more parts than the simpler type shown in Fig. 69,
possesses distinct advantages in the matter of winding. By virtue of
its simpler form of winding space, it is easier to insulate and easier
to wind, and furthermore, since the shaft does not run through the
winding space, it is capable of holding a considerably greater number
of turns of wire. The ends of the armature winding are connected, one
directly to the frame and the other to an insulated pin, as is shown
in the illustration.

[Illustration: Fig. 70. Generator Armature]

[Illustration: Fig. 71. Generator Field and Armature]

The method commonly employed of associating the pole pieces with each
other and with the permanent magnets is shown in Fig. 71. It is very
important that the space in which the armature revolves shall be truly
cylindrical, and that the bearings for the armature shall be so
aligned as to make the axis of rotation of the armature coincide with
the axis of the cylindrical surface of the pole pieces. A rigid
structure is, therefore, required and this is frequently secured, as
shown in Fig. 71, by joining the two pole pieces _1_ and _2_ together
by means of heavy brass rods _3_ and _4_, the rods being shouldered
and their reduced ends passed through holes in flanges extending from
the pole pieces, and riveted. The bearing plates in which the armature
is journaled are then secured to the ends of these pole pieces, as
will be shown in subsequent illustrations. This assures proper
rigidity between the pole pieces and also between the pole pieces and
the armature bearings.

The reason why this degree of rigidity is required is that it is
necessary to work with very small air gaps between the armature core
and its pole pieces and unless these generators are mechanically well
made they are likely to alter their adjustment and thus allow the
armature faces to scrape or rub against the pole pieces. In Fig. 71
one of the permanent horseshoe magnets is shown, its ends resting in
grooves on the outer faces of the pole pieces and usually clamped
thereto by means of heavy iron machine screws.

With this structure in mind, the theory of the magneto generator
developed in connection with Fig. 68 may be carried a little further.
When the armature lies in the position shown at the left of Fig. 71,
so that the center position of the core is horizontal, a good path is
afforded for the lines of force passing from one pole to the other.
Practically all of these