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.