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Jul 02, 2015 8:14 am
Jul 02, 2015 8:14 am
Subject: 2ltr clutch
Uff! I almost lost this story by mistake managing the forum. So here it is again what was starting in beginning of May:
Owning this 2ltr for a good year now, and after about 2000km driving, I only recently had severe clutch slip. If it was my driving or if it was worn out in the beginning is not sure. I always tried not to let the clutch slip. I will know if clutch slip is soon back after overhaul.
Driving up a hill finally was difficult, I had to drive with limited power. Cleaning the clutch with brake cleaner, checking the clutch adjustment, did not help. The clutch adjustment was ok, the adjustable tappets giving more than 1mm play when pressing them in against the little springs before touching the clutch cover plate. The only thing not correct was that the clutch ejector always was positioned fully to the front, so when depressing the clutch pedal, it could not move further forward, thus beeing out of operation. Therefore this nice mechanism would not work and make gearchange a bit more crashy. But it would not explain the clutch slip. The reason it could not move further forward, I think, is that the clutch shaft coupling on my car should be mounted a few mm further forward using shims or a thicker hardy discs. I found one triple and one only double hardy disc (thinner) on the short shaft between engine and gearbox, this might be the reason.
Anyway the clutch had to be removed, looks quite straightforward in the beginning but then lifting it out is a pain. I was not able to remove the lower aluminium casting hanging on the clutch driving shaft, so had to remove the whole package including the complete clutch.
There are reports about clutch overhaul in Club magazines 212 (by Peter Sowle) and 216 (by Alan Elliot). Both were helpful. Alan described the use of a turnbuckle as used for tightening wire fences, to pull up the whole package towards the aluminium bulkhead above. Which I did and it worked. Alan suspects that the chassis cross member on many but not all 2ltrs is in the way. On mine it is.
Inspection: Smell was like burned electronic boards. Linings were dry and brittle, with holes where material had broken out and some lining particles as fine sand on the surfaces. The driving plate was slightly distorted but especially had thicker and thinner areas. This can be seen on the photo and feeled by finger. The thickness of the linings on both sides was about 4mm, surprisingly thick. The club replacement ones have 4.8mm, I was told. The springs were maximum 1mm shorter than the standard 1 7/8".
Springs: the ones supplied by the club are nominal "130lb" I wonder what that means, the rate of a spring is given as force/compressed length, so it is 130lb per a certain distance of copmpression. Knowing this I could measure the rate of the old ones and compare if they have weakened. In club magazine articles authors mention the practice to put a florin in to compress the springs more (British coin used 1849-1970, changing size a bit over time, from 1893 on it had 28.5 mm diameter and 2.1mm thickness). The pocket in the flywheel allows for max. 30.5mm diameter coins or shims. Large washers (DIN 9021) for M10 screws should fit (outer diameter 30mm, thickness 2.5mm).
I will have the the cover plate and floating plate relined and fit a new driving plate (club spares) and new springs probably. And I will report the refitting and result.
A few thoughts about the clutch design: a bit complicated but the idea was to have low mass on the driving plate, this should allow faster gearchange on an unsyncronized gearbox. The clutch ejector will make sure that the driving plate will move away from the cover plate when the clutch is pressed and the clutch ejector stop prevents that it moves to much forward, then touching the floating plate. The clutch brake: when changing gears up you want to slow down the driving shaft into the gearbox. The clutch brake will do this when pressing the clutch pedal down far enough. You do not want this effect when changing gears down (the opposite, you want to speed up the driving shaft, therefore double declutching and revving up the engine a bit in between. To avoid a counteracting clutch brake, the clutch should be depressed less when changing down gears and depressed only that much, the clutch brake must not come into action yet. There are two adjusting nuts on the threaded rod to the clutch brake arm. The one closer to the clutch brake determines how early it comes and the second can compress the spring on the rod if it shall come stronger. The experienced among you of course all know this, but I really understand it better (I hope) after having dismantled it all.
Attachments:
Uff! I almost lost this story by mistake managing the forum. So here it is again what was starting in beginning of May:
Owning this 2ltr for a good year now, and after about 2000km driving, I only recently had severe clutch slip. If it was my driving or if it was worn out in the beginning is not sure. I always tried not to let the clutch slip. I will know if clutch slip is soon back after overhaul.
Driving up a hill finally was difficult, I had to drive with limited power. Cleaning the clutch with brake cleaner, checking the clutch adjustment, did not help. The clutch adjustment was ok, the adjustable tappets giving more than 1mm play when pressing them in against the little springs before touching the clutch cover plate. The only thing not correct was that the clutch ejector always was positioned fully to the front, so when depressing the clutch pedal, it could not move further forward, thus beeing out of operation. Therefore this nice mechanism would not work and make gearchange a bit more crashy. But it would not explain the clutch slip. The reason it could not move further forward, I think, is that the clutch shaft coupling on my car should be mounted a few mm further forward using shims or a thicker hardy discs. I found one triple and one only double hardy disc (thinner) on the short shaft between engine and gearbox, this might be the reason.
Anyway the clutch had to be removed, looks quite straightforward in the beginning but then lifting it out is a pain. I was not able to remove the lower aluminium casting hanging on the clutch driving shaft, so had to remove the whole package including the complete clutch.
There are reports about clutch overhaul in Club magazines 212 (by Peter Sowle) and 216 (by Alan Elliot). Both were helpful. Alan described the use of a turnbuckle as used for tightening wire fences, to pull up the whole package towards the aluminium bulkhead above. Which I did and it worked. Alan suspects that the chassis cross member on many but not all 2ltrs is in the way. On mine it is.
Inspection: Smell was like burned electronic boards. Linings were dry and brittle, with holes where material had broken out and some lining particles as fine sand on the surfaces. The driving plate was slightly distorted but especially had thicker and thinner areas. This can be seen on the photo and feeled by finger. The thickness of the linings on both sides was about 4mm, surprisingly thick. The club replacement ones have 4.8mm, I was told. The springs were maximum 1mm shorter than the standard 1 7/8".
Springs: the ones supplied by the club are nominal "130lb" I wonder what that means, the rate of a spring is given as force/compressed length, so it is 130lb per a certain distance of copmpression. Knowing this I could measure the rate of the old ones and compare if they have weakened. In club magazine articles authors mention the practice to put a florin in to compress the springs more (British coin used 1849-1970, changing size a bit over time, from 1893 on it had 28.5 mm diameter and 2.1mm thickness). The pocket in the flywheel allows for max. 30.5mm diameter coins or shims. Large washers (DIN 9021) for M10 screws should fit (outer diameter 30mm, thickness 2.5mm).
I will have the the cover plate and floating plate relined and fit a new driving plate (club spares) and new springs probably. And I will report the refitting and result.
A few thoughts about the clutch design: a bit complicated but the idea was to have low mass on the driving plate, this should allow faster gearchange on an unsyncronized gearbox. The clutch ejector will make sure that the driving plate will move away from the cover plate when the clutch is pressed and the clutch ejector stop prevents that it moves to much forward, then touching the floating plate. The clutch brake: when changing gears up you want to slow down the driving shaft into the gearbox. The clutch brake will do this when pressing the clutch pedal down far enough. You do not want this effect when changing gears down (the opposite, you want to speed up the driving shaft, therefore double declutching and revving up the engine a bit in between. To avoid a counteracting clutch brake, the clutch should be depressed less when changing down gears and depressed only that much, the clutch brake must not come into action yet. There are two adjusting nuts on the threaded rod to the clutch brake arm. The one closer to the clutch brake determines how early it comes and the second can compress the spring on the rod if it shall come stronger. The experienced among you of course all know this, but I really understand it better (I hope) after having dismantled it all.
Attachments: