Grand Regulation – part XVII


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 feelrather 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 the action and check the drop visually against the strings. I usually wait and perform this check while regulating the aftertouch, since the way I adjust the dip is to watch very carefully how much the hammer rises after the drop. More will be said on this during the discussion of step no 35 The Aftertouch. Another good check to insure that the drop was regulated uniformly is to depress a group of keys and let the hammers go into check. Slightly release the keys until the hammers rise, as in regulating the repetition springs. All of the hammers in the raised position should be level to each other. If not, the drop screws were not regulated uniformly, since in the raised position all of the balanciers were blocked in their upward movement by the bottom of the drop screws.
There are two types of drop screws which are commonly found. One being a “female” style which accepts a small screwdriver, the other is a “male” style which is turned with a special tool from the supply houses. The “female” style which I will call the Steinway type is usually plated and causes very few problems. Just make sure that a proper size screwdriver blade is used.
After backing one of these frozen drop screws without a head out by hand and installing a new one, you quickly realize that you don’t want to do this often! To free up frozen drop screws I either “zap” them or put a drop of WD40 right on the heads and wait for the lubricant to soak into the wood. Note that I did not say spray WD40 all over the whole action! Take WD40 in the liquid form and with a dropper put one drop on each screw. Be especially careful to keep WD40 away from the action centres and buckskin.
Sometimes the hammers drop too far but the drop screws have already been turned up as far as they can go. With few exceptions, this is prima facie evidence that the action is very worn and needs to be rebuilt, starting with a new set of hammers. If new hammers have just been installed and this problem crops up, it means that the new hammers were not bored correctly to fit the piano.
Another problem which arises all too frequently is where the tops of the drop screws rub on the bottom of the pinblock. One cause is that the pinblock is delaminating. If so, you might even have to dismantle the plate in order to remove the action! In cases where the pinblock is OK but just was installed too low for the drop screws to clear, you have two options. One, replace the pinblock and make sure the new one leaves enough tolerance for the action to clear. Two, replace the felt or leather on top of the balantiers  which is engaged by the bottom of the drop screws with thinner material. I use a high grade of thin keybushing cloth for this repair. In order to regulate the drop correctly, the drop screws will have to be turned down from where they were, hopefully giving enough tolerance to clear the pinblock.
One last problem which frequently occurs on some new grands. The felt on top of the balancier was glued too far forward. Instead of fitting into the contour of the bottom of the flange so that the drop screw is the only thing which comes into contact with this felt, the felt first makes contact with the flat surface of the flange, causing premature escapement of the balancier. Looking at the hammer, it seems like the drop screw is turned down too far. But raising the drop screw does nothing to lessen the amount that the hammer falls, since the. balancier never gets up high enough to contact the drop screw. The solution is to reglue the felt back a little on the balancier, or else just trim off the forward portion that sticks out too far.
This entry was posted in Uncategorized. Bookmark the permalink. Both comments and trackbacks are currently closed.
  • Contact Numbers

    Mobile: 07946 597885

  • Address

    266 Westbourne Park Rd
    London
    W11 1EJ
    United Kingdom

  • Other Locations

    124 Colindale Avenue - NW9 5HP
    375 Edgware Road - W2 1BS
    44 Nether Street - N12 7NG
    97 Iverson Road - NW6 2QY
    453 Archway Road - N6 4HT
    1009 Finchley Road - NW11 7HB

  • Map


    Find a Piano Tuner in your area