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Hi Rich, > >Hi Dan, >. When you refer to the pony bottle, >would this be the only means of OC bailout, or just a supplementary one? There are mulitiple bailouts systems built in to both the BMD and Odyssey. But on the BMD they are far more complex than just grabbing a free second stage from an external pony. And no, I am not thinking of doing any decompression diving on either until the bailout systems become as reflexive for me as going to my alternate reg/bottle on scuba. > I think you would always want an open circuit route to the surface on any >dive in the event of a non-recoverable loop flood. It seems to me that >limiting OC bailout to onboard cylinders would be dangerous if a problem >occurred near the end of the dive. On the Odyssey you go to a built in open circuit system, that would not maintain an extensive decompression without the rebreather. On the BMD there is a whole series of valve shut down systems and a needle valve to allow manual reguation of tank gas directly into a "breathing tube", not connected to the counterlung (so a catastrophically torn bag is something you can deal with). It has several backup systems, but like I said, this is an area I'd have to spend many more hours with before I could use all of it effectively. Right now I could use the needle valve system of the BMD for the most catastrophic failure, but some of the less critical failures have much better ways to be handled (by the BMD design). This is why in the absence of an instructor (if I did'nt have Todd Ives with me), I would have a pony and reg hanging on the outside of the case somewhere. Finding the perfect way to rig this will be one of my projects next week. With the Odyssey every thing you need is right there in it, although I've heard that it might be a good idea to have a separate pony to power the BC, so you don't rob air from your emergency bailout tank. I'll let you know once I have some time on the Odyssey. > >I have a question. If I understand the compound bellows principle, the >purged gas is contained within a bellows that is inside the main >counterlung, correct? In the BMD the 'dual toroidal counterlung" has no compound action. return of gas is dumped overboard as the diver exhales by a spring loaded proportional discharge valve. A puncture here or leak would cause considerable gas loss --in this case you'd be shutting down the tank valves and using a breathing tube and needle valve right off the main tank--a manual regulation. In the Odyssey the purged gas is contained in a bag within the bellows, which is in a fiberglass case, and next to impossible to puncture or leak. The material of the bags is as tough as a zodiac boat. A leak (very unlikely) is dealt with by switching to an open circuit scuba system with its own 1st and second stage outside of the rebreather loop, but contained as a built in part of the Odyssey.. Odyssey feels its too dangerous to have a diver with a serious failure screwing around with a complex bailout system. They want a simple scuba switch. Once thats done and the diver is thinking clearly, some other backup systems can be utilized. For more on this now, I'd have to pass this to Dave Schubert, but I do plan on getting very familiar with the Odyssey soon with some good long drift dives. Regards, Dan Dan Volker SOUTH FLORIDA DIVE JOURNAL http://www.florida.net/scuba/dive 407-683-3592
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