First reg, need to buy two, rec diver

[halocline]

There are a number of factors you aren't taking into account....

I understand all about the cracking effort vs WOB, compression of the spring, diaphragm size vs force, etc.....but none of these factors would explain any relationship between balanced vs unbalanced poppets and diaphragm size, which was your original statement that I questioned.

All other things equal, larger diaphragm exerts more force on the lever than does a smaller diaphragm. Fine, we agree.....but it has nothing to do with whether or not the valve is balanced.

 

[halocline]

my understanding is that with a new HPR second stage, the double hoses can be tuned to a lower WoB and cracking effort than any "normal" style second stage on the market. Basically everything except the Xstream from Poseidon. I know the Kraken did it as I have seen the graphs, but I believe an upgraded Aquamaster can beat them as well

It's impossible to accurately compare WOB numbers between doublehose and single hose regulators in any way that has relevance to actual diving. The position sensitivity of doublehose regs makes them perform VERY differently than single hose regs.

The new 2nd stage that Luis and Bryan developed is definitely an improvement over the stock 2nd stages in the aquamasters, but it doesn't change anything about the position sensitivity. That's inherent in the doublehose design and is responsible for how they feel in the water. For some divers there's nothing like it, for others it's not enjoyable. I love my PRAM, but I would not begin to compare it better or worse than a quality single hose reg. It's just very different. That's what happens when the air depressurizes several inches from your mouth instead of less than an inch.

 

[Luis H]

Hi Halocline
You need to try an Argonaut with the new flow diverter in the DSV mouthpiece and the HPR adjusted for maximum venturi flow and then come back and we can talk about it. The cracking effort is still affected by the water column (that is basic physics), but that becomes a bit secondary.
Position is still important with a DH, but so is breathing technique, etc.


I think what Akimbo is trying to say that with a large diaphragm is that the demand valve doesn't need all the other refinements to get a low cracking effort. I am OK with calling it brute force.

Putting the water column aside, I can easily adjust the HPR in an Argonaut to 0.2 inWC anytime I want to (and it is extremely stable with no leaks or free-flows on dry land). But I have to de-tune it to about 0.6 (or higher) to avoid a little free flow in the water (due to the water column pressure differential).

The exhaust valve is right in front of the demand valve diaphragm and it is 1 inch in diameter (0.5 inches radius). The cracking effort need to be just a bit higher than the height of the exhaust to avoid the water column pressure differential from causing a small continues free-flow.


One big advantage of the "brute force" approach is that the tuning is not that critical. I set the lever height with a gauge, with a gap between the lever and the diaphragm. The new supper flexible large diaphragms have a large range of travel. Since there is a gap between the lever and the diaphragm, the regulator doesn't go out of tune as the soft seat gets an impression. That means I don't have to do any adjustments or change seats for many years and the measured cracking effort has stayed consistent at 0.7 inWC for several years now on all of my Argonauts.

 

[george_austin]

Vaping is stinking up the store!

Now I've heard everything.

 

[halocline]

Since there is a gap between the lever and the diaphragm, the regulator doesn't go out of tune as the soft seat gets an impression. That means I don't have to do any adjustments or change seats for many years and the measured cracking effort has stayed consistent at 0.7 inWC for several years now on all of my Argonauts.

Hi Luis, I do want to try an Argonaut, and hopefully I'll have a chance to try one of yours sometime. I'm sure they're even better performing than the PRAM, which as you remember was a major improvement in itself.

I'm not sure how the gap between the lever and the diaphragm affects the long term tuning. If there were enough contact between lever and diaphragm while the reg was unpressurized, the diaphragm would be acting as a de-facto seat saver. Wouldn't that prolong seat life? My PRAM also has a slight gap between lever and diaphragm, as do most of my single hose 2nd stages. Maybe the longevity of your tuning has more to do with the seat material and general 2nd stage design, which results in it not being as sensitive to small changes in the seat as it wears; my PRAM often sits for long periods of time and I haven't tuned it in years.

Regarding the diaphragm size and balancing, Akimbo said that "balanced second stages allow smaller diaphragms" and that's not a true statement. As I mentioned, we can all agree that all other things equal, a larger diaphragm will apply more force to the lever for an equal pressure differential. But that has nothing to do with balancing, and it's exactly the same effect on balanced and unbalanced 2nd stages.

Certainly there are all sorts of design factors that have resulted in 2nd stages getting smaller over time, and most modern high performing 2nd stages are balanced. But those two characteristics are independent of each other.

 

[george_austin]

It's impossible to accurately compare WOB numbers between doublehose and single hose regulators in any way that has relevance to actual diving. The position sensitivity of doublehose regs makes them perform VERY differently than single hose regs.

The new 2nd stage that Luis and Bryan developed is definitely an improvement over the stock 2nd stages in the aquamasters, but it doesn't change anything about the position sensitivity. That's inherent in the doublehose design and is responsible for how they feel in the water. For some divers there's nothing like it, for others it's not enjoyable. I love my PRAM, but I would not begin to compare it better or worse than a quality single hose reg. It's just very different. That's what happens when the air depressurizes several inches from your mouth instead of less than an inch.

The only single hose regulators I have that match the comfort and breathability of my tuned Phoenix / HPR / DBE equipped Royal AM or even my 62 Voit V66 with Phoenix and DBE is the Conshelf XIV and AMF MR12 II.

I've been trying to get comfortable with my new Mk25 + G260 and that regulator IMO is junk compared to all four listed above. Mechanically, I'm sure it's a fine regulator but it's just a massive PITA and a distraction comfort wise

 

[Bryan@Vintage Double Hose]

One of the often overlooked components in determining the ease of breathing in a second stage is the design/compound of the diaphragm. Large or small if the diaphragm is too flexible or not flexible enough or the profile is not correct performance will suffer.
It's easy to put racing stripes on a regulator or associate catch phrases to internal components but until it's subjected to testing by an independant source with no vested interest in being good or bad it's all just selling the sizzle not the steak.

It's been said many times that a regulator that costs 10x as much as it's competition will not give you 10x the dive enjoyment. Most regulators on the market today will serve 90% of the divers in the world just fine. The rest is up to the service and customer support folks to drive the brand and earn customer loyalty.

 

[Couv]

Since there is a gap between the lever and the diaphragm, the regulator doesn't go out of tune as the soft seat gets an impression.

I learn something everyday.

If there were enough contact between lever and diaphragm while the reg was unpressurized, the diaphragm would be acting as a de-facto seat saver.

Yes, but my guess is the gap prevents any tension the diaphragm might exert on the spring/poppet/seat assembly when in use; therefore the hard and soft seat nestle and maintain a better seal.

BTW Halo, I won't be using my Kraken until November, so you are welcome to borrow it until then. It has the DSV and it tuned per Luis.

 

[halocline]

Large or small if the diaphragm is too flexible or not flexible enough or the profile is not correct performance will suffer.

Hi Bryan, hope all is going well. Assuming a rigid plate in the middle (like most have), how would a 'too flexible' diaphragm cause performance to suffer? I can certainly see not flexible enough causing problems, but not too-flexible.

 

[Bryan@Vintage Double Hose]

Hi Bryan, hope all is going well. Assuming a rigid plate in the middle (like most have), how would a 'too flexible' diaphragm cause performance to suffer? I can certainly see not flexible enough causing problems, but not too-flexible.

Around 2005 when I was trying to reproduce the main diaphragm for the USD double hoses I knew that the improvements in materials would be key but since there were no actual specifications for them getting an accurate durometer reading from a 50 year old sample was near impossible so I had to guess. The first samples I had made showed no marked improvement in cracking effort over the originals. I knew something was amiss. I had the mold modified and samples were made with a thinner sidewall and the readings using those were a drastic improvement.....I should have left well enough alone but I convinced myself that if a little was good then a lot must be better and I had the sidewall made even thinner....And when I tried those I found that the cracking effort went back up. After a lot of midnight oil and trial and error I figured out that the material was so thin that there was too much stretch in the sidewall causing a lag before enough force was applied to the center disc on the lever. I proved it out a few other ways but needless to say it was an expensive experiment. Dome height, sidewall angle and durometer are a tricky business.
The Argonaut Kraken main diaphragm is actually a cross between the USD and the LaSpirotechnique designs.