Lotus Elan

Burton concentric clutch slave cylinder: fitting ?

PostPost by: nmauduit » Tue Oct 09, 2018 11:47 am

Thank you Rohan for this thorough article, I will keep it for our long winter nights. I only had a quick glance but noted they appear to make a specific point of clutch wear for the feel (moving operating point meaning a different angle and leverage hence pedal effort), with all sorts of automated shims to maintain the operating point stable... I don't care much about pedal feel as long as I still can operate the thing ;)
Then remains the "hydraulic release" impact on lifetime with plate wear : I believe the system I have takes reasonable care of this (std disclaimer : if I set it correctly...) as the spring motion after wear is taken up by the light spring inside the slave to maintain contact with the ring (i.e. less fluid in the slave at rest then) - just like one would adjust manually the rod and clevis on the original setup. As long as there is enough free travel with the slave to accomodate bearing motion under plate wear, I fail to see a significant difference between fork and annular clutch release from that perspective.
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PostPost by: rgh0 » Tue Oct 09, 2018 12:06 pm

My 1999 Toyota Landcruiser has a self adjusting clutch and no adjustment on the slave cylinder. i have done 403,000 kms with the original clutch and release bearing so it works and the release load and feel and travel has remained constant. The car weighs 3 tonnes when loaded and I often pull my Elan on a trailer and with a high torque 4.5 litre engine it puts a lot of load on the clutch!

My fear is that without a self adjusting clutch you will run into problems with the concentric slave cylinder travel as the clutch wears. When and how the problems arise will depend on the installation setup dimension and how much clutch wear overtime.

The only problem I experienced with the self adjusting clutch on my Landcruiser is that for a period between 300,000 km and 350,000 kms if I went to maximum revs before changing gears something happened to the self adjusting mechanism and clutch travel to release increased for the next 4 or 5 applications until it adjusted itself again back to normal. This only happened for a while and has now gone away again.

Just need to be aware of limitations of new technology you may adopt and its implications

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PostPost by: prezoom » Tue Oct 09, 2018 5:15 pm

When I did my Zetec conversion to the Plus2, I opted to use the concentric release bearing system from the Contour/Mondaeo, because that was the pressure plate I chose to use with the Fidanza aluminum Zetec flywheel. The release bearing is spring loaded against the fingers. Thus, the release bearing must be pushed back a sufficient distance when assembled, in order to move the fingers enough to release the driven disc. Rather than trying to make an adequate spacer arrangement to mount the release bearing assembly to the front of the bell housing, I machined a new bearing retainer, replacing the original one, placing the release bearing assembly forward to give the bearing enough movement to release the clutch. Unfortunately, I missed the mark the first time, as when the pedal was fully depressed, it bottomed the release bearing against its stop before moving the fingers enough to completely release the clutch. Engine back out........ugh, and a spacer was inserted to increase the travel. That worked, and now the release point is about where I want it in the pedal travel. After thinking about it, I came to the realization that I could have made the spacer even thicker, so as to take care of driven disc wear. Only additional fluid would possibly be needed, as the position of the release bearing changed as the disc became thinner. This is because as the bearing moves forward, the fluid capacity behind the bearing increases, reducing the fluid level in the master cylinder, making the fluid the only adjustable item.

I was concerned about the amount of pressure the spring exerted against the release bearing initially, but as these are all standard parts in the clutch system in the Contour/Mondaeo, I convinced myself that Ford must have designed it that way to make for a minimal maintenance system. With about 3000 miles on the clock, everything is working as designed. Only time will tell.

One of the reasons I went with this system in the first place was, it used all standard parts, and the bonus was I was able to remove the external slave cylinder, including the ring on the side of the bell housing, allowing the exhaust header to be raised above the bottom of the chassis, and it also gave a bunch more room for the much larger diameter pipes for the 4-2-1 system. Now, the only part of the exhaust that is below the chassis is where the pipe drops below the chassis at the center line behind the gearbox. The rear header support bracket is now mounted to a stud welded to the head of the bottom bolt that holds the tail housing to the center section of the gearbox,
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1964 Sabra GT
1964 Elva Mk4T Coupe (awaiting restoration)
1965 Ford Falcon Ranchero, 302,AOD,9",rack and pinion,disc,etc,etc,etc
1954 Nash Healey LeMans Coupe

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PostPost by: Panda » Wed Oct 10, 2018 5:42 am

The Saab concentric slave cylinder which first appeared in the late seventies simply relied on having sufficient travel to avoid the release bearing contacting the cylinder as the clutch plate developed wear. The pressure plate was a very simple common design of the era. I worked on them for 24 years!
I have had one in my last 3 Elans without any problems. I made up a plate to bolt onto the original release lever opening with 2 holes, one for the supply hose and one for the bleed hose fitting. Fairly close to the exhaust but works fine with my current race car. Bleeding never been an issue using a vacuum bleeder.
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