clutch clapming query

[simonjrwinter]

As a rule of thumb (this is not TR specific) how much should a clutch cover need to be tightened down?

Let me explain, when fitting a new clutch, driven plate is in place, clutch cover lined up and bolts in finger tight. Any more bolting down of the clutch cover is against the clamping force of the cover so roughly how many mm would it need to bolt it up completely?

I'm trying to find out if 4.5mm is enough (again not on a TR)

Any advice appreciated

Simon

 

[john.r.davies]

Any workshop manual will/should quite a torque value.

As you probably know, TR6 16-20ft-lbs.

 

Not a lot, bit more than hand tight, hand tight with a tweak, really.

 

But what are these units you quote for bolt tightness? Mms??

Newton-metres, perhaps? Written Nm? But 4.5 Nm is only 3,3 ft-lbs, so that can't be it.

John

[peejay4A]

I can't recall exactly but around 5mm sounds like the sort of take up on a clutch cover I'd expect once it's located on the dowels.

 

John, I think you've read Simon's question wrong, or I have.

Edited February 9, 2016 by peejay4A

[simonjrwinter]

Pete, Thank you, yes that was my query

Simon

[john.r.davies]

No, I read the question thoroughly - just couldn't believe that Simon meant tightening a bolt by a distance.

That's why I asked about a misprint, "mm" for "Nm"

 

Is this a new way of securing a bolt?

Rather like a stretch bolt, torque to certain level (hand tight), then turn through a certain angle (or, enough to compress the spring by 4.5mm)

 

Are clutch cover bolts stretch bolts?

Why not torque them?

The bolts cannot be tighter than a sliding fit in the cover, and some movement is inevitable. Unless the bolts grip the cover to the flywheel, it will wobble under load.

But engineers are infinitely inventive - what car is this and how is the cover secured?

John

[simonjrwinter]

Ok, I'll put it another way

When tightening clutch cover bolts, you are tightening against the clamping force of the clutch cover.

How many mm would the metal face inside the clutch cover be pushed back when the bolts are torqued up in comparison to the position of the clutch cover when sitting on the bench.

Edited February 9, 2016 by simonjrwinter

[john.r.davies]

Ah! So! Question nothing to do with securing the cover?

 

Then your answer - 4.5 mm?

but even hand tight will take up a tiny bit of compression in the spring, no idea how much.

John

Edited February 9, 2016 by john.r.davies

[peejay4A]

I don't think the tightness has anything to do with Simon's question. He's worried about the amount of compression of the clutch cover springs and whether 4.5mm. is normal.

[simonjrwinter]

Yes I've got a slipping clutch (not on the TR) and it seems to me the clutch cover has seen better days.

The clutch driven plate itself looks fine but as there's only 4.5 mm worth of clamping force to control 400bhp, I'm worried it's not enough.

Simon

[peejay4A]

4.5mm might be enough if the diaphragm spring is in good condition.

[Ian Vincent]

It should be straightforward enough to calibrate the clutch cover in terms of kilos per MM and them work out if the resulting clamping force is going to be enough. There must be data on the web somewhere that will provide the answer.

 

Rgds Ian

[Nigel Triumph]

The engine is out of my GT6 at the moment, so I've just measured the gap between clutch cover and flywheel.

 

With the clutch cover pressed firmly onto the friction plate and flywheel by hand, the gap is 3.5 - 4mm. The friction plate has done about 15,000 miles and is slightly worn, so with a new friction plate no doubt the gap would be a bit larger. And of course the GT6 clutch is 8" diameter compared to 8.5" on the TR6, though otherwise of similar design.

 

Your 4.5mm measurement with a new friction plate seems correct to me.

 

 

Nigel

[mleadbeater]

What is also important regarding clutch fitting is the height of the clutch release thrust pad relative to the position of the release bearing in the bellhousing.

to get correct clutch engagement and release, the bearing should engage with the thrust pad just before the 90 degree position of the yolk's arc of travel, if the thrust pad is too low the clutch may not release, if too high the clutch may be partially engaged and possibly slip.

As the clutch cover is tightened the thrust pad is raised as the springs compress. On older coil Spring clutches this can be adjusted by moving the fulcrum stops on the release arms, with diagram clutches this is usually not possible, so the only way to alter this is by fitting a thicker friction plate, or, conversely machining the face of the flywheel.

Suggest you check this either before you fit the gearbox, by measurement, or on the bench with engine and box engaged.

Hope this makes sense and is helpful, I know from bitter experience the frustration of having to remove the gearbox to adjust an non-operational clutch.

 

Mike