Balancing Time

The mechanical heart of the wristwatch is a delicate affair, requiring poise and balance. In the second part of our series on escapements, we take a closer look at the balance wheel

- Ashok Soman

In our story last issue on the balance spring – literally the beating heart of the mechanical watch - it might seem like this component does all the heavy lifting, as far as the back-office business of timekeeping goes. As any watchmaker will tell you though – and a good number of watch brand CEOs too – there is little point in talking up a new balance spring if one does not also address the balance wheel, and indeed the lever that impulses the system. In this story, we’ll be looking mostly at the balance wheel itself, with a few forays into the history and workings of verge, détente and Swiss lever escapements. As for the lever or pallet fork, it will have to wait for another issue.

We begin this story where the last ended – on the note that balance wheels and hairsprings need to function together. The best way to understand this is to think of the relationship between the mechanical wristwatch and the pendulum clock. Just as the pendulum is the regulating organ of the clock, the balance and balance spring perform the same function in the wristwatch. That means the balance and balance spring have to approximate the effects of gravity. Our returning protagonist for this introduction is none other than Dutch physicist Christiaan Huygens. You will recall that Huygens pioneered the balance spring (perfecting it in 1675) and the pendulum (of the aforementioned clock).

Curiously, the balance wheel appears to have existed before Huygens time – Huygens himself designed his balance wheel and spring system in the verge escapement style. Indeed, Huygens and other pioneers had been searching for the right component to create harmonic oscillation, and that missing piece was the balance spring. So the rest of the verge escapement – the Swiss lever system would only emerge later –existed prior to 1675.