32-keyless Trumpet Organ
1 Reservoir and feeders
The design is based on the traditional model, but maximum capacity in a limited space was a priority.
The two sets of double-acting feeders were mounted very close together, eliminating wasted space down the
centre. Wind entry to the top pumps is by the outside edges only, through the two slots in each side. The
bottom pump entries are underneath.
The hinge blocks were made from hard-wearing beech, and machined to the correct
angle. Small wind-boxes were constructed around them, onto which were glued the top fixed boards. Not
pictured are the two moving boards, laminated using beech for the frame and 1.5mm ply for covering. The
wind-transfer holes in the moving boards were covered with leather valve flaps before fitting the boards.
The valve leather is made by folding the leather onto itself creating a laminated piece. This prevents
the valves curling up in dry conditions which would ruin effective sealing.
A moving board secured with nylon cord and beech wedges. The hinge had been
liberally greased for smooth running. Above right:
One side of the hinge was sealed with a strip
of leather to prevent leakage from one side to the other.
Preparation of the ribbing - four sets like this were required for the
feeders plus a larger set for the reservoir. 1.5mm ply was used with cross-grain to prevent collapse
under pressure. Above right:
calico strips were glued onto the main boards for initial fitting
of the ribbing. The strips are bias-cut (45 degrees to the warp and weft) so both warp and weft
threads cross the hinge line for strength.
The ribbing is glued behind the calico strips. Note the hinge point a little
inside the edge to allow for a quirk in the final leathering. This picture shows the counter-bored hole
to take the steel crank pin. Above right:
Leathering completed - the long sides were done first
with one piece each, and the ends were then done, also with one piece each. On the left hand side can be
seen a fine gauze patch covering the bottom air entry holes to the lower feeder.
Having fitted the base strips to join the two sets of feeders together, the reservoir hinge rail
is fitted (above left)
and manifold pieces fitted and leathered (above right)
. The end
reservoir calico hinge can be seen ready for the ribbing. The opening to the right of that is the airway
from the reservoir to the outlet manifold.
The air inlet slots are covered with gauze to keep out dust, and two braces
are installed to keep the top fixed board rigid. Above right:
The steel cranks are fitted.
These and the braces were made by Bob Wallington. The length of the connecting rods are adjusted by
screwing two sections against one another. These 9mm rods are stronger than the traditional wooden rods,
and far smaller - ideal in this limited space.