What is an Automatic Watch?

An automatic watch (also known as a self-winding watch) is a mechanical watch whose mainspring is wound automatically by the natural motions of the wearer. In plain English: you move your arm, the watch gets energy, you don't have to wind it manually - Hallelujah.

In contrast, a manual watch requires you to wind the crown by hand regularly. Think of it like pushing your car up a hill versus having it make itself.

How does an Automatic Watch work?

1. Inside the watch, there is a spiral spring called the mainspring. In a manual watch, you wind it via the crown.
2. In an automatic watch, there is an oscillating weight (a rotor) which pivots when you move (your wrist, arm, pocket, etc). This rotor uses your motion to wind the mainspring.
3. Some mechanisms wind only when the rotor moves in one direction; more sophisticated ones wind in both directions.
4. A typically fully-wound mainspring in an automatic watch can store about two days' worth of power reserve - so if you take off the watch and rest it on a table overnight, it should still tick.

Preventing Overwinding

Yup, the rotor keeps winding as you move - but what if the mainspring is already fully wound? That would be bad (over-tension, parts could break). So watchmakers use a slipping clutch or bridle mechanism: once the mainspring is fully wound, excess motion simply slips and doesn't overwind.

Slipping spring or bridle

The bridle is a little steel spring pressing against the barrel wall; when the mainspring is full, the bridle slips and prevents further winding. Invented/patented by one of the founders of Patek Philippe!

History of Automatic Watches

Pocket Watches:

• As early as the 1770s, watchmakers experimented with self-winding mechanisms for pocket watches: Abraham-Louis Perrelet in Switzerland (~1776) is one of the earliest credible inventors.
• These early versions used different types of weights: side-weight (on edge movement), center-weight, rotor-weight, and movement-weight. All are trying to harness motion.

Wrist Watches:

• After WWI, wrist watches became common, so self-winding mechanisms got renewed interest. 
• One of the first commercially successful wrist automatic watches was by John Harwood in 1923: the "bumper" type, where a weight swings back and forth ~180 degrees and bumps buffers.
• The brands like Rolex improved things: in the 1930s, they made a rotor that could spin 360 degrees and increased the energy storage up to 35 hours.
• Later on, in 1948, Eterna introduced ball bearings for the rotor mechanism - a key step in making automatic movements smoother and reliable.
• Even more advanced: in the 1960s/2000s, companies like Carl F. Bucherer introduced a rotorless design (a geared ring with a mass segment around the movement) for thinner watches.

Why you should try Automatic Watches?

• Convenience: You don't have to remember to wind your watch every day if you are wearing it - your wrist does the job.
• Mechanical artistry: Automatic watches are marvels of tiny engineering - gears, springs, rotors, clutches. Show off a bit of nerd cred.
• Vintage Charm and Modern Tech: They bridge centuries of watchmaking history and still look great today.
• Collectibility: Many watch lovers value automatic movements for their complexity and heritage.

A few little quirks

• If you take the watch off and it sits idle for days, it might stop, since your wrist is not moving to wind it.
• Automatic watches may be slightly thicker than manual ones because of the rotor and added parts. 
• Motion is the key: If you are extremely sedentary (desk job, little movement), the winding mechanism might not get enough juice, so some watches allow manual winding as a backup.

Imagine your watch as a tiny gym rat: every time you move your wrist, it lifts weights (the rotor), stores energy (the mainspring), and keeps on time — all without you having to wind it. That’s an automatic watch.