Bearing Up

Now that the new bearings have arrived it’s time to fit them.

Steel bearings into an alloy casing- -that means heat the casing to expand it.

The alloy expands more than the steel so by heating the case the old bearings will drop out and the new ones can be dropped in.

So it’s into the kitchen with a piece of plywood to protect the work top, some shop-rags, the new bearings and the inner and main casings.

I’ve already extracted the studs from the casings so they will sit square on their faces on the plywood  and the new bearings are unwrapped and put ready to hand.

The first casing is put into the oven, 10 minutes at Gas Mark 7 gets it hot enough that when a moistened rag is rubbed across it it sizzles so it’s taken out of the oven(GLOVES!) and rapped square and flat, open end of the bearing cup down, onto the plywood and the old bearing just drops out.

Smartly turn the casing over so it’s sitting open end up on the plywood, wipe the bearing mount clean with the shop-rag, drop the new bearing into place and then weight the bearing down to make sure it stays hard home in the casing as it cools and that’s the job done.

The second casing is now put in the oven. By the time that it has heated up the other casing has cooled enough to grip its bearing firmly and so it can now be put to one side and the whole process repeated with the second casing and bearing.

While the second case is cooling you have time to remove any evidence of your use of the oven from the eyes of S.W.M.B.O. and then get the casings etc. back into the workshop.

G/box Contents

Set out for re-assembly

Each of the bearings is held in place by a circlip and these pop easily back into place so the bearings are fully home in their housings.

Next thing is to install the output gear into the output bearing. This is a tight fit so it needs to be pressed home, easy answer is to pop over to Bob’s and use his press rather than codge up something, so with that gear now in place it’s time to rebuild the ‘box.

The gear cluster is assembled with the selector assembly meshed in on it and the whole lot offered up to the main casing, a little wangling and the layshaft end slips into its bushing, the end of the camshaft does likewise and the whole assembly slides into place.

The mainshaft is quickly slid into place through the output gear to lock things in place, the first gear pinion slid onto its end and that’s it.

main case

Gear cluster in place

All that’s left to do is fit the indexing pawl in place, put the bearing rollers in place on the cam-shaft and the inner casing can be put on and bolted up.

inner case

Inner casing bolted on

Once the inner case is in place then all that’s left to do is to fit the kickstart ratchet, match up the timing marks on the cam-shaft and the gear-change mechanism, wind up the return spring on the kickstart shaft and then fit the outer case with the foot levers and the rebuild is finished.