我被三个黑人玩的不能下

 A gear refers to a mechanical component with gears continuously meshing on the rim to transmit motion and power. The application of gears in transmission has been around for a long time. At the end of the 19th century, the principle of gear cutting and the emergence of specialized machine tools and cutting tools using this principle for gear cutting emerged one after another. With the development of production, the smoothness of gear operation was valued.

 The Chinese name Gear appeared in the late 19th century when the foreign name Gear appeared