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<DIV>
<DIV>In a message dated 12/31/2004 1:47:55 P.M. Pacific Standard Time,
claviers@nxs.net writes:</DIV>
<DIV> <FONT size=4>Jim</FONT></DIV>
<DIV><FONT size=4> Nice post.</FONT></DIV>
<DIV><FONT size=4> Happy new year</FONT></DIV>
<DIV><FONT size=4> Dale Erwin</FONT></DIV>
<BLOCKQUOTE
style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: blue 2px solid"><=
FONT
style="BACKGROUND-COLOR: transparent" face=Arial color=#000000 size=
=2>I won't
repeat the previous posts, because I don't believe it's necessaty.<BR>Ron
Nossaman is mostly correct. The drastic change in pitch of one
section<BR>when the tension is off an adjacent section has more to do with=
the
plate<BR>than it does the soundboard. But it's not so much "compress=
ion"
of the<BR>plate as it is "deflection". It's the fact that the plate
wants to bow up<BR>when it's under tension. Release the tension of o=
ne
section, and the plate<BR>straightens out a little. Put the tension
back, and the plate bows up<BR>again. That's what the nose bolts and=
the
"horn" are for - to minimize the<BR>upwatd bowing. It may not be obv=
ious
to the eye, but if you will put a<BR>rigid beam across the piano, and some=
dial indicators measuring both plate<BR>and board deflection at different
places as you change overall tension, you<BR>will see what's happening.&nb=
sp;
I have done that, and the dial indicators tell<BR>the story.<BR><BR>It's b=
oth
plate and board, but as Ron says, I believe in this case, it has<BR>more t=
o do
with the plate than it does with the board.<BR><BR>Another point missed
here. If you look at one string only, and see changes<BR>in neighbor=
ing
strings, a part of that change will be coming from<BR>compression in the
bridge itself - i.e., forces on bridge pins being<BR>reflected to neighbor=
ing
bridge pins. If you look at the bridge on a<BR>microscopic scale, yo=
u
will see that it is not a rigid body at all. On the<BR>cell-to-cell
scale, it is somewhat springy too.<BR><BR>Conclusion: Because of the=
obvious plate deflection, you can't assume<BR>anything about the board.&nb=
sp;
When you change the tension, everything moves<BR>just a little bit, but no=
t in
the same direction.<BR><BR>Sincerely, Jim Ellis</FONT></BLOCKQUOTE></DIV>
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