Anatomy of a WurliTzer Theatre Pipe Organ
The top plate screws to the top board of the regulator and contols the movement of the valves.
The large tapered valve goes through the hole in the regulator body and seals around the top surface
of the largest diameter section.
Vertically through the main valve are 5 small holes. The small valve, with its felt and leather
seal, at the bottom covers these holes. A spring around the rod through the main valve pushes the
small valve away from the main valve to open the small holes.
When the pressure is very low the whole valve assemble is pushed down which opens largest possible
opening through the regulator to let in as much air as possible as quickly as possible. As the pressure
and the regulator top begin to rise the tapered section of the valve increasingly restricts the size
of the opening and the flow of the air. When the pressure nears the set level the main valve pulls
up against the seat on the regulator body closing off the large hole completely and leaving the
five holes through the valve body open until the regulator top rises a little more to compress
the spring and pull the small valve up against the main body of the valve as the system settles
gently into its equilibrium state.
In theory with a perfectly sealed system the valves will close completely and no air will flow
into the regulator until some air is drawn off when the preset system in the console is activated,
or whatever the regulator is supplying. In reality no air system in any organ can ever be totally
sealed so the small valve will always be very slightly open to comensate for the losses. If the
system was 100% sealed the valves would never be able to seal perfectly at the desired pressure
so the regulator pressure would rise slowly until air was draw off. A slight amount of leakage
in the system is not only ineviatable it is necessary for the system to operate properly. All
attempts should be made to minimise the leaks but in the unlikely event that you do get too
close to perfect you will actually cause more problems than you are solving.