Pretty much everything is aluminium, apart from the shaft which is 316 SS. Heat sources will be far away, so the only way the housings can get warm is through consistent running, which is rather unlikely (operation will be more start-stop than on forever). In between the bearings there's a pulley, so the tube idea is not possible.

Cap vs. locknut - still not sure, both have pros and cons, with no access from the side, the locknut is a) harder to torque to the right value (needs a locknut socket) b) harder to secure in place via grub screw (would need a longer thru hole on the mounting plate for allen key access). Cap / bolt has top access which is good, easy to torque to the right value, although would need Loctite or some threadlock to hold in place without undoing itself as I doubt the bearings can take huge preload needed to stop the bolt from undoing itself.

With tapered roller bearings, I'm guessing I'd need to periodically re-apply grease? I can fit grease seals, but it complicate things a bit more from a design point of view. With sealed single row AC bearings, I can just whack them on the shaft and not worry much. With tapered rollers vs angular contacts - is there really that much more stiffness offered by the rollers?

Just one addition check before I start doing proper drawings, both single row angular contact bearings should be an interference fit in the housings and a close slide fit on the shaft?

Regards,
dsc.