But Richard, the hammer produce resonnance of the board, at its own resonnant frequencies, while certainly less efficiently than a generator, so I believe that is the same effect and the same name for the sand pictures . Greetings Isaac OLEG Entretien et réparation de pianos. PianoTech 17 rue de Choisy 94400 VITRY sur SEINE FRANCE tel : 033 01 47 18 06 98 fax : 033 01 47 18 06 90 cell: 06 60 42 58 77 > -----Message d'origine----- > De : pianotech-bounces@ptg.org > [mailto:pianotech-bounces@ptg.org]De la > part de Richard Brekne > Envoyé : lundi 20 octobre 2003 22:41 > À : Pianotech > Objet : Re: Soundboards: Thickness and Area > > > No no no... we are not talking Chladni patterns here Cy. But you are > right that they are dependant on the Frequency of the vibration. > > But in this case you are not providing the soundboard with > a particular > frequency per se... you are just hitting the bridge with a hammer or > something... as in one time every second or two.. > > A Chladni pattern require an input frequency that > corresponds to one of > the soundboards resonant frequencies. > > Cheers > RicB > > > > Cy Shuster wrote: > > > > Don't these Chladni patterns depend on the frequency of > the vibration? See, > > for example: > > > > > http://www.kettering.edu/acad/scimath/physics/acoustics/imag > es/chladni-dat.gif > > > > It's the last project on this page: > > > > http://www.gmi.edu/acad/scimath/physics/acoustics/projects-s.html > > > > Or is it different because the edge of the panel is > already glued down? > > > > --Cy Shuster-- > > Rochester, MN > > > > ----- Original Message ----- > > From: "Richard Brekne" <Richard.Brekne@grieg.uib.no> > > To: "Pianotech" <pianotech@ptg.org> > > Sent: Monday, October 20, 2003 10:49 AM > > Subject: Re: Soundboards: Thickness and Area > > > > Apprapoe freeing up the edges of the board Dale, > > > > One of the segements of Steingræbers lecture in Helsinki this past > > weekend was about this. He showed a few pictures of how > they go about > > this at their factory and breifly discussed some of the > goals in their > > proceedure. > > > > They spread dark sand on the panel and then pound a bit > on the bridge to > > see where the sand settles. They remove material from the > soundboard > > until the sand accumulates in a very clearly defined thin > boarder line > > about the edges of the entire soundboard. They are particularily > > concerned with the K point area which corresponds to the > area in the > > treble where the so called killer octave phenomena occurs. But all > > around the edge of the soundboard they want a precisely > defined line of > > sand. > > > > Tho he didnt mention it, the pictures also revealed an > accumulation of a > > line of sand just at the leading edge of the bridge as > well. I didnt get > > a chance to ask him if that was done on purpose or not. > > > > Cheers > > RicB > > > > > Erwinspiano@aol.com wrote: > > > > > > Glenn > > > You're asking the hard technical questions. My > engineer friend say > > > that when his friends get picky with details the > comment is "hey your > > > not building a piano ya know" I take that as a > compliment. In this > > > case we are but fortunately board thinning isn't a > mystery. It however > > > helps to have an organized approach to thinning. If you > ask 5 belly > > > guys how they do it you'll get five different answers. > > > The amount of thinning depends on what your goals is > & what you > > > think is benifiacial to freeing up the edges of a > board. The thinning > > > in most regimines includes thinning along the > spine(straight side), on > > > around the tail around the curve and stopping short of > the top treble > > > area which needs no or little thinning. > > > Some also thin along the belly rail up to the offset of the > > > board ,which is sometimes desireable depending on the > overal thickness > > > of the board to start. > > > Thinning is mostly restricted > > > > > > > > > > -- > > Richard Brekne > > RPT, N.P.T.F. > > UiB, Bergen, Norway > > mailto:rbrekne@broadpark.no > > http://home.broadpark.no/~rbrekne/ricmain.html > > http://www.hf.uib.no/grieg/personer/cv_RB.html > > _______________________________________________ > > pianotech list info: https://www.moypiano.com/resources/#archives > > > > _______________________________________________ > > pianotech list info: https://www.moypiano.com/resources/#archives > > -- > Richard Brekne > RPT, N.P.T.F. > UiB, Bergen, Norway > mailto:rbrekne@broadpark.no > http://home.broadpark.no/~rbrekne/ricmain.html > http://www.hf.uib.no/grieg/personer/cv_RB.html > _______________________________________________ > pianotech list info: https://www.moypiano.com/resources/#archives
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