Allignment question

[John Fitzpatrick]

I’ve had a problem with disengaging my clutch ever since the engine was reunited with the transaxle after an engine rebuild, and because of this I haven’t put the drivetrain back in the car . I just assumed that the clutch had been assembled incorrectly, but when I separated the engine/transaxle and removed the clutch, it was just fine and had been put on correctly. I read on another thread that a slight misalignment when bolting up the bellhousing will cause the throwout bearing to bind on it’s sleeve, causing excessive pedal pressure, so I’m thinking perhaps that’s what was causing the problem. How can I check this out, and although the engine hasn’t been run, would a misalignment have damaged the pilot bearing, which is a ball bearing type, not a bronze bushing? Transaxle's a ZF -0, Ford bellhousing, twin plate bellville type clutch.

I’m beginning to appreciate how W.C. Fields came to declare that “Life is just one damn thing after another!”

 

[Bob Putnam]

Have you checked for length-interference between the trans input shaft and the pilot bearing/crankshaft?

 

[Russ Noble]

John,

Despite that other thread, I'd be most surprised if it was an alignment problem. Bob's suggestion is worth checking out.

I would also check that there is sufficient movement of the release bearing. Have you rebuilt your m/c etc yet? if not it could have some lazy seals which would cause you to lose some stroke at the slave.

Have you got the right m/c on clutch pedal? Do you have a larger one e.g. one of the brake ones that you could fit to try to give you a bit more stroke and see if that helps things?

After that I'd get the clutch installed height, movement to release etc checked out by your local friendly clutch rebuilder.

Just a few simple ideas that I'd try first before getting too technical about alignment....

I'm not sure of your exact clutch configuration, but one other thing that is a long shot, is your f/w stepped? Has your clutch been set up taking this into account? If not it will never release!

Cheers

 

[John Fitzpatrick]

Russ-
When the engine/transaxle was out of the car for the engine rebuild, I could depress the clutch arm without any trouble. Afterwards, I could push hard enough for it to hurt my hand with no movement. Once the transaxle was off, the throwout bearing moved smoothly with no binding. That's why I thought it was a reassembly problem of some sort. Photos of the clutch are on this thread http://www.gt40s.com/forum/gt40-tech-powertrain-transaxles/22484-vintage-clutch-questions.html

I'll take the clutch and flywheel to a shop and get them checked to rule that out, and take a close look at the pilot bearing to be sure it isn't bunged up. Since this exact combination worked at one point, I wouldn't think the shaft length is an issue- unless the pilot bearing's damaged. I'm wondering how much force is normally required to release the clutch on a ZF set-up like this--surely no more than 15 lbs or so?
Thanks for the help,
John

 

[Russ Noble]

John,

If you're talking about pushing the clutch arm with your hand and you mean the clutch fork (the lever that the slave cylinder works on), then I certainly wouldn't expect to be able to depress it by hand. You are often able to depress the clutch pedal by hand, but not always though, particularly with a very heavy clutch. But to depress the clutch fork by hand in a performance V8 sort of application definitely not. IMHO although I've had nothing to do with ZF setups.

Why you could depress it by hand when you initially removed it from the car, I would not hazard to guess.....I would imagine with that sort of clamping force the clutch would tend to slip like hell!!

As for the force to disengage it I would think more likely at least 40-50 lbs where the ball of your foot goes on the pedal and maybe about 4 to 6 times more than that at the point where the slave connects to the fork. So maybe 150 to 300 lbs where you are trying to push the fork, depending on how the leverages are designed into the system. That is certainly nothing that you could achieve by hand.

Let me say I have not measured these forces but my experience would lead me to believe the figures I have given you would be in the ballpark.

I was waiting for someone else to give you a definitive answer on that but in the absence of any other replies that's my considered offering. I stand to be corrected by anyone with the hard facts.

Also John, I may have misinterpreted what you are trying to say but nothing you have said up to now would lead me to believe there is anything wrong with your clutch as it is now installed.

Cheers,

 

[John Fitzpatrick]

Thinking back to when I first got the car and started the restoration back in the early '70s, once the engine/transaxle were out, I had the clutch pressure plates re-surfaced. Is it possible that they were worn to the point that the clutch would disengage easily but now that they're redone, the required force is back to normal and I incorrectly assumed something was amiss?
Ignorance coupled with inexperience is a bitch.
John

 

[Russ Noble]

Ignorance coupled with inexperience is a bitch.
John

Don't beat yourself up John. That Lotus is fantastic car and the fact that as a guy in a wheelchair you are even attempting a job of this magnitude is quite humbling.

Best of luck with it and remember I could still be wrong!! But I don't think so......

Cheers,

 

[Jac Mac]

John,
Went back to your other thread with pics, The plates had been relined and there is a possibility that the combined thickness is greater than original spec. Can you remember on reassembly whether the fingers of the diaphragm were flat , or coned toward the trans or away from the trans on assy.

The point being that if the plates are too thick it will cause the diaphragm to be 'over compressed' to the point going over center. Once it reachs that point it no longer applies any clamping force and at RPM centrifugal force will keep it in this position. If this is the case you can save the situation by fitting thin washer's between the clutch cover & flywheel of a thickness that has the diaphragm coned toward the trans in the engaged position & just about flat in the released/disengaged position.
To get an indication of the washer thickness reqd loosen the clutch cover bolts evenly until the diaphragm is about 75% of the way back to the point where it contacts the cover. Measure the gap between the cover & flywheel and obtain washers of 'that gap' in thickness. Now removing one bolt at a time, insert washer between cover/flywheel then retorque clutch bolts & re-adjust freeboard. Now when you push clutch to release diaphragm should not go past the 'flat' position and the pressure reqd should 'feel' more even.

Jac Mac

 

[John Fitzpatrick]

Jac Mac
The diaphram was coned outward, pointing toward the transmission.
Russ-
Thank you for the kind words, and thank you both, and the other members here, for your forbearance in answering my questons. I've cut and pasted enough replies from this forum to make a fair-sized booklet, and that's just on issues that apply to my project! You should both consider getting together, perhaps with some others here, and publishing your experience? There is a need.
John

 

[Russ Noble]

That's an interesting thought John.....

Jac Mac's the man for that job. He's short of projects and this could be just the thing for him to get his teeth into......

I would suggest he needs to write two books one possibly titled "The basics of motorsport engineering - how to beat chequebook racers".:chug:

And a much much more interesting one "Tales of my misspent youth - how the f*** did I ever live to be 57?" epper::bash:oke::lol:

Although that'll be 58 in another few weeksboomsmile

Cheers,