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[terry paget]

Chatting to chums in the pub last night I mentioned that the Omega has a concentric clutch slave cylinder. Rubbish, they said, that would need two concentric seals, hard way of doing it. I saw their point, but still reckonned it was concentric. Today, looking at my photographs, I wonder if it has any moving seals, or if it simply 'swells' when hydraulic pressure is applied.  Please enlighten me.

[sjr47]

Would think they work like brake caliper cylinders they have to be self adjusting to take up wear in clutch just like brakes therefore being single action only just moving off clutch when hydraulic pressure is released.

[terry paget]

Would think they work like brake caliper cylinders they have to be self adjusting to take up wear in clutch just like brakes therefore being single action only just moving off clutch when hydraulic pressure is released.

Good thinking, sjr47. So it cannot be a simple swelling cylinder, can it?

[Nick W]

It's concentric around the gearbox input shaft.
Doing it that way has the advantage of not needing an actuating arm and separate pivot.
It has the disadvantage of having to remove the gearbox when the thing fails. And I don't think they're that much more reliable than an external cylinder.

[terry paget]

In 1977 in a Peugeot 505 family estate I had the wretched lever arm crack and the clutch failed. I had to drive the car back from Wallingford to Midsomer Norton - 70 miles - carrying 6 elderly relations without a clutch, pulling away on the starter.

My original question was - how do you make a concentric clutch slave cylinder? If it is a piston in a cylinder, it will need two seals, whre one would have done in a simple cylinder. 

[aaronjb]

It's a piston with a hole punched through it - so it's a donut with twice as many seals..

Patent drawings: http://www.google.com/patents/US6374724

[05omegav6]

First imagined in 1983 apparently 

[Andy H]

It's a piston with a hole punched through it - so it's a donut with twice as many seals..

Patent drawings: http://www.google.com/patents/US6374724

That patent appears to show a design that allows one seal to bridge the gap between inner and outer cylinder walls.

The concentric slave cylinder is an elegant design solution. It has one moving part, is self adjusting and avoids applying sideways loads to the release bearing.

[terry paget]

Thank you gentlemen, and congratulations. My friends were right, it has two seals. I was right, the slave cylinder is indeed concentric. It is a recent invention, and quite tricky to manufacture.

[terry paget]

It's a piston with a hole punched through it - so it's a donut with twice as many seals..

Patent drawings: http://www.google.com/patents/US6374724

That patent appears to show a design that allows one seal to bridge the gap between inner and outer cylinder walls.

The concentric slave cylinder is an elegant design solution. It has one moving part, is self adjusting and avoids applying sideways loads to the release bearing.

Thanks Andy. I have read the patent a couple of times, and studied the drawings, but cannot decide whether there are two seals, or one seal spanning both sides of the narrow annular chamber. One would certainly be more elegant.

[Marks DTM Calib]

On the Omega setup there is two hydraulic seals plus a bellows type dust seal, cant see them being that hard to manufacture.

And failure of them is all but unheard.