New Bearing Gauges that don't lie

[Erwinspiano at aol.com]

Hi David
  I can see how this dial gauge will give you a very close reading on  a new 
fully crowned board.  The  problem I experience  with this type of gauge or 
the Lowell gauge is that more often than not on  old boards the crown has sunk 
some or a lot & the bevel on the bridge top  comes into play.  Meaning that the 
rear bridge pins pull the string down  below the actual true rear string 
angle. (This may show more bearing than  is actually there). The  rear string 
length in these  cases runs up hill to the string rest reducing the overall 
bearing angle.  So the closer the placement of the rear foot of either gauge to the 
bridge  the more bearing reading discrepancies you will have.  See what I'm 
getting  at? 
 
  With he wooden gauges I posted about last week it is also critical  that 
the speaking length foot be butted up against the front bridge pins when it  
rocks  or big false readings will occur  as well. See what  I'm mean?
  When its' all said & done it seems there are least 3  types of usage for 
both gauges. 
 1. Assessing any bearing in an old board & using the information  to set it 
up while stringing   2. A quick reference in advising  clients as to the 
condition of there piano or one that is being considered for  purchase.
  3. Confirming your bearing in a newly bellied & strung  piano.
  Sheldon Smith & I often mused about that in reality  that the  strings need 
to be off an old board to really get an  accurate & truthful idea of crown & 
bearing as they are so usually  minimal.
   Dale

This is  the method I prefer for a quick check of down bearing.  It's  a
modified dial gauge and the three feet are 1 inch apart.  When set  on a
level surface the needle points straight down to 6:00.  Each  increment on
the gauge is .001".  So when set over the bridge with the  center foot
centered on the bridge and the outer feet on the front and back  scale, it
gives a very quick reading of the total bearing (sine(1o) =  .018.  The photo
shows about 1 degree of residual bearing.   

Of course, it's relatively useless for setting up bearing on an  unstrung
board but so is any other gauge.  My latest foray is to use  my rib scale
spreadsheet for calculating the amount of total deflection  under load and
predetermine the bridge height based on calculations (I just  hate cutting
those stupid little slots and pulling strings around).  I  still use a string
and a square to determine whether the bridge top is  square and canted
properly front to back when I do the dry fitting.   My final adjustments come
from using an adjustable plate perimeter mounting  system.  

David  Love
davidlovepianos at comcast.net
www.davidlovepianos.com





Dale  Erwin--Piano Restorations
Modesto, Ca.
Shop 209-577-8397
cell  209-985-0990
Web site _http://www.Erwinspiano.com_ (http://www.erwinspiano.com/)  
Restoration & Sales of
Steinway & Sons plus  other fine pianos.
Custom made soundboards by  design
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