Thanks Nick,
The clutch fingers will push the bearing back, but obviously only as
far as their limit of movement, so they cannot result in any clearance
between the bearing and the fingers. Actually it makes sense that
there should be very light positive pressure here - it will prevent
any tendancy to "chatter".
As regards bite point, on a hydraulic clutch - which is after all self
adjusting - the bite point should be independant of clutch wear. If
one starts off with a new clutch cover and plate, as I am, then the
actual distance that the release bearing must travel forwards to
release the spring pressuure from the driven plate is probably very
little - maybe 1/4" to 3/ 8"or so?
Given the leverage of the clutch fork ( about 2 : 1 ) then the piston
in the slave cylinder only needs to move twice this distance, say 1/2"
to 3/4", a lot less than the length of the cylinder. This movement
must relate to the amount of fluid pumped from the master cylinder on
a single stroke of the clutch pedal. The clutch wear is automatically
adjusted for as it dosn't matter which 1/2" - 3/4" of the slave
cylinder bore is travelled by the piston; - near the circlip end for a
new clutch, near the bleed screw end for a worn clutch.
There don't seem to be any adjustable stops in the system: Both
pistons ( master and slave ) have a limit when they reach the end of
the bore (circlip) but in normal use I don't think that this is
intended to prevent "overthrow" of the clutch. The only thing I can
think is that the amount of travel of the pedal - master cylinder
piston - slave cylinder piston - clutch fork - and release bearing is
all designed to produce the required movement at the clutch pressure
plate.
I know that the length of the slave push rod can be critical - at
least if it is too short as the piston comes up against the circlip
before the clutch has disengaged. I guess we have all tried putting a
nut under the rounded end of the pin to adjust the length. It always
surprised me that this pin wasn't adjustable anyway!
Guy
----- Original Message -----
From <Midgetracers at aol.com>
To: <guy@weller-lakes.freeserve.co.uk>; <spridgets@autox.team.net>
Sent: 23 December 2001 22:58
Subject: Re: Clutch again
> According to Vehicle and engine technology by Heinz Heisler - ...
The return
> spring in the slave cylinder will then maintain a slight pressure on
the fork
> lever, so that the thrust bearing will always be in contact with the
release
> fingers....
>
> I would guess the slight pressure is very slight given that the
pressure
> plate fingers are pushing the thrust bearing away.
>
> I think the only way you deal with your second problem is to
establish where
> the BITE point is on the clutch. If the BITE point is right at the
top of
> the pedal then there may well be a strong possibility that the
clutch fingers
> (assuming a diaphragm spring) may be bent too far in but I think you
would
> feel the pedal getting very hard before it was fully pressed and on
the
> floor. A multi coil spring clutch couldn't I think, be damaged as
easy
> because the coils would simply bind and are I think, less prone to
damage.
> If the pedal is getting very hard - I think you said you were doing
a Ford
> conversion or something? then cut a bit off the end of the clutch
rod till it
> feels ok and goes to the floor without getting stiff and hard near
the bottom
> :-|.
>
> Maybe another lister has a better response? Paul A ??
>
> Nick
>
> >
> >
> > First question: What actually pulls the release bearing back, or
does
> > it always run lightly on the clutch cover?
> >
> > Second question: what limits how far forward the release bearing
moves
> > when you put your foot on the clutch pedal?
> > I am worried about there being too much travel, and damaging the
> > clutch springs.
> >
> > Guy
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