A treble in trouble

[Delwin D Fandrich]

Delwin D Fandrich wrote:

> A440A@aol.com wrote:
>
> > Greetings all,  can we talk about this?
> >
> > Del writes:
> > >...And to a certain extent strings can be
> > >"pre-stretched" a bit by rolling them or pressing them--temporarily stretching
> > >them well above their normal pitch--as is the
> > >practice of some factories and rebuilders. These practices can all help to
> > >improve initial tuning stability.
> >
> >      I agree, however, these practises can overstretch a lot of strings.
> > There is a limit of tension a  wire will accept without deformation, when
> > surpassed, you usually have a tonally deficient string, ( at least I do,
> > after maybe, a chipping "accident".).  Stretching strings "well above" their
> > normal pitch by rolling is asking for excessive stretching.  I think
> > factories suffer from some of this, judging by the amount of false strings in
> > some domestic instruments.
>
> Ed,I agree with you! We don't "pre-stretch" strings by either rolling them or depressing them in any way. I mentioned the
> practice only because if I didn't someone out there would have been sure to inform me that it was possible to do so and would
> now be extolling the virtues of the practice. We generally don't even pitch raise new strings much more than a quarter of a
> step sharp.

----------

Part II

Ed,

Upon reflection I was dissatisfied with my initial response to your post. So, rarely being one to leave well enough alone, I plod
on...

So, Ed, I agree with you in part. The question is over my comment about "temporarily stretching them [the strings] well above
their normal pitch." in order to pre-stretch them and thus improving a piano's initial pitch stability. In fact, it is quite
possible to do this without damaging the strings in any way. Sometimes. It is not a question of how far above their normal pitch
they are stretched, but how close to their breaking point they are taken.

In most pianos and through most of the scale this practice can be done in such a way as to not injure the music wire in any way.
It can be a bit difficult to determine in advance whether you are going to do more harm than good, however.

For example: C#-29 in a Steinway M uses a #18 gage wire (0.041" diameter) and when at pitch has a tension of approximately 113
pounds. In a Steinway D, D#-43 is also a #18 gage wire but has a tension of approximately 183 pounds. In the case of the Model M,
I could indeed stretch the strings of C#-29 "well above their normal pitch" without them any uncomfortable degree of stress. Less
so, the strings of D#-43 in the Model D. The point is to not stretch any string so much that its tension gets too close to its
elastic limit. For music wire this is approximately 70% of its breaking strength.

(Again, for a MUCH more complete analysis of what happens to music wire when it is placed under tension, see the Journal article
I referred to earlier. It was written by Glen Hart and appeared in the October, 1995 Journal.)

If the reader is going to "pre-stretch" the strings in any piano, my advice would be to use restraint and to pretty much stay
away from the treble section and the bass strings. In the treble, the strings are already stretched to a tension that is fairly
close to their safe limit and in the bass, you never know. Until you've done it, that is, and then it's too late.

I stopped doing this some years ago, not so much for what it did to the strings, but for what was happening to bridge pins and to
the surface of the bridges. The two weakest spots of modern piano design (at least in terms of their mechanical structure) are
the two string termination mechanisms. The industry should not be excessively proud of either the bridge pin system (no matter
how well the bridges are "hand-notched" by "old-world craftsmen") or the agraffe. The traditional capo 'd astro bar/V-bar is
nothing to write home about either. Ah, well...

-- ddf