Regulator that breathes good in all directions?

[paulwlee]

I don't know about all the other stuff, but I breathe a SB R390 and R190 both with MK16 1sts. No difference in breathing regardless of orientation up to and including upside down.

Next time try laying on your back and looking up directly at the surface. (Or look directly up while vertical, but there the tendency is for people to tilt the head up only slightly when looking up which results in not much difference from more normal positions, which is why laying on the back is a better way to get that orientation.) If you don't notice a difference then, you are a human breathing machine.

That position, with the second stage facing up with diaphragm parallel to the surface yields the most noticeable difference. Other positions not so much. No way there is no difference, it's a matter of physics.

I've regularly used high end models of Atomic, Scubapro, Apeks, Aqualung, etc. and they're all the same in this respect.

One reason I suspect that people think there is no difference is that the diaphragm up position is not assumed very often while normal diving.

 

[halocline]

I can't believe I'm getting involved in this discussion again, but consider this: Position 1, vertical, head up. This position represents the maximum depth distance between regulator and lungs, with the lungs being deeper. Now, position 2, vertical, feet up. This represents the maximum difference in depth between reg/lungs, with the lungs being shallower. In these two cases, breathing resistance on most single hose, 2 stage regs is more or less equal. Yet, the difference in depth relationship between reg/lungs is maximized by these two positions.

Explain, clearly, how to resolve this apparent conflict.

Now, consider this. Axis of the 2nd stage diaphraghm horizontal, wet side down. This is normal, horizontal diving position. Flip the reg over, so the diaphraghm is horizontal, but with the dry (air) side down, and you have the maximum difference in breathing resistance. I've tried this in every possible body position I could get myself into, like upside down, at an angle, chin forward, horizontal on back, and whenever the axis of the reg is parallel to the surface with the dry side down, the reg breathes much more stiffly. This is regardless of the relative position of my lungs to the reg.

Now, take as an example the D400 with it's angled diaphraghm. When horizontal looking up, this reg's diaphraghm is not parallel to the surface; this reg also has the reputation fro not breathing as stiffly when looking up at the surface.

DA Aquamaster has posted extensively about "case fault geometry" in which the depth relationship between the diaphraghm and the exhaust valve impacts the inhalation effort. I have a feeling he's right.

But, I will still stick to my simple-minded explanation (no matter how many experts tell me the world is round!) that its the air-on-one-side vs water-on-the-other that's having the real impact. Yes, I know that gas in an enclosed area exerts equal pressure in all directions, but, the gas in the reg is buoyant. This is why when you turn a 2nd stage mouthpiece up, it freeflows; turn it mouthpiece down, it stops. Why should it be any more complicated than that?

Okay, Luis, you can let me have it again; it's been at least a year

 

[Nemrod]

"But, I will still stick to my simple-minded explanation (no matter how many experts tell me the world is round!) that its the air-on-one-side vs water-on-the-other that's having the real impact. Yes, I know that gas in an enclosed area exerts equal pressure in all directions, but, the gas in the reg is buoyant. This is why when you turn a 2nd stage mouthpiece up, it freeflows; turn it mouthpiece down, it stops. Why should it be any more complicated than that"

Unfortunatly this is not very good science, the world is in fact relatively round and angled or not the diaphram of the D400 is going to obey the laws of physics and your understanding of "air on one side and water on the other" is greatly incorrect.

N

 

[bperrybap]

The last two post is a perfect example of the biggest difficulty encountered when testing a regulator (or any other equipment highly involved with a human interface).

The two regulators may perform somewhat different, but they are both working in the same water column environment and both are affected by differential pressures. IMHO the biggest difference between the two is that two different individuals are testing them (and no calibrated instrumentation was used).

We are all different and some of us are very sensitive to small changes while some of us are not. Our perception is not only different from person to person, but it can change from one day to the next (or it can be influenced by many factors).

This is why human factors engineering is such a difficult science. Blind test are often performed in order to eliminate some of the biased perceptions that we all have, but even that is not very reliable.

When I was testing a double hose regulator in front of me while I was raising it and lowering, I tried it keeping my eyes closed, but as a human I am aware that I am not a calibrated instrument.


Oh …by the way…any instrument can introduce their own set of errors that have to be accounted for, but that is whole different subject.

Well, while I do agree with you that different folks will perceive
things in different ways, and instrumentation is the only
true way to get unbiased repeatable scientific data,
I can't agree with your comment about the biggest difference
between the "perceptions" of how a regulator breaths is primarily based
on the individual testers personal perceptions.


IF, everyone was testing and commenting on the same
regulator, then the argument would make sense. However
this is not the case. I'm also guessing that different individuals
commenting about breathing effort are not "testing" the regulator
in the same way when they are doing their breathing effort "testing".

Different regulators have different designs and internal/external
geometries that may affect how the regulator breathes and
might affect how it can breath in different orientations and
different water column depth differences.

Otherwise, how do you explain a regulator breathing "wet".
My guess is that just about everyone will notice wet breathing
similarly.

So while as you cited above "both working in the same water
column environment and both are affected by differential
pressures" they were not the same regulator and
each regulator may not react in exactly the same way to those
differential pressures depending on their internal design
and orientations.

It is also possible that since different divers are different sizes,
and those size differences can affect water column differential
differences between the lungs and the 2nd stage, that
different divers might in fact actually experience the very
same regulator differently strictly because they are different
sizes, not because one is any more or less sensitive to breathing
pressures.

In my case, I can tell you that when I use my Aeris regulator
I can look up and I can suck so hard that my cheeks cave into my
teeth and no air will come out.
However, if I switch to my Atomic SS1, and perform the same
test, while the breathing effort is noticeably more difficult when
looking up, I can still breath from it.

Also, when I'm horizontal in the water and turn my head to the side
and slightly look up, the Aeris breaths wet. And yes I have
confirmed that it is not leaking around my lips.
However, when using my SS1, the wet breathing in this
same orientation does not occur.

I've also performed similar experiments using a Sherwood
Shadow+ (octo inflator). Results are similar to the SS1.
While noticeable, it doesn't behave like the Aeris when
looking up.

So in this example there is no variation in the person testing
since I can do these tests back to back in the water using
all the same gear and 1st stage.

The difference is the 2nd stage regulator and perhaps how it is
tuned. The different designs simply work differently.

One thing I have noticed on the Aeris is that tilting my head
even just slightly to either side just a few degrees
when looking up will allow breathing.

So it seems to me that not only is the 2nd stage location
in the water column relative to the lungs and 1st stage a
factor but the orientation of the regulator diaphragm and exhaust
valve is also a factor.

--- bill

 

[DA Aquamaster]

If you control for everything other than regulator orientation (ie by just looking forward and then looking up or down.) you still perceive a significant difference in inhalation effort with any conventional second stage design.

This is because of the pressure changes inside the second stage due to the relative positions of the diaphragm and exhaust valve.

For example when looking horizontally in the water the center of the diaphragm is level with or just slightly above the upper edge of the exhaust valve, so the pressure acting on both locations is the same and the pressure inside the case is same as the pressure acting on both so there is no additional assitance or resistance affecting inhalation effort.

However in a face down position the center of the diaphragm is now the low point in the second stage and it has the most pressure acting on it. At the same time the upper edge of the exhaust valve is now the high point in the system. The result is that the air inside the case is (initially when the inhalation stops) pressurized to the level of the water outside the center of the diaphragm. This is perhaps 1.0" to 1.2" of water pressure higher than the pressure at the upper edge of the the exhaust valve. Consequently some air leaks out the exhaust valve, causing the diaphragm to move inward until it is stopped by the resistance of the lever it is in contact with. If there were no lever installed, the diapragm would move upward until the pressure inside the case equalized between the center of the diaphragm and the top of the exhaust valve. This would still not be quite the same pressure because of the resistance caused by the exhaust valve itself.

Practically speaking with the lever installed, the diaphragm rises until it is stopped by the resistance of the lever, meaning that in a face down position, the system is already pre-loaded so very little inhalation effort is needed to initiate the next inhalation. In fact, in most high performance second stages, this preloading effect is enough to cause the reg to freeflow slightly between breaths in a face down position unless the reg is detuned slightly as the poppet itself may require only .5 to .7" of water pressure to activate the valve in a situation where the pressure difference between diaphragm and exhaust valve is 1.0 to 1.2 " of water. Consequently most second stages are limited to a minimum inhalation effort in the .8 to 1.0" of water range to avoid freeflow issues in a face down position. (The inhalation effort can be stable even though it is .2 to .3" inches of water lower than the pressure difference due to the resistance of the exhaust valve and the slight pressure change that occurs before the diaphragm begins moving the lever.)

At the opposite extreme, when you are looking straight up, the center of the diaphragm is now the high point of the system and when you exhale the pressure inside the case is equal to the pressure at the upper edge of the exhaust valve - which is now about 1.0 to 1.2" of water pressure higher (since it is 1.0 to 1.2" deeper in the water column) than the the pressure acting on the diaphragm. What this means is that just before you begin to inhale the air pressure inside the case is actually trying to push the diaphragm away from the lever (since the pressure on the outside of the diaphragm is lower than the pressure inside the case) and the diver has to inhale harder to overcome this pressure difference. In terms of inhalation effort required, this is the worst case position for a conventional second stage regulator design.

The concept is easier to visualize if you take your second stage and rotate it to various orientations while visualizing what parts would be deepr or shallower in each position.

This effect is what Pete Wolfinger termed Case Geometry fault. It has nothing to do with physiology, but rather with the assistance or resistance acting on the valve assembly as the regulator orientation changes in the water column.

This is why the D400 was such an exceptional design in the water. The coaxial design of the diaphram and exhaust valve ensure that the maximum distance between the two could never exceed .5 " and the angled diaphragm design ensured that the worst case positions were in orientations divers seldom if ever would encounter. The result was a second stage that could deliver stable real world breathing performance in the .6" of water range with no need to adjust the reg in different orientations.

The current batch of SP engineers either failed to understand CGF or were over ruled by the marketing folks with the X650 design. In that design, the use of a D400ish angled diapgragm in combination with a conventioal exhaust valve location actually aggravates the CGF situation as the worst case situation in terms of a slight freeflow ocurring between breathes occurs in a normal swimming position rather than in a face down position. The really large and easy to open exhaust valve just further aggravates the problem.

As Luis indicated, the physilogical effects and the related perceptions involved are much more complex, but they are a distinctly different issue.

 

[Luis H]

I can't believe I'm getting involved in this discussion again, but consider this: Position 1, vertical, head up. This position represents the maximum depth distance between regulator and lungs, with the lungs being deeper. Now, position 2, vertical, feet up. This represents the maximum difference in depth between reg/lungs, with the lungs being shallower. In these two cases, breathing resistance on most single hose, 2 stage regs is more or less equal. Yet, the difference in depth relationship between reg/lungs is maximized by these two positions.

Explain, clearly, how to resolve this apparent conflict.

Read my previous post. Pressure sensation is not on the lungs it is in the inner ear. Therefore, IMHO the vertical distance to the ears is what maters (when we are talking about sensation or how it feels).

I own and have used D400s and side mounted diaphragm Poseidon regulators. They all behave the same. The only advantage is that the diaphragm is closer to the ears, but you can still sense a minor difference. It is all measured in inches of Water column.

Any owner of a double hose regulator can tell you that air will free flow out of a mouthpiece pointing downwards the moment the mouthpiece is higher than the diaphragm. It doesn't mater if the diaphragm is pointing up, down, or sideways.

This are all very repeatable physical observations. If they don't clearly demonstrate the physic I don't know what will.


"Case fault geometry" as in the maximum distance from from the sensing diaphragm to the exhaust, dictates how sensitive can the cracking pressure in a regulator be adjusted to (to avoid a free flow in any position).


Buoyancy is driven by the combined density of an object. Combined density being the total weight divided by the total volume. It doesn't mater if you combined heavy and light object (air in a steel cylinder, oil in a big light cylinder) or a any other low density material, the buoyancy can be the same. This is part of Archimedes principle, which used to be taught in basic scuba class.

When I did my basic Scuba training we learned about the diving scientist alphabet: A, B, C, D, and H. It is a shame that it is not taught anymore. Would you (or anyone) care to guess who they are?


And yes, I do feel like I am waisting my time. I can only hope that I am not.

 

[Luis H]

It is also possible that since different divers are different sizes,
and those size differences can affect water column differential
differences between the lungs and the 2nd stage, that
different divers might in fact actually experience the very
same regulator differently strictly because they are different
sizes, not because one is any more or less sensitive to breathing
pressures.


--- bill

I am not disagreeing with any of your points, but perhaps I am not always clear.

I also agree that your statement above could be an important factor.
How we affect the performance of the equipment is discussed heavily in white water kayaks, where the weight of different paddlers affects the displacement, water line, etc. of the boat. Therefore the same exact boat behaves totally different under different paddlers.

 

[Greg Barlow]

When I did my basic Scuba training we learned about the diving scientist alphabet: A, B, C, D, and H. It is a shame that it is not taught anymore. Would you (or anyone) care to guess who they are?

Luis, would those gentlemen happen to be: Archimedes, Boyle, Charles, Dalton, and Henry?

Greg Barlow

 

[Couv]

Luis, would those gentlemen happen to be: Archimedes, Boyle, Charles, Dalton, and Henry?

Greg Barlow

I learned more about physics from Joe Strykowski than all of my HS teachers put together.