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  1. #1
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    homemade rear venting regulator

    being a keen photographer i have always looked with envy at rebreathers with there rear or zero gas vent. there was the aqualung mistral which did the same thing but is now getting old and hard to find. what i am thinking of doing is blocking up the left hand air vent on my second stage with a removable plug. on the right hand will be a plug to adapt to a standard BCD hose which i will attach to the regulator hose.

    is there something really obvious that i am overlooking or can anyone think of a neater solution?

  2. #2
    Hail the Children of LLyr
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    So you just want to divert the exhaust to come out of a hose over your shoulder?

    A friend tried it and it just free flowed. in through the one hose, straight out through the other.
    "...are we human, or are we diver?"

  3. #3
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    Quote Originally Posted by Noggin the Nog View Post
    So you just want to divert the exhaust to come out of a hose over your shoulder?

    A friend tried it and it just free flowed. in through the one hose, straight out through the other.
    Yup, I can see why it would do that.

    Sent from my SM-G930F using Tapatalk
    'I saw some purple slug things on the Scylla, so I squished them' - #MiniBodger

  4. #4
    Where'd The Bubbles Go ....? Capt Morgan's Avatar
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    I think it could just turn your reg into an airlift.

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    Quote Originally Posted by Capt Morgan View Post
    I think it could just turn your reg into an airlift.
    Alternatively, it might not have the airlift function if you route the exhale hose downwards so it comes out near your arse.

  6. #6
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    Quote Originally Posted by Tunicates View Post
    Alternatively, it might not have the airlift function if you route the exhale hose downwards so it comes out near your arse.
    Instead it will increase the work of breathing putting you at risk of hypercapnia.

    Graham

  7. #7
    Established TDF Member Paulo's Avatar
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    You can get exhausts that are designed to divert the flow of bubbles to away from the divers face. I have an SP one somewhere on one of my sets that does just that
    Rememeber anything you read on the internet was probably written by some guy sitting at home in his underpants! Including this !!

    Illegitimi non carborundum

  8. #8
    Established TDF Member Nickpicks's Avatar
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    Just get a rebreather!

    The problem with putting a long extension on the exhaust vents is that as you breathe out, the tube will be filled with air. This will make the hydrostatic pressure at the exhaust (and hence inside the reg) the same as the hydrostatic pressure at the back of your neck. The hydrostatic pressure on your purge button will be higher, by roughly 250mm. The cracking pressure on most regulators is about 35mm, so your reg will just freeflow (the same principle as if you lower it into water with the mouthpiece pointing up).

    To solve this problem, you either need to have the same water pressure on the purge button as on the exhale vent (the old style Mistral did this by having the second stage at the back of the neck, and presumably used flap valves to get the inhale/exhale direction in the hoses). You could do this by having the exhale vents where they are, but fitting a shroud (with a gap) to catch the bubbles and divert them round your head, but getting this in just the right place would be tricky.

    You could fit the second stage to the inlet hose of a rebreather loop, with a vent on the exhale hose, both reg and vent mounted on the back to equalise the pressures. The problem here might be that if the second stage is much higher than your lungs, then work of breathing will increase.

    As regs have been designed and developed to breathe easily when they're used as intended, adding hoses and things to them is going to force them to work in a sub-optimal way. Not to mention the problems you're going to have if you need to share air with someone!
    The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at or repair.

  9. #9
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    Quote Originally Posted by frogfone View Post
    being a keen photographer i have always looked with envy at rebreathers with there rear or zero gas vent. there was the aqualung mistral which did the same thing but is now getting old and hard to find. what i am thinking of doing is blocking up the left hand air vent on my second stage with a removable plug. on the right hand will be a plug to adapt to a standard BCD hose which i will attach to the regulator hose.

    is there something really obvious that i am overlooking or can anyone think of a neater solution?
    Yes - it's called a 'Twin Hose' - Aqualung did one in recent times... You mau still find one on ebay. Ask an old diver...

    Your idea won't work as the diaphram that reponds to your breathing will be below the exhaust out level by serveral inches so on first exhale the valve will go into free-flow when you are face or head down, face or head up then it will be very hard to exhale; the exhaust valve and inlet diaphram have to be close together (and ideally at the centre of your lungs) to reduce the work of breathing effort and prevent free-flow from happening. (a bit of 'Boyles Law)

  10. #10
    Hail the Children of LLyr
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    Quote Originally Posted by Tunicates View Post
    Alternatively, it might not have the airlift function if you route the exhale hose downwards so it comes out near your arse.
    Where it could possibly serve as a form of propulsion or more likely cause your buddy to lose buoyancy control while sniggering uncontrollably.
    "...are we human, or are we diver?"


 
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