Workshop
Manual
Rolls- Royce Silver Shadow
B
Bentley
T
Series
Chapter
M
FIG. MI3 CORRECT FITTING OF BRUSH SPRING
1
Brush
box
2
Brush
3
Normal working position of spring
4
Anchor post
A
CORRECT (Spring tensioning half-turn)
B
INCORRECT (Spring tensioning full-turn)
FIG.
MI4
CHECKING BRUSHGEAR INSULATION
1
110 volt AC mains
2
15 watt lamp
3
Insulated brush box
2.
If the armature shows signs of fouling the
pole-shoes, worn bearings or an untrue armature
shaft are indicated. Check the armature between
centres for eccentricity; renew if necessary.
If the arrnature is serviceable, the bearings must
be renewed (see Bearings
-
To renew).
3.
Check the insulation of each armature segment
with a
110 Volt A.C. 15 Watt test lamp connected
between the commutator segments and the shaft
(see
Fig.
M15).
The lamp will light if the
insulation is not satisfactory.
4.
Check the armature for short circuit in the
windings using
'
Growler' equipment and following
the manufacturer's instructions.
Field coils-To remove
1.
Using a wheel operated screwdriver, unscrew
and remove the four screws securing the pole-shoes.
2.
Remove the insulation piece fitted to prevent
intercoil connectors from contacting the yoke.
3.
Draw out the pole-shoes and coils from the
yoke, and lift off the coils.
Field coils-To fit
1.
Fit the new field coils over the pole-shoes and
place them in position inside the yoke. Ensure that
the taping of the field coils is not trapped between
the mating surfaces of the pole-shoes and yoke.
2.
Locate the pole-shoes and field coils by
lightly tightening the retaining screws and fit the
insulation piece between the field coil connections
and the yoke.
3.
Hold the pole piece in position by means of a
pole-shoe expander or
mandrel, then tighten the
screw, using the wheel operated screwdriver.
Field coils-To test
To test the continuity of the field coils, proceed
as follows.
1.
Connect a 12 Volt test lamp and battery
between the terminal on the yoke and each brush;
ensure that the brushes and their flexible connec-
tors are clear of the yoke. If the lamp fails to
illuminate, an open circuit in the field coil is
indicated and the coil must be renewed.
To test the insulation of the field coils proceed
as follows.
(see
Fig.
M16).
1.
Connect a 110 Volt A.C. test lamp between
the terminal post and a clean part of the yoke. If
the test lamp illuminates it indicates that the field
coils are earthed to the yoke and that the field
coils must be renewed.
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