Over breathing -- common?

[halocline]

I'd be careful about assuming your regulator is not supplying anough air. Even a lowly 30SCFM 2nd stage, on full purge, would theoretically be capable of emptying an AL80 in 3 minutes. I have a strong suspicion that the tank valve is the primary limiting factor in flow rates.

OTOH, there are lots of sensory differences in the way regs deliver air, and you might find that you enjoy diving more with a higher performance reg, and that's enough reason to buy one. One other thing to be careful about is the assumption that "contemporary" regs will breathe better than older ones. I would doubt that you would ever find a reg that felt better to breathe than a well tuned MK5/balanced adjustable (or G250, or D400) and those regs can be decades old.

Although I'm not the expert that some of the other guys are around here, I'm starting to become convinced that reg design "improvements" over the last couple of decades have been motivated by marketing decisions, patents running out, and other economic factors, rather than true performance improvements.

 

[beachnik]

But do understand, even with a high performance regulator, that turtle is still going to kick your ass if he wants to.

Well AWAP, once again, you've hit the nail on the head. Your intuition is flawless. It is, more often than not, a turtle. I avoided mentioning this for fear that people would jump to the conclusion that I'm a 'marine life harasser'. I don't touch them! (anymore). I give them a reasonable amount of space. They allow me to cruise with them - it's their decision.

One of my dive buddies has a Gates housing permanently attached to his hands. When we happen upon a turtle, I become the 'turtle wrangler' - I swim out to the far side and try to get ahead of the the turtle - to coax him back towards the camera. I try, almost always unsuccessfully, to get the turtle moving in an arch around my buddy - I know how hard it is for someone to swim fast with both hands gripping an over-sized metal shoe box. Also, with a diver near the turtle (in the view finder) it helps give perspective to the size of the turtle. And most importantly, all of these shenanigans increase my chances of getting into the video! Unfortunately, my pal is wise to me and he edits me out almost every time! (Oh, beachnik, I must have forgotten to press the record button...yeah, yeah, yeah)

; )

 

[paulwlee]

Lots of people have something to say about the Conshelf - just nothing about max flow rates of the SE2.

I'm pretty sure that the Conshelf SE2 has a high enough flow rate for anything a single diver may encounter.
There are many dimensions to a regulator's performance besides maximum flow rate.
If two regulators have the same flow rate but with one it takes more effort to initiate this flow, then you will get less air when you are exerting yourself and breathing fast and hard. So you need to take into account work of breathing (WOB), and then there is also the subjective element.

The Conshelf SE2 second stage is a very simple downstream valve, and I suspect 90% of the difference in performance with higher performing regulators comes from this and a more modern design balanced second stage.

 

[Luis H]

You can also have a huge difference between a regulator that has been "properly serviced" and one than has been fined tuned. This is particularly the case with a simple regulator like the Conshelf second stage.

Most technicians will err in the side of avoiding a free flow rather than fine tuned for max performance. If they fine tune the regulator it is more likely to come back early due to a free flow once the seat breaks in. A good tech can estimate how to de-tune just the right amount, but there is always a bit of guess work.

One of the major advantages of the modern pneumatically balanced second stage is not its over all performance, but its ability to maintain than performance and be less susceptible to variations such as IP and time from last service.



I do agree with mattboy, in that some of the best performing regulators have been around for at least a couple of decades, the Scubapro D400 and Balanced adjustable are just two examples.

No modern regulator can really be fined tuned better than the D400 just because of the distance from the exhaust to the center of the diaphragm. Mechanically many regulators could, but they would tend to free flow when the top edge of the exhaust was higher then the center of the diaphragm.


The flip side is that if a regulator is tuned to be too sensitive, it could become a bit unstable and tend to bubble under minor variations. This when an adjustable second stage is very desirable.

 

[beachnik]

I'm pretty sure that the Conshelf SE2 has a high enough flow rate for anything ..... and I suspect 90% of the difference in performance with higher performing regulators comes from this and a more modern design balanced second stage.

I'm not sure I follow. Are you saying that a simple solution might be to keep the 1st and get something like an Aqualung Titan LX 2nd?

(if I could get a lot of improvement out of just replacing the 2nd, I'd probably stick with an Aqualung 2nd, if for no other reason then simplifying the service end of things)

 

[beachnik]

Most technicians will err in the side of avoiding a free flow rather than fine tuned for max performance.

I was wondering if that might be it. In fact I called the shop that serviced it a few months ago. They vaguely suggested that I should have it serviced again - at my expense. (I'm not complaining about that, they're not getting rich off this stuff. And before my last service, I didn't give them any info about how I wanted it tuned.)

I do agree with mattboy, in that some of the best performing regulators have been around for at least a couple of decades, the Scubapro D400 and Balanced adjustable are just two examples.

No modern regulator can really be fined tuned better than the D400 just because of the distance from the exhaust to the center of the diaphragm. Mechanically many regulators could, but they would tend to free flow when the top edge of the exhaust was higher then the center of the diaphragm.

Not to worry. Before proceeding to the 21st Century, I thought I'd linger a while with one foot in the 20th. I'm over there on ebay trying to 'snipe' mattboy on an MK10 and/or a G250. My 'saved searches' include MK10, G250, D350, D400, etc. Oh sh#t, now I've revealed my hand.

 

[halocline]

I'm over there on ebay trying to 'snipe' mattboy on an MK10 and/or a G250. My 'saved searches' include MK10, G250, D350, D400, etc. Oh sh#t, now I've revealed my hand.

Oh, that was you, eh?

Actually I've just bought a few recently to get some more experience rebuilding, dive them for a while and then pass them on to friends. I already have too many, so you might have done me a favor. As long as we're on the subject, I would suggest avoiding any auctions by "allegroauctions." I bought a MK5 from him, looked great in the photo, he sent me a different MK5, one that was pretty beat up and corroded. He took it back, but it was still a waste of time.

 

[red_barbarian]

The flow rates quoted I believe are for the steady state condition. The way I understand the second stage to work is the drop in pressure caused by the breathers inhalation effort induces enough pressure differential on the two side of the diaphram to cause the "cracking" of the diaphram. This is aided by means of a spring that is adjustable in it's "cracking" pressure. In the second stage there are in essence 2 springs. The first is the "rubber" diaphram and the second is the metal spring that is adjusted behind the diaphram. Spring behavior when subjected to long time periods behaves in a nice linear fashion (Hooks Law). Unfortunately elastic materials(never follow Hooks Law) and metal springs when subjected to impulse conditions stop reacting in a linear fashion. The stronger the intantaneous impulse the more resistance that will be encountered. A simple analogy (and not entirely accurate due do hydraulics in them as well) is the behavior of car springs. They dampen the force thru resistance, encountered as your car hits bumps in the road. In regulators the designers are going to attempt to mitigate this behavior but the harder the breathing rate the more like you are to encounter the effects of the instaneous impulse component of the spring equations. See: Dirac Delta funtions for math based explanation. In addition the frictional components in air flow will grow as impulse demand grows as well as the increase in overall effort to pull more gas through the same size "pipe". This leads to momentary lag in air being delivered to the lungs, and the perception of resistance. The larger the lung capacity and the stronger the human diaphram exerting the force will exacerbate these conditions. An interesting experiment would be to don a heart monitor and drive your heart rate to 95% of known Max for a period of at least 5 minutes. This is usually sufficient to induce close to VO2 max consumption, use a subject w/ a lung capacity of over 5 liters. I'd bet if you hooked them up to a regulator at that point it will be spit out in a hurry as unable to deliver enough air. A heavily loaded diver should be okay, but a panicked diver will encounter this situation. The above leads me to beleive that under severe loads a well conditioed diver is worse off in a panic situation than a poorly conditioned one. The heavily loaded diver will obviously be far better off being well conditioned as a better user of the available O2 in the gas stream.

 

[beachnik]

I would suggest avoiding any auctions by "allegroauctions." I bought a MK5 from him, looked great in the photo, he sent me a different MK5, one that was pretty beat up and corroded. He took it back, but it was still a waste of time.

Thanks for that tip. In a previous life, I did a lot of digital retouching/compositing. So, I'm kinda sensitive to imagery. The first thing I noticed about "allegroauctions" stuff was what terrific condition everything seemed to be in (I also noticed that someone had open the photos, reset the highlight and shadow, adjusted the contrast, and boosted the color saturation...hmmm, if they're willing to do all that work, might they be tempted to go further?). I saw an MK5 that looked like it just rolled off the production line. A metal R109 that looked brand new.

After looking at the images closely, I decided that they were not 'retouched' (no cloning). But with so much old stuff that appears to be in mint condition, I wondered if he had one photo of a mint MK5 (et. al.) and kept using that same photo every time he got a new MK5. Again, I'm not saying he did it, I'm saying it was a kind of gut reaction. But from what you're saying, it sounds like that's what he's doing.

Thanks again. I'll stay away from him.

 

[Luis H]

I'm not sure I follow. Are you saying that a simple solution might be to keep the 1st and get something like an Aqualung Titan LX 2nd?

(if I could get a lot of improvement out of just replacing the 2nd, I'd probably stick with an Aqualung 2nd, if for no other reason then simplifying the service end of things)

IMHO, that is not a bad idea. You are correct about the issue of servicing a mixed regulator, but that is easily solved…learn to service your own gear and then you can fine tune it to your own taste.

I know this is easily said than done. There is very little in the way of courses for servicing gear. It is too bad we are not back in the early 70’s. I used to teach a the regulator repair class as part of our advance scuba class. It was only about 4+ hours, but it was a good start.


I personally consider your Conshelf first stage one of the best (and its derivative like the Titan). My wife’s regulator is a Titan first stage with a D400 second stage. IMO there is one of the best performing single hose regulators available.

For a save a dive regulator I normally carry a Titan first stage with a Scubapro Balanced Adjustable second stage. I also have another Titan first stage adjusted to an IP of 170 psi for my Poseidon Cyklon second stages.

But, the regulators that I actually dive most of the time are Phoenix Royal Aqua Masters or a Royal Aqua Master double hose regulator. The Royal was the regulator that introduced the balanced first stage that eventually came in the Conshelf and most of Aqua Lung regulators.

Oh, that was you, eh?

Actually I've just bought a few recently to get some more experience rebuilding, dive them for a while and then pass them on to friends. I already have too many, so you might have done me a favor. As long as we're on the subject, I would suggest avoiding any auctions by "allegroauctions." I bought a MK5 from him, looked great in the photo, he sent me a different MK5, one that was pretty beat up and corroded. He took it back, but it was still a waste of time.

That is a good way to go and I bet you make good friends that way too.

You ought to start playing with some double hose regulators. It is a lot of fun. A lot to tinker with to play with performance, etc.