A mechanical watch is a type of clock that uses a mechanical method for measuring the passage of time, differing from those that measure the time from a measurable natural phenomenon (such as sundials, hourglasses, or watches based quartz oscillation, which also incorporate electronic components)
This mechanism converts the circular pinion in one continuous linear zipper by movement, which is simply a rigid bar toothed. This mechanism is reversible, that is, the rectilinear motion of the rack can be converted into a circular motion by the pinion
Can transmit rotary motion between two parallel axes, and change the speed but not the direction of rotation (not possible to make a shaft rotate clockwise and the other counterclockwise). On bicycles they are widely used the "speed change" composed of several wheels on the pedal shaft (catalina) and several in the wheel (pinion), which allows for modifying the position of the chain, between 15 and 21 different speeds.
Gear is a wheel or toothed cylinder used to transmit rotary motion from an alternative or part of one machine to another. A set of two or more gears which transmits the movement of one shaft to another is called gear train.
This mechanism is improved rod-crank system. Basically it consists of connecting: A crank handle (or eccentric) with the head of a connecting rod (the crankpin of a crankshaft or eccentric shaft in an eccentric can also be used). The foot of the connecting rod to the piston.