Vintage Double Hose

Who has rebuilt one? Are there any specific tricks to getting one to work?

I already searched. Many of the old threads are gone from pre-2008 and many of the old photobucket pictures have been erased by people who shared them previously. Can the seats be refinished? For those of you who have gotten them to work, how have you done so?

I have no clue Ron, but I do have an exploded view in one of my manuals if that would be any help.

I spent hours and hours trying to get the HP seat to seal on two different USD US Royal Mistrals. Tom helped me with one and we tried several different compounds of nylon and various other material trying to make a reliable replacement seat to no avail. I won't service them for this reason. Last I heard Karl has one that was working ok but thats the only one in recent memory. Great idea....great looking label but there is a reason they only made them two years and the HP seat might be it.

Is it a design flaw or something? Poor orifice design or seat material selection?


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Seat material combined with size of the orifice with the spring selection...Luis would be the most qualified to answer that.

Yeah, Luis did do Project Unicorn, so his input would be great.

I wonder if there is a solution. Obviously I am not the guy to design it, but I would help back a solution with capital and be willing to test dive it. You know I prefer to be a money where my mouth is kind of a diver.


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It would not be a problem for the company that made HP seats to remedy the material problem at they have done several times with the Royal/Conshelf/Titan seat. And without a doubt USD could have easily solved minor dimension change to the other parts if they were the cause.....But WHY did they drop it after only two years if it could have been fixed easily. I wonder if the lack of HP/LP ports was an issue? They could have incorporated a HP port like they did on the La Spirotechnique version but no way for the LP. Capitol investment vis return I'm guessing.

I'm conjecturing here, but the regulator first appears in the 1965 USD catalog. It is priced in between the DW Mistral and the DA Aqua Master. The Royal Master already debuted in 1964, and it was already balanced. I wonder if it simply didn't fill a role for them. For slightly less, you could get a DW Mistral, with a record for reliability and ease of service. For slightly more, you could get a DAAM or RM, and the RM was a balanced two stage regulator. Maybe the juice was not worth the squeeze?

No other American manufacturer made a balanced single stage to my knowledge. Is it more difficult to design or less desirable for customers?

Either way, if we could figure out how to solve the problem then I am willing to support it with my money and time. Is anyone interested in resurrecting the only non-functional USD double hose besides me?

Also, Herman if you can post or email the Royal Mistral schematics and stuff to me, then I will hang it on the site permanently for everyone to use.



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Another issue now is how many are out there and available. I would be super interested in working on making one work and putting money towards something - but there are so few and they go for so much one has remained out of my reach.

Certainly. I spent the time and money on getting my DX working as originally sold just to be able to dive it. I incurred the entire cost of that myself. Still, the more people the cheaper it gets.


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The soft cone design on a hard square edge orifice seat is not a realible geometry without very precise tolerances. It is basically not a very good design.

Other companies (Poseidon first stages and Mares Ruby 1st stage) have tried the opposite (a hard cone with soft orifice) with better succes, but still not huge reliabilty. A hard cone on a soft seat is more reliable, but I still don’t considered it ideal.

A flat seat is highly predictable against a the flat plane formed at the top edge of a volcano orifice.

I personally would not waste my time on this regulator. It is just not as reliable valve seat geometry (nothing to do with the balance). Better material selection could help, but the geometry makes it an uphill battle.

I can write a full explanation with a lot more details (it would be a long post), but I don’t have the time right now. Maybe after I am done helping Bryan with the new DSV.

Thanks Luis, I know that you are very busy so I appreciate your knowledge


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Well, if I end up with this one maybe I will sell it. I don't keep scuba gear that doesn't work.


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slonda828 wrote:Certainly. I spent the time and money on getting my DX working as originally sold just to be able to dive it. I incurred the entire cost of that myself. Still, the more people the cheaper it gets.

I agree there. I put countless hours and more money then I care to think about (and hope my wife never finds out about) into my first DX to restore it to original function. It was a lot of fun and entertaining to chase parts, make parts, work with others here etc... to get it to work. Certainly not my favorite to dive with but rewarding nonetheless. I then bought a nice original example of one, and its just not as cool to me. That's why getting one of these to work, if not ideal, would be interesting to see.....