breathing effort difference between 2 first stages...help

[John C. Ratliff]

I am pretty sure the HOG is balanced as well. In any case I had a SP G200B on the bench so I ran though IPs ranging from 100 to 140 using a USD Conshelf for a first stage. I ran it several times and charted the results on my manometer as best as I could. While I was at it I also did an old Sherwood Magnum. Here are the results:

IP.............cracking pressure G-200B......Sherwood
140......................................0.625............1.25
130..................................... 0.75 ............ 1.50
120..................................... 0.875 ...........2.0
110 .....................................1.00 ............ 2.25
100..................................... 1.125............2.50

The Sherwood cracking pressure difference would be quite noticeable but the SP is less than 1 inWC across the 40 psi range I ran it through which is way out of the range I would expect even on an unbalanced first stage. It did not drop below 1.125 inWC even at 100 psi, still a passable cracking pressure.

Apparently, the diving equipment companies have been making a lot of noise about having a balanced second stage. What function does this "balancing" perform? I think it is more a marketing technique than any engineering feat.

Now, if you look at the cracking effort above, you will see the Sherwood regulator at just over an inch of water column suction effort and just over a half inch with the interstage pressure of 140 psig. The Sherwood regulator would probably be better at a slightly higher interstage pressure, as all this says is that the spring tension is that much greater than the interstage pressure as it acts on the seat. I have several regulators (Calypso and Dacor Pacer) which have a cracking effort of 1/2 inch (0.5 inches) of water column, and these regulators are over twenty years old. The Calypso is also an unbalanced second stage (the Pacer may also be, but I'll have to look inside to be sure). The balancing includes the seat holder going through an O-ring on the second stage (see the second stage animation in Wikipedia). If you look at this animation, you will see several additional sources of potential friction introduced into the second stage. If not serviced regularly, and well lubricated, this second stage can actually preform worse than the old unbalanced second stages.

How do I know that my Calypso second stages have less than 0.5 inches of cracking effort? Well, in certain orientations, they will leak air a bit. Dacor got away with very low suction effort without the leaking in the vertical plane by using two smaller exhalation valves, rather than one larger exhalation valve. If you will look at this Wikipedia diagram of the second stage, you will see that if you orient the regulator with the diaphragm down, the top of the exhalation valve will be over half an inch from the center of the diaphragm.

So what I am saying is that while the first stage being balanced is very important to performance, because you can balance the interstage pressure against the spring pressure of the second stage, there is not that kind of fluctuation difference between the air pressure in the mouthpiece (pressure of the surrounding water) and the air pressure of the intermediate stage (which remains constant with a balanced first stage). In short, you are being sold a bill of goods.

SeaRat

 

[dumpsterDiver]

Maybe there's something wrong with the oceanic 1st stage then, like a clogged filter. Who knows.

That's my bet from reading all this.

 

[herman]

John, you might want to look at the numbers again, a bill of goods it's not. Now I certainly agree that an old USD or Dacor (the Pacer is not balanced- reguardless of what is printed on it) can be tuned to crack at fairly low pressures as could the Sherwood in the example, but minimum cracking pressure was not what the experiment was about, it was to determine the effect of balancing has on the cracking pressure of a balanced second stage as IP changes. A quick look at the numbers makes it clear that it works. The balanced second that I used had a total shift in cracking pressure of about 1/2 an inch as opposed to the unbalanced Sherwood which had a 1.5 inch shift or 3 times more than the balanced second. Clearly the balancing is working. To the average diver a 0.5 difference is not that noticable but a 1.5 difference is. Now I do agree that it is not necessary to balance both stages, that becomes redundant. Farther I would agree that a balanced first stage coupled with an unbalance second stage with a cracking pressure adjustment (SP 109 for example) is a better choice from a durability standpoint but balancing a second stage is def not just marketing.

 

[JKSteger]

me too. The IP on the D12 is more consistent than the IP on the PX3, "but" the PX3 has great flow, with a balanced second it shouldn't be a issue. They are both good first stages.

I used and still have loaned out PX3's with GT3's as my personal tech regs when I was a Oceanic Rep., so I like them and have confidence in them.

Chris, I will try to bring it by next week and let you have a look at it. I can leave it for you if I get a chance to make it by earlier.

Now you know I'm going to wind up getting the sealed HOG first anyway but this is just for couriosity sake...

Jeremy

 

[Couv]

I'm surprised that HOG's own website does not described a balanced 2nd stage as such. That's a pretty big oversight, unless I missed something obvious on the page.

no dude, you didn't miss anything, I did. <http://www.scubaboard.com/forums/images/smilies/Standard%20Smiles/04.gif>

fixed now.

This is what this board is all about. Thank you Chris for listening and well done to you Matt for making a difference.


OK ladies and gentlemen, place your bets:

Unless the IP is really low, like around 110 psi or less, I say a restriction of some sort in the first stage. (clogged filter, foreign object, corrosion, etc) Why? The OP said the cracking pressure was about the same when hooked up to either regulator-that points to a flow problem.

Couv

 

[shogan]

If Chris had seen or known about this I would have earlier.

Teh HOG is balanced.

You live 20 mins away from where I do, less than a hour from where I work. I will be happy to help you out, not only am I the EDGE guy but I have taught the service clinic for the other regs you mention/have (Viper First stage should be d12 or d16 and the PX3 from Oceanic)

Edge/Hog has some fine people working for them.

 

[Bubbletrubble]

OK ladies and gentlemen, place your bets:

Unless the IP is really low, like around 110 psi or less, I say a restriction of some sort in the first stage. (clogged filter, foreign object, corrosion, etc) Why? The OP said the cracking pressure was about the same when hooked up to either regulator-that points to a flow problem.

My guess: Colonel Mustard in the Billiard Room with the candlestick. Oops! Wrong game.
I bet it's a clogged filter in the first stage. Hopefully, the OP can just replace that part and see whether reg performance changes.

 

[LeadTurn_SD]

Edge/Hog has some fine people working for them.

1+

I think it is amazing and terrific that a manufacturer takes the time answer questions here. (I'm a happy HOG customer by the way ).

Best wishes.

 

[cerich]

1+

I think it is amazing and terrific that a manufacturer takes the time answer questions here. (I'm a happy HOG customer by the way ).

Best wishes.

I have to, a few years back it was my idea to have a manufs area on Scubaboard...

Plus I enjoy it.

 

[John C. Ratliff]

John, you might want to look at the numbers again, a bill of goods it's not. Now I certainly agree that an old USD or Dacor (the Pacer is not balanced- reguardless of what is printed on it) can be tuned to crack at fairly low pressures as could the Sherwood in the example, but minimum cracking pressure was not what the experiment was about, it was to determine the effect of balancing has on the cracking pressure of a balanced second stage as IP changes. A quick look at the numbers makes it clear that it works. The balanced second that I used had a total shift in cracking pressure of about 1/2 an inch as opposed to the unbalanced Sherwood which had a 1.5 inch shift or 3 times more than the balanced second. Clearly the balancing is working. To the average diver a 0.5 difference is not that noticable but a 1.5 difference is. Now I do agree that it is not necessary to balance both stages, that becomes redundant. Farther I would agree that a balanced first stage coupled with an unbalance second stage with a cracking pressure adjustment (SP 109 for example) is a better choice from a durability standpoint but balancing a second stage is def not just marketing.

Herman,

I think that is my point--you only need a balanced second stage if you have an unbalanced first stage. And even if you do, you will still get more fluxuation of cracking pressure than you would with a balanced first stage and an unbalanced second stage. The latter combination can be tuned within a few psig of by the IP, and it will not vary with varying tank pressure. This technology has been in use since the 1960s. It is still my contention that if a regulator has both a balanced first stage and a balanced second stage, the diver is being sold something (s)he doesn't need.

SeaRat