Old vs. New Mistral

[kgehring]

I am new to the old and I have the new Aqua-lung Mistral. I dove it for the first time a month ago wit Rob, Allan, Greg, & the GREAT BROXTON CHUCK.
After the dive I asked Chuck if he would service one of my many old 2 hosers. He said Yes!. I gave him my 1960 Mistral and he went thru it and made it dive worthy. I also had to have the Famous Broxton Chock Banjo fitting. Well, I just got out of the local mud hole and the 1960 Mistral breathes and performs much better than the new Aqua-lung Mistral.
KUDOS to the GREAT BROXTON CHUCK!!!!!!!!

[nemrod]

Of course the real deal, made out of metal, meant to last a lifetime original Mistral out performs the plastic POC. Tell you another thing, either of my souped up Royals will walk all over that plastic POC "new" Mistral and do some kinda obscene wiggly football goal dance on top of it.--lol. James

[SeaRat]

'Sorry guys, but I'm not quite buying that the ol' Mistral will outperform the New Mistral. Maybe if you said that at 500 psi, the ol' Mistral performs as well as..., but it would be difficult to convince me that a balanced, two-stage regulator will be outperformed by a single-stage upstream regulator at full tank pressure. I just don't think that will happen.

After thinking it over, you may want to re-check your tank position, and see whether it is set up too high on your back. That would leave the impression of hard breathing, unrelated to actual regulator performance.

I've breathed off the New Mistral, and I would put it, at factory settings, at just under what my AMF Trieste II can do performance-wise. If some of us were to tinker with it a bit, who knows. Maybe I should buy it to find out.

John

[VintageDiverMN]

Who cares how the new Mistral breathes. I thought we are interested in vintage diving equipment, I know I am. Frans

[Ron Hearn]

Hi

I agree with both of you, The old mistrals hold a historical value and a certain amount excitement and enjoyment when used by collectors like us. The new mistrals is just a modern re engineered first stage regulator with a redirected exhaust and intake and naturaly they would breath better as they do not have that large diaphram to move and duck bill to blow out of. I'm sticking to my CG45.

Ron

[kgehring]

New Mistral performance problem... I removed a lp hose and there was moisture in the first stage. My best guess is that the check valve in the second stage did not seal totally and water entered the first stage. I know what you are thinking... he rinsed it with the dust cover off. Well, It was on.
I checked the diaphram and the check valves. All appear to be ok. I will dive it on sunday and see what happens.

Old Mistral on a full tank diving in 20 ft. breathes easier than the new. I will try both again and see if the new will stay dry.

[luis]

"...naturaly they would breath better as they do not have that large diaphragm to move..."

Actually the large diaphragm is what helps old two hose regulators breath easier.
The force produced by the diagram (to move the horse shoe lever) is equal to the pressure differential times the area of the diaphragm. Therefore, the larger the area the less amount of pressure drop/ suction required to move the lever.

New regulators with small diaphragms require fine tuning and other mechanical advantages (pilot valves, etc.) that was not as critical with a big diaphragm. The diaphragm gave you the mechanical advantage. The original Mistral relied on that size diaphragm.

[nemrod]

I agree with Luis, the large diaphram is a positive not a negative. It is a force multiplier. It would be great if it were made of super flexible, springy and lightweight silicone but a good condition neoprene diaphram treated with silicone seems plenty flexilble and works decently enough.

I think there is always the latent belief that because something is newer it is better, often it is but in this case I fear Aqualung just grabbed some stuff from the parts bin and whipped out a funky double hoser that despite being "modern" is not really a truely congealed design and appears full of compromises despite having some clever features as well. What it has that the Royals do not is LP and HP ports and unlike the old Mistral it is not limited to 2200ish psi.
I would like to see a more vintage styled modern regulator along the lines of the Voit Trieste using a servo valve to keep the main diaphram small. All silicone duckbills, diaphrams and mushroom valves would also help greatly. James

[John C Ratliff]

Concerning the water in the first stage situation, there is only two ways that can happen. One is the dust cover (but that did not happen), and the other is that there was water in the hose that got by the mouthpiece check valve into the normally dry area of the second stage. Then, to get into the first stage, the LP valve had to open with water inside. That means that a vacuum of some sort had to be created on that side. This could happen if suction was applied (someone breathed on the system without tank pressure) to create a vacuum, and there was water inside too. If you want to prevent that, then after rinsing the regulator, do not breath on it without hooking it up to the tank.

On the question about the diaphragm, the larger size does help, as does flexibility. My AMF Trieste II is my best breathing regulator, but to get it there I had to create a "new" diaphragm for it. I did this by replacing the Trieste's diaphragm with a home-made one made of rubberized fabric. The original diaphragm had a molded-in inflexibility which caused about a 1.5 inch water pressure increase in the inhalation resistance of the regulator. I cut a new diaphragm out of the neoprene-impregnated fabric, and glued the metal disc onto the center surface with shoe-goo. I then set it on the sealing surface after preparing that surface (first with a layer of grease and then with shoe-goo glue), put another layer of shoe-goo on the top surface, prepared the sealing surface of the bottom box with grease and set it on the regulator. I then put the clamp ring on the reg, without tightening it, and let it set for three days to cure. Then I pulled it apart, cleaned all the surfaces, and let it cure another week (if I did not do that, then the glue would give off vapors that would not be pleasant to breathe). Now, with another modification to the venturi of the regulator, I have a regulator with a breathing resistance measured at about 1/2 inch of water pressure.

So when I say that I figure the performance of the New Mistral at just under my AMF Trieste II, it is with these modifications. I cannot tell right now much about the New Mistral as I have not bought one yet, or used it. So my estimates may be a bit off. But the old Mistral on a full tank will pull somewhere around 2 inches of water pressure suction effort (it goes down to about half an inch at 500 psi).

The Snark III also has a breaking effort of about 1/2 inch if you take the non-return valve out of the mouthpiece, as it has the same mechanism of the old Mistral, but on a two-stage regulator. This regulator has two design problems, one being the hose/mouthpiece system with too small of diameter mouthpiece openings and non-return valves, and a venturi system that actually pushes air up into the LP diaphragm to decrease the venturi effect (thus increasing breathing effort during the breathing cycle).

My other, very good performing regulator is my Sportsways Hydro-Twin. This regulator is the equivalent of the USD Mentor, as it has both LP and HP outlets on the regulator body, and a very good, balanced first stage and downstream second stage. It has a larger LP diaphragm than the USD Royal Aquamaster, and one that is both flexible and tough (rubberized fabric). But it had an ill-designed hose/mouthpiece system. I use it with a USD hose/mouthpiece system, and it performs equivalent to my AMF Trieste II.

What I mean by good performance of either of these regulators is that once the inhalation is initiated, the regulator blows air and you must exhale to stop flow. If I begin an inhalation on either of these regulators, and take my mouth away from the mouthpiece, they will continue to flow. This is what I consider a good-performing double hose regulator.

Concerning the old Mistral's performance, I have a report that shows this regulator (La Spiro's version with Nemrod Snark III hoses) pulled 10 cm of water suction effort for breaking at 190 bar (2756 psi), and only about 3 cm of water at 40 bar (580 psi). ("An Attempt to Link Objective and Subjective Performance of Sprort Divers' Regulators," b R. J. Nyman et al, Science Diving International, Proceedings of the 3rd Scientific Symposium of C.M.A.S., edited by N. C. Flemming, published by B.S.A.C., 1973.)

John

[Gomez]

Like old Harold Hill said, " you can talk, you can talk, you can talk all you want, you can talk talk talk talk, bicker bicker bicker ;D... BUT he dosent know the territory" Take a lesson. This isnt worth wasting space about. Your using classic gear here. Gear that was made right the first time. Be happy your "vintage divers" and have the gear to have your fun with. This modern stuff will never be classic, or anything else but forgotten 40 years from now.

[Broxton Carol]

I have been reading this line, and ANY of the old regs we use can be fine tuned for optimum performance. The mistral I have is a pleasure to use. My ROYAL gives all the air effortlessly, and thats set to factory specs. My old broxtons and DA's all work great WITHIN their design limits. If you own say a nice 63 chevy, and really tune it up, really carefully, and maybe tweek the mix, or timing a hair, you might get a little better something for all your loving care, as RUSKIN said "that intangible something" but for me, nobody else cares. I just roll down the road, and let them get out of my way. Same with my old gear, if somebody likes it fine, if another guy dosent rave about it, I could care less. I like it. Have you ever had a stranger come up and ask how many inches it pulls? Who cares. Get on with it, and start having fun. I once saw a guy who had drilled out his K valve so it would supposedly shoot more air into the reg. Also I was rebuilding an aquamaster for a guy, and found some moron had drilled out the seat holder with big holes to supposedly let more air in................ Wouldnt it make more sense to drill out the seat oraface also? And on and on and on and on....................

[kgehring]

I appreciate the good info on the operation of the regs. I am new to vintage gear and would like to thank everyone for their knowledge and input. I guess some people do not tolerate anything "new".

[SeaRat]

I bought my AMF Trieste II regulator new, and was disappointed when it did not perform as well as my Mistral in 1973. I also bought a Dacor Dial-a-Breath used, and upgraded it to an R-4 by buying the parts and putting it together, and was disappointed that it did not breath much better. So since about 1975 I've been trying to figure out the design defects in some of these two hose regs, and fixing them. Each one has its own good points, and poor ones too. Old is not necessarily better, as I've discussed above with my three favorite regs, the AMF Voit Trieste II, the Snark III and the Sportsways Hydro-Twin. My USD DA Aquamaster needs a rebuild, and at the same time I'll be rebuilding my Bronxton DA Aqualung to see whether Chuck's contention that it is adequate is correct (I never got that reg to work to my satisfaction since I've had it, and it was rebuilt in the 1970s). But I suspect even the New Mistral has some interesting characteristics about it. This is a "vintage" site, but realize that to me some of these regs are not vintage, as I bought them "new." But that is now making...me...(can I say it...)..."vintage."

I will say that it is humerous that Cousteau's divers took the LaSpiro Mistral to a depth of 365 feet in the Conshelf 2 program in about 1963, and were very comfortable with it there. It does show that this regulator has withstood the "test of time," and continues to be a very nice regulator to use as a standard.

John

[nemrod]

kgehring, hey, welcome to the group, sincerely. Please realize many of us and now you as well are passionate--lol---about our old junk. Agsin, welcome and please stay and give future reports on anything you like including the new Mistral! James

[Broxton Carol]

Hi John: When they were down there they were listnin to Mel Gadson singin "comin' down with love" with Dick Biondi on WLS channel 89 Chicago. Came in good through the left hose with a little antennae on the tank band!!!!! I got Royal here to overhaul tonight and Ill do that while watching "Greta" and her way out news. Real exciting stuff. Later, Chucko