Replying to Barry Dennis's inquiry in 091031 MMDigest about rebuilding
Duo-Art cross valves upside down.

Perhaps there are others not familiar with this approach.  I'll begin
at the very beginning.  Why "upside down" becomes obvious by the end.

1. When you rebuild the valves, be sure the valve stems are at right
angle to the button.  I have a piece of 5/8" thick steel drilled out
so the stem fits snugly in the hole.  5/8" assures that the stem will
have the proper length when I glue it together.

There are at least four styles of cross-valve stems: some have chopped
tops, some are bullet shaped.  Some of each kind have shoulders
to assure the button does not migrate down the stem as time passes;
I prefer these.

In either case I re-glue the buttons and then put the valve in the steel
to be sure it is at a right angle to the stem.  The long end of the
stem should just touch the outside of the steel.

2. The valve wells and the channels to the pneumatics should be
resealed.  An amazing amount of air can -- and often does -- travel
between both the wells, and the pneumatic channels.  As the amount
differs from well to well, if the wells are not sealed the stack cannot
be made to perform evenly.

When the pneumatics are off the decks, make a plug for the pneumatic
hole and pour the pneumatic channel full of shellac.  Drain out the
shellac through the pneumatic hole then wipe the outside clean with
alcohol on a rag, where the pneumatic will be glued.  Yes, its messy;
I use Zinsser orange shellac, at least two coats.

The pouch board can be checked by sealing off two pouches, attaching
a tube to a nipple to one in between, and alternately sucking and
blowing.  If the pouches that are sealed off rise and fall, this
leakage will affect the bleeds and the resulting performance of the
stack will be slightly erratic.  Reseal the pouch wells and replace
the pouches.

3. With the valve chest disassembled and the pouch-board set aside,
put all the outside valve plates on with their gaskets and their
straps.  Aeolian did _not_ glue the top plates in.  You shouldn't
need to glue them, either.

Now flip the valve board over and check to see that all the center
holes on the straps are centered in the crosses.  Also check to be
sure they are all the ones for the outside, which are just barely large
enough for the valve pins to go through.  The straps with the large
holes are for the inside only.  If someone has drilled the outside
strap holes larger, you're screwed -- don't bother to try to make them
work.  Get an orphan cross valve stack and pirate it for straps.

4. With the leathers on the valve, drop it in place, screw the inside
plate on and measure its travel.  Original travel measurements vary
from .040" to .055".  Everybody seems to have their own preferred
setting.  The wider the gap, the louder the piano can top out at.
The tighter it is, the faster acting and less loud the top volume can
be.  The most important thing is to pick your travel distance, and
stick slavishly to it.

(For your info, in my case I don't have a concert hall, so with a
9' 6" Steinway, I set my valves to travel .038".  I did the same with
my 7' 6" Steinway.)

Having measured the travel, remove the plate and add paper shims.
Repeat the process until you use the fewest number of shims to achieve
your desired travel.  Tear your hair out, if you must, but be proud of
your work when you're done.

5.  When you are satisfied with the travel, remove the plate and strap
one last time and ring the valve-well hole with thick Zinsser shellac,
thicker than honey.  I keep mine in a pint jar with its lid and the jar
threads greased so the lid doesn't glue on.  If you don't have any,
make some; it doesn't take long to evaporate it down.  It's what the
old guys did and you can do it too.  _Don't_ use glue -- someone else
someday will have to get the plates off without bending them.

6. Put the valve in the well and the plate on top.  The inside strap
should be at right angle to the outside strap.  It should have the
larger hole for the pin.  Screw it down, and now check to see that the
pin is centered in the hole in the strap.  This is why you went to the
effort of doing it this way.  This will assure that, when the valve
drops to seat, it will not touch the edges of the strap.  You know it
will not leak.

Bruce Grimes