Four thousand years ago in ancient my country, the working people began to know how to roll in production and life.
The role of the body, the use of logs to support the movement of important objects forward; the use of metal tiles to reduce the friction between objects. For example: during the 850 years since the founding of Beijing, countless ancient buildings used huge stones and wood. Weighing several tons, with a trunk diameter of more than 1 meter and a height of more than 10 meters, how to transport them to Beijing across mountains, rivers, lakes and seas, except for some by water transport, most of them are transported by rolling bodies for land transport.
The chariot was invented before the Spring and Autumn Period and the Warring States Period, and the hub of the chariot was manufactured using the principle of bearings, and modern bearings came into being along with the bicycle.
