262. Wood-work. The base is 7 × 5 × ⅞ in. The uprights, U, are 3½ × 1 × ¾ in. They are screwed or nailed to the base from below, their 1-in. sides being towards you in Fig. 119. They are 4¼ in. apart, inside, in this model. The piece, A, is 2½ × ⅞ × ⅝ in., and is cut away on the underside to straddle the yoke. Fig. 118 is a suggestion as to its shape. A is screwed or nailed to B.
263. Tin-work. The horizontal arm, T, is made of 3 thicknesses, and holds the shaft in a vertical position. T is 6¼ × ¾. In its ends are slots, and in its center is a hole so that the ¼ in. shaft can revolve easily, but not too loosely. The slots allow an adjustment, the screws, S, holding T to U. The shaft rests in a dent made in a piece of tin which is tacked to A. The yokes are elsewhere described.
Fig. 119.
264. Field-Magnets. In this model they were made of 5⁄16 bolts, 2 in. long, placed 2 in. apart center to center. The washers are 1⅛ in. apart inside. ([See App. 88] for full directions.) [App. 89] and [71] should be studied. Except in size, they are made as in [App. 144]. They have 8 layers of No. 24 or 25 wire.
265. The Armature, Fig. 121, on this style of motor consists of a regular horseshoe electro-magnet, made in the same general way as the field-magnets. The electro-magnets, 12 and 16, are smaller, however, than the field-magnets. The cores are ¼ in. stove-bolts, 1¼ in. long under the head. They are placed 2 in. apart, center to center. They are insulated and wound as fully explained in [App. 88]. These ¼ in. bolts require a change in your winder. ([See App. 147] for this.) If you wish to use 5⁄16 bolts, you may use the same axle for your winder as before. The washers are ⅝ in. apart, inside. The cores are wound with 4 or 6 layers of No. 24 or 25 wire. This makes them about ¾ in. in diameter. They are held in a tin yoke, 14, made of 5 or 6 thicknesses of tin. 14 is 3 × ¾ in., and has 3 holes punched in it. The two outside holes are 2 in. apart. Through these pass the bolts, which are held firmly by the 2 nuts. The shaft, S B, is a sink-bolt, 3 in. long, and ¼ in. in diameter. ([See § 253].) The inside ends ([§ 123]) of the coils should be firmly twisted together or held under the top nuts to make a good connection between them.
Fig. 120.