My "new" independent doubles setup

[AfterDark]

I've never dove SM or independent doubles so I have no experience to justify my opinion...so here it is.

Looking at this it dosen't seem to complicated in theory. Maybe it's complicated in hardware but the theory of it's use seems straight forward.
I'm imagining it goes something like this...

1. Turn on air.
2. Put modified regulator in mouth with one in line valve open and the other closed.
3. Breath.
4. After breathing 500 psi from one tank, reach up and close one inline valve and open the other.
5. Breath and repeat the process every 500 psi.

Seems simple. All the hardware "looks" complicated but it dosen't seem hard to use in theory. The in line shut offs for the secondary 109's seems excessive but I guess it prevents free flows.

You could get really crazy and get a dual bladder wing and add TWO Air2's and then you'd have 5 second stages!!! Take that redundancy.

Is it the hardware that people don't like? Is there a reliability problem with the in line shut offs? I really don't know and am seriously curious as to why people think this is a bad idea. Is there something inherently dangerous about the setup or is it just different. It looks like something I would engineer with my Wile E. Coyote brain.

I hope it works out like you envision. Update as you proceed please. Be safe.

You have hit the nail right on the head in this post! The thing most do not like is the amount of connections required. Every one is considered a weak point. I don't disagree with that one bit. With that in mind extra attention to system integrity is paramount. Checks for leaks and loose connections using wrenches and soapy water will be part of my pre-dive protocols.

Different is always bad or dangerous to most people, I know because I've been different all my life. Outside the box thinking is my way of life so I get to see and receive the brunt of people's bias and fears up close like. Thanks for your post.

 

[Wibble]

Interesting configuration.

Do you have a replacement second stage somewhere?

The point of independent twins/doubles is, like sidemount, they're completely separate and fully redundant. Ignoring the long-hose debate for a moment, having two regulators bungeed on necklaces would mean you've a fully redundant system with simplicity at it's heart.

Add a single longhose to the mix and you can tell which reg you're breathing from as one has a bolt snap.


I've had a bit of a personal issue with very non-standard configurations ever since I was sitting next to a guy on a boat with a ridiculous monstrosity of a rig: a twinset with a ponied (as in mounted on the side of the twinset) 7 litre (55cf ???) deco cylinder. To all of that was three sets of recreational regulators with 'console' gauges and a "slob-knob" remote control for the isolator valve. I spent ages looking at it to work out what the heck was going on.

He died. We suspect he didn't turn his gas on.

Please be careful of esoteric equipment configurations.

 

[AfterDark]

It always amazes me when someone has a different setup and others jump on the bandwagon of "that's not right!" We've all changed our setups over time, this is no different, just multiplied by a lot more time. I can't imagine what my setup will look like after 50 YEARS of diving! In comparison, I'm still just learning to crawl....haven't even made it to baby steps yet, lol. What happened to dive and let dive?

Thanks for sharing @AfterDark, I'd dive with you in that setup any day.

I hope you do see 50+ years of diving! My only regret in 53 years of diving is I didn't dive more!

 

[Wibble]

A question springs to mind (it's engineering, not principles)...

What's the effect of connecting two first stages together using the LP hose?

With the two shutoffs, if you were to open them both at the same time, then the two first stages would be connected together. It's unlikely that both would have the same IP (intermediate pressure) settings, so the lower pressure one would get more pressure.

Would this simply be blocked by the 1st stage effectively acting as a one-way valve? i.e. no effect.

 

[AfterDark]

Interesting configuration.

Do you have a replacement second stage somewhere?

The point of independent twins/doubles is, like sidemount, they're completely separate and fully redundant. Ignoring the long-hose debate for a moment, having two regulators bungeed on necklaces would mean you've a fully redundant system with simplicity at it's heart.

Add a single longhose to the mix and you can tell which reg you're breathing from as one has a bolt snap.


I've had a bit of a personal issue with very non-standard configurations ever since I was sitting next to a guy on a boat with a ridiculous monstrosity of a rig: a twinset with a ponied (as in mounted on the side of the twinset) 7 litre (55cf ???) deco cylinder. To all of that was three sets of recreational regulators with 'console' gauges and a "slob-knob" remote control for the isolator valve. I spent ages looking at it to work out what the heck was going on.

He died. We suspect he didn't turn his gas on.

Please be careful of esoteric equipment configurations.

Replacement 2nd stage? As is in a second AIR at home as a spare or another 2nd stage on the rig? There is a 156 2nd stage on the right side tank. It's not in the picture it is mentioned in the text of my 1st post. It's there in case of a AIR 2nd stage failure and for donation. The system is definitely not as fully redundant as the current configuration in the 1st picture with 2 156s.

However with a long history of zero in water failures with the current/original configuration my thinking is a small reduction in redundancy is within my acceptable risk limits. The chances of the AIR and the right hand 1st stage or the156 attached to it failing at the time is very remote and that is the only scenario that would leave me in an OOA condition or unable to access the air in either tank. Or if all 3 inline on/off switches fail at the same time. Both scenarios or so unlikely that it really isn't a concern for me.

If I do my job of air management correctly, I always have ample air to surface safely and end the dive in case of equipment failure. Thanks for your post.

 

[AfterDark]

A question springs to mind (it's engineering, not principles)...

What's the effect of connecting two first stages together using the LP hose?

With the two shutoffs, if you were to open them both at the same time, then the two first stages would be connected together. It's unlikely that both would have the same IP (intermediate pressure) settings, so the lower pressure one would get more pressure.

Would this simply be blocked by the 1st stage effectively acting as a one-way valve? i.e. no effect.

My understanding of the way that works is the 1st stage with the higher IP will be drained 1st then the other tank. However both MK5s I'm using have rock solid 135psi IPs, no drift. My guess is it would be like having an old school doubles manifold on the tanks where both drain at the same rate however they cannot equalize each other as they would with a manifold, the 2nd stage AIR is in control.

Of course with my ID protocols I would either pick that up on a SPG check or at the 1st 500 psi switch when I would find both in the open position. If both are open then that is operator error, those switches are real positive on/off ya can't just bump one and have it change position.

 

[lexvil]

Flow from the higher IP tank should, in theory be primary but the AIR 1 can move a lot of air, IP would probably have to be more than 15psi higher but moot with the inline valves.

a D420 would make me feel better, if you can find a used one they aren’t to nutty expensive, no idea of the cost of the second inlet port but probably not to crazy. It’s getting harder to keep an AIR1 running as many parts are only available by scrapping another one. The 420 should keep going for a long time and (I’m pushing 67 and still diving but only been at it for 50 years) when you decide to quit diving it will sell more easily than an AIR1.

 

[AfterDark]

Flow from the higher IP tank should, in theory be primary but the AIR 1 can move a lot of air, IP would probably have to be more than 15psi higher but moot with the inline valves.

a D420 would make me feel better, if you can find a used one they aren’t to nutty expensive, no idea of the cost of the second inlet port but probably not to crazy. It’s getting harder to keep an AIR1 running as many parts are only available by scrapping another one. The 420 should keep going for a long time and (I’m pushing 67 and still diving but only been at it for 50 years) when you decide to quit diving it will sell more easily than an AIR1.

I have given my diving end and what to do with my gear a lot of thought for quite sometime and have come to the conclusion that none of it owes me anything it has performed better than I could have ever expected. It looks its age and so do I, so what? They have modern internals nitrox friendly o rings serviced regularly with at least spec parts if not OEM, VDH.com sells outstanding service kits for MK5s 109s and 156s. The AIR was serviced last year by a qualified tech that posts on the board and I'm confident that it is solid. So the bottom line is, if I had to sell it all for scrap weight I got my monies worth and more in knowledge, fun, and great people diving has brought my way. As I posted the only regret after 53 years of diving is that I should have done more.
I suspect I will not be lamenting about not working enough overtime in my later years.

I checked on a D420 $700.00 and up. Maybe in your world that's not crazy money for a regulator but in my world it is out of reach.

 

[AfterDark]

Just read they found a rebreather diver face down, downunder.

I say this I'll feel a lot safer diving that rig than I would diving a rebreather. Those darn things will put a diver to sleep!

 

[OTF]

Pretty much anything is safer than a rebreather.

I like your weird setup. I agree with some of the criticism people have offered and personally I will keep my standard manifold and regs. But if nobody ever tried diving innovative setups like this we would never see any progress. Clearly you put thought into it and developed a rig to serve your needs in a reasonable way. Let us know how it's worked out in the water after a bunch of dives!