<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML><HEAD><TITLE>Re: Bridge design</TITLE> <META http-equiv=Content-Type content="text/html; = charset=iso-8859-1"> <STYLE type=text/css>BLOCKQUOTE { PADDING-BOTTOM: 0px; PADDING-TOP: 0px } DL { PADDING-BOTTOM: 0px; PADDING-TOP: 0px } UL { PADDING-BOTTOM: 0px; PADDING-TOP: 0px } OL { PADDING-BOTTOM: 0px; PADDING-TOP: 0px } LI { PADDING-BOTTOM: 0px; PADDING-TOP: 0px } </STYLE> <META content="MSHTML 5.50.4134.100" name=GENERATOR></HEAD> <BODY bgColor=#ffffff> <DIV><FONT face=Arial size=2>Sorry Del,</FONT></DIV> <DIV><FONT face=Arial size=2>I thought the discussion had gone to = the treble end of the long bridge. I haven't seen a transition bridge setup yet but I'm = sure I will soon.</FONT></DIV> <DIV><FONT face=Arial size=2>    A laminate structure = is far more resistant to flex. Bend too straight pieces of wood and glue them = together. They want to stay where you glued them and will stay that way longer and with = less warpage than a piece of solid wood cut that way. (presuming the = glue joint....etc.) I've been in the construction trades 30 years and a = laminate beam is far more desirable structurally than even pattern nailing a = bunch of boards together.</FONT></DIV> <DIV><FONT face=Arial size=2>    Now here's where I = may be presuming two much. It seems to me, as the bridge is loaded and the soundboard/bridge structure approaches the point of failure, the = impedance would change exponentially. Small initial changes can become major. In my = limited experience I haven't heard of any real model test of 2 identical boards = and bridges glued up and run through a battery of tests. It was my feeling = (my 2 1/2 years of engineering at UCSB is now a jigsaw puzzle with a bunch of = missing pieces), that the glue joint as a variable might not have been coorectly = assessed.</FONT></DIV> <DIV><FONT face=Arial size=2>Keith R</FONT></DIV> <DIV><FONT face=Arial size=2>Conrad!  You better throw in a = technical disclaimer along with the automatic reworder on my new flame = suit.</FONT></DIV> <DIV><FONT face=Arial size=2>And HURRY!</FONT></DIV> <DIV> </DIV> <DIV>----- Original Message ----- </DIV> <BLOCKQUOTE dir=ltr style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; = BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px"> <DIV style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: = black"><B>From:</B> <A title=pianobuilders@olynet.com href="mailto:pianobuilders@olynet.com">Delwin D 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> Sunday, July 07, 2002 = 7:20 PM</DIV> <DIV style="FONT: 10pt arial"><B>Subject:</B> Re: Bridge = design</DIV> <DIV><BR></DIV> <DIV><FONT color=#000080></FONT> </DIV> <BLOCKQUOTE dir=ltr style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; = BORDER-LEFT: #000080 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=kpiano@goldrush.com = href="mailto:kpiano@goldrush.com">Keith Roberts</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> July 06, 2002 7:52 = PM</DIV> <DIV style="FONT: 10pt arial"><B>Subject:</B> Re: Bridge = design</DIV> <DIV><BR></DIV> <DIV><FONT face=Arial size=2>Maybe gluing the bridge cap on in = the crowned position and the bridge to the sound board in the crowned position, = like Dale does, will add the necessary impedance to the treble end of the = bridge. </FONT></DIV></BLOCKQUOTE> <DIV dir=ltr><FONT color=#000080>It's not the treble end of the = long bridge that is in question here. It's the bass end of the long bridge. And no = amount of crowning the bridge to match the crown of the soundboard is = going to affect that. Or much else, for that matter.</FONT></DIV> <DIV dir=ltr><FONT color=#000080></FONT> </DIV> <DIV dir=ltr><FONT color=#000080></FONT> </DIV> <DIV dir=ltr><FONT face=Arial size=2></FONT> </DIV> <BLOCKQUOTE dir=ltr style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; = BORDER-LEFT: #000080 2px solid; MARGIN-RIGHT: 0px"> <DIV><FONT face=Arial size=2>Most of the models discussed here = on the list, didn't seem to deal with the  stiffness added by the glue = joints in a laminated structure. Usually underestimated and throws that = kink into the reality/theory gap along with a few of the other observartions = Dale has made.</FONT></DIV></BLOCKQUOTE> <DIV dir=ltr><FONT color=#000080>Would you care to explain this a = bit more? How does stiffness added by the glue joints in a laminated structure = -- assuming there is any -- affect the impedance of the very end of the = long bridge?</FONT></DIV> <DIV dir=ltr><FONT color=#000080></FONT> </DIV> <DIV dir=ltr><FONT = color=#000080>Del</FONT></DIV></BLOCKQUOTE></BODY></HTML>