<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML><HEAD> <META content=text/html;charset=iso-8859-1 = http-equiv=Content-Type><!doctype html public "-//w3c//dtd html 4.0 = transitional//en"> <META content="MSHTML 5.00.2314.1000" name=GENERATOR> <STYLE></STYLE> </HEAD> <BODY aLink=#ff0000 bgColor=#ffffff link=#0000ee text=#000000 = vLink=#551a8b> <DIV> </DIV> <BLOCKQUOTE style="BORDER-LEFT: #000000 2px solid; MARGIN-LEFT: 5px; MARGIN-RIGHT: = 0px; PADDING-LEFT: 5px; PADDING-RIGHT: 0px"> <DIV style="FONT: 10pt arial">----- Original Message ----- </DIV> <DIV style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: = black"><B>From:</B> <A href="mailto:klavier@annap.infi.net" = title=klavier@annap.infi.net>Frank Weston</A> </DIV> <DIV style="FONT: 10pt arial"><B>To:</B> <A = href="mailto:pianotech@ptg.org" title=pianotech@ptg.org>pianotech@ptg.org</A> </DIV> <DIV style="FONT: 10pt arial"><B>Sent:</B> Tuesday, September 28, = 1999 5:46 AM</DIV> <DIV style="FONT: 10pt arial"><B>Subject:</B> Re: evaluating sdbd. = crown & bridge downbearings in a new piano</DIV> <DIV><BR></DIV> <DIV><FONT color=#000000 size=2>Richard,</FONT></DIV> <DIV> </DIV> <DIV><FONT size=2>.....</FONT></DIV> <DIV><FONT size=2></FONT> </DIV> <DIV><FONT size=2>Here is an experiment I conducted in my shop yesterday.  I selected a room dried strip of sitka spruce, made = pencil marks on it 18 inches from the end.  I bent the spruce to an = approximate 3' radius and glued a rib to the bottom.  When I measured the top = of the spruce, I found that the pencil mark position indicated the top had = stretched approximately 1/16 inch, and the bottom had compressed about as = much.  This model indicates to me that the top is in tension and the bottom = in compression.  </FONT></DIV> <DIV><FONT size=2></FONT> </DIV> <DIV><FONT size=2>I then placed the model between constraints at = each end and loaded the top.  As the load increased, the line on the spruce = showed me that tension in the top was decreasing.  I loaded the model to failure.  The rib failed first, and the failure was the most = beautiful textbook indication of a failure in tension on the top and compression = on the bottom (if you don't know what this kind of failure looks like, buy a = box of chalk and break a few pieces in different ways - the most interesting = is when you break it by twisting).  Because of one of Newton's laws, we = might deduce that the soundboard was experiencing equal and opposite loads = when the rib failed.</FONT></DIV> <DIV><FONT size=2></FONT> </DIV> <DIV><FONT size=2>If you care to construct such a model, I'm sure = your results would be similar.  If you would like to see pictures, I will = consider putting them up on a photo site.  If the actual physical = demonstration of the main point I am arguing does not convince, then I fear we must = promote this discussion to the level of religion where issues are resolved on = the basis of faith and personality.</FONT></DIV> <DIV><FONT size=2></FONT> </DIV> <DIV><FONT size=2>Frank Weston</FONT></DIV> <DIV> </DIV> <DIV><FONT = size=2>-----------------------------------------------</FONT></DIV> <DIV> </DIV> <DIV><FONT size=2>Good grief, man, the top piece did not = "stretch," you wrapped it around a larger circle! </FONT></DIV> <DIV><FONT size=2></FONT> </DIV> <DIV><FONT size=2>I am working on a similar experiment.  The = results and conclusions will be posted later.</FONT></DIV> <DIV> </DIV> <DIV><FONT size=2>In the meantime, if you really want to understand = this subject, I would suggest that you take the results of your experiment = and discuss them with a local engineer.  Perhaps he/she can think of = some example that will convince you of the error of your ways.</FONT></DIV> <DIV> </DIV> <DIV><FONT size=2>Regards,</FONT></DIV> <DIV> </DIV> <DIV><FONT size=2>Del</FONT></DIV></BLOCKQUOTE></BODY></HTML>