Hammers with no inner felt.

[Erwinspiano@AOL.COM]

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In a message dated 7/25/2002 9:51:23 PM Pacific Daylight Time, 
yardbird@pop.vermontel.net writes:

             Hi Bill
     I meant to comment on the "work hardening" idea you stated last week.  I 
have an idea what you refer to but as I see it all hammers soft or hard have 
some work hardening done to them as they develop string marks, compacting 
right on and barely under the strike surface. The results are quite different 
depending on the hammer.  If I understand you term or concept this is what 
this means.
   A piano hammer is an energy storage device. It absorbs energy on impact 
with the string. As it begins its contact with the string it 
deforms/Compresses the string and then re-releases its energy that was 
stored, for that split second, back   into the string. As the string is 
deformed it to releasees its stored energy imparted by the initial hammer 
blow pushing the hammer away. Basically two springs pushing on each other 
rather than a head on collision If this is somewhat clear the next part 
should fall into place
  Work hardening and the subsequent development of some kind of molecular 
change in the felt beneficial to tone is only possible if the hammer has a 
certain amount of stiffness or limited resilience to begin with. With 
unlimited resilience (too soft) the hammer no longer works as a nonlinear 
felt spring and cannot take advantage of work stiffening/hardening. It is too 
linear, unable to get progressively stiffer with increasing levels of energy 
applied, it becomes instead more of a damper. Hardeners/stiffeners (lacquers) 
must be applied to limit resilience then work hardening can apply.  
    For the overly plasticized or (petrified felt) hammer work stiffening 
happens at the immediate surface only compacting surface felt seen as the 
string grooves which cause a nasty sound we all dislike, but does nothing 
else except annoy & assault piano tuners ears. Not much musical dynamics to 
be had here.
   However for the hammer with a reasonable amounts of reselience/stiffness, 
meaning not too much needling or juicing to get close to desired piano tone, 
work hardening is something that happens not only in the string grooves but 
deeper underneath and thru out. The felt takes on a set but doesn't freeze 
up. Sometimes it shows up visually like the hammers have taken this set, 
squashed a bit on the top and out at the shoulders. I've seen this in 
Isaac,Ronsen and Stwy hammers.  Primarily though it shows itself in the tone 
which is what I your point was Bill. The tonal ripening.   Hmm I like that 
Bill
      The more the felts resilience is stolen during pressing the less likely 
work hardening has any effect or validity to its tone production qualities.

      >>>>>>>>>>Dale Erwin>>>>>>>>>>>.
> 
> It is the hammer which has not had its resilience thermoplasticized 
> out of it which, soft though it may be, is ready for 
> working-hardening. This "after-market" process really ripens the 
> resilience, and allows the tone to mature into something great.
> 
> Bill Ballard RPT
> NH Chapter, P.T.G.
> 
> "If you jabber like a jabberwocky and if you walk like a jabberwocky,
> You must be a jabberwocky"
>      ........... two punchy guys
> +++++++++++++++++++++


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