Kranich and Bach Action pictures

[Robin Hufford]

Hello Dean,
     There is no need to change the wippens, and every reason not to,
notwithstanding suggestions  from those whose first impulse is, as
always,  to "redesign", thinking, no doubt sincerely, if new it must be
better.  .  A much better alternative would be to understand the
sophisticated system in place in this action, or other aspects of the
design system.
     What you have in the picture is the original, insofar as I know,
isotonic pedal K&B action.  Later actions, (perhaps from 1920 or so)
lack this feature.
In this action the left pedal operates a pitman which pushes up on a
short  lever attached to the wippen rail which can rotate.  The wippen
rail has a spring which opposes the action of the pedal pitman.   The
rotation of this rail causes the wippen to slide across the capstan and
also changes the angle of the wippen relative to the hammer assembly.
The result of this is a rise in the hammer line which creates the
intended result - shortening the blow distance but without introducing
lost motion. thus causing a quieter sound.
     It is often asserted that K&B used a hammer lift rail to achieve
this but this is not so.  The function described above achieves this:
the rest rail merely follows, as you can see from your picture, by
virtue of being attached to the rotating wippen rail, thus maintaining
the rest rail in a proper relationship to the hammershank even when the
isotonic pedal is depressed.   It is not what is is almost always
thought to be by misinformed technicians who regard it as just another
cheap grand hammer lifiting rail.  Yours  is the early incarnation of
this action, using brackets and attaching the rest rail as can be seen;
the later version, appearing sometime around  the beginning of the 20th
century, has no action brackets and the rest rail follows the motion of
the wippen rail through a sliding mechaniism and supports which are
attached to the hammer rail.
     Although radical changes in the thickness of the backrail cloth may
cascade into a series of adjustments which also lead to these kind of
problems, it is most likely the case that the pedal is incorrectly
adjusted with incorrect compensatory adjustments made to the hammer
line, or the wippen rail itself may be incorrectly rotated due either to
wear or ignorance.  If the rail is incorrectly rotated, whether by
maladjustment of the pedal travel, or wear of the packing and the
limiter described below,  the result, in conjunction with compensatory
adjustments made to the capstans by an uncomprehending technician will
be just what your picture shows.  The wippen heel will be too far
forward:  the wippen flange center is too low:  the hammer line is
incorrectly adjusted:  the hammershanks incorrectly rest on the
cushions:  the capstans are too low in the key and the jack/knuckle
alignment is questionable.    Take heart as these are all interconnected
in this sophisticated sytem and may be fairly easily corrected.  To do
so I would:
     1.  Look at the limiter, a kind of metal hook which restrains the
rotation of the rail against the pull of the spring.  There will be
leather or felt glued to the point of contact of the wippen rail and
limiter.  If these appear original consider the pedal throw:  possibly
somewhere the pedal is traveling to much:  remember, its function is to
rotate the rail downwards.   There is also a stop under the lever on the
bottom of the keybed.  It is easy to be fooled into thinking the problem
is merely pedal throw, which indeed it may be, or perhaps not.  There
may be, instead, an incorrect position of the limiter due to wear or
misguided adjustments of other technicians.
     2.  Rotate the rail counterclockwise (from the perspective of your
picture) and watch the heel/capstan interface.  Bring these to a point
approximately centered on each other.  At the same time observe the
angle of the jack which at present is incorrect relative to the
knuckle.  Try to find the place where the jack is as close to parallel
with the core of the knuckle while at the same time the heel/capstan
alignment becomes more centered.  Usually, this will result in the rail
being approximately horizontal.  Fix this point by either packing the
leather or felt under the limiter, or adjusting it, if possible.
     3.  Reset the hammer line while observing the effect on the
alignment of the jack/knuckle and the heel/capstan.  It may be necessary
to tweak the  rail as described above to achieve the best compromise.
Raising the hammer line changes the previious adjustment slightly so an
iterative process may be necessary here.
     4.  Adjust the hammer rail so that the hammershanks are above it as
in most grand rest rails.  The weight of the hammer assembly should be
taken by the jack and repetion lever in the normal fashion.
     5.  Now correctly adjust the pedal throw so that the hammers go
about half the blow distance to the string.  Watch to make sure the
pedal does not rotate the rail so far that escapement occurs.
     The action can then be regulated as usual.  One can see this is a
tremendously well thought out system, generally, so sophisticated that
it is misunderstood by well meaning technicians who make adjustments
which create these kinds of problems.
Regards, Robin Hufford, RPT


Dean May wrote:

>    Part 1.1.1    Type: Plain Text (text/plain)
>              Encoding: 7bit
>
>                   Name: k&b 006.jpg
>    k&b 006.jpg    Type: JPEG Image (image/jpeg)
>               Encoding: base64