misfiring jack

[Farrell]

I had this situation arise on a 12 year old Kimball two days ago. The keys
were front heavy so you never saw any lost motion. If you pushed the key
down in back, the wippen would fall and the jack would go under the butt. I
removed the action and removed the wippen from the worst offending note. The
flange center was almost froze solid. WAY over ten grams friction. Repinned
that one and the ten or so others that were not always firing and problem
solved. Apparently, the wippen weight was enough to drop the wippen and
reset the jack, but with the little up-pressure from the keys, the slow
wippen/flange center prevented the wippen from returning all the way and the
jack from resetting.

Repin worst ones, lube the rest, action works great..........at least in
this case..........for now...........I think..........hope it lasts!

Terry Farrell
Piano Tuning & Service
Tampa, Florida
mfarrel2@tampabay.rr.com

----- Original Message -----
From: "Dave Nereson" <dnereson@dimensional.com>
To: <pianotech@ptg.org>
Sent: Friday, December 08, 2000 3:04 AM
Subject: Re: misfiring jack


>   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
>
>
>