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Feature: What’s Inside A Real Rolex Watch?

What a Rolex looks like on the outside is no secret. Being the best-selling luxury watchmaker in the world, chances are the Submariner’s visage is familiar to most of the people here—but what about the inside? What lies beneath that plain, unadorned case back? In an era when most manufacturers are desperate to show off the great amounts they spent on their movement, Rolex continues to buck that trend. Let’s take that case back off and see just what’s going on inside.


The calibre 3135 has been powering Rolex watches since 1988, when it superseded the previous 3035. In the Submariner, it has since been retired for the updated 3235, although it still lives on, for now at least, in the Datejust 34. With millions of units made, it has proven itself as one of the sturdiest and most reliable movements ever conceived. How does it work? It all starts with the winding.

For a very long time, wristwatches—and pocket watches before them—were wound by hand. A watch’s power comes from its mainspring, coiled tight in the mainspring barrel. For the 3135, the mainspring holds 48 hours of power, which would once have meant manually winding it every other day—but not for the 3135.

Rolex was founded in 1905, London, England

Rolex was founded in 1905, London, England

An evolution of an existing idea, the Perpetual winding rotor was Rolex’s solution to automatically topping up the watch’s power. As the wearer moves, the semi-circular weight spins, coiling the mainspring tight to keep the watch running. It can slip when its full, too, so it doesn’t wind to tight and break. And those two purple wheels aren’t there just for show; inside them are ratchets that allow the Perpetual rotor to wind the movement no matter which way it spins. Unlike many other watchmakers, Rolex has made these Teflon-coated wheels removable so they can be properly serviced.

The power from the mainspring leaves very slowly, and so underneath the winding rotor assembly is an unseen sequence of gears that get quicker and quicker. The first spins once every sixty minutes, directly driving the minute hand; the next two convert the speed into one rotation per minute for the seconds. Thirty-one synthetic rubies, grown in a laboratory, act as bearings, chosen for their low friction, hard-wearing properties. But what about the hour hand? That has a separate gear off the minute hand which slows the rotation to once every twelve hours.


The Rolex calibre 3135 beats at 28,800 vph. That is to say, eight times per second. Many people are more familiar with the idea of a quartz watch or clock beating or ticking just once per second, so why eight? Here’s the boring answer: physics. The more interesting answer? That’s a little longer. You see, a watch needs to regulate its power—that is to say make sure it’s used evenly. I’m sure you’ve been in a car with a driver on the highway who thinks the throttle pedal is an on/off switch. You accelerate, you slow down, you accelerate, you slow down. And you feel sick.

This would make for a very bad watch. So, like that bad driver, a watch needs cruise control, something that keeps its speed constant. That’s the escapement, which consists of three major components, the escape wheel, pallet fork and balance wheel. The balance wheel is the key, the amount of time it freely bounces back and forth, like a pendulum’s swing, pretty much constant. Each swing, eight per second, allows the second hand to creep forward at a consistent rate. But here’s where physics tries to mess things up.

The smaller a balance wheel is, the faster it can go, increasing the number of ticks per second. This 3135 does eight, but wristwatches with bigger balance wheels often beat slower, and pocket watches with even bigger balance wheels slower still, ticking around half the speed of the 3135 at four times per second. There’s more mass to accelerate and decelerate, that kind of makes sense.

The Rolex Submariner was first introduced in 1953

The Rolex Submariner was first introduced in 1953

So then, why would you want a faster beat? Doesn’t it use more power? Well, not only is it a by-product of shrinking movements to fit into wristwatches, it’s also a very easy way to increase accuracy. With automatic winding systems reducing the need for longer power reserves, it means more attention can be given to performance. Like a basketball spinning on a finger, the faster it goes, the more stable it can be, and that can protect it better from shock. But shock isn’t the only thing trying the upset a balance wheel: there’s also position, temperature and magnetism.

The 3135 is armed against those things. The balance wheel is made from Glucydur, a beryllium alloy with minimal thermal expansion. The tiny gold Microstella weights on the balance wheel can be screwed in and out for fine tuning. The spring itself is spun from Parachrom Bleu, a niobium alloy that shields it from magnetism. There’s even a little Paraflex shock absorber securing the balance jewel to protect it from knocks. The watch is then set up and tested in five different positions and temperatures to make sure it doesn’t drift more than two seconds per day.


Rolex has been well-known for fitting high-quality movements into its watches for over a century. Its calibres are built to last, as is evidenced by their longevity, and provide excellent timekeeping, as is demonstrated by their chronometer certification. They’re workhorses, no two ways about it, which was fine for an era when a Rolex was a watch built to be worn by a professional, but perhaps stands at odds with the luxury approach expected today. Perhaps that’s why Rolex choses to cover the 3135 up?

Well, funnily enough, no. The 3135 may not be decorated to the levels of a Patek Philippe or Vacheron Constantin, but it’s no bare-bones tractor engine either. But what do I mean by decorated? For that, we’re going to need to understand a little more about what watchmaking really means.

Switzerland has been producing watches in earnest since around the 18th century. Sure, it was making them before that too, a religious reformer by the name of John Calvin banning jewellery—and dancing, of all things—in 1541, forcing the jewellery-makers of the time into watchmaking, but the country didn’t start to earn a reputation until both the British industrial revolution and the French revolution. British watchmakers were too expensive and French watchmakers were too, well, dead. The ones that got away fled to Switzerland, including a certain Mr. Abraham-Louis Breguet.

The Rolex Submariner 116613 LN features the Calibre 3135

The Rolex Submariner 116613 LN features the Calibre 3135

But the real turning point for the Swiss industry in a commercial sense was the introduction of the American System of Watchmaking. Having devised a mechanised method of mass production to cater for the volume of quality watches needed for the vast American railroad system, Americans like Florentine Ariosto Jones, founder of IWC, were tempted by government incentives to bring that ability to Switzerland.

Where companies such as Patek Philippe, like the British and French watchmakers of old, had earned a reputation for making components one by one by hand, now it was possible to use machines to do the bulk of the work instead, leaving just the final finishing and assembly needing that human touch. Those British and French watches were often rather plain, perhaps featuring an engraved cover, but with this newfound time on their hands, watchmakers in Switzerland could use their expertise in the decoration of the movement itself.

But it’s not all for show. There is a practical motive. The rhodium plating of brass plates and bridges, for example, wards of corrosion; bevelled and polished corners and countersinks stop sharp edges fragmenting; striping and graining catches and holds any pieces of debris; mirror-polished screws—well, I think they do that just to look nice. These days on a movement like the calibre 3135 it’s done more by machine than by man, but it’s there. You just don’t get to see it.

In one sense, it’s perfectly reasonable for Rolex to hide its movements. Historically, it’s got more in common with DeWalt than it does Patek Philippe, producing quality products built to do a demanding job and do it well time after time, where aesthetics are superfluous. The 3135 continues to demonstrate this approach in its construction and technology, often preferred by watchmakers, being both reliable and easy to service. But on the other hand, watchmaking is different now; the brands are living, breathing museums whose exhibits are to be found on the wrists of millions the world over. In the case of Rolex, perhaps it would be nice, now, if we got to enjoy a little more of it.

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