Hydraulic clutch, how does it work ??

In the past I have dealt with cable release versions but never one of these.
question is how do they work ? I assume the principle is that the pedal
transmits force to the fluid reservoir which then actuates the clutch. What
is the line of connection from the pedal and why use it if there is no
assistance from the engine as per brake system ??

Ta John H

110 Tdi 98

--


" ..... it is the provenence of knowledge to speak, and it is the privelage
of wisdom to listen"

"Hirsty's" <[email protected]> wrote in message
news:[email protected]...
> In the past I have dealt with cable release versions but never one of
these.
> question is how do they work ? I assume the principle is that the pedal
> transmits force to the fluid reservoir which then actuates the clutch.
What
> is the line of connection from the pedal

*Usually some sort of rod linkage to the cylinder.

and why use it if there is no
> assistance from the engine as per brake system ??

*Because you can get a mechanical advantage by making one cylinder bigger
than the other. ( I should perhaps more correctly say something like the
swept cylinder volume of one is bigger than the other) So then it's much
easier to push the clutch in.

I was amazed recently when changing a clutch cable on a Rover 1800 - the
actuating arm only moves an inch or so but requires all my strength to move
it by hand. I dread to think how much force is required for the larger landy
ones!

TonyB
>

Hirsty's wrote:

> In the past I have dealt with cable release versions but never one of
> these. question is how do they work ? I assume the principle is that the
> pedal transmits force to the fluid reservoir which then actuates the
> clutch. What is the line of connection from the pedal and why use it if
> there is no assistance from the engine as per brake system ??
>
> Ta John H
>

The pedal acts on the master cylinder which in turn pushes hydraulic fluid
through a series of pipes to the slave cylinder which actuates the clutch
release.

The main thing they've got going for them over a cable clutch is the
mechanical advantage that can be had from a hydraulic system over a direct
physical connection.

Additionally you don't end up with nasties like the bowden wire rusting and
siezing at a nasty time and then having to rerun the entire wire.

It's just a different way of doing things which happens to allow for a bit
more flexibility in where they clutch is located and allows for the clutch
to be made lighter than via a direct mechanical connection.

P.

Hirsty's wrote:

> In the past I have dealt with cable release versions but never one of
> these. question is how do they work ? I assume the principle is that the
> pedal transmits force to the fluid reservoir which then actuates the
> clutch. What is the line of connection from the pedal and why use it if
> there is no assistance from the engine as per brake system ??
>
> Ta John H
>
> 110 Tdi 98
>
> --
>
>
> " ..... it is the provenence of knowledge to speak, and it is the
> privelage of wisdom to listen"

Hydraulic clutch operation is used for the same reasons that hydraulic
braking was used for at least fifty years before any engine assistance was
applied (and probably still is in some cases) - because hydraulic operation
is virtually friction free, allows complete freedom of linkage design, and
needs no special design to allow for movement between the pedal and the
place of operation. The connection between the master cylinder operated by
the pedal and the slave cylinder on the flywheel housing is by a steel pipe
and a short flexible high pressure hose.
Mechanical linkage or cable clutch operation, by comparison constrains the
design quite severely (for example makes change from right to left hand
drive more difficult) and has a lot more friction, and tends to produce
lost motion due to wear.
JD