_THE DRAW-STOPS._
WE have provided no means as yet for bringing the sliders under the
control of the player. The mechanism by which this will be effected
must depend upon our plans for the case and book-board.
_Method 1._--As we have only five stops we may have resolved to arrange
the knobs in a horizontal row above the key-board, and below the edge
of the book. We shall soon see that this arrangement will result in
much convenience and simplicity.
The ends of the sliders project at each end 2 or 3 inches beyond the
margin of the sound-board. To the cheek of the wind-chest, below these
projecting ends, will be screwed a stout balk of oak or mahogany (say
2-1/2 inches square), constituting a bridge, and having stout levers,
after the manner of backfalls, working in notches. These levers should
be of oak, birch, or other hard wood, at least 1/2 or 5/8 inch in
thickness, and not less than 2 inches wide; and the pins on which they
work should be very stout, say 1/4 inch in diameter, and should be
held down in their places by slips of hard wood firmly screwed down
to the bridge. All this is sufficiently shown in Fig. 46, and it will
be quite plain to the comprehension of every reader that these levers
(like backfalls) may be askew to the straight line of the bridge, so
that while their upper ends spread out to reach the sliders, their
lower extremities may be brought into any position convenient of access.
[Illustration: Fig. 46.]
The arms of these levers will of course be of unequal lengths. About
2 inches, or a trifle more, will be found a sufficient and agreeable
play for the draw-stops. If the sliders have a play of 1 inch only, it
is clear that the lower arm of the levers must be twice the length of
the upper arm. At any rate the adjustment of the play of the draw-stops
to that of the sliders should be made in fitting these levers, and not
in any other part of the mechanism. The upper end of the lever, shaped
into a tenon or tongue, will enter a square aperture in the end of the
slider, and the edges of this aperture should be bevelled, in order
that the lever may bear equally upon it in all positions. Rub the end
of the lever with blacklead, and use this wherever there is friction of
wood against wood.
The levers being fitted, three at one end and two at the other, or
all the five at the same end, as may best suit the position of the
wind-trunk, the form of the frame, and other considerations, it will
be easy to connect them with the draw-stops by means of squares or
bell-cranks.
[Illustration: Fig. 47.]
Fig. 47 shows these squares or bell-cranks arranged upon a board which
is screwed upon the key-frame. They may be cut out of sheet iron or
may be made of oak, the arms halved together or joined by tenon and
mortice. They should work upon a strong pin of iron or brass, and a
small block underneath each square lifts it above the level of the
board. A trace, or light rod of pine, 1 inch or 7/8 square, notched at
one end to receive the arm of the crank, and at the other to catch the
end of the lever, is connected with each by a pin of iron or brass, and
blacklead is used as before.
The draw-stops are generally turned and polished for a few inches at
the end which appears in sight, and which carries the knob, and it is
usual to line the holes through which this turned and polished part
protrudes with scarlet or other cloth. The tails of these draw-bars,
left square, should work in guides cut in a vertical piece at the back,
or otherwise arranged to ensure parallel movement. A short slip of hard
wood or of metal connects each draw-bar with its bell-crank. The action
of this mechanism must not be considered satisfactory unless each stop
operates with ease and exactness, and without any sense of elasticity
or unequal resistance.
The knobs will be easily fashioned, from a good pattern, by any turner
possessing a light lathe; nor is it difficult to engrave the names on
the ivory faces. A convenient tool for this latter purpose may be made
by grinding down the end of a small triangular file. But the engraver's
"burin" may be bought at the tool-shops. The knobs will not be glued
into the ends of the draw-bars until all is complete, that the engraved
titles may be rightly adjusted at a true level.
_Method 2._--If it is preferred to place the draw-stops to the right
and left of the player, as in large organs, we shall have the bridges
and levers as before. The draw-bars will run through guides at the
back, fixed to some part of the frame, and their polished ends will
be brought through lined holes in the cheeks of the case, fitted
according to taste. The connection of these horizontal draw-bars with
the vertical levers will be effected by squares or bell-cranks of a
form known as "trundles." We give a representation of one of these
in Fig. 48, where _a_ is the slider, _b_ the lever acting upon it,
_c_ the trace connecting it with _d_, an arm of the trundle _e f_.
This trundle should be of oak, birch, or other hard wood; it has pins
at each end, which are received into holes bored in bearers arranged
accordingly, and not shown in the figure, or in the frame itself of the
organ. (It is well to char these holes.) The trundles are of course
placed parallel to each other in a row, and the second arm of each
trundle will be inserted at the level answering to the position of the
draw-bar. In the cut _g h_ is this second arm and draw-bar.
[Illustration: Fig. 48.]
The trundles are easily made of iron, and with manifest increase of
strength and neatness. We have used gas-pipe for this purpose, 1/2
inch in external diameter. The arms made from iron slips, 1/2 inch
wide and 1/4 thick, were brought to a round pin at one end in the
lathe. This round pin passes through a hole drilled through the trundle
(whether tubular or solid), fitting it tightly, and the projecting
end is spread out with a riveting hammer. All this may be done cold,
but still more effectually with the aid of a forge. The ends of the
trundle will be received in charred holes in bearers as before, using
tallow as a lubricator; or if tube is adopted, brass or iron pins may
be jammed into the ends of the tube, and trued up in the lathe. All
such iron-work, introduced here or elsewhere in the organ, may be
painted over with the composition known as "Brunswick black varnish,"
which will prevent rust. The holes in the arms, to receive the pins of
the traces and draw-bars, will be drilled with ease in the ever-handy
lathe, or with a bow and breast-plate, or by any blacksmith.
[Illustration: Fig. 49.]
_Method 3._--In small organs, with short sound-boards, the iron
trundles may be made to act at once upon the sliders, without the
intervention of the levers and bridge. When this is done the upper arm
of the trundle will be quite at its top, and will be sloped or bent
upwards as shown in Fig. 49. Near its end will be a short and strong
pin, which will enter a little slot or oblong hole in the slider. The
trundle will revolve in a wooden collar screwed to the cheek of the
wind-chest, and at its base in a hole in a bearer or in the organ-frame
as before. The draw-bar will act directly upon the lower arm of the
trundle, and the lengths of the two arms must be proportioned to each
other, so as to compensate for the difference between the play of the
slider and that of the draw-stop.
Cases of peculiar construction may be easily imagined, in which two
sets of trundles may become necessary, communicating with each other
by long traces. In some other cases the trundles may be horizontally
placed, like a roller-frame, and common squares may act upon the
sliders; with upright traces connecting them with the arms of the
horizontal trundles; while combinations of these various plans will
suggest themselves to the inventive reader to meet possible exigencies
of position or arrangement.
_Method 4._--We may still further explain that trundles may be
discarded by fixing common squares or bell-cranks upon steps or stages
cut on the edge of a piece of thick plank, screwed to the organ-frame,
the steps or stages corresponding to the levels of the draw-stops as
arranged in the cheeks or jambs of the organ. The draw-bars will act
directly on these squares, which will transmit the movement to the
levers by traces; but in this case it is plain that the levers will
be of varying lengths, and must be provided with separate bridges, in
order that the proper relation may be maintained between the play of
the several parts. This plan has much to recommend it.
We have entered at some length into the subject of the draw-stop
action, because much of the comfort of the player depends upon its
efficiency. The arrangement to be adopted should be well considered,
and the plans for it matured at an early stage of the work. All the
pins used should fit accurately, and it is well that means should be
taken to prevent the dropping or working out of these pins. A very
neat way of guarding against this common accident is to reduce a small
portion of the end of the pin with a file or in the lathe, and to cut
a screw-thread upon this reduced portion; a leather button will then
render failure impossible. The other end of the pin is usually bent
down at a right angle.
Composition pedals, for drawing and shutting off the stops in groups by
the foot, are not wanted in so small an organ as ours, and we need not
describe them.