<!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 6.00.2800.1106" name=GENERATOR> <STYLE></STYLE> </HEAD> <BODY> <DIV>Ron O. wrote:</DIV> <DIV> </DIV> <DIV>"Look up your engineering handbook."</DIV> <DIV> </DIV> <DIV><FONT color=#008000>I don't own one. Never opened one. I was a = geologist in a former life - never an engineer. Do you or anyone else have a = recommendation for a good basic nut & bolts Dr. Suess-level engineering reference = book. I guess if I'm going to build a rib I need to start understanding what = effect various dimensions, etc. will have on its performance.</FONT></DIV> <DIV> <SPAN id=__#Ath#SignaturePos__></SPAN> </DIV> <DIV>"The paring (you might have a different term for it) at the ends of = the ribs...."</DIV> <DIV> </DIV> <DIV><FONT color=#008000>Oh, you mean the taper of the rib from the = maximum height in the middle section to a lesser height near the ends. OK, gotcha.</FONT></DIV> <DIV> </DIV> <DIV>"By the way Terry, congratulations...."</DIV> <DIV> </DIV> <DIV><FONT color=#008000>Thank you very much for the comment on = APPARENT good progress. Perhaps best to save the congrats (if deserved) for after = we play the instrument! I do have very high expectations though. I gotta admit = that when I laid the ribs into their new notches and stood back for a moment, I = just about jumped out of my shorts. WOW! Happy boy..... for now.</FONT></DIV> <DIV> </DIV> <DIV>----- Original Message ----- <DIV>From: "Ron Overs" <<A href="mailto:sec@overspianos.com.au">sec@overspianos.com.au</A>></DI= V> <DIV>To: "Pianotech" <<A href="mailto:pianotech@ptg.org">pianotech@ptg.org</A>></DIV> <DIV>Sent: Sunday, April 13, 2003 10:12 AM</DIV> <DIV>Subject: Re: Killer Octave Question</DIV></DIV> <DIV><BR></DIV>>----- Original Message -----<BR>>From: "Ron Overs" = <<<A href="mailto:sec@overspianos.com.au>sec@overspianos.com.au">mailto:sec@= overspianos.com.au>sec@overspianos.com.au</A>><BR>>Subject: Re: Killer Octave Question<BR>><BR>>SNIP<BR>><BR>>  = > 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.<BR>><BR>>Please try = and clarify the above statement. Are you defining an axis <BR>>going from = the extreme treble end to the low tenor end of the long <BR>>bridge? Then = are you speaking of the two ends rotating backwards to <BR>>meet the crowned = board? I guess then one could speak of the killer <BR>>octave area (or = thereabouts) rotating forward if the the two ends <BR>>are considered as reference = points?<BR><BR>If you imagine a line which passes through each end of = the long <BR>bridge, the bridge rotates around the axis of that line such that it = <BR>rises in the middle to accommodate the rising centre of the sound = <BR>board. When we started installing entire long bridges, we had it in <BR>mind = that we would crown the underside of the bridge to fit the crown <BR>of the = board, similar to John's suggestion. But when we built the <BR>first basic = bridge blank, we noticed that it fitted the board's <BR>crowned profile almost perfectly as is. Consequently, we haven't <BR>bothered crowning the = underside of the bridge to this day.<BR><BR>><BR>>  > = The<BR>>>  rib profile,  'stress in extreme fibre' and paring profile is where<BR>>>  its at!<BR>><BR>>I'm trying to understand = this statement. Rib profile - OK, the <BR>>shape/curve of the rib.<BR><BR>Yup.<BR><BR>>Stress in extreme fibre - what is = that?<BR><BR>Look up your engineering handbook. The chapter on beams as load <BR>bearing structures has the info. The maximum stress in extreme fibre <BR>is the = loading within the beam which results from a given load (this <BR>is always at a = maximum at the top and bottom of the beam, and <BR>virtually zero in the = middle). After reading about the behaviour of <BR>beams, take a look at any 1900 = Blüthner or Bechstein board with their <BR>low 18 mm high sound board ribs. No = surprises as to why they've sunk <BR>out in the middle right under the long bridge. = Its all about <BR>excessive 'stress in extreme' fibre.<BR><BR>>Paring profile = - totally lost on this one - what is that?<BR><BR>The paring (you might = have a different term for it) at the ends of <BR>the ribs have a marked = influence over the tonal outcome. Have a look <BR>under a few different pianos and = think about what you see and how <BR>they sound.<BR><BR>By the way Terry, = congratulations on your new venture into belly <BR>work. Looking good.<BR><BR>Ron O.<BR>-- <BR>_______________________<BR><BR>OVERS PIANOS - SYDNEY<BR>Grand Piano Manufacturers<BR><BR>Web: <A href="http://overspianos.com.au">http://overspianos.com.au</A><BR><A href="mailto:info@overspianos.com.au">mailto:info@overspianos.com.au</A= ><BR>_______________________</BODY></HTML>