Post by SeaRat on Apr 15, 2005 17:39:32 GMT -8
Both of you (Buzz and Yankdownunder) bring up good points, but I think there are still some misunderstanding of the physics involved. Because the two hose regulator is a closed system, the diver's lungs cannot feel any difference between the mouth and the lungs. The only open part of that system is where the diaphragm is, and that's the point that matters to the lungs for a two hose system. The reason for the second, exhalation hose is that the pressure needs to be equilized between the diaphragm and the exhalation valve. If they are not equal...I'll let Cousteau describe the differences. When Cousteau wrote The Silent World, he described the development of modern scuba:
The implications of this influenced diving for all these years, and apply to both double- and single-hose systems, but differently. I'll discuss this after supper (wife's saying "Supper's done!").
John
We were dreaming about a self-contained compressed-air lung. Instead of Le Prieur's hand valve, I wanted an automatic device that would release air to the diver without his thinking about it, something like the demand system used in the oxygen masks of high-altitude fliers. I went to _Paris to find an engineer who would know what I was talking about. I had the luck to meet Emile Gagnan, an expert on industrial-gas equipment for a huge international corporation. It was December, 1942, when I outlined my demands to Emile. He nooded encouragingly and interrupted. "Something like this?" he asked and handed me a small bakelite mechanism. "It is a demand valve I have been worknig on to feed cooking gas automatically into the motors of automobiles." At the time there was no petrol for automobiles and all sorts of projects were under way for utilizing the fumes of burning charcoal and natural gas. "The problem is somewhat the same as yours," said Emile.
In a fgew weeks we finished our first automatic regulator. Emile and I selected a lonely stretch of the river Marne for a test dive. He stood on the bank while I waded in over my head. THe regulator furnished plenty of air without effort on my part. But the air rushed wastefully out of the exhaust pipe in the fashion of the Fernez gear. I tried standing on my head. The air supply almost ceased. I couldn't breathe. I tried swimming horizontally, and the air flowed in a perfectly controlled rhythm. But how were we going to dive if we couldn't operate vertically?
Chilled and disappointed, we drove home, analyzing the regulator's reason for such tricks. Here it was, a miracle of design, the first stage efficiently reducing one hundred and fifty atmospheres to six atmospheres, and the second control stage rationing that to breathing density and volume. Before we reached Paris we had the answer.
When I was standing up in the water the level of the exhaust was higher than the intake and that six-inch difference in pressure allowed the air to overflow. When I stood on my head, the exhaust was six inghes lower, suppressing the air flow. When I swam horizontally, the exhaust and intake were in the same pressure level and the regulator worked perfectly. We arrived at the simple solution of placing the exhaust as close as possible tothe intake so that pressure variations could not disrupt the flow. The improvement worked perfectly in a tank test in Paris.
The Silent World
Pagces 19 and 20 in the chapter titled " Menfish"
In a fgew weeks we finished our first automatic regulator. Emile and I selected a lonely stretch of the river Marne for a test dive. He stood on the bank while I waded in over my head. THe regulator furnished plenty of air without effort on my part. But the air rushed wastefully out of the exhaust pipe in the fashion of the Fernez gear. I tried standing on my head. The air supply almost ceased. I couldn't breathe. I tried swimming horizontally, and the air flowed in a perfectly controlled rhythm. But how were we going to dive if we couldn't operate vertically?
Chilled and disappointed, we drove home, analyzing the regulator's reason for such tricks. Here it was, a miracle of design, the first stage efficiently reducing one hundred and fifty atmospheres to six atmospheres, and the second control stage rationing that to breathing density and volume. Before we reached Paris we had the answer.
When I was standing up in the water the level of the exhaust was higher than the intake and that six-inch difference in pressure allowed the air to overflow. When I stood on my head, the exhaust was six inghes lower, suppressing the air flow. When I swam horizontally, the exhaust and intake were in the same pressure level and the regulator worked perfectly. We arrived at the simple solution of placing the exhaust as close as possible tothe intake so that pressure variations could not disrupt the flow. The improvement worked perfectly in a tank test in Paris.
The Silent World
Pagces 19 and 20 in the chapter titled " Menfish"
The implications of this influenced diving for all these years, and apply to both double- and single-hose systems, but differently. I'll discuss this after supper (wife's saying "Supper's done!").
John