The fibre bushing is a hollow cylinder, five-sixteenths of an inch in diameter and seventeen thirty-seconds of an inch long. The bushing should force tightly on the shaft. The segments are make by turning a piece of three-quarter inch brass rod in a lathe until it is one-half an inch in diameter for a distance of about seven-sixteenths of an inch. A five-sixteenths inch hole should be bored through the center so that it will fit tightly upon the fibre bushing.
FIG. 64.—Showing how the Coils on a Six-pole Armature are arranged and connected.
Then cut the brass off one-half inch from the end so that it leaves a flange at one end, three-quarters of an inch in diameter. Saw it lengthwise into three equal parts and mount it upon the fibre bushing with a small strip of mica between each two sections to fill in the space made by the saw cuts. The sections are held together by a fibre ring, three quarters of an inch in diameter outside and one-half an inch in diameter inside. The ring should fit very tightly over the commutator and be forced down flush against the shoulder. After the ring is in position, file any mica which may project out of the slots down even with the surface of the segments and force the commutator onto the shaft with the shoulder against the armature. The commutator must fit very tightly so that there is not any possibility of moving it after it is in position.
FIG. 65.—Details of the Commutator.
The sections should bear a certain relative position to the armature windings. The diagrams in Figures 63 and 64 show the proper position for the three and six pole armature respectively.
The coils are connected to the commutator by soldering the terminals to the shoulder on each segment. This work should be very carefully done so as to insure a neat job and connection of the proper terminal to the proper section.
FIG. 66.—Details of the Bearings, Shaft, and Pulley.