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to
eng ine speed. Automation
spark advance
is
then reppresented by a
diagram
(see
Fig
.
122)
which shows the degrees of
advance
of the cam
with
respect to
the speed of the distributor
shaft.
CONTACT BREAKER
(see
Fig. 123)
The duty of the contact breaker
is
to
break at
intervals the
low
voltage current which flows
in
the
primary
winding of the ignition coil. Contact
breaker
consists
of one plate (1), which is
screwed to distributor body and which compri-
ses the
fo
llowing
parts;
-
Fixed contact print holder
(2)
which can ro-
tate for some degrees around pin (5) solid
with plate and it
is
secured to plate by means
of screw
(3)
in the most suitable position
for obtaining a correct breaker
gap.
breaker
arm
(4)
provided with movable
contact
point, pivoted on pin
(5)
and com-
prising flat spring
(6) which
secures contacts
pressure and adherence
of
felt pad
(7)
to
the two-nosed
cam (8). Number of cam no-
ses
is
always
the
same as the
number
of
cylinders.
When contacts
are closed,
the
low
voltage
current of the battery
flows thru ignition
coil
primary winding and arrives to
terminal
(9).
From
here
the current runs thru flat spring
(6)
and goes to ground Ihru contact point holder
(2) and distributor body.
CONDENSOR
The
condensor,
which
is inserted in parallel
with contact
breaker
points,
has the duty to ma-
ke
sharper
the current
break and in
the
mean-
time
10
damp
the strong sparking
originated at
points
by the
break of
primary winding.
The
condensor consists
of two
tin
foil stripes, insu-
lated
by interpolation
of paper stripes. The
lot
is
then
rolled up,
dipped
into special
insulating
oil
and sealed in a casing. One
of
the tin foil
stripes
is
internally connected
to the metalJic
casing, while
the
other
stripe
is
connected
to
an insulated
terminal.
Fig. 123
1.
Plate
-
2.
Fixed
contact point holder
-
3.
Point holder
securing screw -
4.
Breaker arm -
5.
Breaker arm pin
-
6. Flat spring
-
7.
Felt
pad -
8. Cam -
9. Terminal for
con-
nection
to
coil.
DISTRIBUTOR CAP AND ROTOR
Distributor cap and rotor can be described
together because they form the high voltage
current
distribution system
.
Distributor cap and
rotor are both in molded bakelite and
include
some metal parts which
form
separate
circuits.
One of these circuits, and exactly the
central
circuit, transfers
the
high voltage
current
recei-
ved from the
coil
to the carbon brush which,
owing to the pressure af a spring, is constantly
in
contact
with the
inner
end
of
the rotor meta!
brush.
Rotor is positioned at top
of
cam spindle, thus
rotating at the same speed
of
the distributor
shaft. When
rotor
is in rotation. the
outer
end
of
the metal
brush (contact
piece) skims
one
after the other the metal sectors
in
distributor
cap,
thus transmitting the high
voltage current
pulses
coming from ignition
coil.
After that, the
current
flows thru the two
peri
ph erica I circuits
of
cap until reaching
outlets
in which are in-
serted the
cables
required to
convey the current
to
the
spark plugs. Ignition spark
will
take
pla-
ce
between plug points. The number
of
the
cylinder to which
each
cable
must be
connec-
ted
is marked
on the
distributor
cap.
SPARK
PLUGS
Spark
plugs
fitted
on
this
machine are
MAREL-
LI
CW
225
LVT
type
or
BOSCH
W
225 T 2
type.
-105
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