----- Original Message ----- From: "James Ellis" <claviers@nxs.net> To: <caut@ptg.org> Sent: Saturday, December 20, 2003 1:31 PM Subject: Touch Weight > 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. Inertia is not a "quantity" at all, it's an effect. Inertia is simply a fundamental property of matter that causes it to want to stay at a constant velocity and in a straight line. The is no unit of "inertia". > Inertia is proportional to mass, but it is proportional to the square of > velocity. 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. You are apparently referring to kinetic energy, which is actually *half* the mass multiplied by the velocity squared. This is a property of an already moving object and is an energy term, not an inertial one. If you are looking for a quality of the hammer that indicates how it is affected by a force or an acceleration you probably mean the "moment of inertia". The hammer is a rotating object about a pivot point and the moment of inertia is sort of like its mass in rotational terms. For a point-mass it is mass multiplied by the distance from the pivot squared. Since there's no such thing as a point-mass in the real world, the m.o.i. must be calculated by considering the object in pieces and using standard formulas, or by measuring. Velocity is meaningless as applied to inertia. Acceleration is what causes forces and where the moment of inertia comes into play. Adding lead to any point on an object can only increase its m.o.i., never decrease it. The only way to decrease it is to either remove material, or change its geometry so that more mass is closer to the pivot point. If the lead is used as a counterbalance it can only overcome the effects of gravity, not inertia. Don A. Gilmore Mechanical Engineer Kansas City > Merry Christmas, Jim Ellis > > > _______________________________________________ > caut list info: https://www.moypiano.com/resources/#archives
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