What is Clutch disengage force ?

[car1.0]

I have a question.

I had the problems with the clutch diseengaging,
due to the very hard clutch pedal.
And it "bumped" harshly.
No way to soft clutching, shooting the clutch all the time.

Gearbox has expired and needs replacement.. ;-(

What should be the force direct to the diaphragm spring to disengage clutch? 
I mean the immediate force from the bearing pushing the fingers'-spring.

I have disassembled my VW 1.0 ltr motor clutch, 190mm diam. from Lupo.
Clutch plate not worn, flywheel dry and free from overheating.
Bearing was not heard while disengaging. 
(the worn-out gearbox was heard while clutch engaged)

I have measured this disengaging force with scale 
pushing to the center of the preasure plate
(diaphragm spring) with a lever.

and it came 100 kg to disengage (1000 N newtons)
it is huge force!
Maintaining disengaed took 80 kg
ad releasing begins at 60 kg

I know this is not other parts that made so much resistance, it is a clutch spring.

I wonder is this a normal pressure force, this 100kg? 
Certainly not.
What is the source of this spring stiffness? Overheating?

[mk2]

This is a known problem.

It is caused by a mixture of clutch dust and gear oil, which creates a sticky, glue like substance. It sticks to the outside of the clutch release bearing spacer tube, and prevents the release bearing from sliding up and down easily. It should be dry.

Yes, it creates a huge force. A new clutch needs about 200N (~20kg) of force to operate at the pedal.

It is unrelated to the gearbox itself, but indicates that there is a leak on the input shaft seal. Now that the gearbox is out, it makes sense to change all the bearings and seals 👍🏻 Lots of pics please

 

[car1.0]

mk2
Thank you for your answer!

I have read something about that glutous mixture here somewhere here in the topic of clutch... 

The conclusion seems to be correct: the mixture clogs the splinter axle. 
I understand this.

Having read about these symptoms I tried to check the cover plate with the spring.
It is outside the working environment and engaged by the lever. 
No bearing and no splinter axle resistance.

On the polish fb mechanics group they told me that proper force is 100 till 140 kg.
Mine is in the normal range.

>A new clutch needs about 200N (~20kg) of force to operate at the pedal.

YT mechanic measured 24 lb (12, 5 kg) at the pedal. 

I had so much more than 12-20 kg at the pedal!

(I have driven several cars, and this one had the hardest clutch. Easily 40kg.)

Do you think that this failure is due to the strong force on the spring + friction force? 

My dillema: if clutch cover functions within the range - should I change it? 
Will I get the easier, lighter new cluthch cover? (I doubt it).

I attach pictures from checking the clutch cover force.
The lever presses the clutch, reaching 100 kg easily., 
maitaining disengaged at 80 kg.

[mk2]

I like your scientific method👍🏻

I once had the same problem on one of my Lupos. At the pedal it was so stiff/hard to disengage I thought the clutch cable was going to snap (or the pedal box break). It also was that sticky residue on the inside of the release bearing...

The clutch diaphram spring only needs to pop in and out. If it works, then it is ok. The force isn't really that important as the engine torque is quite low in our Lupos. Just check where the release bearing contacts on the spring centre; The wear limit is half the thickness of the metal. So 1/2mm groove is ok... use a tiny amount of MS3 (CV joint) grease.

[car1.0]

mk2
Thank you for your answer and recognition! 
I am an egineer, maybe for that reason the method is little more than guessing.

I guess the additional friction resistance of the spline slider made the clutching work of the cluch 
literally "explosion of torque" from the rotation inertion due to the different rotation velocities:
of engine and gearbox spline axle. The clutch is not worn out, because the clutching was done in 
small parts of a second so this was a easy task. 
But for the gearbox it was not.

The kicking violently the gearwheels made them first weakend, then dead.

Now I have dead gearbox, not spinning the axle in some gear positions. 
Concrete stop. As concrete poured into and dried.

 

My consideration is to exchange the gearbox (with one with other gear ratio to move faster)
and to have a clutch assembly
so healthy
to not to spoil that newly exchanged gearbox again.

Now I have no clue if my cluthch - although "normal" is healthy?

 

[ObjectiveAway]

On 5/3/2022 at 9:03 PM, mk2 said:

I like your scientific method👍🏻 

[…]

 The wear limit is half the thickness of the metal. So 1/2mm groove is ok... use a tiny amount of MS3 (CV joint) grease.

Thank You both, this came out as a very interesting topic, and I also didnt know the wear limit, thats very useful information.

[car1.0]

mk2 you wrote:
 

Quote

But what I'd noticed is that the primary input shaft seal, which is meant to keep the gear oil inside the gearbox, starts to weep very slightly as it gets old. The rotary action of the spinning shaft or maybe just capilary action allows a very small amount of oil to build up around the guide sleeve. Some of that oil makes its way between the sleeve and the releaser which naturally starts to collect clutch dust. Which then turns into really thick sticky gunge.

The gunge has properties best described as very thick sticky toffee like tar, with fine grit in. Such a high viscosity substance between the sleeve and releaser simply jams the action, resulting in a heavy clutch. It doesn't help that the clutch release bearing lever that presses against the springs moves in an arc, which naturally tries to twist the release bearing when you put your foot on it. When you release, it gets pushed straight back by the springs, so engaging is not a problem- only releasing...

so my guess is that fine metal in your gearbox oil has worn the seal, which is weeping, collecting dust and causing the releaser to be sticky.