misfiring jack

[Dave Nereson]

  To:  H. Pengelly, re misfiring jacks:

    I've run into quite a few pianos where the jacks won't return all
the way because the action parts just aren't heavy enough to return the
keys all the way (assuming key bushings and balance pin holes aren't too
tight, capstans are polished, action centers aren't too tight, etc.).  I
usually end up weighting the keys on these (I've never used those
springs that insert in the key button and help the key return, but I
guess that's a possibility).  If you put the weights as close as
possible to the balance pin (towards the capstan just enough to make the
key return), it doesn't affect the touch too drastically (these are
usually cheap spinets and consoles we're dealing with here, not fine
touch-weight regulation of concert grands for concert pianists).  If
possible, put the weights underneath the keys, so the capstans are still
accessible for regulating lost motion.  Sometimes this doesn't work
because the weights clunk on the keybed or keyframe.  Then you have to
put them on top, which might necessitate removing each key to adjust the
capstans, but what else can one do?  Use the springs?
    Other actions require more than the acceptable amount of lost motion
in order for the jacks to return because the shape of the hammer butt
under the butt leather is too "humped".  Sometimes shimming the hammer
rail up (decreasing blow distance) helps this, but not always.  I did
run into one action that had a sharp edge on the jacks and they would
scrape the butt leather.  I ended up removing all the wippens, rounding
the edges  of the jacks, re-graphiting (or Dag), and putting them all
back.
    Some poorly designed actions just cannot be optimally regulated
without modifications.
    Instead of the screw-on key weights, I suppose you could go to the
trouble of removing leads from the fronts of the keys, if there are any,
or drilling holes sideways thru the ends of the keys and inserting small
round weights, or if there's room, adding small weights to the back ends
of the keys that face the strings.  Any of the above will of course
change the touch-weight, but if it makes the piano playable, as opposed
to not-playable, and if the pianist isn't sensitive to the touch-weight,
what the heck?  Has anyone ever added the little round weights found in
some grand damper levers to upright wippens?
    --Dave Nereson, RPT, Denver Chapter PTG