1917 Cadillac - GM Heritage Center

ADJUSTMENTS 63
CADILLAC-DELCO ELECTRICAL
SYSTEM
The Cadillac-Delco system is the single wire, single unit system.
One side of the motor generator, storage battery, lamps, horn and ignition
apparatus is connected to some part of the frame of the car or the
engine. The other connections are made with copper wires or cables.
The motor generator serves both as a generator of current and as an
electric motor for cranking the engine when starting. The principal elements
of the motor generator are an armature and a field. There are two windings
on the armature and two in the field—one on the armature and one on the field
are used when the motor generator is used as a generator and the other windings
when it is used as a motor.
The motor generator, when acting as a generator, is driven at engine
speeds by the fan shaft which in turn is driven by a silent chain from the
cam shaft at the front end of the engine. Thus driven, it delivers electrical
energy for charging the storage battery and for operating the lights, ignition
apparatus and horn. To prevent the voltage of the current generated from
rising too high when the engine is running at high speeds, the third brush
system of current regulation is employed.
When, acting as a motor the sole function of the motor generator is to
crank the engine. In starting, the first thing the operator does is to push
down the ignition lever on the combination switch. This closes the ignition
circuit and the circuit between the storage battery and the generator windings
on the motor generator causing the armature to revolve slowly.
A ratchet clutch in the front end of the generator allows the armature
to rotate ahead of the driving shaft. The clicking noise that is heard when
the ignition switch is turned on comjes from this clutch.
Next the operator pushes down the starter button. The first movement
causes the starter gears to mesh with the teeth on the fly-wheel. The probability
of the ends of the teeth striking and failing to mesh is overcome by the
slow rotation of the armature which began as soon as the ignition was turned
on.
As the starter button is pushed further down the current between the
storage battery and the generator windings of the motor generator is broken.
Upon the last movement of the starter button the circuit is closed between
the storage battery and the motor windings on the motor generator causing
it to act as a powerful electric motor which rapidly cranks the engine.
As the gear ratio between the armature shaft and the crank shaft is
approximately 35 to 1 the armature would be driven at an excessively high
rate of speed after starting the engine and before the operator let the starter
button back if it were not for an over-running clutch in the hub of the
idler gears between the fly-wheel and the armature shaft. The electric motor
cranks the engine through this clutch but after the engine has started and
begins to run faster than the electric motor, the clutch slips.
When the starter button is let up, as soon as the engine is running
under its own power, the first movement of the button breaks the circuit
between the electric motor and the storage battery, a further movement
causes the starter gears to slide out of mesh and the final movement completes
the circuit between the generator and the storage battery, which was
broken when the starter buttoa was pushed down. The engine running and
the circuit being closed between the storage battery and the generator windings
of the motor generator, the generation of current begins.