Starter Motors; Run-Off Helix Drive - Perkins 4.108 Workshop Manual

ELECTRICAL EQUIPMENT -0.6
remove the link from between the terminals and
restore the orig inal connections.
STARTER MOTORS
General
The following information is concerned with the M45G
starter motor. Two types of drive are available and both
are covered fully in the following section. Should in-
formation be required in connection with any other type
of starter motor then the relevant manufacturer should
be contacted.
STARTER MOTORS
Run-off Helix Drive (See Fig. 0.4)
1. Description-Model M45G Type RF 17
This electric starter motor is a four-pole four-brush
machine having an extended shaft which carries the
engagement gear, or starter drive as it is more
generally known.
The starter motor is of a similar construction to the
dynamo except that heavier copper wire is used in the
construction of the armature and field coils. The field
coils are series-parallel connected between the field
terminal and the insulated pair of brushes.
The armature has 23 winding slots. The drive portion
incorporates a special overload protective device
known as the Run-off Helix.
2. Routine Maintenance
(a) The starter motor requires no routine maintenance
beyond the occasional inspection of the electrical
connection which must be clean and tight, the
brush gear, and the commutator.
(b) After the starter motor has been in service for
some time remove the starter motor from the
engine and submit it to a thorough bench in-
spection.
1. Check that the brushes move freely in their holders
by holding back the brush springs and pulling
05
BRUSH
gently on the flexible connectors (Refer to Fig.
0.5). If movement is sluggish, remove the brush
from its holder and clean its sides with a fluffless
petrol moistened cloth. Replace the brush in its
original position. Brushes which are worn to less
than 9/16 in (14 mm) long must be renewed.
NOTE: This is the length when half the available
wearing length has worn away. The time taken to
reach this stage normally extends well beyond that
to reach the point of major engine overhaul. After
this time, the rate of wear accelerates due to re-
ducing spring pressure.
2. Check the tension of the brush springs using a
spring scale. (Refer to Fig. 0.6). The minimum
tension is 43 ozf (0,61 kgf). New springs should
be fitted if the tension is low.
MODEL M45G TYPE RF 17
BRUSHES
COMMUTATOR END COVER BAND COVER BAND
BRACKET NUT
SEARING BUSH
04
FIXED SLEEVE
PINION RESTRAINING SPRING
FIELD COILS
THRUST WASHERS
DRIVE END
BRACKET
....... , .. j
I
BEARING BUSH
~
PINION & SLEEVE MAIN SPRING SHAFT NUT