Lotus Elan

Heavy clutch

PostPost by: JonB » Thu May 17, 2018 7:01 pm

My Plus 2 has a heavy clutch and I'm fed up with it. Takes all the joy of driving the thing away.

I've searched and the standard answer is "they all do that". But why? It can't be beyond the wit of man to improve the thing!

So, I've been thinking. There are some well known options, such as changing cylinder bores or altering the pedal (move master cylinder pin closer to pivot) which sacrifice travel for leverage. Maybe fit a concentric slave? Not sure how this helps though, other than to protect it from the exhaust heat.

Someone on PistonHeads was going on about the concentric spring fitted to the clutch itself. This is what you're pushing against when you press the clutch pedal. The point was, they get harder as they age, due to ear or something. Not sure I go along with that, but anyway....

What I thought was, "let's cut a few of the spring tines off". Obviously an evenly spaced number. This sacrifices clutch plate pressure for pedal effort. Might it work? Or will I end up with a slipping clutch? Anyone tried it?
1973 Elan Plus 2S 130/5 - UK - Chassis 50/1115L
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PostPost by: MarkDa » Thu May 17, 2018 9:20 pm

Have you compared tours to others?
Basically you have to trade pedal travel for load.
For a given pressure plate if you increase the slave to master cylinder bore area you can reduce pedal pressure - but yo may not be able to displace enough fluid to release the clutch!

There are several threads on here about concentric slaves.
Try a Google search to get some ideas.
Not cheap by the time you've done some machining.
And of course it's engine out - or can you drop gearbox on your chassis.
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PostPost by: Concrete-crusher » Thu May 17, 2018 9:28 pm

Over the years I’ve changed 2 clutches and in both cases the new pressure plate made the clutch much lighter

I would not risk cutting of fingers , but it’s worth changing the pressure plate

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PostPost by: vincereynard » Thu May 17, 2018 9:51 pm

As you state Jon, the standard answer is they all do that. I believe the original was something like a Hillman Hunter / Rapier pressure plate so there is no real reason for the Lotus to be so heavy other than poor design.

Toad problem was exaggerated by the usual dimwits having fitted an incorrect slave. You could experiment with a larger slave or I considered a servo for the clutch. Land Rovers of some persuasion have them I believe.

Or go to the gym! Probably best to exercise both legs or you could walk strangely.

I've read that a concentric slave (off a SAAB) does give a lighter pedal, probably by having a superior mechanical advantage. (No pivoting arm to consider. ) But its an engine out job.
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PostPost by: StressCraxx » Fri May 18, 2018 2:46 am

Concrete-crusher wrote:Over the years I’ve changed 2 clutches and in both cases the new pressure plate made the clutch much lighter

I would not risk cutting of fingers , but it’s worth changing the pressure plate

Steve


Steve,
That's exactly my experience. As the disc wears, the diaphragm in the pressure plate has to travel farther over center and requires more effort to release the pressure. The stock slave and lever arm are not well aligned and there is an uneven push from the slave to the clutch arm causing a loss of mechanical advantage. Yes, the SAAB concentric slave is a big improvement.

Regards,
Dan
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PostPost by: JonB » Fri May 18, 2018 6:36 am

Right then, new clutch.

Thanks all! Will add it to the list.
Last edited by JonB on Fri May 18, 2018 10:02 am, edited 1 time in total.
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PostPost by: pauljones » Fri May 18, 2018 9:16 am

Jon

Im sure my clutch only weighs a few kg, not heavy at all. You sure yours is correct.?
Kick the tyres and light them fires...!!!!!!!
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PostPost by: JonB » Fri May 18, 2018 10:00 am

Hi Paul

Not sure if you're joking or not. Weighs as in "the parts weigh this much when off the vehicle"? In which case, :lol:

.. or Weighs as in "I only need this much weight on the pedal to disengage it"?

If the latter, how are you measuring it?

Cheers
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PostPost by: vincereynard » Fri May 18, 2018 3:10 pm

Another problem is that the arm is at a poor angle when it is in contact with the clutch pressure.

I established where the release contacted the pressure and discovered the arm was over centre already.
Note the washers, most of which are the bellhousing thickness + a couple to create a better mechanical advantage.

166-may.-18-16.01.jpg and


The tube supporting the release also comes loose. (All a bit of a lash up to be honest!)
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PostPost by: JonB » Fri May 18, 2018 3:42 pm

So what you're saying is it could be improved.

What angle would be best? Yours looks like nearly 90 degrees to the input shaft.
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PostPost by: john.p.clegg » Fri May 18, 2018 5:50 pm

Half way through the travel it should be at 90 degrees..

John :wink:
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PostPost by: vincereynard » Fri May 18, 2018 6:58 pm

JonB wrote:So what you're saying is it could be improved.
What angle would be best? Yours looks like nearly 90 degrees to the input shaft.


As John states. Ideal is 90 degrees at release point. Maybe that is why it gets heavier when worn? The lever is past 90? Anyway my original clutch was such a mess - scored flywheel / worn driven / 4 speed pressure / loose guide tube etc etc, the new clutch could hardly fail to be an improvement. Surprise was it worked as well as it did!

They are probably all slightly different anyway. Dry test it with the engine and box out of the car and measure where the release contacts pressure plate. That's how I found mine could do with a tweak.
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PostPost by: JonB » Fri May 18, 2018 7:59 pm

I will.

This "engine out" job is going to be quite an odyssey. But worth it, surely..
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PostPost by: vincereynard » Fri May 18, 2018 9:00 pm

As mentioned in another place - only you can judge!
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PostPost by: MarkDa » Sat May 19, 2018 12:54 am

Is it bad enough to be a summer job?
Or are you going to combine it with head going to machine shop?
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