False Beats

[Ron Nossaman]

>Ron
>It also seems like its almost impossible to avoid as it would require a
>perfect fit all along the length of the bridge pin in the bridge wood, and
>this fit (if it can be so acurately bored and pinned to begin with) is
>going to be wrecked sooner or later by variance in climate through the
>years, the sideways stress on the pin, and a few other factors.

Not necessarily, and that's one of the points I'm trying to make. I don't
really think the fit at the bottom of the hole is even remotely critical. I
don't see how it could be. Pin movement has to occur where the pin meets
the string for this kind of false beat. The top of the hole takes the abuse
from string tension and movement, and gets loose long before any looseness
is evident at the bottom of the hole, which is under very little string
side pressure. In those pins I mentioned earlier that produced the false
beats, but were very hard to pull out, the bottoms of the holes were still
quite tight. It's the top of the hole that flares out into that bell shape
(thanks Ron), like the noisy end of a clarinet, because of string tension
and wood movement with humidity swings. 


>Adding CA or epoxy would seem to help to begin with, if done well, but I
>suppose in the end climate concerns would wreck this fit as well. As to re
>pinning with next size up pins. I am wondering if heating the hole so that
>the pin just fits in with an easy tap would be an idea ?? That way when the
>would cools down again it would expand around the pin and make a real tight
>fit ????

Like Don said, the epoxy or CA should soak into the wood and seal and
stabilize it somewhat. You're making a cellulose reinforced plastic collar
around the top of the pin, in effect. Even then, the wood will still move,
but perhaps won't crush the reinforced support collar as easily. As long as
the wood at the surface doesn't crush enough in the wet cycle to not
contact the pin in the dry cycle, the false beat won't come back. 

More on the oversized pins: If you think what was there was too small, by
all means go a size up. I don't like #6 bridge pins, and will replace them
with #7. Just drill them out before you drive in the bigger ones. Even if
the original hole is deep enough for you, 0.010" undersize is too tight
0.003" is more like it. I still don't think it's a good idea to replace
loose pins with oversized just because the originals are loose. I need a
better reason than that. 


>All this brings me back to the old... sheeshh... there has got to be a
>better way.. grin... One other question I am not clear on. Is it then
>necessary for the strings energy to be transmited deeply with in the bridge
>via some kind of insert (like the bridge pin) or could that be accomplished
>just as well by contriving some way of keeping the string "pressed" firmly
>onto the top of the bridge alone ?? (just musing a bit there..)
>Richard Brekne

It shouldn't make a whit of difference, hence my claim that a pin doesn't
have to be bottomed in the hole. you could terminate a string at the bridge
by wrapping baling wire around the bridge to clamp the string down and
probably get a decent termination. The energy transfer happens at the
termination, not past it. In the case of the loose pin false beat thing,
the termination isn't solid because the pin flagpoles.

Still my 2 cents.

Ron N