Grand Regulation In Detail - The Drop - part 16

34) The Drop

The modern grand action compared to the old type of action that was used for instance in the square grands show one great difference. Absent in the square grand mechanism is the repetition lever and the auxiliary features which go with it. Namely the drop screw, the repetition lever support spring, and the repetition lever height adjustment screw. The purpose of installing the repetition lever was to gain more positive and faster ability to repeat notes.

The technician who regulates this old style action has an easier job than if he were regulating a modern action, for there are fewer adjustments to make. This is especially true when regulating the escapement. He would only need to regulate the let-off screw. If he were regulating a modern “double escapement” action, he would have to regulate both the let-off and the drop.

Picture how the modern action works in the escapement process. At rest, the hammer is supported at the knuckle mostly by the balancier. As the key is depressed and the whippen rises, the balancier compresses slightly and lets the jack carry the hammer upwards.

Somewhere near the time that the hammer approaches the string, the jack tender engages at the let-off button. Eventually the jack trips out fully from under the knuckle. Likewise, the drop screw must be withholding the upward rise of the balancier as the jack trips or else the balancier would take over the thrust of the hammer and cause it to “block” upon the string. Hence the name “double escapement” action.

Most technicians have experienced “blocking” hammers, especially if it is the let-off that is faulty. Not only will the hammer “block” upon the string, but as long as the key is depressed, the hammer will stay at the string, completely dampening the sound. In the event that the drop screw is too high, the hammer will only momentarily “block” upon the string. Because the balancier is supported by a spring, the hammer will rebound from the string and the knuckle will cause the balancier to compress. In this case, some dampening has occurred, but the string will continue to speak.

Almost as critical to the performance of the action would be the maladjustment of the escapement too low. Where the drop is set correctly but the let-off is too far from the string, a loss of power and control would be evident. Removing the jack from its duty too early results in the thrust of the hammer being turned over to the balancier for the remainder of the distance. Just how far from the string the hammer lets-off too early and how strong the repetition spring is would determine how great the power loss.

In the case where the let-off is the correct distance from the string but the drop is too far, a very slight power loss could be evident. More important would be the lack of “surefootedness” as I call it that the pianist would feel. When the drop screw engages the balancier too early, again the balantier compresses, robbing some energy from the hammer’s thrust (however so small the amount, it does exist). The greater the amount that the hammer drops, the more the pianist will feel it as he plays.

 

He won’t be able to explain just what it is, rather the fact that something does not feel correct as he plays. I should probably explain that during normal playing ... 

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