When you push the pendulum, you interfere with its natural frequency — a little, or possibly a lot, depending on when and how hard you push it. Ideally, the pendulum would be given impulse instantaneously, at its equilibrium point, and there would be no variation in rate.
However, anything that actually physically impulses a physical pendulum will introduce errors. The problem is made even more severe if you want to have an actual clock. Now you not only have to keep the pendulum swinging, but you must also count each swing mechanically.
You therefore need some sort of mechanism that both gives impulse to the pendulum and which, in doing so, advances a gear train. Such devices do exist — they are called escapements.
The anchor escapement is an example of this simple but wonderful device. The animation shows only three components. The anchor and pendulum are in grey and the escape wheel in yellow. The escape wheel is made to rotate — maybe by a weight attached to a pulley, or maybe by a mainspring barrel.
As the escape wheel rotates, it is alternately locked and unlocked by the anchor, under the impetus of the pendulum. Every time the anchor unlocks the escape wheel, the escape wheel tooth slides along the curved impulse face of the anchor, giving the pendulum a push. You can see the beauty of it — the escape wheel advances one tooth; the pendulum gets an impulse; this is all you need, really, to have a clock.
The name "escapement" is apt — with each oscillation, it allows one tooth of the driving wheel to "escape," or advance.
Let us now turn to the balance and spring. In a watch, there is no pendulum; rather, there is a balance and balance spring. The key point here is that the balance stands in for the pendulum, and the balance spring stands in for gravity.
The balance is held at its equilibrium point by the spiral balance spring. If you give the balance a push, it will begin to oscillate; in one direction the spring tightens, and then releases energy to push the balance back to its equilibrium point; in the other direction, the spring coils expand, and release that energy to push the balance back in the other direction.
The beauty of the spiral balance spring is that ideally, it is like gravity — isochronous, as the force of the spring will be proportional to the force of the impulse. If we look at the anchor escapement, however, we can see that it does not fully fit the definition of an ideal escapement. In an ideal escapement and I owe a lot of this analysis to Daniels' Watchmaking , which for a lucid explanation of the principles of a practical watch escapement is very hard to beat , impulse would be applied instantaneously at the equilibrium point, in both directions, with equal force each time in order to ensure perfect symmetry of motion especially important in a watch.
There would also be no friction involved as this dissipates energy and affects the motion of the oscillator. The anchor escapement fails on both counts — not badly, by the way; you can get excellent performance out of it — but it is not an ideal solution.
Moreover, the sliding friction at the escape wheel teeth and pallets, as the curved projections of the anchor are called, requires oil, and any oil will eventually thicken and evaporate over time. The viscosity of oils will also change with temperature, and this means that the ideal escapement would be oil-free as well.
A watch escapement should be self-starting — that is, its design should be such that the watch will spontaneously begin to run once a certain amount of energy is wound into the mainspring. The escapement must have good safety — that is, it should not unlock accidentally if the watch is given a shock. And overall, of course, in giving impulse and counting oscillations, the escapement should interfere with the natural harmonic motion of the oscillator as little as possible.
So we have a little checklist:. All this means that designing a watch escapement that fits as closely as possible the requirements of an ideal escapement is a very tall order indeed, and if you think about it, you begin to understand why successful, practical escapements are very few and far between. Escapement design is something horologists have been fiddling with for or so years, but while many are called, few are chosen, and the timeline of horology is littered with the sad, silent, inert corpses of escapements which enjoyed, as it were, a brief moment in the sun before fading and falling with all the poignant finality of a cherry blossom oh, chaff-cutter escapement, we hardly knew ye.
With this in mind, we can now look at some examples of escapements in modern watches. If you own a watch today, and it doesn't say Omega or Roger Smith on the dial, there is close to a percent chance that you have a watch with a lever escapement.
There are a number of very good reasons for this. One of them is simply longevity — the lever escapement, which evolved from the anchor escapement for clocks, appears to have been invented by Thomas Mudge in , and it has been with us in one form or another ever since.
It can be made in various configurations — tourbillons often have a side-lever, for instance, in which the ruby pallets are in a radial line to the center of the balance, rather than perpendicular to it, as in conventional lever watches — but the basic principles have been the same for almost years. This means that when you buy a modern lever escapement mechanical watch, even a humble Seiko 5, you are getting the benefit of over three centuries of cumulative research and development, conducted by some of the finest minds in the history of the applied sciences — which is a pretty terrific thing, and the reason that good accuracy and precision are so widespread as to be taken for granted in modern horology.
A lever watch movement. Left to right, mainspring barrel, center wheel, third wheel, fourth wheel, escape wheel, and lever; balance not shown, for clarity. The animation is of an ETA which was originally designed as a pocket watch movement. In a classically set up watch, the center wheel turns once an hour and the fourth wheel, once per minute; the fourth wheel drives the sub-seconds and the center wheel, the motion works for the hour and minute hands.
So how does the lever escapement stack up when you look at it against our checklist? Not bad, my friends, pas mal. It delivers impulse in both directions, and it is also self-starting. Moreover, the lever has excellent safety. The angle of the impulse and locking faces of the ruby pallets, and the escape wheel teeth, interact in such a way as to press the shaft of the lever firmly against its bankings , which is the term for the pins that prevent the lever from moving any further at either extreme of its swing.
The fact that it takes quite a jolt to cause the lever to unlock accidentally gives the escapement great reliability and is a big factor in lever escapements having found their way into wristwatches that have all sorts of adventures, from mountaintop to sea bottom and everything in between. As a side note, banking pins are usually adjustable, but they can also just be the solid walls of the well in the movement plate in which the escapement sits; these are so-called solid bankings, and they are one of the requirements of the Geneva Seal.
Lever escapement animation; note the two banking pins, left and right. The pressure of the escape wheel teeth keeps the lever firmly pressed against its bankings. Animation, Mario Frasca, Wikipedia. So why go to the trouble of developing any new escapement at all? Well, the lever's not perfect. For one thing, it doesn't deliver impulse completely symmetrically you'll notice the lever arm is longer on the right than the left.
Like any escapement, it introduces its own, characteristic escapement error — impulse is delivered as the impulse jewel on the balance passes through the notch in the upper tip of the lever, and there is a loss of energy as this happens. This, combined with other aspects of the escapement's geometry, tends to introduce a losing error — this losing escapement error is an inherent feature of the lever escapement which must be taken into account in the design and setting up of the rest of the watch.
The most formidable problem, though, is the sliding friction between the escape wheel teeth and the ruby pallets. Those teeth are scraping along those jewels, and there are no two ways about it. And although the friction isn't all that high — friction is proportional to load, and the loads in a mechanical watch are pretty low — it's not nothing.
In a modern lever watch running at 28, vph, that scraping friction happens eight times per second. That is ,, times per year In five years, that's 1,,, times You need oil, and if the lever has an Achilles' heel, it's that it needs oil on those impulse surfaces, and oil, even the best, breaks down after a while. Still, the lever is tried and true. Think about it — just about every watch on Earth except for some exotics, and of course, Omega, which we'll get to in a minute uses a lever escapement.
Even in watches with silicon pallets and escape wheels, the basic principle is the same. It is a somewhat humbling reminder to not get too up on your high horse about your watch — that you blew the kid's tuition payment this year on is using exactly the same basic mechanism as a Seiko 5.
Okay, I'm being a little rhetorical there — after all, there are enormous differences in craft and execution, across the board — but given how many hundreds of escapements have been tried over the centuries, it is a remarkable testimony to the lever escapement that it is, if not the only game in town, still the biggest after so many centuries. Rolex is a funny beast.
A lot of what they patent never sees the light of day in actual products, but they do put a lot of time and research into making improvements on basic timekeeping technology, and one example of their efforts is the so-called Chronergy escapement. The Chronergy escapement is basically a Swiss lever but with some modifications intended to improve performance and efficiency.
It was first introduced in the Day-Date 40mm, in , in the then-new caliber Without escapement, a watch cannot tick. Read: Tourbillon Watch Recommendations for You. The power from the mainspring is transmitted through a set of wheels to a regulating component called the balance. Between the balance and the wheel also known as the gear train , there is an important part of a watch called the escapement. Without it, the force from the gear train will be released uncontrollably.
As the balance wheel returns to its central position, it once again moves the pallet fork, which in turn causes the exit pallet to lock the escape wheel in place. This process is repeated over and over again, with the continual movement of the balance wheel—kept in motion by the balance spring—causing a regular locking and unlocking of the escape wheel, regulating the release of power from the mainspring to the rest of the movement. Watchmaking is all about innovation and improvement, and over the years, other escapements—such as co-axial movements—have been developed by enterprising watchmakers.
The lever escapement, however, will remain a critical turning point in horological history. Still scratching your head? Never fear! We use cookies and similar technologies to help personalise content, tailor and measure ads, and provide a better experience. To change preferences or withdraw consent, please configure your cookie settings.
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