pianotech-digest V1997 #1919 (long)

[Richard Brekne]

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Ron Nossaman wrote:

> >Ed has three main points to make here. The first is his (hotly disputed
> <grin>)
> >contention about the Vacuum pattern plate casts reduced ability to damp
> metallic
> >noise.
>
> * This has not been "hotly disputed" my a single living soul, as far as what
> I've read on this list. Am I missing the good stuff?

Ah... I was just kidding dont you see... all in fun. <grin>

>
>
> The second and third points are related.He states that  the Vacuum method
> >creates a harder plate, which causes problems particularily with the capo bar
> >termination, String breakage results from the Capo bar being to hard. To
> counter
> >that problem the capo bar is profiled with a wide rounded termination point
> which in
> >turn undermines the pivoting function of the capos termination point,
> causing loss
> >of string energy, excessive sting buzzing noise (especially as the capo bar
> wears)
> >and excessive wear on the capo bar itself (due to the string no longer having a
> >precise pivot.)
>
> * This is exactly contrary to what folks have been saying on this list. I
> don't recall anyone claiming anything but softer iron in the V-Pro plates,
> with a harder iron, and a sort of case hardening in the sand cast. Is that
> right, or am I in the Twilight Zone?

Lets see, I recall some folks saying that the Skin of the plate is harder, but I
dont recall a consensus of opinion stateing that the plate as a whole is softer
useing V-Pro. Quite the opposite, most of what I have read points to the opposite.
Then there is the matter of the porish consistency difference between the two types,



> If I read the posts right, who's
> correct, Ed, or the people with contentions contrary to his? Which is it, is
> the V-Pro plate harder, or softer than traditional sand cast plates, and by
> who's authority is this determined?

Seems like we have stumped onto a problem area no one on this list is "qualified" to
answer and at the same time back up with any kind of proof. Yet the "hardness" of an
iron casting plate is a quantifiable entity. So... I will try and dig around and see
what I can find.

> Also, I got into a discussion recently
> where (nearly) everyone and his brother claimed that the V-bar needed to be
> hard, *and* of a small radius profile in order to minimize string noises in
> the front duplex, in some cases, regardless of the counter bearing angle and
> length of the duplex segment.

Well lets see here. If the V-bar needs to be hard, then why do aggraffes work so
well in so many other pianos ?? Noff said about the "need" for hardness. The key
here (in regard to string buzz, loss of string energy, etc, is the profile of the
"V" bar. If this is at around 0,5 mm wide, then you are in good shape. However if
this is also a "hard"  capo bar, then you will experience string breakage. As far as
this goes in itself, I aggree that this is independant of bearing angle and lenght
of duplex segments.

> Also, how does a
> larger capo radius accelerate capo wear by not allowing the string to have a
> precise pivot? That doesn't make any sense to me at all and I'd like it
> explained. How can a longer support area for a given load, on a given
> footprint width, result in accelerated wear of the support? This is contrary
> to logic as I know it. How does this work? Let's backtrack and plug a few
> holes before we hotly dispute anything else, what do you say?

Grin ...I can only report the information and arguments as I read them, Ron, but
they make sense to me. The wear and tear on the capo by the string is of different
character if the capo is more a "clamped" termination then a "Pivot"  Your "longer
support area" for a given load analogy doesnt really hold true. The "given load" is
not there at all. The "load" is in fact different in each case, by virtue of the
fact that the "load" behaves differently in each case.

Lets put it this way. If you were standing on a really like "big" V-bar being really
carefull to only tilt your feet forward and backwards, exactly perpendicular to the
bar, and then compare the amount of wear and tear on your feet and on the bar to the
same experiment on a wider rounder bar, then your conclusion would be correct. But
if in the case of the wider rounder bar you introduce some twisting and sideways
motion then the wear will increase dramatically.(Both on your foot, and on the bar)
This only makes sense to me.

The precise pivot has the effect of limiting the stings motion in this regard.
Whatever "flex" the string has at the termination point is "pivoted" in the
direction of the pivot. If you replace the pivot with a wider, rounder surfoace,then
the flexing of the string is dispersed in several directions, thus increasing
friction and thereby wear.

Now.. be it known that this is not me talking as an authority. It is me relateing
what I have read. This part of the termination point as a "pivot" visa vi a
"clamped"  point is supported in several places on the nett. There are lots of
Universities running acoustics sides and several of these have short explanations
and/ or demonstrations of this. As far as I can see they are all in aggreement with
this.

>
>
>  Ron N

Richard Brekne
I.C.P.T.G.  N.P.T.F.
Bergen, Norway.

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