Hi Terry, some pianos (grands too) use a different angle then 90 degrees. Some by design...hehe...and some by acident me thinks. Bob Hoff wrote a nice series in the journal recently that touches on this..tho its more on the lines of finding the right bore length to fit any given piano configuration. And I think, if I am not mistaken thats set up for a 90 degree angle...I will have to recheck that tho.. in anycase it would be good reading. Your question as I understand it is more a question of action geometry then anything else. And I suspect you will get a few involved replies in that direction. Thats good too... cuz we havent really gotten so much into upright action geometry so much in the recent past. I look forward to some interesting responses... :) Farrell wrote: > Is there ever any good reason to bore a hammer on an upright such that the > long axis of the hammer & core and the shank form an angle less than 90 > degrees? I'm putting new hammers and butts on an upright and don't want to > repeat original mfg. errors. I should think the hammer/shank angle should be > exactly 90 degrees and the boring distance should be like on a grand - just > a hair longer than where the shank becomes parallel with the strings, just > to allow for a small amount of hammer wear. Original hammer core/shank angle > is about 88 degrees. > > (Why is there 1/2" of felt on the top half of hammer and about 5/8" on the > bottom? Did someone file the top only, or can gravity do that much? It makes > it pretty funny looking because you can see so clearly that the flat surface > of the string imprint at the strike point is centered well below the center > of the hammer core - a good argument for why we file the top AND the bottom > of hammers!) > > Or is it better to not hold to hard and fast rules and rather put new sample > parts on piano and see if it works better with the small angle? > > Close examination of the new Abel butts show that the shank hole is about a > half-shank-diameter toward the back of the piano from the original location > when the butt top is horizontal. So is it better to shorten the boring > length to make the shank parallel with the strings, or might it be better to > keep the boring length about the same and have the shank never quite get to > parallel with the strings (and thus exaggerating the present hammer/shank > angle) - but having the hammer hit the strings when it is perpendicular? > > A confusing array of possibilities here. I realize on the upright you likely > have a bit of geometrical leeway anyway, but even if I don't achieve > perfection, I want to push myself in that direction as far as is reasonable. > To do that I need to understand what perfection is (theoretical at least), > or our best guestimate of perfection. > > "It's always something!" > Terry Farrell -- Richard Brekne RPT, N.P.T.F. Bergen, Norway mailto:rbrekne@broadpark.no
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