Optimizing repetition (revisited)

[Horace Greeley]

Jerry, et al -

Great!  I was hoping to hear from some of you Continental Types!

Anyway - comments (as usual) are interspersed:

>I feel that it is pertinent to mention that  any alteration
>of the jack position vis-a-vis let-off necessarily implies a change
>in the jack position when the key is in the rest position.
>
>Our jack regulating method here in Paris, which conforms to Hamburg
>procedures, is to regulate the jack, not in relation to the knuckle core,
>but in relation to the angle the jack forms with the hammer shank.
>This is in order  to maximize the amount of energy transferred to the hammer
>shank from the pianist's finger in the first moment of key movement.
>

This is absolutely correct.  The principle has been corrupted in most US
discourse to
the assumption that the core of the knuckle is perpendicular to the shank,
and,
therefore, provides an appropriate reference point.

>The principle is that the maximum amount of energy is transferred from
>the key to the hammer shank when the jack is perpendicular to the
>hammer shank at rest position.  If the jack is in any other position
>the maximum energy transfer either peaks after the hammer has begun to
>move (too late for maximum acceleration), or not at all (in the case where
>the jack is regulated leaning slightly towards the hammer).

Two points:  First, this intersection is another set of intersecting involuted
curves.  The farther they are from "optimal" intersection for transfer of
power
(as Jerry describes supra), the less energy is transferred to the hammer.
(Also,
the rate at which the energy is transferred is changed, but that's another
story.)
Second, as I suspect most folks who have regulated more than one or two
Hamburgs already know, even there the regulation guides machined into the top
of the balancier do not always properly provide this angle, either.

>We do our jack regulating by lifting the neighbor hammers out of the way,
>pushing the neighbor wippen gently to one side and sighting down the jack
>to look for a 90 degree angle with the hammer shank.  Striking distance
>and rep lever height have to be correct  to do this.
>
>This is, of course, a description of an ideal situation.  Dozens of
>variations in parts dimentions, rail positions,  wear, hammer boring,
>etc., can and do necessitate compromises, and it is impossible to
>ignore the jack's position in relation to the knuckle. There's always
>room for a little tinkering, but we try for the most rapid response at the
>beginning of key movement.

This is the other area which seems to be immediately noticed by (real)
pianists.
Further, this has a profound affect on the _perception_ of the relative
weight of the
action.  We first came on these problems early in the history of the notorious
Teflon era - things would move lickety-split - _after_ they started moving.

>To develop what has already been discussed about repetition from the
>bottom portion of key dip... if an action is regulated carefully and
uniformly,
>I believe that a first rate pianist can find a comfortable and rapid
repetition
>without letting the jack return completely to its rest position against the
>spoon.

This is a really important point, and one which is, I think, often
misunderstood
by technicians as well as pianists.  The problem is most manifest in an action
which is (otherwise) properly regulated, but in which the aftertouch is too
shallow.
(No, there isn't a truly viable specification for this, but, traditionally
was about
the thickness of a US Nickel for US S&S pianos and about the thickness of a
US Penny [the old-fashioned, copper kind] for Hamburgs and folks who wanted
a more "Hamburg" feel.)  In this case, (remember Alicia) the pianist does
not have
room to "catch" the knuckle because of the limit of the aftertouch.  (Jerry
says this
better - I seem to have my mouth full of haroseth.)

>The essential is the uniformity of regulation so that the pianist feels the
>minimum
>risk in letting the key rise the minimum amount.  If this amount is
uniform and
>well defined, I believe the pianist will feel relatively at ease, even if
>the piano is
>not the fastest in the world.  Clearly, no two pianos will be alike in this
>respect.
>The various comments others have offered about drop, springs, key felt, and
>lever position are all excellent and important.
>
>We've talked a lot about the top action in regard to rapid repetition, but I
>think
>it bears mentioning (even if it seems obvious) that consistent repetition
also
>depends heavily on the stability of the action.  If the action starts
bouncing
>even slightly due to poorly set glider bolts, stripped out action bracket
>screws,
>cracked rails, or if the key returns to an inconsistent position due to
deformed
>key holes or worn key bushings,  the repetition will naturally become less
>controllable and the pianist will glower.
>

To which I would add the integrity of the forefinishing work between the
case and the
keyframe.  Anymore, I take the whole mess apart and start over, rather than
leave
a question in my mind.

Thanks again, Jerry!

Best.

Horace

Horace Greeley

Stanford University
email: hgreeley@leland.stanford.edu
voice mail: 415.725.9062
LiNCS help line: 415.725.4627