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> > I agree for the most part, but I would drop the "75%" to maybe "40%", and > > I would reduce the "tenfold" to maybe "threefold". I would also not have > > I'll take your word for the 40%, but I feel tenfold for the CCR is > conservative. FYI, so you don't think I'm just being opinionated, I've > spend the last 30 years designing and manufacturing > electro-mechanical products for the aerospace and medical industry, but I > could be missing something or more. Well, I don't know how one would go about measuring these things, but a CCR (in principle) is the same as a SCCR plus some electronics and a second cylinder, minus an active or passive gas injection system. Both have breathing hoses, both have counterlung(s), both have a cansiter with CO2 absorbent material, both have (or should have) at least one manual by-pass gas injection system, both have (or should have) gas addition systems to compensate for depth increases, both have (or should have) open circuit bailout systems, both have the same backpack/BC requirements, both have a mouthpiece. O.K., so let's say the cylinder, regulator, and manual by-pass system comprises one-third the complexity of a SCCR (I would argue that this is a generous allowance, but for the sake of argument, I'll say it's one third). This means the second cylinder on the CCR comprises a 33% increase in complexity. Now, the active or passive gas addition system on a SCCR can vary in complexity from, let's say 5-20% of the complete complexity of the SCCR, so we'll call it 10% on average. Now, the CCR system is about 23% more complex than the SCCR system. That leaves the electronics, which comprises minimally 3 O2 sensors, a solenoid valve, a primary display with electronics, and a backup display. The quesion is, how complex is this electronic system when compared to an entire SCCR (including loop, counterlung(s), scrubber, cylinder and plumbing, backpack/BC, OC bailout system, moutpiece, active or passive gas addition system, etc.). Now, I'm an underwater photographer, so I KNOW how flakey electronics can be underwater, so I'll say the electronics system of a CCR is at least as complex as an ENTIRE SCCR. Hell, I'd say it's at least one and a half times as complex, when you think about the sensors. Shoot, I'll even give you that the electronic system of a CCR is a full one and three quarters times as complex as an ENTIRE SCCR. O.K., that would be 175% plus 23% equals 198% - which means that a CCR has about THREEFOLD the complexity of a SCCR. You said there was a TENFOLD difference, so that means that the electonics system of a CCR would have to be 877% - almost NINE TIMES - as complex as an ENTIRE SCCR! Come on Pete, is this realisitic? In my experience with rebreathers, the electroncs do not fail ANYWHERE NEAR NINE TIMES as often as ALL OTHER components on the system combined (most of which are shared by a SCCR), so the electronics are CERTIANLY not nine times as prone to failure. When you consider that you don't even need the electronics to safely abort in closed circuit mode (provided you are trained properly), then I think my Threefold value comes a little closer to reality than your Tenfold value. Where is my logic flawed? If you need more food for thought, consider that we have heard tell on TD recently of failures in the cmfv's (active gas additions system) of SCCR, so if anything I underestimated the liability, if not the complexity, of this aspect of SCCR. Whatcha think? Aloha, Rich
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