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At 10:19 PM 2/2/96 -0500, Roderick Farb wrote: > > >On Fri, 2 Feb 1996, Richard Pyle wrote: > >> Then why, among my stack of NEDU reports, do I find various evaluations >> of the "Mk 15 1/2 Closed Circuit UBA"? (e.g., Rept. No. 10-84) > >The military wasn't happy with some of the features of the Mark15 such as >the small scrubber size which limited scrubber duration. They also didn't >like the stainless center section. There were other minor things they >grumbled about as well. BioMarine decided to build another unit that >corrected the complaints of the military and built about 18 Mark 15.5s >for the military to evaluate. The military evaluated them and liked them >and wanted other features added. So BioMarine used the Mark 15.5 design >and incorporated the new additons into the design and the Mark 16 was >born. BioMarine made the Mark 16 for a while but during the process >the government decided to reopen bidding on the contract to >supply rebreathers and Carleton beat out BioMarine in a hotly contested >race. So, the 18 Mk15.5 reverted back to BioMarine. BioMarine was bought >by Don Rodocker who, as part of the deal, acquired the MK15.5s. He sold >them to civilians including me and McKenney. There are now more than the >original 18 Mk15.5s out there because all that needs to be done to >convert a MK15 (of which there are a lot floating around) to a 155 is to >replace the center section with a 155 center and viola a MK15 becomes a >155. I know someone who has done just that. > > >> >> I don't know the history well enough, but I do know there are some >> fundamental differences in design concepts between the two units (you >> know, trivial things like counterlung placement, electronic and manual >> control principles, scrubber canister design, etc). What you suggest above >> might be akin to saying that the Mark 15.5 grew out of the foundation laid >> by the Fleuss Mask. My understanding is that the reason Stone started at >> ground zero on rebreather design was that he wasn't happy with the 15.5 >> for cave diving. He could have saved a hell of a lot of money by just >> modifying the 15.5 to meet his needs. Unless he's stupid (and I happen >> to know that he's not), he must have had some reason for re-inventing the >> wheel. > >If I were building my own rebreather, I would change several things about >the 155 that are made for the military but unnecessary for rebreathers >in general. Basically, the military needs good units that are a. dumb >proof, b. shake, rattle and roll proof and c. completely reliable in the >hands of guys who could f**k up a steel ball. I mean, BioMarine was asked >to remove the off-on switch and not put one on the MK16 because the guys >were torquing them off (and the switch is not inconsequential). The 16 is >turned off-on by removing and installing the battery. The switch can be >found on MK15 and 155s. Remeber too that Stone-if I remember the history >correstly- built two complete rebreathers in on Cis-Lunar until he >realized that some things did not have to be redundant. He took one such >unit and made two out of it and you now have them both. There is no >question he looked at the MK155 and redesigned it to fit his needs- with >the 155 providing a positive stimulus for the resulting unit. > >> On the other hand, what makes the 15.5 so attractive is the incredible >> amount of testing that it has been subjected to. Over the past year, >> I've learned a lot about how important it is to have real-world test time >> on units in a variety of conditions, and the 15.5 is near the top of the >> heap as far testing goes for mixed-gas fully closed 'breathers. > >This is one of the biggest points for BioMarine. They know rebreathers. >The new CCR500 is further evolution of their knowledge about rebreathers >and the price of $7000 for a fully closed circuit rebreather makes it >very attractive. For redundancy you could wear one in front and one in >back for $14K. > >> > You know, biologists have known for a long time that if earthlings >> > worshipped anything it ought to be the sun for providing the oxygen we >> > breathe and the food we eat. In the same vein, rebreather fanciers ought >> > to worship the MK 15.5 as the fountain of all rebreatherness and as such >> > they ought to bow their heads when we MK15.5 owners pass by with our >> > units. Rod > > >> >> Huh? The sun provides the oxygen? wha...? Did I miss something? I >> always though that the sun provided electromagnetic energy. > >Inside each particle of electromagnetic energy is a tiny bit of O2 which >is released when the energy hits a green leaf and other particulates in >the ocean. Sorry to butt in, you are obviously very knowledgable about rebreathers but you definitely need to go back to particle physics 101. The stuff coming from the sun are called photons. They can be described as particles (see wave/particle duality) but definitely not as a gaseos element. They are used by plants (including ocean plankton) during photosynthesis. You could say the light acts as a catalyst for the production of energy. In fact plants use up CO2 and produce O2. Don't mean to sound pretentious but I can't comment on the diving aspects (way over my head) so I thought I would share what knowledge I do have. > >> But on the rest of the stuff (e.g. head bowing, etc.), I fully agree. > >BTW, I thought your explanation for the bailout procedure if you lose all >three sensors in the Cis-Lunar ( the three sensor concept came from the >MK155) was excellent. Unfortunately, it is probably lost on >non-rebreather divers because you have to practice the concept >with a rebreather for it to become second nature. For many divers, the >only procedure to adopt if all three sensors fail is to place their head >squarely between their legs and kiss their butt goodbye. Rod > > > > >> Aloha, >> Rich >> >-- >Send mail for the `techdiver' mailing list to `techdiver@terra.net'. >Send subscription/archive requests to `techdiver-request@terra.net'. > > ======================================================================== David Hurt - Fisons Instruments Ph 913 491 2826 Fax 913 491 2934 E-Mail hurt@fi*.co* =======================================================================
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