pianotech-digest V1997 #1919 (long)

[Richard Brekne]

Ron Nossaman wrote:

> >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.
>
> * I read softer V-Pro, and case hardening in sand cast.

perhaps we need to retrack and repoll opinions here. I have only heard references to
the SKIN of the plate being harder in sand cast plates.

>
>
> >Then there is the matter of the porish consistency difference between the
> two types,
>
> * I'll probably regret it, but I'd like an explanation of this too if you would.

It is stated that the vacuum plate has smaller and more uniform ....  "air pockets",
then the sand cast plate. This is supposed to be a contributing factor as to why the
vacuum plate has reduced internal damping ability.

>
>
> >> 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.
>
> * Metaphysics aside, how can a bearing load resulting from a given string
> tension, at a given deflection angle not be the same in either case?

What does metaphysics have to do with it ?  It can differ due to differences in the
strings vibrational axis. The clamped termination will be different then the pivot
termination. Er.. isnt a pivot just that.. a pivot. You dont pivot on a pivot in any
other direction then that of the pivot. You ever try to make a see-saw go sideways
??

>
>
> >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.
>
> * How would all this sideways motion, I'm throwing "twisting" out
> altogether, get past the termination (tangent) point and wallow around on
> the rest of the string/capo contact area to cause all that wear on all that
> extra area? This doesn't make sense to me.

> The "twisting" was an illustration in relation to the subject of a footprint,
> which you brought up. In reality neither twisting or footprints have any bearing
> on the subject, which was my point. Let me understand this correctly, do you
> dispute that a vibrating string will behave differently when under a pivot then
> when under a clamped termination point ??? Does this not then in turn directly
> relate to how the point of contact will react to this difference in behavior ??

>
>
> >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.
>
> * Wear of the capo? Why? The *internal* friction increase would be in the
> string, wouldn't it?

the internal friction increase is the other side of the coin. That point was not
made in the section you site here.

>
>
> >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.
>
> * So where can I find all this information about how, *specifically*, a
> large radius capo wears faster than a small radius under similar conditions?
> Since this is at odds with my understanding of basic physics, I'd sure like
> a cood clear explanation of how this works.

Outside of reading Ed's book, I can make no recommendations for you as yet. But...
wait a while.. I am catching up. grin

>
>
>
>  Ron N