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 4½ inches. The ribs are of very thin stuff, say ¼ 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.

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 1½, 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.

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.

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. 22a.

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.

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, 1¼ inch thick, and from 3½ to 4½ 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.

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.

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.

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.

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.

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