The Armature. Two strips of tin, three-eighths of an inch by one and one-half inches, are cut to form the armature. They are slightly longer than will actually be necessary, but are cut to length after the finish of the bending operations. Mark a line carefully across the center of each strip. Then, taking care to keep the shape symmetrical so that both pieces are exactly alike, bend them into the shape shown in Figure 243. The small bend in the center is most easily made by bending the strip over a knitting-needle and then bending it back to the required extent.
Fig. 245.—The Field.
A piece of knitting-needle one and one-half inches long is required for the shaft. Bind the two halves of the armature together in the position shown in Figure 249. Bind them with a piece of iron wire and solder them together. The wire should be removed after they are soldered.
Fig. 246.—The Field and Commutator.
The Field Magnet is made by first cutting out a strip of tin one-half by four and then bending it into the shape shown in Figure 245.
The easiest way of doing this with accuracy is to cut out a piece of wood as a form, and bend the tin over the form. The dimensions shown in Figure 245 should be used as a guide for the form.
Fig. 247.—The Bearings.