What's inside a pianola
Pianolas are much more complicated than what can be seen from the outside, there are hundreds of moving parts hidden inside. All the pneumatics and bellows are covered in rubberised cloth, valves and gaskets are leather and tubing is also rubber or lead. Most rubberised cloth parts have a lifespan of 30 - 40 years and the bellows need to be recovered when they are old and rotten as they leak air and pedalling gets harder until it just does not work anymore. If Pianolas have been stored in damp areas or in sheds then corrosion of metal parts becomes a problem as well.
The pianola action generally consists of a unit in the bottom of the piano which produces the vacuum called a bellow set, which has feeder bellows attached to pedals and reservoir bellows which are spring loaded,
and a top action with 88 small pneumatics (bellows) which activate the piano keys. Each of these small key pneumatics is controlled by a valve (or two in a double valve type) which is activated by a hole in the roll as it passes over the tracker bar.
There is also a system of tracking to keep the roll aligned with the holes and an air powered motor to drive the roll via a gearbox, a governor to regulate the air motor speed regardless of pedal pressure, and often other pneumatic/valve units for sustain and soft hammer rail.
Follow this link to find which brand of player mechanism is inside your pianola: Player piano makers
A full player action restoration takes between 2 to 3 weeks full time work for pedal uprights – grands and reproducing players take longer. It is a very labour intensive business as can be seen by the pictures below: