Honking Scubapro A700? Your experience?

[Luis H]

May I suggest some experiments?
Put a flexible 1” diameter hose between your single hose regulator and your mouth.

You need to try it with a D400, a conventional second stage (a Balanced Adjustable would work great), and if you can you should try a Poseidon Cyklon second stage also.

With the flexible hose you will be able to tell how the regulator breath as the depth of the regulator changes relative to your inner ear level.

You can also rotate the regulator (while keeping the diaphragm at the same depth) and see if it makes any difference in breathing performance.

Matt,
I am sure you have already noticed that the double hose mouthpiece will free flow like crazy when it is raised above the diaphragm, even if the opening is pointing down.

If you haven’t done it, you should at least take off you Scuba tank underwater with the double hose in front of you. Then move the tank/ regulator up and down relative to your inner ears and your lungs and see how it feels. try it both in a horizontal and vertical position. Hold the tank (not the tegulator) and close your eyes. Try to guess the possition of the regulator to you inner ear and then open your eyes.

You can also rotate the rig so that the double hose regulator faces up, down, and to the side. The exhaust will of course move relative to the center of the diaphragm. See if you can tell if it has any effects.


You can play with being horizontal or vertical. But, as far as I know the lungs don’t have pressure sensors (so you should not feel much difference about your position), but the work of breathing will cause some fatigue on the long run.

You could say that your inner ear and mouthpiece are very close to each other, but as far as I know we have pressure sensors in our inner ear not our mouth.


Another set of interesting experiments is to isolate the exhaust and intake. One easy experiment is again with a double hose. With a spare exhaust can you can move the exhaust and diaphragm relative to each other rand relative to you inner ear.


You should try these experiments. I think you will find the results very interesting.

By using a flexible hose with different types of single hose regulators it is easy to isolate the effects of position (facing up, down, or to the side) and depth of the diaphragm relative to the exhaust and to the diver.


I have done most of these experiments, but some day I may try to instrument the hose that connects the second stage to my mouth. I am thinking about looking for a Magnehelic that reads about 20 inWC and try this while I hold my mouth 12” below water. An assistant would have to read the gauge. My LDS has a test pool I can use to try this.


Added:
The only problem with these experiments is that humans are horrible instruments. Our sensations and sensory perception is influenced by many factors that are very difficult to isolate. That is why I would like to add some instrumentation to my experiments. But if one is careful with the observations (actual diaphragm depth, etc.) my experience is that it is possible to observe results that are meaningful.

 

[halocline]

Luis, I was afraid you'd see this thread..

In my mind there is little doubt that case fault geometry plays a role in the sensation of more difficult breathing in different positions, but I am starting to think that the depth relationship between diaphragm and mouthpiece has influence as well. I'm going to try your experiments, maybe over spring break (woo hoo!) and see what happens.

One question, if you were to separate the exhaust hose from a doublehose can and raise it up, I know that it would freeflow. If, however, you lower it so that it's several inches below the cans, what happens?

 

[Luis H]

Lowering the exhaust makes it more difficult to exhale… makes absolutely no difference to the inhalation. Try it. It is easy to do with a double hose.



A few more suggestions:
Do these experiments preferably in a pool or someplace with a clean hard bottom. Overweight yourself so that you can fix yourself on the bottom.

All this can be done in a shallow pool. That makes it easy to switch from one regulator to the next.

Remove the mouthpiece of the second stage to install the hose. A 12” to 18” hose or a bit longer works well.

When you rotate the second stage upside down, etc. make sure that you are keeping track of the actual height of the diaphragm.

It would really help if you could put a large mirror with a scale taped to the edge of it. The mirror can be just a 18” tall and maybe attach it to the back of a metal chair and bring it to the bottom of the pool.

The experiments I suggested with a double hose can be done without any (or minimal set up). With a single hose second stage it requires a little more set up, but IMHO it definitely worth while.

Take your time and repeat every test several times. You can try many different body positions and regulator positions. Close your eyes at times to avoid distractions.




Just one small preview of some of the results: you will feel a lot of the pressure differentials, but one of the neat things is when you lower the second stage (or the double hose) about 8 to12 inches below your mouth. At that point you will feel your cheeks ballooning (note: there is no danger as long as you are paying attention and don’t exceed much more than 12 inches).


One more interesting observation: move the hose loop (from the regulator to your mouth) up or down and see if you can sense any difference.

 

[sphillips3]

Just came back from Honduras where I took my brand spankin' new A700 and MK17 for a dive vacation. Love the A700, breathes great but some noticeable quirks. When above water, it honks. Makes breathing a little more difficult to get a smooth breath while getting ready to jump in or using it on the surface. Have also noticed that if I'm horizontal (face down), the breathing is great, but if I pick up my head to look ahead or look up, it seems that the draw is just noticeably more difficult than when I'm looking down.

Anyone have the same experience? I was told the honking is normal for the A700...? Isn't there something that can be done to eliminate that? And why would it be slightly more difficult to draw a breath when going from horizontal to vertical? Other than that, I'm happy with my new setup.

There is an updated diaphragm that is supposed to cure some of the honking. Because of the metal case the sound is especially noticeable and SP came up with a fix. Have your service tech call the mother ship and talk to Jules.

 

[MJJ]

This is all well and good, as long as I'm not the one (again) accused of veering a thread wildly off topic.

DA Toastmaster has provided an excellent explanation which I have interpreted to mean "there is a positional effect of the _regulator_ orientation, not of the _diver_ orientation." Did I get that right?

I was struggling with the numbers a bit and what you say makes much more sense. My thinking was along these lines: When I am prone, we can say for argument that there is zero difference between midpoint lung depth and regulator depth. When I am upright (head up, feet down) or inverted (feet up, head down), I would say for argument that there is about a foot (12") of difference between midpoint lung depth and regulator depth. Having just learned in class that one foot of water is good for about 0.5 psi, I'm drawn to think there must be some noticeable effect there. The only nagging thing is... far from just being noticeable, I think 0.5 psi is about the limit of my ability to pull in a breath.

So your explanation of depth differences in terms of inches and fractions of inches of depth makes much more sense to the observed effect.

Luis H, your experiments are inspired (no pun intended) and hooking up a manometer for concrete measurements would be very interesting.

So, the question then becomes, if you accept my guesstimates of lung and regulator depth, and compare those depths in my head-up vs. my feet-up positions, there's a full 1 psi of pressure difference that apparently we will take absolutely no notice of. How on earth is that accomplished?!?

 

[Couv]

Thank you Luis,

Boy am I glad the "very smart guy" showed up so I don't have to tangle with the two professors first, or by myself. Let's consider the real functions of the exhaust valve. First, it allows gas (or water, sand, dirt, fish, teeth, if there is any in the regulator) to escape when the diver exhales into the case. But the exhaust valve is also a check valve; it prevents water from entering the case when the diver inhales. I bring this obvious fact up in order to point out that after the very slightest pressure differential (on inhalation) between the dry side and the wet side of the diaphragm, the exhaust valve is totally out of the picture. While case fault geometry, as it relates to the exhaust valve, does have a very minor influence on free flow, it has and nothing to do with breathing resistance after the exhaust valve is seated. You can prove this by removing the exhaust valve and taping over the spider. This experiment removes the exhaust valve's roll in inhalation resistance from the equation, and is much easier than taking a chair, mirror, tape measure, magnehelic gauge, book, vcr, roll of dimes, and a person who'll assist you into the pool.

The factors that influence inhalation resistance of (the same) regulator is it's main diaphragm's position in the water column in relation to the mouthpiece and to the diver's lungs.

We can get into the whole discussion of long snorkels, etc later if we have to.

Cheers,

Couv

 

[DA Aquamaster]

When I get back from Minneapolis this weekend I want to fill the tub and then test the second stage on a magnahelic at various orientations to quantify the numbers listed in my previosu post. I think they will be very close to what people percieve as the increases and decreases in inhalation due to the orientation of the reg.

 

[elan]

My Zeagle ZX second stage does exactly the same, honking and increasing the effort

 

[Luis H]

This is all well and good, as long as I'm not the one (again) accused of veering a thread wildly off topic.

DA Toastmaster has provided an excellent explanation which I have interpreted to mean "there is a positional effect of the _regulator_ orientation, not of the _diver_ orientation." Did I get that right?

I was struggling with the numbers a bit and what you say makes much more sense. My thinking was along these lines: When I am prone, we can say for argument that there is zero difference between midpoint lung depth and regulator depth. When I am upright (head up, feet down) or inverted (feet up, head down), I would say for argument that there is about a foot (12") of difference between midpoint lung depth and regulator depth. Having just learned in class that one foot of water is good for about 0.5 psi, I'm drawn to think there must be some noticeable effect there. The only nagging thing is... far from just being noticeable, I think 0.5 psi is about the limit of my ability to pull in a breath.

So your explanation of depth differences in terms of inches and fractions of inches of depth makes much more sense to the observed effect.

Luis H, your experiments are inspired (no pun intended) and hooking up a manometer for concrete measurements would be very interesting.

So, the question then becomes, if you accept my guesstimates of lung and regulator depth, and compare those depths in my head-up vs. my feet-up positions, there's a full 1 psi of pressure difference that apparently we will take absolutely no notice of. How on earth is that accomplished?!?

As I have mentioned, the lungs do the work of breathing, but they are surrounded by relatively powerful muscles and are not very sensitive to small pressure differences. They do not have pressure sensors.

The only true pressure sensor in our body is located in our inner ear. It can sense even small pressure differentials when we are flying, etc. That is why I continue to believe that the critical distance in the water column is from the regulator diaphragm to our inner ear.

The mouth and mouthpiece is just part of the tubing, just like the hoses in my double hose. They only sense large pressure difference like when I lower my double hose down about a foot below the mouthpiece. My cheeks tend to balloon at this point.

 

[Luis H]

Thank you Luis,

Boy am I glad the "very smart guy" showed up so I don't have to tangle with the two professors first, or by myself. Let's consider the real functions of the exhaust valve. First, it allows gas (or water, sand, dirt, fish, teeth, if there is any in the regulator) to escape when the diver exhales into the case. But the exhaust valve is also a check valve; it prevents water from entering the case when the diver inhales. I bring this obvious fact up in order to point out that after the very slightest pressure differential (on inhalation) between the dry side and the wet side of the diaphragm, the exhaust valve is totally out of the picture. While case fault geometry, as it relates to the exhaust valve, does have a very minor influence on free flow, it has and nothing to do with breathing resistance after the exhaust valve is seated. You can prove this by removing the exhaust valve and taping over the spider. This experiment removes the exhaust valve's roll in inhalation resistance from the equation, and is much easier than taking a chair, mirror, tape measure, magnehelic gauge, book, vcr, roll of dimes, and a person who'll assist you into the pool.

The factors that influence inhalation resistance of (the same) regulator is it's main diaphragm's position in the water column in relation to the mouthpiece and to the diver's lungs.

We can get into the whole discussion of long snorkels, etc later if we have to.

Cheers,

Couv

Thanks Couv

lol

I was just thinking about adding that experiment to the list. I had to leave to go to work (I was running late) and I don’t have access to the message board from work.

The easiest would be to use a second stage that the exhaust T can be removed. Then try all the same experiments of position with the exhaust covered. Just inhale from the regulator and exhale through your nose.

One can cover the exhaust with your hand and uncover it to try both conditions one after the other.

I haven’t actually done this experiment intentionally, but many years ago I did have a regulator with a leaky exhaust and I finished the dive by holding the exhaust when I inhaled.


With a double hose it is very easy to test that the lack of exhaust has no influence. I have just pinched the hose. The inhalation is not affected.


The case fault geometry does limit how low the cracking effort can be adjusted to avoid a free flow. This is the same effect Cousteau and Gagnan found in 1943. Using a duckbill right on front of the sensing demand valve diaphragm was the actual original patent of Cousteau and Gagnan.