Thomas "Tom" E. West wrote about the Aeolian Duo/Art 88-note plastic
valve block players.  His problem is these pianos must be pedaled _and_
have the suction box going.  I have run across this for the last 20
years in almost all of the pianos like this I have seen.

The first problem is the material that the valves were made of: sponge
neoprene.  The second problem is the original valve travel installed
into the valve.  The factory built these with a valve travel of .050"
to .150", with most around .080".  Yes: 150 thousandths!  The valve
surface of the sponge neoprene distorts or wears away so that each
one leaked after perhaps a year after manufacture.  The third problem
commonly found in these pianos is the pneumatic cloth on the striker
pneumatics is leaky and riddled with holes 80% of the time now.

The solution to the three problems is to rebuild the plastic valve
blocks using new pouch leather pouches and airtight valve leather
glued to fiber or cardboard disks, instead of sponge neoprene.  Make
sure the travel is .035" to .040" just like most player valves, and
lastly, expect to recover the pneumatics.  I have collected these
plastic valve blocks for years and now have several hundred of them
rebuilt and sitting waiting for another couple of these pianos to come
in needing them.  They can also be used for nickelodeon percussions
when we build one of those in our shop.

If you want to test your piano to see if it has these problems,
disconnect the supply from the cutout and tape closed the tracker bar
holes.  Now find a vacuum supply of 30" or more suction and measure
the vacuum at the end of the hose coming out of it.  Then connect it
to the stack and connect your manometer to one of the valve note
ports (from under the pouch).  Your vacuum should be the same before
and after connecting the stack to the suction hose, but they won't
be.  Subtract the two numbers from each other and you will see you
are likely losing 10 to 20 inches of vacuum from the stack valves,
perhaps more.

I have restored almost a dozen of these plastic valve block pianos
and afterward they play better than they did brand new.  They can
play soft and loud which is something they _never_ did when new.

Doug L. Bullock
facebook.com/doug.l.bullock