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Thread: Capacity of rebreathers' breathing bags? Rebreathers with 2 bags?

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    RBW Member Anthony Appleyard is an unknown quantity at this point Anthony Appleyard's Avatar
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    Capacity of rebreathers' breathing bags? Rebreathers with 2 bags?

    Please:
    (1) In a rebreather with one bag, what is the usual capacity of the bag when full? I.e. how big should the bag be?
    (2) How many rebreathers have 2 bags, and the breathing circulation is lungs to bag1 to absorbent to bag2 to lungs? How big should each of bag1 and bag2 be?

    (3) What is the usual capacity of the bag of a diver's lifejacket (e.g. Fenzy) when full?
    (4) What is the usual capacity of the bag of a stabjacket (e.g. Buddy Commando) when full?
    Last edited by Anthony Appleyard; 22nd September 2016 at 15:45.

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    Supporting Member Dsix36 has a reputation beyond repute Dsix36 has a reputation beyond repute Dsix36 has a reputation beyond repute Dsix36 has a reputation beyond repute Dsix36 has a reputation beyond repute Dsix36 has a reputation beyond repute Dsix36 has a reputation beyond repute Dsix36 has a reputation beyond repute Dsix36 has a reputation beyond repute Dsix36 has a reputation beyond repute Dsix36 has a reputation beyond repute Dsix36's Avatar
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    Re: Capacity of rebreathers' breathing bags? Rebreathers with 2 bags?

    The actual capacity of the bag is kinda worthless. The capacity needs to be measured when fitted the rebreather and ready to use. When I built my BOB, I first used one 4L bag since that was plenty for me. When installed the bag would not fully expand and limited the capacity. I ended up using 2 4L bags to make it work.
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    RBW Member Anthony Appleyard is an unknown quantity at this point Anthony Appleyard's Avatar
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    Re: Capacity of rebreathers' breathing bags? Rebreathers with 2 bags?

    I don't know how relevant this is, but I have just found that in my posable Poser CGI model of a Fenzy-type diver's lifejacket, whether or not converted into a rebreather, the bag, when inflated by 100%, increases volume by 4.15436 liters.

    The same done with my CGI model of an old-type British Siebe Gorman rebreather's breathing bag (c.c. CDBA) calculates out as 2.35263 liters.

    The same done with my CGI model of a stab-jacket shows something like 10 or 12 liters.

    https://en.wikipedia.org/wiki/Poser

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    Re: Capacity of rebreathers' breathing bags? Rebreathers with 2 bags?

    Not too sure how important the 4th and 5th digits after the decimal point are

    Michael

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    RBW Member Anthony Appleyard is an unknown quantity at this point Anthony Appleyard's Avatar
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    Re: Capacity of rebreathers' breathing bags? Rebreathers with 2 bags?

    Here is an early (1944) oxygen rebreather with two bags:-

    f.jpgg.jpg
    The set's parts are fastened to a heavy rubber back-and-chest apron (or whatever the correct word is); the big hole in the middle is for his head. He breathes into his right (the image's left) bag, through the canister (behind his shoulders), through his left bag, and back into his lungs. The right bag is smaller than the left bag, likely so that his breath can easily overfill it and thus make sure that more often some of his breath goes through the canister.

    Re the extra decimal places :: sorry, it happens with cutting-and-pasting output numbers.
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    RBW Member Anthony Appleyard is an unknown quantity at this point Anthony Appleyard's Avatar
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    Re: Capacity of rebreathers' breathing bags? Rebreathers with 2 bags?

    387412.jpg
    Back view showing canister (2 men) (best image of it that I have).
    The set is called an UWSBA (the Dunlop Underwater Swimming Breathing Apparatus).

    And no help from the University of Waterloo Sports Business Association messing up the Google search.
    Last edited by Anthony Appleyard; 23rd September 2016 at 15:36.

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    Re: Capacity of rebreathers' breathing bags? Rebreathers with 2 bags?

    There is a requirement under EN14143 for a tidal volume of 4.5ltrs, ancient military rebreathers are Not a good source of best practice for CCR design.

    The lungs in 1 or 2 bag designs are usually a much bigger volume to cope with being worn.

    Do you need 4.5ltrs- not generally.

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