Strings riding up (was Tuning stability)

[David Skolnik]

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Ed -

No smiley faces, so I'm not sure if you're serious.  In case you are, 
here's what I think:

At 06:02 PM 4/8/2004 -0400, you wrote:
>Fred wrote:
> > The real thrust of my musing was to consider
> > "going with the flow" in real world situations, where recapping or bridge
> > replacement aren't going to happen (at the particular moment). "Curvature
> > happens." Bridge tops crush at both sides more than on top. This is 
> what we find
> > most often in the field.
>and
> >    BTW, if anyone reading really believes that  light tapping doesn't crush
>bridge
> > tops, take a piece of wire, lay it on a bit of exposed bridge top 
> (above C8, eg)
> > and give it a tap with your brass rod. Even with your hammer shank. 
> Give the
> > amount of tap that has "given focus to the tone," "allowed you to see 
> the string
> > drop," "dropped pitch 4 cents," whatever. Then look at that bridge top. I
> > guarantee you'll see a little groove where none was before.
>
>So, this suggests we should be tapping the string in the middle!
>
>Not near the termination points, but along the arc in the center of the bridge
>cap.

The question again is, "Why are you tapping?". What are you trying to 
accomplish?  If there IS some benefit to be gained, even temporarily, it 
will be had by tapping either pin or in front of the bridge, not on the 
bridge surface.  If there is some negative front bearing, tapping on the 
bridge  string segment will not seat the string.  The question still 
remains whether you want, or need to seat it, against its natural 
inclination to form a straight line. If you think seating improves the 
tone, what's the cause?


>If humidity change can crush the wood at the edges to make the curved string
>groove, then tapping forcefully in the middle should be able to deepen the 
>groove
>in the middle so that the string is not lifted away from the termination 
>points at
>the edges.

I don't think you're visualizing the real configuration, but apart from 
that, if you could, in fact achieve string seating like that, what would 
you be doing to your downbearing?


>Would we then reach a point of stability as the crushed wood becomes 
>harder, or
>would we just be starting the process over again, so that the next rise in
>humidity  would push the edge grooves still deeper?

I am also curious whether the crushing process increases the resistance to 
further deformation.

>Let's hurry up and get this figured out, I'll be restringing the next piano in
>about 2 weeks!
>
>Ed Sutton


Ed -

Great opportunity for some documentation.  Are you willing to do 
it?  Measuring all the downbearing (front, rear, net, bridge profile)?  One 
question I would have would be how much downward movement you would observe 
in the seating process, once the piano is under tension.  In other words, 
what would prevent the strings from seating themselves, at least in a piano 
with positive front and rear bearing?


David Skolnik


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