New Bearing guges that don't lie

[Ron Nossaman]

>   How I think it works. According to Nick Gravagnes articles, if the 
> rear string length,meaning the string distance from the front bridge pin 
> to the rear rest is measured & multipied by.026, a distance bearing of 
> .104 is required to set up your string deflection of 1 &1/2 degree of 
> bearing.  In the picture below I have a 4 inch rear string length & a 
> residual distance bearing as measured at the gap between the string rest 
> & the bottom of the rocker foot of approx .050.  This indicates 3/4 of a 
> degree of  bearing. If you look closley the gap is very
> visiable.

The slope angle is a tad less than 0.018:1 per degree. So a 4" 
arm would need 0.070" gap per degree, so if you want 1.5°, 
that'd do it.

In Excel, it's DEGREES(ASIN(drop/distance))


>  The three gauges below were designed to work on the aliquot sections of 
> most Steiwnays.  Make your own based on the measuring device below.
>   Give me some feedback & tell me what your thoughts are.  This is in 
> the experimental stage so please chime in.
> *  Regards*
> *  Dale Erwin*

It's an old idea, and works very well if you don't need front 
and rear bearing information. For setting up new boards, no 
problem, but I've seen field diagnosis instances where pianos 
had negative front bearing and positive net, and clanged on 
the bridge pins on a hard blow. A rocker gage didn't indicate 
any problem, but the bubble gage showed it clearly.

I do have a question though. I use the above formula to set up 
initial plate height with a thread, and my deflection 
calculations, but how do you use the sticks to set bearing 
before you have strings on?

Ron N