<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML><HEAD> <META http-equiv=Content-Type content="text/html; = charset=iso-8859-1"> <META content="MSHTML 5.50.4134.100" name=GENERATOR> <STYLE></STYLE> </HEAD> <BODY bgColor=#d8d0c8> <DIV><FONT face=Arial size=2>The undercutting was to move the bridge = /soundboard contact point away from the belly rail while maintaining the proper = speaking length for notes in the high treble. There is not much flex in the board straight down from the front of the bridge in the last octave</FONT></DIV> <DIV><FONT face=Arial size=2>Keith Roberts</FONT></DIV> <BLOCKQUOTE dir=ltr style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; = BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px"> <DIV style="FONT: 10pt arial">----- Original Message ----- </DIV> <DIV style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: = black"><B>From:</B> <A title=davidlovepianos@earthlink.net href="mailto:davidlovepianos@earthlink.net">David Love</A> </DIV> <DIV style="FONT: 10pt arial"><B>To:</B> <A = title=pianotech@ptg.org href="mailto:pianotech@ptg.org">pianotech@ptg.org</A> </DIV> <DIV style="FONT: 10pt arial"><B>Sent:</B> Saturday, March 29, 2003 = 8:34 PM</DIV> <DIV style="FONT: 10pt arial"><B>Subject:</B> RE: Bridge = dimensions</DIV> <DIV><BR></DIV> <DIV><FONT face="MS Sans Serif" size=2>Perhaps it was a = misinterpretation of your previous post on the subject, but I though you said that part of = the reason for undercutting the bridge was to allow that part of the sound = board to be able to move freely up and down.  That prompted my = question as it seemed that freedom to move up and down and stiffness, i.e. high = impedance, were at odds.  I think you've answered that question, but if the = board is going to move anyway, why bother to undercut the bridge other than to = move it away from the bellyrail?  Is it assumed that on a piano with a = more severely undercut bridge, it should have a more substantial rib = configuration to balance it and vice versa?  And given the choice between more = mass in the bridge or more substance in the rib configuration, what would you choose?  Am I right in assuming that the more minimal = undercutting in a Steinway bridge is because the rib configuration is more = skimpy? ! If so, then would undercutting the bridge further on a Steinway create more = problems and a weaker treble if the rib pattern and height remained the same?</FONT></DIV> <DIV><FONT face="MS Sans Serif" size=2></FONT> </DIV> <DIV><FONT face="MS Sans Serif" size=2> <DIV>David Love</DIV> <DIV><A = href="mailto:davidlovepianos@earthlink.net">davidlovepianos@earthlink.n= et</A></DIV> <DIV> </DIV></FONT></DIV> <DIV> </DIV> <BLOCKQUOTE style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; = BORDER-LEFT: #000000 2px solid"> <DIV style="FONT: 10pt Arial">----- Original Message ----- </DIV> <DIV style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: = black"><B>From:</B> <A title=pianobuilders@olynet.com href="mailto:pianobuilders@olynet.com">Barbara J. Fandrich</A> = </DIV> <DIV style="FONT: 10pt arial"><B>To: </B><A = title=pianotech@ptg.org href="mailto:pianotech@ptg.org">pianotech@ptg.org</A></DIV> <DIV style="FONT: 10pt arial"><B>Sent:</B> 3/29/2003 8:03:21 PM = </DIV> <DIV style="FONT: 10pt arial"><B>Subject:</B> Bridge = dimensions</DIV> <DIV><BR></DIV><FONT size=2> <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></FONT></BLOCKQUOTE></BLOCKQUOTE></BODY></HTML>