The Richmond palladium and sun-telegram. [volume] (Richmond, Ind.) 1907-1939, 1919-11-22
The Automobile Cut-out.


AS was shown in the first lesson on
Starting and Lighting. when the en-
CINE Is idle the generator will not be
sendig current to the battery, but the
current from the battery will flow to
the generator, and so. unless some de-
vice, which will disconnect the bat
terry and generator. is used, the bat
terry will soon be discharged.
The device used tor this purpose IS
called an Automatic Cut-out and some
times a Relay.
Not only must the cut-out be used
when the engine Is idle, but also when
II is running slowly, as at the slow
speed the voltage OF the current, made
by the generator, will be less than the
voltage Cor pressure) Of the battery
and so under this condition the cur
rent would also flow from the battery
20 the generator, and so the battery
becomes discharged
From the above we see that the pur-
pose Of the cut-out Is to disconnect
the battery and generator the moment
the voltage OF the battery is greater
Than the voltage Of the generator, and
t. connect them, the moment the gen
e~ator voltage is greater than that OF
The battery.
The cut-out is arranged to act at
an engine speed Of about $50 revo!u-
tons per minute, or a car speed of
about Is miles per hour. Thus you
will notice that the generator will
charge the battery only at car speed
greater than IS miles per hour.
Let us see how the automatic cut
out operates. Were current Of cleo
tricity to TOW through coil B, Fig. l.,
in the direction Of the arrows, then
the core A would become magnet,
and would draw piece Of steel to
its ends. If current were also made
to flow through coil G, in the direc-
ton Of the arrows, the magnetic
strength Of the core would be increas-
ed. but should the current flow
through c in the reverse direction,
then this coil would act against the
coil B, and so the core would lose
magnetism created by B would be alb
sorbed by C. 1t is on this principle
that most cut-outs operate.
Fig. 2 shows the condition Of a
Bosch cut-out when the generator Is
making a current OF high voltage
than that Of the battery. Here you
will notice. by studying the arrows,
that the curre~t is fowig In the same
direction through both coils, B and c
The core is therefore a magnet and
has drawn down the Button again st
the spring action and SO closed the
contacts. Thus the battery and gen.
orator are connected or "cut In"
Fig. 3. shows the condition when
the generator voltage is less than the
battery voltage. BY studying the ar
rows you will notice that the curren,
flows through the coils B and c In
opposite directions. The magnetizina
action OF the one coil will now neu
tralize that OF the other, and so the
core will cease to be a magnet and
Will no longer draw down the button
The contact points will therefore
open. and the battery and generator be
disconnected on "Cutout."
The position OF the cutout varies ir
different makes OF cars. Sometimes II
1t placed on top or on the side OF the
generator. and often It Is placed on
the dash.
Should your battery become dis
charged over night. it nay be due tc
the contact points Of the cut-out stick
Ing, or to the spring, which pulls them
apart, being broken, loose or weak
When the engine IS idle the contacts
should be open.
Failure Of the generator to charge
the battery may also be due to the
automatic cut-out In this case the
trouble Will be due to the contacts no.
being pulled together. or to the con
tact points being so burned or pittet
as to make a poor contact. They
should be closed at the higher engine
speeds.