Re Aftertouch

[Kenneth Sloane]

                      Subject:                              Time:  9:38 PM
  OFFICE MEMO         Re Aftertouch                         Date:  8/28/95

--------------ORIGINAL POST---------------

Ken, your response about Steinway switching the knuckle geometry, yes I
realize they changed in '84, I thought the higher leverage shank would yield
less dip needed... so I have to rethink this.

So if differences in shanks don't account for the difference between NY and
Hamburg recommended dip, is the .42 because of key ratio variation?  (And
therefore will change again as soon as they complete the "2 to 1" program to
preset key ratio prior to strike point?)  Is that why Hamburgs come out with
better projection on Stanwood's charts, primarily?  key ratio producing more
efficient strike ratios?

Audrey Karabinus,   Seattle

-------------------REPLY------------------

It occurred to me that some people may be confused about differentiating
between high and low leverage components. Given two notes with identical key
travel, one note can be said to have higher leverage than another note if its
hammer moves less than the other. The higher leverage action, therefore,
requires more dip. Think of the crow bar as an example with its fulcrum very
close to the object being moved and the other end much farther away. The
crowbar in my shop has a ratio of mechanical advantage of roughly 7:1 with the
end of the lever for your hand roughly 7 times farther from the fulcrum than
the end for prying. If I move something by exerting pressure on the very end
of the lever, my hand moves roughly 7 times as much as the object I am prying.

Now if I move my hand half way down the lever towards the fulcrum, it takes
only half the hand movement to move an object the same distance as when my
hand was at the end of the lever, but it takes twice as much energy. And
though a crowbar might sound like a crude example to use for the piano action,
the same rules of mechanical advantage apply to the action.

One way to understand, more easily, how a change in dimension will affect
leverage is to try and visualize what would happen if the change were taken to
the extreme. For example, what would happen if you moved a knuckle so far from
the action center of a shank that it was just behind the hammer? To do this
properly, we must also assume that the action is modified to allow the jack to
be positioned under the knuckle. Since the jack top and knuckle would then be
so close to the hammer with a change such as this, the hammer would move about
the same distance as the jack top (about 1/4 to 5/16" in most actions).
Obviously, then, moving the knuckle farther away from the action center
results in less hammer travel per unit of key travel.

But to get back to Audrey's questions, different style shanks can account for
different dip requirements. The pre '84 Steinways with the low leverage shank
(knuckle closer to action center), could almost always be set up with 3/8"
(.375) dip. In fact, couple this with an action that has a capstan line
farther away from the balance rail than the capstan line that a 2:1 ratio
would dictate (let's say, for example, the action had a 1.87:1 key ratio) and
you've got yet another lever in the piano that's going to force you to
regulate with less key travel or else have too much aftertouch. Most Steinways
I have measured have key ratios less than 2:1, and though this forces you to
"cut back" on dip (especially if the pre '84 shanks are used), remember what
happened when you lowered the leverage on the crowbar. You could move an
object with less hand movement, but it got a lot harder to push.

So, in conclusion, the Hamburg Steinway with its high leverage shank and fixed
2:1 key ratio will probably be more consistent on Stanwood's charts or any
other charts for that matter. Hammer weight, hammer hardness, friction, key
lead quantity, key lead position, and voicing are certainly other factors to
consider.

And on the other side of the Atlantic, the pre '84 and post '84 American
Steinways certainly have different characteristics one from the other, the
different shank dimensions associated with each group being very critical to
the "feel" of the pianos in each group. However, the fluctuating key ratio
inherent in American Steinways certainly can contribute to the "uniqueness"
each piano has, no matter what group it's in.

Ken Sloane, Oberlin Conservatory