[CAUT] restrung D

[Ron Nossaman]

>Now however, Ron has presented a
> compelling argument that tapping the pin down is a temporary fix at best
> (feel free to jump in here Ron when you get back home from SLC). A couple
> seasonal humidity shifts later and the pin will have risen back up. 

Hi Alan,
I'm back. We drove the full 1050 miles Saturday to take 
advantage of the weather forecast.

That's correct. The bridge changes height with humidity 
swings, and the hole the pin is installed in changes depth 
with it. The dry season (when false beating is most common) 
has the pin bottomed out in the hole, and the damp season 
(when false beats are least common) has the pin end above the 
bottom of the hole. As the hole bottom extends beyond the pin 
end, the cap is pushing the string up the bridge pin, crushing 
the notch edge, since the point of zero relative movement 
between the pin and the bridge tends to be around the glue 
joint between the cap and root. The only thing you do that 
effects false beating in seating bridge pins is to drag the 
string down with it to the notch edge.


>Not only
> that, because the pin is at an angle, over the seasons the string pushes up
> on the pin and in the process creats an oblong hole at the top of the bridge
> surface (flagpoling of the pin). Result? False beats. Cure? Quick and dirty:
> CA glue at side of pin opposite the string. Cure at rebuild? Very hard
> bridge cap with pins epoxied in, but with the pin not seated in the hole.

Regardless of the number of elaborate and often contradictory 
theories to the contrary, this model fits observable facts, 
and works better in real world application than anything else 
I've seen.


> The concept being that the tight fit of the pin at the surface of the bridge
> is what counts, not whether the pin is seated at the bottom of the hole. In
> fact, Ron says, a pin tight at the bottom, but flagpoling by a minute amount
> at the top is still a source of false beats. So the idea of testing the
> integrity of bridge pins by giving them a yank and assuming that, if they
> are tight they are still good, may not be an accurate test.

Too many times in my early years, following this advice left 
me with a new string job with all the old false beats of the 
old one, in spite of the newly dresses and shaped V bar. The 
ideas I offer in explanation of the problems we encounter with 
pianos didn't come out of a pickle jar last week. They evolved 
through thirty years of observation and experiment, refining 
understanding by making disappointing mistakes of following 
conventional wisdom based on nothing rational. A lot of years 
of experimentation and thinking went into this stuff, and what 
I present is my most current practical understanding of the 
problems and their probable causes.



> BTW, regarding that nick in the side of the bridge pins (caused by the
> string digging into it) that was the topic of a thread awhile back. Anyone
> have any thoughts as to the effects of this nick on tone and tuning? I'm
> guessing that the effect is negative for both (based on absolutely no
> experiment!)  But if my guess is correct, would a harder material for bridge
> pins be a good idea? Bridge pins are probably #2 steel plated with either
> copper or nickel, and nickel is harder than copper, right?

It surely has an effect of some sort on tone and tuning, or 
tuning stability. I just don't know to what degree. I haven't 
done a one to one comparison, and am probably not equipped to 
tell the difference in any qualitatively meaningful way in any 
case, since "improvement" is so apparently an individual 
assessment. Harder surfaces most likely couldn't hurt, and 
stiffer pins have proved (to me) in use to be better. So far, 
I've made a point of avoiding exotic materials to see how far 
pure design can be taken in elimination of the warts we 
battle. No special wire, no special bridge pins, no special 
agraffes or pressure bars. Epoxy laminated veneer bridge 
capping is something all rebuilders can make up and install 
themselves, and virtually eliminates the scrubbing of the 
string up and down the bridge pin with seasonal humidity 
swings, as nearly as I've measured so far. I expect to be 
doing more testing along those lines this year to nail this 
down more thoroughly. If this proves to be the case, that 
alone will eliminate the vast majority of pin contact wear, 
and notch crushing, keeping the bridge termination and 
accompanying tone production problems at a minimum to 
non-existent level for a very long time without the need for 
Titanium, Ebony, nickel plating, or anything more exotic. 
Again, my intent is to try to understand and state the 
underlying principals clearly enough to apply the simplest and 
most effective fix at the root cause, rather than a series of 
more elaborate and less effective "fixes" two or three levels 
into the "effects". In other words, the problem with the pin 
wear isn't strictly a problem. It's an effect of an underlying 
problem that may very well prove to be a non issue when the 
underlying problem is corrected.

It all connects.
Ron N