Movement

The mechanisms that power a watch: automatic, quartz, Eco-Drive and related concepts.

Amplitude: Amplitude is how far the balance wheel rotates from its rest position to the peak of its swing in a mechanical watch, measured in degrees and read on a timing machine. A healthy figure shows the movement is receiving good energy, while low amplitude points to a tired mainspring, gummed-up oil, or a service that is due.
Automatic Watch: An automatic watch is a mechanical watch that winds itself from the movement of your wrist. A rotor inside swings as you move and tightens the mainspring, so it needs no battery. Worn every day it keeps running; left off for a few days it stops and has to be rewound.
Beat Error: Beat error is the small timing difference between the two swing directions of the balance wheel, measured in milliseconds on a timing machine. A low figure means an even rate, while a high one can be reduced during regulation by resetting the balance's rest position.
Bridge: A bridge is a metal bar screwed over the mainplate that holds the upper pivots of the going-train wheels and balance in place. Fixed at both ends rather than one, it suspends each pivot between two anchor points. Bridges largely define the visible architecture and character of a mechanical calibre.
Calibre: A calibre is the specific movement model inside a watch, usually named by a number such as the Seiko 4R36 or Orient F6922. The calibre tells you the movement type, whether automatic or quartz, and its features such as hacking, hand-winding, beat rate and power reserve.
Eco-Drive: Eco-Drive is Citizen's light-powered quartz technology. A cell behind the dial converts any light into energy, so the watch never needs a battery change and, fully charged, keeps running for months in the dark.
Escape Wheel: The escape wheel is the toothed wheel at the end of the gear train. The pallet fork locks and releases it beat by beat, turning the mainspring's continuous power into the regulated steps that drive the hands. It is the gateway to timekeeping in a mechanical watch.
Gear Train: The gear train is the series of meshed wheels that carries energy from the mainspring barrel to the escapement. Along the way it steps the power down and the speed up, so the hour, minute and seconds hands turn at the correct rate. Because it keeps the watch going, it is also called the going train.
Hacking (Second Stop): Hacking is the feature whereby the seconds hand stops the moment you pull the crown out, letting you set the watch to another timepiece right down to the second. Not every mechanical movement offers it.
Horology: Horology is the science of measuring time and the art of making timepieces. It covers everything that keeps time, from sundials and water clocks to mechanical and quartz watches, including their design, history, and the principles that make them work.
Kinetic: Kinetic is a hybrid system developed by Seiko: the motion of your wrist turns an internal rotor, the energy it generates is stored in a rechargeable cell that Seiko calls a capacitor, and that charge drives a quartz movement. It pairs the self-winding feel of an automatic with quartz accuracy and needs no routine battery change.
Magic Lever: The Magic Lever is Seiko's automatic winding system. An eccentric on the rotor's pivot rocks a small two-pawl lever back and forth; as one claw pulls, the other pushes, so the mainspring winds whichever way the rotor turns. It uses very few parts, making it robust and cheap to manufacture.
Mainplate: The mainplate is the base plate of a movement. Every other part, including the wheels, bridges, winding mechanism and pallet, is mounted onto it. Its holes and seats locate each part in exactly the right place. Its diameter usually defines the calibre's diameter, since it is the foundation everything else sits on.
Mainspring: The mainspring is the coiled steel ribbon that stores a mechanical watch's energy. Winding tensions it, and as it unwinds it slowly releases that energy to the movement. The total energy the spring holds sets how long the watch runs unworn, known as its power reserve.
Mainspring Barrel: The mainspring barrel is the toothed drum that houses the coiled mainspring. As the spring unwinds, the barrel feeds its stored energy into the centre wheel of the going train. Barrel diameter, mainspring length and thickness, and the calibre's energy consumption together set the power reserve.
Manual-Winding (Hand-Wound): A manual-winding (hand-wound) watch is a mechanical watch you power by turning the crown with your fingers rather than from wrist motion. Each turn tightens the mainspring to store energy, so unlike an automatic it must be wound by hand on a regular basis.
Mechanical Watch: A mechanical watch runs on a wound mainspring and a gear train, with no battery. There are two kinds: automatic, which winds itself through a rotor, and manual, which you wind by hand. It is prized for its craftsmanship and a smooth sweeping seconds hand, keeps time slightly less accurately than quartz, and needs periodic servicing.
Pallet Fork: The pallet fork is a small anchor-shaped lever in the escapement. Its two jewelled pallets lock and release the escape wheel in turn, and in doing so it hands a measured push of energy to the balance wheel. That locking and releasing action is what makes a watch tick.
Power Reserve: Power reserve is how long a fully wound mechanical watch keeps running off the wrist. On most automatics it is around 40 hours; some movements reach 70 hours and more.
Quartz Watch: A quartz watch tells the time using a quartz crystal that a battery makes vibrate. It is far more accurate than a mechanical watch and needs next to no maintenance, drifting only about fifteen seconds a month and running for years on a battery, or on light.
Rotor: A rotor is the half-moon weight inside an automatic watch. It swings with the motion of your wrist, and that swing winds the mainspring. You can usually see it turning through a display caseback. Its free swing is what makes an automatic watch self-winding.
Shock Protection System: A shock protection system is a sprung jewel setting that lets the fine pivot of the balance shift slightly on impact and then return to place, so the delicate balance staff does not snap when the watch is dropped. The best known systems are Incabloc, Seiko Diashock and Citizen Parashock.
Solar Movement: A solar movement is a watch powered by light. A cell under the dial converts sunlight or room light into electricity and stores it in a rechargeable cell, so there is no routine battery change. Fully charged, it carries on running for months in the dark.