D. Stanwood wrote: > Your arguments are well founded and I have given them due > consideration in the past. Based on what you outline here, it > would be improper to use strike weight for calculations such as > moment of inertia etc. > I'm really saying more than that...using statically determined strike weights in *comparing* the dynamic behaviour of different actions may give slightly distorted results. F.i. because the bass hammer is wide (in the plane of its motion) it will dynamically not behave exactly as if all the mass were concentrated at the strike line. Thus the strike weights determined for the bass and treble hammers of the same piano will not strictly be comparable...in terms of the `effective' mass which hits the string. You did mention dynamic performance in your post on the metrology. > The strike weight measures make sense in that all modern pianos > are constructed in a like form, having the hammer mounted roughly > 5 1/16" out on the shank and the hammer bore distances are fairly > consistant from make to make. Anyone know of a piano with a 3" > bore? Relative to eachother, strike weight values may be used as > an effective measure of how much weight is being thrown into the > string, and our experience bears this out. > Experience is a good basis for ad hoc methods and what you say above would seem to indicate that the static/dynamic difference is not significant. To establish a metrology like this requires some up-front analysis to verify that the techniques are valid (as you have been doing of course)...I realize your requirements relate to practical day-to-day work, but once this is published someone else will point out what I've said...so I'm just suggesting that this point should be checked now, so that it's insignificance is verified quantitatively, and potential criticisms averted. > The same could be said for the downweight and upweight measures. > Crude but effective. Pianos weren't invented by physicists. > Things like what you speak of are very interesting but they don't > have much to do with the day to day chores of the piano maker or > technician, nor do the Pfeiffer books have much in the way of > practical information. As the piano developed it has really existed in a state of experimentation almost continuously...enough instruments were built by a maker that design features could be checked empirically. Now that manufacturing precludes such experimentation for the most part we should take advantage to the full of modern technology in analysing design features. I understand that day-to-day requirements are incompatible with complex analysis but that doesn't mean we cannot take advantage of the knowledge gained. The stuff on first/second moments, and also the Pfeiffer books, is really nothing more than pretty elementary physics. I don't find the Pfeiffer books very useful (and there are errors, f.i. his treatment of energy efficiency) precisely because they are too complex for `ordinary' purposes, but too simplistic to have any connection with realism. For the project I referred to earlier, I believe we can learn a lot about pianos using techniques from simulation in robotics engineering...I don't mean to suggest these as practical methods for the day-to-day technician. However I do believe it will eventually be possible to completely simulate the dynamic performance of a piano, from key to hammer and determine the acoustic behaviour exactly...all with nice computer animation to show the result. This is a *long* way off but the techniques are available now. 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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