Stack Reassembly + Head Shelf Installation + Regulation

Once the stack has been thoroughly tested and you are satisfied, it’s time to install the top shelf and the other peripherals as well.

The items that live on the top shelf include the spoolbox (which is commonly integrated with the shelf), the shifter (tracking) device, the air motor, and sometimes some other small valve boxes which serve as signal boosters (as is the case with mine).

The “head” consists of a shelf (horizontal piece in line with the yellow arrow above word “transmission”) and the various components attached thereupon

Assuming that your shifter and other valve boxes have been tested, and that your motor has been tested and regulated already, these things can be mounted on the shelf.
If you haven’t already done this, you can check out my earlier post on the shifter here, and my post about the air motor here

This is also a good time to tidy up any outstanding cosmetic issues, should there be any. I am thinking specifically of hardware and switches around the spool box area, as once the shelf is fully loaded these are harder to get at. I noticed that I had neglected to replace an old cloth washer on the spring loaded idler chuck for the music roll, so I went ahead and disassembled that completely and gave it a bit of spit and polish. I did not replate any of my hardware, but for the round and oval head screw heads, I did clean and polish them, to match the transmission which had received the same treatment. It was a more uniform look!

final polish and replacement of cloth washer in the roll idler chuck

We’ll look at the transmission in more detail shortly, but for now, reinstall it in its home, make sure everything is lubricated and free, in terms of the bearings and so forth. Different rebuilders use different products, including motor oil, sewing machine oil, 3-in-1 oil. I chose Mystery Marvel Oil. Whatever you use, only put it where you need it, and remember: “less is more”! Paradoxically, too much lubricant can spread to the upper brake drum; making the drum sticky over time and causing excess drag on the music roll!

Regulating the position of the take up spool and the clutch, as well as other transmission adjustments

Now, the spool box itself has to be regulated too, oh yes. First we align the take up spool to the tracker bar, so that it is centered in position (use the shifter/tracker holes as a reference). On my piano there is a lock nut on the right side of the gear shaft, in the transmission, to fix the location. With that done, now we set up the music roll idler (left) and clutch (right) shafts.
What is required here is that when a music roll is placed, and the paper drawn down and wound onto the take up spool, three things need to be in alignment:

  • The shifter (tracking) device, in neutral (center) position
  • The clutch (reroll) shaft centered on the tracking cam
  • The paper roll centered above the tracker bar, just as the take up spool is centered below

I have noticed that although the width of the paper on most piano rolls is 11 1/4″, there is variation in the thickness of the spool ends, which changes the precise location of where the roll sits over the tracker bar. This in turn will change the position to which the shifter defaults, when the piano begins to play. There is a bit of fiddling involved to achieve a happy medium between rolls of different brands.

Also note that all bearing points of the shifter linkage must be free, to respond smartly to the slightest signal of misalignment from the designated tracker bar holes. This is important!

Brakes: most transmissions have two brakes; one brake for play mode (which bears on the upper clutch/reroll shaft), and another for reroll mode (which bears on the lower gear/drive shaft).
Current convention dictates that the play brake should be regulated so that it presses just lightly enough to keep the paper from flying around loosely.
Most contemporary rebuilders are of the position that the reroll brake should be disengaged completely, so that older or original rolls have less of a tendency to rip or break when being rewound at high speed. Use your own judgement!

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