Instability puzzler

[pianoguru at cox.net]

---- Jon Page <jonpage at comcast.net> wrote: 
> Back when I was tuning full time, I found that Yamahas in particular 
> were a problem
> at the area. On a thread regrading that many years ago, I think it 
> was Ron O who suggested it was probably due to the difference of % 
> breaking strain across the strut.
> A scaling problem basically.

This is a common enough scaling problem, but one that can be overcome.  With a sufficient dogleg in the bridge, the speaking lengths can be maintained at an ideal incremental value as between notes not divided by a plate strut.  With vertically laminated bridges, where it may be impractical to bend sharply enough to achieve this, the dogleg can be smoothed out a little, and the back bridge pins moved forward on one side of the break and back on the other, maintaining the same angle for side bearing, leaving the bridge pins comfortably positioned on a bridge that does not quite follow the shape implied by the bridge pin pattern.  I never change wire gauges at the break, which would compound the differences in beak %, tension, etc., at this critical point.  In some designs where the note on the bass side of the strut is allowed to be longer than ideal, the increment of wire gage is reversed, using a smaller gauge rather than what one would otherwise expect, an ever increasing wire gauge as you go further into the bass.   Most of the above is only useful in designing or rescaling, but I have used a smaller wire gage across the break in instances where I was not doing major bridge work on a rebuild.

Frank Emerson