consistent downbearing measurements

[Ron Nossaman]

>The "angle" of deflection is a hypothetical construct.  If the profile of 
>the bridge surface was the peak of a triangle, you could speak of an 
>"angle" of deflection, however, distortions in the bridge surface 
>(curvature or string held to bridge contact by pins) can alter the angular 
>perception of deflection.

Not really. That's the whole purpose of using a bubble gage instead of a 
dial or rocker type gage. With the bubble gage, overall bearing is overall 
bearing, regardless of what the bridge top looks like. Overall bearing is 
what you're interested in when you want to know how much load the strings 
are putting straight down on the soundboard. Overall bearing is what you 
are comparing against remaining soundboard crown. Front and back bearing 
relative to the bridge top are termination concerns.


>Still, the challenge of accurately measuring and conveying  the nature of 
>a particular piano's string deflection, including the bridge, is, to me, a 
>separate question from how much or little there should be or how it does 
>or doesn't affect the instrument's qualities.

You'll never get an absolute answer to that one. Get five techs to evaluate 
a piano with a flat soundboard and zero-to-negative overall bearing at some 
point in the scale.. One will say the piano sounds terrible, and indicate 
the bearing and crown as likely causes. One will say the piano needs new 
hammers and voicing, and that the crown and bearing aren't indicative of 
anything at all. One will say that this is the most beautiful sounding 
piano he's ever heard, and you shouldn't change a thing. One will say the 
action needs bedding. One will say the piano is perfect without even 
lifting the lid or playing a key, just from the name on the fallboard.

Personally, I still think it's the casters.

Ron N