Mark Davidson wrote: > I made an attempt to relate hammer, wippen and key inertia to total > reflected inertia here: > > https://www.moypiano.com/ptg/pianotech.php/2003-August/140901.html > Mark, Thanks for sharing this with me. Just yesterday I came to exactly the same conclusion. I am doing a drawing to show the acceleration ratios of the wip and shank in relation to the key. The fact that we both came up with the same formula is encouraging but to be sure we need to have Don go over it. Have you plugged in the MOIs? It looks like the shank and hammer contribute about 12 times or more of the total I as felt at the key. If the formula is right it shows how unimportant changes to the key MOI is in relation to overall efficiency. Also, if there is any benefit to pattern leading it is not to make the action feel even from note to note. Adding lead to the key is not the big evil commonly thought unless it has some effect on repetition. I think we are going to find that the biggest problem with increasing the mass of the action parts is the losses due to bending and compliance. I still need to complete the kinetic model of the action but I can see ahead to the next step. Maybe you are already there. Is there a way to convert the kinetic forces developed at different levels of play into static loads. Then we can see how these loads bend the shank and key. It would be great if this could lead to a formula for finding the terminal velocity of the hammer. 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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