I had many animated effects on the White River & Northern IV, and several of them I'm replicating. One of the more popular ones was a window fan. The mechanism is dirt-simple: I attached fan blades to the end of a geared motor shaft, and positioned it behind a model box fan enclosure.
Usually if I'm building an animation I'd built before, I like to up the stakes. This time, I made it much closer to scale in size, and... I made two. They reside in the window display of the hardware store.
I figured the hardest part would be the mechanism, but this turned out to be the easiest, thanks to a "sacrificial" toy insect, which had the perfect gears to make a simple gear train (above). The last gear of the gear train pops up through the floor (first image below) to engage two tiny gears behind the window display (second image below).
Those two tiny gears, incidentally, I had to make by slicing them off of a larger originally compound gear. Also, I made the washers from tube styrene. And the shafts are cut from #72 drill bits. The fans themselves—at least the boxes—were relatively easy to make. They're just thin slices of square brass tube; the grilles are bits of Plano stainless steel freight car roof walk.
It was the fan blades that monopolized my time. I tried a great many things before I finally settled on soldering three wheel hubs from an etched brass cart kit together. I hadn't done such fine soldering since my days working in T Gauge. It took many, many tries—it's a good thing I had a few spare kits.
