>Your right, it would. I have noticed this while building soundboards. If >the bridge is flat it fights the crown of the ribs as it is clamped into >the case. I am no scientist and I don't have a degree in engineering but >it seems perfectly logical and consistent to machine the bottom of the >bridge to more or less follow the crown created by the ribs. I would think >this would add to the overall strength and durability of the whole >soundboard. I don't know what it does to the tone but a soundboard that >lasts longer will sound better longer. > >I have worked on many brands of grand pianos and have observed that some >pianos seem not to have this feature but the two brands that consistently >show evidence of bridge crowning are Steinway and Mason and Hamlin. John, How then does this correlate with the number of new Steinways we see (often enough on the showroom floor) with concave crown in the killer octave? It seems to me that if a crowned bridge is supporting soundboard crown and making it last longer, there ought to be soundboard crown to show for it. Especially in a new piano. >Newer ones will have more crown than old ones indicating that the crown >does dissipate over time but not as fast as the ribs. You lost me again. If the crowned bridge is helping support crown, and the bridge and ribs are both glued to the same panel, how can one lose crown faster than the other? I don't understand what you're saying here. >Besides it would be more difficult to plane a slight bevel to the bottom >of the bridge rather that cutting a crown into the bottom. Why? And why would it be considered necessary? Spruce is quite compliant, and will easily accommodate this. Are you saying that you hand fit each bridge exactly to the contour of each individual soundboard assembly, like fitting a pinblock to a plate? >Tilting the bridge in this way would also screw up the position of the >unisons moving them back. You mean like how the forward rotation of the bridge when you string it and the soundboard deflects under load screws up the unison positions by moving them forward? How much movement do you suppose you're talking about here? You can do the math, or I will. Whoever produces the numbers, they will be orders of magnitude smaller than the manufacturer's variation of speaking lengths measured on production Steinways. And if you're going to the trouble of making a bridge and cutting a crown in it, or not, don't you position it on the soundboard to produce the scale lengths you hopefully also went to the trouble to determine? >Who knows, maybe our predecessors in this business knew what they were >doing. After all they made a lot more pianos than we ever will. > >John Hartman RPT Who knows? I hope it's our job to know, or attempt to learn. Ron N
This PTG archive page provided courtesy of Moy Piano Service, LLC