Fig. 98.
206. The Base, B, is 6 × 4 × ⅞ in. The magnet, M, is explained in [App. 89]. Its wires are attached to the binding-posts like [App. 46]. The armature, A, is 2½ × ¾ × ⅛ in., and made as described in [App. 71]. The piece, D, is 2½ × 1⅜ × ½ in., and is screwed to B from below, after the two uprights, C, are nailed to it. The uprights, C, are 2¾ × ⅞ × ½ in. They are nailed to D. The nail, N, runs through both uprights, and acts as the bearing for F to rock up and down upon. The hole for N is 2 in. above B. It must not be too loose in the holes, or F will rock sidewise, and allow A to touch one of the magnets. The upright, E, is 2¾ × ¾ × ¾ in., and is screwed or nailed to B from below. A screw, G, is put into the side of E near the top. This screw has the underside of the head filed flat, and against this the screw, L, taps when the armature is attracted. The arm, F, which carries the armature, A, is 4½ × ½ × ½ in., and is pivoted by means of N, which passes through it and the uprights C. F must swing up and down freely. The hole for N, in this model, is 1¾ in. from the armature end.
207. The armature is fastened to F by a screw, S. A copper bur is put under the head of S to aid in keeping A from rocking sidewise. Through F, and about half way between C and L, is put a screw, I, the lower end of which taps against the head of a screw, H, which is put into D. By unscrewing H a little, F will be raised, and A will be brought nearer the poles of M. The rubber-band, J, is placed over the head of I, and has tied to it a thread, O, which in turn is tied to a screw-eye, K. K screws into the end of B, and by turning it one way or the other, the tension, or pull, on J may be increased or diminished. There must be enough spring in J to pull A up after the current ceases; it must not pull so much that the magnet cannot draw A down hard enough to make a good click between L and G.
The Magnet, M, is explained in [App. 89], and the construction of one bolt magnet is given in detail in [App. 88]. In this particular sounder the bolts are 2 in. long under the heads, thus bringing the tops of the bolt-heads about 2¼ in. above B. M is held to the base by a band of tin, T. The yoke may be screwed to B, as suggested in [App. 90]. This is the better plan.
208. Adjustment. You will find, although you make all of the parts with the dimensions given, that you will have to try, and change, and adjust before everything will work perfectly. A must not be allowed to touch the poles of M when it is pulled down, on account of the residual magnetism, which would keep it pulled down. Adjust this with F. The armature must not be pulled too far up from the poles of M by the tension in J; adjust this with I and H. If your battery is weak, the pull of J must be small, just enough to raise A.
The Battery. It is supposed, if you make an instrument like this, that you expect to use it for a line. In that case make a regular gravity battery like the cell of [App. 9]. See Fig. 99 for line connections, and Fig. 98 for plan view of this sounder.
209. Telegraph Line; Connections. Fig. 99 shows the complete connections for our telegraph line, with two complete outfits. The capital letters are used on the right side, R, and small letters are on the left side, L. The batteries, B, b, are like [App. 9]. The keys, K, k, are like [App. 119]. The sounders, S, s, are like [App. 121] or [122].