I had a tough time understanding the purpose of one of these gears as the operation of it is quite strange. https://www.youtube.com/watch?v=kcdj-b49TW8 https://

I had a tough time understanding the purpose of one of these gears as the operation of it is quite strange. https://www.youtube.com/watch?v=kcdj-b49TW8 https://www.youtube.com/watch?v=kcdj-b49TW8 ...this lego version made it a little more understandable. Roughly: it's a motor turning an ellipse, and the ellipse is pushing against a flexible "sock" made of metal with geared teeth. All this is contained _inside_ a fixed gear. As the motor turns, the ellipse turns, and causes the geared teeth to push and squeeze against the fixed container. This gearing motion is designed to take ~100rpm's down to ~1rpm (very high _reduction_ ratios)... as the outer container has ~100 teeth and the inner has ~99 ... every one lap around the large gear only advances the small inner gear a single notch. So... high motor speed is converted to low motor speed. The fixed containing gear never moves (it's fixed), and you rely on the flexibility of the inner metal flexible "sock" in order to turn another shaft which is giving the output power. In the lego model you see using red "nubs" for the fixed outer gear, yellow "windows" to catch the "nubs", and then the yellow "splines" simulate the flexibility of the metal / sock component. As the lego model turns you see where the motor driver is turning the ellipse. The basketball-picker-upper is effectively attached to the "sock" directly and that is the output work. A lot of the animations are really hard to understand (compared to physically seeing it working) because the gearing ratio is so low... hard to see the output movement over time compared to the lego on.