Rolls-Royce Corniche - Brush Gear Insulation-To Check; Brush Springs-To Service; Brushes-To Remove, to Fit; Tube Dimensions and Checking Brush Spring Pressure

Rolls-Rovce Silver Shadow B Bentley T Series
Workshop Manual
Chapter M
are true to centre, then set up the armature between
the centres on a lathe and polish the commutator
with fine glass paper; on no account should emery
cloth or a similar abrasive be used.
5.
If the commutator needs to be skimmed, the
minimum diameter to which it may be reduced is
39,O mm. (1.545 in.). After skimming, the
commutator surface should be finally polished with
very fine glass paper, on no account should emery
cloth or a similar abrasive be used.
The insulation segments on the commutator must
not be undercut.
Brushes-To remove
FIG. Mll TUBE DIMENSIONS
1. There are four brushes in the starter motor,
two are connected to the brush boxes and two
A 12,70mm.(O.O50in.)~ B 7,62cm.(3;0in.)
connected to the free ends of the field coils.
Carefully prise open the field connections with a
screwdriver and use a soldering iron to remove
the solder from the connections. Remove the
brushes.
A
Brushes-To fit
Reverse the procedure given for removal. When
fitting a new brush ensure that it is free in its
brush box, noting the following point.
1.
New brushes are pre-formed and do not
require bedding in.
Brush springs-To service
1.
Check the brush spring pressure using a
pull-type spring gauge and without the brush in the
brush box
(see Fig. M12). The spring pressure
recorded
by the spring gauge at the moment the
spring pressure is relieved from the brush box
should be
1 ,l kg minimum (42 oz).
2.
If new brush springs are required ensure that
they are correctly fitted
(see Fig. hfl3). If the
springs are incorrectly fitted there will be
excessive pressure on the brushes resulting in
premature brush wear and damage to the commutator.
Brush gear insulation-To check
Check the brushgear, using a 110 volt A.C. 15 watt
test lamp connected between each of the two
insulated brushboxes in turn and a clean unpainted
part of the bracket
(see Fig. M14). The lamp should
not illuminate,
FIG. MI2 CHECKING BRUSH SPRING PRESSURE
1 Commutator end bracket
2 Spring gauge
3 Anchor post
A Pressure reading
Armature-To check
1.
If the solder on the armature has 'thrown' or
the cbnductors have lifted from the commutator
segments, the armature should be discarded.
This also indicates possible shorting and
over-
speeding of the motor and the operation of the
roller clutch drive should be checked as described
in Roller clutch drive
- To check.