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Hello David As for the bag collapsing and restricting flow in a heads up orientation you are correct, the bag would cause a restriction, but my primary interest in making an o2 rebreather is not for diving. I forsee using the rebreather on the surface prior to and between dives to reduce subsequent deco times. I also would like to be able to provide an adequate volume of gas in the event of a long boat ride back to a chamber. I ordinarily dive from a 5 meter inflatable, extra cyclinders of o2 are inconvenient. If this design isused for IWR you run an L shaped perforated non collapsable tube in side the bcd bag from the lower left rear of the bcd (where the co2 rich gas leaves the bag to enter the scrubber) up the inside of the bcd with the foot of the inverted L reaching across both shoulders. Purging the bag is easy with reg in mouth designs, you breath in through your mouth and out through your nose and mask. If you are using a full face mask grab the exhaust hose and crimp it over your exhaled breath will blow out around the mask. When the bag is empty you manually refill it. Purge intervals are discussed in "oxygen and the Diver" by Kenneth Donald for his oxtox experiements, the subjects had no prior nitrogen build ups though. How you would alter your purge times to account for the accelerated rate of N2 offgassing from various dive profiles without the use of an o2 gauge beyond me. > >I have some questions regarding rebreather design myself. After reading the >below, I started wondering about breathing bag design. How do you make sure >that you can always suck the gas out of the bag, especially in the example below >where the exhaust is on the bottom of the bag/BCD (could not the vinyl collapse >around the exhaust port sealing or at least making the flow of gas difficult)? >I do notice a good bit of air relocation with my BC on the bottom when I switch >positions. So top wouldn't always be the top if I'm upside down? Is a semi >rigid breathing bag the design of choice, i.e. bellows? > > >Bill and Mr. Appleyard, could you please send me your addresses privately so I >can swap information with you more efficiently? Thanks--DD > > >David B. Drake EDS/SATURN Infrastructure 8-320-4190 on GMnet Spring >Hill, TN USA Internet: saturn.ddrake05@gm*.co* > >P.S. How do you get rid of the inert gas buildup in a completely closed >rebreather system when doing IWR. I assume the amount of Nitrogen/He that will >come out of your body will be more than significant to the size of your counter >lungs and reduce off-gassing efficiency...
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