The morning news. [volume] (Savannah, Ga.) 1887-1900, 1895-01-13

magnet a change is made in the lines Of
force.
Now. the current Of electricity formed
when a single wire is moved within the
magnetic field is very weak. 1t can only
be detected by an instrument made for
testing electric currents called a gal
vanometer. BY doubling the wire back
and forth upon itself like q skein of yarn,
or as a fish line is wound on a piece of
cardboard, and then passing all the coils
through the magnetic field, a stronger
current is made or induced. The stronger
the magnet is the stronger the current of
electricity will be- and as an electro
magnet is many times more powerful
than steel magnet electro-magnets are
used in modern dynamos. The earlier
dynamos were made with permanent
steel magnets. and, compared with the
generators used to-day, they were clumsy,
weak machines; but the same bottom fact
is the foundation Of all dynamos, and that
IS that II a wire be moved within a mag
netic field a current of electricity is set
to flowing in the wire; or if the magnet
be moved the same result win surely fol-
low, and electricians call that phenome
non 'magneto-electric induction Differ
ent makes of dynamos have various forms
and shapes and do their work in different
ways, but the same principle uuderlies all
The dynamo with all its mysterious
powers, is a simple machine. 1t consists
OF two principal parts, the armature and
the field magnets. If were to go on and
tell you all Of the different kinds Of ma
chimes made-such as mUlt-phase, alter
mating, continuous, and fifty others-you
would know less about them than you do
now so 1 will only show you how
simple, ordinary dynamo works
The armature is the revolving part
of the machine. 1t turns round In the
magnetic field, for it revolves between the
poles CT the field magnets. The field
magnets form part of the framework of
the machine, which is heavy iron cast
ing. The armatUre is the most important
part and the most difficult to make up.
Tor II must be built up 1t is really part
Of the shaft, on one end of which is the
pulley, over which runs the belt from the
lying wheel Of the engine. Unlike the
field magnets, which are made of casr
iron, the body of the armature is made of
great many pieces of sheet iron cut
into fiat circular shapes or disks. Each
disk has large hole in the center, so il
can slip over the shaft, and also several
smaller holes for the Ions bolts which
hold all disks together. Each disk is sep
arated from the other by similar disks
of mica or some other substace NOT IN
huenced by electricity, so that each is
insulated or electrically separated from
us neighbor. The workman first Sins on
an IRON disk, then mica disk and then
an iron one, and so on until the Iarntnated
core OF the armature is built up. Heavy
cast iron plates are put at each end of
the core, and long bolts passing THROUGH
all the iron and mica disks hold the arua-
ture solidly together. This laminated
core Is used because if the core were made
of solid iron it would set up d little cleo
rical arrangement of its own and become
very hot. When the core is built I'D if
Is put in lathe and turned to a smooth
surface.
Next the armature is wound. This
dose not mean that a long wire is wrapped
around the armature core, for as a matter
or fact, the wire is cut in pieces as long
as the armature and laid on the core
IengthWise. This wire is genrally heavy.
and is covered with some insulating ma
teIial. When the wires are laid in pace
1hey are held to the core by bands of Ger
man silver wires. so that they VIII not
fly out when the armature revolves
Each length of wire on the arna+,1re
Is connected with the commutator' which
Is a device on the aramture shaft wbere
all the different currents of eiectricit,, I
are collected, otherwise the electricitv
would be lost. The coinmutator roiobt
De called the ends of the wires on the or-
mature Tor 1t Is made of pieces Of conner /
separated from one another bv mica Or
ranged around the shaft at tba erd -.
the armature core. Each section Of the
ccmmutator is connected with one or more /
wires and the electricity is taken off the
copper sections by the brushes ,rb,cb /
Iouch the commutator The brushes arc /
strips of copper or pieces OF. carbon one
pressing on one side and the other on ~
opposite side of the commutator A.
the srmature shaft revolves. CAUSING tn I
arnature to rotate each section of ina
cornnutator comes in contact with the /
brushes which pick it up. me
The framework of a dy-nsr,o i..,
in all sorts of shapes but part Of If e vn,r5
with many coils of insulated wire sor,a
OF the dynamos are in general shane ILL.,
large horseshoe magnets; others H.
two horseshoe magnets Joined together ny /