hammer crowns tearing apart (was Dolge)

[A440A@aol.com]

Barbara writes: 

Didn't Ed Foote advise needling the shoulders first on these hammers to
avoid the crown splitting?
Ed, do I have that right?
<< >     If the tone is too bright after the filing, then any voicing with
> needles near the strike point (even if it's not right ON the strike point)
> makes the crown spread apart even more.  It's very frustrating and I'm not
> sure how to handle this problem.
 
Yes,  I did. Yamaha hammers have so much compression in them, that if one 
needles a lot on the top, the outer grain of the felt on the hammer gets torn by 
the compression below as the felt expands.   I have found that by introducing 
resilience into the crown by relieving tension lower on the shoulder, I 
maintain the integrity of the fibers over the strike point while still allowing the 
hammer to soften underneath.  I also use a small steel hammer to move the felt 
around in between each voicing step.  I hit them pretty hard, too. By 
spreading the needle work over a large area, away from the crown,  there is no 
localized weakness in the outer surface to allow tearing.  Once the low shoulders 
are softened, then I move upwards with the accupuncture.    
   I follow my ears in this procedure, using a needle long enough to reach 
the underfelt in the area between 8:00 and 10:00 and 4:00 and 2:00 until the 
distortion in sound on a FFF blow is gone.  As soon as this point is reached, I 
like to stop and let the piano get played some.  I think it allows the felt's 
compression to relax and stabilize.  The tone on softer playing will rarely be 
changed by this low, deep needling, but it is common for brilliance to 
increase a day or two later.  I ascribe this effect to the hammer becoming more 
active in its rebound . 
    When I return, I can usually effect most of what I want with several 
slightly shorter needles up around 11:00 and 1:00 . This pass is directed by what 
I am hearing in the p-F range.  At this time, I would like to hear a 
predictable increase in brilliance between the two levels.  This is the "palette" that 
the majority of playing is occuring in.  
   After these two treatements, ideally several days and hours of playing 
apart,  I can go back through and even out the response with usually a single 
deep needle up high on the shoulders.  I want all the hammers to increase in 
brilliance evenly, (though that NEVER happens perfectly).   Sometimes, I, in 
response to a "crunch" spot in the hammer, will run a needle straight down into the 
crown, between the string grooves.  Sometimes, I take a voicing tool with 
four 3 mm needles in it and pound the hammer from 9:00 to 3:00, right over the 
top.  This is when I want a velvetly ppp and can't get it any other way.   
  It is not uncommon for these hammers to "grow" a couple of mm with heavy, 
low shoulder needling.  The finest voicing takes a couple of days to show 
itself, since the felt doesn't react and equalize all at once.  However,  I really 
think it takes a deep and broad coverage needling to get the whole hammer 
working together to produce the greatest range of tone, located between the 
particular perfomers limits of strength and subjective desire for the tone. 
Regards,   
 
Ed Foote RPT 
http://www.uk-piano.org/edfoote/index.html
www.uk-piano.org/edfoote/well_tempered_piano.html