Fred, Richard and list,
Fred Sturm wrote:
>I'm just not really convinced that hardness per se is an issue for
>string breakage (at least within normal parameters: hard enough not to
>deform too much over time, probably softer than the wire itself - though
>even here I'm not entirely convinced). Seems to me this might be one of
>those areas where we assume we know something and then never bother to
>question it.
Absolutely Fred - there seem to be many out there who have views on
duplexs and bar hardness. But how many of them have actually done the
experimentation? Our views, which have been progressing since 1994,
have come about in response to trying all manner of combinations.
> Breakage of a string at the capo happens mostly from an action similar
>to kinking and rekinking a wire. THe bend is accentuated when the string
>is struck, then springs back beyond rest point - and back and forth
>during vibration. As long as the fulcrum (capo) is stable and firm -
>that is, it doesn't move significantly realtive to the string, and
>doesn't have "springiness" - why does it make a difference exactly how
>hard it is?
Your correct, it doesn't. Its the affective surface area of the bar
in contact with the string and the string load on the bar (which is
the Sin of the deflection angle times the string tension) which
affects the 'survival' of the wire.
> I don't think the wire is deformed in cross section ("smashed") by
>hammer blows. In the first place, the hammer blows occur away from the
>point where the wire crosses the capo. In the second place, the hammer
>surface is springy. If it were a matter of deforming/thinning the wire
>during impact, hardness of the capo would matter. But I don't think the
>mechanics are set up in a way that would make this a factor.
> Sharpness of radius and high angle of deflection are very definite
>factors in breakage, no question.
Indeed, the smaller radius bar must be accompanied with a lower
deflection angle.
>I just raise the question whether
>hardness per se, other factors being equal, has actually been shown to
>have a significant impact. Preferably experimentally. Can anyone point
>me to experimental data? Or offer a mechanical engineering explanation?
Deformation of piano wire is a matter of the point loading. Both bar
radius and deflection angle will affect the actual deformation
pressure on the wire. Bar hardness directly affects the tendency of
the bar to deform.
> No question that much work has been concentrated on this area of piano
>design. THis is the area pianists need to make "sing," to bring out
>above the rest of the piano. Hence duplexes, aliquots, unequal unison
>lengths, varying angles of deflection, etc, etc.
Although I suspect that most manufacturers a guilty of doing very
little original work. Mostly, they seem to be content with copying
someone else's design, no matter how good or bad it may be.
Unfortunately, success in the market place doesn't necessarily come
about from superior design.
>Hardness/softness, as
>far as I have been able to determine has mostly been an issue of
>maintaining a clean termination over time. That is, at least, how I have
>always viewed it.
Exactly, although a cut bar will develop an inferior tone.
I guess that in the end, we need to ask ourselves the ultimate
question. Which manufacturers are building pianos with clean toned
trebles. Certainly, the current crop of modern pianos with their
Steinway style duplex systems, often sound more like an old typwriter
than a piano.
Ron O
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