ELECTRICAL
EQUIPMENT
(iii) Mark the yoke and pole shoes
(0
Bearings
so that the latter
can
be fitted
Bearings which have worn to such an
in their original positions.
extent that
thw
will
allow side move-
(iv) Unscrew the pole shoe retaining
screws by means of the wheel-
operated screwdriver.
(v) Draw the pole shoes and coils
out of the yoke and lift off the
coils.
(vi) Fit the new field coils over the
pole shoes and place them in
position inside the yoke. Take
care to ensure that the taping of
the field coils is not trapped
between the pole shoes and the
yoke.
(vii)Locate the pole shoes and field
coils by lightly tightening the
fixing screws.
Fig.
9
Tightening Pole Shoe
Retaining
Screws.
(viii) Fully tighten the screws by means
of the wheel-operated screwdriver
and lock them by caulking.
(ix)
Replace the insulation piece be-
tween
the field
coil
connections
and the yoke
(X)
Resolder the field coil connections
to the field coil terminal block and
re-rivet to the yoke.
ment of the aknature shaft must be
replaced.
T;
replace the bearing bush
in
a
commutator end bracket, proceed as
follows:-
(i) Remove the old bearing bush
form the end bracket, the bearing
should be removed by screwing
a
Q
inch tap into the bush for
a few turns and pulling out the
bush with the tap. Screw the
tap squarely into the bush to
avoid damage to the bracket.
Insert the felt ring and
aluminium
disc in the bearing housing, then
press the new bearing bush into
the end bracket (using a shoul-
dered, highly polished mandrel of
SHOULDERED
MANDREL
1
YHAND
PRESS
,
SUPPORTING BLOCK
Fig.
10
Method of fitting Porous Bronze Bearing
Bush.
the same diameter as the shaft
which is to fit
in
the bearing)
until
the bearing is flush with the
inner face of the bracket. Earlier
models, fitted with screw-cap type
lubricators, do not have a felt
ring or
aluminium
disc
in
the
bearing housing.
(ii) Porous bronze bushes must not
be opened out after fitting, or the
porosity of the bush may be
impaired. Before
fitting the new
bearing bush it should be allowed
to stand for
24
hours completely
immersed in
thin
engine oil
;
this
will
allow the pores of the bush to
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