Gear wheels are used to transmit a rotary motion from a driving shaft to a driven shaft in a form-fit manner. Depending on the ratio of the number of teeth of the gears used, the speed and torque can be maintained, reduced or increased during transmission. This ratio is called the transmission ratio, whereby the consideration is made from the driven to the driving gear. The inverse ratio applies to the resulting speeds, see the following formulas. Due to the positive engagement between the gear pairs, the rotary motion is transmitted precisely and without slippage.
A gear pairing consisting of two or more gears combined with each other is called a gear transmission. The smallest gearwheel is often referred to as a pinion, the largest simply as a gearwheel. The driving and driven gears always rotate in opposite directions. If this is not desired, a third gear must be used as an intermediate gear. Gear drives typically only require small center distances, which can be influenced by the number of teeth selected.
