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Coil to diaphragm clutch conversion confusion


Colin Lindsay
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Ever get one of those mornings where the brain will not work and everywhere you turn to for reference only confuses things? Welcome to April 13th...

I decided a while back to keep the original coil spring clutch on the Herald convertible and rebuilt the gearbox clutch release arm accordingly. Now, as I've found I have two brand new original B&B diaphragm clutches it makes sense to use those. I need to match the correct release bearing to the correct clutch. I had believed that the flat faced bearing, to the right in the first photo below, was for coil clutches and the thicker rounded-face version on the left was for diaphragm, but having checked a few of my spare release lever arms I find early cars, which were coil spring clutch, with the rounded bearing. I've checked online but cannot find the definitive photograph that will confirm and some suppliers are just listing a one-size-fits-all part with the same photograph.

  Secondly I've checked the carriers and found a complete mixture of bearings and carriers; some short carriers and some long but each with different bearings fitted. The last photo on the right shows the early alloy gearbox lever arm but it has the rounded bearing and long bearing carrier, and it dates from 1959 / 60 so there's no chance of using my spares as a definitive reference. As a lazy man's method of confirmation can anyone confirm that for a Herald with diaphragm clutch (and yes I've swapped flywheel and slave cylinder) I need which bearing on which carrier? Flat on short / flat on tall / rounded on short / rounded on tall?

38E078CD-00D9-4844-A5C3-F5AAE29693AC_1_105_c.jpg.85c1e5fdfd13618a0e99860d5a71d517.jpg 9760A99D-9321-44A6-AA1A-8180BB5D6D35_1_105_c.jpg.b214a2f57746307e910d76bb2410ba06.jpg  F4B4597C-6FFC-4ECE-8DD4-329BDEDEF552_1_105_c.jpg.c366456be0ef5c57cadffd335b784298.jpg E014F406-599B-4BBA-9F09-95F2095F23E2_1_105_c.jpg.3b7cbc2f0fe0e3a58bdff7458ed1fd44.jpg

 

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in general  clutch design  a coil cover has a flat platen so you need a pretty flat bearing to match it as the two faces stay the same as the cover is operated

a diaphragm cover needs a rounded face as the fingers have to slide over the face as the cover is operated  

a diaphragm cover is normally shallower than a coil so has a deeper carrier to make up the change in stand off .

the coil cover may use a semi rounded as a self centring idea if the geometry of the throwout lever means 

concentricity is let say ...a floating variable 

Pete

 

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Thanks Paul; of course the only bit he doesn't mention is the size of the bearing carrier (I have three sizes!) but a quick reference shot of a 13/60 seems to confirm it's the longer carrier and the rounded bearing.

s-l1600-35.thumb.jpg.d4ca9e1bf950c72e53d7729158c28659.jpg

Now all I have to do is work out how one of mine ended up with a short carrier and a round bearing, which wouldn't work on any clutch... :)

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Ok so have killed my alloy backplate and in removing the flywheel etc again have also killed the locking tab washers on the flywheel bolts. They were quite rusty but I didn't think they were so bad as to fall apart, so need replacements. 

Part number is 102076 NLA as usual. I see the later cars don't use them; early bolts are 105116 but suppliers seem to be replacing them with 138526. As luck would have it I've just bought four of those from Paddocks. I'm assuming they are some kind of interference fit and don't need tab washers?

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