On String Breakage

[Tom@Sprint]

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Hello all:

As one who has been lurking in the string breakage discussion, I would =
like to offer a possibility that hasn't been offered yet as to why =
strings break in the M&H but not in the Story & Clark, given all else is =
considered and equal.

I'm wondering if the designers of the M&H were attempting to produce a =
piano that had as much power and sound as possible and in the attempt, =
designed the scaling closer to the edge in regard to the tensions being =
closer to breaking point.

The Story & Clark, being a piano intended for mass consumption, might =
have a more conservative scaling and as such, might be nearly impossible =
to ever break strings by mere playing unless they were to become =
extremely corroded.

As for the force discussion, Newton's second law has the resultant =
equation the F=3Dma. Which is force equals the mass times the =
acceleration. Disregarding friction, the forces input into a linkage =
system will equal the forces produced by a linkage system. This means =
F[at the key] =3D F[at the hammer] =3D F[at the string]. Going further, =
if we subsitute the mass x the acceleration (ma)side of the equation, =
then ma[force at key] =3D ma [impact of hammer] =3D ma[string =
vibration].

To lower the ma[string vibration], one has to lower the ma[hammer =
impact], and to do that one has to lower the ma[force at key]. They will =
all remain equal and to paraphrase Newton law 'Energy is neither gained =
nor lost'.

If you lighten the hammer, and you change nothing else, and you hit the =
key with the same blow and you believe energy is neither gained nor =
lost, then the end result is that the hammer will just accelerate =
faster. Lightening the hammer will not work by itself unless you =
undertake a way to also lessen the acceleration.=20
=20
The most common way to do that is to let-off sooner and/or reduce the =
hammer blow distance. The ma[at the hammer] will become lower and as a =
result the string will get less vibrational energy. But where does the =
ma[at the key] go? After all, don't all the forces remain equal? Well, =
the forces will remain equal but there will be less force at the hammer =
because all the forces put into the linkage after let-off will go into =
the front rail felts. In other words, there is added aftertouch and the =
forces are dissipated into the keybed, which is where all excessive =
forces at the keybed have always gone anyway.=20
=20
There is another problem to consider. Sooner let-off and decreased =
hammer blow might save strings and hammers but it does not solve the =
problem of brutality at the keyboard. One has to wonder if doing these =
adjustments simply enables and introduces the specter of other problems =
developing that may in the end be much more serious.

The reader will notice that no mention was made here of hammer voicing. =
This was already covered in an earlier post.=20

All the best.

Tom Thievin R.P.T.(Canadian Association of Piano Technicians).

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