Figure 258 is a diagram showing how the winding is made and connected. It is wound about the armature, always in the same direction, just as if the armature were an ordinary electro-magnet.
The ends of the winding are each connected to one of the commutator sections by scraping the wire and placing it under the screws.
The winding space in the field magnet should be shellacked, and insulated with brown paper by wrapping the core with a strip of paper and covering the bobbin ends with circular pieces made in two halves.
The field magnet is wound full of No. 20 B. & S. gauge single-cotton-covered wire. The wire should be put on in smooth, even layers and the winding space completely filled up.
Fig. 260.—The Pulley and Bearings.
The base for the dynamo is a piece of hard wood, five inches long, four inches wide, and five-eighths of an inch thick.
The bearings are small brass castings of the dimensions shown in Figure 260. It is necessary first to make a wooden pattern and send it to the foundry for the castings.
The bearings are fastened to the projecting arms on the field casting by means of machine screws eight-thirty-seconds of an inch in thickness.
The field magnet should not be screwed down on to the base until the armature runs easily and truly in the tunnel.