> When stopped, it
> doesn't take long for all liquid to drain down to the bottom pool
> elevation. The clearances I was talking of were compared to a turbine
> aircraft engine, where the blade clearances are in thousands of an inch.
> The tube does not become near total full of liquid, but maybe 1/4 full,
> and the motion of the screw is fast enough to overcome the natural flow
> of the liquid down, much like =A0a leaky bucket elevator.

Note that the "screw binded to outer wall" version does not leak at
all when stationary. It will retain all fluid and restart immediately
where it left off when restarted (with suitable allowances for reality
such as a bit of slop and surge).


SUPERB EXAMPLE :

       http://www.swansea.ac.uk/grst/images/Archimedes'%20screw.jpg



       Russell

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