Carbon /Graphite Release bearing FAILURE

[AC Ace Bristol]

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During January / February  BEX333 had a major Service,   Check and rebuild Gearbox, Fit new MGB Clutch Cover,  Borg & Beck  Graphite release bearing / AP centre plate,  Fit J type over drive unit,  check Differential and install  a Quaiff Limited Slip unit

Having covered just 986.5  miles  in readiness for Le Mans Classic and  another 60,000 miles of  enjoyable .. :)  AC Motoring.

On Sunday 24th July, Stuck in heavy traffic  covering 1.2 miles in 70 minutes trying to get into the Bicester Heritage /  Classic & Sports Car Show.
The Clutch Failed,  Couldn't get into  any gear,  Thank fully inside showground,  carried out obvious  visual inspection,  Clutch  Master cylinder level correct.  Pedal travel &  return all Ok. and the slave cylinder operating correctly , However  really excessive movement ( adjustment ) to engage and disengage clutch.

Sunday evening   arrived at  Tony Byford's  workshop courtesy of the RAC,  quick inspection indicated the Carbon / Graphite release bearing had broken .


Monday removed the gearbox to find the Carbon  /  Graphite had come free polished the metal cup / carrier and broken into many pieces and dust
so called Borg & Beck  Release Bearing bought by  Tony Byford in good faith was  definitely not a genuine Borg & Beck unit,  Having no casting name or part number.

I DO NOT ride the clutch and everything was set up correctly by Tony, I  can only assume the adhesive / bonding agent securing the  carbon - Graphite  into
the metal carrier had failed  and excessive heat generated by  graphite revolving against the face of the cluctch  cover  and inside the carrier caused the carbon  Graphite to break up.
Hours spent cleaning carbon - Graphite from  inside Bell housing, Flywheel , Starter Ring , Starter Bendix etc etc, fitted my old 60.000mile Borg & Beck Release bearing still has lots of  plenty of material. 
Hopefully up and running for weekend then off to Le Mans Classic 5th July.  Bloody Hell that's next week.

Has Any one else experienced this type of Failure ??   Is it Cheap inferior  3rd world copy  masquerading as Quality Borg & Beck product. .??
Suggest one always  checks for correct trade marks and casting numbers.      ...    Expensive Exercise 


Picture or two too follow. ;)


Keith

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[pjbowman]

Wow Keith, sorry to hear all of that! At least you weren't left stranded in the middle of nowhere (always look for the silver lining, right?). Hope you have a great time at the Classic, and no further issues!

[GSouthee]

Hi Keith

Dam shame, had a similar experience in my land rover SII V8,the release bearing broke up again an alleged B&B item. I suspect 3rd world copies getting into the system.


Still hope all ok for Classic, I have just finished pulling, filling and priming a couple of dents in the rear wing of the Ol Girl, these were acquired yesterday by some half wit who did not bother to leave any details etc etc, now trying to find a paint match but unlikely before trip to Classic.

G

[B.P.Bird]

Pictures from Keith of BEX 333 and suspect release bearing. In quite a few miles and many races I have never experienced a carbon thrust race failure. The only difference I note in Keith's case is the diaphragm clutch, but there should not be a significant difference in load on the release bearing. I wonder if Borg & Beck Competitions Dept. still exist - they might report and advise on the cause and remedy ?



No carbon in the release bearing, but plenty spread around the bell housing.



Comprehensive break up

[Robin A Woolmer]

Diaphragm Clutches like uniform pressure on the release pad, the type of rotary movement by the release carbon does not deliver this, the best clutch release for diaphragm clutch's is a concentric slave!
Some gearbox input shafts have a sleeve which can guide the release carbon but it does need to stay aligned with the pad as the arm rotates.

Robin   

[AC Ace Bristol]

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Robin

Very interesting,  But having covered in excess of 60,000 miles on the old Graphite Borg & Beck release, I would assume it was well suited.
Many other Club members run MGB Clutch cover with 8.5 inch AP racing centre plate and small modification to ensure the slave cylinder activates
pivot arm and the clutch correctly,  None of us competing with Ace Bristols, BMW 328, Bristol Cooper &  Arnolt Bristol have ever experienced the
graphite element breaking up.

Keith

PS

Keith.
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[Robin A Woolmer]

Keith
Then you have good experience that it works, what is apparent, it looks as though the graphite has been loose & spinning in the holder so not bonded! that cannot help, the AC design had the carbon ring clamped in not bonded!
Not sure how the modern carbon release bearings are held in the housing?

Hope all goes well for your trip.

Robin

[AC Ace Bristol]

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Robin

The Carbon/Graphite  in early BMW engine is secured by pinch screw,   

Does anyone know main contact for Borg & Beck for possible analyst of the carbon graphite to determin the true B&B spec  and compare with broken sample.

As the carrier bore no  embossed Bog & Beck  name or part number, Can only assume inferior copy.

Will re inspect condtion of  graphite  in carrier  next  December / January. and replace with correct spec B&B  unit

Just pays to buy origonal NOS  spares, too many inferior spares entering the market... >:(


Keith
 

[Robin A Woolmer]

Keith
It appears that this type of failure is not unique , the MG B people have the same experience even to the extent where the cast iron carrier has broken up, also people have fitted a roller type bearing & those have exhibited similar failure!
I understand Borg & Beck closed there operations a few years ago & after market people are probably trading similar parts!
The carriers do vary in the dimension of the pivot centre to the carbon face so are you sure you have the correct part? this will effect how concentric/aligned the bearing face is to the clutch pad!
It is difficult to find actual carbon replacement rings now, the main type available are what you have!
Most Carbon rings are made in India.

Robin 

[AC Ace Bristol]

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Robin

Thank you for the update,  Went through Tony's stock of NOS and Part worn release bearings,  all the same dimensions, the NOS items have Cast
Borg & Beck.
One was not marked B&B and no Part number cast into carrier,  this was the twin to the one fitted to BEX333, Tony decided to dispose of it as he
couldn't afford to fit a potentially suspect item.  ;)
Tony assured me he bought this pair along with a pair of Borg & Beck clucthes, however the thrust release were not in  Borg & Beck boxes, but bought in
good faith as B&B.

Thank you Robin for your input, I will investigate further and report back on this thread.

Keith

[AC Ace Bristol]

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BEX333   ..  ..  ..  Back up and running... :)
drove home via scenic route and Silverstone,  95 miles.   All running well.
Will check clutch adjustment after clocking up another  100 or so miles. Then off to Le Mans Classic.

Thank you to all those who either posted  information on this thread or sent me emails.  appreciated.

Keith

[bobbylangley]

Got your RAC cover up to date Keese....? Just saying'  ;)

[AC Ace Bristol]

Bob ..  ..  aka  Comedian

Yes!   RAC Cover up to date,   THANK YOU,  However  Craig told me he has agreed with you that  we take your Cobra instead of BEX...
More room , creature comforts etc but we have to take spare throttle cable.... ;)

Now back to the Serious Thread  ..  ...   :) 

Keith

[AC Ace Bristol]

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Back from Le Mans Classic , clocking up 937 miles ......  BEX running well on the old Carbon Graphite Thrust release. 

Confirming that my original set up and adjustment was correct and proving that the Cheap 3rd World Borg & Beck Imposter / Copy was made of inferior material.
I believe the bonding agent failed to secure the Carbon Graphite ring in its cup whilst covering just 1,2 miles in 70 minutes  getting into The Classic & Sports Car / Bicester Heritage show two weeks ago.   ( Beware of Cheap imports )

I would like to thank all those who phoned and emailed , It is very interesting to learn of the various combinations of  Ace Bristol Clutch kits employed in England,  Europe,  USA & Australia.   A little knowledge with me  can be dangerous,  So I will consult and  have a few  words with one or two of you and maybe publish a technical feature in a future issue of ACtion.

Keith