MG Magnette KA Instruction Manual page 98

T O P SPEED
TOP SPEED TOP GEAR
ACTUATING
OUTER
R I
NG
INNER
ENGAGING TOP
SPEED
RING
/
LUG
/
CONE
lllustration
L.-Complete set of brake-drums and epicyclic gears. T h e parts have been slightly
strung out t o show the internal gears, the top speed cone engagement w i t h the third speed drum,
and the manner in which the top speed is actuated by its steel balls, forcing the top speed inner ring
forward under the action of the helical ball tracks, and the top speed actuating outer ring.
Having thus described the details o f t h e operation o f gear selection and the
manner in which t h e bands are caused t o contract, lllustration
K
should now be
studied. The next point is t o see how the gears are built up i n t o a unit on t h e
in-put and out-put shafts, and how t h e various gears are operated. lllustration
K
shows a gearbox partially dismantled. The f r o n t end cover o f t h e gearbox has
been removed, and is shown on t h e right-hand side o f t h e illustration. This forms
a housing for t h e o i l pump, which can also be seen complete w i t h its housing. The
f r o n t end o f t h e in-put shaft is provided w i t h a cam-shaped extension o r eccentric
which fits inside t h e pump plunger extension, so that w i t h every revolution o f
the engine a plunger which fits i n t o an oscillating housing is caused t o rise and fall.
This sucks up o i l through a small hole in the body o f t h e gearbox, and as t h e pump
oscillates and closes up the suction hole, t h e downward stroke o f t h e pump plunger
forces oil up through the hollow plunger i n t o t h e hollow gearshaft, and is so
distributed throughout the whole inner works o f t h e box.
After t h e f r o n t end cover has been removed it is possible t o w i t h d r a w t h e
complete train o f gears and shafts as shown, presuming that t h e box has been removed
f r o m t h e chassis. The brake-drums can be clearly seen, which operate through
t h e action o f the brake bands o f the reverse, Ist, 2nd and 3rd speed gears. The
t o p speed, however, i s differently operated. O n the left-hand corner o f lllustration
K
t h e mechanism o f the t o p speed can be seen. There
is,
in point o f fact, an actual
conical engagement o f t h e t o p speed cone and t h e Ferodo facing o f t h e inside o f the
3rd speed brake-drum. This is n o t brought about directly by spring pressure, b u t
by the action o f the t o p speed actuating outer ring, which is held stationary up
against t h e f r o n t end cover by means o f three set screws and the steel balls which
are positioned in helical slots.
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