New Bearing guges that don't lie

[Erwinspiano at aol.com]

John Hartman gave me this idea a few years ago &  I'm just getting around to 
using it adn making it practical.  The more I  thought  about it the more I 
realized it's  value. 


 I've made some very simple wooden jigs which  act like rocker gauges.Just 
some straight maple.  The front foot , a  couple inches long & 12mm wide  sits 
on a unison.  There is  a slot cut out over the bridge to clear the pins when 
it rocks back so  rear foot touches the rear rest.  The bottom of the gauge 
simply  simulates the straight string line. The bottom edge of the front  foot & 
rear foot is on the same string line. Is this clear?  See  pictures,  it's 
sooo simple.


     The beauty of it is that it rocks  right at the front bridge pin fulcrum 
where the front &rear sine  angle  intersects & the rear string rest. The 
only two bearing  angle reference points that matter are these 2.  The front 
where the pin  & string intersect & is bedded firmly to the bridge & the other  
side of the bridge where the string touches down at it's final resting  place.  
Forget bridge slope & cant, iI don't think it  matters.

  The rear foot rocks down till it hits the  aliquot. It clearly & definitely 
gives you a visual,tactile picture  & physical distance gap at the rear 
aliquot indicating positive bearing(or  not) which is absolutely the truth & can be 
measured with a feeler  gauge.  I believe it's possible, since I know what my 
approx new board  squash is that I can extrapolate the precise residual 
bearing  angle for  each note & can graph the graduated bearing settings for the 
entire  bridge. I've yet to work thru this process conlpetely but the 
possibility's are  potentially very useful.
  For example.  The obvious ones just stated but also in giving  a client a 
visual idea about bearing in a piano they are considering buying or  
rebuilding. Warranty applications.
  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 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
 


   


 
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