Two small holes should be bored in the feet of the field magnet to receive No. 3 wood screws, which fasten the field to the base.
The Bearings are shown in detail in Figure 247. They are easily made by cutting from sheet-tin. Two small washers, serving as collars, should be soldered to the shaft as shown in Figure 243.
The Commutator Core is formed by cutting a strip of paper five-sixteenths of an inch wide and about five inches long. It should be given a coat of shellac on one side and allowed to get sticky. The strip is then wrapped around the shaft until its diameter is three-sixteenths of an inch.
The Base is cut from any ordinary piece of wood and is in the form of a block about two by one and one-half by one-half inch.
Fig. 248.—The Complete Motor.
Assembling the Motor. The parts must be carefully prepared for winding by covering with paper. Cut a strip of paper one-half inch wide and one and one-eighth of an inch long and give it a coat of shellac on one side. As soon as it becomes sticky, wrap it around the top bar of the field magnet. 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.
This is accomplished by looping a small piece of tape or cord over it. The next two turns are then taken over the ends of the loop so as to embed them. Wind on three layers of wire and when in the middle of the fourth layer embed the ends of another loop, which may be used at the end of the fourth layer to fasten the end so that it will not unwind. After the winding is finished, give it a coat of shellac.
The winding of the armature is somewhat more difficult.