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>Mark Caney wrote
>
>I experimented with this when I first got into photography until I discoved
>that it causes your reg to go into massive freeflow/turns your lungs inside
>out. You could not have the end of the hose significantly higher than the
>second stage. However, an old trick was to use a twin hose because the
>bubbles are behind your head, which makes a substantial difference to the
>fish. So maybe if you ran the hose a little way down your body it might give
>the effect you want. (Or buy a twin hose).
I think we need something more sophisticated than a simple hose. Clearly a
simple hose will lead to free flows (second stage diaphram separate from
exhaust, eg. USD Conshelf), regulator lockups ( diaphram and exhaust one, eg.
a Poseidon Oden) and nasty barotrauma to our tender bodies. However it should
be possible to design a valve such that the exhaust side is at 1 ATA absolute,
the requlator side is at ambient, and flow is 0 until the regulator side
preasure
increases ( when the diver exhales ). I can imagine the rough design for such
a valve. However there is no way I could manufacture one! I suspected that
this problem has been solved by the gas reclamation system used by comercial
divers. It also appeared to be solved by the device I saw on the TV show
( which was about some H2O2 dry suit heater ). I can't remember who
suggested that you only had to admit water to the hose and the problem is
solved.
However it would be rather noisy!
I did manage to manufacture one system from a garden hose, garden hose faucet
and a rubber glove. The regulator exhaust when into the rubber glove through
the faucet and up the garden hose to the surface. By adjusting the faucet the
flow could be controled so that free flows and lock ups of the regulator did not
occur. The problems were
1. The system required constant adjustment underwater.
2. The breathing characteristics where terrible. Exhaust effort was far to
great.
The system could be used in an 8 ffw pool but I wouldn't try it in a real
diving
situation. The reason (I believe) for the poor performance was that the valve
restricted flow rates instead of a preasure drop. There's probably an
analogy here with electric circuits, maybe resitance vs induction or
capacitance.
Anyway I'm still stuck at the drawing board stage.
Barrie Kovish
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