Evening star., 1897-01-16

is cotton-covered wire, in the manner
shown by figure 2, care being taken to
wind evenly, and enough layers being
wound on to bring the wire flush with the
surfece of the core When the winding
: was finished both ends of the wire were
together at the long end of the shaft
JOINS next operation was to bind one
end OF the wire to the shaft by two layers
or cotton batting, a quarter of an inch
wide. Around the cotton he then fastened
strip OF sheet copper, also a quarter of
an 1Ech wide. A quarter of an inch fur
ther toward the end of the shaft another
layer of cotton and copper was wound in
the same way, excepting that no wire was
pound under it. These two bands of cop
Per are known as "cOmmutators," the
bound wire being fastened to the further
rand and the unbound wire to the end
nearest the core.
About the Frame.
Next came the frame. 1t was made of
four pieces of wood, the base being six
inches long. a half an inch wide and two
inches high. The top piece was an inch
longer than the base, and hree-auarters of
an inch WIDE. The two end pieces were six
inches long. three-quarters of an inch wide
ana haif an inch thick. They were all
screwed toSether, so as to make strong
frame. John had to be careful to get the
end surface of each piece of wood perfect
~ true and square, otherwise the frame as
a whole must have been distorted and 'out
OF pIumD. In each of the end pieces n
mole vas made large enough to allow the
smart to pass through. These holes were 10
serve as bearings and the armature had to
De placed In position before the second end
piece OF the frame could be screwed IN
Inc appearance of the whole at this stage
OF construction is shown in figure g.
ine next thing was the construction of
what are known as the fields" First
the two plates of iron were bent in the
manner shown in the cut leaving two and
quarter inches fiat at one end-the lower
ana one and quarter a. the upper Next
the lower fiat surface of each plate was
insulated by wrapping it with paper to
within one-quarter of an inch of the
bend. Then four layers Of the No 1s COP
per wire were evenly wound over the paper.
both ends of the wire, in each case, being
brought to the same end of the iron plate
Next the upper ends of the two plates
were screwed fast to the top piece of the
frame; this caused the plates to assume an
upright position, with the wound end of
each resting against the base piece, and
these were held firmly in place by a strip
of tin screwed to the wood of the end
pieces and passed over the wound wire
cut.
When the work had progressed thus far.
John found that the armature was lying
In such way that 1T could be easily re-
VOWED In space between the concaye
surfaces of the fields. though it nearly
touched them. and that nothing remained
TO be done excepting to provide way for
the current to pass between the two sur
1aces-Which answered to the electro mag
net OF a dynamo-and through the arma-
ture. which then" Johns friend explained.
viii begin to whirl at practically the
same rate of speed as the dynamo.
Some Further Details.
Two strips of sheet "copper" each two
inches long by quarter of an inch wide.
were then cut. In each of these strips
i
quarter of an inch from one end. Through
the short end he bored hole, and through
TINS ne screwed the strips fast to the base
oil the frame, in such a way as to bring the
lons ends in contact with the commutators
in the manner shown by the .ut The
screw which fastened the copper strip-or
"brush'-nearest the end was allowed to
project about quarter of an inch, and
was to be used as one of the binding
posts or point Of connection from the
dynamo. About quarter of an inch from
this screw-or binding posr-he drove an
other screw, in the base. and allowed it
also to project about a quarter of an inch
This was to serve as the other binding
post or point OF connection with the dy-
namo
From the coil around the lower rart of
each piece of iron forming the fields" 1t
VIII be remembered. there extended two
wire from each coil was now connected
with the other. the remaining free end
from one coil being connected with the
strip of copper-or brush-nearest the field
while the one from the other coli was
connected with the projecting screw or
binding post that had been driven into the
wood.
Then wooden pulley, or driving wheel,
with groove for round belt, was at
tached to the end of the arma.ure shaft
projecting from the frame and the cleo
trio current was turned on.
Now" said Johns friend. eff you were
to apply power to the motor instead of to
the dynamo current would be generated
by the motor and the dynamo could be
operated as motor. In other words, a
dynamo may be used as motor and q
motor may be used as a dynamo. They
are interchangeable. the same as the two
wheels in the circular trough of water.
But different type of machine is used for
the motor from that used for the dynamo,
the type chosen for use as dynamo being
more efficient in developing the current,
just IS the one used for the motor is more
efficient in utilizing it."