My "new" independent doubles setup

[AfterDark]

We'd have more Aqualung! I still like the Conshelf (the old chrome ones).

My instructor told me in 1968 if I used USD gear I'd die, he was a Scubapro dealer. LOL!! Kidding

 

[halocline]

IP drops as tank pressure is reduced on the MK5 with highest starting IP, which would be initially feeding the system. Soon the 1st stages reach a point of matching IP and both begin feeding the 2nd stage equally. Both tanks draw down at an equal rate from that point onwards and both tanks reach empty on the same breath.

Is my thinking correct?

Not really, if they were unbalanced piston regs with a substantial drop in IP as tank pressure dropped, then yes you would be correct. But these are balanced 1st stages with only a slight (maybe 7psi) drop over the supply range, and it's not linear, because there is a friction component on the HP o-ring which is much higher when very tank pressure.

What I think would happen (its only a guess) is that under demand, especially at some depth, IP will drop in the hoses enough to open both 1st stages, but not equally. I would expect that the tanks would both drain but not predictably even. This is, of course, assuming that you have somewhat matched IP on the two regs to begin with.

The whole thing is just a really bad idea that solves absolutely no problem and creates the potential for more. But OP couldn't care less what I think or the posters that have years of experience training divers to survive in very demanding technical environments. So I'm going to check out of this thread.

 

[Kupu]

Not really, if they were unbalanced piston regs with a substantial drop in IP as tank pressure dropped, then yes you would be correct. But these are balanced 1st stages with only a slight (maybe 7psi) drop over the supply range, and it's not linear, because there is a friction component on the HP o-ring which is much higher when very tank pressure.

What I think would happen (its only a guess) is that under demand, especially at some depth, IP will drop in the hoses enough to open both 1st stages, but not equally. I would expect that the tanks would both drain but not predictably even. This is, of course, assuming that you have somewhat matched IP on the two regs to begin with..

Thanks for the additional information, after a bit more thinking I saw obvious flaws in my guess that both tanks reach empty at same time.

 

[Gone for diving]

My quess there will be a bunch of people that will not like this

Ps there are check valves inside the 2 BCD nipples which are high flow ported(with a file). And has a high flow 3/8 ID yellow hose for a reservoir,

 

[OTF]

Is that some sort of surface supply rig? What is that supposed to accomplish? It's awful, I absolutely love it.

OP's system was always meant to be used with only one shutoff open at a time, right?

 

[Ghost95]

My quess there will be a bunch of people that will not like this

Ps there are check valves inside the 2 BCD nipples which are high flow ported(with a file). And has a high flow 3/8 ID yellow hose for a reservoir,
View attachment 675872

That's quite a setup, what's it for?

 

[AfterDark]

That's quite a setup, what's it for?

It does look like a it's setup for surface supply and maybe additional 2nd stages or air tools. I think I'm looking at 3 empty male quick connectors on the splitter. Poster didn't give many details.

 

[AfterDark]

Not really, if they were unbalanced piston regs with a substantial drop in IP as tank pressure dropped, then yes you would be correct. But these are balanced 1st stages with only a slight (maybe 7psi) drop over the supply range, and it's not linear, because there is a friction component on the HP o-ring which is much higher when very tank pressure.

What I think would happen (its only a guess) is that under demand, especially at some depth, IP will drop in the hoses enough to open both 1st stages, but not equally. I would expect that the tanks would both drain but not predictably even. This is, of course, assuming that you have somewhat matched IP on the two regs to begin with.

The whole thing is just a really bad idea that solves absolutely no problem and creates the potential for more. But OP couldn't care less what I think or the posters that have years of experience training divers to survive in very demanding technical environments. So I'm going to check out of this thread.

You indicated you were done with this thread on your other post but here you are again. Can't help yourself can you?

I'm the one with 50+ years diving experience. At this stage of my diving I'm done with demanding environments in what's more I was doing what called is technical diving these days before it was called technical diving and because of the state of diving technology at the time it was a lot more demanding than it is now. So please take your hero worship of these tech divers and check out of this thread like you posted. It gets tiring. The main reason I dive doubles in any configuration is to try to reach my NDL in OW ocean at rec. depths for that a ID set fine.

 

[Open Ocean Diver]

Have you tested your rig on dry land with both switches open essentially connecting the 2 ip chambers together? Have an ip gauge and SPG on each first stage to see how they react when when breathing on your air regulator.

 

[Gone for diving]

I built this when I wanted to simplify side mount I think stowing and unstowing hoses is a pain with thick gloves on...

But I also planned that it could be use to jack in and feed back into my on board rebreather dil... if IP pressure was a bit lower than my sling tanks... you can save onboarding dil unless you really need it.
The 2 Y bcd nipples have small rubber balls inside. And act as check valves as long as there is pressure inside the hoses.
So I can hook up only one bottle