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Post by Linda on Dec 12, 2003 10:24:24 GMT -8
From "Let's Go Diving", an Illustrated Diving Manual by Bill Barada, Published by U.S. Divers Co., 3323 West Warner Ave., Santa Ana, CA. Catalog No. 7804-00, Copyright 1962, 4th Printing November 1965, page 29.
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Post by immadman on Dec 31, 2012 10:26:49 GMT -8
Thanks for the diagram, Linda! It makes the complicated (at least for me) idea of physics as it relates to diving and regs easy to understand for old, fat, simpleminded men like me who tend to be narced on the surface!!!
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Post by SeaRat on Jan 1, 2013 18:19:01 GMT -8
immadman, let's do a bit of the physics for that diagram. We know that in 33 feet of sea water, there is one atmosphere of pressure. That one atmosphere is 14.7 psi gauge at sea level. At 33 feet, it is twice that, or 29.4 psig. At 66 feet, 3 times the surface pressure, or 44.1 psig, and so on. Now, if we take that 14.7 psi in 33 feet, and divide it by 33, we get 0.45 psi per foot. If we then divide that by 12, we get 0.04 psi per inch. If you look at the top two diagrams of a diver in a level (supine) position, you can see for the double hose regulator there is about 8 inches of difference between the regulator and the center of the diver's lungs. That is 8 x 0.04 = 0.3 psi difference, both for inhalation and exhalation.
That 0.3 psi might not sound like much, but it is. It is the reason breathing through a snorkel when upright with the head completely underwater is difficult, and why someone with a great-breathing double hose regulator says it's like breathing through a straw. What happens here is that the regulator is put on a single tank with a conventional BC, and the regulator is right behind the head of the diver. In certain positions, it is over a foot above the center of the diver's lungs. As you now know, a foot is 0.45 psi. That is a lot of breathing resistance to overcome.
We have been talking only about inhalation resistance. Modern double hose regulators will almost breathe for you because of a design feature called "venturi action." This means that the air is shot down the intake hose, and this results in a partial vacuum in the chamber which keeps the diaphragm down. Air flows until the diver stops inhaling, and the buildup in pressure allows the diaphragm to go back to its original position, and air flow ceases.
Virtually all decent double hose regulators incorporate venturi design into their regulators. However, there are some of the original regulators (Healthways SCUBA, first and second generation; DA Aqualung, first generation in the USA) which do not have venturi designs. However, the DA Aquamaster, Mistral, Royal Aquamaster, Hydro Twin (Sportsways), and the AMF Voit equivalent regulators have venturi designs. Without venturi assist, the diver has to continue sucking at a specified amount to open and keep open the regulator's air flow mechanism.
So the double hose regulator needs to sit between the diver's shoulder blades, and as close to the diver as possible. This results in optimum breathing through these regulators.
John
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Post by sitkadiver on Jan 9, 2013 11:11:34 GMT -8
Not sure if this information is welcome, since we're focusing on the function of a double hose regulator, however, it is my undertanding that Emile Gagnon's first prototype regulator was a single hose.
The regulator looked like a single stage DH reg, with a single corrugated hose running from the tank mounted reg to the divers mouthpiece. On the side of the mouthpiece opposite the breathing hose was a valve that looked very much like a duckbill.
This setup freeflowed considerably when a diver was in any position other than head down. As a result, Gagnon changed the design to incorporate a second hose, that placed the exhaust valve very close to the 1st stage diaphragm.(That freeflow can still be experienced by a modern DH reg by having a diver lie on his/her back with the reg body below the mouthpiece.)
I believe it was Phil Nuytten who wrote that Gagnon thought the Calypso regulator was about as close to the pinnacle of regulator design as he could get. It was 2 stages, the first stage was balanced, the second stage was a downstream design and the second stage being located in the mouthpiece itself prevented freeflows. I'll have to look back into my HDS articles and other sources to be certain of the verbage.
In any case, as I look through my regulator collection, I cannot find a single one of my single hose regs that strays too far from the Calypso design. Not sure that bodes well for us DH fans, but it wold appear from an engineering stand point that Gagnon preferred the single hose downstream design to the DH design.
Now that I've said that, please don't ostracize me from the board.... HA HA (I hope)
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Post by nikeajax on Jan 9, 2013 12:26:05 GMT -8
DAVE, how could you... The only problem I have with SH'ers is how dry they breathe, okay they're noisy too, and they do obscure your vision, but, but... I totally dig on'em--really! Would love to have a Calypso-I, but have no intention of selling one of my kidneys to get one: they seem to fetch a pretty stiff price these days--UFF DA! Jaybird
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Post by SeaRat on Jan 9, 2013 18:43:55 GMT -8
Not sure if this information is welcome, since we're focusing on the function of a double hose regulator, however, it is my undertanding that Emile Gagnon's first prototype regulator was a single hose. The regulator looked like a single stage DH reg, with a single corrugated hose running from the tank mounted reg to the divers mouthpiece. On the side of the mouthpiece opposite the breathing hose was a valve that looked very much like a duckbill. This setup freeflowed considerably when a diver was in any position other than head down. As a result, Gagnon changed the design to incorporate a second hose, that placed the exhaust valve very close to the 1st stage diaphragm.(That freeflow can still be experienced by a modern DH reg by having a diver lie on his/her back with the reg body below the mouthpiece.) Yes, that is what happened, and is described by JY Cousteau in The Silent World. This is also the basis of his patent. I believe it was Phil Nuytten who wrote that Gagnon thought the Calypso regulator was about as close to the pinnacle of regulator design as he could get. It was 2 stages, the first stage was balanced, the second stage was a downstream design and the second stage being located in the mouthpiece itself prevented freeflows. I'll have to look back into my HDS articles and other sources to be certain of the verbage. In any case, as I look through my regulator collection, I cannot find a single one of my single hose regs that strays too far from the Calypso design. Not sure that bodes well for us DH fans, but it wold appear from an engineering stand point that Gagnon preferred the single hose downstream design to the DH design. Now that I've said that, please don't ostracize me from the board.... HA HA (I hope) I think you are talking about the exhaust valve being located in the diaphragm as making it pretty much ideal. That would be the original Calypso, and there are relatively recent Dacor single hose regulators too which incorporate the exhaust into the diaphragm. My AIR I regulator by Scubapro actually uses the entire diaphragm as an exhaust, and is perhaps the most effective use of this design. Gagnan actually designed more two-hose regulators too, like the single stage Overpressure Breathing and Mistral upstream design and the downstream design that AMF Voit ultimately incorporated into their Fifty Fathom regulator. www.google.com/patents/US2875756?pg=PA3&dq=Gagnan+dive+regulator&hl=en#v=onepage&q=Gagnan%20dive%20regulator&f=falseHe went on to develop a number of single hose regulator designs: www.google.com/patents?id=OJRJAAAAEBAJ&pg=PA1&dq=Gagnan+dive+regulator&source=gbs_selected_pages&cad=2#v=onepage&q=Gagnan%20dive%20regulator&f=falseYou can look up his influence on "Google Patents" and search for all of his designs. John
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Post by sitkadiver on Jan 11, 2013 11:02:01 GMT -8
John,
I was thinking of the later Calypso, but only becuase I do not possess the knowledge to know better. That style, that looks a great deal like the Conshelf regs, seems to have the same layout, lp stem and actuator that almost all other hockey puck regs possess.
That being said, the double hose in my mind still has several advantages: The bubbles are behind me, which is great when I'm taking pictures of tinkering with tools, I also think they're easier to work on since many of my single hose second stages are a pain to adjust due to not being able to get a 1/4 in. socket to fit inside the reg body. Other advantages for me are retaining the reg and not having to grop for it behind my shoulder should I lose it(rare, but it could happen again.)
Primarily for me, I'm finding it's a bit more comfortable to breathe from since the air entering my mouth is travelling slower and not wooshing in directly from the IP hose.
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Post by nikeajax on Jan 11, 2013 15:44:43 GMT -8
"Other advantages for me are retaining the reg and not having to grop for it behind my shoulder should I lose it(rare, but it could happen again.)"
Why haven't they brought neck-straps back? Yeah, you might get some sand or debris in it, but, since no one really does buddy-breathing any more... Gosh, on the rare chance you might need to, why couldn't you just unsnap the dang thing? From the way I see it, it would really help if you get smacked in the face accidentally, or somehow you lose consciousness, like hitting you head... 411-please!
Jaybird
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Post by sitkadiver on Jan 11, 2013 16:51:02 GMT -8
Sorta did..... Attachments:
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