Interested participants, I'd have to go with Bob Davis and Jim Coleman Sr. on this one.=20 Further thoughts: Playing with my third tuning today (K.Kawai grand), I was= dinking around with the false beats I was getting in octave 6. ALL of the= beating strings cleared up with a slight pressure on the side of the bridge= pin opposite the string. Gotta be loose pins. Light seating helped on SOME= of the beaters, not all. Probably floaters, got them down where the= horizontal scrub on the bridge overcame pin flex. While playing with this,= I thought of another possibility as to how strings get up on bridge pins.= =20 When a pin is originally driven into the bridge, the part of the hole that= has had the least amount of pin pushed through it is the very bottom. Since= the bottom of the hole experienced the least wear and trauma with pin= insertion, it ought to have the tightest grip on the pin, with the loosest= fit occurring at the top, or entry point. The piano is strung and the= strings are seated on the bridge. With high summer humidity, the bridge= swells. It grows taller, the pin does not! The pin, gripped most firmly at= the bottom, has the top of the bridge literally sliding up it, taking the= string with it. Since the extreme side bearing of the string on the pin= puts the net (side&down) bearing angle at something near horizontal and= probably not far from 20 degrees from PERPENDICULAR (thanks Mike) to the= pin, when the bridge dries and shrinks, the string stays up. Meanwhile, the= extreme sidebearing makes the string very hard to push up the pin and= mashes a GROOVE in the top of the bridge. This movement also saws the= bridge pin against the top of the hole, at a side pressure somewhat less= then the string sidebearing force (minus spring of pin), with each cycle.= No wonder the holes oval out and the pins get loose at the top! If the= strings are tapped down when they are noisiest ( Winter, pianos get really= clear and sweet when the humidity's high and don't need it ), the bridge= top will again be more deeply grooved with the next high humidity cycle.= Even if they are tapped down as gently as possible, they will damage the= bridge on the next cycle! Epoxying the bridge pins in solidifies the column= of wood immediately around the pin and severely limits it's vertical= movement, relative to the pin, with humidity changes. If this is a good= model, the tapping isn't what does the damage, it just makes it possible= for the bridge to crush itself. I like this explanation. I think it's= logical and simple - Ocham's Razor -. The simplest explanation is probably= the correct one. What do you think? With some trepidation, Ron (simple, ask anyone) Nossaman =20 At 03:26 AM 4/14/97 -0400, you wrote: >> If there are false beats, then the vertical component of the string >vibration >> would have to vary cyclically.=20 >> Bob Scott > > Only if you explain false beats as amplitude modulation. Frequency >modulation makes more sense to me, as explained by Jim Coleman Sr. >(difference in speaking lengths in vertical and horizontal modes causes= pitch >change. This can be due to unclean notch OR bridge pin which wobbles in >horizontal mode, causing the string to act longer in that mode). > >Bob Davis > > Ron Nossaman
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