_THE BELLOWS, TRUNKS, AND FRAME._
AFTER all our minute operations with small drills and fine wires,
calling for a light hand and patient accuracy, we have to turn to work
comparatively rough and coarse. The business of bellows-making presents
no serious difficulty, and we hope we may pass rapidly over it. We
shall have no reader who is not already familiar with the form of
organ-bellows, which consist of three main boards, namely, the middle
board, the top board or table, and the feeder, and of thin plates of
wood called ribs, the whole united together with flexible white leather
forming hinges and gussets.
The shape or form of the bellows will of course be determined by that
of the organ; they may be long and narrow, or short and wide, like the
sound-board. Their capacity, or area, will depend on the number and
character of the pipes which they have to supply with wind. A common
rule is to assign two square feet of superficial area for each stop
in the organ; but this would be in excess of the requirements of such
a small organ as that which we are making. 3 feet 6 inches by 2 feet,
giving 7 square feet of area, will be ample dimensions in our case,
and will work in conveniently with the size which we have assumed
throughout for the sound-board, namely, about 4 feet or 4 feet 6 inches
by 15 inches. In arranging your plans in the first instance, allow
room for a drop or play of the feeder of at least 10 inches, free of
all interruption from the pedal or other contrivance for blowing, for
it is upon the capacity of the feeder that you must depend for the
quantity of air supplied, the upper part of the bellows being merely a
reservoir in which the compressed air is stored away, and from which
it is distributed to the pipes as it is wanted. The reservoir may have
a rise or play of about 10 inches or a foot. Get out the three main
boards of deal or any sound stuff, leaving the middle board some inches
longer than the other two, that its ends may rest upon the frame of
the organ, or upon other supports as you may arrange. Cut out pieces,
also, to form a shallow box, say 4 inches deep, upon the middle board,
of the same size as the top board. This is called a trunk-band, and is
introduced to allow of fixing the wind-trunks which are to convey the
wind to the chest. You will want also a light frame of three-quarters
stuff, pine recommended, to carry and support the ribs of the
reservoir; the four boards of which it is made will be of the same
width as the ribs themselves, namely, about 4 or 4-1/2 inches. The ribs
are of very thin stuff, say 1/4 inch, but they must be quite sound and
free from cracks. You will want sixteen ribs (eight pairs) for
the reservoir and six for the feeder; of these last the long ones will
be of triangular form.
[Illustration: Fig. 19.]
Cut plenty of large openings in the feeder board for the admission of
the external air, and in the middle board for the transfer of that air
to the reservoir. These openings may be rectangular, say 4 inches by
1-1/2, and there may be fully six of them in each board. After cutting
them, convert them into gratings by fitting little wooden bars across
them, 1 inch apart, let in flush with the board, and planed level.
Each of these gratings will be covered with a valve or clack of stout
white leather, two thicknesses glued together, and held down along
one edge by a slip of wood and brads. These leathern valves should
play with perfect ease, and it is well to thin down the hinge-flap,
or cut it half through with a sharp penknife, that the valve may fly
open at the slightest pressure of the wind, and may not throttle or
retard its passage. It is a common plan to make these valves without
a hinge, by attaching pieces of tape to the four corners, and pinning
down the ends of the tapes to the board. The whole valve then rises
and falls. We prefer the hinge. After cutting your ribs to the proper
shapes, in which you can hardly get wrong, sort them into pairs, and
glue a long strip of stout white sheep-skin along the edges of each
pair. Stout calico or linen may be substituted for leather on the
opposite side, namely, the side which will present the inner angle,
and in which the ribs will be in close contact when folded together.
A glance at Fig. 19 will show that the upper ribs of the reservoir are
in a position the reverse of that of the lower ribs. This inversion of
the ribs represents the result of a clever invention by one Cummins,
a clockmaker. Before its introduction, the air in the reservoir had
suffered a slightly unequal compression as the top board descended, in
consequence of the closing-in on all sides of the folds of the ribs,
which diminished the space occupied by the air. Cummins's ingenious
modification at once rectified this inequality, since the upper ribs
fold outwards, and allow more room for the air, precisely in the same
proportion as the lower ribs fold inwards and diminish the space.
An unpractised ear might not, indeed, detect the slight change in
the tone of the pipes caused by bellows made in the old-fashioned
way, but let us by all means follow Cummins's plan. You will do well
first to join the inner lower edges of the upper ribs to the inner
sides of the middle frame; then their other edges to the top board
at the proper distance from its margin; then attach the upper and
outer edges of the lower ribs to the outer edges of the middle frame;
lastly, the lower edges of the lower ribs to the trunk-band. All this
must be done quickly that the glue may not grow cold; it will much
facilitate a distasteful operation to use a small sponge with warm
water, passed over the outer or smooth side of the leathern strips as
they are glued on. The main hinge of the feeder will be best made by
passing pieces of hempen rope through several pairs of holes bored
obliquely for the purpose in the feeder board and middle board, and
wedged in with pegs and glue. Fig. 20 sufficiently explains this. Two
or three layers of the stoutest leather will be glued over the line of
junction formed by this hinge. There is no reason why the hinge should
not be on one of the long sides of the feeder, instead of its narrow
end, if your arrangements for the blowing-handle or pedal render this
form of construction desirable. (You have doubtless well considered
your blowing mechanism.) The ribs of the feeder being worked in like
those of the reservoir, and all the glue dry, fix the bellows in a
fully distended position by temporary appliances, and fill up the
open corners by gusset-pieces of your best and most flexible leather.
Material will be economised and neatness consulted by preparing a
paper pattern of the gusset-pieces in advance. Those of the feeder must
be very strong, and it may be well, but it is not necessary, to put on
a second pair over the first, but not glued to them in the folding or
crumpled part. All must be perfectly tight and well glued down in every
part. A mere pin-hole will betray itself hereafter by a disagreeable
hissing.
[Illustration: Fig. 20.]
[Illustration: Fig. 21.]
We had almost forgotten to say that a valve 4 inches square, or
thereabout, must be fitted in the middle of the top board to prevent
over-blowing. This is generally made of a small board of wood, planed
truly level, and covered with two thicknesses of the pallet leather,
rubbed with whitening. It opens inwards, and is held closed by any
simple application of a stout spring made of much thicker wire
than the pallet springs. Fig. 21 suggests one of the very simplest
of arrangements. A string, fastened to the under side of this
safety-valve, and to the middle board beneath it, may be of such length
as to pull the valve open when the bellows are fully inflated; or the
valve may be pushed open from above by a wooden arm or catch attached
for the purpose to some part of the frame.
The apertures for the trunks should be cut in the trunk-band, according
to well-digested plans, before the bellows are put together, that
there may be no sawdust or chips afterwards to get under the clacks;
and it is well to give the whole interior of the bellows two coats of
glue-size before the ribs are closed in.
[Illustration: Fig. 22.]
The little contrivance _a b c d_, Fig. 22, is to ensure the
simultaneous rising of the top board and middle frame when the bellows
are in action. It may be conveniently made of hoop-iron, but oak or any
hard and strong wood will be equally good. If some such contrivance
were not introduced, the top board and upper ribs would rise first on
the working of the feeder, and the frame and lower ribs would follow
in their turn. This would cause inequality of pressure, since the top
board would not at once bear up the weight of the frame and lower ribs.
The little jointed apparatus redresses this by causing the whole of the
ribs to obey the first admission of air. A simpler form of it will be
found in Fig. 22_a_.
We are building a very small organ, but, desiring as we do to give as
much completeness to this treatise as circumstances will allow, we
here explain that in larger instruments two feeders are generally or
always introduced, unless, indeed, a "cuckoo feeder" is used, which
practically amounts to the same thing, being a long board hinged to
the under side of the middle board by a stout transverse piece in
its middle, and provided with two sets of ribs, each set filling up
the space from the middle hinge to the end of the board. This feeder
supplies wind with the upward as well as the downward stroke of the
bellows-handle, but it would not be suitable for an organ in which the
blowing is effected by the foot.
[Illustration: Fig. 22_a_.]
We may have readers who are so fortunately circumstanced as to be able
to apply water-power to their bellows. In this case two feeders should
be fitted in order to utilise both strokes of the ingenious little
machine, which consists essentially of a piston moving water-tight in
a cylinder provided with a valve which admits water alternately above
and below it. This is not the place for entering on a discussion of the
conditions essential to the due working of the water-pressure engine;
they may be studied in any modern treatise on hydro-dynamics; it is
enough for our present purpose to say that a cylinder not larger than
a common wine-bottle will give ample power for such an organ as ours,
provided that the pressure on the piston be not less than 30 lbs. to
the square inch, and that the supply-pipes be of ample size. Water, it
must be remembered, does not expand like steam when admitted into an
empty space, or rather into a space occupied only by atmospheric air;
hence large pipes, large valves, and large ports, or valve-openings,
must be provided, that the water-pressure, irresistible when properly
applied, may be thrown at once upon the point where it is wanted. But
this is by the way, and we will only add that the water machine should
be in a room or cellar below or adjoining that in which the organ
is placed, as a slight noise is inseparable from its action, and it
should act on the feeders by a wooden or iron rod brought up through
the floor. Still better if the whole apparatus, feeders, reservoir,
and all, can be down-stairs or in a neighbouring apartment, the
trunks only passing through the wall or floor. In very large modern
instruments the feeders, worked by steam or water, are commonly made to
move horizontally, in a way which will be understood if we imagine an
accordion or concertina laid upon its side. When the reservoir is fully
inflated it acts upon a valve, which reduces or cuts off the supply of
water or steam.
The trunks are rectangular wooden tubes made of half-inch pine, and
well jointed. In their course from the trunk-band to the wind-chest
right-angled mitres are permissible, for it is a mistake, though a
common one, to imagine that the wind rushes in an impetuous stream
along the trunks as it does (for instance) along a conveyancing tube
when its pallet is open. The trunks are simply connecting links between
the reservoir and wind-chest, but they must be large enough to ensure
an equality of wind-density in both wind-chest and reservoir under
all demands on the part of the player. Our trunk may be 5 inches by
2, inside measurement; or it may be 9 or 10 inches wide by only 1;
or we may make it 3 or 4 inches square, as may suit our plans. The
ends of the trunk should not be glued into the openings cut in the
trunk-band and wind-chest. The ends, reduced by half the thickness of
the wood, and brought to a shoulder, should be glued into an opening
in a small board, an inch or two larger on all sides than the area of
the trunk. Engineers would call this a "flange." This flange being
leathered, and the aperture of the trunk cut out, it may be pressed
with four or more screws against the margins of the openings with which
it is in communication, and will thus be removable at any time if the
organ is taken down or altered. The interior of wind-trunks should be
well coated with thin glue, and the exterior should be painted. Some
builders prefer to cover the exterior of their trunks with paper, and
to line the ribs of the bellows with the same material, applied with
common paste. Trunks have been made, too, of zinc, and oval in section.
The frame of the organ, whatever its form or plan, should be very
strong and solid, and should stand firmly in its place on the floor
without any tendency to vibration or unsteadiness. The pieces of which
it is composed should be of good deal, 1-1/4 inch thick, and from 3-1/2
to 4-1/2 inches wide, according to circumstances, that is to say,
according to the weights which it has to carry. The essential points
are these, namely, that the keys, or manual, shall rest upon firm
supports at the proper height above the floor; that the sound-board
shall be borne upon bearers at a sufficient height above the keys to
admit the intervening mechanism; that the bellows shall be carried on
cross pieces far enough removed from the floor to admit of the free
play of the feeder.
You will take into consideration, in designing your frame, the question
whether you will have pedals, and the still more important question
whether you will have separate pipes for them, and how they are to
be connected with the lower keys. Room must be provided for all the
apparatus involved in these arrangements, and, as in every part of
our work, so in this, we say that the reader himself must think over
carefully all contingencies, and make a preliminary drawing to scale
for his own guidance.
Enough if we lay down here the following rules:--
1. The under side of the key-board must be 25 inches from the floor,
or from the upper surface of the pedal-board.
2. The under side of the wind-chest should, if possible, be at least 15
inches above the key-board.
3. The middle board of the bellows should be fully 12 inches above the
floor, or above any trackers or other mechanism connected with pedals.
4. The front edge of the key-board should project about 1 foot in
advance of the panels closing in the lower part of the case.
5. Ample space should be secured for a large book-board by allowing
a still greater distance between this front edge of the keys and the
front edge of the sound-board above.
These are not quite all the considerations involved in designing the
frame. The draw-stops and their connection with the sliders must be
well considered, and room left for the requisite apparatus; and the
position of the bellows-handle should be determined, and the part of
the frame on which its fulcrum or centre will rest.
Fig. 23 gives, perhaps, the simplest form of frame usually adopted for
a small organ. It is made of four distinct frames, united at the angles
by screws, so that the whole can be easily taken to pieces. It must
be understood that the key-board is carried upon two cross-bearers,
leaving the under part of the tails of the keys accessible; and the
sound-board in like manner rests upon two bearers under its extreme
ends. If any longitudinal bar is introduced to assist in sustaining
the weight of the sound-board, it must be after careful consideration
of all the arrangements for the action or movements of the keys.
Similarly, the entrance of the trunk must depend on the mechanism of
the action and of the draw-stops. It is unnecessary to screw down
the sound-board to the bearers. Its own weight when loaded with the
pipes will keep it down, while a couple of dowels (short wooden pegs),
one in each bearer, fitting into sockets in the bottom board of the
wind-chest, will prevent it from moving laterally.
[Illustration: Fig. 23.]
There is another form of frame well suited to small organs, and which
we ourselves greatly approve. According to this plan, which is sketched
in Fig. 24, the bellows are enclosed in a stout low structure rising
no higher than the level of the key-board which rests upon its top. The
sound-board is carried upon cheeks screwed or otherwise attached to the
bottom board of the wind-chest either at its extreme ends or at points
nearer to its centre, according to your plans for the action and the
draw-stops. Or the cheeks may be united by a stout transverse piece or
girder, the sound-board being then kept in place by dowels only.
[Illustration: Fig. 24.]
The present writer has further modified this arrangement by
substituting a wide and shallow trunk for one of the cheeks. This trunk
is screwed by its flange to the bottom board of the wind-chest, where
the wind enters, and it is closed at the bottom, where it rests upon
the cross-bearers of the frame. A lateral aperture is cut in it an inch
or two from this lower end, and a short mitred trunk connects it with
the bellows. All this may be sufficiently understood by inspection of
Fig. 24.
_Remark._--The late eminent builder, Mr. W. Hill, we believe, exhibited
an organ at the London International Exhibition in 1851 which had
hollow framework, serving as trunks. It is evident that by making
one end of our bellows rest upon a hollow bearer we might omit the
trunk-band entirely, since this hollow bearer might be directly
connected by a mitred trunk with the hollow cheek supporting the
wind-chest. And by making one leg of the bellows-frame hollow, and
connecting it at top with a hollow cross-bearer, carrying the cheek on
which rests the wind-chest, it is plain that we supersede the separate
trunk altogether. Such plans as these may amuse some of our readers.
[Illustration: Fig. 25.]
If the feeder is worked by the foot of the player such a pedal as
that shown in Fig. 25 will be found convenient. It is made of hard
wood--oak, birch, ash, or walnut--with iron or brass hoops and
pivots, and is screwed to the floor of the room, independently of the
organ-frame. The little roller should be covered or muffled with soft
leather, and you will see that it rolls clear of the valve-holes in the
feeder. By lengthening the middle piece or shaft we may work with the
right foot, a feeder having its play on the left side; but in such a
case the whole machine will be best made of iron by a smith. He will
coat the pedal for you with india-rubber where the foot rests upon
it--a much better plan than roughening it like a rasp. The pedal, as
figured, is intended to be on the extreme right of the player, and to
be clear of a pedal-board of two octaves.
The reader will see that by reversing the positions of the arms of the
pedal it may be made to suit any little organ with a manual only. In
this case the muffled roller will traverse the feeder not crosswise,
but lengthwise.
We pointed out in a former page that the position of a bellows-blower
must be considered in your plans for the finished instrument. If he
stands close to the player on either side of him the lever will be
easily poised upon a strong pin projecting from the frame. A piece of
web or a leathern strap will be a better connection with the feeder
than any rigid bar of wood or of iron. If the organ is not placed
against a wall the position of the blower may with equal ease be
precisely reversed. The lever, however, may be arranged parallel to the
back wall by constructing your bellows in the first instance with a
view to this, the hinge of the feeder being on one of its long sides,
as we have explained in a former page. Or, with a feeder hinged as
usual at its end, the lever may still be parallel to the back wall by
acting upon an arm with a roller precisely similar to our foot-blower.
[Illustration: Fig. 26.]
Another mode of effecting this is shown in Fig. 26. _a b_ is the
handle turning on a strong pin at _a_, fixed to the back of the frame.
_c d_ is a shaft which should be of iron, but might be of hard wood,
hooped at the ends, having two arms, _e_ and _f_, projecting from it
in opposite directions. This shaft turns on stout iron pivots which
enter holes in stanchions securely fixed to the frame. These holes
will be better for being bushed with brass. _g_ is a short wooden link
connecting the handle with the arm _f_; and _h_ is a wooden rod which
connects the arm _e_ with a forked lug screwed to the feeder. All these
connections are by stout turned pins of iron or brass. It is plain
that every downstroke of the handle _a b_ will bring up the feeder. All
this is a matter of mere mechanical arrangement; the simpler you can
make it, by diminishing as much as possible the number of pivots or
turnings, the better it will be.
We conclude this chapter, and turn to the next branch of our subject,
with the assumption that the organ is thus far satisfactorily advanced.
When the new bellows are worked we assume that no hissing is heard,
and no escape of air perceived at any of the holes when a slider is
drawn, or at any part of the junctions of the trunk. We assume also
that when any pallet is opened by drawing down the ring of its wire, a
strong rush of wind will immediately follow, and will be as instantly
stopped by releasing the ring, when the pallet will close with a ready
and prompt snap. The sliders, too, must glide to and fro with perfect
smoothness and ease.
Pass over no serious fault. Remedy all defects with unwearied patience,
even if it involves a reconstruction of your work.
It is usual to paint the frame and bellows (leaving the ribs untouched,
however) with some dark priming. A dull red was formerly in vogue;
chocolate, dark brown, or a slaty black have now found favour in the
eyes of builders.