[pianotech] X-Ratcheting Counter Bearing Shim

George F Emerson pianoguru at cox.net
Sun Apr 11 20:40:22 MDT 2010


Nice work, Ron N and David L.

I recently had a case where a piano had been "rebuilt."  The problem was 
that the old phenolic resin panel, under the understring felt was reused, 
with new felt glued to it.  Re-rebuilding it made no sense.  It had new 
strings and tuning pins.  The pins were tight enough in the block.  Bridges 
and soundboard were fine.  It was just a problem of the strings becoming 
imbedded in the felt and grooves in the old underlying phenolic panel, 
producing so much friction that the string would not render.  It was 
impossible to tune with any stability.  Normally, I would not reuse the old 
strings once they were removed, but in this case the strings were not all 
that old and were "pre-stretched."  I removed the strings in the tenor 
section from the tuning pins, replaced the understring felt and phenolic 
panel with a brass half-round and softer, narrower understring felt on both 
sides or the brass counterbearing, and replaced the original strings on 
their tuning pins.  It was a lot of work, but not as much as restringing the 
tenor section, and dealing with the instability of new strings amid the 
older more stable strings.  I was surprised that the old strings exhibited 
as much instability as they did, but certainly not as much as new strings 
would have.

I must confess that I have reused the phenolic resin panel with new felt 
glued on top.  After this experience ... never again!  It's a bad system to 
begin with.  You need a counterbearing to relieve the potentially severe 
friction.

Frank Emerson 



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