Hi Ron: This makes more sense than anything I have seen to date. If true, it could be measured with a depth gauge in summer and winter to verify. Jim Coleman, Sr. On Mon, 14 Apr 1997, Ron Nossaman wrote: > Interested participants, >=20 > I'd have to go with Bob Davis and Jim Coleman Sr. on this one.=20 >=20 > Further thoughts: Playing with my third tuning today (K.Kawai grand), I w= as dinking around with the false beats I was getting in octave 6. ALL of th= e beating strings cleared up with a slight pressure on the side of the brid= ge pin opposite the string. Gotta be loose pins. Light seating helped on SO= ME of the beaters, not all. Probably floaters, got them down where the hori= zontal scrub on the bridge overcame pin flex. While playing with this, I th= ought of another possibility as to how strings get up on bridge pins.=20 >=20 > When a pin is originally driven into the bridge, the part of the hole tha= t has had the least amount of pin pushed through it is the very bottom. Sin= ce the bottom of the hole experienced the least wear and trauma with pin in= sertion, it ought to have the tightest grip on the pin, with the loosest fi= t 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 bridg= e dries and shrinks, the string stays up. Meanwhile, the extreme sidebearin= g 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 o= f the hole, at a side pressure somewhat less then the string sidebearing f= orce (minus spring of pin), with each cycle. No wonder the holes oval out a= nd 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 groove= d 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 b= ridge 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, i= t just makes it possible for the bridge to crush itself. I like this explan= ation. I think it's logical and simple - Ocham's Razor -. The simplest exp= lanation is probably the correct one. What do you think? >=20 > With some trepidation, Ron (simple, ask anyone) Nossaman > =20 >=20 >=20 >=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 > > > > >=20 > Ron Nossaman >=20
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