Piano Designers are Sadists

[Delwin D Fandrich]

Jim Coleman, Sr. wrote:

> Hi Michael:
>
> The one insurmountable problem in designing a piano that would stay in tune
> in the Tenor section is the fact that as the strings get longer and longer
> as you go down thru the Tenor section, the spacing on the bridge gets wider
> and wider. With wider string spacing on the bridge, there is less
> downbearing pressure to hold the swelling soundboard in check when the
> weather gets more humid. Conversely, when the weather gets drier, the
> soundboard decreases its resistance to the string pressure and the tension
> drops causing a lowering of pitch.

Well, let's not say "insurmountable," let's just say that a new approach might
be required.  For example:  Where, in the laws of God's universe, is it written
that the top two sections have to be designed with their strings perpendicular
to the strike line?  The next installment of the small piano design I working on
for the Journal will show the string layout for a small vertical piano in which
only C-88 is at 90º to the strike line.  The flare begins with B-87 and
progresses at a uniform rate from that point down.  This spreads the load out on
the bridge much more evenly.  There is no reason why this can't be done with
grand stringing scales as well.  In fact, it has already been done.  Check the
string layout on the Walter grand.  I must confess, I didn't do this for tuning
stability.  I was after the improved acoustic response that the more balanced
bridge and soundboard loading gives.



> One might counter with this by saying, the Bass seems to hold very well.
> Yes, we could have more wound strings in the Tenor, but then you bring in
> impurities higher up into the scale, so it is a tradeoff.

The number of unisons requiring wrapped strings depends on the overall length of
the piano and, more specifically, the available speaking length that can be
designed into the tenor section without running into the bass bridge. Or the
number of unisons the designer is willing to put into the bass section. Again,
there is no law in the universe that requires that there be either and only 20
or 26 notes in the bass section of a grand piano.

In general, the stringing scales used on current production pianos have too few
unisons with wound strings. I have very little use for tri-chord wrapped strings
on either bridge, so considering strictly bi-chords the following guidelines
could be used:
-- Pianos up to about 180 cm should use up to 30 or 32 unisons of wrapped
strings.
-- Pianos from about 182 cm up to about 215 cm should use from 25 to 30 unisons
of wrapped stings.
-- Pianos from about 215 cm up to about 250 cm should use from 22 to 25 unisons
of wrapped strings.
-- Pianos from over 250 cm should use from 20 to 22 unisons of wrapped strings.

Obviously, none of these are absolutes due to the virtually infinite variations
that exist in laying out a stringing scale for a piano of any given length.



> Another contra idea might be that you could increase the string length in
> the Tenor along with an increase in the string diameter and as a
> consequence have more downpressure on the board. The string lengths would
> still cause wider spacing along the bridge in an exponential manner and
> some of the same problems would still exist. And besides, all of this would
> require a longer piano which would require longer keys etc.

Not if the flare started as outlined above and not if a more reasonable number
of unisons were designed into the bass section.  It would also improve things
somewhat if a few of those unisons were shifted to the bass section.


> Yes, I know that one of the keys to progress is to not believe that
> something cannot be done. Let's hear some more new ideas. The olde guarde
> has spoken.
>
> Jim Coleman, Sr.

Jim,

I still recommend one of my favorite little books, "A Whack on the Side of the
Head" to one and all. Every once in a while I get it out and try some of the
author's little mind games just to kind of loosen up the little gray cells.

Regards,

Del