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Post by SeaRat on Jan 23, 2019 20:10:43 GMT -8
I just picked up a sweeeet Navy Unit III on the bait. It looks good, but I haven't taken it apart yet, due to overwhelming #s of projects I care about. I got it because I'm thinking about a doublehose mod that would feature this 1st stage. Prolly won't get to it for awhile, if ever. Pics to follow. Ever thought of creating a second stage, double hose regulator that is independent of the first stage. This is what was done by Aqualung when they developed the New Mistral:  With an independent second stage, the regulator can be located at more ideal positions, rather than being clamped to a manifold or valve. The second stage could be located lower on the back between two tanks, or chest-mounted, like the Cousteau divers.  John |
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Post by technidiver on Jan 24, 2019 12:43:13 GMT -8
I just picked up a sweeeet Navy Unit III on the bait. It looks good, but I haven't taken it apart yet, due to overwhelming #s of projects I care about. I got it because I'm thinking about a doublehose mod that would feature this 1st stage. Prolly won't get to it for awhile, if ever. Pics to follow. Ever thought of creating a second stage, double hose regulator that is independent of the first stage. This is what was done by Aqualung when they developed the New Mistral: With an independent second stage, the regulator can be located at more ideal positions, rather than being clamped to a manifold or valve. The second stage could be located lower on the back between two tanks, or chest-mounted, like the Cousteau divers. John I didn't realize that the New Mistral could be chest mounted! All you'd have to do would be to create a rig to keep it on your chest. Phil, would you consider doing a chest mount mod? TD |
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Post by vance on Jan 24, 2019 18:27:06 GMT -8
I have an odd Russian doublehose regulator (AVM-3) that is a second stage reg. It needs a remote 1st stage, and is a great candidate for a chest mount. I have been thinking about this, and might do it someday. All I'd need is a harness. The first stage and connecting hose could be anything, but I'd use a Nemrod 1st. It has an ORPV option, so it'd be safe if the Russky unit is an upstream reg. I don't remember, but I think it is. I have a lot of project irons in the fire, so who knows if I'll ever get to it? This is it, showing the stack of adapters I had to use to get it to connect to a BCD QC hose. It can be simplified: 
It is a pretty good breather.  The cap on the angled fitting is also an LP tap which would be more convenient for a hose take off. |
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Post by cnotthoff on Feb 1, 2019 17:14:45 GMT -8
Phil, I know you just used that stack of fittings to prove a concept. Please don't try to dive it that way. The BC quick connect is way too small to flow enough air to breath, particularly at depth. That is why Scubapro's Air 2, Aqualung's Airsource and other Alternate Inflators use a larger QD fitting. If you drill out the flared end of this fitting, it will screw onto a standard 2nd stage hose swivel. I forget the size drill, but you can figure it out. That gets you to a 1/4 met. www.keeneeng.com/mm5/merchant.mvc?Screen=PROD&Product_Code=A5BGood Dives, Charlie |
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Post by SeaRat on Feb 1, 2019 20:03:03 GMT -8
I had a center section of a Sherwood manifold modified to accept the LP hose fitting, with the idea of using it with a Mistral regulator for chest-mounting. It did not work. I finally figures out that the routing of air going through that center section was insufficient to maintain a good flow in the Mistral. When I put a Royal Aquamaster on it, the flow was better, but still not satisfactory, so I upped the interstage pressure on the first stage and then dived it. I got adequate air flow, but I was also diving my Nautilus CVS BC, and had a malfunction of the weight retention lever. I had to hold the weights with one hand, and try to manipulate the lever/pin system with the other hand...unsuccessfully, I might add. So I finally, after about five minutes of this, got to a place I knew and let the weights go. I had a head-down controlled buoyant ascent (after dumping 16 pounds of weight), surfaced, and got out of the water. I returned with a different Scuba system and recovered the weights (and my GoPro camera--yes, I have video somewhere of that escapade that I have not released).
The point of this post is that the single stage regulators (and I tried a Healthways Gold Label too) don't work well on a second stage at interstage pressures 120-145 psig). To successfully combine two different regulator systems, you may need to substantially up the interstage pressure.
You may have seen Jacque Cousteau using a rather unique triple tank system, with a chest-mounted Mistral regulator. I have this feeling that he was either using an interstage pressure of 500-750 psi, or actually not using a regulator first stage at all, and the line to the Mistral was a HP line. This was probably his last dive before the docs said, "No more diving!" After a lifetime of smoking caused lung disease (nothing but speculation on my part, but in one of his last films he did say that "My diving days are over," if my memory is correct).
John
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Post by vance on Feb 2, 2019 10:51:06 GMT -8
Phil, I know you just used that stack of fittings to prove a concept. Please don't try to dive it that way. The BC quick connect is way too small to flow enough air to breath, particularly at depth. That is why Scubapro's Air 2, Aqualung's Airsource and other Alternate Inflators use a larger QD fitting. If you drill out the flared end of this fitting, it will screw onto a standard 2nd stage hose swivel. I forget the size drill, but you can figure it out. That gets you to a 1/4 met. www.keeneeng.com/mm5/merchant.mvc?Screen=PROD&Product_Code=A5BGood Dives, Charlie Thanks, Charlie and John for your suggestions and experiences. There's more than a couple of things about this setup that I have questions/concerns/comments about.
John, you might want to move all of this to a new thread, since it has nothing to do with tilt valves..... But others have mentioned chest mount projects and it might be a fun thread. First is that the regulator (the AVM-3) is a second stage only. It is not a singlestage regulator, and requires a remote first stage. I have never tried to make a remote setup with a singlestage like a Mistral, so I don't know what its air volume requirements would be 2 feet away from the tank valve. But one would think that a AVM-3 should work fine with no restrictions less than the openings in an LP hose meant for any 2nd stage. The stack is indeed unwieldy. I thought it would be convenient to have the QC on it, but quickly discovered it isn't. You are right, the stack of fittings is simply a crude attempt to adapt metric threads to 3/8"UNF using some fittings I had on hand. Unfortunately, this required also adding 1/4" NPT to the mix. I will make an adapter going directly from M16 (or whatever) to 3/8".
I did notice a lack of ooomph (engineering term) in the breathing quality of the AVM-3 with the stack. Also, there was considerable diaphragm flutter. |
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Post by SeaRat on Feb 2, 2019 12:06:55 GMT -8
Done.
John
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Post by luis on Feb 2, 2019 14:23:19 GMT -8
If you ever notice how a DH becomes a positive pressure breather when you get on your back, that is basically what chest mounted does to a DH. It is still a demand valve, it is just biased to work in a positive pressure mode. You actually have to hold your mouthpiece with your teeth. It would work with a full-face-mask if you had to dive in contaminated water. One big disadvantage of chest mounted is that now you can end up with a lot of bubbles in your face. If you do a search for chest mounted you will find a number of related threads. Here are a couple of links. From 2009: www.vintagedoublehose.com/forum/viewtopic.php?f=4&t=3773&hilit=chest+chest+mountFrom 2012: vintagedoublehose.com/forum/viewtopic.php?f=4&t=6513&p=56100#p56100From 2015: vintagedoublehose.com/forum/viewtopic.php?f=4&t=8042&p=65950&hilit=chest+mounted#p65950During Sand Dog IV (in 2007) I tested a new Mistral on a chest mounted configuration. Since the first and second stage can be easily separated, it made it very easy to try it in this configuration. The cracking effort was biased towards a positive pressure breather, but that did not resolve the lack of any venturi assistance.  
This was in June 24, 2012.
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Post by vance on Feb 2, 2019 16:57:34 GMT -8
Thanks for moving/starting this thread, John! Sorry for the hijack, but it wasn't just me! |
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Post by vance on Feb 2, 2019 17:05:15 GMT -8
What is the second reg's provenance? It looks sorta-kina like a DA minus yoke in FX cans? But???
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Post by luis on Feb 2, 2019 17:53:16 GMT -8
It is a DA body, but a new HPR second stage and there is no first stage.
I also added an in line shut-off valve. I had made a prototype DSV at the time, but I was not using it.
You can see details in the link to the 2012 thread.
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Post by vance on Feb 2, 2019 20:41:57 GMT -8
OK, very interesting. I should have looked at the links b4 asking questions. The pic above looks like a USD first stage but blank. In the 2012 post I can see the obvious plug.
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Post by Fibonacci on Feb 3, 2019 17:11:05 GMT -8
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Post by SeaRat on Feb 18, 2019 20:19:16 GMT -8
After finally disclosing the dive I made with my chest-mounted Royal Mistral, I thought I would put some photos up of the setup.  I used my Dacor Nautilus as a basis for my experiment, thinking that it would be better than my Para-Sea BC, which was a mistake (see my post above). But you can see that I have two hoses coming off my Dacor Pacer regulator, going to a modified Sherwood valve to accept LP hoses.  This is looking down on the chest-mounted Royal Aquamaster, with the valve in place.  And this is what the entire setup looked like, ready to dive. John |
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Post by technidiver on Feb 18, 2019 20:26:34 GMT -8
Interesting setup John, did you eventually figure out the LP problem you mentioned?
TD
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