Dale writes: What do you find the average amount of over centering to be ie. no. of MM s the center of the hammer shank rises above the center pin height? Also I am most curious as to your subjective opoinion about what discernable differences in sound..if any? Ed Foote writes: >From the perspective of mechanical transfer of energy, this causes waste, in the form of heat and flex in the hammer and shank structure. Is it important? I can't say, but usually obedience to first principles ( in this case, energy is most efficiently transferred at 90 degrees), keeps efficiency at its maximum. My subjective opinion is that I get more power under FF when the hammer's axis drives directly into the string, but I have no way of measuring that. Yes, "obedience to first principles" is always the place to start. But some perspective: say an 8 gram hammer moving at FF impacts the strings at 90 degrees and at 40 pounds of force*. Here is what happens at each degree off of 90, whether under or over-centering. At 89 degrees the force has dropped to 39.99 pounds At 88 the force has dropped to 39.98 At 87 down to 39.95 At 86 down to 39.90 At 85 all the way down to 39.85 Thus, with a 5 degree "error" the force has diminished by 0.15 pounds; a 0.375% loss of force / energy / efficiency. Rather than significant power losses, the 5 degree error would likely cause strike-point-to-string-length issues in the shorter treble strings. *also 180 N as taken from a study of dynamic measurement of a piano hammer striking a piece of piano wire attached to the face of a force transducer Nick Gravagne, RPT Piano Technicians Guild Member Society Manufacturing Engineers Voice Mail 928-476-4143 -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://ptg.org/pipermail/pianotech.php/attachments/20100209/59e163c8/attachment-0001.htm>
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