Hi Paul,
I was thinking on similar lines. Great stuff. I noticed this...

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Obviously the water level in the DP would control the height of free sliding plugs in the AP.
Max height is at the upper girdle stone. Granite and water are about 2.6-1 weight/volume.
Got to remember that the downward pressure from the DP is also lifting an increasing column of water as well as the plugs.
Haven't done any real calcs yet but maybe the whole thing is always in a state of equilibrium.
So therefore we could be looking at a hydraulic lift who's purpose is to vary the length of the AP.
The original total length of the plug blocks is about equal to the distance between the girdle stone centers.
Simple analogy... A Trombone!
Any gas trapped above the AP plugs would require a large expansion chamber to vent into.......



Edited 2 time(s). Last edit at 25-Nov-15 07:25 by Jon Ellison.