Vertical shaft bearings

[davidwheeler]

After correspondance with Mike Benwell and study of the Spares Catalogue, we have discerned the correct configuration of the bearings, to whit:-

In the head, the top bearing is a thrust bearing and the bottom one a plain ball bearing.
In the block, the same.

Thus, the thrust is directed downwards on both shafts, being pushed down on the top shaft and pulled down on the bottom one.

I found I needed about 1mm. of packing washers on both shafts to eliminate all play and ensure a trace of preload.  I even fitted the upper gear on the lower shaft (if you see what I mean) without the key and then pulled up the nut to check that it did not skid round on the shaft and also that it required a little tap to free it from the taper.  I made up an extractor to remove the gear and found that the threaded holes in the original gear are Whitworth but in the Consortium gear metric.  Fortunately, if you are removing an original gear, metric bolts will fit well enough!

[johnturner]

Well yes, that's what the book says, but a good number of engines I have taken apart have thrust, or angular contact, bearings at each end of the shafts in both block and head, and it does make a sort of sense. As you will have heard, the camshaft introduces a fair amount of backlash into the gear train which must introduce some load up, as well as down, and it was presumably for this reason that Jonathan's top shaft was trying to climb out of the head? (see the thread below)

[davidwheeler]

I did too on Boot but I did not pre-load them enough and there was a little play both up and down and side to side resulting, probably, in the Great Oil Pump debacle.  The serious thrust is taken by the thrust bearings as in the book and the side thrust is taken by the radial bearings.  I think I would prefer to follow the Master!

[davidwheeler]

I have recently re rebuilt the engine with particular attention to the vertical shaft and bottom bronze bearings.   I found that some play had developed in the lower shaft which I measured it with a dial gauge and fitted a shim to take up the play plus a thou or two preload.  I also found slack had developed in the upper shaft in the head, due not a little to the taper pin having come half out!!  I made a new pin and further shims to take up all play.  This together with fitting new bottom bronze gears with nil to a few thou tolerance has resulted in a much quieter engine.