<!doctype html public "-//W3C//DTD W3 HTML//EN"> <html><head><style type="text/css"></style><title>Re: Killer Octave Question</title></head><body> <blockquote type="cite" cite>----- Original Message -----</blockquote> <blockquote type="cite" cite>From: "Ron Overs" <<a href="mailto:sec@overspianos.com.au">sec@overspianos.com.au</a>></block= quote > <blockquote type="cite" cite>Subject: Re: Killer Octave Question</blockquote> <blockquote type="cite" cite><br></blockquote> <blockquote type="cite" cite>SNIP</blockquote> <blockquote type="cite" cite> </blockquote> <blockquote type="cite" cite>> Sure the long bridge will rotate backwards<br> > on its axis (from end to end) just slightly to accommodate the crown<br> > of the board, but it will be so minimal as to be insignificant.</blockquote> <blockquote type="cite" cite> </blockquote> <blockquote type="cite" cite><font color="#800080">Please try and clarify the above statement. Are you defining an axis going from the extreme treble end to the low tenor end of the long bridge? Then are you speaking of the two ends rotating backwards to meet the crowned board? I guess then one could speak of the killer octave area (or thereabouts) rotating forward if the the two ends are considered as reference points?</font></blockquote> <div><br></div> <div>If you imagine a line which passes through each end of the long bridge, the bridge rotates around the axis of that line such that it rises in the middle to accommodate the rising centre of the sound board. When we started installing entire long bridges, we had it in mind that we would crown the underside of the bridge to fit the crown of the board, similar to John's suggestion. But when we built the first basic bridge blank, we noticed that it fitted the board's crowned profile almost perfectly as is. Consequently, we haven't bothered crowning the underside of the bridge to this day.</div> <div><br></div> <blockquote type="cite" cite> </blockquote> <blockquote type="cite" cite>> The<br> > rib profile,  'stress in extreme fibre' and paring profile is where<br> > its at!</blockquote> <blockquote type="cite" cite> </blockquote> <blockquote type="cite" cite><font color="#800080">I'm trying to understand this statement. Rib profile - OK, the shape/curve of the rib.</font></blockquote> <div><br> Yup.<br> </div> <blockquote type="cite" cite><font color="#800080">Stress in extreme fibre - what is that?</font></blockquote> <div><br></div> <div>Look up your engineering handbook. The chapter on beams as load bearing structures has the info. The maximum stress in extreme fibre is the loading within the beam which results from a given load<font color="#0000FF"> (this is always at a maximum at the top and bottom of the beam, and virtually zero in the middle)</font>. After reading about the behaviour of beams, take a look at any 1900 Blüthner or Bechstein board with their low 18 mm high sound board ribs. No surprises as to why they've sunk out in the middle right under the long bridge. Its all about excessive 'stress in extreme' fibre.</div> <div><br></div> <blockquote type="cite" cite><font color="#800080">Paring profile - totally lost on this one - what is that?</font></blockquote> <div><br></div> <div>The paring<font color="#0000FF"> (you might have a different term for it)</font> at the ends of the ribs have a marked influence over the tonal outcome. Have a look under a few different pianos and think about what you see and how they sound.</div> <div><br></div> <div>By the way Terry, congratulations on your new venture into belly work. Looking good.</div> <div><br></div> <div>Ron O.</div> <x-sigsep><pre>-- </pre></x-sigsep> <div>_______________________<br> <br> OVERS PIANOS - SYDNEY<br> Grand Piano Manufacturers<br> <br> Web: http://overspianos.com.au<br> mailto:info@overspianos.com.au<br> _______________________</div> </body> </html>