Mechanical excellence - The watch movement

An example of a mechanical watch movement

Mechanical watch movement - what is it?

If a watch has a mechanical movement, the watch has a device for keeping time, which uses the energy stored in a wound spring, and keeps time through the highly regulated release of that energy through a set of gears and an escapement.

Mechanical self-winding movement vs quartz analogue movement

This device must be wound periodically, ensuring that the wound spring is continually loaded to power the watch. It differs from the typical quartz watch in that it uses purely mechanical components to keep time.

An example of an automatic (self winding) mechanical movement installed inside a Longines watch

Watches that are powered by automatic movements operate similar to a watch with mechanical movements, except that the winding of the spring occurs automatically, every time the wearer moves his or her arm. A rotor that turns in response to motion, winds the watch's mainspring, supplying the needed energy to power the watch. The automatic watch was invented by James Harwood in 1923 who devised a swinging weight mechanism called a "rotor" which rotates due to the normal movement of your body. The rotor is combined with a ratcheting mechanism to limit the winding motion to a uniform direction. Together, the rotor and ratchet keep the watch wound automatically. If you stop wearing the watch, however, the watch will normally wind down and stop within 1 to 2 days depending upon the capacity of the mainspring. A normal mechanical watch can run for about 40 hours on one full winding of the mainspring, and a few designs can last up to 8 or 10 days are also available.

The obvious benefit of an automatic movement is that there is never a need to replace a battery or to wind the watch. Keeping this in mind, it is necessary to occasionally "tune up" an automatic watch to ensure timekeeping is precise. The general design of mechanical movement watches have not changed notably in the past fifty years. But, the development of greater technology and modern materials has changed the way mechanical movement watches are manufactured.

Longines list of mechanical movements

An expensive watch is more accurate, right?

If this is your first time buying an expensive wristwatch, there is one very important fact you need to know in advance. A $25 Timex or Casio digital watch will keep time just as well as, and possibly better than, a $20,000 solid gold mechanical Omega, Rolex, or other very fine watch.

If that last statement surprised you, read the rest of this section carefully.

All watches tend to gain or lose a few seconds over a period of time. These are small mechanical or electro-mechanical devices that are counting out 86,400 seconds per day. Even if a watch is 99.9% accurate, it will still be off by a minute and a half in only 24 hours! So even a mediocre wristwatch has to be well over 99.9% accurate to even begin to be useful on an ongoing basis.

So, what is a reasonable expectation of accuracy from a wristwatch?

Reasonable Accuracy Expectations
by Type of Watch
Seconds gain/loss per day Best
Worst Typical Best
Vintage mechanical watch
in good repair
+/-60 +/-15 +/-5 99.9826%
Modern mechanical watch
+/-10 +/-5 +/-2 99.9942%
Modern mechanical watch
chronometer certified
+6/-4 +/-3 +/-1 99.9977%
Modern quartz watch
non-certified (normal)
+/-2 +/-1 +/-0.1 99.9998%
Modern quartz watch
chronometer certified (rare)
+/-0.02 +/-0.02 +/-0.0 99.9999%

While some people desire wristwatches with extremely high accuracy over long periods of time, it is seldom for any reason besides personal satisfaction. The few professions that depend on precision time synchronization (such as astronomy, global navigation, train scheduling, and broadcasting) base their operations on high precision time sources, not consumer wristwatches.

Ultimately, if you are living so close to the edge that having your watch off perfect time by less than a minute bothers you or otherwise throws your life into disarray, you probably need less caffeine and a vacation!

Why would I want a mechanical/automatic watch when quartz is more accurate?

Simple. Quartz is clearly better on accuracy. But there are many other advantages and pleasures from wristwatch ownership beyond just measures of precision levels that are beyond the notice of many people.

Frankly, quartz watches and many other technologies don't really do anything significant to better people's lives. People with quartz watches are no more reliably on time than people with mechanical ones. People driving cars with manual or automatic transmissions still get where they are going equally well. People still enjoy music about as much as they used to, even though CDs play it more clearly that tape or LPs did. You are not likely to have any smarter thoughts simply because you wrote them down with a computer than with an ink pen. You can easily spend as much time playing golf or football on an accurate computer simulation game as on a real playing field, but the experience is not any more fulfilling at the end of the day. And you can certainly do a lap around the lake faster in a speedboat than in a rowboat, but what have you really accomplished?

The newer technologies often gain a level of efficiency that makes them... uninteresting. In many cases, the older ways and technologies were more than sufficient, and it is their minor failings that give variety and character to doing things that way. With the older ways, you usually have to be more aware of details, understand more of what you are doing, and take more time being involved in the process. That greater interaction makes the process more personal and enjoyable for some people.

With the newer ways, you can be pretty assured your quartz watch is on the right time, your car's automatic transmission won't miss downshift on the way home, your CD will play exactly the same as it did yesterday, your computer will catch and correct your typos and misspellings, your video game won't stop in the middle because of rain or a player injured in a tackle, and you certainly won't be bothered seeing much of the detail and wildlife on the lake at high speed from your motorboat. How boring.

Mechanical watch enthusiasts often compare the movements, the finishing, the level of adjustment, types of certifications, performance under different circumstances and other esoteric measures of mechanical timepieces.

Quartz watch enthusiasts compare... mostly accuracy measures.

So if efficiency is your main desire, then quartz is for you. If you are tired of efficiency and want something interesting instead, try a mechanical watch.

Are quartz watches always more accurate than mechanical ones?

Typically they are, but not always. Accuracy and precision are not exactly the same thing.

It is important to remember that even when a mechanical watch is allowed to vary +6/-4 seconds per day, that does not mean it will consistently vary by that high an amount each day. Mechanical movements, except the very rare 'turbillon' movements that correct for it, are noticeably affected by the gravitational pull of the Earth. It only takes a performance distortion of 1/1000th of a percent for a watch movement to be one second less accurate in a day. This causes the performance of mechanical movements to be somewhat different from day to day when not stored in a fixed position. The good news is that the actual variations of a mechanical watch will often cancel each other out. This means a mechanical watch will tend to be more accurate over a longer period than the single-day COSC measurement may imply.

The day-to-day performance of quartz is much more consistent than mechanical under identical conditions. Quartz performance is affected mainly by temperature changes and weakened batteries. So a quartz watch that you measured to gains 0.5 second yesterday will be consistently increasingly off correct time by about that amount. You can be pretty certain that in 60 days, it will be about 30 seconds off. At the end of a year, it would be likely be over 180 seconds off.

Compare that to a mechanical watch that you measured to gain 2 seconds yesterday. It would seem that our example quartz watch is 4 times more accurate than this. But while the daily measured daily variations seem much higher, they are not likely to be as consistent, so will have a dampening effect. You cannot accurately predict that this mechanical would therefore be off by 120 seconds at the end of the same 60 days. It might be right on time, or it may be 200 seconds off. That broader range of variations allows most mechanical watches to stay closer to correct time than the daily variation rate implies. Over a year, some mechanicals can on average stay closer to correct time without having to be reset than a quartz watch might.


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