Aqualung Mistral
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ScoobieDooo
Guest
Ahhh....Cracking Pressure...
ScoobieDooo:
Sort of. That's certainly a big part of what controls the WOB.
The way I understand it WOB boils down to how many "joules of work" -- that means there is a force (sucking) and movement (the valve opening) in the directon of the force -- is required for the valve to remain open for a given length of time.
It's measured in j/l (joules per litre) which I assume means they attach it to a machine that sucks a given amount of air through the reg (in and out) and then measures how hard it needed to work to do that.
And that's just about the limit of my knowledge on that topic. Anyone else?
R..
ScoobieDooo
Guest
Nope...that pretty much covers it. A guage (manometer) is attached to the 2nd stage which measures the amount of 'suction' required (in mercury - technically - even though the media now used is plain colored water) to open the 2ns stage valve.
Greg Barlow
Contributor
The WOB also includes the exhalation effort, which for substantial depths, is a large part of the overall effort needed to move the liter of gas through the reg. Some regs offer a low WOB by being on the verge of free flow while in a horizontal swimming position. This can easily lead to positive pressure breathing, and is an unnatural feeling.
Numerous tests have demonstrated that it takes at least 0.4j/l difference in WOB for a diver to accurately identify the variation. Due to case fault geometry, many regs cannot be set at a level below 1.25" without free flowing. I set all non-adjustable regs to have a cracking effort of around 0.10" more than what the CFG allows. This allows stable performance and relatively low WOB.
Greg
Numerous tests have demonstrated that it takes at least 0.4j/l difference in WOB for a diver to accurately identify the variation. Due to case fault geometry, many regs cannot be set at a level below 1.25" without free flowing. I set all non-adjustable regs to have a cracking effort of around 0.10" more than what the CFG allows. This allows stable performance and relatively low WOB.
Greg
ScoobieDooo
Guest
Sadly the old Aqua Master Double Hose Regs have a pretty high cracking pressure...
"Sadly the old Aqua Master Double Hose Regs have a pretty high cracking pressure..."
The WOB is the total breathing cycle effort in joules. Not just cracking force/pressure, not just "sucking" effort but also exhalation--the entire cycle.
Apparently you have not used a good double hose because while it is true the cracking effort is higher there is a large venturi effect that once begun pulls the large diaphram inward providing an excellent air flow. The effort of exhalation is also failry low on a good double hose. Therefore the total expended effort of a finely tuned Aquamaster is not that much more than a good modern regulator.
Further, you have heard it said that while breathing though your single hose regulator that you should "just breath normally". This is not the case with a double hose. Instead you should take longer deeper breaths and longer more complete exhalations. This reduces the number of times the cracking effort must be overcome for a given volume of airflow thus further reducing the actual work of breathing.
While I would not expect folks to run out and start rebuilding antique regulators and toss their new Apecks or Mares or whateverhaveya the fact is they worked and still work quite well and many superb divers including the inventor of modern diving, Cousteau, dived double hose units his entire career.
Modern diver training and most modern divers are not trained for double hose regulators, clearing them, buddy breathing and breathing technique are all a lost art. Not understanding something does not make it invalid. The Aquamasters and double hose regulators in general where supreme from the 40s and well into the 70s. Their performance was not as lacking as you may be led to believe and they can be dived safely and effectively with proper training in 2005 as easily as in 1965. N
The WOB is the total breathing cycle effort in joules. Not just cracking force/pressure, not just "sucking" effort but also exhalation--the entire cycle.
Apparently you have not used a good double hose because while it is true the cracking effort is higher there is a large venturi effect that once begun pulls the large diaphram inward providing an excellent air flow. The effort of exhalation is also failry low on a good double hose. Therefore the total expended effort of a finely tuned Aquamaster is not that much more than a good modern regulator.
Further, you have heard it said that while breathing though your single hose regulator that you should "just breath normally". This is not the case with a double hose. Instead you should take longer deeper breaths and longer more complete exhalations. This reduces the number of times the cracking effort must be overcome for a given volume of airflow thus further reducing the actual work of breathing.
While I would not expect folks to run out and start rebuilding antique regulators and toss their new Apecks or Mares or whateverhaveya the fact is they worked and still work quite well and many superb divers including the inventor of modern diving, Cousteau, dived double hose units his entire career.
Modern diver training and most modern divers are not trained for double hose regulators, clearing them, buddy breathing and breathing technique are all a lost art. Not understanding something does not make it invalid. The Aquamasters and double hose regulators in general where supreme from the 40s and well into the 70s. Their performance was not as lacking as you may be led to believe and they can be dived safely and effectively with proper training in 2005 as easily as in 1965. N
ScoobieDooo
Guest
Nemrod,
Well I dunno - I had rebuilt mine with all new parts from Reb's Parts and Dan's Vintage Scuba - I set IP around 140 psi as stated in Aqua Lungs Service Manual for the Aqua Master DA and had my demand lever as low as I could get it w/o freeflowing when the hose was higher than the box. I had all new valves, diaphargms, horseshow lever, gaskets, screws, HP and LP Seats, new cages and valves in the mouthpiece, etc. and in the water unless I was on my back it breathed like crap. Every part had been rechromed as well. She sure was a thing of beauty...
Well I dunno - I had rebuilt mine with all new parts from Reb's Parts and Dan's Vintage Scuba - I set IP around 140 psi as stated in Aqua Lungs Service Manual for the Aqua Master DA and had my demand lever as low as I could get it w/o freeflowing when the hose was higher than the box. I had all new valves, diaphargms, horseshow lever, gaskets, screws, HP and LP Seats, new cages and valves in the mouthpiece, etc. and in the water unless I was on my back it breathed like crap. Every part had been rechromed as well. She sure was a thing of beauty...
Well Scoobie, I think you did the rebuild?, and the IP is 110 in my manual and I think at a tank pressure of 500 PSI and such as that. This is the thing, if you don't like them, don't dive them, no one is forcing you into it. Some like them and others don't and there is nothing wrong with that. Some people don't like to dive at all, imagine that!
That said, my DA Aquamasters seem the most challenging to tune and I am still working with them. The Mistrals and Royals seem easier to set up. There are many subtle things that don't strike my attention at first but do now.
I learned to dive on double hoses in circa 66. I am fully aware of what they do and don't do well. I also have a range of gear spanning from the 50s until now.
The USD Mistral first on the left was purchased by my uncle in 1958 and given me in 1968 and dived many times. The remainder are recent purchases, all rebuilt by myself and all do just fine, especially the Royal Aquamaster front and center, it is as smooth as silk. The older Royal beside it with no hoses is not rebuilt yet. The old pre Mares Voit MR12 enjoys the esteemed company of the Aquamasters and Mistrals.
N, I don't breath the long hose, I breath two short ones
That said, my DA Aquamasters seem the most challenging to tune and I am still working with them. The Mistrals and Royals seem easier to set up. There are many subtle things that don't strike my attention at first but do now.
I learned to dive on double hoses in circa 66. I am fully aware of what they do and don't do well. I also have a range of gear spanning from the 50s until now.
The USD Mistral first on the left was purchased by my uncle in 1958 and given me in 1968 and dived many times. The remainder are recent purchases, all rebuilt by myself and all do just fine, especially the Royal Aquamaster front and center, it is as smooth as silk. The older Royal beside it with no hoses is not rebuilt yet. The old pre Mares Voit MR12 enjoys the esteemed company of the Aquamasters and Mistrals.
N, I don't breath the long hose, I breath two short ones
ScoobieDooo
Guest
Oh I liked mine alot - just couldn't get it to breathe well enough for me. I spoke to Dan at Vintage Scuba about mine at one time with ideas and suggestions to try. I had a frozen HP Seat at one time and repaired that. I used to go thru an AL80 in about 15 mins.
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