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Hi Hugh. Yes, depending on how much volume change there is between fully
retracted and fully extended, a fairly large tube reservoir is needed, and one
that is flexible enough so as not to create a vacuum strong enough to pull water
in when the rod contracts and expands near the surface. At depth, we'll have the
increased water pressure to supply the squeeze, but at the surface, just the
change in internal volume will move the oil so the tube needs to be
flexible.
I think maybe a 1 inch clear vinyl tube, not too thick walled, should be
flexible enough.
If the tube was too short, it's real cheap to just put a longer piece on
there. It wouldn't hurt to have too long a tube, just gives us extra oil
capacity.
I've seen some ingenious springed chambers that would work too. A little
more complicated, but worth investigating. The hi-dollar thrusters use that type
of arrangement. Frank D.
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