Disc: 11 lobes, on an eccentric12 fixed ring pinsAn output pin: the slow outputThe eccentric pushes the disc around inside the ring of pins. The disc has one lobe fewer than there are pins, so after one input turn it has rolled back by one lobe: 1/11 of a turn, the other way. The output pins sit in holes bigger than they are by twice the eccentricity, which lets the disc wobble around them and passes on only its slow turning. Many lobes touch pins at once, so cycloidal drives carry shock loads well and have very little backlash. Real ones use two discs 180° apart so the wobble balances.