breathing effort difference between 2 first stages...help

[herman]

Herman, I don't agree with that. It's true that a balanced 2nd is less reactive to IP differences than an unbalanced, but a 20 PSI difference would definitely be noticeable. You still have a mechanical spring pushing the seat closed; I would venture a guess that most balanced barrel-poppet regs have about a 50% downstream bias. It would be easy to measure a SP s-wing poppet for seat diameter (actually orifice interior diameter) and diameter at the balance chamber end with a micrometer and calculate the surface area of each.

A few PSI, I definitely agree, would not be noticeable on a balanced 2nd, and I also agree that the difference is likely to be much more pronounced on an unbalanced 2nd, which this one could be. In fact, I looked up the HOG website and this is the 2nd stage that came up, it does not say balanced so I would assume it's unbalanced.

HOG (HIGHLY OPTIMIZED GEAR) SECOND STAGE TECHNICAL REGULATOR BY EDGE

Maybe.... &^$%&^%$!! another project.
It may be easier to just measure the cracking pressure while varying the IP....guess I have something to do later today.

 

[Nemrod]

You know, not all regulators are created equal, some don't breath as well as others. Things like diaphragm size, stiffness and pliability, mechanical leverage, state of tune, venturi efficiency or lack thereof. I have several dozen different single hose regulators including classic and modern regs like the Legend, Titan, Titan LX Mares MR, Voit MR12II, ScubaPro R190, ScubaPro R109, Calypso, Conshelf, Tekna T2100, T2100B, Omega II, Oceanic and despite considerable effort spent on them, some simply do not breath as well as others.

N

 

[halocline]

Sure, but he's talking about moving a 2nd stage from one 1st stage to another, so it's definitely an IP issue if cracking effort is substantially different. There's nothing else it could be unless something is wrong with the 1st stage that's resulting in higher cracking pressure. Especially since it appears that the hog 2nd stage is not balanced, it's almost certainly very IP sensitive.

 

[JKSteger]

Funny about the air balanced spec on the HOG reg. Some sites say air balanced while others don't. Maybe Chris will chime in and let us know.

As far as 2nd stages go, it funny that MY (read, I have owned at some point in time) favorate and best breathing regs have been:
1. Mares Abyss
2. Apeks AT50
3. Dacor Viper
4. Scubapro G250 / Balanced Adjustable's
5. HOG

It's funny, I think the Abyss is NOT air balanced but was my best breather ever. Also that the Viper is inexpensive and not air balanced and it's been a great breather as long as it's adjusted right.

Maybe the 2nd needs to be adjusted using the same like the Viper. I remove the LP hose, press the purge, insert a hex wrench and move about an quarter counter clockwise to make breathing easier, then test. If it free flows, I make a very minor adjustment to the right until it doesn't free flow anymore.

Jeremy

 

[Bubbletrubble]

Sure, but he's talking about moving a 2nd stage from one 1st stage to another, so it's definitely an IP issue if cracking effort is substantially different. There's nothing else it could be unless something is wrong with the 1st stage that's resulting in higher cracking pressure. Especially since it appears that the hog 2nd stage is not balanced, it's almost certainly very IP sensitive.

@mattboy: I understand what you're saying. An unbalanced second stage is going to be more sensitive to IP changes than a balanced second stage.
Despite the glaring omission on the Edge/HOG website, I believe that the second stage is balanced. There was a thread in October 2008 here on SB in which Phil Ellis (Divesports.com) made a post regarding the HOG second stage design. Unless the design was drastically changed in the last year, the HOG second stage is, in fact, balanced. I hope that, at some point, an exploded parts diagram and technician repair manual will be posted on the Edge website so that we can see for ourselves.

 

[halocline]

Bubbletrouble, I would not be surprised if you're correct, I was just going on what the HOG website said. (or more accurately did not say!) It's hard to imagine a marketing department missing that one, but you never know.

 

[herman]

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.

 

[halocline]

Herman, you're a wild man for doing that experiment. So it's half an inch of difference in cracking pressure over 40PSI, I've got to say I stand corrected. 1/4" over 20 PSI drop, it's noticeable but pretty subtle, nothing anyone would complain about.

Given this and the OP's description, I'm betting that the HOG 2nd stage is not balanced, at least not in the same way that the SP barrel poppet regs are.

 

[LeadTurn_SD]

Funny about the air balanced spec on the HOG reg. Some sites say air balanced while others don't. Maybe Chris will chime in and let us know.

As far as 2nd stages go, it funny that MY (read, I have owned at some point in time) favorate and best breathing regs have been:
1. Mares Abyss
2. Apeks AT50
3. Dacor Viper
4. Scubapro G250 / Balanced Adjustable's
5. HOG

It's funny, I think the Abyss is NOT air balanced but was my best breather ever. Also that the Viper is inexpensive and not air balanced and it's been a great breather as long as it's adjusted right.

Maybe the 2nd needs to be adjusted using the same like the Viper. I remove the LP hose, press the purge, insert a hex wrench and move about an quarter counter clockwise to make breathing easier, then test. If it free flows, I make a very minor adjustment to the right until it doesn't free flow anymore.

Jeremy

Hi Jeremy,

You're right, the Mares Abyss is an unbalanced, "classic downstream" 2nd. It does breath really well when tuned properly (it is still my favorite).

Best wishes.

 

[Nemrod]

The Mares has the venturi assist tube and it is a very effective one as developed originally in the Voit MR12II. Properly tuned these unbalanced regs can breath with the very best today.

N