CLUTCH
assembly on the flywheel so that
32.
the ground lands of the gauge
plate are situated under the release
levers.
(ii)
Turn the adjusting nuts to bring
the release lever tips to contact a
short straight edge resting upon
the boss of the gauge plate.
(iii)
Having made preliminary setting,
operate the mechanism several
times in order to settle the mech-
anism. The press used for assem-
bling the cover assembly will
perform this operation.
(iv)
Carry out a check with the straight
edge and re-adjust if necessary.
Lock the adjusting nuts.
(c)
Utilising the Driven Plate Assem-
bly.
This method of setting the levers is not
highly accurate and should only be
used when the Churchill Fixture
or the Borg and Beck Gauge Plate
No. CG
192
are not available.
The draw back to this method is that
although the driven plate is produced
to close limits, it is difficult to ensure
absolute parallelism. Although the
error in the plate is small it becomes
magnified at the lever tip due to lever
ratio.
(i)
Utilising the actual flywheel, lay
the driven plate in position and
clamp the cover plate assembly
over it. The driven plate can be
centralised by the Churchill Tool
No.
20s.
72
(or similar tool).
(5)
By turning the adjusting nut adjust
the height ofthe lever ti~s to
1.895''
from tvhe flywheel fa& utilising a
suitable depth gauge.
(iii)
Operate the Clutch by using a
small press several times in order
to settle the mechanism.
(iv)
Check the height of the release
lever tips and re-adjust if neces-
sary.
(v)
Slacken the cover assembly and
turn the drive plate
90".
Reclamp
the cover assembly to the flywheel
add check the height of the release
lever tips as a safeguard against
any lack of truth in the driven
plate.
12
CONDITION
OF
CLUTCH FACINGS
The possibility of hrther use of the driving
plate assembly is sometimes raised, because
the clutch facings have a polished appear-
ance after considerable service. It is perhaps
natural to assume that a rough surface will
give a higher friction value against slipping,
but this is not correct.
Since the introduction of non-metallic faces
of the moulded asbestos type, in service, a
polished surface is a common experience,
but it must not be confused with a glazed
surface which is sometimes encountered due
to conditions discussed hereafter.
The ideal smooth polished condition will
provide
a
normal contact, but a glazed sur-
face may be due to a film or a condition
introduced, which entirely alters the fric-
tional value of the facings. These two con-
ditions might be simply illustrated by the
comparison between a polished wood and
a varnished surface. In the former the con-
tact is still made with the original material,
whereas in the latter instance, a film of dried
varnish is interposed between the contact
surfaces.
The following notes give useful information
on this subject.
(a)
After the clutch has been in use for
some little time, under perfect condi-
tions, with the clutch facings working
on a true and polished or ground
surface of correct material, without
the presence of oil, and
with
only that amount of slip which the
clutch provides for under normal con-
dition, then the surface of the facings
assumes a high polish, through which
the grain of the material can be clearly
seen. This polished facing is of a mid-
brown colour and is then in
erfect
condition, the CO-efficiency of
p
riction
and the capacity for transmitting power
is up to a very high standard.
NOTE
:
The appearance of Wound or
Woven type facings is slightly different
but similar in character.
(b)
Should oil in small quantities gain
access to the clutch in such a manner
as to come
in
contact with the clutch
facings it will burn off, due to the heat
generated by slip which occurs during
normal starting conditions. The burn-
ing off of the small amount of lubricant,
has the effect of gradually darkening
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