All About Automatic Watch Movements

How does it work?
All self-winding watches work on the principle of converting arm motion (kinetic energy) into the winding of the mainspring (potential energy). This is performed by a half-disc of metal weighted at the edge called a rotor, which spins when the wearer’s arm moves normally throughout the day. Relatively speaking, this semi-circular piece is fairly heavy, and it is therefore affected by gravity. As you wear your watch, this piece will move so that it is always pointed toward the ground. As you walk with your arm swinging back and forth, the rotor spins inside the watch. This rotary motion is then geared down through the gear train to wind the central arbor of the mainspring. Each movement of your arm winds the spring a tiny bit, but since you move your arm so much it easily keeps your watch wound.

You cannot overwind an automatic watch if it is in good working condition and properly serviced. In a typical system, the mainspring, which is wound at the central arbor of the barrel, is not rigidly attached to the outside of the barrel. Instead, there are a series of detents along the outer edge of the barrel that allow a stiffly constructed “clutch-like device” called the bridle to allow the mainspring to slip inside the main barrel when this spring is wound to maximum. On some watches, a faint click can be heard when this happens; on others, it cannot be heard. This overwind protection is critical to avoid damage to the watch.

Automatic – in a minute
To ensure consistent performance, you should wind an automatic watch FULLY from a dead start before wearing it. This takes only a minute, and making this a habit will ensure that your watch is always at or near its peak power. The watch will then be less likely to stop in less time than its maximum power reserve (typically 48 hours, but this varies among brands). The combination of a sluggish or undersized rotor and non-active life style can result in a watch that is not fully wound and running slow.

A good way to keep the inner mechanism of your watch consistently well-oiled is to give the crown a couple of turns every morning. If your watch is new, simply hold your watch face up and “swirl” it around in the same motion with which you would swirl brandy in a snifter. Do this for 1-2 minutes and the watch will accumulate a couple of hours worth of power reserve. When you wear your watch, you’ll complete the winding to build up the rest of the power reserve. If you wind the watch then wear it all day, you should have a full power reserve at bed time.

Want to learn all about watchwinders for your automatic watch? Read our watchwinder FAQ here.

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