Purpose of the Action of the
Grand PianoThe purpose of
the piano action as a whole is to accurately translate every nuance of the
player's finger and hand movements into a musical note that reflects the exact
intentions of the player. The slightest change in the speed of the stroke, the
firmness of the stroke and even the release of the key must result in a
corresponding change in the piano's performance. The explanations here will
certainly not make you into an expert piano technician but hopefully as a player
you will have a better feel for the control of your instrument by grasping the
sheer complexity of what happens everytime you press a key down and release it.
A piano technician who can make the adjustments necessary to achieve the above
described behavior from the piano is indeed a true artisan. Please
scroll
down to view all the
explanations.
Description of Components
The
Key itself moves in a
"see-saw" type of motion as the player presses the front end. The
key coverings of modern
pianos are no longer made of Ivory due to legal restrictions on its use. Most
manufacturers now offer some variety of a man-made or synthetic ivory to provide
a touch sensation that some players feel is conducive to smoother piano
technique. Key Leads
are used to balance the key's "see-saw" motion so that just the right amount of
force is required to press the key down. Since the keys of the piano become
longer as you approach the lower notes, lower notes require more key leads than
higher notes so as to make all keys feel the same to the player. The key leads
must also be positioned very accurately since the closer they are to the front
of the key, the easier the key will depress and vice-versa. The
Key Button is made of
very sturdy wood in order to resist wear from the constant movement of the key
on the Balance Rail Pin.
The Balance Rail
is part of the key frame (not shown) and supports the
Balance Rail Bearing
which serves as the pivot point for the "see-saw" movement of the key. The
vertically adjustable Capstan Screw
does the actual pushing up of the other components of the action. The
Action Hanger is
mounted to the key frame (not shown) and supports three separate rails that each
have certain action parts attached to them as you will see below.
The
Hammer Flange serves as
the support for the hammer which pivots on a
Center Pin. The Hammer Flange is secured to the
hammer rail with a screw and is held in position by the fluted edges along the
rail. This design assures an absolutely stable pivot point for the hammer. The
Letoff Screw is screwed into the Regulating Rail and as you can see in the
animation above, blocks the bottom half of the jack (shown later) as it moves
upward so that it has to pivot out from under the knuckle (shown later).
The
Support Flange
"supports" a large number of moving parts known as the wippen assembly and is
secured to the Support Rail by screw. The three rails mentioned here and above
are sometimes made of wood, sometimes extruded aluminum, but the method used
here is hollow brass tubing with wooden doweling driven in the center. The brass
is considered more durable and has less tendency to add a metallic quality to
the piano's tone and the wooden dowel helps to provide better stability for the
screws that run through the rail as well as eleminates unwanted metallic
resonance.
While most action parts are made of
hard maple, the Hammer
itself is sometimes made from mahogany or a similar hardwood. It is attached to
a Hammer Shank
which may be cylindrical or octagonal as shown here. Underneath the hammer shank
is attached the Knuckle.
It is this Knuckle that is actually pushed up by the jack (shown later). When
the jack slips from underneath the Knuckle, the hammer is said to "escape" as it
surges upward suddenly and strikes the string. The
Hammer Felt, the
covering over the hammer, must be of exact hardness and shape to produce the
best possible tone when striking the string.
The Wippen Assembly
is the most complex part of a piano action and is responsible for the most
precise and sensitive control of the motion of the Hammer to and from the
string. Both the Balancier
and the Jack are
responsible for the actual pushing of the Hammer toward the string. The black
areas visible above are the carbon coating on the Balancier and Jack in the
areas where they push against the Knuckle (shown above). The Hammer "escapes"
from the Jack or from the Balancier depending on how the key is moved. Basically
if the key is moved from a full stroke the jack does the pushing but if the key
is moved from a lower position as in fast or very soft repetition, the balancier
does the pushing. This dual pushing of the hammer is called
"Double Escapement" and is the single most important
innovation in piano action design. The
Repetition Spring keeps the balancier in position to
be able to perform the above described repetition while the
Repetition Felt Block
is what the Jack rests against when the Balancier takes over to perform
repetition. The Hammer Rest
provides a soft landing place for the hammer after it has performed a
particularly forceful blow and bounces back all the way down. The
Spoon is simply a stop
against which the Fly Regulating Screw
adjusts the at rest position of the Jack directly against the Knuckle (shown
above). The Balancier Covering
provides cushioning if the Balancier moves all the way up against the Hammer
Flange (shown above) and the Support
Cushion provides the curved surface against which the
Capstan Screw (shown above) actually pushes up on the entire Wippen Assembly.
The Center Pin
shown here is the one on which the entire Wippen Assembly pivots as it moves the
Hammer.
