32-keyless Trumpet Organ
the 69 pipes in this organ were made by myself. Shown here is the smallest
of the main melody bourdon pipes - top "C" (transposed up 3 notes = D# -
MIDI 75). A 50-pence coin is shown for size comparison (approx. 27mm
across). The pipe body is 109mm long and the cross-section is approx. 17mm
square. Its internal cross-section (the important bit) is a mere 8mm
square. The stopper is shown before fitting. Allowance had been made for
its leather plug, shown by the coin. At the other end of the pipe (out of
view) is the foot, made as a separate piece on an engineer's lathe - a
wood-turning lathe would not be accurate enough.
Pipe scaling was accomplished using my scale chart on an Excel
spreadsheet. I programmed the original many years ago on a Casio pocket
computer, now donated to the National Computer Museum in Bletchley. The
scale progression from the largest to the smallest pipe is approximately
half-size every 16 notes for the width and half-size every 12 notes for
length. Every pipe has unique dimensions (paired for the two ranks of
Here, I will show how a rank of pipes is made, using pictures of the
smallest rank in the organ - the mixture quint (actual pitch A# to A# - MIDI
82-94). Above left: Small planks of suitable timber are
quarter-sawn. Pine is used for backs and sides, maple for fronts. The blocks
are laminated from pine with a thin layer of maple at the front - wood
forming the wind-way must be something hard to minimize erosion from dusty
air being blown through. Above right: The planks are cut down to
relevant dimensions for the pipes, with final planing allowance. The narrow
ones on the left are the sides, the long wide ones on the right are the
backs, and the short wide ones are the fronts. The small pieces at top left
are the blocks - the tiny pieces with them are for spacing the open end of
the pipes, to be sawn off later.
Above left: The sides are glued either side of the blocks, planed
at front and back and flue slots chiselled into the blocks. Above
right: The backs are glued into position, and upper lips are
chiselled onto the fronts.
Above left: Now the fronts are glued into position leaving
pre-arranged spaces that will become the mouth "cut-ups". You can see the
extra length of the blocks below the mouths. This area will be turned to a
conical shape to produce integral feet. Some historical organ restorations
have revealed this kind of construction, so I decided to try it on these
tiny pipes. Above right: This is the make-shift tool for turning
the feet. It is a small block of maple with a foot-taper bored into it. One
corner of the block was cut away to allow a chisel to be clamped into
position. This contraption was mounted into the lathe tailstock, and the
pipes were fitted into a four-jaw chuck, and rotated by hand (power and
drive disconnected). It was time-consuming but successful.
Above left: This shows the pipe feet turned parallel. Just visible
are the centre points used for stabilizing the pipes at the tailstock end of
the lathe. Above right: One of the pipes after use of the taper
tool. At the bottom of the picture is the pipe's cap, showing the flue cut
into it in the English style. All the flue pipes in the organ have these
"English" caps. Mechanical organs usually have their flues cut into the
blocks, but if cut too deep they are impossible to reduce. With this style,
reduction is as simple as planing off a little from the surface of the cap,
or even making another cap - much better than making another pipe.
The bass pipes, shown here, were mitred to fit under the organ's floor.
They are always best in that position so the case plays its part in
enhancing their resonance. These are the largest pipes in the organ, the
longest being 23 inches (583mm), there was not room enough for them to be
left straight, but in any case, their wind supply coming through a
vertical transfer board running across the front of the case dictated
where the pipes' mouths needed to be.
The mitring process, done after voicing, is simple using a mitre saw
fitted with a thin blade, so not much length is lost. The only tricky part
is where a mitre could interfere with the stopper; the "C" pipe was close!
"business" end of a reed pipe. Fitted into the block with a semi-circuler
wedge is the shallot - a brass tube open for its length about one-fifth of
its circumference, and fitted with an angled tip. Shallot-making is a
skilled job, and I leave it to the firm of W
P Williams & Co, who have made all my
shallots (to my own specification) over the years. Across the gap is
fitted a brass tongue which is very slightly curved at the open end. The
curve is hand-formed, itself an extremely skilled job, especially
considering all the pipes in a rank must have the same tone quality and
power. The slightest mis-curve or kink would completely spoil the result.
I have always produced my own tongues, for mechanical and church organs.
A bronze spring is pressed against the tongue limiting its free length.
When wind is applied to the space around this assembly (encased by a
"boot") the tongue vibrates in sympathy with its free length and the air
column contained inside the resonator (not shown). Tuning is achieved by
moving the spring to shorten or lengthen the tongue's vibrating length.
Above left: The trumpet rank in bare wood. The largest four are
made from noticeably inferior timber, but that matters much less with reeds
as the resonators only serve to amplify the sound and stabilize the pitch.
If knots in the wood are beginning to separate they could be in danger of
falling out in time. In that case a patch of thin leather can be glued over
them on the inside. Above right: The trumpets, now finished. The
boots (plastic tube covered with brown paper) are fitted to the resonators
with tapered wood "feet" similar to the feet made for flue pipes. The boots,
in turn, are fitted with shaped wood tubes for wind entry. Six of the pipes
get their wind from the top of the distribution board, and the other three
get it from the front. The tops of the boots are sealed with leather patches
to contain the wind and dampen any internal resonance which could spoil the
speech. At the bottom can be seen captive nuts used with bolts for
supporting the resonators at the open ends. The pipes speak through the
opening at the bottom the façade, with their tone quality strongly
influenced by the space below the organ's floor. This tone is augmented by a
rank of "helpers" mounted between the bass pipes under the floor, speaking
an octave higher than the reeds.
© 2017, John Page