NORTH EAST IGNITION SYSTEM
The N.-E. Model O Distributor Ignition System is used on Dodge Brothers
cars. This system provides high tension ignition for the engine by
transforming the low voltage of the starter generator or the battery
into a high voltage capable of jumping freely between the spark plug
electrodes. This is accomplished through the agency of an induction
coil, the primary winding of which, in series with an interruptor or
contact breaker, receives current under normal running conditions from
the starter generator. The starting and lighting battery, however,
supplies this current instead of the generator whenever the engine is
starting or running very slowly.
At each interruption of the primary current there is set up in the
secondary winding of the coil a high tension current, and this current
flows from the coil through a high tension cable to the distributor
rotor from which point it is selectively conducted to the proper spark
plug. Upon reaching the spark gap in the plug, it jumps from the inner
electrode to the outer one, which is grounded, and then returns through
the engine frame to the grounded end of the secondary winding on the
ignition coil. The high tension spark thus produced in the cylinder
ignites the gas and so brings about the necessary combustion.
=Wiring= (Fig. 62).--As will be evident upon reference to the
accompanying wiring diagram, the primary circuit of the ignition system
leads from the positive terminal of the battery through the charging
indicator to the ignition switch binding post marked “Bat.,” thence,
when the switch is turned on, through the switch to one of its binding
posts marked “Ign. Coil.” Continuing on from this point through the
ignition coil and the breaker contacts, it returns to the second switch
binding post marked “Ign. Coil,” where it passes through the switch
again. It then finally reaches the grounded negative terminal of the
battery through the grounded terminal of the switch and the car frame.
[Illustration: =Circuit Diagram of the Model O Ignition System on the
Dodge Brothers Motor Car=
Fig. 62. Wiring Diagram, North-East System--on Dodge Car]
The ignition switch is so constructed that it produces a reversal of
polarity in the distributor circuit each time the switch is turned off
and then on again. For this reason there is no necessity of making a
distinction between the two wires leading from the distributor to the
two switch binding posts marked “Ign. Coil,” because the operation of
the system cannot be affected by the transposition of these wires. With
this one exception, however, the ignition circuit connections must
always be made exactly as indicated in the diagrams, if satisfactory
operation of the system is to be maintained.
[Illustration:
CHARGING
INDICATOR
IGNITION AND
LIGHTING SWITCH
SPARK PLUGS
GROUNDED
THROUGH CASE
CONTACT-STUD LOCK NUT
STATIONARY CONTACT-STUD
MANUAL CONTROL LEVER
BREAKER-ARM
GROUND
CONNECTION
BREAKER-CAM
STARTING SWITCH AND
REVERSE CURRENT
CUT-OUT
BREAKER-CAM NUT
CONDENSER
BREAKER-
CONTACTS
IGNITION
COIL
BREAKER BOX
DISTRIBUTOR
HEAD
BATTERY
SECONDARY COIL
PRIMARY COIL
SAFETY SPARK GAP
GROUND CONNECTION
GROUNDED
THROUGH CASE
Fig. 63. North-East Distributor--Model O--Ignition]
=Ignition Distributor.= (Fig. 63).--The model O ignition distributor is
mounted on the right-hand side of the Dodge Brothers engine where it is
held rigidly in position by means of four bolts. The horizontal shaft
of the distributor is connected directly to the engine pump shaft
through a flexible coupling, and runs, therefore, at engine speed. The
vertical distributor shaft is driven from the horizontal shaft by means
of spiral gears which reduce its speed to one-half that of the engine.
The complete distributor unit consists essentially of three
self-contained assemblies: The ignition coil, the breaker box and
distributor base assembly which include the automatic spark advancing
mechanism. Each one of these three elements is so constructed as to
be readily detachable from the distributor unit independently of the
others.
=Ignition Coil.=--The ignition coil, which is contained in a separate
housing, forming part of the distributor unit, is constructed for
12 volt service and operates directly on the starting and lighting
circuit. The coil housing is attached to the distributor base by means
of four screws and serves also as a cover for the automatic advance
compartment. The high tension terminal located on the coil housing
is designed to provide a safety spark gap, as well as to act as a
binding post for the high tension cable which connects the coil to the
distributor head.
=Breaker Box and Distributor Head Assembly.= (Fig. 64).--The breaker
box and distributor head assembly is mounted in an upright position
near the center of the distributor base and is secured in place by a
large-headed screw in the vertical portion of the base. This screw
projects into the annular groove in the vertical shaft bearing sleeve,
thereby preventing the breaker box assembly from becoming detached from
the distributor base and yet at the same time permitting it to turn
freely from side to side. The short lug projecting downward from the
manual control lever on the breaker box extends into the round hole
near the middle of the distributor base and acts as a stop to limit the
travel of the breaker box.
In case it should become necessary to remove the breaker box and
distributor head assembly, the distributor head should first be
detached from the breaker box and then, with the breaker box in the
position of full retard, the exact location of the distributor rotor
should be marked accurately on the edge of the box. This mark should
be made with special care, because it has to serve as the sole guide
for the correct position of the vertical shaft when the assembly is
put back in place again on the distributor base. Moreover, while the
breaker box assembly is separated from the base, the horizontal shaft
in the base must not be turned from the position it occupied at the
time when the location of the rotor was marked. If either of these
precautions is neglected, the correct relationship between the several
moving parts of the system will be likely to be disturbed to such
an extent that the complete retiming of the distributor will become
necessary.
[Illustration:
HIGH TENSION
DISTRIBUTOR TERMINALS
DISTRIBUTOR-BRUSH
DISTRIBUTOR-HEAD
DISTRIBUTOR-ROTOR
BREAKER-CAM NUT
BREAKER-ARM
LOCK WASHERS
VERTICAL SHAFT
BREAKER-CAM
VERTICAL SHAFT
BEARING SLEEVE
STATIONARY CONTACT-STUD
SUPPORT
PRIMARY COIL
TERMINALS
GREASE CUP
COUPLING YOKE
HIGH TENSION
COIL TERMINAL
HORIZONTAL SHAFT
ADVANCE PLATE
COIL HOUSING
VERTICAL SPIRAL GEAR
ADVANCE WEIGHTS
IGNITION COIL
HORIZONTAL SPIRAL GEAR
Fig. 64. North-East Breaker-Box]
=Condenser.=--The condenser, shunted across the breaker contacts to
absorb the inductive surges that occur in the primary circuit at
each interruption, serves to intensify the effect produced in the
secondary circuit by these interruptions, and also to protect the
breaker contacts from injurious arcing. It is contained in a sealed
case which protects it against possible external injury, and is located
in the breaker box close to the breaker contacts where its maximum
effectiveness is obtained.
Being very substantially constructed, the condenser ordinarily
requires no attention. If for any reason it should become
inoperative, the best course is always to replace it with a new one,
because condenser repairs are not economically practicable. The
entire condenser unit can be easily removed, whenever desired, by
disconnecting the two condenser leads from the breaker box binding
posts, and then unscrewing the two nuts on the under side of the
breaker box that hold the condenser case in place.
=Breaker Contacts.=--The breaker arm, which carries one of the
two breaker contacts, is mounted on a pivot post from which it is
thoroughly insulated by a fiber bushing. The helical spring, which is
attached to the lug at the pivot end of the arm, holds it normally in
such a position that the breaker contacts are kept closed. But the
fiber block near the middle of the breaker arm lies in the path of the
breaker cam and is consequently struck by each lobe of the cam as the
vertical shaft revolves. Each of these blows from the cam cause the
breaker contacts to be forced apart, and thereby produce the necessary
interruptions in the primary circuit. The second contact is carried by
the stationary contact stud, which is adjustably mounted in an arched
support. With this stud properly adjusted the difference between the
contact points when they are fully separated by the cam, is twenty
thousandths of an inch (.020″).
If it should ever become necessary to renew the breaker contacts, a
complete replacement of the entire breaker arm and the contact stud
assemblies will in general be found to be the most effectual method of
handling the work. The breaker arm can be removed by simply lifting
it off its pivot bearing after its pigtail has been disconnected from
the breaker box binding post. The spring attached to the breaker arm
lug will slip off of its own accord as soon as the arm is raised
sufficiently from its normal position. After the breaker arm has been
taken off, the stationary contact stud can be removed by releasing its
lock nut and unscrewing it from its support. To replace the breaker arm
it is merely necessary to insert the lug in the spring, and then, with
the spring held taut, to push the arm firmly down upon its pivot post
until it snaps into position.
=Breaker Cam.=--The breaker cam, by which the interruptions in the
primary circuit are produced has four projections on its working
surface, so spaced that one of them strikes the breaker arm and causes
the breaker contacts to be abruptly separated each time a spark is
required. The cam is held in place on the upper end of the vertical
shaft by means of a slotted nut and set of special lock washers. It
should never be disturbed if avoidable, because its accurate setting is
absolutely essential to the correct operation of the entire system. If,
at any time, however, its position should become altered accidentally,
it must be carefully reset at once in accordance with the timing
directions given later on.
The breaker cam and the distributor rotor are both mounted on the
vertical shaft and are rotated at exactly one-half engine speed.
Accordingly, since the engine is of the usual four-cycle type requiring
two revolutions of the crank shaft for one complete cycle of operation,
the distributor rotor and breaker can make one revolution during the
completion of each full cycle of the engine.
=Distributor Head.=--The distributor head contains five high tension
terminals. The central terminal receives the current from the secondary
winding of the ignition coil and transmits it to the rotor arm by which
it is distributed to the four outer terminals. These outer terminals
are numbered 1, 2, 3, 4 respectively, corresponding to the firing order
of the engine, and are connected to the four spark plugs in accordance
with their markings. The distributor rotor in completing one full
revolution establishes contact successively between the rotor brush
and each one of these four outer distributor terminals, each contact
being made at the same moment that the primary circuit is interrupted
by the action of the breaker cam. Thus when the spark plug leads are
properly connected, the high tension current, as soon as produced in
the secondary circuit, is conducted to the spark plug of the proper
cylinder just at the moment when the gas in that particular cylinder is
ready for firing. If, therefore, the spark plug leads ever have to be
removed from the distributor head, they must always be attached again
carefully in the correct order.
=Automatic Advance Mechanism.= (Fig. 65).--Combustion does not follow
instantaneously upon the occurrence of the spark, however, because a
small time interval is always needed for the gas in the cylinder to
ignite. Consequently, unless some means are provided for offsetting
the lag between spark and combustion, the explosion of the gas could
not always be made to take place at exactly the correct moment under
varying conditions of engine speed.
[Illustration: Fig. 65. Automatic Spark Advance Mechanism--North East]
To compensate for this lag, therefore, there is incorporated in the
distributor a centrifugally actuated mechanism, which is capable of
automatically advancing or retarding the time of the spark in exact
accordance with the rate of speed at which the engine is running.
The operating characteristics of the automatic advance are accurately
proportioned to conform throughout the entire speed range with the
requirements of the engine; and in order to insure the permanence of
this relationship the device is so constructed as to be practically
nonadjustable.
=Manual Spark Control.=--Besides this automatic advance there is
also the usual manual control mechanism for changing the time of the
spark independently of the centrifugal device. This manual control
is for use principally for retarding the spark when starting or
idling the engine or for facilitating carburetor adjustments. During
normal operation of the engine, the spark lever on the steering wheel
quadrant should be advanced as far as permissible without causing the
engine to knock, and the actual regulation of the spark position be
left entirely to the automatic advance mechanism. The arrangement of
the manual control is such, provided the breaker cam is properly set,
that when the spark lever is in the position of full retard, and the
engine is running very slowly, the spark will occur in each cylinder
at 5 engine degrees after the piston has passed the upper dead center
of its compression stroke. With the spark lever advanced to the limit
of its travel on the quadrant, the spark will occur 15 degrees before
the upper dead center position has been reached by the piston on its
compression stroke.
=Timing the Distributor.=--Whenever it becomes necessary to disconnect
the distributor shaft from the engine pump shaft the exact relative
positions of the two halves of the coupling joining these two shafts,
as well as the location of the distributor rotor, should be carefully
noted and marked. This is necessary in order to make possible the
reëstablishment of the correct relations between the distributor
shaft and the pump shaft when original conditions are being restored.
Moreover, care must be taken to avoid turning the engine while the
distributor is disconnected, because the proper timing relations can
only be retained by keeping the position of the pump shaft unchanged
during this time.
Should it ever happen, however, that the distributor has been taken off
without the proper precautions having been observed, or that the timing
arrangement has been disturbed in any other fashion, it will thereupon
become necessary to make a complete readjustment of the timing
relations of the distributor and the engine. This is to be done always
after the distributor has been reconnected to the engine, the first
step being to ascertain definitely the relative position of the engine
pistons and valves. With this done, the positions of the breaker cam
and the distributor rotor are then to be reset as directed below.
Since all the parts of the engine follow a regular sequence of
operation, only the position of the piston and valves in the No. 1
cylinder need be considered in this process, and the three remaining
cylinders may be practically disregarded. There are numerous methods,
varying in their degree of accuracy, for locating the position of the
engine pistons, but the most dependable one is that of removing the
cylinder head so as to expose the pistons and valves to full view. With
the head thus removed, the engine should be cranked slowly by hand
until the No. 1 piston has risen to the top of its compression stroke
and has just started to descend on its combustion stroke. At this
moment the spark, when fully retarded, should normally occur in No. 1
cylinder.
Under circumstances where it is not convenient or desirable to remove
the cylinder head the following approximate method for determining the
location of No. 1 piston may be employed with a fair degree of success.
Open the cocks of the priming cups on all the cylinders, and crank
the engine slowly by hand until the No. 1 piston has just reached the
top of its compression stroke. This can be ascertained by holding the
thumb over the No. 1 priming cup and noting carefully the moment when
the compression ceases to increase. After locating the dead center
position of No. 1 piston in this way, turn the crank shaft a very
slight distance further until the No. 4 exhaust valve is just at the
point of closing. Under these conditions, provided the No. 4 exhaust
valve lifter is in correct adjustment, the No. 1 piston should be
approximately in the desired position of 5 engine degrees beyond dead
center.
With the No. 1 piston thus carefully set in accordance with one of the
above methods, preferably the former, bring the distributor into the
position of full retard. To do this, disconnect the manual control
attachment and turn the break-box as far as it will go in the direction
in which the vertical shaft rotates. Then after making sure that the
ignition switch is turned off, remove the distributor-head and the
distributor rotor and the breaker box, and with a broad bladed screw
driver back off the breaker cam nut until the cam is free to turn on
its shaft. Next, replace the rotor temporarily, and turn the cam slowly
until the breaker contacts just begin to open when the rotor occupies
the position where it normally makes contact with the No. 1 distributor
terminal. This adjustment can be made to the best advantage by turning
the cam forward to separate the contacts then back again slowly until
the contacts just come together, at which point the cam should be
allowed to remain.
After the proper setting has thus been obtained, remove the rotor again
and lock the cam securely in position by tightening the slotted nut
that holds it. Finally, replacing the rotor, rock the vertical shaft
backward and forward as far as the slack in the gears will permit, and
note carefully the action of the break contacts. The setting of the cam
must be so accurate that when the gears are rocked forward to take up
the slack, the contacts will be just held apart and yet when the gears
are rocked backward as far as the slack permits, the contacts will be
actually closed.
A convenient method of verifying this adjustment is to turn on the
ignition current and connect an ordinary 14 or 16 volt 2. c. p.
lamp across the two binding posts of the breaker box. The lamp thus
attached, will serve as a sensitive indicator for representing the
action of the contact-points when the vertical shaft is rocked forward
and backward to take up the slack in the gears. The moment the contacts
begin to be separated, the lamp will light; but as soon as they are
allowed to come together the lamp will at once go out again.
Should the test prove the first setting to be inaccurate, the cam
must be readjusted, and the test repeated several times if necessary
until the correct setting is finally obtained. Too much care cannot
be employed in making this adjustment, because even a very slight
inaccuracy in the setting of the cam will produce a considerably
magnified effect upon the operation of the engine. This is due to the
fact that the engine speed is twice as great as that of the vertical
shaft.
=General Care.=--Under normal operating conditions the ignition system
requires very little care aside from the usual precautions against
moisture and dirt. There are, in fact, but three points of importance
that need attention during service:
1. Lubrication.
2. Cleaning and adjustment of the breaker contacts.
3. Inspection of the wiring and the spark plugs.