Dan Franklin wrote; >Some years ago at my first PTG National. . was a huge class by John Ford >Senior . . a dispute I had with Big John on the >question of bi chords. > >My point was : if you pull one side of a bi chord its bound to affect the >tension and the pitch of the other side. John adamantly disputed this saying >that the bearing points of the bridge pins, the agraffes, coils etc inhibited >this consequence. If you are referring here to two unison strings which are hitched via a single hitch pin then I'd say that John Ford was correct regarding the hitch pin. While the pull on one unison will indeed affect the rear duplex length of the same unison, the effect will not continue around the hitch pitch to the adjacent unison which is sharing the same hitch pin. Yes I know, I've heard many who dispute this also, but they are wrong provided that the string tension is not too different for the two unison strings concerned. Sure, if there's a huge tension difference there will be a tendency for the unison to pull around the hitch. But under normal scaling tension deviations, this is not an issue. And before Dan feels tempted to remind me again of my proximity to kangaroos, I might mention that Del has also written posts to this list which concur with my view. I would also add for Dan's benefit that I do not employ Kangaroos, apart from the fact that they have difficulty holding tuning lever, they are dumb. I prefer not to employ idiots. > Now transferred to the question of the duplex which you raised, this seems >to be a cogent point. . . I think you are probably right: that the >excitation of the >speaking length activates the duplex around the "trees" of the bridge pins, >hitch pins etc "activates the duplex around the "trees" of the bridge pins" - nice line Dan. I agree with you that considerable energy gets over to the rear duplex from the speaking length. This is I suspect why some manufacturers set their rear duplex lengths to a semitone higher than the harmonic of the speaking length (I have seen this done in a couple of high-end Japanese pianos, where they actually did a remarkably good job of locating the rear duplex block assemblies). In doing this, they would seem to be setting the duplex length to the harmonic of the adjacent note to reduce the tendency for excessive string energy to transfer to the duplexes. Ron O -- ______________________________ Website: http://www.overspianos.com.au Email: mailto:ron@overspianos.com.au ______________________________
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