Dennis Johnson wrote: [...] > I've been reinstalling leads as needed from the front (as the factory is > actually doing again now) but lately I've been wondering if perhaps the > idea wasn't completely foolish. I'm still trying to tell if its my > imagination, but I really think that I can feel the difference between one > lead at the very front and *slightly* more lead towards the middle, so > tough weight is the same. As much as I am irresistably attracted to using > less lead, I think that maybe the other example actually starts smoother. > Was this really a sound idea that unfortunately got blasted due to other > weight/geometry problems? > Once again I will raise the dreaded moment of inertia to answer this one. There is a difference. The static (touchweight) is based on the first moment of the key about the pivot and varies as the distance between lead mass and pivot. The dynamic (feel) of the key is based on the second moment (moment of inertia) and varies as the square of the distance between lead mass and pivot. Thus when you move the leads to the middle of the key and *slightly* increase to balance the touchweight you reduce the moment of inertia significantly (even though the leads are a bit heavier)...hence the key feels different. Another analogy...golfclubs are (or used to be) sold in sets which were statically matched (i.e. the first moments about the grip were the same)...called `swing weight', which is identical to D.Stanwood's strike weight! Recently some manufacturers started making sets that are dynamically mateched (i.e. the second moments are the same). You can't match both first and second moments, because one varies in proportion to distance whereas the second varies as the square of the distance. My 1937 Hamburg Steinway has had key leads added sometime before I acquired it...these are quite near the front of the keys and the action has always seemed a bit `clunky' to me, presumably because of the position of the leads. Would like to remove them altogether, but not being a (modern piano) technician I'd probably mess up the whole action doing so. Stephen Birkett (Fortepianos) Authentic Reproductions of 18th and 19th Century Pianos Waterloo, Ontario, Canada tel: 519-885-2228 fax: 519-763-4686
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