The Commutator Core is formed by cutting a strip of paper three-eighths of an inch wide and about five inches long. It should be given a coat of shellac on one side and allowed to dry until it gets sticky. The strip is then wrapped around the shaft until its diameter is three-sixteenths of an inch. The sticky shellac should be sufficient to hold the paper tightly in position when dry.
The Base is cut from any ordinary piece of wood and is in the form of a block about two and one-half by one and seven-eighths by one-half inches thick.
FIG. 13.—Side view of the Armature and Commutator Core assembled on the Shaft before winding.
Assembling the Motor—The parts must be carefully prepared for winding by covering with paper. Cut a strip of paper five-eighths of an inch wide and one and three-eighths inches long and give it a coat of shellac on one side. As soon as it becomes sticky, wrap it around one of the two upper vertical parts of the field magnet as indicated in Figure 11. Both sides of the field should be insulated with paper in this manner. The armature is insulated in exactly the same way, taking care that the paper covers the entire flat portion.
The field and armature are now ready for winding. It is necessary to take proper precautions to prevent the first turn from slipping out of place.
The field should be wound first. This is accomplished by looping a small piece of tape or cord over it at the point indicated by "A" in Figure 15. The next two turns are then taken over the ends of the loop so as to embed them. Wind on three layers of wire on one side and then run the wire across to the other side and wind on three layers there. The third layer of wire in the second coil should end at "B." It should be fastened into position by a loop of string so that it will not unwind.
FIG. 14.—Showing the Motor assembled on the Base so that all the parts may be lined up before winding.
This method divides the field winding into two parts, both of which are connected together. The outside layer of the first coil is connected to the inside layer of the second coil. The two coils really form one continuous winding divided into two parts. After the winding is finished, give it a coat of shellac.