Musings about a homebuild BOB & pendulum rebreathers

Woz

OK what about 2 hoses running side by side like Duncan has on his sidemount?

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jaap

Nice idea, but it could be tricky to get the oneway valves by the DSV to work. Like a normal one for the inner hose and something like a washer or flat torus shaped thing for the outer one. Also the inner one could maybe even be almost the same size as the outer one but made entierly collapsible, like a irrigation hose. Possibly with some small wire inside to prevent it from sticking.

Padowan

Of course that's possible. But it's not a pendulum rebreather then!

I've been thinking about all sorts of cunning ways of getting 2 hoses next to each other to design a twin-loop BOV, like Dave mentioned he's working on.

The most cunning solution I had was to use 2 independant collapsible (like lie-flat) hoses. As you breathe in and out, one hose collapses, as the flow passes down the other hose. These 2 hoses could be contained within one outer hose, and it's only at the ends, that 2 connectors rigid connectors would be seen. The other "benefit" is that they will act as part of the counterlung volume too, enabling smaller counterlungs wherever they are positioned. I have no idea what the WOB would be like for such a config, and it's never got further than my mind to do any tests!

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Marc T

Potentialy same issue on the submatix with his exhale bag inside the inhale

Duncan Price

One of the CDG boys was playing with this idea for a sidermount unit. The outer hose acted as part of the counterlung.

Alternatively have two pendulum rebreathers feeding either side of what looks like a standard DSV except that you can switch between them.

Dave Sutton

When you consider that the moon walks were done with a rebreather that was designed by the same engineering team, using many of the same design concepts, and in some cases the same *part numbers* as the Mark-15, it's no wonder that risk adverse professional skeptics rely on the Mark-15 when they need *one loop* that they can trust 100%....

And *the* most reliable rebreather electronics *ever manufactured* are the Revision G Analog Mark-15 electronics... which do exactly *one* thing: Maintain PP02 100% of the time, and are milspec man-rated life support equipment.

This is why when I dive a MILSPEC Mark-15 I carry the same exact bailout system that they used on the moon: Nothing.

Still alive after all these years,

Dave

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Dave Sutton

I'll take photos next week of the dual-DSV Mark-15, all Mark-15's were set up this way by the USN for buddy-breathing.

This type of design requires a scrubber that is twice as capable as needed for one diver (duh!) as well as a large loop volume. The Mark-15 has both items well covered.

I'm just getting back into society after a 3 week diving trip, so forgive the delay in getting photos shot.

Will Smithers and I, BTW, debated and discussed the collapsed "hand-off" bailout Rebreather (Will's preference for caving) and the worn by the diver "continually managed" bailout rebreater at length some 7 years ago. He ended up playing with a hand-off rig that could be carried collapsed while cave diving and able to be passed to another diver, without much success, and my experiments in bailout systems took the other path, which I think makes more sense in open water.

I agree 100% with the concept that if you're going to carry multiple 7 litre cylinders for "bailout", plus suit infltion bottles, and all that crap, then "why bother with the loop". I'm a pure alpinist..... less crap = a lower parts count = a better chance that I'll perform perfect maintenance on all components = longer mean time between failures = higher reliability. Being a little scared all the time is not a bad thing, either....


Interesting link for those studying this:


World smallest CCR by Dave


(have a sense of humor as you read it....)

and:

Diver Dave's Minimum/Bailout Rebreather



Dave

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silent running

Dave, I'm with you there. Just because we decide to dive an ECCR doesn't mean it has to be complicated-SP control only-KISSECCR. -Andy

Marc T

Agreed with many things you said, including the fact that alpine “thinking” could be the only choice for complex dive witch are impossible to do with a complex dive system who finally add is own problems and danger.
And yes MK15 with” DIR” or “KISS” electronic is certainly a way.


MK15 is certainly not the best Rebreather you can choose to try things with a second loop because of its size and also because of the position of the counter lung.

However, not being yet able to found a solution to the double loop don’t mean that’s a bad way and not having accident don’t mean that you are in a safe way.

I know your smallest Rebreather since a long time, great!!!!

paulraymaekers

not possible ofcourse, the hoses are not lungs, they have constant volume, so when you exhale, gas goes from mouth trough exhale hose trough scrubber into lung (and not into inhale hose, because it is closed at the other end, and is already full of gass:-)
when you inhale, you inhale gas from the lung, not from the exhale hose, (you can not vacuum that hose :-)

regards
paul

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.... the earth is flat, Elvis is alive, and radial scrubbers give longer dwell time than axials...