More restrictive inhale when face up with regulator

[Akimbo]

It makes perfect sense... But the OP to say "But I felt a significantly more difficult inhalation the moment I turned myself facing to the surface "…

Talking rough numbers, let’s say the lung center-mass is 12" from the center of the regulator diaphragm when the body is vertical in the water column and facing forward. The actual center of force on the lung may actually be lower on some people since the rib cage deflects a lot of hydrostatic force (pure speculation on my part)? Looking up moves the center of the regulator diaphragm about 6" higher in the water column. I can see a rapid 50% increase in water pressure being noticeable — perhaps moving over the threshold where this individual can sense it or not.

Unless I completely misunderstand the question, it is more an issue of activation pressure on the second stage than the flow rate. I know that I have to be very relaxed in dead-calm warm water without a suit and concentrate to detect positional difference. I doubt that changing the second stage would change that. Even if the second stage was badly tuned, it would be equally poorly tuned in any position.

If I remember correctly, the Conhself 14 (hate Roman numerals) is an unbalanced second stage with a larger diameter diaphragm. This would theoretically work against you requiring more lung force to activate against the differential pressure on the larger diaphragm surface area.

The “unbalanced” part isn’t the issue other than it requires a larger diaphragm to activate the demand valve. Both the Conshelf and Atomic regulators produce about the same performance in instrumented breathing machines. The big variable is individual bio-mechanics. Maybe your body structure around the lungs is more effective at deflecting hydrostatic pressure than mine or the OP’s? We know the physics is sound; it is only an issue of being able to sense it.

 

[wedivebc]

So he's right in that each fsw is worth .445psi. But since my mouth is roughly a foot above my lungs, .445psi is nothing. I doubt you are calibrated enough to detect that difference in suck factor Yes, I made that term up.

I am surprised hearing this from you. I find back mounted counterlungs have a HUGE suck factor (I'm going to start using this) when turned on your back. Isn't this why many rEvo divers disable their ADV? Much less than .445psi to create a suck factor.

 

[Superlyte27]

No, we disable the ADV because it's a total worthless piece of crap. - more later on bmcl. I'm eating

 

[herman]

So he's right in that each fsw is worth .445psi. But since my mouth is roughly a foot above my lungs, .445psi is nothing. I doubt you are calibrated enough to detect that difference in suck factor Yes, I made that term up.

Actually, 0.445 psi is a HUGE deal when you are discussing regulators.....as you should know, regs are rated/tested in inches of water column (IWC) not psi. The conversion from PSI to IWC is 27.7 to 1 or in this case .445 x27.7= 12.3 IWC. A good reg breaths at around 0.75-1 IWC, a poor one at 1.5 and a really bad one at 2 ICW. .445 psi/12 IWC would be like a thick milkshake through a straw. As far as detecting the difference, with a little practice 0.25 to 0.50 ICW is easy to detect, pretty much anyone can detect a 1 ICW difference if they are paying any attention at all.

OP, what you are feeling is the difference in position of the second stage diaphragm in the water column in reference to your body...the actual detection point is a matter of debate, depending on reg design and relative position, this can range from very slight to somewhat noticeable. It's normal but most people don't notice it. While it might not seem like a big deal, an inch or less change in position can make a noticeable difference in the way a second stage breaths. Double hose divers (which I am) are well aware of this.

 

[seeker242]

I havent tried it with an atomic reg but all of my other regs breath differently when I am face up underwater. It happens. Regs are optimized to breath when face down in a horizontal position.

I have an Atomic Z3 and I can tell there is a difference. Not really that bad though, but it's definitely different!

 

[oldschoolto]

The first time I made a pass in a top fuel car , I could tell the difference from the door slammer pro-mod I was running... I could not tell the difference between running a 5.850 at 243 mph and a pass at 5.79 at 248 mph... The only way to tell was look at the time slip.... I can tell the difference as Herman said when I dive my Aquamaster double hose... But not with my conshelf 14

Jim...

 

[timz]

Talking rough numbers, let’s say the lung center-mass is 12" from the center of the regulator diaphragm when the body is vertical in the water column and facing forward. The actual center of force on the lung may actually be lower on some people since the rib cage deflects a lot of hydrostatic force (pure speculation on my part)? Looking up moves the center of the regulator diaphragm about 6" higher in the water column. I can see a rapid 50% increase in water pressure being noticeable — perhaps moving over the threshold where this individual can sense it or not.

Unless I completely misunderstand the question, it is more an issue of activation pressure on the second stage than the flow rate. I know that I have to be very relaxed in dead-calm warm water without a suit and concentrate to detect positional difference. I doubt that changing the second stage would change that. Even if the second stage was badly tuned, it would be equally poorly tuned in any position.

If I remember correctly, the Conhself 14 (hate Roman numerals) is an unbalanced second stage with a larger diameter diaphragm. This would theoretically work against you requiring more lung force to activate against the differential pressure on the larger diaphragm surface area.

The “unbalanced” part isn’t the issue other than it requires a larger diaphragm to activate the demand valve. Both the Conshelf and Atomic regulators produce about the same performance in instrumented breathing machines. The big variable is individual bio-mechanics. Maybe your body structure around the lungs is more effective at deflecting hydrostatic pressure than mine or the OP’s? We know the physics is sound; it is only an issue of being able to sense it.

I don't really thing it's biology. I think it has to be something to do with the regulator orientation.

I am surprised hearing this from you. I find back mounted counterlungs have a HUGE suck factor (I'm going to start using this) when turned on your back. Isn't this why many rEvo divers disable their ADV? Much less than .445psi to create a suck factor.

What is ADV??

 

[Akimbo]

I don't really thing it's biology. I think it has to be something to do with the regulator orientation...

Regulator orientation is certainly the primary factor. But Jim/Oldschoolto’s comment indicated he never detected any difference (paraphrasing). The physics isn’t in question so there must be other factors preventing this very experienced diver from perceiving the pressure change. Biomechanical variations is the only logical explanation I could come up with.

 

[Superlyte27]

An ADV is a feature on a rebreather that automatic delivers diluent through a valve when lung volume gets too low. On the 4 or 5 rebreathers I'm certified on, the only one that works perfectly is the Optima.

So, what's supposed to happen is.... lung volume gets low, the ADV fires to add gas to the lungs so you can keep breathing.
It's an absolute piece of crap on the rEvo. So most of us disabled it.

 

[oldschoolto]

Regulator orientation is certainly the primary factor. But Jim/Oldschoolto’s comment indicated he never detected any difference (paraphrasing). The physics isn’t in question so there must be other factors preventing this very experienced diver from perceiving the pressure change. Biomechanical variations is the only logical explanation I could come up with.

You may be onto something... We had a thread sometime ago about having an adjustable flow control on the second stage.. And I remember posting .. " I don't remember ever being on a dive that I said ( Boy I'M GLAD I'M DIVING MY 109 ) VS my Conshelf " .. But , I also change breathing " BEFORE " changing workload... Rather than waiting for my body to change breathing rate/volume due to workload...

Jim...