Label Question

[kgehring]

On the Aqua-Lung Stream Air Regulator thare are some with yellow Mistral label above. Was this a transition between years models and are there differences in the internal parts. Stream Air or Mistral?

[jrvance]

this means it was converted to a mistral

[admin]

The only difference between the Stream Air and the Mistral is the length of the nozzle; the Stream Air is short and the Mistral has the longer one (about 3/4 inch). The longer nozzle meant a stronger venturi and better breathing. As for the "Mistral" decal above the Stream Air label, it's possible that they all had it when new but most fell off over the years. We've also seen the "Mistral" decal on an "Overpressure Breathing" model and maybe even a yellow labeled Mistral. But these could have been an oddity.
Another interesting fact- the early Jet Airs with the raised letters cast right into the plastic had the letters painted yellow when new. But very few have the yellow left on the label.
Dan

[SeaRat]

Actually, I'm going to side with John Vance on this one. I think the yellow "Mistral" labels on the "Stream Air" regulators did undergo the conversion, as did the "Overpressure Breathing" regulators with the "Mistral" label.

Fred Roberts, in Basic Scuba stated that both of these regulators could be converted to Mistrals with a conversion of the venturi nozzle. For the Stream Air, the not only was the nozzle changed, but the positioning was also changed.

The "Stream Air' nozzle was actually providing more venturi action than the "Mistral" nozzles. The "Stream Air" nozzle was simply a stainless screw with a hole in it. But it was not pointed directly down the intake hose, as this would create too much venturi effect.

The "Mistral" nozzle was more sophisticated, with a bit smaller hole, one which increased the velosity of the air, but also with two holes allowing air into the case. This dampened the venturi effect to some effect, allowing a smoother breathing action. But because of the holes, the nozzle had to be lengthened.

The upgrade of the Stream Air to Mistral involved both replacing the nozzle, and re-orienting the body so the Mistral oriface pointed directly down the intake hose.

The "Overpressure Breathing" regulator had a very unique venturi, with a nozzle/interior hose that led to the mouthpiece, where the air was ejected through several holes directly into the diver's mouth. To upgrade this regulator, the hose/mouthpiece system had to be changed to the "Kleer-EZ" hose/mouthpiece system. The original "Overpressure Breathing" regulator had short hoses (which were indestructable--I still have mine) with a metal mouthpiece built to take the interior hose into a metal tube with holes drilled to re-direct the air into the diver's mouth. A modified "Overpressure Breathing" regulator to the Mistral design has no hose-within-a-hose system, which is what the original has.

Karl (I hope), you can check this by opening the regulator and seeing if it has a "Mistral" orifice, which is about 1.5 cm long, and had to side holes in it. The "Stream Air" had a simple screw with a hole in it.

Dan, I think John Vance got this one right.

John

[jrvance]

thanks for agreeing ;D ;D

i am not a vintage person, and you all dive this stuff

but i remember reading somewhere about a converted mistral and thats the only reason i say this

[admin]

Hi John;
I agree with what you wrote on the principles of operation on both the Stream Air and Mistral.
I have a hard time believing that US Divers would have modified the Stream Air or Overpressure Breathing regulator after they were sold to a customer. I don't think they did "recalls" in the 1950's and 60's and this would lead the customer to believe that they bought an inferior regulator. I've been looking at my US Divers catalogs, back to 1956. The photo of the Stream Air doesn't show the Mistral decal, nor does it show in the 1957 catalog. But in 1958, when the yellow labeled Mistral was first sold, the Mistral decal appears for the first time in the catalog and it's shown on the Mistral all the way up to 1962. I have around 10 Mistrals, I've rebuilt at least 35 customer ones and I've seen around 30 others, and yet I've never seen the Mistral decal above the yellow Mistral ID plate. So I have a theory that perhaps US Divers came up with the new nozzle concept before they wanted to do away with the Stream Air (maybe they had lots of Stream Air labels left) and they modified them at the factory and designated this with the decal. I was able to locate one of my Stream Airs with the Mistral decal and it DOES have the Mistral nozzle but not the second pin alignment hole in the box (for changing the angle of the nozzle) which means that it wasn't a Stream Air top box. But I have seen top boxes with aligning holes just several degrees apart. We can verify this theory about factory conversion if all the Stream Air owners can give us their serial numbers and let us know if the reg has the Mistral nozzle or the Stream Air one. If they modified at the factory, the higher serial numbers will be the converted ones and the lower serials will be the original Stream Airs. Am I making any sense here?
Dan

[jrvance]

because all they would have to do is replace a drop in part

what i think is the dive shop replaced the orifice and add the sticker

[JES]

Dan,

Let me start by saying that I won't even begin to pretend to know the correct answer.

I do however agree with your rational because like you I don't believe that USD (or any other scuba company) would go out of their way to modify their regulators or perform recalls.

[jrvance]

what im saying is people would pay for the upgrade

[kgehring]

Dan, Would you like me to ship it to you for disection? I can send my Stream Air and Stream Air with Mistral Logo decal. They are both wall hangers. I am not ready to restore them to working order at this time.

[JES]

jrvance said:

what im saying is people would pay for the upgrade

That could be possible.

However, I'm still thinking like Dan said "perhaps US Divers came up with the new nozzle concept before they wanted to do away with the Stream Air (maybe they had lots of Stream Air labels left) and they modified them at the factory and designated this with the decal.".

Dan's logic would follow a typical "for-profit" business model.

[jrvance]

yay capitalism

[Seahuntjerry]

Hi,
In some early Skin diver magazines there were ads to convert Overpressure breathing to Mistral orifices.
I have an original yellow label overpressure breathing regulator with the yellow decal(Mistral) with The Mistral long orifice.
Us divers also showed the Mistral in some of the 60's catalogs and yu could clearly see the Red Stream air nameplate with the Yellow Mistral decal on them
I assume Us divers just used those nameplates and added M istral decal to them.
Jerry

[jrvance]

i wonder how i knew that

[SeaRat]

According to Fred Roberts in Basic Scuba, those modifications to the oriface were apparently fairly common. It was probable done at the dive shops, but the book does state,

The orifice of the Mistral differs from the orifice of the DW predecessor in a manner which greatly improves performance. Those divers converting a DX to a DW regulator take note. To understand the reason for the Mistral orifice let us go back to the first venturi Aqua-Lung employing overpressure breathing, the DX...

I think a lot of people changed the orifice on these regulators. But I also like Dan's idea that USD changed the orifice and not the nameplate, and so put the label on it too. My question would be whether the orifice and the label were possibly shipped out as an upgrade kit for these regulators? If there is a bill of materials (BOM) at USD for the Mistrals and for upgrade kits, perhaps this could shed some light on the subject.

John