Section G2D - Royal Enfield SPRING FRAME O.H.V. 250cc CLIPPER 1954 Workshop Maintenance Manual

ROYAL ENFIELD WORKSHOP MANUAL
Lucas A.C. Lighting-Ignition System
I. General
The Lucas A.C. Lighting-Ignition System
comprises seven main components:
(1) Alternator with magnet rotor.
(2) Bridge-connected rectifier.
(3) Ignition coil.
(4) Contact breaker unit with automatic
timing control.
(5) Lighting switch.
(6) Ignition switch.
(7) 6-volt battery.
Under normal running conditions electrical
energy in the form of rectified A.C. passes
through the battery from the alternator, the rate
of charge depending on the position of the
lighting switch. When no lights, or only the pilot
lights, are in use the alternator output is
sufficient only to supply the ignition coil and to
trickle charge the battery. When the lighting
switch is turned to the " HEAD " position the
current increases proportionately.
1 (a). Alternator Model RM13.
Model RM13 alternator (see Fig. 1) has an
outside diameter of 5 in. and is suitable for motor
cycles up to 250 c.c. having headlamp bulbs not
exceeding 30 watts. The alternator comprises two
main components, a stator and a rotor. The stator
is built up from iron laminations and carries three
pairs of series-connected coils insulated from the
laminations. The rotor has a hexagonal steel core,
each face of which carries a permanent magnet
keyed to a laminated pole tip. The pole tips are
riveted circumferentially to brass side plates,

SECTION G2d

Fitted to "250 Clipper," 1955
the assembly being cast in aluminium and
machined to give a smooth external finish. The
stator and rotor can be separated without the
need to fit magnetic keepers to the rotor poles.
As the rotor turns rapid and repeated reversals of
flux take place in the coil cores. These lines cut
through the turns of the coil and induce
alternating voltages in that coil. External
connections are taken to these coils from a
bridge-connected rectifier (see Fig. 2).
1 (b). Circuit Details
series
permanently connected across the rectifier bridge
network. The purpose of this latter pair is to
provide some degree of charging current for the
battery whenever the engine is running.
The alternator stator carries three pairs of
connected coils, one pair being
Section G2d Page 1