Re. Bobbling hammers on Yamaha upright

[Bill Maxim]

----- Original Message ----- 
From: "James Ellis" <claviers@nxs.net>
>The problem is too much of a hump at the very front of the butt leather,
making the jack have to move too far out before it will clear.

I ran into the same problem 30 years ago with two Yamaha P2F's at an
institution I service.  I tweaked the regulation on the offending notes with
no immediate satisfaction, but now 30 years later they are behaving.

I have now run into the same problem in a 20 year-old Renner
action/Grotrian-Steinweg studio piano.  D4 and E4 were bobbling. I got them
to stop, just barely, by tweaking the regulation.  I will not be surprised
if the condition returns.  I assumed it was due to compaction of the
buckskin/undercloth of the butt at the point where the jack pushes, leaving
less compacted buckskin/cloth to interfere with the jack as it tries to
clear the butt.  I did not remove the butts to see if this was actually the
case.  My experience has been that C4 and F4 get more wear than the notes in
between, so I have some doubt the compaction theory is correct.

I am wondering if I could adapt the "bolstering the knuckles" technique with
any success.  That should change the shape of the buckskin, with associated
re-regulation, enough to allow the jack to clear, I would guess.


Bill Maxim
Maxim Piano Service
Columbia, SC
wmaxim@sc.rr.com