Bridge caps

[jolly roger]

 but this should be a pretty good indication that the
>bottom of the pin doesn't move in the bridge, while the bridge expands and
>contracts relative to the pin bottom making the top of the bridge slide up
>and down the pin, carrying the string along with it.     

Hi Ron, 
          Your observations give an excellent eplaination of why there is a
need to seat strings periodically on performance piano's.  This movement of
the bridge and cap, is one of the things that attracted Conklin to the use
of vertical laminations.
FWIW,  I have found far less bridge related problems with the Baldwin
system than on more traditional bridges. The failure's encountered have
been more glue related.
You really got me thinking. (Ouch it hurts.)  
I wonder what the change of dimension is on the pin for a 15F swing in
temperature. Rate of change temperature vs humidity vs material will enter
the mix.
Suprising that any thing ever works in a piano, given our lack of full
understanding of all the variables.
Now I will crawl back under my rock.
Roger