Musings about a homebuild BOB & pendulum rebreathers

paulraymaekers

you can also use a 'non-pendulum'-hose (like drager ray), and simply connect both endings at top of the scrubber: this way you don't inhale the exhaled gas from exhale-hose and your scrubber is used pendulum

paul

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www.rEvo-rebreathers.com

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

montyg

I assume you mean Dave's site?

It be the awesome Diver Daves Rebreather Site


I knew that one day I'd be able to prove Dave wrong about something. You are wrong Dave, I look at your site all the time!

I have for the last 4 or 5 years gone there almost every week and I STILL learn something or get new ideas every time I go there!

rgds
monty

iain-hsm

You can pretty much balance the negative aspects of C02 dead space in a single hose pendulum design by the improved C02 absorbsion you get. Provided the breathing tube is as short as possible and as small a diameter you can use without over doing WOB.

The best kept secret in pendulum breathing is:
As the dirty expired C02 has to pass through the scrubber twice each breath and each time in different directions. The forgotten "trick" is that only one side of the Soda lime grain get to "see" the dirty gas in a typical one way loop system whereas in the pendulum design the backward/forward push pull design is a more effective "cleaner".

Jpeg is of a Royal Navy semi closed or closed CDBA rig on a long term trial. The canister is 5.5 inches diameter by 3 inches deep, appx 2lbs (0.90kg) absorbant.
depth 80 fsw flow 4l/min gas 60/40 duration 90 minutes
depth 140 fsw flow 8l/min gas 40/60 duration 83.3 minutes
depth 140 fww flow 12l/min gas 40/60 duration 55.5 minutes
depth 180fsw flow 13//min gas 32.5% 67.5% duration 51.2 minutes

Note duration trial was limited by the cylinder size not the absorbant but pretty well balanced. Calculations were: 2 cylinders each 1.9 litres at 150 bar minus 30 bar (WP) divided by the flow equal to unit gas duration.
We also used a pendulum design rebreather on a 72 hour proposal for a subsmash project last year. iain Middlebrook

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Ben Field

I've been wanting to find out alittle bit more about Olivier and his rebreather for years after a read an article about him designing a modern diving helmet... not much english language stuff about him online though...

Nice! Brave but nice.... That must be an OTS Scrubber, certainly a V small rebreather.

BEN

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Marc T

Sorry Im very disappointed with your comment
Im always one of your best fan because you share what you do, and because , like Tom Mount, nothing seemed to be impossible to you.But I dont care, you helped me, and so I got my own wings, and so thanks for ever.
Now what its important is to do what I really want to do and speaking about dive I mean cave diving alone because its safest its simplest and much more beautifull to watch to the cave than to phone ( when will you be ready ? ), wait for ( are you ready? ), and look at ( are you OK? )your buddy.
So,yes, without time without buddy I have built a double Rebreather, witch is a little bit difficult and heavy to wear but rather easy to dive and Im rather proud of this funky prototype but yes I also worry about double issue because I nearly got it.
No time,nor knowledge and over all no pleasure to have a weebsite, but no reason to hide what I do.

Just for you to think about, my two Rebreather are feeded by a gaz block ( with back up solutions in case of leak in any part of the system) and its not a great prob to feed a third one.
I dont care about my first backup loop (because of its backmounted position, Kiss like, and minimal volume ) at any moment of a normal dive.
The third loop is a sidemounted Rebreather like joki or DDD, feeded by the same gazblock BUT the counterloungs are collapsed and you dont have to worry about buoyancy.
Its not a real emergency loop, its usefulness is to secure the deco stops includind deep stops which are drasticaly inceesed by RGBM.

Cavediving is dangerous, danger is a part of the game but lowering the danger to play as long as possible is the real challenge.

Cheers

Marc T

Dave Sutton

Sorry..... i Cave Divers obviously look at life differently than wreck divers like myself, but it's just that men walked on the *moon* with *one* rebreather loop... you would think two to be sufficient anyplace... ;-)

Does anyone but me remember that the original Navy Mark-15's were set up with two sets of hoses and DSV's, the second hose and DSV set was held with velcro loops on the back of the shell and the bailout mode was to have two divers on one loop? This is one of the reasons for the loop volume of the Mark-15 being what it is. I actually have one fully set up this way and can show photos if anyone wants...

Dave

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"Silent Diving with No Bubbles and No Politics".... www.nobubblediving.com

Marc T

Walking on the moom with a many thousand million dollars Rebreather!! Sorry you increase confusion, not the same challenge not the same risk not the same way not the same thing not the same world its as different than war and peace can be.

jasondrake

I'd definitely be interested in seeing pictures. Strange how through all my musings about bailout I've never once thought about puttin two people on one loop - that's an absolutely brilliant idea.

And I must say I agree - bailout can become an crazy. I see deep wreck divers on Rebreather's but carrying 2 drive cylinders, a suit-filling bottle and up to 3 slung 12litre bailouts. Why bother with the loop? I dive RB's to avoid carrying so much gear. I just use one loop, maintain and check it scrupulously and then trust it. Much like a pilot of a single engined plane I imagine. Instead of building 2 or 3 mediocre, failure-prone Rebreather's why not aim for a failure-proof single Rebreather?

Just my thoughts,
Jason

silent running

Hello Dave, yes please, I would like to see picturers of that. Interesting idea, although I guess it would presume that both divers had the same deco stops. Come to think of it, my tmix instructor was an x-military diver and he did insist on team dive practices, planning, same stops, etc. I learn something new about Mks everyday... -Andy

O.C.Diver

Hmmm, hostile environment where you have to be self sufficient and equipment failure equals death. Sounds comparable to me.

When you stop to think that the first moon walks were done with what is now 40+ year old technology, science, etc., whether it cost millions or "thousand millions", that it succeeded is pretty remarkable even with today's technology.

Ted

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Ted Green
Charter Boat "OC Diver"
http://www.ocdiver.com