shank strike weights

[Barbara Richmond]

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shank strike weightsJon,

I slept on it.  So you would put the lighter weight shanks with the =
larger knuckles on the most overweight hammers.
Do I have that right?

Barbara Richmond, RPT


  ----- Original Message -----=20
  From: Jon Page=20
  To: pianotech@ptg.org=20
  Sent: Tuesday, November 15, 2005 6:58 AM
  Subject: shank strike weights


  > What is the benefit or what <is> the noticeable difference of =
measuring
  >the knuckle, besides making the let off buttons nice and even and =
look good?


  I first started measuring knuckle and shank thickness because of what =
I would
  call a poorly installed set of knuckles and was surprised to find such =
a wide disparity. Measuring the thickness of many shanks proved to have =
negligible differences so the differences were in the exactness of =
pressing the knuckle in. I measure from the top
  of the shank to the bottom of the knuckle.
  Last year I posted about a knuckle caul press for this concern.


  Subsequent sets measured to have differences between .5 and 1 mm (.020 =
- .040")
  within the set. I maintain a window of .25 mm (.010"), that's +/- =
.005" (.125 mm) from
  the average overall shank/knuckle height. I place the bulk (average) =
of the shanks
  in the center and the +/-'s at the extremes. A more level let off =
button line was just an interesting result.


  Action geometry is affected by the size of the knuckle so anything one =
can do to
  bring uniformity benefits the action.  Priority for shank selection is =
matching shank SW
  to hammer weight with knuckle height second.


  Ultimately the best scenario, inertially speaking, would be to =
graduate the weight of the hammer heads themselves and group =
same-weight/knuckle height shanks. But most hammer sets are
  so erratic in individual weights that it takes invasive procedures to =
have them comply.


  Matching shank SW to hammer weight has proven to require minimal =
intervention for
  a smooth SW curve.


  First, I bore and taper the hammers.
  Weight them and plot them on a graph.
  Select shanks accordingly and install them on the rail. (# on =
underside next to knuckle)
  Hang hammers.
  Remove h/s/f from the rail.
  Cut the protruding shank off with a band saw and rough cut an arc.
  Set up fence to trim tails on disk sander to even length.
  Arc tails.
  Weigh SW and plot on chart
  Adjust SW
  Install h/s/f on rail.


  I sounds like a lot of work but it goes fast. I like to arc the tails =
after hanging the hammers
  to produce a nice finished edge. I also ease the edges (sides and =
bottom) of the tail molding
  to remove the sharp corners with a file.


--=20

  Regards,

  Jon Page
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