Action of the Square Piano.
A. Action Frame.
B's Indicate the Cushions, or Bushing, of felt, cloth or leather.
C. Balance Rail.
D. Balance Pin. Round.
E. Mortised Cap for Balance Pin. Bushed.
F. Key.
G. Lead.
H. Back Check.
I. Bottom or Key Rocker.
J. Bottom Screws; used to regulate height of Jack.
K. Jack.
L. Jack Spring; concealed under Bottom.
M. Center Pin to Jack.
N. Hammer Rail.
O. Regulating Screw.
P. Regulating Button.
Q. Flange Rail.
R. Flange. Split.
S. Flange Rail Screw.
T. Flange Screw, to regulate jaws of flange.
U. Hammer Butt.
V. Center Pin.
W. Hammer Stem or Shank.
X. Hammer Head.
Y. Hammer Felt. Treble hammers sometimes capped with buckskin in old instruments.
Top Action of Square Piano.
1. Damper Lifter Wire.
2. Damper Lifter Buttons.
3. Damper Felt.
4. Damper Head.
5. Damper Lever.
6. Damper Leads.
7. Shade, supported by wire stanchions, on top of which are screwed shade buttons.
8. Damper Rail. Tilted by Loud Pedal Rod which raises all the dampers simultaneously.
9. Damper Flange.
10. Flange Screw.
11. Damper Lever Center Pin.
The Trap Action
consists of Pedals, Pedal Braces, Pedal Feet, Pedal Rods, Roller Boards or Elbows, Studs, Plugs, Trap Springs, Wires and Lifter Rods.
The cut is from the French action. Nearly all square pianos in use at the present time are of this type.
The hammer rail in the square, in addition to serving its purpose as a rest for the hammers, also serves the purpose of the regulating rail, as you will see the regulating screw, with its button, attached to it. This rail is stationary in the square, not moving toward the strings and shortening the stroke as it does in the upright when the soft pedal is used. The soft pedal in the square piano simply interposes a piece of felt between each hammer and its corresponding string or strings. This felt being much softer than that of the hammers, the tone is greatly subdued.
The mechanical arrangement of the dampers is very different in the square from that in the upright. The dampers are above the strings. Instead of springs to hold them against the strings, they simply rest upon them with their weight. In many old squares some of the dampers fall upon nodal points, causing defective damping or harmonic after-tones.
The stationary parts of the square action are: action frame, to which is secured the balance rail, balance pins and guide pins, hammer rail, flange rail, and damper rail. When the key is struck, the parts that move upward are: the back end of the key, bottom, jack, hammer, back check, damper wire and damper lever. The hammer falls back upon the back check immediately after striking, and remains there until the key is released, when all movable parts fall to rest position.