34) The Drop (continued)
Regulation of the drop screw was defined in the last post as being the adjustment for regulating the point of escapement for the balancier. Today, we will discuss how to make that adjustment and some problems that may crop up when regulating the drop.
The first priority is to have already regulated the let-off. Second, make sure that the repetititon springs are strong enough to support the hammer. Trying to regulate the drop with weak repetition springs is a lost cause. When watching the amount that the hammer drops after let-off, a weak repetition spring will let the hammer drop too far, since the spring is not strong enough to support the hammer. Adjusting the drop screw up under this condition will not cause the hammer to drop any less, and will be rather frustrating. Third, make sure that there is sufficient dip to enable the action to complete its escapement cycle.
To regulate the drop, remove the action from the piano and place it on level surface. At this time, the drop screws may be either too high, too low, or just about right. Remember that the drop screws must be low enough to see the hammer let-off, so frequently they have been turned down in order to complete step no 33 The Let-off. But if the repetition springs were too weak, many times the drop screws must be turned up in order to see the hammer rise when regulating the repetition springs. So who knows where the drop screws are at this point?
Carefully depress the key of the note that you will be regulating until the hammer lets-off. Watch the amount that the hammer falls below this point of let-off. To make this judgement easier, I frequently depress the neighbouring key first and keep its hammer in a raised position while adjusting the drop. Comparing the height of the hammer being regulated with its neighbour at the point of the let-off and again after it has fallen, I can judge with great accuracy how much the hammer has dropped.
In my earlier years, I was instructed that the drop screw should be turned until the hammer drops ½ the let-off distance. I will advise that it is faster, easier, and more accurate to regulate the drop (as well as other steps) by the way it feels. The ideal is to have the drop screw engage the balancier at exactly the same time that the jack is engaged by the let-off button. This “double escapement” can be felt by a good pianist, and with a little experience, a technician can learn to feel it also. Since I prefer to regulate an action at the piano, regulating the drop to be 1/2 the let-off becomes a problem. The action must be removed from the instrument in order to turn the drop screws. With the action out of the piano, how can a technician know what the let-off distances are (remember that I taper the let-off so it varies with each note)? I don’t have space enough to carry around the complete shop, so I never have a let-off rack with me when I find a piano that needs regulating. The answer to this problem is simple; regulate the drop by feel rather than by a specific distance!
Let me go on record again about the use of let-off racks. I believe that they are a costly item which can easily be eliminated by using the piano strings themselves, which is most accurate. The time spent correctly adjusting a let-off rack to match the string height is in my opinion wasted, as well as being inaccurate.
Once the drop has been regulated, reinstall ...
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https://www.professionalpianotunerlondon.co.uk/post/grand-regulation-in-detail-the-drop-continued-part-17
