Future advances in regulator design?

[Luis H]

Yes, I agree that the decision to go with single hose regulators by the major manufacturers was a business decision, i.e. motivated by profit more than by product innovation. And it is true that at the time, the single hose regs solved the position-sensitivity issue, which I'm sure was seen by many divers as a significant improvement. The regs were cheaper to build and more popular for the expanding recreational dive market. You can't blame them for going in that direction.

But this thread is about regulator performance innovation, not about what makes the most money for manufacturers.

In the 1970’s the primary reason for discontinuing the double hose (specifically the Royal Aqua Master) was not the breathing performance. As a matter of fact , the RAM had a strong reputation of being a better performance regulator than most of the single hose regulators at the time.

Part of the explanation could have been that the single hose regulators (US Divers Calypso or Conshelf, Scubapro Mk-5, Poseidon Cyklon, et.) did not come out of the box tuned to the level that we have come to expect or have achieved now-a-days. The expectations have changed a bit through the years.

The RAM does not require the same level of fine tuning to perform and we were all using plain backpacks which places the DH in a good position.

The RAM was at the time venerable as a better performer, but it required more maintenance (due to the rubber parts), it required re-tooling to add HP and LP ports, it was bigger and occupied more space in a dive bag, and probably most important: it was not slick looking like the newer single hose regulators.

Actually, IMO, the lack of an HP port to attach a pressure gauge was probably the “kiss of death” for the RAM. At least it was at for us at Divers Service Center where I worked. The delicate appearance of the big hoses (even if they weren’t that delicate) was also a big factor.

After production of DH regulator stopped, the supply of specialized rubber parts (specially the duckbill) dried up and many DH regulator were not serviced or kept in operation, but many owners did go out of their way to find or make parts.

When designing the new DH regulator, I intentionally decided to study lessons learned (from both DH and single hose regulators) and to try to resolve the major issues and improve anything that was reasonable (under the budget of essentially a hobby).

We have design tools and prototyping tools that were not even dreamed of in the 1970’s. Even as an individual I have access to computer, instrumentation, and prototyping tools that Gagnan, Spirotechnique, US Divers, or Scubapro couldn’t even dream of having back then. And I have samples of their designs (and some documentation) to use as background knowledge to build upon.

Aqualung obviously has many more resources that than I or VDH has, but they don’t have the interest and I am OK with that. The “new Mistral" was basically a "bad-design" and all it did was set back the acceptance of new DH concept.

For many reasons (breathing performance not necessarily being one of them) the DH will probably always be a specialized market. I keep comparing it to driving a stick-shift versus driving an automatic transmission vehicle. A very small population (me included) drive a stick-shift in the US anymore. It is just “too much trouble” and it requires skills that many drivers don’t want to learn. I think it is a lot more fun, but that is just me.


BTW, to the OP, I still have a concept in my mind on how to add a “muffler” to the exhaust bubbles and a way of dispersing them a bit. The trade-off may be the size which may make it less appealing, but I will be looking into it.

 

[Luis H]

Ergo, we have an issue where instructors want the regs to be slightly detuned and people who rent those regs want them to tuned to a knife's edge.

Given the premise of this thread I would like to see a regulator that would NEVER free flow unless something in the first stage had broken.

R..

In a way, that was what the venturi deflector and the diver adjustable second stages (and in some regulators the dive/ pre-dive switch) were intended to accomplish.

 

[Akimbo]

I did a lot of work investigating WOB with high HeO2 densities at depths greater than 400M/1,312'. Assisted breathing at the center-mass of the lungs gets complicated really fast. This was complicated farther since there was also an exhalation regulator for gas recycling at the surface. We were able to do it electronically but reliability sucked due to so many additional failure points.

The real question for recreational divers is what is good enough? Current regulator WOB is good enough on air to about 60M/200' based on all the research I have seen. I doubt that there will be a significant improvements in regulator WOB because the demand isn't there. Improvements in material technology applied to regulators is what I see as the next big overall improvement. Carbon nanotubes won't improve WOB significantly but will make regulators lighter and more reliable in salt water. That technology "could" make a huge difference in the strength-weight ratio of Scuba tanks though.

It is interesting that virtually everyone notices the WOB due to gas density when dry inside a chamber on air starting about 50M/165' on air. Not many divers notice it in the water, probably due to all the environmental distractions.

 

[Luis H]

There is always a lot of talk about Work of Breathing (WOB), but very little talk about the Perceived Work of Breathing. Only in very few rebreather studies and when I was talking to some of the research scientist at NEDU was Perceived WOB part of the conversation.

I will try to briefly explain the difference.

OWIC647 posted above the classical diagram showing the center of the lungs as the point in the water column where the actual WOB takes place and that is for the most part correct. But, we have no sensation of pressure at our lungs.

You can confirm this if you are using a snorkel on the surface. The WOB using the snorkel doesn’t feel any different if you are on the surface horizontal or vertical. Even do the lungs are deeper when you are floating vertically on the surface as opposed to horizontal, the snorkeler cannot feel the difference.

The reason is that the center of sensation is close to the back of your throat (there is a specific physiological name for this spot, but I can’t remember). I saw the breathing test dummies at NEDU and they all have their pressure probe (where pressure is measured) roughly on the back of the throat.

There are also articles on rebreather WOB where this is discussed and the reasons why the location of the counter-lung affects the Perceived WOB.

The actual work is performed by the muscles surrounding the pleural cavity (lung cavity) and the diaphragm (abdominal diaphragm), but we don’t really feel the difference in differential pressure in that region.


There are many other subjective issues that can affect the Perceived WOB, for example: how much did we pay for the regulator. OK, I am partially kidding.

But the reality is that humans are very poor actual instrumentation devices and we are often affected by a variety of side factors, many of which are very important, but are not necessarily directly involved with actual WOB. But they can affect the perception and when it comes to humans, the perception can be more important than actual “numbers”.

This all falls into the area of Human Systems Integration (HSI), Ergonomics, Human engineering, Human Machine interface, etc. At work I was asked to take on the responsibilities for HSI because I have a very limited knowledge on the subject of human engineering (which made me the local expert ), but I am quickly shedding that responsibility to a younger engineer who is actually taking some specific classes in the subject.

Some of the other perception factors on WOB of a regulator that I can mention are: how the air is delivered into the mouthpiece (for example a strong venturi jet versus even flow), the diver surroundings (for example, in air versus water), and there are many others less subtle that would require too much of an explanation to bring up at the moment.


In the last 40+ years we keep on talking about WOB, but little have actually changed in the actual WOB performance. The changes have been fairly subtle in the subject. There has been a lot of other changes in the diving kit configuration, but the mechanism and aerodynamics inside the regulator (demand valve) has changed very little.


OK, my explanation wasn't brief...

 

[EricTheDood]

the general consensus of which seems to be that it is quite mature technology and only incremental advances will occur in future.!

I'm firmly in the "incremental changes" camp.

Technology in consumer industries almost always trickles down from larger industries, such as defense and aerospace (where the $$$ is). No doubt that high pressure scuba tanks would not exist if there weren't a much larger industry for high pressure cylinders, e.g. welding gas and medical applications.

If we look at the manufacturing advancements in the last 20-30 years (new metallic alloys, carbon fiber, 3D printing, etc) none of that fundamentally changes the OC scuba regulator.

 

[Blasto]

Maybe this is true- or maybe there could be some quantum leaps in reg design ahead!
So, what specific advances would you like to see happen?

While WOB has always been the go-to metric of performance, I can't recall any time I found it an issue.

Personally, I'd rather see them go down the miniaturization and improved reliability route. Titanium regs didn't work out (oxygen - although the medical industry occasionally uses aluminum... safety not first, apparently), but ceramic/composite ones might. Even without that, some "final" design might emerge.

If it does, I'd expect to see no more than 2-3 sets of first stage internals, generally only one in use in any given region. There will still be a lot of brands and models, but they'll only differ in LP/HP port count and the logo. Ideally, even the o-rings will have sufficient lifespan that the regulator isn't serviced in routine use.

Second stages might get smaller and more resistant to freeflow, even with sand ingress.

 

[ams511]

The RAM does not require the same level of fine tuning to perform and we were all using plain backpacks which places the DH in a good position.

I learned to dive in 90 or 91, when double-hoses were mostly dive shop displays. When watching old videos of double-hoses in use (Sea Hunt, Cousteau, etc.), where the divers are using a cloth harness. It appears that the tank moves much more on the divers back than it does today (assuming a well fitting BC). I am not just talking about underwater fight scenes but during normal diving. Would this also affect breathing performance? In one of my older dive books it mentions where the regulators should sit for best performance.

 

[ams511]

While WOB has always been the go-to metric of performance, I can't recall any time I found it an issue.

Personally, I'd rather see them go down the miniaturization and improved reliability route. Titanium regs didn't work out (oxygen - although the medical industry occasionally uses aluminum... safety not first, apparently), but ceramic/composite ones might. Even without that, some "final" design might emerge.

If it does, I'd expect to see no more than 2-3 sets of first stage internals, generally only one in use in any given region. There will still be a lot of brands and models, but they'll only differ in LP/HP port count and the logo. Ideally, even the o-rings will have sufficient lifespan that the regulator isn't serviced in routine use.

Second stages might get smaller and more resistant to freeflow, even with sand ingress.

Scubapro did have and aluminum regulator for a while, the MK-20 and 25 Ultralight. I have one. The regulators had problems with corrosion and I believe at one point they were trading them in on new MK-25s. That is why the dive industry moved to titanium but as you pointed out, it is not the best material in an O2-rich environment. However it is fine for banked recreational nitrox.

Most first stages do use similar internals. For example the AL Titan first stage kits can but used for regs dating back to the old Conshelf series and before. Most first stage kits only vary by the number and size of o-rings. The seats and diaphragms are usually the same. Also if properly rinsed and stored most regulators can go much longer than a year or two before requiring a rebuild.

As far as second stage size goes look at a AL Micra, I am not sure they can get any smaller. As far as second stage weight goes, I don't see the problems with current designs. Underwater most are neutral to positive. The infamous "jaw fatigue" is more do to poor mouthpieces, divers biting too hard, and hose pull than the weight of the second stage.

The physics of regulators is well-understood, so most changes are going to be evolutionary rather than revolutionary.

 

[Luis H]

I learned to dive in 90 or 91, when double-hoses were mostly dive shop displays. When watching old videos of double-hoses in use (Sea Hunt, Cousteau, etc.), where the divers are using a cloth harness. It appears that the tank moves much more on the divers back than it does today (assuming a well fitting BC). I am not just talking about underwater fight scenes but during normal diving. Would this also affect breathing performance? In one of my older dive books it mentions where the regulators should sit for best performance.

I totally agree with your observation. There is a reason why the old harness was only used until the late 50’s. By the time the 60’s came around none of the manufacturers in the US are showing the original harnesses in any of the catalogs.

If you notice on my statement I specifically mention plain backpacks, not the original harnesses from the 1950’s. I have used the original harness a lot and the cylinder top moves side to side and also rotates some.

When I am with my vintage equipment collector friends and they start taking about how great the old harnesses are and how they hold the regulator next to your back, I just keep quiet and don’t say a thing. But I have seen plenty of pictures and videos where you can see the top of the tank moving side to side a lot.

The side to side motion is not as detrimental to DH regulator performance if the diver doesn’t roll at all, but that is not always the case. But, when you are doing some underwater knife fighting, you don’t pay too much attention to those details.

The reason the cylinder moves so much side to side with a traditional harness is because the shoulder straps are attached to a tank band down below the shoulder of the cylinder. They come to a point down on the actual cylinder, much lower than the tank valve or regulator.

The VDH backplate was specifically designed to solve this problem. I took some ideas from a very vintage double hose backplate and I designed it to fit the different modern wings, using modern dual tank bands. I located the shoulder straps as high as possible and used the concept of crossing the straps to control and restrain the lateral motion at the top of the cylinder.

The VDH plate is a small flat plate to keep the cylinder as close as possible to the divers back.

The modern backplate with the bend on the middle (designed for double tanks) tends to move the cylinder away from the diver. That is even worse if you use one of the single tank adapters. That concept can move a cylinder so far away from a divers back that I always see divers bending forward to carry the weight when they are walking to the water on a shore dive.



A well fitting BC, even a jacket BC, will work fine as long as the BC positions the regulator close to the diver and it fit snug enough that the tank and regulator doesn’t float away from the diver when you put air in the BC. If there is any separation between the tank and the diver or you are using a big diameter cylinder, that tends to move the regulator away from the diver. That is not good.

About 10 years ago, I used to use a simple BC jacket that I modified the shoulder straps and it worked great with my Phoenix RAM. It fitted snug and I used a crotch strap with it. It was the best simple BC that I had at the time.

The biggest problem with many modern BC (Jackets and some back inflate) is that they have too much padding and other material that moves the cylinder away from the diver. And if they are loose the cylinder will float up (away from the diver in a horizontal position) when the diver adds any air to the BC. I have seen a diver with a jacket BC with air in it and I could easily slip my fist between the diver's back and the jacket.

 

[Blasto]

Most first stages do use similar internals. For example the AL Titan first stage kits can but used for regs dating back to the old Conshelf series and before. Most first stage kits only vary by the number and size of o-rings. The seats and diaphragms are usually the same. Also if properly rinsed and stored most regulators can go much longer than a year or two before requiring a rebuild.

Yeah. I'm just looking forward to the ultimate step of completely standardized internals (because there's nothing left to make perceivably better, and nothing to be saved by making it worse), built out of something corrosion- and oxygen-resistant like ceramics, with non-degradable o-rings, so you never need to know the internals are there.

As far as second stage size goes look at a AL Micra, I am not sure they can get any smaller.

Probably not. Regs aren't cell phones... but cell phones and most other tech did evolve from technology-facing (big box, small buttons) to user-facing (just a really thin screen). There is a "smaller" to go to, the integrated reg used in Spare airs and such, just not good enough.