Is the piano done at long last?
Ask yourself the following questions:

Does the tempo of the roll function independently of the volume?

Is the piano “easy” to play?
By easy, it is meant that the treadles offer a proper amount of resistance, and one can feel the air being pulled out of the chest with each push of feet.
It is NOT meant that there is no resistance at all, and one must pump like a maniac to play the music!

Do the control levers, buttons and expression devices all act as they should?

Does the paper of an older roll stay true on the tracker bar, even if there are some occasional rips or tearouts along the way?

Is the piano able to play large successive chords and/or arpeggios, with many notes at the same time?

In other words, does the piano feel, sound and look as it should?

If the answers are all “yes”, congratulations — you’re all done!

Now that your stack is completely assembled and thoroughly tested, let’s put get it back in the piano (do read the previous post for prior steps, if you have not already).

Carefully put the stack back in its home, without touching the hangers against the piano wippens. Slide the stack back into place and secure it with the large screws.
Install the tubes for suction supply to the motor, and the damper pedal feed, as well as any other expression devices or the shifter if necessary. Ensure that this tubing does not kink or interfere with the piano action.

Connect the mechanical linkages for the tempo indicator rod and the transmission; these need to be regulated mechanically, so that the range of motion of the control levers is optimized.

For the play/reroll lever, regulate the linkage so that when the lever is in play position, the pinion engages with the take up spool gear; it should engage positively, but not so much that it bears strongly onto the gear. When the lever is moved to the reroll position, the pinion hub should slide over enough so that a protruding pin (or other arrangement) engages the reroll sprocket so that now the motor is powering the reroll clutch shaft above.
In conjunction with the transmission, the play/reroll lever must also cleanly activate the stack cutout valve, so that when in reroll mode no suction is supplied to the stack, in order that you don’t hear the music playing backwards at high speed!
Conventionally, a player action features a governor override valve, so that when in reroll mode, the air motor receives unregulated (maximum) suction to reroll as quickly as possible.
When in play mode, this valve should be firmly closed to ensure accurate functionality of the governor, so check that this adjustment is regulated properly.

The tempo lever regulation is coordinated with the tempo valve and the indicator / pointer found at the bottom of the spoolbox (normally). When the tempo control lever is all the way to the left, the tempo is theoretically “zero”; the v-slotted tempo valve in the lower action or governor should be closed, which means that the air motor is receiving no suction and does not turn. Adjust the pointer rod so that it accordingly reads zero at the indicator. Likewise, when the lever is all the way to the right, the tempo valve should be wide open now, but just so. This should correspond to a tempo reading of 120 on the indicator. A further check is that the motor should just begin to turn when the pointer indicates a tempo of approximately 10.

With this done, now the governor itself needs regulating. The above regulation needs to be done well, for the following regulation to be effective. The spring tension of the pneumatic and knife valve need to be calibrated as follows: At a tempo of 70, seven feet of paper need to pass the line of holes in the tracker bar. You will probably need to manually measure and mark this on your test roll, as I did.

With the test roll accurately annotated, play the roll from the starting point, marking time on a stopwatch. If the 7′ mark arrives before time, it is running fast which means you need to weaken the retaining spring of the governor pneumatic. Conversely if the roll is running too slow, you need to tighten the spring. Although it may seem tedious after all the other regulation which has already been done, it is important to get this final adjustment just so, to ensure smooth and reliable playing.

It’s time for tubing — yes!
This is a sure sign that we are approaching the end of the project.
On a double valve stack, the tubing (or retubing) is effected at the end of rebuilding, when we know the valves and pneumatics all work.

This is another task which is pretty straightforward, but still needs a degree of care and planning.
It’s a question of both cosmetics and functionality.
If the tubing is stretched too tight, it may kink near the nipples or come off prematurely.
If it is too loose, it may kink on itself, or get caught in the piano action backchecks.
So, get it in the Goldilocks zone, and make it “just right” in terms of function and appearance.

The smaller size from the tracker bar to the nipple board (piano notes) and to the shifter valve box are usually size 9/64″ inner diameter. The expression and supply lines may be a larger diameter size like 3/16″, 7/32″ and so on. Measure the tubing based on the nipple fitting on which it will need to live. And note that while tracker bar tubing is generally sold in 100′ lengths, you actually need at least 140′ to complete a whole stack – ask me how I know this!

The tube or hose should be barely snug on its fitting; enough so that it will not fall off accidentally, but not tight to the extent that you have to use a lot of force to push it on. For smaller diameter tubing (e.g. tracker bar), what helps is a bit of lubricant when trying to get it in place. A liquid polymer used for piano work, will serve well for this application, or failing that, good old human spit also does the job! This makes the job easier, and also safer for the piano, as it is not so difficult to inadvertently bend or break the long and delicate nipples on the back of the tracker bar. This preventable scenario is to be avoided!

In the event that your stack still has the original lead tubing, and said tubing is still in good condition (not deteriorated or crumbling), it can continue to serve if you feel it is safe to do so. If there are problems or damage that are evident, it’s really best to replace wholesale with neoprene tubing (again, working safely with the lead), instead of trying to do extensive and uncertain repairs to the old lead tubing.

Once everything is back together, it’s time for the final bench test of the stack. Hook up your suction supply to the stack and shifter device, with a vacuum gauge for calibration. Put a music roll in the spool box and wind it down onto the takeup spool. If you have a diagnostic test roll, this is an ideal choice. Testing the notes sequentially will help identify problems quickly and accurately. Fire up the suction and manually advance the transmission gear so that the roll plays through its notes. Make sure to check which note is the first on the roll — not all test rolls play 88 notes!

As before, if all notes work well, with good actuation and repeating, at various “tempi” (feed rate of the music roll), and if the shifter device keeps the paper tracking as it is supposed to, and you can do all this at 7″ of IWC suction, you are in good shape!

Here once again is Bruce Newman demonstrating what a properly restored stack looks like on the bench.

If you haven’t done so, finish assembling the spool box and any other components, to get the stack ready for its new home in the piano.

Before putting stack back in, this is the time to address any outstanding issues with the piano. Give the piano a good tuning, and voicing, if necessary. Double check the regulation and performance of the piano action. You can also check the functionality and regulation of the pedal pneumatic at this time, since it is easier to make those adjustments now.