At 10:16 PM -0700 4/21/03, David Love wrote: > I don't really know how to handle the inertia question in a >quantifiable way--not yet anyway. There are those who are working on the >project, though, and it will be interesting to see what comes of it. If you are referring to Stephen Birkett (as you did in the original post), I'll let him speak for himself. Yes, he will produce the Mother of All dynamic grand action mathematical models. No, he didn't the Guild Foundation funding he'd been asking for five years ago, and the actual source of the funding will be the beneficiary of his work. What I know he told me in a private email, but I don't think I'm abusing his confidence. >I am reminded, however, of a presentation I saw some years ago by Rich >Baldassin. In short, he had a customer who complained of an action that >was too light. Taking lead out of the keys did not seem to solve the >problem adequately. Anyway, to make a long story short, he found that in >order to satisfy the customer, what was needed was to add two leads, one >behind the balance rail and one in front, equidistant from the center. The >net effect on the balance weight would have been zero, but the, presumably, >increase in inertia was what the pianist was looking for. I'd like to step back from your story and Rick Baldassin's, to reflect on how the three forces at work in an action, friction, gravity and inertia, have moved from dimly suspected, to regulated to specific targets, to (finally) ingredients in a soup which can be balanced to the taste of the chef (for a particular customer. Friction of course, is the "parking break" of the action, slowing the action down whether you're in forward or reverse gear. Gravity (BW) acts like a spring in that whatever the net balance of gravity between the two halves of the key, the force which the pianist applies in overcoming it on the downstroke is not lost but stored for the key's return. (Well, not completely like a spring which requires increasing force as you continue to deform it.) Inertia is only felt when the action parts change speed (ever heard of them changing direction, that is from their plane of rotation?). But Inertia is the toll-booth at the outset of play (and to a minor extent, a "use-tax" applied to any increase in speed that the pianist during the downstroke). All three forces of course are there at the outset, but as soon as the pianist gets the parts moving, inertia has been paid off. Mind you, as the other two forces exert their constant tax on the motion of parts, the pianist with find more acceleration required, simply to maintain level speed. Thus, the size of the other two forces will bring inertia back into play. But this is nothing compared to the amount of inertia encountered at the very beginning. In fact, I've always thought of inertia as a vanishing brick wall. When the pianist's finger strikes the key, its own velocity (considerable) goes smack into the dead zero velocity of the key and the parts loaded on it. There is a momentary squashing of the finger as the key picks up speed, but as soon as the two match, inertial resistance disappears. Starts out as a brick wall, and after a few miliseconds, it's gone. Which is not to say that the energy poured into the parts to overcome inertia is lost. Like the energy to overcome gravity, it is simply stored temporarily in the parts. Fifteen years ago, action friction was a matter of a long list of preparatory steps, which when executed would put a Good Housekeeping Seal of Approval on the action. One or two people had suggestion that it could be inferred from Down and Up Weight, but they were few and far between in a world of techs for whom action resistance was DW and nothing more. Since then, it's been possible to determine whether friction is a matter simply of good housekeeping or instead, heavy hammers. Also David Stanwood's friction control shanks have allowed quick exploration of different levels of friction on the action and the pianist. The same thing can be said for his adjustable helper spring, in experiencing different levels of BW. If you buy David's assertion that FW is a good measurement (albeit static) of inertia (and I do), we're now at the point where all three can be set to specs, and two out of three can be reset on the fly. Fifteen years ago, we didn't have that. Now we do. It's a brave new world. But just to keep things sober and in perspective, all of this pertains to the mechanical aspect of the action's "feel". It doesn't directly accomplish anything for the sound of the piano, which is where the art and the gift in our business lies. Confusing the issue here is that fact that when pianists report that an action feels good, they mean that getting the sound they want out of the piano is easy. They don't have to hunt for the sound they don't have to struggle to draw it out. The set-up of the action may contribute to the sound mainly in the absence of work done wrong, but for the most part the sound comes from the condition of the hammers and the belly. That's another ballpark entirely. Bill Ballard RPT NH Chapter, P.T.G. "Talking about music is like dancing about architecture" ...........Steve Martin +++++++++++++++++++++
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