<!doctype html public "-//W3C//DTD W3 HTML//EN"> <html><head><style type="text/css"></style><title>[Files] Re: B 458198, string deflections</title></head><body> <div>Hi Kent and all,</div> <div><br></div> <blockquote type="cite" cite>Following up:</blockquote> <blockquote type="cite" cite><br></blockquote> <blockquote type="cite" cite>My observations do not confirm the presence of significant grooving on the bridge, no evidence of aggressive string seating, just some scuffing as the route of the string over the bridge changed. Try this view and note that the damage to the bridge is more obvious:</blockquote> <blockquote type="cite" cite><br></blockquote> <blockquote type="cite" cite><a href="http://tinyurl.com/dkjo2">http://tinyurl.com/dkjo2</a></blockquote > <blockquote type="cite" cite><br></blockquote> <blockquote type="cite" cite><a href= "https://www.moypiano.com/ptg/files/attachments/9f/c1/94/30/dscn1194.jpg" >https://www.moypiano.com/ptg/files/attachments/9f/c1/94/30/dscn1194.<span ></span>jpg</a></blockquote> <blockquote type="cite" cite><br></blockquote> <blockquote type="cite" cite>I'm still convinced that the high angle of string off the backscale side of the bridge is a source of the damage. The pins along the speaking length side of the bridge do not show significant movement.</blockquote> <div><br></div> <div>I totally agree with you Kent. Excessive string angle is almost certainly the primary cause of failure of this bridge. Its not only a poor layout but it is poorly executed. Look at the second-note-from-the-left pin group. You'd be hard pressed to find any more careless  bridge pinning anywhere. And this manufacturer still claims to be building world class pianos - I very much doubt it. Notice also that the deformation of the left-rear bridge pins (as viewed in the above links) appear to be exhibiting greater deformation than the right side unison bridge pins. The bridge pins are laid with a relatively close spacing of the unisons (although there are more severe examples of this than the bridge shown). This allows bridge-pin failure to sort of stack up, with the greater movement being in the pin which is being forced towards the other two bridge pins. I've noticed this before from various manufacturers who should have had better corporate memory, since they've on occasions reverted to this inferior layout after doing it better at a previous time.</div> <div><br></div> <div>Ron N's post which includes vector force calculations for the various pin angles shows why such poorly laid high-offset bridges fail more.</div> <div><br></div> <div>Ron O.</div> <x-sigsep><pre>-- </pre></x-sigsep> <div><font face="Times New Roman" size="+1" color="#0000FF"><b>OVERS PIANOS - SYDNEY</b></font></div> <div><font color="#000000"><i>   </i></font><font color="#0000FF"><i>Grand Piano Manufacturers</i></font><font color="#000000"><br> _______________________</font></div> <div><font size="-2" color="#000000"><br> </font><font color="#000000">Web http://overspianos.com.au</font></div> <div><font color="#000000">mailto:ron@overspianos.com.au<br> _______________________</font></div> </body> </html>