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Post by seakrakken on Dec 16, 2004 2:11:06 GMT -8
True! It would seem, that upon observing the differences between the HP Seats of the two regulators, that some math was thrown in favor of the Royal Mistral that was withheld from the standard Mistral. Someone mentioned earlier that the body of the Royal Mistral was somewhat longer than that of the standard Mistral. It would seem that the length of the spring and the seat body would account for that extra length. To what effect though? It would seem to me that the internal compound lever mechanisms of the Mistral Regulators share the same travel and mechanical advantage. It would stand to reason by virtue of that shared characteristic that the pin to unseat the HP Seat to allow in more air would travel a similar distance. If this is the case what was the point of making a longer body? Was it simply to accomadate part 111305? If this is the case and the additional part is, as the manuals indicate, unique to the Royal Mistral then it would seem possible to fabricate a similar part and make any Mistral a Balanced regulator. What are your thoughts?
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Post by Bryan on Dec 16, 2004 4:55:25 GMT -8
I have 3 of these regulators and none of them have part #111305 in them? Two of them are the exact regulator that is shown in the web link and one of them is the latest model double hose that was made by Spiro. I have no idea why none of them have this extra part? Nor has anyone ever been able to tell me why it would or would not have it. Basically the body inside the Spiro's looks exactly like the USD with the exception of a small stainless steel tube soldered into the side with a fitting on the other end to attach your HP gauge to. Pehaps is was designed to be a replaceable seat in the body ? Either way the entire design would have to be drastically changed to make it a balanced regulator. It really cannot be done without letting air pressure equalize on both sides of the HP seat.
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Post by Bryan on Dec 16, 2004 5:01:47 GMT -8
How is it clear from the photographs that the seat was designed for a higher pressure? On the subject of Mistrals, I finally got the new adjustment wheels done that I promised some of you months ago....Sorry for the delay! www.vintagedoublehose.com/parts/misc/index.html
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Post by nemrod on Dec 16, 2004 10:05:17 GMT -8
"How is it clear from the photographs that the seat was designed for a higher pressure"
Hi Bryan. Like I said I know I am not a regulator expert ---I was extrapolating from things I do know. The smaller diameter of the seat is what catches my eye as well the longer stroke. I could be entirely wrong so please do not think I am being a know it all--lol. It seems that the smaller diameter would require less breaking force for a given pressure and thus could be used at higher pressures without the breaking force-cracking force becoming exessive (PXA type equations). The longer stroke would allow more air to flow for a given pressure but because the diameter is smaller it would require the longer effective stroke at lower tank pressures to equal the flow of the larger type piston/seal (with less stroke). Do you follow what I am saying--I did not say it very well? The longer spring and body appear to have more stroke thus equalling out the smaller diameter required for higher pressures. If I am wrong so be it --- I just noticed those things and they are similar to what is done with various apparatus I have seen when similar changes in design requirments were made. Hey, you have a nice web site and thanks for your support of these wonderful old regulators and vintage diving---hey---I am marooned in KS with you! Came here from Az, if there was an ocean nearby it would be darn OK. Thanks again. Nemrod
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Post by seakrakken on Dec 16, 2004 10:05:23 GMT -8
I believe it could be because of the smaller size of the seats surface area. Less surface area the less applied force and less distorsion of the materials.
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Post by John C Ratliff on Dec 16, 2004 10:36:24 GMT -8
I've also looked at the two different seats, and see something else.
First, let me state that the failure I saw at 3000 psi on my Mistral seat was cause when the metal center area was pushed aside by the force upon this part of the seat. The impact point of the pin is on this concave metal part, that is "floating" on the top of the seat material. This led to the seat failure. I looked, and I don't think I still have that seat. The three I have appear to have undamaged seats, so I probably threw it away.
If you will look closely at the center portion of the Royal Mistral seat, it appears to be a part of the base metal of the seat itself, with a indented point. Basically, this would mean that the metal portion, rather than being a "top hat" floating on the plastic, is actually a part of the brass seat itself. More precise machining would be required for this to work, but by the time the Royal Mistral was produced, this was easily accomplished. The plastic (nylon or teflon??) seat itself appears to be a donut-shaped piece that goes around the center, rather than a circular piece.
I think this better explains the reason that the seat can stand the higher pressures. Of course, only the specific design drawing from La Spirotechnique, or someone deciding to sacrifice one, will positively identify the exact design change.
SeaRat
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Post by seakrakken on Dec 22, 2004 23:51:09 GMT -8
Experimentations on the Mistral I rescued from Ebay indicate that it is willing to function at 3000 PSI with no hesitation. Once I got to playing with it I decided that I would put a Conshelf yoke on it. All I had to do was chuck it up on a lathe at work and bore out the base of the yoke to 1". Then I got to thinking about something somebody mentioned about another Aqualung reg. They said that their reg had a venturi hose running down from the 1st stage down to the mouth piece. I then got some Tygone tubing of 5/16" ID and shoved that up onto the Venturi Nozzle that aims down the intake hose. I put the rest of the tubing to run down the inside of my intake hose. I then trimmed the length of the tubing to where it is just short of the wagon wheel on the mouth piece when everything is assembled. Putting it back on my 3000 PSI tank and doing a test breath or ten I immediately noticed a perceived reduction in Work of Breathing. As to whether or not there was really any reduction or not I am unable to tell because of a lack of instrumentation. Don't get me wrong I thought this Mistral already breathed better than my DA Aqua-Master. Now it feels comparable to my Conshelf XIVs I welcome any comments, criticisms or warnings anyone cares to help me out with.
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Post by nemrod on Dec 23, 2004 0:46:03 GMT -8
Installing a piece of tygon tubing on to the venturi is something that I have thought about but not yet tried since both my Mistrals are in a current state of disrepair soon to be remedied. It makes sense to me though it was my intention to only run the tygon about 6 inches into the hose. Nemrod
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Post by seakrakken on Dec 23, 2004 1:14:42 GMT -8
I ran mine as far up to the mouth piece as I could because, I wanted to reduce the friction/turbulence that the corrugations of the hose make.
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Post by Bryan on Dec 23, 2004 8:50:39 GMT -8
What many people complained about when using the DX Overpressure Breathing regulator was TOO much air. Some said it felt like it was being forced down their throat. So they did away with the green hose inside the intake hose that attached to the mouthpiece. It was then called the Stream-Air. The venturi did not perform all that well on that model so they changed it a bit and called it the Mistral. You will see many many DX Overpressure and Stream-Air regulators that have been updated and use Mistral venturi nozzles. Dan even has a picture on the site of one of the Stream-Air regulators with a Mistral sticker on it.
Your idea of putting the hose just outside the wagon wheels might be a good compromise ??
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Post by John C Ratliff on Dec 23, 2004 9:03:31 GMT -8
I may be one of the few people still using the DX Overpressure Breathing regulator (the original single-stage from USD). It has a metal mouthpiece, and the hose actually fits into another metal tubing on the mouthpiece. That metal tubing is attached inside the mouthpiece, and has three holes drilled in it that put the air directly into the diver's mouth.
The objections were the following:
--When water came into the hose, it got into this tubing and sprayed a fine mist into the diver's mouth. If the diver was ice diving (and they did that way back when too), these were little ice crystals coming out into the diver's mouth and throat.
--This was a very easy breathing regulator. Divers actually complained about the ease of breathing. It put out more air than any Mistral or DW regulator, because of the lack of hose restriction.
While I have not modified a Mistral with a tube, I have thought about it. Here's what I would do. I'd run the tubing actually through the "wagon wheel" by drilling out the wagon wheel to accomodate it. If I used a non-return valve on this side, I'd cut out the center and fit it over the hose. I would leave enought tubing to go to the opposite wagon wheel, and cut slits into the hose to fit it over the exhaust side. I would fill the hose with a glue, and glue it to the wagon wheel. But I would have cut out half the tubing longetudinally to make the same kind of opening I've seen in Dacor and Scubapro regulators, and face it directly down the mouthpiece.
I may be doing that with my Mistral, and doing one better. I'm looking to chest-mount my Mistral, so that the regulator is in the optimal position (the one Cousteau himself used in his last diving years).
This, to me, would be the ultimate Mistral design--chest-mounted and with the original hose-within-a-hose venturi concept.
SeaRat
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Post by seakrakken on Jan 3, 2005 17:33:49 GMT -8
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Post by nemrod on Jan 4, 2005 2:05:12 GMT -8
Seakraken, I tried your idea as I had mentioned that I had thought along similar lines. Well, I was not impressed. In fact, the Mistral was terrible with the hose inside a hose. I ran it two ways and repeated the test in a pool. I ran it about 3 inches into the hose---that did fairly well so I tried running the Tygon all the way to the wagon wheel valve. That was horrible--like sucking jello through a straw. I removed the contraptions and all was once again normal and my old Mistral behaved sweetly. Is that a 3000 psi Dacor aluminum tank?--to much pressure for the Mistral given my pool experiments it likes no more than 2500 and preferrably 2200. I could be wrong but way back in 66 when I took my NAUI course at age 12ish we used several double hose regs. The instructor said to take long slow deep breaths and long slow exhlations. The reason I assume is that while double hose regs have higher cracking effort than a single hose but once they are flowing the venturi effect from the aspirator in the Mistral helps to hold the diaphram down and the large mechanical advantage of compound levers helps also assuring a large and effortless flow of air. If you take the shorter normal breathing one often uses with a single hose then you are constantly fighting the larger cracking effort and not taking advantage of the venturi effect and resulting large flow of air. I could be wrong but that is what I think he said and it makes sense to me. Nemrod
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Post by Captain on Jan 4, 2005 13:38:06 GMT -8
I think that why the hose in a hose doesn't work that well is because it may reduce some of the vacuum signal from the venturi effect in the regulator case which normally helps to pull in the diaphrgam reducing suction effort. I tried the same thing on a Aquamaster that I soldered a 1 inch long piece of copper tube on one of the 3 holes in the nozzel and pointed it down in the hose but it breathed like a dog. I believe the nozzel has to be about an inch from the hose in order to get the vacuum effect in the case. If someone has a case they want to sacrafice they could drill a hole in it and attach a magnahellic gage or manometer and measure the pressure in the case both with and without the tube in a hose. How about it Bryan.
Tom
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Post by SeaRat on Jan 4, 2005 22:04:17 GMT -8
There is no need to drill a hole into the case to determine the effectiveness of the venturi with and without the hose. As I stated above, I have the DX Overpressure Breathing regulator, and it has the hose-within-the-hose venturi. It works very well. The hose extends into the mouthpiece, where it attaches to another metal tube that parallels the mouthpiece tube (which alse is metal, with a "T" for the mouthpiece. The metal tube is crimped just on the far side of the mouthpiece's opening, and has three holes drilled into the tube to pipe the venturi air directly into the diver's mouth.
Seakrakken, I think that the problem with the concept you have is not the hose, but the type of hose. I think you have a hose that collapses in certain positions, and therefore gives you the characteristics of "sucking jello through a straw." If it works in some positions and not in others, look at the inside hose and see whether it can collapse. If it does, you've solved the problem.
As stated above, there are advantages to having the hose-within-a-hose concept. The main one other than easy breathing is that it is a quiet regulator. It is the regulator I like to use to take marco photos, as it really isolates the diver from the air noises typical of most scuba regulators (double and single-hose).
John
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