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MMD > Archives > April 2005 > 2005.04.28 > 09Prev  Next


Duo-Art Cross Valves Modification
By Bruce Grimes

Regarding reaming out the bottom valve guides on cross valves, I thought
everyone knew about rebuilding cross valves upside down, so as to avoid
the leakage-on-seating problem.  For those who haven't:

1. Put all the top plates and guides in first.

2. Then turn the deck upside down, put the valves in place with bottom
valve plates and guides for the gapping process.

3. As the top guides are the ones with the small holes, the valves will
be centered, and seated in the up (or play) position, so when you screw
on the bottom plates and guides, you can see if the pin is perfectly
centered (which is as it should be) as you set the proper travel
(gap).

4. When properly gapped, put your thick shellac solution on and screw
down the valve plate.  Check again to be sure the pin is perfectly
centered.

There are, by the way, at least three varieties of pins in the valves:
those with rounded tops (often, but not always) have a collar molded
in just below the wooden valve button to keep it from sliding down
on the pin.  I have yet to see pins with chopped off tops that had the
anti-slip collar.  I have seen pianos where the button definitely had
slipped down the pin.  This, of course, affects the playing capability
of the valve.

I have rebuilt many cross valve stacks, and built several brand new
ones, and they seem to work quite well.  So do original round valves.
I have also seen later Steinways with original round valves.  When
paired with the proper size pneumatics, they work quite well.  When
I built my stack for my 7' 6" Steinway, I followed this later Steinway
pattern.  At least one of the ten Steinway "D"s was built with round
valves.

One other thing I was told years ago, if after moving a grand it
doesn't play, one trick that often works is to lift the piano two or
three inches (I never measured exactly how much) on the treble end,
and then let go -- drop it!  Repeat on the bass end.  It make take two
or three times, but this often shakes the valves into place.

You may also find that running the test roll up and down the scale at
high vacuum does the same thing, and doesn't show as much on your fine
pine floors.

Bruce Grimes


(Message sent Thu 28 Apr 2005, 14:52:56 GMT, from time zone GMT-0400.)

Key Words in Subject:  Cross, Duo-Art, Modification, Valves

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