This is a multi-part message in MIME format. ---------------------- multipart/alternative attachment Hello Isaac (and everyone): Let me give you a concise grounding in how geometry and balancing = affects the inertial properties of an object. As I mentioned before, moment of inertia is due to a mass rotating at a = distance from a pivot and is proportional to this mass and to the square = of the distance from the pivot point. Simple; right? Well as long as = the mass has no physical size you're doing just fine. =20 Now let's talk about a metal rod spinning about one end. metal at the = middle of the rod is at one distance from the pivot and metal at the end = of the rod is at a larger distance, so the mass in the rod affects the = moment of inertia more and more as we go outward from the pivot point, = in fact it is affected as the square of the distance. If you think = about it, it gets scary. No matter how small a piece of the rod we take = into account, it still has some finite size and one end of the piece is = farther from the center than the other. But we have to have some size = (volume) or we have no mass! We would have to consider an infinite = number of pieces that are infinitely small and add their m.o.i.'s = together to get the total! =20 Impossible? Well, that's what calculus is for. By using integral = calculus we can do this infinitesimal sum (that's literally what = calculus is for) and come up with a nice, neat little formula for = calculating the m.o.i. of our rod. It turns out that it is a simple = little algebraic equation. Now this equation is only good for a = cylindrical rod pivoted at its end. For other shapes and pivot points = we would need to derive a different formula. "Now, Gilmore, how the hell is this helping me?" Well, now you have a = general idea of what affects an object's m.o.i. So when you go playing = around with an object's geometry, you'll know what you're doing. Just = remember that more mass or a wider radius both increase the m.o.i. and = the radius is the more extreme of the effects since it is squared. If = you are using small leads you can probably just assume that it is = approximately a point mass and figure its addition to the overall m.o.i. = by using m x r^2. Remember also that a mass' angular location has no = effect on its moment of inertia...only radius. So a lead weight can be = located anywhere on an object as long as it is the same distance from = the pivot. Now, about balancing. You can use a counterweight to "counter" the = effects of gravity by creating a teeter-totter effect. But this weight = can only increase mass and m.o.i. It just depends on what your goal is. = If you are worried about the weight of the hammer and its effect on key = pressure you can counterweight and partially, or completely eliminate = the weight. But even with no weight at the key, the m.o.i. will = determine what happens when you try to accelerate the object. Don A. Gilmore Mechanical Engineer Kansas City ----- Original Message -----=20 From: Isaac sur Noos=20 To: College and University Technicians=20 Sent: Sunday, December 21, 2003 5:21 AM Subject: RE: Touch Weight Vince,=20 I believe that you are also changing the moment of inertia with = changes in regulation parameters , attack angle of the keys, height of = the centers - while it does not make sense at first. I concur to say that the leading of the keys is not the way the action = can be lightened, or make heavier, it is quite simple to experiment with = leads using double sided tape and normal cylindrical leads, you can = experiment on many kind of setups. I believe that the action mass may match the pianists hand weight so = to be comfortable, finding the way to express those parameters in = numbers should certainly be useful. Best Regards. Isaac OLEG Pianotech=20 =20 Isaac OLEG accordeur - reparateur - concert 19 rue Jules = Ferry 94400 VITRY sur SEINE =20 oleg-i@noos.fr tel:=20 fax:=20 mobile: 033 01 47 18 06 98 33 01 47 18 06 90 033 06 60 42 58 77 =20 =20 =20 =20 =20 Powered by Plaxo Want a signature like this?=20 =20 Add me to your address book...=20 -----Message d'origine----- De : caut-bounces@ptg.org [mailto:caut-bounces@ptg.org]De la part de = madelyn mrykalo Envoy=E9 : dimanche 21 d=E9cembre 2003 03:10 =C0 : College and University Technicians Objet : Re: Touch Weight James Ellis <claviers@nxs.net> wrote:=20 Touch weight and inertia are NOT the same thing at all. "Tough = weight" is merely a measure of static force. "Inertia" is a dynamic quantity. Neither is front weight the same thing as moment of inertia, which = I have already said. That's why putting more leads closer to the center of the keys will result in less "KEY" inertia. You will have to use more lead, = but the "key" inertia will be a little bit less. However, the keys are NOT = where most of the total action inertia comes from. It comes from the = hammer heads out on the ends of the shanks, because that's where the = (mass x velocity squared) is concentrated. All I'm saying is that moving the leads closer to the centers of = the keys is not going to buy you very much, because that's not where most = of the total action inertia is coming from in the first place. But then that is the only place we can change the moment of = inertia, unless we lighten the hammer. What it will do is weaken the keys, especially if you drill more holes, plug holes, = etc. That's probably not going to be a problem. Those two things are about all it will do for you, other than just = making the keys heavier in the middle. So, before you haul off and re-do = a whole set of keys, drilling more holes, adding more leads, plugging = holes, and moving all the leads closer to the center, remember: It won't buy = you very much towarding lowering the overall action inertia, because that's = not where it's coming from, but it will definitely weaken the keys. If we are going to change the front weight anyway, because we are = also changing out hammers, the MOI might as well be dealt with then too. Merry Christmas, Jim Ellis _______________________________________________ caut list info: https://www.moypiano.com/resources/#archives Vince Mrykalo University of Utah=20 -------------------------------------------------------------------------= --- Do you Yahoo!? New Yahoo! Photos - easier uploading and sharing ---------------------- multipart/alternative attachment An HTML attachment was scrubbed... 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