Baldwin Termination Bars, H. Conklin

[Michael Wathen 556-9565]

Here is the a Post for our group that was submitted to me by
Harold Conklin.  Harold designed the SD-10 and The SF-10, some
other grands, and the model 6000 Concert Vertical.  He
contributed to many improvements that were incorporated into the
entire Baldwin Piano line.  He was the inventor of "Synchro-Tone"
(tuned longitudinal mode) strings, the "acujust" vertical hitch
pin, and other piano-related inventions for which more than 15
U.S. and foreign patents were issued.  Many of these inventions
still are used in production pianos.  He left Baldwin in 1986 and
has no present connection with the company.  As a sort of
disclaimer, he adds, that what he says may not necessarily agree
with their present technical positions.  His words follow.

If a piano designer attempts to tune the fundamental frequencies
of the treble counterbearing string lengths (the string lengths
between the capo bar and the ridge on top of the tuning pin
panel) to frequencies of partials of the speaking lengths of the
string, the result will likely be unpleasant noises ("zingers").
The "unpleasant noises" come from beats between the excited
resonant frequencies of the short counterbearing string lengths
and the frequencies of those speaking length partials that are
near in frequency to the counterbearing length frequencies.  In
casting piano plates it is impossible to control the
counterbearing lengths closely enough to end up with the
counterbearing lengths tuned  zero beat to partials of the
speaking lengths.  Therefore, in order to avoid "extraneous"
noises due to beats, it is desirable to dimension the
counterbearing lengths so that their fundamental frequencies will
lie between two speaking length partials and will be separated
from the nearest one preferably by at least a few hundred Hz.  It
is possible to do this with plates of conventional design by
careful positioning of the counterbearing ridges on the casting
pattern, and use of careful casting techniques.

To provide a long-wearing termination that does not change its
shape and to control closely the counterbearing lengths so as to
avoid the above problems, later model SD-10/SF-10 instruments
used an individual termination bar for each treble note.  By
carefully selecting termination bar dimensions it was possible to
achieve good results by using only two different types of
termination bar (Type I and Type II).  The only functional
difference between the two was in the length of the
counterbearing portion.  Only two Type II bars were used, the
other 33 bars being type I.

These individual termination bars were precision steel castings
that were hardened (harder than piano wire) for long wear without
changing shape.  Steel has lower internal losses than cast iron
and gives improved tonal duration.  After hardening, the bars
were plated with electroless nickel, used as a "solid lubricant"
to produce a surface on which piano strings can move with the
right amount of friction to provide stable tuning, but not too
much friction, which might cause excessive string wear and
difficult tuning.  Before the initial stringing operation the
bearing surfaces of each bar were to be covered with a light
coating of petroleum jelly (Vaseline).  this treatment should be
repeated before any subsequent re-stringing of these instruments.
It should never be attempted to file or re-shape the precisely
cast string-bearing surfaces of these parts because the
electroless nickel plating would be damaged.

The "duplexed" portions of the strings (between the bridge and
the hitch pins) operate under quite different conditions than the
"counterbearing" portions discussed above because the coupling
within the string between the duplex length and the speaking
length is much less direct due to the use of a pair of deflection
points (two bridge pins) to terminate the speaking lengths,
instead of just one (the capo bar).  Consequently, no undesirable
effects result from tuning the "duplexed" portions near to the
frequencies of speaking length partials.  In fact, an enhancement
occurs which increases the apparent duration of the upper treble
tones.  However, when the lengths between bridge and hitch pins
become longer than about four or five inches, the duration of
their own vibrations can become undesirably long, and may require
a damping means such as muting tape.