>On another subject, I've read or heard that the total downward pressure >on the soundboard is about 1500 lbs., and that the approximate downward >pressure of one string on the bridge is about 7 lbs. 1500/240 strings >= 6.25 lbs. per string and 7 lbs. x 240 strings = 1680 lbs. total. , so >these two figures are in the same ballpark. That means a 42-string >bass bridge would have about 300 lbs. pressing down on it. Can that be >right? Many bass bridges are cantilevered out -- no matter how good >the glue joint, and even with screws into the apron from the back of the >soundboard, it seems that two 150-lb. people standing on the >cantilevered bass bridge would break it right off! > Dave. dnereson@dim.com I've read and heard all that too, with wide variations in figures, all guaranteed to be the real no kidding finally accurate figures. In the range of bearing angles you will find across bridges in pianos, the SIN of the angle * the string tension will give you a reasonably accurate bearing poundage. A string at 160 lbs tension, and 1° bearing angle, will provide a bearing load of 2.79 lbs. That same 160 lb tensioned string would have to be just over 2.5° bearing angle to produce 7 lbs of load. That's near five times the angle I'd think anyone should be putting on a cantilevered bridge, but that's my opinion and I don't like cantilevered bridges in the first place. They're hard on the soundboard structure. If you want a reasonably accurate total bearing load in any given piano, you need all the string tensions, bearing angles, and the time to either put it all into a spreadsheet or hand calculate individual string bearing loads and add them up. The information's available, but it's in kit form. <G> Ron N
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