A damper arm is an action mechanism found in Wurlitzer pianos. It is responsible for lifting the damper felt away from the reed when it is struck by the hammer. This causes the reed to sustain. When the key is released, the damper arm falls down and the damper felt mutes the reed. It also keeps unplayed notes muted, minimising harmonics and potential feedback from the electronics. Each note in a Wurlitzer piano has a damper arm.
Function:
The damper arm plays a crucial role in the correct functioning of the Wurlitzer piano action. As a key is pressed the rear of the whip assembly is lowered. In turn this lowers the damper regulating screw, which pulls on the rear end of the damper arm through the damper grommet. Pivoting through the damper flange found approximately 3/4 towards the rear of the arm, this raises the front end of the arm. This in turn lifts the damper felt away from reed allowing it to sustain.
When the key is released, all the above processes happen in reverse. To ensure a quick dampening of the reed, a damper spring is situated on the underside of the damper arm. When the damper arm is raised the spring is under tension; and when released the spring will press the damper arm into the reed. The spring allows firm contact between the damper felt and reed when the action is in rest position.
Servicing:
Correct regulation of the damper mechanism is crucial for the dampers to work correctly. If the damper spring is broken or the damper screw is too low, then sustaining of notes can happen when the key is not pressed.
Lubrication of the damper grommet and the damper flange bushings can aid in reducing friction and preventing slow and sluggish damper arms. Protek is the recommended lubricant for almost all metal-to-felt piano parts.
On 200 series pianos, the top five notes have a reduced damper arm without a damper felt on it. This post has more information regarding this.
