Lotus Elan

Burton concentric clutch slave cylinder: fitting ?

PostPost by: Frogelan » Fri Sep 28, 2018 3:24 am

In October / November I will start assembly of my rolling chassis after a 12 month parts hunt and a rebuilt engine and a new gearbox (by a local firm, First Motion and with the help of parts from Mike Duff from the Forum). The car is a S2 and the chassis is a Elan S2 26R Lotus Replacement type (Gartrac). I have no bodyshell so far and have not started offering the parts up for testing.

I plan to fit a Burton supplied concentric clutch slave cylinder (CCSC) and wondered if folks here had any suitable tips or feedback on 2 main questions:

(1) There are 2 Aeroquip type hoses for the operation and external bleeding. Both will run from inside the gearbox bellhousing upwards through a hole that I need to make in the top of the bellhousing (a vintage aluminium one that is surprisingly light and fragile).

Does anyone have a suggestion for where this would be best located to allow a free run without it rubbing against the chassis or the bellhousing itself ?

(2) Obviously I realise that once the CCSC is finally installed it needs to be done up tightly. Are there any tips on the best way to identify the amount by which the spacer has to be machined ?

[I have in mind making a bench type pedal box and then perhaps using a cheapo inspection camera from the original lever hole to have a look inside]

Many thanks !
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PostPost by: alan.barker » Fri Sep 28, 2018 7:18 am

I suggest you look at past posts and about the orientation so Bleeding will not be a problem :wink:
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PostPost by: vxah » Fri Sep 28, 2018 7:35 am

Once you have your flywheel, disc and cover fitted up to the engine it should be easy to use a straight edge and vernier to measure the distance from cylinder block bell housing face to the cover fingers. Release the cover bolts a little to simulate disc wear so the fingers move back and that is the minimum distance that your bearing bust go back for the clutch to work.
You can then use the straight edge on the bell housing face to then measure back on the input shaft to work things out? I have not seen the Burton set up but made mine using a Vauxhall Astra slave cylinder, I guess the Burton system is fairly straight forward to fit up?
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PostPost by: jimj » Fri Sep 28, 2018 7:45 am

As you know, my concentric clutch unexpectedly failed recently. It was the rear seal and a mystery as to why. When fitting the new one, just to be sure, the engine and gearbox were mated out of the car and a temporary clutch fluid line connected to the master cylinder and the pedal operated while the slave cylinder operation was observed with an inspection camera.
The bleed line comes out of a hole near the underside so you can get at it. Having it come out of the top just created problems. Ordinary copper line is used.
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PostPost by: Andy8421 » Fri Sep 28, 2018 8:07 am

I have been considering a concentric clutch cylinder - but I have a question for those who have used them.

On the standard Lotus/Ford item, there is a substantial return spring that pulls the release bearing away from the fingers on the pressure plate when the clutch is released. The concentric versions don't seem to have this - and therefore the bearing must remain in constant contact - do I have this right?
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PostPost by: nmauduit » Fri Sep 28, 2018 8:24 am

Andy8421 wrote:I have been considering a concentric clutch cylinder - but I have a question for those who have used them.

On the standard Lotus/Ford item, there is a substantial return spring that pulls the release bearing away from the fingers on the pressure plate when the clutch is released. The concentric versions don't seem to have this - and therefore the bearing must remain in constant contact - do I have this right?


there is a light spring inside the slave of mine (Saab 900), which pushes the bearing in light contact with the fingers (bearing being intended to work so).
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PostPost by: alan.barker » Fri Sep 28, 2018 9:02 am

jimj wrote:As you know, my concentric clutch unexpectedly failed recently. It was the rear seal and a mystery as to why. When fitting the new one, just to be sure, the engine and gearbox were mated out of the car and a temporary clutch fluid line connected to the master cylinder and the pedal operated while the slave cylinder operation was observed with an inspection camera.
The bleed line comes out of a hole near the underside so you can get at it. Having it come out of the top just created problems. Ordinary copper line is used.
Jim

Instead of copper line i would use "Kunifer" :wink:
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PostPost by: alan.barker » Fri Sep 28, 2018 9:02 am

jimj wrote:As you know, my concentric clutch unexpectedly failed recently. It was the rear seal and a mystery as to why. When fitting the new one, just to be sure, the engine and gearbox were mated out of the car and a temporary clutch fluid line connected to the master cylinder and the pedal operated while the slave cylinder operation was observed with an inspection camera.
The bleed line comes out of a hole near the underside so you can get at it. Having it come out of the top just created problems. Ordinary copper line is used.
Jim

Instead of copper line i would use "Kunifer" :wink:
Alan
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PostPost by: nmauduit » Fri Sep 28, 2018 10:32 am

alan.barker wrote:
jimj wrote:As you know, my concentric clutch unexpectedly failed recently. It was the rear seal and a mystery as to why. When fitting the new one, just to be sure, the engine and gearbox were mated out of the car and a temporary clutch fluid line connected to the master cylinder and the pedal operated while the slave cylinder operation was observed with an inspection camera.
The bleed line comes out of a hole near the underside so you can get at it. Having it come out of the top just created problems. Ordinary copper line is used.
Jim

Instead of copper line i would use "Kunifer" :wink:
Alan


I've made stainless steel lines for my car.
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PostPost by: Chancer » Fri Sep 28, 2018 12:11 pm

jimj wrote:The bleed line comes out of a hole near the underside so you can get at it. Having it come out of the top just created problems. Ordinary copper line is used.
Jim


That is just asking for problems, air rises and there is a good reason why bleed fittings are always at the top of an installed hydraulic cylinder.

Unless there is some internal gallery that connects the bleed port to the top of the cylinder but unlikely as you would need a rapid bleeding action to displace any air.

Ahhh, I think I realise what you are saying, bleed line comes out the top of the cylinder and then down to the exit hole in the bellhousing, my bad
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PostPost by: Frogelan » Fri Sep 28, 2018 1:50 pm

Thanks chaps for the very useful replies. I think I now understand how to do the measurements.

With respect to the flexible or non-flexible pipes, I think that an (upwards) pipe solution within the bellhousing makes sense but this should not anywhere near the exhaust (the main reason for not having the standard system).

I will come back with some photos in November (as I am in France and the car is in GB!).

PS: I have read through most of the threads before posting but additional suggestions / ideas (thanks VHAX and Nicolas Mauduit) are always useful and tease extra information which is always useful!
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PostPost by: nmauduit » Fri Sep 28, 2018 2:26 pm

Chancer wrote:Ahhh, I think I realise what you are saying, bleed line comes out the top of the cylinder and then down to the exit hole in the bellhousing, my bad


not entirely your bad imho: the volume under pressure (granted, less pression in the case of a clutch than for brakes) extends till the purge screw. If you have a large up then down such volume in the remote purging tubing, you'll have to rely on fast purging and surface tension to push the air out pass the high, and this will depend on the characteristics of the hydraulic fluid used (and tube diameter etc). If the purge screw is at the high point of the system without any high then low before it, purging will always work, without relying on speed or minimum throughput.

I use Silicon hydraulic fluid (Automec dot 5) in my street oldtimers, and one drawback is that it is prone to make a lot of small bubbles : if you need fast purging, the smaller bubbles may not have the time to gather near the local high or the purging point, resulting in a partial purge.
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PostPost by: vxah » Fri Sep 28, 2018 4:33 pm

Just one other thing, although I have not seen the Burton unit. The design of some concentric cylinders means that the pressed in back plate has a bigger surface area than the actual moving release piston. This means there is more force trying to push the back out than push the clutch fingers down... Make sure the unit is bolted securely to a flat surface to stop the back popping out! Seen it happen to a plastic cased unit where the fixing bolt heads were too small in diameter and got pulled through the plastic!
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PostPost by: vxah » Mon Oct 08, 2018 4:23 pm

Just ben looking at another one, guy has put three slaves on a Vectra and they keep failing! One of the three fixing bolts was going tight before clamping the housing.. The pressure tilted the cylinder over and popped the back out!
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PostPost by: rgh0 » Tue Oct 09, 2018 10:28 am

Another word of warning about concentric slave cylinders. As these have no adjustment they are designed to be used with self adjusting clutch pressure plates that adjust as the clutch plate wears to keep the fingers at the same position. These come in various types and have an additional benefit of achieving higher clamping loads and torque capability at lower pedal pressure and this being maintained over the life of the clutch.

I don't know if self adjusting pressure plates are available to suit a twin cam flywheel but if you don't use one the life of your concentric clutch conversion may be limited due to clutch wear.

see the attached article link on the history of clutch technology for more information.

https://media.repxpert.de/media/lokale_ ... 070715.pdf

cheers
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