Lowell guage

[Ron Nossaman]

>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