Fig. 59. Exploded view of dynamo
.
B (3) Dynamo – Dismantling
(a) Bend back the tag on the washer (B, Fig. 59)
locking the screw (C) securing the driving gear (D)
and remove the screw. Withdraw the gear from the
dynamo shaft by carefully levering it off by means of
an extractor. Remove the key (E) from the shaft.
(b) Remove the cover band (F), hold back the brush
spring and lift the brushes (G) from their holders.
(c) Take the screw (H), with spring washer, from the
centre of the black moulded end cap (I). Draw the
cap away from the end bracket, take off nuts (J) and
spring washers, and lift the connections off the
terminals.
(d) Unscrew and remove from the driving end
bracket, the two bolts (K) securing the driving end
bracket (O) and commutator end bracket (Q) to the
dynamo yoke (S). Hold the nuts (L) at the
commutator end whilst unscrewing the bolts, and
take care not to lose the nuts.
(e) Draw the armature (N) complete with end bracket
(O) out of the yoke.
(f) Unscrew the nut (M) from the driving end of the
dynamo shaft and remove the armature from the end
bracket, using a hide or wooden mallet.
(g) Take out the screw (P0 securing the green field
coil lead with the yellow sleeve to commutator end
bracket and remove the end bracket (O), withdrawing
the connectors through the slot in the insulating plate.
B (4) Dynamo Brushes.
Test if brushes are sticking. Clean with petrol and if
necessary ease the sides by lightly polishing on a
smooth file. Replace brushes in their original
positions.
Test the brush springs with a spring scale (Fig. 60) if
available. The correct tension is 10-15ozs.
Fit a new spring if tension is low. If the brushes are
worn so that the flexible is exposed on the running
face, new brushes must be fitted. Brushes are pre-
formed so that bedding to the commutator is
unnecessary.
Fig. 60. Method of measuring brush spring tension.
Dynamo - Commutator
A commutator in good condition will be smooth and
free from pits or burned spots. Clean the
commutator with a petrol moistened cloth. If this is
ineffective, carefully polish with a strip of very fine
glass paper while rotating the armature. To remedy
a badly worn commutator, mount the armature with
or without the drive end bracket in a lathe, rotate at
high speed and take a light cut with a very sharp tool.
Do not remove more metal than is necessary. Polish
the commutator with very fine glass paper.
39
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