---------- > From: Richard Moody <remoody@easnetsd.com> > To: pianotech@ptg.org > Subject: Re: "Oval or Round Shanks" or to bend or not to bend > Date: Thursday, September 04, 1997 12:48 AM > > OK. So has anyone seen rectangular hammmer shanks? Well my > Chickering Anniversery Grand has 'em. I better measure, they might > be square. Hmm wonder if I can get replacements? > > Also just to open another can of worms, what does "stiffness > requirements of transferring the necessary energy to the hammer mass > of each note" mean? > The hammer can only do one thing as it approaches the string, and > that is acheive a certain velocity. If Newton's (Sir Isaac) Laws are > correct, full velocity is reached at the moment let off starts to > occur. The hammer is in acceleration to that point. In the space > past that point no acceleration can occur because the source of > energy has suddenly let off. Since this let off occurs some > distance from the string, the hammer must then be decelerating, or > loosing velocity as it strikes the string. Since let off is so close > to the string the deceleration must be miniscual (sp? a word?) so we > can envision the hammer velocity as the same at let off until > striking the string. > But is this what is really happening? Del suggests an idea by > bringing up the "stiffness" factor in the shank. Thus the hammer > might be decelerating (or not accelerating as fast as the key is > being pushed down) during the key blow because the shank is bending > as a reaction to inertia. Because the hammer shank bends and robs > the hammer of acceleration, this can be viewed as a waste of energy. > Perhaps the ideal shank would be one of ultimate stiffness, or one > that doesn't bend at all. > On the other hand, a bent hammer shank may possess potential energy > just as a bent bow ready to shoot the arrow. So perhaps after let > off, the bent shank tends to spring back and actually accelerates the > hammer onto the string. But maybe the paltry distance of 1/16 inch > let off isn't enough for the bent shank to respond with its fullest > energy potential. Maybe a let off of say, 1/4 inch would give more > space to allow more of this energy to be released. > Anyhow one can conclude that the let off of 1/16 (1.5mm) without > considering hammer shank flex, is only concerned with the idea of > most contact with the key to acheive the greatest velocity of the > hammer. In that construct, the hammer shank stiffness cannot be a > criterion. > > Finally all of the above is mostly moot if we want to consider the > most important phenomena, what happens to the string during and after > hammer contact? > > Richard The Space Jockey Dear Richard, On the Yamaha silent series pianos the let-off is set further away from the strings. I wonder if these pianos could be measured against normal let-off as far as de-celeration is concerned? James Grebe pianoman@inlink.com > > ---------- > > From: Delwin D Fandrich <pianobuilders@olynet.com> > > To: pianotech@ptg.org > > Subject: Re: "Oval or Round Shanks" > > Date: Tuesday, September 02, 1997 9:04 AM > > > > The > > hammershank is a beam. > > > > The best hammershank shape would be one that is rectangular--not > round > > or oval--right out to the end where it would have to be made round > to > > fit the bored hole in the hammershank. The cross-section of this > > rectangular hammershank, i.e., its width, could be varied as > required to > > meet the stiffness requirements of transferring the necessary > energy to > > the hammer mass of each note. > > > > --ddf > >
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