Automatic watch movements are some of the most highly prized and celebrated in the industry, particularly by watch collectors who appreciate the complexity and effort that goes into constructing each intricate component that makes up the movement.
Unlike a quartz movement which is powered by a battery, an automatic movement is one of two types of mechanical movements which power the watch through an array of components including a mainspring, balance wheel and oscillating rotor. Each of these mechanisms work together to power the watch and its functions.
The other type of mechanical movement besides an automatic movement is a hand-wound movement. These types of movements must be manually wound by hand, usually by turning the crown, to wind the mainspring up and power the watch. An automatic watch movement does not require winding and is wound automatically through the movement of the wrist. As you wear an automatic watch, energy is created by the oscillating rotor which winds the mainspring and then powers the watch.
Some mechanical movements are COSC certified or given the status of ‘chronometer’ which means that the movement has been tested over 15 days against the rules of the Official Swiss Chronometer Testing Institute. These tests measure the accuracy of the watch and ensure the movement remains within +6 and -4 seconds per day.
The different components within an automatic movement:
Crown: This is the small knob usually located on the right-hand side of the watch. This can be used to set the time as well as winding up the movement
Rotor: Sometimes seen through an exhibition case back, the rotor is a semi-circle shaped weight which swings around as your move your wrist. The rotor, like the crown, is used to wind the movement in an automatic watch.
Mainspring: This is one of the most important components in an automatic movement and is the main source of power. When the watch is being wound, kinetic energy is transferred to the mainspring which stores the energy as it gets tighter and tighter.
Gear Train: This component sends the energy stored within the mainspring to the escapement through a series of gears.
Escapement: Once the gear train has sent the energy through to the escapement, the energy is then regulated and released in equal segments.
Balance Wheel: As the energy is released regularly into the balance wheel, it begins to turn in a circular motion between five or ten times a second. The faster a balance wheel oscillates, the faster the watch will run.
Jewels: These are synthetic rubies and sapphire found within the movement which reduce friction between each component. The more jewels a movement has, the higher grade the watch is considered.
You can find more information about automatic watch movements and other watch complications here.