DH Regulator independent of Manifold--A Failed Experiment

[SeaRat]

I have envisioned using a system where I had independent doubles (no connecting manifold) feeding a double hose regulator off two first stages. So last Spring I asked DiverDon to make me a center manifold that would connect two LP hoses coming off a first stage, and sent him a Sherwood center manifold for the experiment. Well, he did a great job, and I was set to do some in-water work this summer on a new system, one which would detach the double hose single stage regulator from the manifold and allow a lower back mounting or even a chest mounting. This would get away from the problem of the valve placement being high off the diver's back, and causing a lot of water pressure between the regulator and the center of the diver's lungs. I figured I would gain at least a couple of inches water pressure by this placement. So I set up the experiment in my garage, and tried it out. Here's what it looked like:


I used two different tanks in light of setting it up for diving just to try it out, and balanced the two regulator first stages at about 140-160 psig. I used my SCUBA Gold Label Hybrid regulator, and tried it out. Here's what it looked like closer up:


Note the tie-in to the two LP lines for the double hose regulator.


There was no leaking, and the setup looked good. Initially I was going to use my MR-12 on this, but the second stage would not take the increase in pressure (leaked badly--it's IP is around 125 psig), so I used the Dacor Olympic regulator and first stage. I needed a second stage on the system to provide a downstream valve as an overpressure relief valve.

Well, then I tried breathing off the system, and it did not breath well. It was like there was a restrictor orifice on it. So I put on a USD Mistral instead, again at about 145 psig. It too had the same problem. Well, then I put my Dacor Clipper on it, and the breathing was okay at first, but a heavy breath would over-breath it too. My Mossback Mk 3 had a similar problem. So somewhere there is a design defect I could not envision that prevents this from working.

Don, I told you I'd finally get around to publishing this on the website. Right now, I've tabled the idea for a while. I figure that I need ~500 psig on the LP hoses to make it work, but don't have a good answer about an overpressure relief valve, and the LP lines are not meant to handle that kind of pressure.

This brings me to another aspect of this; I was trying to duplicate the system that JY Cousteau used for some of his last dives. But now I'm pretty well convinced because he is using a Royal Mistral from La Spiro that the lines they were using were high pressure lines.

John

[diverdon]

Interesting experiment John, I hope you're able to find a workable solution. I keep meaning to doff my double hose while in the pool to see how breathing resistance changes when the regulator is below the chest. I suspect exhalation resistance would increase. I can't imagine standard high pressure hoses would offer a solution, as I believe the volume of air they deliver is quite low, is it not?

Good luck!

Don

[Deleted]

John\
I started my thread and then read yours......should have read yours first............check out the photo of JC with a chest mounted reg............

Mossback

[sitkadiver]

John,

Are you thinking of side mount diving? You could add a couple of quick connectors so you could clip each tank on independently... Not sure how dry it would keep you 1st though..............?

[gj1963]

Interesting... A few years ago I set up a DA as a chest mount. Plugged first stage and fed air from a conshelf into the hookah port. It worked too well, it was uncomfortable to breathe off of over several dives. Felt like drinking from a fire hose.

[SeaRat]

Nov 24, 2014 20:31:42 GMT -8 gj1963 said:

Interesting... A few years ago I set up a DA as a chest mount. Plugged first stage and fed air from a conshelf into the hookah port. It worked too well, it was uncomfortable to breathe off of over several dives. Felt like drinking from a fire hose.

Actually, I'm thinking of doing this experiment with my Royal Aquamaster in the same way you describe it above. I'll let you know how it comes out.

Dave, I'm not thrilled with side-mounts, as the hydrodynamics just isn't there for me. My thought is to make the double hose regulator independent of the tank's valve position, and lower on the back of the diver than many configurations with today's tanks allow.

John

[cnotthoff]

Hey John,

I just came across this thread. It's an interesting idea.

Did I miss something or are you supplying the first stage of your MR-12 with 140 psi? That would make breathing off it like breathing off a nearly empty tank. I don't recall the MR-12 was a single stage reg. Using a single stage would really make it hard to breath.

Since you are using the first stages from a couple of single-hose regs, can't you remove the first stage guts from your MR-12 (or any 2-stage DH) so that the 140 psi feeds directly to the second stage? If you use diaphragm first stages, you can set intermediate pressure to match second stage. The only problem I can see is being sure the hp diaphragm seals. It's still going to have no more than 140 psi to hold in, so shouldn't blow out.

I did something similar a while back with a Scubapro Pilot second stage. It has inlet fittings on the left and right. I ran a hose to each side from separate first stages hooked to 2 independent tanks in a doubles rig. It looked cool, but didn't really do anything for me.

I'm curious to hear how this works out.

Good Dives,

Charlie

[SeaRat]

Hi Charlie,

What I was using was two first stages off single hose regulators, with an intermediate pressure of about 140 psig, into a manifold center portion to feed a single stage double hose regulator (SCUBA Deluxe or Mistral). But the manifold center portion itself seems to not have the interior diameters to supply the single stage double hose regulator, and therefore acted as a restrictor orifice. Because I found this out during early tests in my garage, this concept has not been "wet" yet (pool or open water). I figure that the interstage pressure for this system to work needs to be between 250 and 500 psig, but the LP hoses are not so designed, and if I used an upstream single stage double hose regulator, there would be no overpressure relief valve on the system. I therefore declared the experiment a failed experiment. I still want to thank Don (DiverDon) for making the manifold that would allow use of LP hoses, but I don't at this point foresee taking this experiment "wet."

I may use gj1963's idea of the hookah port on my rebuilt Royal Aquamaster to accomplish the same thing, and that may be a better solution to removing the double hose regulator from the tank valve and onto the straps between the shoulder blades on the back of the diver. This would minimize the water column difference when a diver changes position, as the tank valves are on the tank, which is a straight line that does not bend with diver movement. Does that make any sense at all?

John