Aqualung Core Supreme - advice

[Luis H]

Well, I think I learned something today. I couldn't immediately agree or disagree with the statement that ANY second diaphragm is over-balanced, so I did some research.
From what I can find, the over-balance is a function of the ratio between the size of the two diaphragms. So the Legend and Apeks use a diaphragm on the environmental seal that has a larger operative surface area than the main diaphragm, and make the over-balanced statement. If they are the same surface area, then I believe there is no over-balanced effect. And of course, if they are close to the same size, I could see not making a statement that a 1st stage is "slightly" over-balanced.

If anyone else has something definitive to add, I am always ready to learn. And no, I did not break down any regulators to compare operative surface areas of diaphragms today, but you can bet I will be looking closely the next time that I work on one.

Your statement is for the most part correct.

But I would like to change one piece of terminology. We are technically not talking about balancing or over-balancing. The subject is actually about the ambient pressure compensation or over-compensation (of the ambient pressure).

I realize the manufacturers are all using the wrong terminology, but that is because it is being driven by their marketing group and not by engineering. As an engineer I dislike using the wrong terminology. What is the point of a common language if everyone makes their own definition?


So about the area ratio of the diaphragms.

I would like to introduce the term of “effective pressure area”. What I mean is that the two diaphragms may actually seem to have the same area, but they may not behave the same. The actual working area (or effective area) of a diaphragm can be affected by its stiffness, by the clamping condition, and by other constrains that limits its flexibility (like a large central disc).

The inside high pressure diaphragm is probably stiffer and the clamping force around the perimeter is probably higher. Therefore the edge will not flex as much and the effective flexible area may be significantly smaller than a more flexible diaphragm of the same diameter, for example the outer environmental camber diaphragm.

So the pressure areas of the two diaphragms may look to be similar (or the same), but the actual effective working pressure areas could be significantly different.

The percentage of flexible area lost can be significant since the constrained area is on the outer perimeter.


It is my speculative theory that “over-balance” (actual over-pressure compensation) was the result of originally designing the outer and inner diaphragms using the same diameter, but not taking into the difference in effective area due to diaphragm stiffness and perimeter clamping effect. Instead of correcting this issue, marketing just made into a advertising feature.

I have no proof that this is how it actually happened, but to me it seems like a logical explanation.


BTW, I have experimentally confirmed that performance of a second stage LP diaphragm can change as a function of how tight I clamp the diaphragm. In other words I was reducing the working effective area by clamping the a diaphragm too tight. I performed these experiment with a vintage double hose regulator (very large diaphragm)using a new very flexible silicone diaphragm.

 

[Luis H]

I should add that I have tested the IP of several regulators as a function of depth using a modified IP gauge. It was basically an IP gauge that I allowed to flood with large holes so that could rinse it with fresh water after the dive. I used a Y adapter to connect it to the LP inflator.

I have tested dry environmentally sealed Conshelf and the older Titans. We did not see any IP change on dives down to 90 feet.

I do not have any regulator that is advertised as "over-balanced" so I have not been able to test one of those, but I just though of a friend that has a Legend. I will try to remember test her regulator during a dive next year.

Here is a link to some of the IP test gauge I used.
Spec Boot For Mk-15

 

[JackD342]

Your statement is for the most part correct.

But I would like to change one piece of terminology. We are technically not talking about balancing or over-balancing. The subject is actually about the ambient pressure compensation or over-compensation (of the ambient pressure).

I realize the manufacturers are all using the wrong terminology, but that is because it is being driven by their marketing group and not by engineering. As an engineer I dislike using the wrong terminology. What is the point of a common language if everyone makes their own definition?


So about the area ratio of the diaphragms.

I would like to introduce the term of “effective pressure area”. What I mean is that the two diaphragms may actually seem to have the same area, but they may not behave the same. The actual working area (or effective area) of a diaphragm can be affected by its stiffness, by the clamping condition, and by other constrains that limits its flexibility (like a large central disc).

The inside high pressure diaphragm is probably stiffer and the clamping force around the perimeter is probably higher. Therefore the edge will not flex as much and the effective flexible area may be significantly smaller than a more flexible diaphragm of the same diameter, for example the outer environmental camber diaphragm.

So the pressure areas of the two diaphragms may look to be similar (or the same), but the actual effective working pressure areas could be significantly different.

The percentage of flexible area lost can be significant since the constrained area is on the outer perimeter.


It is my speculative theory that “over-balance” (actual over-pressure compensation) was the result of originally designing the outer and inner diaphragms using the same diameter, but not taking into the difference in effective area due to diaphragm stiffness and perimeter clamping effect. Instead of correcting this issue, marketing just made into a advertising feature.

I have no proof that this is how it actually happened, but to me it seems like a logical explanation.


BTW, I have experimentally confirmed that performance of a second stage LP diaphragm can change as a function of how tight I clamp the diaphragm. In other words I was reducing the working effective area by clamping the a diaphragm too tight. I performed these experiment with a vintage double hose regulator (very large diaphragm)using a new very flexible silicone diaphragm.

So I think we are in agreement that just adding the environmental seal diaphragm does not automatically impart over-balance (or whatever one calls it) to a 1st stage. It's the specific technical details that can be discussed ad nauseum. So in Apeks/Aqualung's terms, I would stick with their description of which models do and don't exhibit that property. Doesn't mean a Core Supreme might not be "a little over-balanced," but I would think it was a conscious decision to make no mention on that model, or the Titan LX Supreme that preceded it. BTW, I think the author of Regulator Savvy calls it hyper-balanced, IIRC.

 

[D_Fresh]

I won't go into the technical stuff and balanced/over-balanced as it's been well covered above.

I have the Core non-supreme (the warm water version) and really like it. I use a hose integrated computer and AI Transmitter, 40" primary with 90°, and integrated secondary backup. Plenty of ports on the first stage and I mostly like placement. I have a little bit of interference between my regulator hose and wing when the wing is mostly inflated, but not enough to worry me.

I do not recall what my tech set the crack value at, but with the venturi knob open it breathes sooooo nice. Simply think of breathing and I have air coming. And I still have no issues with free flow of I remove the reg underwater.

I travel a bit, around SE Asia, and have found has no issues with weight or size.

I'm happy with the setup. I wish you the best of luck!

 

[Luis H]

So I think we are in agreement that just adding the environmental seal diaphragm does not automatically impart over-balance (or whatever one calls it) to a 1st stage. It's the specific technical details that can be discussed ad nauseum. So in Apeks/Aqualung's terms, I would stick with their description of which models do and don't exhibit that property. Doesn't mean a Core Supreme might not be "a little over-balanced," but I would think it was a conscious decision to make no mention on that model, or the Titan LX Supreme that preceded it. BTW, I think the author of Regulator Savvy calls it hyper-balanced, IIRC.

That is correct.

The two examples I mentioned before (the Conshelf and the old Titan, both with dry environmental chamber) have a constant IP, independent of depth. The intermediate pressure above ambient was always the same. It was not affected by depth.