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<DIV><FONT size=2>David Love wrote:</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2><EM>Del:</EM></DIV>
<P><EM>Is there an ideal dimension (height, width and width at the =
footprint) in
the treble section of the piano? It seems that the two requirements are =
at odds,
one of flexibility to allow the soundboard to move, and one of stiffness =
to
increase impedance in that section and improve sustain. </EM></P>
<P><EM>Wouldn't it be better to support the board in that section with =
an
additional rib, say, and leave the bridge more flexible? Or is it six of =
one...</EM></P>
<P>----------</P>
<P>It depends, I suppose, on what you mean by 'ideal.' Why do you think =
the
bridge needs to be "[flexible] enough to allow the soundboard to =
move...?" The
soundboard is going to move anyway--even if the bridges were infinitly =
stiff it
(the assembly) would still move. </P>
<P>The bridges need to be stiff enough so that the impedance level does =
not drop
enough to significantly affect power and sustain in between the ribs. =
Obviously,
if the ribs are closer together, i.e., a greater number of ribs, the =
bridge do
not have to be as tall to accomplish this. Both the bridge dimensions =
and the
number of ribs and their dimensions are a balancing act. The more =
ribs--and the
more stiffness and mass in the rib field--the lower and less massive the =
bridge
can (should) be. If the rib field is skimpy the bridges are going to =
have to be
taller and wider to compensate. </P>
<P>Bridge width is usually as much a function of mechanical necessity as =
of
acoustics. It must be wide enough to easily accomodate the bridge =
pinning
configuration without coming apart. It has been my observation over the =
years
that bridges that are much less than 30 to 32 mm in width are somewhat =
more
prone to splitting.</P>
<P>Del</P></FONT>
<DIV> </DIV>
<DIV> </DIV>
<DIV><FONT size=2>Delwin D Fandrich<BR>Piano Designer & =
Builder<BR>Hoquiam,
Washington 98550 USA<BR>360.532-2563<BR>360.532-6688<BR><A
href="mailto:pianobuilders@olynet.com">pianobuilders@olynet.com</A></FO=
NT></DIV></BODY></HTML>