The moving boards of the feeders are mounted on welded steel frames
that have rubber hinges at the extreme left side of the cabinet frame.
That way the feeder bellows move more like a parallel motion than in a
plain wedge bellows, an expedient to maximize bellows air displacement
while keeping size down. - After disconnecting screw joints on
the
feeder frame shafts I can easily lift the entire bellows and crankshaft
assembly out of the cabinet for maintenance.
The feeders are below a big flat board that makes the central floor
of the cabinet. There are four (numbered) holes in that board, one for
each of the feeders. The lower two feeders are channeled up to the
floor
using 75 mm plastic tubes (numbers 3 and 4). Above the floor rests what
I consider a nice design, namely a central frame containing all the
valves
in the system, next attached drawing. On top of that frame is the
reservoir
bellows. It is just a matter of unscrewing four bolts to take out the
reservoir
and this valve frame for service.
An external fan is an additional air supply alternative. There is an
inlet and back check valve for that in the valve frame and that air
will
then enter the central compartment in the frame. From there is a
passage
up to the reservoir, central dashed hole in the drawing. This hole is
covered
by a bellows unloaded disk, connected with a string and spring to the
reservoir
lid, works as a pressure regulator.
The upper board in this picture is the reservoir bottom with the four feeder output valves. Unscrewing another four bolts you can remove the reservoir bellows and its spring mechanism to access these valves. This design is extremely easy to disassemble for experimentation and maintenance, but a weak point may be the rather extensive use of gaskets. At present these are the black stripes from closed cell neoprene foam. Work fine, but longevity can be questioned.
The springs to press down the reservoir lid used to be a bit problematic. Earlier i have used a set of harmonium compass springs for the purpose, but they are a bit tricky to balance in order to have the lid moving in parallel. Next I followed a conventional design using screw springs with extended arms, tied down with straps. Heated and shaped an old athlete's arm strengthener made from 6 mm steel wire. Now finally, a pair of leaf springs, resting at the center of the reservoir top board and with yokes at their ends. Work very well to keep the board moving in parallel. Each spring is a stack of four 1*50 mm spring steel bands of progressive length up to 500 mm, same as the length of the reservoir. Reservoir pressure is around 3 kPa (12 inWC).
This is what it looks like when in place in the organ bottom frame. The present challenge is to optimize the output valves that are linked to the reservoir top in order to regulate feeder flow. In case of low air consumption the reservoir lid will rise and keep these valves open part of the feeder 'inhalation' cycle. Then some air flows back into the feeder, which will also reduce the mechanical driving power.