👉 In mechanical engineering, a "countershaft" refers to an arrangement of gears or other rotating components where two sets of teeth are disposed on opposite sides of a common axis. This arrangement is often used in machinery such as bicycles and motorcycles for reducing friction and increasing efficiency. For example, the wheels of a bicycle are typically mounted on the front wheel with one set of teeth facing forward, which allows for easier pedaling. The other set of teeth faces backward, allowing the bicycle to turn more easily
