>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
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