>Hi list, > Does anyone still have the original lowell downbearing gauge >instructions , that tell what the scale markings are supposed to be >calibrated to? For fun I went to the Baldwin class at Sparks and the >Baldwin people disagreed with Mr. Lowell as to the actual degrees that >the bubble markings corresponded to. But I can't find my notes, >soooooo............... > >Thanks > >Dale Fox Here you go Dale, Tom sent me this some time back. In brief, the thousandths of an inch quantities represented by the linear increments (division lines) on the gauge are the rise or fall (vertical dimension) per inch of length of piano string. So, to give an example, if your rear string length was 3" and your gauge measurement was .009", then the difference in elevation between the top of the bridge (a reference at zero), and the rear string rest would be 3" x .009" or .027". Very simple math. These dimensions can be converted to degrees of angle by multiplying 1/6 degree times the number of division lines the bubble has crossed. Crossing six division lines would mean 1 full degree of string angle. More simple math. To determine the lbs. pressure from the net downbearing measurement multiply the net bearing in thousandths of an inch by the tension of the string. For example, a string of 200 lbs tension, deflected by the bridge so that a net downbearing measurement of .018" (1 degree) is created, will produce a downbearing pressure of 3.6 lbs. (200 x .018). More simple math. Incidentally, the bridge is pushing up at the string 3.6 lbs. at the same time the string is pushing down on the bridge, thus creating a static equilibrium, like a depressed spring. An understanding of trigonometry is unnecessary, but can't hurt anyone. Ron N
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