ase (J) should be countersunk, as at M, so
the head of the nut will not project. The fields of the dynamo are now
secured in position to the base.

[Illustration: _Fig. 24._ DETAILS OF THE ARMATURE, CORE

_Fig. 25._ DETAILS OF THE ARMATURE, BODY]

THE ARMATURE.--A bar of iron (Fig. 24), 1" x 1" and 2-1/4 inches long,
is next provided. Through this bar (1) are then bored two 5/16-inch
holes 1-3/4 inches apart, and on the opposite sides of this bar are two
half-rounded plates of iron (3) (Fig. 25).

ARMATURE WINDING.--Each plate is 1/2 inch thick, 1-3/4 inches wide and 4
inches long, each plate having holes (4) to coincide with the holes (2)
of the bar (1), so that when the two plates are applied to opposite
sides of the bar, and riveted together, a cylindrical member is formed,
with two channels running longitudinally, and transversely at the ends;
and in these channels the insulated wires are wound from end to end
around the central block (1).

MOUNTING THE ARMATURE.--It is now necessary to provide a means for
revolving this armature. To this end a brass disc (5, Fig. 26) is made,
2 inches in diameter, 1/8 inch thick. Centrally, at one side, is a
projecting stem (6) of round brass, which projects out 2 inches, and the
outer end is turned down, as at 7, to form a small bearing surface.

[Illustration: _Fig. 26._ JOURNALS _Fig. 27._ COMMUTATOR,
ARMATURE MOUNTINGS]

The other end of the armature has a similar disc (8), with a central
stem (9), 1-1/2 inches long, turned down to 1/4-inch diameter up to
within 1/4 inch of the disc (7), so as to form a shoulder.

THE COMMUTATOR.--In Fig. 27 is shown, at 10, a wooden cylinder, 1 inch
long and 1-1/4 inches in diameter, with a hole (11) bored through
axially, so that it will fit tightly on the stem (6) of the disc (5). On
this wooden cylinder is driven a brass or copper tube (12), which has
holes (13) opposite each other. Screws are used to hold the tube to the
wooden cylinder, and after they are properly secured together, the tube
(12) is cut by a saw, as at 14, so as to form two independent tubular
surfaces.

[Illustration: _Fig. 28._ END VIEW ARMATURE, MOUNTED]

These tubular sections are called the commutator plates.

[Illustration: _Fig. 29._ TOP VIEW OF ARMATURE ON BASE]

In order to mount this armature, two bearings are provided, each
comprising a bar of brass (15, Fig. 28), each 1/4 inch thick, 1/2 inch
wide and 4-1/2 inches long. Two holes, 3 inches apart,