Grand Regulation In Detail - The Drop continued - part 17

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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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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Grand Regulation In Detail - Setting The Hammer Blow - part 12

We left off talking about the two factors that create the striking point for a hammer. Assuming that the hammer glue joint is 90 degrees on the shank, which it must be, these two factors are: 1) The distance from the hammershank centre pin to the centre of the hammer molding, and 2) The position of the hole in the hammer molding, more commonly called the hammer bore distance. In measuring factor number one, the measurement is always taken from the centre of the centre pin, to eliminate any error because of larger centre pins.

Looking at the diagram, this distance for factor number one is labeled (L). In this particular instance, (L) = 5 1/8“, which is a common measurement. (L) determines the type of arc that the hammer will take on its upward movement towards the string. The distance that the hammer travels in this arc is labeled (S). (S) is correctly termed the hammer travel distance. Note that this is different from (6) the hammer blow distance. These two words should not be used interchangeably.

As the hammer is moved in or out on the shank, this distance (S) changes. Minute alterations of (L) by the technician as he glues on a set of new hammers is acceptable in order to achieve the correct striking point. However, keep in mind that the piano was designed with a specific distance for (S). The work that the knuckle does in raising the hammer is in a ratio which is dependent upon (L) and the placement of the knuckle. The closer that these two placements are to what was designed, the better the action will perform.

Of greater importance than factor no1 is factor no2, the hammer bore distance. I regularly find good make grand pianos where the bore distance is wrong from the factory! When manufacturer installs the hammers, he should measure the distance (A) on the diagram. This is the distance between the bottom of the string and the centre of the centre pin on the hammershank. Unfortunately, many pianos are manufactured without regard to this measurement. (A) does fluctuate a little from what the piano was designed to be, mostly because of differences in the thicknesses of the plate castings. Sometimes the string height varies because of improperly installed agraffes, or in the case of a rebuilt piano, the string heights will vary because the plate was lowered in order to achieve proper downbearings.

When rebuilding, always wait until the new strings are installed before sending off for new hammers. Never buy stock hammers. Insist that the hammers be bored to match the piano. Either send to the hammer duplicator the measurements for (A) for each section of the action, or else bore your own. Anyone who has regulated many actions will have noticed that the string heights vary not only between similar pianos of the same make and model, but will also vary between the different sections of one instrument. Ever wonder why the hammer rest rail never fits the bass hammershanks like it does the tenor? One cause can be improper hammer boring. Why? Most grands are made with the hammers bored at a stock distance, to supposedly fit all of the pianos made of that model(s). No interest is paid to what (A) is, or whether (A) is the same for each given section of the action.

Why is this so important? 

 

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Grand Regulation In Detail - part 11

32) The Blow

Step no12 was adjusting the key height and leveling all 88 keys. Last month we discussed step no31, regulating the jack height. These are the only steps that directly affect the blow distance, or hammer line. Indirectly the repetition springs will also affect the hammer line if the springs are weak. However, we had to make sure the springs were strong enough to support the hammers before the jack height was set. Therefore, we should now be ready to set the hammer blow distance.

Once set, there should be no need in doubling back to readjust this distance. Remember that before all of the jack heights were set, a number of sample keys were regulated for jack height, blow, let-off, drop, and then the regulation was proven to be correct with proper after-touch. I always use the end keys in each section as my samples. First, this allows for any irregularities in the string height going from section to section. Second, it gives me a hammer at the end of each section which has been set to the correct blow distance. Doing step no32 The Blow then becomes a simple matter of drawing a line between the tops of these two end hammers and setting the remaining hammers in each section level to this line.

This, of course, is accomplished by raising or lowering the capstans. If the hammers do not return consistently back to the same height when a test blow is given to the keys, check for weak repetition springs, too much lost motion in the jack height, tight hammershank flange centres, or tight key bushings. Any time that the capstan is changed, it is a good rule to give the key a test blow to see where the hammer will settle in its height. During this test, watch the rebound of the hammer as it comes up off the hammer rest rail/felt. All 88 hammers should rebound with the same freedom. If they do not, stop and check for nonuniformity in the centres, as this will make the action play unevenly no matter how well the action was regulated.

When all of the hammers in each section have been made level to the samples, install the action back into the piano and play each note vigorously. At no time should any one hammer be higher or lower than its neighbours in a section. Any unevenness should be corrected. Incidentally, the practice of raising one hammer to give the proper after- touch to that one key is wrong. In order to have perfect evenness of touch, uniformity of tone (i.e. power), and a uniform repetition, all hammers must be the same distance from the strings. More will be said on this subject at a later time.

In selecting the proper blow distance, look at the tangent relationship between the jack and the knuckle. Ideally, the knuckle should be glued on at 90° to the hammershank, and the jack should be in a straight line with the knuckle core. This would give the ideal of a jack at 90° to the hammershank. The shank should be about a shanks height off the rest felt. If it is a great deal more above the rest felt, make sure that this angle between the jack and shank is checked. An angle of more than 90° will result in a loss of power. What we want is the maximum acceleration of the hammer without destroying this tangent relationship. As has been mentioned before, altering the blow distance or altering the key dip are the only two steps which can be changed to compensate for action wear. Never set the blow distance without also considering the dip. If it is unacceptable to change the dip, and if this tangent relationship of the jack to shank has to be compromised, perhaps you should think in terms of installing a new set of hammers/shanks/flanges.

 

In the past, I have stated that ...

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