Rescaling

[Delwin D Fandrich]

----- Original Message -----
From: "David Love" <davidlovepianos@hotmail.com>
To: <pianotech@ptg.org>
Sent: June 28, 2001 9:53 PM
Subject: Rescaling


> List:
>
> I have begun having the pianos I'm restringing rescaled (or at least
> recalculated).  I notice, at least with the company doing the calculations
> for me, that they often set the scale with a slightly higher tension.
> Instead of starting with #13, for example, the rescaled instrument will
> start with #13 1/2 and procede through a higher range of gauges, ending
with
> perhaps 21 or 22 instead of 19 or 20 (this happened recently on a Steinway
> B).  I would like to know what others' experience is in this area.  Can a
> higher tension scale "choke" the board?  When is it preferable or not
> preferable?  Are there varying philosophies about scaling or are the
pianos
> I've had rescaled just been wrong?

--------------------------------------------------------

Many, if not most, pianos designed from the late 1800s through the early
1900s (and this includes most Steinway models) have very short treble
sections. It's not unusual to find a speaking length at C-88 down in the 47
mm range (that's about 1 7/8"). It's common practice to specify #13 1/2 wire
for these short strings to raise the string tension by 10 pounds or so. This
does look better on paper, though I'm not sure just how much good it does in
practice. It also adds considerable stiffness to an already very short
string. It's rather a judgment call. In the case of the Model B that you've
mentioned my own practice is to leave the top two unisons with #13 wire and
then switch to #13 1/2 but, as I say, this is a judgment call.

At the other end of the bridge--and here you've mentioned the Steinway B
which is a good example of the problem--many pianos are designed with a
tenor section that is simply too short. Take a look at the way this bridge
hooks back at the low end of the tenor. The speaking length is
'foreshortened in a manner that is appropriate' to quote one early writer.
With the original scaling, the tension on this string (F-21) is around 115
to 120 pounds. B-27 just six notes up is strung at approximately 165 pounds.
Yes, there is going to be a tone quality variation between the two. I was
some nervous the first time I scaled the F-21 with #22 wire but the result
was, while not great, considerably less bad than the original. A better
practice is to drop the last few notes off that bridge and install a third
bridge using wrapped bi-chords. An even better solution would be to make a
new plate and put about 26 or 27 notes in the bass section and avoid the
problem entirely, but most customers consider that to be overkill on the
average rebuild.

The idea of rescaling is to even out the scale and improve the acoustic
performance of the piano, not to make nice pretty lines on a piece of paper.
There must be a liberal dose of practical hands-on experience applied to the
process. By that I mean, do the scale and then put it on the piano and
listen to it. I don't care how many scales one has done on paper--how many
one has done on the piano is more important.

I started scaling pianos about 30 years ago using a slide rule--no fancy
calculators or computers back then--and have quietly--OK, sometimes not so
quietly--observed an era of scaling excesses. A lot of damage has been done
to some rather nice pianos over the years by folks who were able to make
nice lines on paper but who didn't have a clue when it came to the real
piano. Hopefully, most of those have either quit or have learned a bit more
about the real piano since then. At least I don't hear about as many weird
things being done in the name of 'rescaling.'

I still do get nervous when I hear of overall tensions being raised. Who is
evaluating that plate to make sure it can take the added stress? Who is
evaluating the changes in stress placed on a given plate even if the overall
tensions are not being raised, just changed around a lot. For example, with
some particularly poor piano designs it is quite possible to raise the
tensions through a badly scaled tenor treble section by a few thousand
pounds while lowering them through the bass by a comparable amount. The
overall tension load may remain similar, but now there is a whole lot more
stress on the struts in the tenor/treble section. It is to the credit of the
plate designers that we rarely hear of problems with piano plates developing
problems as a result of some of the scaling excesses that have gone on,
still I think it behooves us to be careful.

Del