Tsn BneKrNG
Sysrnu.
57
CHAPTER
VI
The
Braking
System
General
Description-Possible V
ariations-Adjustments-Adjustment
of Hand
Brake-Adjustment
of Seruo-I.ubrication-Bleei,ing
the
Hydraulic System-Hydrawlic
Master Cylinder.
Generat Description.
The
Bentley four-wheel
braking
system
is
of the
Servo assisted
type,
and comprises a
mechanically driven
servo
motor
of
the dry
disc-brake
type,
which
is
equally effective for
either forward
or
backward
movement
of the
car. Further,
even should
the servo be
out of
action,
the
rod
operated
rear
brakes
are still directly
coupled
to
the
pedal.
Pressure on the
pedal
applies the rear brakes
direct
in
the usual
manner,
and also
engages the servo, but
the front brakes
which are
of
the
hydraulically
operated
type are actuated
entirely by the
servo
acting through the
medium of
a
balance lever and hydraulic
master
cylinder.
The
servo effect is
distributed between
the front and
rear
brakes,
being
added therefore
to the direct pedal
effect
in
the case of
the
rear brakes.
With the leverages provided,
this results in about
55
per
cent. of the
total braking
being
imposed
on
the front
wheels, which
allows for the
fact that greater
weight is
thrown
upon
the front wheels
during
braking.
The
proportioning
of the servo
pull
to the front and rear brakes
respectively is
effected by a balancing
lever. A separate
equaliser
is
provided
for
the two rea.r
brakes, which,
with the
hydraulic
operation
of
the frqpt
brakes,
ensures
even
braking
on either
side
of
the car.
The
hand
brake
lever
operates the rear brakes
only and uses
the
same linkage
as the foot
pedal.
A diagrammatic
representation
of the whole system is
shown
in
Fig.
17.
A
pull
rod
(1,
Fig. l7), operated by
the
pedal, is
coupled
to a
lever
(2),
on
the servo
motor shaft,
the
motor
itself (3)
being mounted
on the
off-side
of
the
gearbox,
and
driven
at approximately.one-tenth
of
the
propeller
shaft speed.
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