This is a multi-part message in MIME format. ---------------------- multipart/alternative attachment Ron O. wrote: "Look up your engineering handbook." 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. =20 "The paring (you might have a different term for it) at the ends of the = ribs...." 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. "By the way Terry, congratulations...." 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. ----- Original Message -----=20 From: "Ron Overs" <sec@overspianos.com.au> To: "Pianotech" <pianotech@ptg.org> Sent: Sunday, April 13, 2003 10:12 AM Subject: Re: Killer Octave Question >----- Original Message ----- >From: "Ron Overs" = <<mailto:sec@overspianos.com.au>sec@overspianos.com.au> >Subject: Re: Killer Octave Question > >SNIP > > > Sure the long bridge will rotate backwards >> on its axis (from end to end) just slightly to accommodate the crown >> of the board, but it will be so minimal as to be insignificant. > >Please try and clarify the above statement. Are you defining an axis=20 >going from the extreme treble end to the low tenor end of the long=20 >bridge? Then are you speaking of the two ends rotating backwards to=20 >meet the crowned board? I guess then one could speak of the killer=20 >octave area (or thereabouts) rotating forward if the the two ends=20 >are considered as reference points? If you imagine a line which passes through each end of the long=20 bridge, the bridge rotates around the axis of that line such that it=20 rises in the middle to accommodate the rising centre of the sound=20 board. When we started installing entire long bridges, we had it in=20 mind that we would crown the underside of the bridge to fit the crown=20 of the board, similar to John's suggestion. But when we built the=20 first basic bridge blank, we noticed that it fitted the board's=20 crowned profile almost perfectly as is. Consequently, we haven't=20 bothered crowning the underside of the bridge to this day. > > > The >> rib profile, 'stress in extreme fibre' and paring profile is where >> its at! > >I'm trying to understand this statement. Rib profile - OK, the=20 >shape/curve of the rib. Yup. >Stress in extreme fibre - what is that? Look up your engineering handbook. The chapter on beams as load=20 bearing structures has the info. The maximum stress in extreme fibre=20 is the loading within the beam which results from a given load (this=20 is always at a maximum at the top and bottom of the beam, and=20 virtually zero in the middle). After reading about the behaviour of=20 beams, take a look at any 1900 Bl=FCthner or Bechstein board with their=20 low 18 mm high sound board ribs. No surprises as to why they've sunk=20 out in the middle right under the long bridge. Its all about=20 excessive 'stress in extreme' fibre. >Paring profile - totally lost on this one - what is that? The paring (you might have a different term for it) at the ends of=20 the ribs have a marked influence over the tonal outcome. Have a look=20 under a few different pianos and think about what you see and how=20 they sound. By the way Terry, congratulations on your new venture into belly=20 work. Looking good. Ron O. --=20 _______________________ OVERS PIANOS - SYDNEY Grand Piano Manufacturers Web: http://overspianos.com.au mailto:info@overspianos.com.au _______________________ ---------------------- multipart/alternative attachment An HTML attachment was scrubbed... URL: https://www.moypiano.com/ptg/pianotech.php/attachments/55/1a/89/11/attachment.htm ---------------------- multipart/alternative attachment--
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