Now we come to a rather important unit called the governor.
The unit in my piano actually comprises a governor, accelerator, tempo control, and reroll bypass…here’s what it looks like!

(These are the “before” pictures)

So what’s a governor? What does it do?

A governor is essentially a pairing of a spring-loaded pneumatic and a knife valve. Its purpose is to regulate suction flow to the motor, so that the motor turns evenly at a given tempo.
Because the action of a person pumping the pedals is not always perfectly smooth, there needs to be a way to compensate for this roughness and the governor’s job to do so. Like other aspects of the player action it utilizes a simple yet elegant design. The flow is routed through the knife valve, which is open a certain amount (let’s say halfway, for the purposes of this explanation) under normal pumping.
If the pumper slacks off, slightly (too much slacking will make the music stop!), the governor compensates by sensing the flow pressure differential inside the unit, and opens the valve to allow more access to the main trunk, where there is extra suction stored in the reservoir.
If the pumper gets excited and starts pumping extra hard, again the differential is sensed and the suction pulls the pneumatic (and the valve) more closed, so that it doesn’t make the motor rush.
This all happens behind the scenes with no direct intervention from the user, it’s all automatic.
Without the governor, the motor (and therefore the playback of the music) would be completely at the mercy of the pumping technique of the user. In many cases, this would mean a bad performance!

The tempo control is commonly paired with (or in close proximity to) the governor. Every pianola has a tempo control lever, which is adjusted by the user. The lever is connected to a slide valve in the unit, which moves in a linear way over an inline port to the motor.
Essentially, when you move the lever to a higher tempo, you are opening the valve to let more suction reach the motor. When the lever is moved downtempo, the valve gets closer to closing, effectively choking the motor and slowing the music.

The accelerator is very much the same idea as the tempo, except in my piano it is meant to be used in “real time”, as opposed to the tempo control which is supposed to be set at the beginning of the roll. The accelerator is also spring loaded to default to a neutral position; whether you press the lever to “accel” or “ritard”, it will spring back upon relase.

Finally, there is a bypass valve, for reroll. When the roll finishes, the “play” lever is flipped to “reroll”, and a couple of things happen as a consequence. Firstly, the direction of the transmission is reversed, so that the roll rewinds. In addition, the suction to the stack is cut off, so that no notes are triggered upon reroll. We wouldn’t want to hear the music playing backwards!
The rotary valve is switched off (this valve is pictured back in the pedal pneumatic post); the signal to the pedal pneumatic is cut off, so that the damper lift is not triggered constantly as the roll rewinds.
Finally, the bypass valve in the governor unit is opened, so that the motor gets maximum suction and operates at full speed on rewind. Otherwise, it would take as long to rewind a roll as it would to listen to the song – and unacceptably long delay!

Even though the construction of the unit is fairly straightforward, it’s important not to overlook anything and to get it all right.
Make sure the knife valve is still mated well, and lubricate with graphite. Recover the slide valves if necessary, and lubricate those too (lightly). Recover the pneumatic and make sure it’s tight, before remounting on the unit. Ensure the various port channels and compartments are sealed, so that there is no inadvertent leakage when the valves are closed.

There really isn’t an obvious way (to my knowledge) of testing the governor’s function independently, outside the piano. So you won’t know what you’ve got until everything is back in place and connected up… but, if you have done diligent work, you should be fine!

And we’re back! Now that the head is done I am moving on to the peripherals. These are defined as any stand-alone components not directly attached to the main trunk or the stack. In my case this means the pedal pneumatic, the governor, the loud/soft button control box, and the theme/ cutout boxes. These last items are technically attached to the lower trunk, but they still have to be rebuilt and verified separately.

Let’s start with the pedal pneumatic. It’s got a couple of different features from previous components, like two inside valves (secondary), and a double pneumatic.

The input to the pedal pneumatic is tubed to a manifold rotary valve underneath the keybed, which connects back to the tracker bar input, the pedal button control. Both of these inputs are shut off when the rotary valve closes during the “reroll” or rewind stage, when the user toggles the switch.

The suction supply is a larger input, because this pneumatic has to generate a fairly large degree of force, and do it quickly, in order to lift all the dampers. The top of the pneumatic is connected to the pedal prop rod via a fulcrum lever. When the pedal input receives atmosphere input, it sends a cascading signal to the pneumatic to close, which in turn raises the dampers.

See diagram from old Standard literature:

Now for the rebuilding. As before, remove old soft materials (unless you can salvage pouches, as in my case), then do your cleaning and sealing.

I will do a post on inside valves separately, that’s a specific topic which covers a fair bit of theory.

The double pneumatic needs a slightly different approach, when recovering. Instead of one pivot point a double pneumatic has two, so the cloth must be first put on one outer edge to the middle edge, then to the other outer edge. Not rocket surgery, really.

The double pneumatic is also double hinged, for strength, as well as spring loaded. You will save a fair amount of trouble if you make an index for your spring holes in the hinge end of the boards. It can just be a piece of acetate or whatever, a “map” to know where to puncture through the cloth, once the hinge end is recovered.

So once the regasketing and recovering is done, I still need to get these two inside valves sorted to complete the unit; until then I will just set it aside and move onto the next peripheral.