Feature: How Does A Mechanical Movement Work?
Breguet 7027 Tradition
.While the sun and moon have long been used as a basis for tracking time, it's the invention of the escapement that really started the modern idea of accurate timekeeping. An escapement, quite simply, is a device that manages a constant energy source into uniform pulses, whether that energy is the flow of water, the coil of a spring—or whatever. In an hourglass, for example, the bottleneck that restricts the flow of sand from the top to the bottom can be considered a very rudimentary form of passive escapement. It quite literally controls how each grain 'escapes' from the top half into the bottom.
The Breguet Tradition 7027 is the perfect watch to see how a movement works
The earliest known example of an escapement dates back to the ancient Greeks, to engineer Philo of Byzantium. Philo was a smart man, dabbling in cryptography, automatic weapons—and washing machines. While the escapement itself cannot be attributed to him, in the design of an automatic washing device, Philo likens his mechanism to that of a clock, suggesting it was already a commonplace invention.
It took over a millennium for the water clock to be superseded by something better: the verge escapement. This was the first example of a truly mechanical timekeeping device, and it shaped the future of watchmaking, utilising the scientific principle of conservation of momentum.
Momentum is simply the combination of mass and speed. This means that something with low mass—like a pebble—and high speed can cause the same amount of damage as something with high mass—a rock—and low speed. That momentum is conserved simply means that it doesn't disappear; while the pebble or rock may be stopped in their tracks, the object they hit will gain whatever momentum they lose. Snooker is the perfect visual example of this. This conservation of momentum is the principle behind the operation of an escapement, but we'll talk more about that later.
Everything that's normally at the back has been moved to the front
Two hundred years after the verge escapement was invented, and Galileo developed a much more accurate escapement that operated with a pendulum. As a testament to Galileo's brilliance, and because he was blind, he designed the mechanism purely in his mind, describing it to his son to draw out.
The bulk and sensitivity of a pendulum clock aren't conducive to portability, however, so the invention of the mainspring wasn't far behind. Clocks became portable clocks, which became pocket watches. The escapement was then refined in the 17th century with the invention of the balance wheel—and that's pretty much the movement we have today.
Let's see how it all works with this Breguet 7027 Tradition. Quite strikingly, the 7027 has had its dial shrunk to almost unreadable proportions—but opening it all up is a price worth paying when you see what Breguet's done with the place. While it appears to be in a state of chaos, it's on closer inspection that it becomes clear that the bulk of the movement has been transferred to the front of the watch so it can be properly appreciated and understood. It's the perfect piece to visualise the operation of a watch.
The dial has been shrunk to fit most of the movement in on the dial side
Smack bang in the centre is the mainspring, and this is where the power is stored. It's wound by the crown, with the power reserve—of which the 7027 has two, one modern, one traditional—displaying the amount of time left until it's completely unwound again.
But why doesn't the mainspring simply unwind in one great explosion of power? That's where the escapement comes in. The power from the mainspring makes its way along the gear train to the escape wheel, the first element of the escapement. Look closely and you'll see how the escape wheel pushes the next component along—the jewelled pallet fork. This is the conservation of momentum we spoke about earlier.
The pallet fork pivots on its staff, locking the escape wheel. This is what prevents the mainspring unwinding in one go. But how does the escape wheel unlock again to progress forward? Well, as the pallet fork pivots, it also knocks the sprung balance wheel at its jewelled impulse pin. The balance spring is coiled, and the momentum is reversed as it uncoils. This returns the momentum to the pallet fork, pivoting it back again, unlocking the escape wheel to push the pallet fork and start the whole process over.
The movement can then be followed from the mainspring through the gear train to the escapement
It's the pause while the balance wheel spins back and forth that gives you a beat, that regulates time—and it's been four millennia in the making.
It took some of the greatest minds thousands of years to develop what we know today as the mechanical movement. It's easy to see why it's so appealing; yes, it can't rival the accuracy and performance of a modern computer or atomic clock, but its refinement and elegance more than make up for it. The revival of film cameras, record players, classic cars and mechanical watches shows that, sometimes, perfect isn't always perfect. Sometimes things just need a little pinch of that universal chaos to get them right.
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