Inertia Heads, I have a little more to report on measuring the MOI of the action parts. A friend brought this method to my attention and I am very grateful for his help. A method based on the principles of a physical pendulum can be use to measure the MOI of odd shaped parts. I have been trying this out on some grand keys. I think it may be more accurate than the estimating method I proposed before. I compared using the estimate with the pendulum method and found a discrepancy of 8.5%. So our estimate is not too bad after all. Note C40 M&H BB with two leads in the key. Estimated MOI = 25077gmcm^2 Measure MOI = 27389gmcm^2 More on this later. 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]
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