Monday, 1 April 2013

Gearbox Rebuild 2: The Practice

Opening up 270 KTA's gearbox is a little like biting into a Kinder Surprise:

Not only have you no idea what's inside, but you know it probably won't be what you were hoping to see.

(And unless Kinder have got their act together since I was a boy, it's also inevitable that at least half the toy will be broken or missing...)

Fortunately, this weekend's surprises have been largely pleasant ones. Thanks to Sheppard Senior (the Patron Saint of Bristol SUs), progress has been great and we've achieved our aims: the gearbox is out, has been examined and we think we know what's wrong. That bit isn't as bad as I'd feared.

But to get to that point, we've had to take the tin opener to other cans of worms...

Anyway, here's where we stand.

The spigot bearing in the back of the crankshaft has disintegrated, which is almost certainly the cause of our Looe noises. This is the bearing which spins on the main front shaft when the clutch is engaged. Lumps of metal, formerly rollers and the inner casing of the bearing, were discovered in the bell-housing, having been spinning around in the way of the fly wheel...

The oil seal in the front of the gearbox had also perished into oblivion, allowing the gearbox to lose huge amounts of oil. Most of this has ended up on the clutch, which will also need to be replaced, along with the oil seal on between the clutch and the flywheel, which had been smashed apart by the failing bearing.
 
Inside the box everything is fine. The front main bearing, which we'd expected to have to change, would have been taking lots of additional strain in the absence of a working spigot bearing, but we caught it in time. In fact, inside it's a really good box, with little play or wear to the gears. Good Kinder...
 
 
There are some other big problems to overcome. In removing the gearbox we had to dismantle, not just the bit of the gear linkage which connects to it, but the entire linkage from front to back. 

Someone, somewhere will remember welding up the joints which would normally make dismantling simple...

The linkage will have to be separated, re-machined and assembled properly with three new universal joints to replace what are, to look at them, the originals.

The phantom welder is probably the same person who'd remember: bashing the hell out of the top gearbox turret (which now needs replacing); drilling a hole through a knackered main bush and bolting it up to reduce the play; replacing the front oil seal without bolts in the housing to stop it from flying out; replacing every loose stud with a tatty old bolt, regardless of threads; and, perhaps it's the same person who secured the prop-shaft with set screws instead of shouldered bolts. I do hope this wasn't you...

In summary, we have a lot of work to do. The next few evenings will be spent sourcing parts and cleaning up the old bits. 270 KTA will have to wait patiently on her pedestal while all this goes on.

Then, when we're ready, we can think about how to go about putting the ultimate Kinder toy back together...


Keep you posted.

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