My "new" independent doubles setup

[Angelo Farina]

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.

@halocline, I do not agree with your latest opinion. This configuration, with two MK5 first stages feeding a Pilot or an Air-1 with two hoses, was the officially recommended setup developed here at Scubapro Italy for diving very deep (75m to 100m and more) in air. At the time (1978) this was common practice here for coral hunters. Also the usage of manifolded twin sets was absolutely standard here, we were using them at the first course (together with the CC pure-oxygen ARO rebreather).
Please note that this is not considered "tech" by us, here in Italy "tech" was starting below 100m and with hypoxic trimix.
In 1978, both I and my friend Marco visited the factory at Casarza Ligure for being trained about servicing SP regs. The Scubapro technician allowed us to service our own MKV (MK5+109) under his guidance. After finished the training, he did show us a special military version of the Pilot with two MK5 first stages and two hoses. Back at home, Marco did purchase the same setup, as he was diving much deeper than me (I almost never exceeded 60m).
I have no photo by hand showing him with this setup, they are probably left in my old house.

What @AfterDark is attempting is to use the same setup with a compact twin set without manifold. I would prefer to have a manifold, keeping the central valve closed, than not having any manifold. I do not see any advantage in removing the manifold, except a very minor reduction of weight. But a manifold with the valve closed really does not change significantly how the system works. Only experimental tests can show how uneven will be the air usage from the two tanks.
But, as said, a certain degree of unbalance can be useful, leaving more pressure in the tank devoted to feeding the BCD. And if the unbalance starts to become excessive, @AfterDark can always close the inline valve of the tank with lower pressure.
I think that this setup with an Air-1 necklaced by two short hoses is a great idea when using an independent twin set.
It removes the need for periodically swapping the regs for keeping the air pressure balanced in the two independent tanks.
Here we are not talking about very deep diving in air, but about normal rec diving at depth of less than 50m, where one single first stage provides enough air flow. So closing one of the two inline valves does affect the performances. And managing the two in line valves is definitely more practical than managing the tank valves behind the head. This is still possible, in case, for example, of a first stage O-ring failure. But in most cases the usage of the inline valves is enough for ensuring to keep a reasonable reserve of air in both tanks.
I would have no problems using such a setup (for rec diving). I simply would add the manifold, for being able to use the air trapped in both tanks in case one of the two first stages fails.

 

[AfterDark]

@Angelo Farina he checked out of this thread 2x's already you could be him luring him in for 3rd checkout now after he posts again that is!

When a diver can't physically reach the manifold knobs the manifold serves no purpose, it acatully becomes dangerous because it can't be used properly. Manifolds also makes it too heavy for me to handle on land. I've lost too much muscle mass in my upper body to lift more than one tank. Plus I can take each tank to the waters edge and set it up there like SM divers are able to do.
I just manage my air and dive so that anytime during the dive I can abort and surface safely with the air left in one tank. It's not rocket science, just hard for people locked in their training paradigms to look at that setup and take the time to understand it, it doesn't look like what they were trained to see as safe so it isn't end of story.



You're forgetting that the inline switches are lethal and there are 3, a hat trick of killers, along with all those O rings, all conspiring and waiting, to drag me into the depths to certain death.

Except on Scubaboard where it is alive and well.

 

[Angelo Farina]

@Angelo Farina he checked out of this thread 2x's already you could be him luring him in for 3rd checkout now after he posts again that is!

You're forgetting that the inline switches are lethal along with all those O rings just waiting to drag me into the depths to certain death.

I never used inline switches, as for me it has always been very easy to reach the valves behind my head. But I understand that for people with limited shoulder mobility the usage of inline valves is THE solution.
I did envy a lot the Pilot of my friend Marco, but at the time I was absolutely broken.
Even purchasing my second MKV was a big effort, I did this only after an event where the main valve did close hitting the ceiling of a tunnel, and I ended OOA, buddy breathing the single reg of my girlfriend (which luckily was more cold-blooded than me).
We are currently yet using those regs, together with their twins which we purchased after that accident.
Also Marco still owns the Pilot, but he is not using it since decades. It was very difficult to service it properly...

 

[AfterDark]

I never used inline switches, as for me it has always been very easy to reach the valves behind my head. But I understand that for people with limited shoulder mobility the usage of inline valves is THE solution.
I did envy a lot the Pilot of my friend Marco, but at the time I was absolutely broken.
Even purchasing my second MKV was a big effort, I did this only after an event where the main valve did close hitting the ceiling of a tunnel, and I ended OOA, buddy breathing the single reg of my girlfriend (which luckily was more cold-blooded than me).
We are currently yet using those regs, together with their twins which we purchased after that accident.
Also Marco still owns the Pilot, but he is not using it since decades. It was very difficult to service it properly...

The pilot was a giant leap forward in regulator performance but has you say not so much in the servicing. The US Navy gave it high marks for performance but low in service. My understanding is that the A.I.R. I was an attempt to remedy the service issue while keeping as large a degree of performance as possible. IMO they again did the performance well enough but the servicing was still a bit complex. Again, IMO if the AIR had been metal instead of plastic it may have been more popular. I remember thinking when it first came out, one tank drop on that and it's done.
It wasn't cheap either and I already the MK5/109 that at that time was preforming like the champ that it is. So I left it to the rich guys as I have to do much more than I'd have liked.

Servicing a pilot now is a real challenge @Open Ocean Diver posted he has or is looking for one. Good luck to him I hope he can pull it off and brings it here for us to marvel at and envy.

Living divers keep their head and wits about them divers that don't often become part of a statistic.
I'm glad you are among former and not the latter!

 

[lexvil]

The pilot was a giant leap forward in regulator performance but has you say not so much in the servicing. The US Navy gave it high marks for performance but low in service. My understanding is that the A.I.R. I was an attempt to remedy the service issue while keeping as large a degree of performance as possible. IMO they again did the performance well enough but the servicing was still a bit complex. Again, IMO if the AIR had been metal instead of plastic it may have been more popular. I remember thinking when it first came out, one tank drop on that and it's done.
It wasn't cheap either and I already the MK5/109 that at that time was preforming like the champ that it is. So I left it to the rich guys as I have to do much more than I'd have liked.

Servicing a pilot now is a real challenge @Open Ocean Diver posted he has or is looking for one. Good luck to him I hope he can pull it off and brings it here for us to marvel at and envy.

Living divers keep their head and wits about them divers that don't often become part of a statistic.
I'm glad you are among former and not the latter!

The AIR 1 was a work around on the Pilot patent and did an excellent job of getting performance from the design, working on them is like arthroscopic surgery. The biggest hold back to keeping them in service is the diaphragm and it’s clip. The plastic (the term doesn’t do this material justice) is vastly superior to the thin metal of the pilot although not nearly as pretty.

 

[AfterDark]

The AIR 1 was a work around on the Pilot patent and did an excellent job of getting performance from the design, working on them is like arthroscopic surgery. The biggest hold back to keeping them in service is the diaphragm and it’s clip. The plastic (the term doesn’t do this material justice) is vastly superior to the thin metal of the pilot although not nearly as pretty.

Who knew that besides Scubapro in ?1981? I did strongly suspect neither were superior to the armor plated 109.

 

[lexvil]

Who knew that besides Scubapro in ?1981? I did strongly suspect neither were superior to the armor plated 109.

The armor takes its licks and shows it, I don’t use 109 any longer because I don’t want to bang them up, now I prefer the “plastic” seconds but bottom line reality is it regulator design stopped with the MK 5 and 109 we would all be ok and alive.

 

[James79]

The armor takes its licks and shows it, I don’t use 109 any longer because I don’t want to bang them up, now I prefer the “plastic” seconds but bottom line reality is it regulator design stopped with the MK 5 and 109 we would all be ok and alive.

Mk5, 109, and Conshelf....

 

[lexvil]

Mk5, 109, and Conshelf....

While I acknowledge the conshelf as a very good regulator, my dislike for the brand goes way way back and many completely obnoxious people associated with them, a personal thing (conshelf is one of those Regs, like a MK 2 that you can dig out of a scrap box and more often than not use it without service)

 

[James79]

many completely obnoxious people

ok, ok, I'll pipe down! lol