PIPER
SENECA
II
SERVICE
MANUAL
11-26. STARTING MOTORS.
11-27. DESCRIPTION. The starting
motor
consists
of
five major components:
the
commutator
end head
assembly, the brush set
and
plate assembly,
the
frame and field assembly,
the
armature, and the drive end
head assembly. (Refer
to
Figure 11-15
.)
11-28.
OPERATION.
When
the
starting circuit is energized, battery current is applied
to
the
starting
motor
terminal.
Current
flows
through
the field coils creating a strong magnetic field.
At
the
same time,
current flows through the brushes
to
the
commutator
through
the
armature windings
to
ground. The
magnetic force created in
the
armature combined
with
that
created in
the
field windings begins
to
turn
the
armature.
11-29. MAINTENANCE. The starting circuit should be inspected at regular intervals; the frequency
of
which should be determined
by
the
amount
of
service and
the
condition under which the aircraft is
operated.
It
is recommended
that
such inspection be made
at
each 100 hours and include
the
following:
a.
The
battery
should be checked with a
hydrometer
to
be sure
it
is
fully charged and filled
to
the
proper
level with approved water. A load test should be made
to
determine
battery
condition.
If
dirt and
corrosion have accumulated
on
the
battery,
it
should be cleaned
with
a solution
of
baking soda and water.
Be sure
none
of
the solution enters
the
battery
cells.
b. The starting circuit wiring should be inspected
to
be
sure
that
all connections are clean and tight
and
that
the
insulation
is
sound. A voltage loss test should
be
made
to
locate
any
high resistance
connections
that
would affect starting
motor
efficiency. This test
is
made with a low reading voltmeter
while cranking
the
engine
or
at
approximately 100 amperes and the following limits should be used:
1.
Voltage loss from insulated
battery
post
to
starting
motor
terminal - 0.3-volt maximum.
2. Voltage loss from
battery
ground post
to
starter
frame - 0.1-volt maximum.
NOTE
If
voltage loss is greater
than
the
above limits, additional tests
should be made over each
part
of
the
circuit
to
locate the high
resistance connections.
NOTE
If a solderless terminal on
an
aluminum cable
is
loose, corroded
or
otherwise unsatisfactory, it
is
recommended
that
the complete cable
assembly
be
replaced instead
of
replacing
or
repairing the solderless
terminal.
Should replacement of the complete assembly not be practical,
it
is
permissable to replace the aluminum cable assembly with a copper
cable assembly which
is
two sizes smaller (Ex: an AL- I Aluminum
Cable Assembly
is
replaced with an
AN-3
copper cable assembly).
The new cable should be installed in accordance with AC-43- l 3-2A.
c.
No lubrication
is
required
on
the
starting
motor
except
at
the
time
of
overhaul. Soak new
absorbent bronze bearings in SAE
20
oil before installation. Saturate the felt oiling pad in
the
commutator
end head
with
SAE 20 oil. Allow excess oil
to
drain
out
before installing end head
on
motor.
Put
a light
film
of
Lubriplate
777
on
the
drive end
of
the
armature shaft before and
after
installing
the
drive end head.
Revised:
3/16/81
2G16
ELECTRICAL
SYSTEM
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