Windmill
I regret I never made a video of the animated windmill on my White River & Northern IV; I didn't even take a decent photograph of it. All I can say is the blades spun, and also it changed direction.
Functionally the mechanism is nearly identical to that of the oscillating desk fan. The key to its operation is a pair of telescoping tubes with a rod at the center. The spin rod spins the blades via a right-angle friction drive arrangement. A spring holds the friction disc mounted on the blade drive shaft against a drive disc made from a segment of rubbery wire insulation. The spin rod rotates within a thin-walled tube that's soldered to the frame; at the other end of the swing tube is a cam and follower arrangement that, through a gear reduction, rotates the swing tube back and forth in an irregular fashion. The swing tube runs through a fixed tube that's attached to the base. Hopefully this illustration helps clarify that long, rambling description:
