New action-parts problem

[Daniel Dover]

--- You wrote:
      Here is what happens: On fast repetition, the hammer gets stuck in
the backcheck before the jack re-sets........

Anyone else have this problem with the new NY problems. Could slight
--- end of quoted material ---

John,

I "inherited" a 1960's 'D' with the same problem when I took this job two years
ago.  I've learned that action problems like these are often like human health
problems, meaning that several factors are all contributing in combination to
an overall effect.  In this piano I found:

-The string height changes abruptly at the first treble break, dropping 3 mm at
note 54.  It dives another 3 mm across to note 88 for a total of 6mm
difference.

-The hammers are a standard factory bore, not custom-bored, creating a short
bore distance in the section where the string height is high.

-Hammers backcheck at 1" (+).  Hammer tails are standard length, could easily
be 1/8" longer.

-Hammer flange pinning was at zero friction, meaning the hammer was rebounding
off the string and pounding into the backcheck with more force than if it were
controlled by some friction.

-Rep lever friction was at zero.  Other replies have covered this, and the
relationship to rep spring strength.

I was able to almost completely eliminate the jamming hammer problem by paying
attention to pinning and spring tension.  The rest of the answer is hammer
replacement-- custom-bored with long tails-- but I'm holding on that while the
school decides if it's going to keep the piano.

Danny Dover
Dartmouth College, Hanover, NH