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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Grand Regulation In Detail - The Let-off continued - part 15

33) Let-off (continued)

For those technicians who find it difficult to set the let-off in the piano by watching the space between the top of the hammer compared to the thickness of the corresponding string, there is another method. Find someone in your area who sells magnetic signs such as those found on the sides of cars or trucks. The magnetic backing for these signs comes in 1/8” and 1/16” thicknesses, which are perfect for use as let-off gauges.

Purchase at least two strips of this material, one of each thickness, about one inch wide by around twelve inches long. The one inch width is sufficient to place the strips against the under sides of the strings without having to worry a lot about whether the strips will cover the hammer strike line. The twelve inch length is variable with the piano. The lengths should be no longer than the sections between the plate struts or else the strips will be too long to adhere. The larger the piano, the more sections are created by the struts, and the smaller the widths are of these sections. You may want to carry an assortment of lengths of this magnetic material.

To use, remove the action and set it aside. Take something such as a felt wedge and block up the sustaining pedal to left the dampers away from the strings. Otherwise, if there are bichord or trichord damper wedges in the area where the magnetic strips are to go, they will prevent the strips from adhering. Position the strips against the undersides of the strings, being careful to place them directly at the hammer strike line. Reinstall the action and check to see if the strips are positioned correctly. If not, carefully reposition the strip with a small tool.

Now comes the easy part. Seat yourself at a comfortable height so that you can see and work on the let-off rail. There is no need to see what is happening at the string level. Depress the keys one at a time and adjust the corresponding let-off button until a very slight resistance is felt as the hammer lets-off against the magnetic strip. When regulating in this manner it is important to remember to continuously depress the key and feel how the hammer lets-off

.

Try to get each key regulated so that exactly the same amount of resistance is felt at the point of let-off. Use the 1/8” thickness for the tenor and low treble sections, the 1/16” thickness for the top treble. After all are adjusted, remove the magnetic strips and check the point of let-off visually. This step must not be overlooked! Invariably there are slight corrections which must be made. Despite the fact that the resistance which was felt was uniform, the actual point of let-off will vary a little.

There are both pros and cons to regulating in this manner. The pros are that it is by far easier and faster to set the let-off with a magnetic strip, especially if the regulation was way off from where it should be. However, the cons are important. Obviously, these magnetic strips will not adhere to the bass strings, so approximately 1/4 to 1/3 of the let-off must still be set by eye! As was mentioned above, those which can be set with the strips must be double checked by eye for accuracy. Most importantly, the best let-off is one that is tapered uniformly from note 1 all the way up to note 88. The magnetic strips do not give a tapered let-off. Instead, they give a noticable break where the change was made between the 1/8” thickness strip to the 1/16”.

 

Despite these drawbacks, I still like to use ...

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Grand Regulation In Detail – The Let-off continued - part 14

33) Let-off (continued)

Previously discussed were the regulation steps that affect the point of let-off, namely the jack alignment to the knuckle and the raising or lowering of the whippen either through altering the key height or by turning the capstan. The amount that these changes would affect the point of let-off is marginal. It is far more important to realize that regulating the let-off affects other steps more than the other steps affect it.

The two steps which are affected by regulating the let-off are dip and drop. Remember that in this discussion dip includes aftertouch. Looking first at how let-off affects drop, let us define drop as the amount of downward movement that the hammer has after the point of let-off. Keep in mind that the regulator has to move the key downward very slowly in order to see this drop of the hammer. During normal playing, this drop as such would not be visible, as the hammer would just rebound from the string into check.

 

If a graph were drawn to show the movements of the hammer versus the slow, downward movement of the key by the technician, the amount of drop and how it is affected by the let-off becomes clear. In all of the graphs shown, the key dip is set to a specific measurement which will not be changed. In figure 1 the hammer travels upwards from the point of rest and lets-off (marked “A”) at 1/8” from the string. The hammer then drops away from the string let’s say another 1/8” (marked “B”), and then rises back up yet another 1/8” (marked “C”). This last upward movement of the hammer coincides with a small downward movement of the key which we will define as aftertouch.

Figure 2 illustrates what happens when the hammer lets-off closer to the string, all of the other regulation steps staying unaltered. The point of let-off has changed to 1/16” from the string, the drop increases to about 3/16”, and the aftertouch decreases to about 1/2” of what it was in figure 1. The aftertouch decreases because it took more key dip to raise the hammer to a higher point of let-off, and it took a fraction more dip for the hammer to drop the farther distance compared to figure 1. The pianist will complain that the piano now “plays hard” since there is insufficient aftertouch. The action also feels a bit sloppy because of the excessive drop. He might even notice that when playing very lightly the hammers have a tendency to “bubble”.

Figure 3 tells what changes happen when the let-off is too far from the string. Here the point of let-off is 3/16” from the string. The drop now decreases to about 1/16” and the aftertouch increases to about 1-1/2 times as much as in Figure 1. The aftertouch increases here for the same reasons why it decreased in Figure 2. It took less dip to raise the hammer to the point of let-off, and less dip for the hammer to drop the smaller distance. In this case the pianist will complain that the keys feel spongy, as there is too much aftertouch. I doubt that he would complain of too little drop, as he would not normally be able to feel it. The complaint may be heard of slower repetition.

As can be seen from these graphs, a change in the point of let-off can really affect another regulation step. I will explain now why it is important to know that ... 

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Grand Regulation In Detail – The Hammer Blow continued - part 13

32) The Blow (continued)

To wind up the discussion on blow, I want to describe some different methods that I know of to measure the distance accurately between the tops of the hammers at rest t­o the bottom of the strings. One easy way is to use a small pocket ruler with a sliding clip. The clip is moved to the appropriate mark on the scale, say 17/8“. The ruler is then inserted through the strings until the tip of the ruler touches the top of the hammer to be measured. The clip marking the desired blow distance is then compared to the bottom of the string. The capstan is adjusted until the clip matches this mark.

The good aspects of this method are that the tool used is already in your tool kit and can be used for many other purposes. It is also easily adjustable to provide a blow gauge for whatever blow distance is desired. This can be helpful if the blow distance wanted is measured in millimetres and does not correspond to a normal inch measurement. The drawbacks to this method are that the clip often moves while trying to measure, giving a false reading; and the ruler usually slips out from between your fingers and drops into the action. Both of these problems have forced me to look for a better idea. 

 

A number of years ago while visiting a piano factory I was given a very nice aluminium gauge Figure 1 which can be used to set a blow distance of 17/8“. This tool really caught my eye since it is very easy to use and has a good handle to grab hold of. The technician just inserts the gauge between the hammer and the strings. If the blow distance is too little, the hammer will be pushed downward by the tool. If the blow is too great, the hammer can be seen to rise when the appropriate key is pushed down. Although better than the ruler, the­­ blow gauge also has its faults. Since the measuring portion is fixed it can only be used to set a blow distance of 1 7/8”. It also happens to be too big to fit in the allotted space in my tool kit!

The best solution, as is often the case, is to make a well designed homemade tool. Take a piece of wire and bend it to look like Figure 2. The functional part marked (A) used to measure the blow distance can be made to whatever distance is desired. I made three gauges to carry in my tool kit. One is 44mm (1 3/4“), one is 46mm, the last is 48mm (1 7/8“). They are colour-coded so that I can quickly select the one wanted. Since they are homemade you can vary the length of the tool to fit your tool case or design the handle so it won’t fall from your hand.

An added plus is that by selecting different thicknesses of wire for these gauges ...

 

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