Grand Regulation – part XXIII

Step 37 – The Repetition String Strength 

Next step on the 50-point checklist is number 37, adjusting the repetition spring strength. What we want is to have the springs adjusted as strong as possible, without the pianist feeling it work at the key. This allows the repetition lever to support the knuckle after the hammer is released from the backcheck,.and enables the jack to return to its rest position as fast as possible. Note that during the actual playing of the piano action, the hammer does not rise in order to let the jack get back to its position.

This is just the way that we think it happens, since that is the way we see it while regulating the repetition spring strength. What really happens is that the whippen drops, while the balancier supports the knuckle, leaving room for the jack to get back to its rest position. Step 36 just previously performed was regulating the backcheck distance. Other than a very minor effect that the jack height has on the repetition spring, the backcheck distance is the only thing which affects the regulation of the repetition springs. This is why the backchecks and the repetition springs are always regulated as a pair, and in that order. A special note should be made, however, concerning the drop screw. If for some reason the drop screw is adjusted too far down, there will appear to be no rise in the hammer while checking for the correct repetition spring tension. The repetition spring will still do its job, but no rise will be seen. The balancier can not raise since the drop screw inhibits that rise. If this phenomenon occurs while regulating, simply raise the drop screw a little.

It is interesting that the repetition spring affects the drop as well as the drop affecting the repetition springs. If the strength of the springs is too weak ...


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Grand Regulation - part XXII

Step 36 - The Backcheck  Distance (continued)

Last month we talked about roughing in the hammer tails and regulating the backcheck bevel. Now we’ll get to the real meat of the subject and cover how to regulate the backcheck distance, along with some pitfalls to watch out for. Going back to the band regulation chart, we see that the key height and key dip directly affect the backcheck distance. An argument can be made that the escapement also affects the backchecking in that if the escapement if set so high that the hammer blocks upon the string, it interferes with the checking. That argument aside, just the key height and dip need be considered.

This seems reasonable since the backchecks are connected to the back of the keys. The keys act as a lever, and certainly changes in the height of the lever at the center, or the amount that the lever goes down at the front will change what happens at the back of the lever. The key height should at this point be correct, as it was regulated as step 12 in the 50-point checklist. However, the key dip may or may not have been regulated for the final time, depending upon the sequence used in section IV The Touch part of the checklist. The sequence used here lists the dip as step 35, the step performed just prior to the backcheck distance. So in this order, we can safely set the backcheck distance without worrying about something changing it as other steps are performed. Keep in mind that the backcheck distance may vary slightly, if the key dip is altered, so if the dip is regulated after the backchecks, some touching up of the checking distance may be needed. This only takes a few minutes, and really is not that hard to do. As was mentioned before, use your fingers when bending the backcheck wires, to insure that the wires bend at the bottom, keeping the bevel the same.

Again looking at the grand regulation chart we see that the backchecks affect only one other step, that being the repetition spring strength. This is sort of stretching the facts if we say that the backcheck distance actually affect the repetition springs. What happens, is that...

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Grand Regulation – part XXI

Step 36 - The Backcheck  Distance

I would first like to review some of the concepts previously stated before we discuss step 36 of the 50-point checklist. The seven main steps in part IV The Touch section of the checklist can vary as to the order in which they are performed. Six of these seven steps are always regulated in pairs, forming four groups:

I.              Jack height / blow  distance

II.            Let-off / drop

III.           Backcheck distance / repetition spring strength

IV.          Aftertouch

The 50-point checklist gives only one sequence that these four groups can make. That order is

I., II., IV. & III. This particular sequence eliminates having to reregulate the backchecks after setting the dip. However, it is only usable if the repetition springs are strong enough to support the hammers. If they are not, then the sequence should be...

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