South Pointing Chariot has two wheels, and when the chariot turns, the rotation speeds of the two wheels will differ. Introduction to the South Pointing Chariot: The South Pointing Chariot, also known as the Sinan Chariot, was a directional device used in ancient China. Unlike the compass, which relies on geomagnetic effects, it does not use magnetism. The South Pointing Chariot is a simple mechanical device that uses gear transmission to indicate direction. Its principle is that human power drives the two-wheeled chariot to move, thereby rotating the wooden gears inside the chariot to transmit the differential between the two wheels during turning. This, in turn, drives the pointing wooden figure on the chariot to rotate in the opposite direction but at the same angle as the chariot's turn, ensuring that the wooden figure always points in the direction set at the chariot's departure, regardless of the chariot's turning direction—"though the chariot turns, the hand always points south." Reconstruction of the South Pointing Chariot: Modern reconstructions of the South Pointing Chariot serve only as references and research for contemporary people and do not represent historical facts of ancient times. The inclined plane push-type South Pointing Chariot has a simple structure without gears, utilizing inclined planes, levers, crankshafts, etc. The internal mechanical transmission ratio of the inclined plane push-type South Pointing Chariot can be easily determined through experiments. In production practice, ancient people would have observed that for two wheels of the same size, when the axle length between the two wheels is half the diameter of the wheel, taking one stationary wheel as the center, the other wheel completes one full rotation when the chariot turns in place for one full circle. In other words, when the chariot turns one full circle, the differential between the two wheels is exactly one full rotation.
