Heavy clutch

[Tim D.]

11 hours ago, Z320 said:

Hi Colin,

in my opinion the problem is the poor design of the TR construction with a shaft and fork,

and the wrong combination of the hydraulik cylinders. The clutch cover is not the problem or solution.

The diaphragm clutch covers

are all have about the the same size and design but a different strong spring and the need for different forces on the pedal.

Me and my mate Jochem had a closer look on the at with our concentric release bearing project, he did some quality measurements at his company.

On the photo: a B&B cover old design on a TR6 flywheel, friction plate between, RHP release bearing, bronze carrier with anti spin pin.

The maximum forces to give the friction plate free are (all tested with the RHP bearing):

- 1,000 Newton: Laycock, only used / NOS

- 1,240 Newton: B&B old design "8+8 1/2", only used or NOS

- 1,300 Newton: Sachs 100 041

- 1,500 Newton: B&B new design "LC03JR003B"

- 1,840 Newton: Mazda MX5

- 2,000 Newton: Sachs 100 142

Because I use a Mazda MX5 gearbox in my TR4A I gave Jochem a MX5 clutch cover to check too!

It is well known the MX5 clutch works very easy - but is one of the strongest ones, guiding me to the

Release mechanism:

The hydraulics on the MX5 works with a fork witout shaft, it only seasaws on a ball pin and has a good combination of master and slave.

When I started first with this issue 6-8 years ago (?) I noticed the pedal gives the clutch free after a very short way of travel,

much enough way of travel was "needles" and good to use a smaller master cylinder.

I changed from the original 0.75" master first to 0.70", next to 0.625", I suppose 0.050" would also work, if it would be aviabale from Girling.

On a TR6 a adjustable pushrod makes sense to push the slave piston as deep as possible in the slave cylinder.

Some other TRs run this way on my recommendation, like Tim D.'s TR6

My recommendation "for little effort" is to use the B&B new design or Sachs 100 041, a 0.625" master, RHP bearing and bronze carrier with spin stop pin.

The forces reduced down from 23 kg to about 16 kg, like on a small new car.

Concentric clutch release bearing:

I ended with this (strongly modified Sachs hydarulic from Opeel/Vauxhall Omega) on my TR4A gearbox, and later also on my MX5 gearbox.

Still with the 0.625" master a and "B&B new design" it gives a little more benefit and needs no limitation of the way of pedal travel.

But it's only the last 5-10%, only a few mates will go that way (lots of effort). If you still have any questions, please ask.

Currently I'm working an an article for our German TR IG club magazin about the issue.

Ciao, Marco

The 0.625 is an easy fix, but you must use an adjustable push rod between the pedal and master cylinder to get enough throw to disengaged the clutch. Means the pedal is higher in the footwear. But is not an issue (we did the round Britain Reliability Run and more like this with no issues. )

Tim

[Z320]

3 hours ago, PodOne said:

Hi Roger

Looks completely different to what I fitted as a Laycock clutch looked like this https://www.ebay.co.uk/itm/314898315902?_ul=UK&mkevt=1&mkcid=1&mkrid=710-53481-19255-0&campid=5338353466&toolid=20006%26customid%3Ds%3AGS%3Bgc%3ACj0KCQiA1rSsBhDHARIsANB4EJaY56_1FptqyGUi8kbJ7QzSvQh84XgfT0ReC6wy4CUg2heraaq5kuYaAqSXEALw_wcB%3Bpt%3A1%3Bchoc%3A2&customid=s%3AGS%3Bgc%3ACj0KCQiA1rSsBhDHARIsANB4EJaY56_1FptqyGUi8kbJ7QzSvQh84XgfT0ReC6wy4CUg2heraaq5kuYaAqSXEALw_wcB%3Bpt%3A1%3Bchoc%3A1&gad_source=1&gclid=Cj0KCQiA1rSsBhDHARIsANB4EJaY56_1FptqyGUi8kbJ7QzSvQh84XgfT0ReC6wy4CUg2heraaq5kuYaAqSXEALw_wcB.

Andy

Yes,

this is the Laycock cover like the one we measured, my mate Wolfgang supported us with it.

Ciao, Marco 

Edited December 28, 2023 by Z320

[Colin Ablewhite]

Hi all.

 It occurred to me how funny it is that my dodgy left knee that can’t push a clutch pedal, can open a great big tin of worms!

A great thread and I am sure lots of us are learning a lot more about clutches.

Thanks for the pictures of the servo. I thought that was a logical place to put it. On my 6 I will just have to find a new home for the screen washer bottle.

Coli.

 

[Z320]

I‘m well used to the issue people don’t to what I recommend 

[harrytr5]

Watch out with some so called reconditioners as the trick they can pull is machining of the fingers to loose that wear groove leaving the fingers half the thickness.

12 hours ago, Z320 said:

Yes,

this is the Laycock cover like the one we measured, my mate Wolfgang supported us with it.

Ciao, Marco 

Watch out for some so called recon Laycock covers that I have seen, to loose the wear groove, they machine it out leaving the fingers half the thickness. 

What do the good ones do when presented with this wear pattern?

I am interested as I have a few worn ones like the one above and would like them reconditioned the proper way.

Regards Harry

[seanlen]

I do remember Alec P used to get clutches refurbed and was highly complimentary of the quality of work from this company - https://precisionclutch.co.uk/contact/

Sean

[stuart]

1 hour ago, harrytr5 said:

Watch out with some so called reconditioners as the trick they can pull is machining of the fingers to loose that wear groove leaving the fingers half the thickness.

Watch out for some so called recon Laycock covers that I have seen, to loose the wear groove, they machine it out leaving the fingers half the thickness. 

What do the good ones do when presented with this wear pattern?

I am interested as I have a few worn ones like the one above and would like them reconditioned the proper way.

Regards Harry

Precision clutch will rebuild clutches to whatever spec you require Harry, they are very good we use them in preference to new unknowns.

Stuart.

[stuart]

3 hours ago, Colin Ablewhite said:

Hi all.

 It occurred to me how funny it is that my dodgy left knee that can’t push a clutch pedal, can open a great big tin of worms!

A great thread and I am sure lots of us are learning a lot more about clutches.

Thanks for the pictures of the servo. I thought that was a logical place to put it. On my 6 I will just have to find a new home for the screen washer bottle.

Coli.

 

I relocated the one on that car to the front of the wheel arch and fitted a header tank instead of the overflow bottle.

Stuart.

 

[Z320]

„Kick that petrol filter in the bin“ (please)

 

[Z320]

21 hours ago, harrytr5 said:

Watch out with some so called reconditioners as the trick they can pull is machining of the fingers to loose that wear groove leaving the fingers half the thickness.

Watch out for some so called recon Laycock covers that I have seen, to loose the wear groove, they machine it out leaving the fingers half the thickness. 

What do the good ones do when presented with this wear pattern?

I am interested as I have a few worn ones like the one above and would like them reconditioned the proper way.

Regards Harry

Hi Harry, just a few thoughts....

We did not measure the pressure of the clutch cover on the friction plate, but all this 8 1/2" covers are pretty much the same construction.

I suppose, but I could be wrong, the Laycock cover need the lowes force to press - because it has the weakest spring and holds the fricion plate less tight.

No, in my opinion it is very likely not its genious construction causing the lowes force to press.....

According to the German workshop manual the B&B "old design 8 / 8 1/2" was original on the TR4A.

This is why in my opinion the Laycock cover is not desirable to own / use.

I told before what my recommenadtion is, but i'm used to the issue.....

Ciao, Marco

 

About the groove on the fingers I have my own idea, but I want to wait for ideas from others.

Edited December 30, 2023 by Z320

[stuart]

1 hour ago, Z320 said:

„Kick that petrol filter in the bin“ (please)

 

It was removed before final road testing, tank condition was at that time unknown

Stuart.

[CharlieBubbles]

I got nicely fooled on this; my CR had the ‘wrong’ CP .75 inch bore master cylinder, so in a bout of enthusiasm changed it for the ‘correct’ .70 inch. Almost immediately the clutch refused to disengage without double declutching. Suspect the PO had felt the clutch was on the way out and changed to the .75 to get a bit more travel on it to put off the need to deal with it. The clutch plate looked ‘orrid when we got it out!

[JohnC]

On 12/29/2023 at 7:40 AM, Tim D. said:

an adjustable push rod between the pedal and master cylinder

Why not between the slave and actuating lever? Isn’t that much simpler?

Cheers,
JC

[JohnC]

On 12/29/2023 at 1:29 AM, Z320 said:

And the adjustable push rod is not really needed if the clutch worked before…..

 

Hi Marco,

Is that correct? If you need 30% less force, you’re going to get 30% less travel at the slave cylinder for the same pedal travel. From what I’ve read elsewhere (e.g., Buckeye Triumphs) I thought the slave travel was marginal, so reducing it by using a smaller m/c would cause problems with disengagement. Would be great to know otherwise. In that case I’ll order a smaller m/c straight away!

Regards,
John C

[Tim D.]

1 hour ago, JohnC said:

Hi Marco,

Is that correct? If you need 30% less force, you’re going to get 30% less travel at the slave cylinder for the same pedal travel. From what I’ve read elsewhere (e.g., Buckeye Triumphs) I thought the slave travel was marginal, so reducing it by using a smaller m/c would cause problems with disengagement. Would be great to know otherwise. In that case I’ll order a smaller m/c straight away!

Regards,
John C

HI John,

You are correct, reducing the diameter of the master reduces the amount of fluid displaced by the master and hence reduces the distance the slave moves. In my hands a 0.625" does not move enough fluid to disengage my Saab 900 clutch.  The way to solve this (which I did) is to increase the distance the clutch pedal pushes the Master cylinder. This is where the adjustable push rod on the pedal works. In a TR6 if you lengthen  the pedal push rod the pedal itself moves back towards the driver. This has the effect of increasing the "throw" of the pedal and hence the distance the pedal moves the pushrod and in turn the clutch master cylinder. This displaces more fluid and moves the slave more disengaging the clutch. It is one of those things you have to work through in your mind.

Lengthening the slave pushrod could in principle produce similar effect by preloading the throw-out bearing against the clutch cover so less movement is needed to release it. But it is a bit too much like riding the clutch and to me would increase the wear on the throw-out bearing and the engine thrust bearings.

 

Hope this makes sense..

Interestingly the amount that clutch pedal moves towards the driver is not really noticeable..

TIm

[Z320]

Hi John,

thank you for your question, 2 points to start with:

#1

If you follow at forums the problems of not proper working clutches - this are „always“ TR6!

There must be something „different“ on them, I guess I know what it will be, but TR6 owners (I‘m don’t own one) will know better

#2

You know yourself best when your clutch engages and disengages and how much senseless way of travel you have to push the pedal fully.

Now to your question.

Yes, 30% more pressure and less force causes about 30% less way of travel of the release bearing.

On my 4A the way of travel of the original 0.75“ master is 30 mm!
This is about 0.56 x 30 mm on the 1“ slave = 16.9 mm

With the length of the release fork / the length of the lever on the clutch shaft = 1- 65/87 mm there is another reduction of 26% = 12.6 mm

With a 0.625“ master this is only 0.625 x 0.625 / 1 / 1 x 65/87 x 30 mm =  8.8 mm on the release bearing!

But….what I supposed and Jochem measured,

the needed way of travel to disengage the clutch is only 2.5-3.0 mm!

This is because it reacts like a seasaw:

once loaded by force the diaphragm spring (like a seasaw beam) react only a minimum elastic - and than lifts up the steel plate of the clutch cover from the friction plate!

Believe it or not, also a 0.5“ master would work.

If not, the in any way limited possible travel of the master is the problem.

Ciao, Marco 

Edited January 4 by Z320

[Waldi]

I agree with Marco about the “hollow cylinder” SC, which is fitted inside the GB bell house.

Due to it’s design it should require less effort. 

It not only eliminates the friction in clutch shaft bearings, SC-pin, clutch fork and carrier, but also the hack-saw action of the bearing carrier.

On the other end, my clutch system (all standard parts, B&B clutch, I think but properly overhauled) works relatively light to I see no need to upgrade.

Waldi

[Z320]

Hi Waldi,

I also felt my clutch not special strong, this is all relative and subjective.

This is why I made a tool to measure and dropped from about 23 or 24 kg down to 16 kg,

which is like a new small car.

Ciao, Marco 

[JohnC]

10 hours ago, Tim D. said:

You are correct, reducing the diameter of the master reduces the amount of fluid displaced by the master and hence reduces the distance the slave moves. In my hands a 0.625" does not move enough fluid to disengage my Saab 900 clutch.  The way to solve this (which I did) is to increase the distance the clutch pedal pushes the Master cylinder. This is where the adjustable push rod on the pedal works. In a TR6 if you lengthen  the pedal push rod the pedal itself moves back towards the driver. This has the effect of increasing the "throw" of the pedal and hence the distance the pedal moves the pushrod and in turn the clutch master cylinder. This displaces more fluid and moves the slave more disengaging the clutch. It is one of those things you have to work through in your mind.

Lengthening the slave pushrod could in principle produce similar effect by preloading the throw-out bearing against the clutch cover so less movement is needed to release it. But it is a bit too much like riding the clutch and to me would increase the wear on the throw-out bearing and the engine thrust bearings.

Thanks Tim (and Marco). That all makes perfect sense. I hadn't thought through what the effect would be of the pedal-m/c pushrod. And it sounds like it may well be worth experimenting with a smaller m/c anyway. I have already gone through all the normal wear points to reduce play so I may have travel to spare.

Cheers,
JC

[Tim D.]

7 hours ago, JohnC said:

Thanks Tim (and Marco). That all makes perfect sense. I hadn't thought through what the effect would be of the pedal-m/c pushrod. And it sounds like it may well be worth experimenting with a smaller m/c anyway. I have already gone through all the normal wear points to reduce play so I may have travel to spare.

Cheers,
JC

No probs. 

[Z320]

13 hours ago, Waldi said:

I agree with Marco about the “hollow cylinder” SC, which is fitted inside the GB bell house.

Due to it’s design it should require less effort. 

It not only eliminates the friction in clutch shaft bearings, SC-pin, clutch fork and carrier, but also the hack-saw action of the bearing carrier.

On the other end, my clutch system (all standard parts, B&B clutch, I think but properly overhauled) works relatively light to I see no need to upgrade.

Waldi

Hi Waldi,

out at holiday I worked through my photos and found one of my calcultion sheet for the Vauhall Omega concentric release cylinder (inside the bell housing).

Its way of travel with the 0.625“ master is only 8.17 mm, 

this is less than 8.8 mm, as calculated above, and why it needs some less force to be pressed (+ no friction of the shaft, fork, connections).

But this is „not needed“, most TR owners will be very pleased with the 0.625“ master and RHP bearing.

Ciao, Marco 

[Z320]

9 hours ago, JohnC said:

Thanks Tim (and Marco). That all makes perfect sense. I hadn't thought through what the effect would be of the pedal-m/c pushrod. And it sounds like it may well be worth experimenting with a smaller m/c anyway. I have already gone through all the normal wear points to reduce play so I may have travel to spare.

Cheers,
JC

You are welcome,

any question helps me to write a better article for our club magazine 

Edited January 5 by Z320

[Z320]

Hi all,

one thing I want to add, this may convince you.

When I started my way with the clutch (0.75" master --> 0.70" master) I asked myself how I can trust "my foot".

Meens: do I only realise an improvement because I expect and hope for this? All other insight could disappoint me?

To avoid this I needed an instrument to measure the force, so I made one.

It looks like a step for horse riding? With the steel plate I step on the clutch pedal.

On top the loop is to hang in our electronic luggage scale, in this a loop from a mountain rope.

In the rope I step with my left foot and pull the step down on the clutch pedal, reading the scale.

This is a bit a challenge of balancing, but after some practice it works well.

I started years ago with a standard TR setup of 0.75" master, RHP release bearing (lovely) and B&B "new" design cover with 26 kg on the pedal!

This has been very strong - but what you expect from a TR! Confirmed with my tool by several TR6 owners / friends.

With the 0.625" master I remember 16 kg (or 18 kg?) this was already very nice and I have been very pleased.

Today I measured only 12 kg with a "comparable" 0.51" master (indeed a 0.625" master with Sachs concentric hydarulic) and new Sachs cover ...041 for Saab.

This is about the force needed on modern cars and makes me more than very pleased

Ciao, Marco

Edited March 7 by Z320