More aggressive venturi action on a RAM/DAAM?

[John C. Ratliff]

I have only a few minutes to write here, but I have made significant modifications to the Trieste II nozzle and openings, and they make it absolutely the best-breathing double hose I have. I have had a USD DA Aquamaster and now a Mossback Mk 3, but this beats them. The Massback Mk 3 is great, but has the exact same nozzle as the Aquamaster/RAM/Phoenix. It provides all the air I need, but does not have the venturi of the Trieste II with modifications. You can see that one opening on this nozzle was closed (the rear one), and one on the side slightly enlarged. The other modification was to take a baffle plate from a Healthways SCUBA Deluxe and glue it in the USD/Voit curved mouthpiece.

I have made several other changes I don't have time right now to discuss.

Now, the reason I cannot write much more is that I need to order some bread from the broad store (Great Harvest) and go out to dive. It's a glorious and beautiful, sunny day here in Portland.

SeaRat

 

[herman]

Ahh bleep Luis, you are right... I had the 2 mixed up, it has been a good while since I was playing around with making the seat holders...I have dies for both.

 

[John C. Ratliff]

Well, what I put up there was thinking that Herman had gotten a Trieste. Then I re-read his post and it was an MR-12 that he got, so this won't help him much.

The main principal on the Trieste II mods is that the main hole was already very large. It had another on the other side of the same size (I haven't taken it apart to look and see dimensions for a while). It also had two holes on each side, which were much smaller. The dive shop in Vancouver BC made the modifications, as they had been selling Trieste II regs for a long time and had a stockpile of them. They blocked off the entire back hole, and then slightly enlarged one of the side holes. This put a majority of the air going down the intake hose, as opposed to less than half in the original design.

There were two other modifications that I made, one of which was critical for the Trieste II performance; I replaced the main LP diaphragm. The original diaphragm was quite stiff, and required about 1.5 inches of suction pressure to depress it independent of the lever system. This was a home-made diaphragm, as others were not available. I have photos below of the coated nylon fabric diaphragm I made using the top and bottom boxes as forms and Shoe Goo as the sealing surface (after coating the two metal parts on the boxes with silicone grease). I made also glued the metal plate onto the diaphragm. This mimics the MR-12 rubber-coated nylon diaphragm.

I dove my Trieste II for about 45 minutes in the Clackamas River today, with great results. It is a fine regulator. I have an LP inflator, a MR-12 octopus, and a gauge console on this regulator too.

The main thing you can take from this is that if you want to open up the orifice into the intake hose of the AM/RAM/Phoenix/Mossback Mk 3, you need to close something else off. But really, what I've found with my Mossback Mk 3 is that it is a fine regulator the way it is; same with the Aquamaster. The venturi is pretty well balanced. My musings about a Mistral orifice on is were just that, and I'll probably never act on that. I have another idea I am pursuing, and if it is successful (or even if it is not) I'll report my results.

 

[elmer fudd]

I was thinking about this today, and it seems to me that the easiest way to block or constrict the other two ports would be to make a little sleeve that drops into the seat holder. All it would have to be is a thin walled brass tube with holes bored out, (or not bored out), for the three ports. This would also allow for correcting holes that ended up being overbored.

 

[John C. Ratliff]

Elmer,

You could do that, but that would be trial-and-error. It may be better to do some calculations to see what effect you wanted. Louis is pretty familiar with the engineering aspect, and really when you are dealing with this it is better to do the engineering on paper first, then the modification. You could start by looking at the Mistral nozzle, hole diameters, the concept of the venturi (see Fred Roberts' book, in the beginning chapters), and see what the Mistral is doing differently from the Aquamaster for the venturi. I also had my Mistral in the water today, and although the initial breathing effort was greater than the Trieste, once going it was effortless.

SeaRat

 

[herman]

Well, what I put up there was thinking that Herman had gotten a Trieste. Then I re-read his post and it was an MR-12 that he got, so this won't help him much.

.

That assumes it stays a MR-12.
I love the photos and mods to any reg so please keep them coming.

 

[John C. Ratliff]

That assumes it stays a MR-12.
I love the photos and mods to any reg so please keep them coming.

Unfortunately, it is the Titan that can be converted to the Trieste, and not the MR12. I'll post some photos later.

John

 

[herman]

Ya know John, this in just not my thread....I know it's the Titan ( I have both) not the MR-12...the fumes of cutting oil may be getting to me.

 

[elmer fudd]

Being the OP, I don't mind thread drift at all. As far as I'm concerned if we're on the vintage forum and talking about vintage diving then everything is fine.