ATWATER KENT IGNITION SYSTEM, TYPE K-2
The operating principle of the Atwater Kent ignition system type K-2,
differs from type CC system in that it operates on the open circuit
plan, whereas the type CC system explained in the preceding chapter,
operates on the closed circuit plan.
A-K ignition system type K-2 consists of three parts:
No. 1. The unisparker combining the special contact maker, a condenser,
and a high tension distributor.
No. 2. The coil, consisting of a simple primary and secondary winding,
and a condenser. These parts are all imbedded in a special insulating
compound. The coil has no vibrator or other moving parts.
No. 3. The ignition switch. This switch controls the system by opening
and closing the primary current.
=The Principle of the Atwater Kent System.=--The function of this
system is to produce a single hot spark for each power impulse of the
motor. It differs from other types of battery ignition systems in that
the contact points do not touch except during the brief instant of the
spark. The ignition circuit is, therefore, normally open, whence the
name “open circuit” results. The contact maker consists of a pair of
contact points, normally open, which are connected in series with a
battery, and the primary circuit of the non-vibrating induction coil.
The mechanism for operating the contacts consists of a notched shaft
having one notch for each cylinder, rotating at one-half the engine
speed, a lifter which is pulled forward by the rotation of the shaft,
and a coil spring which pulls the lifter back to its original position
after it has been drawn forward and released by the notched shaft;
hardened steel latch, against which the lifter strikes on its recoil
and which in turn operates the contact points.
[Illustration:
LATCH
CONTACT SCREW
NOTCHED SHAFT
LIFTER
CONTACT SPRING
LIFTER SPRING
Fig. 71. Atwater Kent Contact Breaker--Diagram of Action--Type K-2
System.]
[Illustration: Fig. 72. Atwater Kent Contact Breaker--Diagram of
Action--Type K-2 System]
[Illustration: Fig. 73. Atwater Kent Contact Breaker--Diagram of
Action--Type K-2 System]
[Illustration: Fig. 74. Atwater Kent Contact Breaker--Diagram of
Action--Type K-2 System]
=Operation of the Contact Maker.=--It will be noted in Fig. 71 that
the lifter is being pulled forward by the notched shaft. When pulled
forward as far as the shaft will carry it (Fig. 72), the lifter is
suddenly pulled back by the lifter spring. In returning, it strikes
against the latch, throwing this against the contact spring and closes
the contact for a brief instant. This movement is far too quick for
the naked eye to follow (Fig. 73).
Fig. 74 shows the lifter ready to be pulled forward by the next notch.
Note that the circuit is closed only during the brief instant of the
spark. No current can flow at any other time, not even if the switch is
left on when the motor is not running. No matter how slow or how fast
the notched shaft is turning, the lifter spring will always pull the
lifter back at exactly the same speed, so that the operation of the
contact, and therefore the spark, will always be the same no matter
how fast or how slow the engine is running. The brief instant that
the contact points touch, results in very little current consumption.
The high tension current from the coil is conveyed to the rotating
distributor block, which seats on the end of the unisparker shaft to
each of the spark plug terminals in the order of firing.
[Illustration: Fig. 75. Atwater Kent Distributor and Contactless Block]
The important advantage which the distributor possesses is the fact
that there are no sliding contacts or carbon brushes. The distributor
blade is so arranged that it passes close to the spark plug terminals
without quite touching (as shown in Fig. 75), thus permitting the spark
to jump the slight gap without any loss of current pressure. This also
eliminates all wear and trouble caused by sliding or rubbing contacts.
Fig. 76 shows the wire connections and direction of current flowage.
The distributor blade is about to make contact with the terminal
leading to the spark plug in No. 2 cylinder. At the instant that
contact is made the breaker points in the contact maker shown in the
lower part of the diagram close, thus allowing a primary or low tension
current to flow between the contact maker, coil, and battery. The
sudden breaking of this current occurs when the points open again,
thereby creating a current of high tension voltage in the secondary
coil which is conducted to the center terminal of the distributor where
it is distributed to the spark plug terminals through the rotation
of the distributor blade. The high tension cables leading from the
distributor are heavily insulated, thus the current in seeking ground
return chooses the easiest path, by jumping the slight gap at the spark
plugs.
[Illustration:
DISTRIBUTOR
GROUND
COIL
BATTERY
CONTACT MAKER
Fig. 76. Atwater Kent Wiring Diagram Type K-2]
=Setting and Timing the Unisparker.=--The type K-2 unisparker is
installed, so as to allow a small amount of angular movement or, in
other words, the socket into which the unisparker fits is provided
with a clamp which will permit it to be turned or locked in any given
position.
=Timing.=--The piston in No. 1 cylinder is raised to high dead center
between the compression and power stroke. Then loosen the clamp which
holds the unisparker and turn the unisparker backward, or contrary to
the direction of rotation until a click is heard. This click happens
at the exact instant of the spark. Clamp the unisparker tight at this
point being careful not to change its position. Note that current for
this system is usually supplied by the starting and lighting battery.
When changing batteries be sure that the voltage of the battery is the
same as that marked on the coil.
[Illustration:
TO PLUGS
TO PLUGS
CONTACT-MAKER
CONTACT MAKER
SWITCH
BAT.
S & INT.
INT.
S.
COIL
INT.
INT.
SEC
GROUND TO MOTOR
GROUND TO MOTOR
POS
NEG
BATTERY
Fig. 77. Atwater Kent K-2 Wiring--Cut 1, Under Hood Coil; Cut 2, Kick
Switch Coil]
The external wiring of the A-K type K-2 is very simple, as shown in the
diagrams, Figs. 77 and 77A. Fig. 77 shows the wire connections, when
the reversing switch and under-hood coil is used. Fig. 77A shows the
connections, when using plate or kick switch coil. A well insulated
braided primary wire is used for the primary or battery circuit. See
that this wire is well protected against rubbing or abrasion wherever
it comes into contact with metal parts of the car. When the starting
and lighting battery is used to furnish the ignition current, two wires
should run directly to the battery terminals.
The two types of Atwater Kent systems described are provided with
automatic spark advance mechanism. Provisions are also made for manual
lever control, by simply connecting the unisparker to the throttle
lever at the base of the steering gear.
[Illustration: Fig. 78. Atwater Kent Automatic Spark Advance
Mechanism--A K Type K-2]
Fig. 78 shows the automatic spark advance mechanism. It is located on
the underside of the contact maker base plate, and consists of a set
of weights which swing out from the center against spring tension,
and advances the unisparker on the shaft, according to the amount of
centrifugal action or speed of the shaft. When the shaft is not in
motion the springs draw the weights toward center, which automatically
shifts the unisparker on the shaft until the spark is in a fully
retarded position.
=Contact Point Adjustment.=--The only adjustment aside from the initial
timing is in the contact points. They are adjustable only for natural
wear, and one adjustment should last at least six months. The contact
screw is provided with a number of shim washers against which it is
set up tight. When the points eventually become worn, they should be
dressed flat and smooth. A sufficient number of the washers should
be removed so that when the contact screw is set up tightly it will
maintain the proper gap between the points. The distance between the
contact points should be about the distance of a thin visiting card.
They should never touch when at rest.
[Illustration:
Oil lightly every
1000 miles
Oil
Fig. 79. Atwater Kent Contact Breaker--Oiling Diagram--A-K Type K-2]
Fig. 79 shows an oiling diagram of the contact maker. The latch,
lifter, and lifter spring are not adjustable or subject to wear. They
should be well cleaned and oiled every five hundred miles. Use a light
oil and avoid getting it on the contact points.
=The Condenser.=--The condenser of this system acts somewhat like a
shock absorber to the contact points. It absorbs the spark or arc and
makes the break in the primary current, clean and abrupt. The condenser
is very accessible, but should never be tampered with, as it does not
require any attention.
=Testing for Ignition Trouble.=--If the engine misses without regard to
speed, test each cylinder separately by short circuiting the plug with
a screw driver, allowing a spark to jump. If all cylinders produce a
good regular spark the trouble is not with the ignition system.
If any cylinder sparks regularly this will indicate that the ignition
system is in working order so far as the unisparker and coil are
concerned. The trouble is probably in the high tension wiring between
the distributor and plug, or in the plugs themselves. Examine the plugs
and wiring carefully. Leaky secondary wiring is frequently the cause
of missing and backfiring.
Frequently, when high tension wires are run from the distributor to the
spark plugs through a metal tube, trouble is experienced with missing
and backfiring, which is due to induction between the various wires in
the tube. This is especially likely to happen if the main secondary
wire from the distributor to the coil runs through this tube with the
spark plug wires.
Whenever possible the distributor wires should be separated by at least
one-half inch of space. They should be supported by bracket insulators,
rather than run through a tube. In no case should the main distributor
wire run through a conduit with other wires.
If irregular sparking is noted at the spark plugs, examine the battery
and connections.
If the trouble commences suddenly, it is probably due to a loose
connection in the wiring, if gradually, the battery may be weakening or
the contact points may require attention.