Action modification results.

[Jon Page]

In the past few months, I've had 2 Young Changs and 1 Samick come
through the shop. Great improvements have been made on all in
regards to action geometry but I didn't document until this last YC.

a. original survey
b. Reshape hammers/taper/re-arc tails
c. move knuckles out 1mm on shank to 18.5mm
d. move stack back 3mm
e. alter FW to target 38 BW

Survey of C4
    UW  DW  BW  F   SW   FW  SBR
a  32   60    46  14  10.9  32    6.4
b  26   52    39  13    9.9  32    6.3
c  24   44    34  10    9.9  32    5.8
d  22   38    30   8     9.9  32    5.4
e  30   46    38   8     9.9  24    5.4

Description:

a.  The piano was difficult to play, one reason the owner sold it,
      he wanted a lighter action and decided to go for a digital.
      BTW this also is a PianoDisc.

b.  Hammers were in the high top range. Reshape, square the tail
      to the shank, taper width 10.5mm at top 7.5mm at tail. Remove
      staple (.2g) from notes 64 and up to reduce shoulders.
      Ending at 3/4 medium range. (at #64, SW increase jump)

c.  Knuckle core aligned forwards of jack center pin. Action spread 113.5,
      no room to shorten spread because the jack was already forward of
      center on the let off button and capstan was on the rear of the cushion.
      Height of wippen rail OK. Jacks were burying into the rep stop felt even
      with 9.5mm dip and 48mm blow.  I expected a greater difference.
      [In retrospect, I might have eliminated this procedure but I didn't like
      the angle between the jack and shank at rest.  The knuckles were 
relatively
      loose in the slot so no damage was done in removal and I reused them.
      A veneer shim was glued in alongside the core upon 
reinstallation. Then the
      final survey (e) might have appeared something like this: 
30,46,38,11,9.9,29,5.9]

d.  The capstans were on the rear portion of the cushion felt and behind
      the Magic Line. The bass and tenor hammers were at odd angles on the rail
      to fit the strings.  Relocated stack back 3mm to align capstan 
on cushion center
      and Magic Line. This also improved the strike point in the 
treble although I had
      to move the keyframe forwards .75mm (predetermined before stack location).
      The bass and tenor hammers spaced to the strings with the shanks at
      more comfortable angles to the rail and wippens.

e.  Plays like a dream with minimal after touch. The FW is still high 
but without
      assist spring wippens there's not much else to do. 10mm dip, 45mm blow.
      Fortunately the hammers allowed for needle voicing which brought 
it right down.
      I think that even the PianoDisc operates better.

Due to reducing the action ratio, the letoff buttons had to be turned 
up to nearly
maximum. This probably will cause some difficulty in their adjustment once the
hammers become worn.  For the next job, I'll either remove the buttons and
remove ~3 to 4mm from the bottom or install wippens which have a wider angle
between the fly and tender; perhaps one with a screw adjust spring 
similar to the
Tokiwa M&H wippen, if not that wip with appropriate flange (preferred option).
I need to pull out the parts kit for comparisons.

The Samick came out best of all because I was able to apply a 
Stanwood TouchDesign
since it had the spring assist wippen already (no screw adjust :-( 
This needed to have
the stack moved back, knuckles moved out on the the shanks, wippen rail raised
1.5mm and spread increased to 114mm, hammer weight reduction with 
shaping/tapering/arcing.


NEXT !
-- 

Regards,

Jon Page