I think Mark Dance’s idea of driving this turntable with a wheel riding out near the edge of the table is going to work!
Rather than dig into the Lego for real, I made my own wheel from some O-rings and brass and 1/2″ styrene tube. The 1/2″ wheel yields about nine turns for a full 360 degrees – some work, but not enough to be really truly annoying. As you can see, the wheel sits in a recess in the plywood half-cover for the turntable that also supports the current collectors and that used to support the worm drive.
To spin the wheel, I jammed a piece of a turnout actuating rod into the end of the wheel’s axle. This should enable me to thread the drive through the maze of benchwork here at the edge of the railroad much easier than a pukka set of universal joints. It isn’t a long run, but I’ll certainly want to test it before declaring final victory.
From below, the drive wheel peeks out through a square hole in the turntable cover. Sadly, I didn’t get to complete the testing because the nuts I picked up at Rona this afternoon on the way home turned out to be 6-32, not 8-32 as I thought when I grabbed the package.