Wednesday, 26 December 2012

Ever deeper - Coupling Gears and Bearings

Under the guise of clearing out the workshop (I was - I was trying to finish off the primary case polishing, but Mrs H was surfing and wanted some Boxing Day P&Q) I ventured into the shed to retrieve the coupling gear cover.

The idea is that once the coupling gear cover is off, I can polish it and the primary case.

The nuts and screws came out relatively easily, but the cover was a b****r to get off, as we say in Norfolk.

Turns out that the cover has a steel locating sleeve around two of the studs, which corrode and resist the removal of the cover. A few minutes with the hide mallet and a soft drift had it shifted (seized at the front, where the steel sleeve meets the weather).

Anyhow, here it is, off:


No drama there, all present and correct - though I expected the coupling cover main bearing to slide out of its journal and stay on the shaft. The peculiar face-type oil seal is cratered - bits of the seal are completely missing.


Here is the cover, complete with bearing. There is a fair bit of gunge in there, which will be ferrous material from the wear on the gears I expect.

The bearing is in there, and for some reason refuses to turn. The story is that this bearing, which is essentially similar to the other drive side main roller bearings, has a inner race which is 0.001" smaller than the roller bearing in the crankcase, so that the corresponding journal on the crankshaft is also smaller. 

This means that when the engine is assembled, the smaller outer journal (the one for the coupling gear cover bearing) will pass through the main bearing in the crankcase.

This bearing is also lipped on the outside of the outer race. It's not entirely clear why they did this, since the crankshaft is located axially at the timing side.

Anyhow, this went back into the workshop to be cleaned up. It turned out that someone had fitted two paper gaskets to this cover for some reason.

The bearing came out with some gentle persuasion (a hammer and a socket in the time honoured fashion) but a look inside the outer race revealed it was junk:

A massive pit and some odd wear marks in the outer race. There were possibly some wear marks on the inner race as well, but we need to look further before passing judgement on those. 
All in all, a jolly evening's work.


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