Bridge pin spacing (was Baldwin SD-10)

[Ron Nossaman]

>Newton, Del, Ron O, Ron N and other scholars out there,
>This might seem like an over-simplified question, but what factors in
>scaling determines the optimum width of a bridge and the facing in the first
>place? I have  always pondered the reasoning behind the broad width bridges
>vs. some of the extremely  narrow bridges found in all types of pianos.
> Having rebuilt oodles of instruments, the good, bad, and the ugly, I have
>yet come to a conclusion as the "why's" vs. the "how effectives" are each
>design.
>Tom Servinsky,RPT

There really isn't a simple answer either. Stiffer and heavier are
determined by width and height, like with any beam. The impedance of the
soundboard assembly at any point in the scale is determined by the mass and
stiffness of the assembly, as seen by the strings at that point. Scale
tensions, soundboard panel thickness and grain direction, rib dimensions
and placement, rim stiffness and proximity to the bridge will all have some
effect. Like everything else in a piano, everything affects everything else
in some way. Too flexible an assembly, and you get one big killer octave.
Too stiff and heavy an assembly, and you get a very quiet piano that
sustains for days. Something in the middle, and a considerable range of
something at that, is what you want. I've found that I can get enough
control of the process to produce the kind of sound I'm looking for with
panel and rib design without having to worry too much about bridge cross
sections. A couple of years ago, I replaced a 40mm wide bridge with a 30mm
wide bridge with a new soundboard and rib scale, and was very pleased with
the result. Since I haven't replaced a bridge with one of different
dimensions on the original soundboard, I can't say exactly what would happen. 

Ron N