string seating

[Ric Brekne]

A couple points here.

#1.  If as is argued otherwise, the bridge pins so firmly clamp the pins 
to the bridge the dynamics of the system dictate that this be if 
anything re-enforced rather then countered in any fashion, then why on 
earth can suddenly this reasoning reverse the whole claim and suddenly 
allow for strings finding themselves up the pins and away from the 
bridge after all ?.

# 2.  The only real way this works is to assume negative bearing and 
loose enough pins that will migrate. Yet that conflicts with real world 
observation which can show strings up the pins while both positive 
bearing and tight bridge pins are evident. We see this all the time if 
you stop and think of it.  Brand new pianos right out of the box.  Take 
off a few strings that needed seating and see how much notching there 
is... measure pin tightness... measure bearing...

#3.  The string under tension will not attempt to define a straight line 
across the top of the bridge. It will be forced in that direction by the 
bridge pins.  The string under tension will attempt to define as exact a 
fulcrum as it can, and will start exerting pressure onto the edges of 
the bridge to do so as soon as tension is applied.  The reverse of this 
condition is that the string being forced flat across the bridge by the 
pins will attempt to counter this and part of that countering is to 
exert an upward force on the string on the outside side of each pin. The 
edges of the bridge are essentially fulcrum points, and as with all 
levers... there is an equal and opposite leverage exerted on both sides 
of the fulcrum.

Cheers
RicB

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Because a past high humidity cycle, or fifty, with the friction of 
the string on the pin, has crushed the edge of the notch. The string 
under tension will attempt to describe a straight line between 
support points. Vertically, the support point on the bridge cap 
being somewhat back from the edge (because the edge was crushed by 
the pin friction BENDING the wire between the center of the bridge 
and the pin and putting the stress on the notch edge), the string no 
longer touches the notch edge.