Fig. 258.—Diagram showing how to connect the Armature Winding to the Commutator.
The commutator is provided with a small brass machine screw threaded into each section near the edge as shown in Figure 257. These screws are to receive the ends of the armature winding and so facilitate connections.
The commutator, shaft and armature are assembled as shown in Figure 258.
The armature may be held to the shaft by a small set screw or a pin. The commutator should fit on the shaft very tightly so that it will not slip or twist.
Every part of the armature and shaft touched by the armature winding must be insulated with paper which has been soaked in shellac until soft. The armature must be left to dry before winding.
The armature should next be wound with No. 20 B. & S. gauge single-cotton-covered magnet wire. Sufficient wire should be put on to fill up the winding space completely. Care should be taken, however, not to put on too much wire or it will interfere with the field magnets and the armature cannot revolve. After winding the armature, test it carefully to see that the wire is thoroughly insulated from the iron.
Fig. 259.—Details of the Wooden Base.
If the insulation is correct, paint the whole armature with thick shellac varnish and bake it in a warm oven to set the shellac.