Just by looking at it I guess that if we have a radius that really move the fulcrum, the hole in the bottom of the key wear faster. I seem to notice that wear on some Steinway I've seen. I guess that the effect of the half round dowel is felt in the acceleration, not in the weight, even if it is a very little. Being very different on sharps than on white keys... Best 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 Sarah Fox > Envoyé : vendredi 2 mai 2003 04:38 > À : Pianotech > Objet : Re: Key Leads and Inertia > > > Hi John, > > > Thanks for your interesting post. I am saving it for future study. > > There's likely to be relevant stuff here, especially > about how some > > compliance could help efficiency. The impedance matching across a > > flexing beam (harmonic motion is a factor hear?) is > intriguing but this > > will take more time to sift down to a conscious layers. > > No, not harmonic motion. Impedance matching applies in > many physical > situations. It's basically a way to balance force/distance > tradeoffs or > voltage/current tradeoffs or so forth. In rather simplistic terms, > impedance is a reflection of the amount of force needed to > effect some sort > of change. In mechanical situations, impedance matching is > generally > achieved through some sort of mechanism that applies a > mechanical advantage. > For instance, in the middle ear, a large sound collection > area (the eardrum) > is used to collect airborn sound from the low impedance > side and transfer it > (with some degree of leveraging) drive vibrations over a > much smaller area > on the high impedance fluid side (the inner ear). > > > Were you some sort of circus engineer before heading into > piano (so > > called) technology? It looks like the clowns have better > R&D than us > > piano people. But I always thought this and now I know for sure. > > LOL! I think Steinway and Sons probably patented a number > of P.T. Barnum's > innovations. > > > It's not really the rail that is radiused it's a 1/2 > dowel covered in > > felt replacing the usual ring-o-felt balance rail > punching. The radius > > is about 6mm. > > Gads. Well, that answers my question: It was nothing more > than a marketing > gimmic. (Big surprise.) The change in mechanical > advantage from the key > rolling over a 6 mm radius would be miniscule -- really, > really miniscule. > Yes, it's enough to *technically* claim accelerated action > and get a patent. > But why bother? > > What I had envisioned was a very broad radius (dunno... > perhaps 25 cm or > more) that would shift the fulcrum point more > substantially. Of course this > would cause the keys to slide vertically on the balance rail pins > (slightly). I don't know if that would present a problem. > > BTW, I had another thought after I fired off my last post. > The springboard > mechanism used by acrobats also achieves something else. > Suppose a heavy > acrobat is to propel a light acrobat into the air (much > higher than the > heavy acrobat's original drop point). There becomes an > issue of where to > place the fulcrum, if a standard fulcrum is used. If it is > placed in the > center of the board, for instance, not all of the kinetic > energy will be > transferred, and the heavy acrobat will hit the ground with > a bump (wasted > energy). The fulcrum point would need to be off-center in > proportion to the > weight differential. At that point, there would be an > impedance match. > However, with the radiused fulcrum, placement is not > particularly relevant. > At some point in the roll, impedance will be matched. Full > transfer of > kinetic energy will occur. Carrying this lesson back to > the piano, how does > one design a piano's action to work equally well for the > light fingers/arms > of a 6 yr old student and for the heavy fingers/arms of a > large-framed man? > With a radiused fulcrum. Interesting application. > > > What's a "Wissner"? > > My piano -- an obscure make from the early 20th century -- > a very nice > instrument in need of lots of TLC. > > Peace, > Sarah > > _______________________________________________ > pianotech list info: https://www.moypiano.com/resources/#archives >
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