The inside must also have strips of linen on the joints, which you will be able to rub down with a strip of wood inserted through the corner holes where the gussets will be put on. When you have attached all the folds to the feeder and feeder-board, and well rubbed down all the leather, to make it adhere perfectly all over, let it dry thoroughly. Open the feeder to its full width, and cut a paper pattern of the gussets; cut them out in leather, and, after paring all the edges with a sharp knife, glue the gussets on, and rub them down well. A small triangular gusset-piece will be required for each corner where the valve-boards are hinged; and if brass hinges are used, a strip of leather must be glued all along the joint, to make it perfectly air-tight. When all this is done, clean off the leather with a sponge dipped in hot water; cover all the woodwork of the feeders with coloured or ornamental paper, and they will look very neat.
Make the two wind-trunks of thin wood, 6 1/2 in. high, and slightly larger internally than the wind-holes.
The reservoir is merely a rectangular bellows, with each fold 2 1/2 in. wide. Cut the ends of each fold to an angle of 40°, the same as the ends of the feeders. The bottom board of the bellows will be 5/8 or3/4 in. thick, and a safety-valve must be made in it in the position shown in Fig. 198. This may be about 2 1/2 in. square, and covered by a valve of thin wood, lined with soft leather (soft side outwards), one end of which overhangs about 1 in., and is glued down to form a hinge. The valve is kept closed by a spring fastened through a little staple on the valve. A peg of wood, about 2 1/2 in. high, is fixed in the feeder-board immediately under the valve; so that as the bellows descends, the peg presses the valve open, and allows a little wind to escape, thus preventing undue pressure on the reservoir. A spiral spring is fixed to the centre of the under side of the reservoir, and to the top of the feeder-board. This spring exerts a constant pressure on the reservoir, and gives the force of wind necessary to cause the reeds to sound.
The foot-boards may be made of 1-in. deal, hinged on the under side of the front edge to the foundation-board already mentioned, and connected from the top by a cord to the lever arm, which is fixed into an axle working on centres in 2 uprights placed at the front and back of the inside of the case. Another arm extends from the other side of this axle immediately under the centre of the feeder, to which it is connected by a short lug. The general view will sufficiently explain this, the axle there being shown in section only. The foot-boards should have a ledge of 3/4-in. stuff on the front edge, and they may be covered with a piece of carpet to make them look neat.
The reservoir having been completed, should now be fastened with glue to the reservoir-board, which has previously been referred to. This board lies on the top of the 2 wind-trunks, which should have a strip of leather run all round the top edges to make all air-tight.
The holes in the reservoir-board over the wind-trunks must be covered with leather valves to open upwards, made in a similar manner to those in the feeders. These valves are to prevent the return of the wind after it has been pumped into the wind-chest. A small hole, 4 in. long and 1 in. wide, is cut in the centre of the reservoir-board, to let the wind into the reservoir. If this is covered with a wooden valve lined with leather, so that it may be closed by pulling out a stop knob, you will have the stop termed "expression"; but if you do not wish for this stop - which is rather difficult to manage, and causes the breakage of many reeds by over-blowing - you will not require any valve over the hole, but may, if you like, make it rather smaller, and cut 2 more holes, 1 on each side of the central one, and about equidistant from that and the ends of the reservoir, as shown in Fig. 200.
To form the wind-chest, take some 1/2-in. pine, 3/4 in. wide, and glue it all round the top of the reservoir-board fair with edge of it at the sides, but 2 in. in from the ends, and plane it level all round, thus forming a shallow box 3/4 in. deep. Now to see if your bellows answer, lay a strip of leather all round the edge of the wind-chest, screw a 1/2-in. board tightly down on it, and glue some paper all round the joints to prevent any escape of air; when dry, fit it into the case, placing a couple of long wedges under the cheeks to hold the reservoir-board firmly, and a screw or two through each end of the bellows board into the ledges. Press the foot-boards gently and fill the reservoir (do not overdo it), and then if your bellows is sound, and the valves act all right, the reservoir will take some minutes to empty itself. This board is only used to test the bellows, and does not form a part of the instrument. It is utterly impossible to make the bellows entirely without leakage.
The pan or sound-board next claims attention. Take the beech plank before referred to, which is to be 2 ft. 7 in. long, 6 in. wide, 1 1/2 in. thick at the bass end, and tapering off to 3/8 in. thick at the treble end. Plane this very truly on both sides, for it must not be touched with the plane after the subsequent operations. Take the width of the row of keys - which will be about 2 ft. 5 1/4 in. - and mark it on the sound-board, leaving 1 in. at the bass end and 3/4 in. at the treble end; divide the 2 ft. 5 1/4 in. into 54 equal parts, and the lines thus made will be the centres of the mortices, which are set out as follows: - At a distance of 1 1/2 in. from the back edge of the board, draw a straight line all along it; at the bass end, set off 1 1/2 in. from that line on the first of the cross marks; at the treble end, set off J in. on the last cross mark, and join it by a sloping line to the bottom of the 1 1/2 in. line, you will thus get the lengths of all the mortices. Then mark the widths of the mortices, which should be 1/4 in. at the bass and diminishing to 1/8 in. at the treble.