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MMD > Archives > March 2002 > 2002.03.22 > 10Prev  Next

Effect of Piano Key Length
By Ferdinand Pointer

>[ How does PTG define key balance and key weight, and what
>[ adjustments can the piano tech perform?  Can the balance point
>[ (the fulcrum) be shifted?  Should this be necessary?  -- Robbie

Hello list.  As a 25+ years RPT member of PTG, I can assure you
that PTG has no single definition of anything to do with pianos, keys,
strings, pitch, tuning method, hammer weight, regulation of anything
else.  PTG is a group of individuals who all have opinions about
pianos.  Very few of these individuals have the same knowledge,
experience or ideas about much of anything.  [ Gosh, that reminds me
of MMDigest! :-)  -- Robbie ]  Having said this I will now opine on
the topic of key length.

Mr. Herr's observation of key length in different pianos is right
indeed.  Every 9' grand I have ever worked on has keys far longer than
many Duo-Art grand keys.  Many taper in length from bass to treble in
order to match up with the string scale.  Touch has all to do with
ratio, not length.  Actually the longer the key, the less the friction
on the capstan.  This is a result of the larger radius of the key
travel around the balance rail.

As for placement of the hammers in relation to the strings, the hammer
action or stack is positioned on the key frame so that the hammers will
hit the strings at about 1/9th the speaking length.  Then a line is
struck from key one to key eighty-eight under the wippens.  This is the
capstan line.

Next, the balance rail position is found by striking a line one half the
distance from the capstan line to the front of the key.  Of course this
is the ideal placement as one strives for a two-to-one ratio of key dip
to capstan rise.  As this is not always achieved by all manufactures,
one can always change this when key frame and action is being rebuilt.
There is at least one piano supply house which can change these
dimensions for you when making a new keyboard for your rebuild job.
I have seen amazing results from this procedure.

The biggest problem with long keys is the flexing of the key over its
length.  This causes a spongy feeling and is very painful to the lower
arm after playing hard for an extended period of time.  You will find
a long shoe or plate of hardwood about 1/8" thick on the bottom of
concert grand keys.  This, in addition to an extra long key button,
provides stiffness to the key stick.

During very hard playing as one would do on a concert grand, the heavy
hammers and long keys can really be a problem if there is not enough
stiffness.  Some Duo-Arts do not have enough support to provide enough
stiffness and suffer the same problem.  This too can be fixed.

Of course no one thing usually makes all that much difference.  Don't
go deciding to change key ratio to solve all the problems of poor piano
design or worn parts.  Having now worked on pianos full time for thirty
years, I have learned one thing:

  "No one change will make a great difference until enough things are
   right, at which point every change makes a noticeable difference."

Ferdinand Pointer, RPT
The Piano Co.
Clearwater, FL  USA

(Message sent Fri 22 Mar 2002, 04:52:39 GMT, from time zone GMT-0500.)

Key Words in Subject:  Effect, Key, Length, Piano

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