tapping strings

[Ron Nossaman]

>If the string isn't in contact with the front (keyboard side) of the bridge,
>could this indicate that positive bearing was exaggerated at "high tide"
>(maximum moisture content), resulting in damage? This is perhaps the sole
>instance where I can agree that, although there is no contact with the front
>edge of the cap, there's still positive bearing.

Ron,
You're at a university. Find yourself an engineer you can believe to
compute the amount of pressure it takes to push a string at 160lb tension
vertically up a bridge pin against a 10° pin tilt and a 20° side bearing.
Compare that number to the downbearing force that same 160lb tension string
exerts on the bridge edge at 1°, 2°, 5°, or any other extreme downbearing
angle you are likely to find in a piano. 

A quick graphic: In a treble bridge with the strings off and bridge pins
out, lay about a 1.5" length of #13 (smaller diameter than was originally
there) in the string groove. With a small screwdriver, scale, piece of
wire, or whatever, press down slightly to keep the wire in the groove.
Slide your screwdriver from the center of the bridge to the edge and
observe the angle between the bridge top and wire as it changes.
 
Ron N