string seating - was bridge caps

[Ron Nossaman]

>I have no doubt that the bridge is moving, what I questioned was whether 
>this was
>the reason (or how much of the reason) for the string indentations. As I 
>said, with
>positive down bearing it would seem to me the same indentations would come 
>about
>anyways. Grin... 

The difference between static downbearing and bridge swelling bridge
grooving should be pretty dramatic. Downbearing at 1° and 160lb is a little
over 9 lbs. The resistance to the string being pushed up the bridge pins
has to (not should be, but HAS to) be considerably more. Where are all
those engineers that abandoned all that expensive training to take up piano
thumping? Someone please come up with the math for this one. I'd really
like to know how to compute this.


>I suppose you wouldnt mind explaining the significance of 
>1470 psi
>here...

Fiber stress proportional compression limit for hard maple... what else?



> If you get a chance you might describe your experiment a bit for us.

I had the chance, and have already posted it for Paul when we were talking
about pin height above the bridge surface. Weren't you paying attention?



>as long as we have enough positive downbearing.. I cant see how it could
escape
>from doing so. But I will certainly buy that if there exists a point on the 
>bridge
>that is lower then a line drawn between the maximum deflection and the 
>termination
>points, then forcing the string down at this point will most definitly 
>create the
>problem you described...

That's what I'm thinking.


>I think I see your point well enough. As I understand it thats the basic 
>reasoning
>behind seating pins by tapping lightly between the pins. Whatever seating is 
>needed
>and / or benificial will be taken care of in this manner. Pressing or tapping
>outside the bridgepins risks damaging the bridge as well as quite possibly 
>creating
>this temporary situation you describe.

But I don't see how tapping between the pin rows can do anything at all
unless the strings are driven into the bridge until the groove underneath
is nearly flat from notch to notch. Again, that's my point. 



>I still see a need to seat strings on bridges tho... but I dont really think 
>the
>reasons for this are at odds with your points here.

I don't see the need, and I do think my reasons are at odds with the
perceived need, which is what the whole thing is about.



>I wasnt really challanging it... just didnt quite get your meaning. Still 
>unclear
>as to how this in itself can cause a false beat, if thats what you were
saying.

Yea, challenging wasn't exactly what I meant.. questioning. The cause of
the beat would be that the string is touching the top of the bridge to
within "X" distance of the bridge pin, but not *at* the pin. On the
vertical axis of string excursion, the termination is past the bridge pin
and farther in on the cap. On the horizontal axis, the termination is the
bridge pin, but if the pin isn't tight in the top of the bridge, it will
flagpole. The poor effective termination from the flagpoling causes the
beat as the termination moves left and right with pin flex. The termination
at the bridge top not being at the pin makes this horizontal movement
possible.  


>What would happen I wonder if you took oversized bridgepins, and notched them
>purposely to hold the string in place vertically....grin..

That might actually work very well.


Ron N