Regulation is technically not “restoration” work, yet it is just as exacting, and an important step in the process of rebuilding the piano.
There are a few operations which need doing at this time. I don’t really have many pictures to offer of this process, but some thoughts on the important things to watch for.
John Tuttle has a visual offering here
Although I sorta glossed over it in the previous post, we want to ensure that the positions of the finger pushrods are regulated properly with the pneumatic hangers.
The pneumatics should be at rest (open) position, and the two leather nuts should be just snug around the hanger, but not tight.
In other words, the nuts should be holding the rods tight enough that it does not slip up or down, but not with such a grip that it actually impedes the pneumatic from closing very quickly.
The fingers should be resting firmly on the rest rail; if the nuts are set too high you will see a gap between the rest rail and bottom of the finger, which is not ideal.
If the nuts are set too low, the pneumatic may be pulled slightly up (closed) at rest, which is also not ideal. The other thing to check is the vertical alignment of the pushrods; we want them to be as plumb as possible, so that the travel is true. Although some degree of care was taken at the factory, if you see room for improvement now is a good time to do so.
With that done, it’s time to put the deck assembly into the piano, and see how it looks.
Exact positioning is pretty important here, so I reattached my secondary valve board which allows me to align to my two manifold supply blocks precisely. This way I know that my (partial) stack is sitting exactly where it will live when it is fully assembled and installed.
Why is this important?
The importance stems from the fact that we are going to do some regulation and we want it as precise as possible. The other issue to watch out for is the side-to-side alignment of the assembly. We also want the fingers of the player action to line up very well with the piano wippens, and this is the time to check and correct as necessary.
Once the fingers all line up in the horizontal plane, now we turn to the vertical plane.
The idea is that there must be a gap between the player fingers and the piano wippens, but that the gap must be quite small. The reason for this is that we want close to zero lost motion and efficiency when the striker is activated. We do need to make allowance for seasonal changes in humidity, recognizing that the gap may close when relative humidity is high. What we do not want above all is the wippens resting directly on the fingers, as this will keep the jacks from resetting and prove fatal to performance of repetitive notes.
Exactly how the fingers need to be regulated depends on the model of player action; in mine there are small capstans on each finger, which can be turned up or down. The size of the capstan is unique to this piano, I have never seen another exactly like this model, so I had to custom make my own tool for regulation! It is based on the tool for a similar larger capstan common in Asian pianos.
Once the “starting” position of all the fingers has been regulated, now we need the second regulation for the “stopping” position of the pneumatics. If you haven’t already done so, install the finger stop rail on the player action. It is important to note here that at this stage, the piano action needs to have been well regulated so that the key travel and hammer checking are all consistent and accurate. Otherwise the following regulation time is wasted.
Now, add the secondary pouch board to complete the valve chest, and with the suction supply connected to your stack assembly, activate each note in turn, and regulate each stop button so that the checking distance of each piano hammer, when actuated by its player pneumatic, is the same as the distance when hand played on the piano key.
This is one of those operations where it would be handy to have a third arm, but alas we must make due with what we have!
Once you are satisfied that the travel amount of the player action has been regulated, pull the assembly out and take it back to the bench, it’s time for a bit more testing!