Hi John: That formula you are using won't even get you anywhere close to the total moment of inertia. The second part is probably all right. You're assuming that the leads are small enough that they will perform like point masses, which will probably get you pretty close. But the first part (1/2ML^2) is wayyyy off. The formula you should use for a rectangular shaft that pivots at its center is I = 1/12 * m * (h^2 + L^2) where h is the height of the key, bottom to top. Good luck! Don A. Gilmore Mechanical Engineer Kansas City ----- Original Message ----- [link redacted at request of site owner - Jul 25, 2015] To: "Pianotech" <pianotech@ptg.org> Sent: Saturday, December 27, 2003 2:29 PM Subject: Moment of Inertia of grand action parts. > Inertia Heads, > > The next step toward understanding how the action works when actually > played is to find the total MOI as measured at the front of the key. > First we need to find the MOI of the key, wippen and shank. I thought it > would be useful to find ways to estimate this. The drawing shows a way > to estimate the MOI of the key. I have ways to estimate the MOI of the > wip and the hammer/shank as well but first I wanted to se if anyone else > had ideas on how to do this. > > We could use a variety of methods to measure the MOI directly like using > a torsion table or torsion pendulum. But these are difficult to build > and calibrate, more useful for demonstrating the principles of inertia > than for getting accurate measurement. Professional measuring equipment > is beyond my reach so for now the estimated MOI will have to do. > > After finding the MOI of the three parts the total MOI can be figured > with an equation. > > John Hartman RPT > > John Hartman Pianos [link redacted at request of site owner - Jul 25, 2015] > Rebuilding Steinway and Mason & Hamlin > Grand Pianos Since 1979 > > Piano Technicians Journal > Journal Illustrator/Contributing Editor [link redacted at request of site owner - Jul 25, 2015] > > ---------------------------------------------------------------------------- ---- ---------------------------------------------------------------------------- ---- > _______________________________________________ > pianotech list info: https://www.moypiano.com/resources/#archives >
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