A lot of the time the features you see as highly touted ones in upper end modern mechanical watches are features you kind of wonder about, in terms of real advantages they offer to the owner (at least when it comes to improvements in keeping time, which after all is what a watch is supposed to do). There are all sorts of examples of this â movement plates made of exotic materials, movement gears made of exotic materials; obsessively refined modern versions of hundreds-of-years old complications, and so on. The truth is that we now know that if you want a solid, reliable, reasonably accurate watch, a modern industrially made, automatic watch with a lever escapement (which is in one form or another about 250 years old, by the way) is very hard to beat, and we’ve largely given the hardscrabble work of pursuing bleeding edge precision up to nuclear scientists coaxing one second per billion years’ accuracy out of atomic clocks.Â
However, we still have with us some exotic leftovers from the days when tweaking the shape of a metal spring could mean a gain in precious fractions of a second’s deviation per day in, say, a marine or a pocket chronometer. One of those relics are exotically shaped balance springs; nowadays, in work-for-a living wristwatches, these generally come in either a variation on Nivarox, or in silicon (or Rolex Parachrom) and in one of two forms: flat, or a Breguet/Phillips overcoil. However you do still also see, these days, exotically shaped balance springs in both cylindrical and spherical flavors (Montblanc is one example; Jaeger-LeCoultre another) and as we’ll see from these two watches from Girard-Perregaux, these did not come from nowhere.
A Very Early GP Pocket Watch From Circa 1860, With A Spherical Balance Spring
This is an extremely interesting watch on several counts. First of all, assuming it was completed in 1860, (as the GP museum tells us) Girard-Perregaux was only four years old; Constant Girard established the firm of Girard & Cie in 1852 in La Chaux-de-Fonds. The dial reads “Girard & Comp’y London” and while at first you might confuse this for Garrard & Co., the latter (and former Crown Jeweler) is an equally venerable but totally unrelated firm. As it turns out, Constant Girard maintained a small but respectable shop in London in the mid-19th century, which in addition to selling directly to consumers, was an export center for the company. Several Swiss firms at that time, and earlier, preferred to ship watches to London for export to more distant lands; for instance, for many years, Bovet maintained an office in London as the liason to their (considerable) presence in Guangzhou (Canton).Â
An English-made watch of the time would have had some similarities to this GP but also, some significant differences. Generally, an English watch would not have the bar-shaped bridges you see in the GP, or for that matter any bridges; it would have had a 3/4 plate construction, with everything but the balance more or less out of view. However, this watch does share, with high grade English watches of its time, the presence of a chain-and-fusÃ©e. Here you can clearly see the fusÃ©e cone, and the chain wrapped around it. You can also see the chain wrapping around the actual mainspring barrel.
Nowadays we’re likelier to be familiar with the fusÃ©e and chain from its presence in (generally very high end) modern watches (the Lange & SÃ¶hne Richard Lange Pour Le MÃ©rite, for instance) but obviously they go back several centuries further than that, and even when the lever escapement had made them much less necessary than they were for the earlier verge escapement (the first known mechanical clock escapement, and one that is super-sensitive to even the slightest change in mainspring torque) watchmakers looking for the last bleeding edge in accuracy still used them.Â
The way they work is pretty simple. This particular GP was wound and set with a key. The key has a socket that fits over the square steel peg at the center of the fusÃ©e (through an opening in the case-back. In one of the Sherlock Holmes stories, Holmes deduces that the owner of a watch had likely been a drinker, as innumerable scratches on the gold of the case around the winding aperture showed a trembling hand). Turning the key winds the chain onto the fusÃ©e cone, and off the mainspring barrel. As the barrel unwinds, it pulls the chain back off the fusÃ©e. At the base of the fusÃ©e you can see a toothed gear; this is the “great wheel” which is the first gear in the actual gear train. As the great wheel turns, it sends power down the gear train to the escape wheel and balance.Â
The shape of the fusÃ©e cone ensures the mainspring has the weakest mechanical advantage when it’s fully wound, and the greatest when it’s reached the end of its power reserve. The whole thing is like a ten-speed bike: the pedals are the mainspring barrel; the chain is â well, the chain; and the fusee is like the stacked gear wheels on the rear hub of the bike. You use the smaller rear gears for hill climbing because you have a better mechanical advantage, and the larger rear gears for running on flatter terrain.
By the way if you think a sec you’ll see a problem with the fusÃ©e; when you wind the chain back onto the fusÃ©e as you wind the watch, there’s no power going to the gears, so the watch stops. To address this John Harrison invented so-called “maintaining power” â basically, a small subsidiary spring inside the fusÃ©e cone that keeps the great wheel at its base under torque while you’re winding the watch.
As we jump from gear to gear down the “going train” (which is hifalutin’ watchspeak for the gears between the mainspring barrel and the escapement) we eventually reach the escape wheel. This is the last gear in the train; the purpose of the train is to take the slow rotation of the mainspring barrel and turn it into the fast rotation of the escape wheel. The escape wheel is responsible for keeping the balance going. In a normal lever watch it does this indirectly, through a tiny steel lever it flicks back and forth to push the balance on each swing. It’s a good arrangement, but the lever escapement has a well known problem: it needs oil where the lever contacts the escape wheel. And as anyone who’s ever owned a bike knows, oil gets gummy if you wait long enough.
Our 1860 GP chronometer represents an alternative: it uses a detent escapement. In a watch with a detent escapement, the escape wheel teeth don’t work through a lever; they push the balance wheel directly as they move past it. This is much more efficient (a lever means more lost energy) and you do not need oil on the escape wheel teeth, so the rate of the watch is more stable over longer periods (though you still need to clean and oil the watch overall from time to time; the pivots of the going train need oil, and so on. Plus there is always the inevitable incursion of what watchmakers call, “general dirt”). This watch uses a particular type of detent called a pivoted spring detent escapement, but back when the watch was made, any detent escapement was also called a “chronometer escapement” which is why it says “Chronometer” in letters you can see a block away on the inner caseback.Â
The detent itself is a razor thin blade of metal that blocks the escape wheel, which sits against it under tension from the upstream gears of the going train. The balance gives the detent the tiniest flick as it swings; the detent moves aside; the escape wheel turns just far enough to give the balance a push at its hub; and then the detent pops back into place and stops the escape wheel again, before it can advance more than one tooth. Lather, rinse, repeat. The detent escapement is near ideal, but it does have a bad habit: jolt it hard enough, and the detent might be jarred hard enough to let the escape wheel skip forward when it shouldn’t. However, its advantages outweigh its disadvantages in watches and clocks that lead a fairly un-jolted life, like pocket watches and marine chronometers.
So let’s get to it: the spherical balance spring. The balance spring of a watch is arguably the single most important part for ensuring rate accuracy; so much so, that it’s sometimes said a watch is only as good as its balance spring. Here’s why. Every watch or clock that ever existed, matter how simple or complicated, has two basic elements: an oscillator, and a mechanism that counts the oscillations and keeps the oscillator swinging. A pendulum clock has a pendulum for an oscillator (a watch has a balance wheel; a quartz watch has a quartz crystal) and the movement simultaneously pushes the pendulum gently to keep it swinging, and counts the number of swings. Stick some hands on the pivots of a couple gears so you can read the time, and darned if you don’t have yourself a clock.
Now why is a pendulum clock capable of incredible accuracy? (And they can be incredible accurate; the best ran to within a second or lessÂ per year.)Â Basically any oscillator has a “perturbing force” (the push) and a “restoring force” (whatever pulls the oscillator back to neutral). For a weight driven pendulum clock, the power for the push comes from a weight attached to a cable or chain wound around the pivot of one of the gears. The pull back to neutral â the restoring force â is gravity. And here is the really key point: how hard gravity pulls back, is exactly proportional to how hard the pendulum is pushed. (Think of pushing a swing: the harder you push it, the further it swings, and the harder it’ll clock you in the face as it swings back.) This means the pendulumÂ should always take the same time to swing irrespective of how strongly or weakly you push it. That property is called isochronism (this is not actually 100% accurate, but it’s a good approximation for understanding the basics).
For a watch with a balance, it’s a little different: the push comes from the mainspring; and the restoring force is the balance spring. The poor balance spring has a totally impossible job: to be as unvarying in restoring force, as gravity. Alas for the balance spring, it is not the Earth’s gravity â not a gigantic, incredibly stable distortion in spacetime caused by the presence ofÂ 5.972 Ã 10^24 kg of iron and rock (and people and dogs and cats and fast food restaurants) hanging in orbit around the Sun. It’s, you know, a little spring. It’s fragile; it’s affected by heat, and cold, and magnetism, and for all I know harsh language, so for it to do its job, you do everything you can to give it a fighting chance. One way to do this is to shape its inner and outer attachments so as to minimize any forces on the balance that would tend to interfere with isochronism. That’s what the Breguet/Phillips overcoil is for â and the spherical balance spring.Â
Who came up with this beautiful but slightly wacky idea? As it turns out the spherical balance spring was the brainchild of someone with a considerable brain. It was invented, so the 1897 edition of Abbott’s Antique Watches And How To Tell Their Age tells us, by one FrÃ©dÃ©ric Houriet, of Le Locle, in 1810 â fifty years before this watch was completed. Houriet was born in NeuchÃ¢tel but he studied watchmaking in Paris; he was a friend to Abraham-Louis Breguet, and as well, he was one of the first makers of tourbillon watches; his life is the subject of Jean-Claude Sabrier’sÂ FrÃ©dÃ©ric Houriet: The Father of Swiss Chronometry.
The spherical balance spring is sort of an overcoil on steroids. At the lower end, it’s attached to the hub of the balance by a tiny collar called the collet. At the upper end, it’s attached to the stud, which is the projection with two screws on top, just behind the regulator (which has two pins through which the last coil of the balance spring passes). As the balance swings, the spring expands and contracts, but a flat spring will do so asymmetrically as it breaths. This produces unwanted lateral force on the balance pivots. The spherical balance on the other hand, should “breathe” perfectly concentrically â aiding in improved isochronism. That’s the idea, anyway.
A Japanese sword expert once said (I’m paraphrasing) that a sword can be beautiful, but the question is also, and always, “does it work?” The spherical balance spring, as it turned out, was one of those things â those many things â in the history of horology where something that was really gorgeous, and for which its inventor had high hopes, turned out to be more trouble than it was worth. A 1940 edition of Britten’s describes the spherical balance spring as a “pure freak” and in Watchmaking, Dr. George Daniels (who very much liked to say so when he saw what he judged to be vanity in watchmakers) writes: “The spherical balance spring was sometimes used by Swiss chronometer makers … such springs offer no practical advantage … but are much admired by some watch collectors, who love craftsmanship the more if it offers a suggestion of extra difficulty of accomplishment.”
Be that as it may, there’s something incredibly moving about this 157 year old machine. It was made at a time when a lot had been figured out but a lot hadn’t, and when people who made this sort of thing were really at a crossroads, and willing to take chances that weren’t just about surprising rich connoisseurs at trade shows once a year or helping them show off; there were life and death stakes riding on what we now vacuously call advances in horology.Â
Dr. Walt Odets once wrote that watches are a near-unique combination of precision, craft, and functional beauty that’s found almost nowhere else â he mentions antique medical instruments. We can all thank god watches like this are less terrifying than trochars, bone saws, and dilators, but the point is well taken, and when you look at a watch like this, which reaches as hard as any watch ever made for the elusive prize of accuracy, you’re also looking at a combination of obsession with precision, and pride in craft, that you just don’t find very often in watchmaking today (not that, to be fair, it was all that common in 1860 either).Â
Houriet’s invention was a brilliant, if ultimately unfruitful, burst of intuition in its day, and though it serves no practical purpose in general modern horology, it, like mechanical watchmaking itself, still lives on as a source of real intellectual enjoyment and aesthetic pleasure. Ain’t nothing wrong with that.
Stay tuned for part 2; ten speed bike image by Ukexpat via Wikipedia Commons.