The Homemade Tromba Windchest
I built a homemade electropneumatic windchest for the 8' tromba on the great, along with the top 28 notes of the 16' principal. This project was completed in Jan-Feb of 2012. The chest holds 86 pipes and was intended to supply air to the three lowest tromba pipes by tubes. But these three pipes refused to speak on tubes, so an offset chest is being provided for those notes.
Here is the mostly completed chest with one bung board still open. The top octave of the tromba is harmonic, and those pipes are sandwiched in the middle. The top octave of the tromba uses flue pipes, which are at the right end. The 16' principal can be seen behind these and sticking up over the trombas in the middle of the chest.
Looking inside the chest, the pneumatics (white) with valves mounted on top, can be seen. Pieces of electrical conduit were used to take the air to the toehole under the pipes. The black things are the electromagnets which open a valve that exhausts the pneumatic.
This picture shows how the pneumatics were made. A spring fits between two pieces of wood, and the wood is wrapped with leather. The valve is glued onto the top.
The tromba is installed above the swell shades, close to the ceiling. This picture shows the bottom of the chest, with all the magnets, and the offset for the 3 bass pipes. This gives a persepective of their lofty perch.
A view of the trombas from the other end of the great walkboard. The great unit flute is in front of the trombas, and the main chest to the other side of the walkboard.
Here is the tiny offset chest that holds C, C# and D. The hole at the end is for the windline.
A front view of the fully installed trombas. The small pipes in the foreground are on the main great chest. The driver board for the trombas is visible under the chest.