Use one piston first stage, and one diaphragm, and adjust the diaphragm first stage to exactly the same IP as the piston. Then you will draw air equally from both cylinders.
SeaRat
Recent Opinions On Air Integrated Computers For Technical Diving
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SeaRat
Mike1967
Contributor
Sounds like a solution looking for a problem to me.
Problem: switching second stages every 500-600 psig per side-mount tank. Each time the regulator must be switched, the diver is without a second stage in his/her mouth, must clear the alternate second stage, then again concentrate on the other factors of the dive. If a switch is not made, then the tanks' buoyancy characteristics deviate from each other, and trim is adversely affected.
Solution: use a second stage which accepts both tank's first stages, and drains each at the same rate simultaneously.
I experimented with this a few years back, mounting my two first stages on independent twin steel 52 cubic foot tanks from USD. Scubapro' A.I.R. I regulator, and their next two generations, allowed attaching a single second stage to two independent first stages, which gave redundancy and better performance at depth to the second stage. Note that I used a Dacor Olympic 400 or Voit MR-12 diaphragm first stage as one of the regulators, a Scubapro Mk V first stage, and was able to match the IP of both first stages.
SeaRat
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Mike1967
Contributor
I understand it might work in that situation but a connection between two SM tanks would be more of a hassle than switching regs IMO.
Explain, please, Mike. Are you talking about before entering, or while exiting the water, or in-water, being more of a hassle? Isn't it at least somewhat of a hassle to switch regulators every 10-15 minutes, or face loss of trim? I have not done any side-mount diving, as I dive rivers in high current, and so feel sidemount itself won't work for me. But I need to know the nature of the "hassles" of not having to remove and switch second stages for a side-mount diver means. You might try it and see how you like it. These very good performing second stages are regularly available on E-Bay.
Scubapro Air 1 scuba regulator with hose AIR1 | eBay
SeaRat
PS, the above independent doubles with a single second stage (and octopus second stages) works, and works well; it's not that they "might work."
I dive WAI on all my setups (sing tank BM, SM and tech)
I hear a lot of people say "what happens when your transmitter fails?" Well, what happens when your SPG fails? You end the dive! I dive a Perdix AI and have never had an issue with a lost signal. Nor have I ever had a transmitter broken off because someone picked it up by the TX. This is something we hear often with no real life stories to back it up.
As for switching regs in SM, it is not an issue. My reg is out of my mouth for a few seconds at most while switching. No different than switching to a deco gas on your ascent.
I fully believe WAI is the future of diving and it won't be long before we see SPGs on sites like Vintage Double Hose. Just my 2 bar.
I hear a lot of people say "what happens when your transmitter fails?" Well, what happens when your SPG fails? You end the dive! I dive a Perdix AI and have never had an issue with a lost signal. Nor have I ever had a transmitter broken off because someone picked it up by the TX. This is something we hear often with no real life stories to back it up.
As for switching regs in SM, it is not an issue. My reg is out of my mouth for a few seconds at most while switching. No different than switching to a deco gas on your ascent.
I fully believe WAI is the future of diving and it won't be long before we see SPGs on sites like Vintage Double Hose. Just my 2 bar.
Mike1967
Contributor
You want both tanks to be totally independent. You might want to enter the water with one on and get the other passed to you. You also might want to pass one or both off before you exit the water. Apart from all that, having them drain together you've basically lost your reserve.
Not at all, it literally takes 10 seconds....if that.
As I said, this is just my opinion, others might disagree.
Mike1967
Contributor
Why not just put a manifold on them?
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they have to be balanced the same and depth compensate the same as well, you'd want to do it with identical first stages.
Tying the second stage together like that is asking for trouble and would be completely impractical for any real technical diving where we are making gas switches or if you have to do any bottle off sections. That solution is actually worse IMO than the UTD z-system.
As for switching, how annoying is it for you to switch to your secondary? It's a basic skill we teach in open water training and since the regs are right there under your chin or right off to the side, the reg is out of your mouth for maybe 2-3 seconds. Why would that result in a loss of trim?
No they won't
One spring will be ever so slightly different than the other so at depth the IPs wont be the same and you will end up preferentially drawing from one cylinder or the other. UTD tried this, they created the "Z-isolator" once they figured out (it took them a few months of trial and errors) that you can't ever get the tanks to balance.
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