On Fri, Apr 2, 2010 at 8:22 PM, David Nereson <da88ve at gmail.com> wrote: > > > >> What would the pivot be? What actually twists -- the whole >> wooden frame (of an upright)? Then you'd think two diagonally >> opposing casters would come off the floor. Or that the plate >> would crack from the strain, in an upright or a grand. Or that >> the top and bottom panels would rub and not fit properly at >> certain times of the year. By "structure" do you mean the >> wooden back (top beam, bottom beam, backposts); or in a grand, >> the rim, belly rail, and radiating beams? Or are you including >> both the rim and the plate? How much can the plate twist >> without cracking? >> Not challenging anything here, since I'm not a >> designer/rebuilder -- just trying to understand so I can tell >> clients what's really happening. >> There also was an article years ago about bridge elongation >> down in the low tenor, by Fandrich, I believe, but I never >> understood how the bridge could elongate when it's glued to the >> soundboard, unless they elongated equally (unlikely, with one >> being maple and the other spruce). >> Confused, --David Nereson, RPT >> >> > I imagine the treble strut itself is acting as some sort of pivot, since after the humidity change the pitches of the notes on either side move in opposite directions. When I say I think the structure is flexing and twisting I don't mean to the degree that you would actually see it happen. ( Although we do find in old uprights that one wheel is often spinning! And obviously some older pianos pull their pinblocks loose) Since everything in the piano is connected - Rim, beams, plate, pinblock, etc. it makes sense to me that it is all moving around to *some *degree. I would not venture to say how much or how significant a role each component plays. Sounds like a job for some inspired grad student! -- Ryan Sowers, RPT Puget Sound Chapter Olympia, WA www.pianova.net -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://ptg.org/pipermail/pianotech.php/attachments/20100402/99078662/attachment.htm>
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