The winding of the armature is somewhat more difficult. The wire used for winding both the armature and the field should be No. 25 or No. 26 B. & S. Gauge double cotton-covered.
FIG. 15.—The Field Frame with the Winding in position.
In order to wind the armature, cut off about seven feet of wire and double it back to find the center. Then place the wire diagonally across the center of the armature so that there is an equal length on both sides. Place a piece of paper under the wire at the crossing point to insulate it. Then, using one end of the wire, wind four layers on half of the armature. Tie the end down with a piece of thread and wind on the other half.
The ends of the wire are cut and scraped to form the commutator segments. Figure 17 shows how this is done.
FIG. 16.—The Armature Winding before the Commutator is completed.
Bend the wires as shown so that they will fit closely to the paper core. Bind them tightly into position with some silk thread. Use care so that the two wires do not touch each other. Cut the free ends of the wire off close to the core.
When finished, the relative positions of the armature and the commutator should be as shown in Figure 17.
Figure 14 shows how the motor is assembled. The windings are not shown for the sake of clearness. The armature should be exactly in the center of the field. The bearing holes should be in the correct position and should permit the armature to revolve freely.