After letting this shift shaft cause me bunch of unnecessary headaches — playing around with all sorts of solutions such as split bushings, pinned joints, and the like — I finally decided to use the KISS method and simply have the splined ends welded onto the shift shaft with the existing flange bearings already on it. A quick trip by my favorite local welder and I’m in business.
The bearings are now non-removable, which is admittedly a little bodgy, but in reality it won’t make any difference. After all, having bearings as a captive part of a larger assembly isn’t unheard of in the engineering world and, given this bike’s experimental nature, the chance of this linkage ever getting sufficient use to warrant replacing these bearings due to wear is a pretty far-fetched notion. At whatever future point these bearings are no longer serviceable, I am sure the bike itself will have been long-ago disassembled, or a rusty and corroded hunk lying in a field somewhere.
BTW, the discoloration on the shaft is NOT excessive HAZ from the welder. I’d previously blued the ends using a polypropylene torch to un-do the red thread locker.
I’ll re-assemble the whole shifter mechanism on the bike this evening and see if it all works as intended.
