This article is about mechanical gears. Two gears and gear drives pdf gears transmitting rotational motion. Note that the smaller gear is rotating faster.
Since the larger gear is rotating less quickly, its torque is proportionally greater. One subtlety of this particular arrangement is that the linear speed at the pitch diameter is the same on both gears. The teeth on the two meshing gears all have the same shape. An advantage of gears is that the teeth of a gear prevent slippage.
In transmissions with multiple gear ratios—such as bicycles, motorcycles, and cars—the term “gear” as in “first gear” refers to a gear ratio rather than an actual physical gear. Its time of construction is now estimated between 150 and 100 BC. Internal gears do not cause output shaft direction reversal. They consist of a cylinder or disk with teeth projecting radially. These gears mesh together correctly only if fitted to parallel shafts. No axial thrust is created by the tooth loads. Spur gears are excellent at moderate speeds but tend to be noisy at high speeds.