Steve Greatrex asks about turbine pumps and Duo-Arts.  The [expression]
problem is probably caused by the excess capacity of the turbine pump.

The Duo-Art does not use a regulator with a true feedback system and
is therefore dependent on a pump of limited capacity.  The rolls were
carefully edited with this in mind.

If you substitute a non-original pump you need to make sure that it can
provide the necessary suction but you must also make sure that the
capacity does not exceed the original or you will throw off the
regulator-spill valve relationship and have terrible expression.  You
can adjust the spill valve to compensate or add a bleed in the pump
line, but the best results are obtained with the right type of pump.

When installing the remote pump, be sure to use a supply pipe of
adequate size.  Remember that the pipe needs to be larger in diameter
than the original to reduce the friction caused by the longer length.
I used a 1.25" connector pipe to the wall and a 2" rigid pipe to
connect to the pump, just to be sure.  A 1.5" pipe would probably be
adequate for 10 feet or so.  I have charts on pressure losses in smooth
wall pipe but not knowing what was acceptable, I just decided to
oversize everything.  The remote pump is a great improvement.

While you are doing the modifications you might as well do one more and
install a low voltage, low current control for the pump motor.  You
can use a solid state relay that is switched by the original switch and
a small dc power supply.  This will help the switch to last forever and
will eliminate the need to install conduit or whatever is needed by the
building code between the piano and the pump.

Spencer Chase
http://nt.mcn.org/spencer/