FIG. 31.—Details of the Field Pedestal.
Mark a line carefully across the center of each of the three strips and then bend them into the shape shown in Figure 20, making certain to keep the shape symmetrical so that all three, pieces are exactly alike. The bend in the center of each strip should fit nicely over the shaft. This result is most easily reached by bending the strips over a knitting-needle and then bending them back the required amount.
FIG. 32.—Showing how the Field Coils are Wound.
The Shaft is a piece of knitting-needle one and seven-eighths of an inch long. Assemble the three strips on the shaft as shown in Figure 21 and bind them temporarily together with a piece of iron wire. Then solder the edges together and remove the wire.
The Commutator Core is formed of a strip of paper, three-eighths of an inch wide and about five inches long, wrapped around the shaft until the diameter of the small cylinder thus formed is three-sixteenths of an inch. The paper strip should be given a coat of shellac on one side and allowed to dry until it becomes sticky before it is wrapped around the shaft. The sticky shellac should be sufficient to hold the paper tightly in position when dry and to form a hard, firm core when dry.
The Winding of the Armature is not difficult. The size of the wire used should be No. 25 or No. 26 B. & S. Gauge, double cotton-covered.
Wrap a strip of paper around each section of the armature so that the wire will be protected from any sharp edges on the tin which might cut through the insulation.
Wind four layers of wire on each section of the armature. Each section should be wound in the same direction as the others. The terminals of the wires should be scraped clean and connected together in the following manner: Connect the outside end of one section to the inside end of the next section. We will presume that the three sections of the armature are lettered "A", "B" and "C." Connect the outside end of "A" to the inside of "B"; the outside of "B" to the inside end of "C" and the outside end of "G" to the inside of "A."
The portion of the wires forming the connections between the three armature coils are used to form the three sections of the commutator.