single hose regs sometimes operate with a very small diaphragm. Once I changed the diaphragm to my Trieste II, it breathed much nicer (home-made diaphragm).
John
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Post by luis on Feb 28, 2008 18:37:03 GMT -8
Duckbill, I think I looked into that, and yes the first stage can be environmentally sealed and protected. I'm going to back away a bit from my statement about the venturi effect on the New Mistral, as I remember testing it at the LDS, and it breathed quite nicely there. It would initiate a flow that I needed to breath-back into the mouthpiece to stop. So it could be that the small case, along with the rounded sides, provide the flow distribution toward the intake hose. I will have to use one in the water to make a final determination, but that is a good possibility. It's kinda like what BroXton Chuck was saying about the DA Aqua-Lung, that pointed the released air at the case instead of down the hose. Only, with a much smaller area, and much smoother surface, the New Mistral may be better at it. Concerning the small diaphragm, it is not the size of the diaphragm that matters so much (the Trieste II has a smaller one too), but it's flexibility and responsiveness. Note that the single hose regs sometimes operate with a very small diaphragm. Once I changed the diaphragm to my Trieste II, it breathed much nicer (home-made diaphragm). John I guess when I have some time I am going to have to post some actual numbers. I have done both calculations and taken some test data with some instrumentation. I own three new Mistrals, I have only tested one and it sucks…both in and out of the water. I have also checked it with my gauges. Single hose regulators that breathe great with very small diaphragms are normally pneumatically assisted…sometimes with pilot pneumatic valves, but most common with pneumatically balanced second stages. The mechanical advantage is obtained by many different ways. And all means of mechanical advantage have tradeoffs. A big diaphragm is just one of the most effective ways of getting good mechanical advantage with minimal compromise, other than the size issue. In a single hose you can also design a much more effective venturi since there is no corrugated hoses that provide backpressure. Designing an effective venturi is a real science and to a lesser degree an art. These are pneumatic devices and most of the energy in operating them comes from the compressed air, but our inhalation effort is required to at least trigger the initial demand valve operation. It should be easy to mechanically balanced most regulator to have a relatively low initial, what is harder is to keep the WOB low during all flow rate requirements without having a regulator that tends to free flow. In a DH is even harder because the back pressure constantly changes with position and to a much lesser degree hose flexing. Scuba regulators are actually simple devices. For a better understanding of the mechanics behind a Scuba regulator I would like to recommend Peter J. Wolfinger book, but I just realize that he is closed. I just went to www.scubatools.com and there is just a message. There is a phone number, I wonder if he may have some books left. Well I got to go pack…I am going skiing in Vermont for the weekend.
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Post by nemrod on Feb 28, 2008 19:39:57 GMT -8
The size of the diaphram is very important. Flexibilty and responsiveness count as well but standard engineering force equations reveals Force X Area for a lrager diaphram to be significant if you compare the Trieste to the Aqua Master (and most others with full size diaphrams) it comes out way on the short end. I don't have a Trieste but after using a few I am not entirely impressed and I am truely dissappointed in that I was not. They just don't live up to the promise and just don't equal a good Aqua Master. The other thing I don't like about them is the integrated yoke. That is kind of archaic and cheaper design. Comparison of single hose and double hose diaphrams to one another is not really useful due to the difference in hydrostatic head the double hose has to work against that the single hose second stage does not. The Trieste is a beautiful vintage regulator and I would be proud to own one, don't get me wrong there but I may be more proud of my newest Phoenix II Voit Lung Navy V66. Nem
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Post by SeaRat on Feb 28, 2008 23:25:28 GMT -8
I think I've pretty well documented elsewhere the three main problems of the Trieste II: --Stiff diaphragm --Lower-than-optimal venturi assist --LP nozzle which allows the main air flow to be not quite straight down the hose.
I've overcome these with my Trieste II, and I'd put it up against any of the regulators you mention. It cracks at about 1/2 inch of water, and I need a deflection plate in the mouthpiece or it shoots on down the exhaust. It is one sweet-breathing regulator.
Concerning the New Mistral, I cannot say for sure as I've never dived one. But here's the breathing characteristics published on the Aqua Lung European website when the New Mistral first came out:
They also published the breathing curve, and tomorrow if I get time I may post it here. Aqua Lung also stated:
This is in keeping with my initial impression of the New Mistral, as I felt at the time it breathed well (surface only inhalation testing).
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Post by nemrod on Feb 29, 2008 15:47:45 GMT -8
I guess the problem is that the Trieste and the new Mistral are being compared to Royal Aqua Master with a variety of modern mods including a LARGE diameter and very soft and responsive silicone diaphram, aerodynamic cage valves and now the super soft new silicone valves.
Cracking effort is but one factor, flow rate and effort to sustain that given rate plus exhalation effort combine to equal WOB. I think several new Mistral owners have discovered their units had a lower than optimal IP from the factoy and have had a good result boosting it back to factory spec or a little better than factory spec. This may account for my less than favorable impression, high cracking effort and seemingly stiff draw once flow was initiated.
Anyone with a new Mistral should certainly work to optimise it and dive it, it is a good and safe and useful double hose with mediocre but very acceptable performance.
Nem
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Post by SeaRat on Feb 29, 2008 22:08:11 GMT -8
Well, Nemrod, I thought I had posted this earlier this morning, but apparently not. Here's the original ads for the New Mistral: And here's the flow information: I got these from the Aqua Lung European site when it first came out. Again, I have not dived the New Mistral, so all I can do is judge it on my in-LDS experience. I did not buy it, but because of incompatibility with my doubles systems, not because of performance. The Trieste II had issues, which I've fixed on mine. I'll stand it up against the Pheonix Royal Aquamaster too, as I feel it now performs pretty well. John
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Post by duckbill on Mar 1, 2008 1:20:38 GMT -8
Sounds like a challenge! Contestants on their marks. Get set. Breathe! Now at 50 feet. Get set. Breathe! Now at 100 feet..........
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Post by SeaRat on Mar 1, 2008 9:16:01 GMT -8
Comparing the New Mistral breathing curve with their other regs, the Legend LX ACD and Legend ACD had a 0.74 J/litre overall work of breathing, and went to negative areas on the inhalation (venturi assist). So it doesn't perform really well compared to their other second stages (Titan LX was 0.79 J/litre), and Aqua Lung did not publish this breathing curve in their USA literature. So you do have a point, Duckbill. I think the breathing contest would be interesting though. I'll put my Trieste II up against the New Mistral, and you can put the Pheonix Royal Aquamaster up against it. That should be fun. I think both these ol' regs (oops, Luis' Phoenix is not ol' ) would out-perform the New Mistral. But I also think the New Mistral is handicapped in that it must be mated to a single tank, and therefore the positioning of the regulator will not be optimal (too high on the back). John
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Post by nemrod on Mar 1, 2008 15:55:43 GMT -8
I have a new Titan LX and my wife has a new Legend. I will put my PI RAM up against either of those. It exhaust easier,is quieter and smoother and cracks at or below .5 inches. It also flows all the air I could use with very little IP drop.
Until we can put them on a machine we will never really know the whole story.There are about to be some tests made informally JFYI on the PII RAM.
I did not include the Trieste in "modern" because it was last made in about 1970 and there are no new parts or kits being made for it to update it to modern standards as there is for the Aqua Masters. The Trieste design is also in my opinion, an inferior design for much the same reason the new Mistral is. That is an opinion, you may not agree, I am not likely to be convinced otherwise after looking at the Trieste.
The new Mistral does not by ALs own data stack up very well thus I feel that my original impression of it was accurate, it breaths stiff and seems short on delievery. Adequate and safe but nothing to write home about.
Nem
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Post by JES on Mar 1, 2008 16:41:28 GMT -8
.... The Trieste design is also in my opinion, an inferior design for much the same reason the new Mistral is. That is an opinion, you may not agree, I am not likely to be convinced otherwise after looking at the Trieste. ...Nem I think it's just that you're spoiled now with the PRAM and the modified RAM.
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Post by nemrod on Mar 1, 2008 17:25:24 GMT -8
I used to drool over the Trieste, then I saw what they are internally and now I don't like them except for vintage. Then I realized they have a light duty yoke that is integral with the body and I liked that even less. It is not like they are not a fine vintage regulator, beautiful and desireable because they are kind of rare but the original post was not so much vintage oriented as it was seeking a double hose that could perform to modern standards and be easily serviceable with readily available parts, that pretty much leaves the Trieste out.
I haver several Voit MRs with essentially the same integrated yoke, it has a lot of stretch at 3,000 psi, maybe even more than the standard light yoke (USD).
I wonder sometimes what exactly is the history of the Trieste. Up until about 64 the Voit regulators were similar to the Aqua Master and Mistral with the Navy essentially being a relabled DA Aqua Master. Then they dissappeared from the catalogs and a few years later the Trieste appears. Perhaps there was a falling out with USD and Voit had to figure out a double hose on their own and the Trieste was it? Anyone know all the history on this?
Perhaps someday there will be a vintage shoot out that is more than antedotal mine is better. That would be great fun to see these on a real test. I suspect many of us might be dissapointed with the hard numbers (me included).
The Trieste appears to be a double hose with MR first stage and the RAM is a double hose with Titan first stage, same as the Titan LX and new Mistral, pretty typical AL stuff to this day.
Nem
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