Technical Perspective: Ultra Thin: What It Is, Why It Matters, And Who Does It Best (Part 2)

(Above, the Piaget 20P/Lassale Caliber 1200, the thinnest hand-wound movement ever made.)

In Part One of this story , we looked at the historical backdrop of ultra thin watchmaking – at why the most punctual watches were so thick, and how advances in watch movement design, combined with the evolution of modern clothing styles, drove the development of thinner watches. We likewise looked at how and why ultra thin watches became, not only fashionable, yet in addition came to be seen as a manifestation of the greatest level of expertise in watchmaking. Today we’ll investigate precisely why making a ultra thin watch is considered such a challenge – just as at a portion of the manners by which modern fine watchmaking houses continue to develop the art.

Above is the JLC type 849. This is one of the exemplary ultra thin movements of the twentieth century, and at 1.85 mm thick, it’s an excellent one to look at regarding why making thin movements is so challenging. There are a number of reasons it’s harder to make a very thin watch, and make it function admirably, than it is to make a thicker watch. Above all else, there’s the question of force. In the event that you want a watch to run precisely, it’s essential to have satisfactory force taken care of through the stuff train to the balance wheel, so it can sway at an enormous enough sufficiency (plentifulness simply means how much the balance swings, and is generally communicated in degrees) to maintain exactness across the working force reserve of the watch. The amount of force you can get from a mainspring is generally dependent on the tallness of the spring, and obviously, in a ultra thin movement there is considerably less stature available. That means that the movement must be made and amassed very cautiously and correctly, in request to avoid excessive loss of force due to friction.

Another reason it’s challenging to make a very thin movement is that generally speaking, you have to roll out significant improvements in movement design. For instance, in most watch movements, the mainspring barrel has two pivots – one running in a bearing in the mainplate, and the other in a bearing in the barrel connect. The JLC type 849 has what’s known as a “hanging” barrel (which was originally invented by Lépine, who you’ll recollect from Part 1 of this story ). A hanging mainspring barrel has no upper scaffold; instead, it runs only in one pivot: the one in the mainplate. The construction is inherently less steady and again, requires a ton of care in manufacturing and design to function admirably, however getting freed of the upper barrel connect saves valuable millimeters and is essential, in the 849, in bringing in the stature at under 2 mm.

Now how about we investigate a modern self-winding ultra thin movement. Above is the Audemars Piguet type 2121. (The easiest version of this movement is the type 2120, which overlooks the date wheel; the 2120 is 2.45 mm, and the addition of a date wheel adds to the stature only marginally, bringing it up to 3.05 mm.) This movement was first created in 1967 and at the time it appeared, it was the thinnest full rotor movement on the planet. Like the JLC type 849, it’s significantly different in many regards from a conventional self-winding movement, including its utilization of a hanging (or as AP calls it, a “suspended”) mainspring barrel. One of the most interesting highlights of the type 2120 and its variants is the suppression of the thickness of the oscillating weight, by moving a large portion of its mass to the fringe. The issue with this technique is that the weight isn’t very steady and in the 2120, there is an ingenious solution: the weight is upheld by ruby rollers on its underside, which run in the round rail you can see at the edge of the movement. 

An interesting element of the type 2120 and variants, is that regardless of its thin profile, it promptly underpins complications, like an interminable calendar. The following is the type 2120/2802, dial side – a ceaseless calendar movement, as seen in the Jules Audemars Perpetual Calendar.

Now, the type 2120 (which is utilized today by Vacheron Constantin as the type 1120 too) is simply the thinnest full rotor winding movement on the planet, however there’s a way you can manage even more stature, and that is to utilize a miniature rotor. The advantages of the miniature rotor are obvious – the winding weight is in the movement, not on it. The issue is that in light of the fact that the width of the winding weight is a lot more modest than it would be in a full rotor movement, there’s a significant leverage disadvantage, so again, it takes very cautious design, manufacturing, gathering and adjustment to get satisfactory performance. One of the most impressive achievements in the utilization of a miniature rotor in a ultra thin movement was the introduction by Piaget (a name that is for all intents and purposes synonymous with ultra thin watchmaking) in 1960, of the type 12P.

Caliber 12P is only 2.3 mm thick and even today, it would be an impressive engineering accomplishment – in 1960 it was an incredible accomplishment and did a great deal to get the reputation of Piaget as, in certain regards, the watchmaking firm when it comes to ultra thin watchmaking – and this when “elegant watch” would universally have been consented to be three things: thin, gold, and automatic.

Movements like the types JLC 849, the Piaget 12P, and the Audemars Piguet 2120/Vacheron Constantin 1120 presumably represent a certain reasonable cutoff on how far you can push ultra thin watchmaking using conventional materials. Endeavors to go even additionally didn’t end well, in general. 

Above is the 1.2 mm thick  late (and to a great extent unlamented) Jean Lassale type 1200, from 1976. In its time it was a technical wonder, and unfortunately, it was a mechanical technical marvel – thanks to the advent of quartz technology – delivered at an inauspicious time for a new mechanical movement of any kind, significantly less a little, incredibly thin, and incredibly risky one. By 1979 production (by Bouchet-Lassale, named for founder Jean Bouchet-Lassale) had stopped. The name Lassale was purchased by Seiko, who put it on the dials of ultra thin quartz dress watches, and the patents were purchased by Nouvelle Lemania, who continued the production of the hand-wound type 1200 (and ultra thin Lassale programmed type 2000) for a couple of more years before production eventually stopped. Piaget utilized the Lasalle 1200 as the Piaget type 20P, which is the version you see here; Vacheron Constantin likewise utilized it, as the Vacheron type 1160, and how they managed to get Geneva stripes on them involves wonder; you’d think there wouldn’t be any overflow metal left to remove.

Alas, for Jean Lassale, the issue wasn’t simply terrible timing; the movements were basically too thin to be dependable. Truth be told, they were meager to such an extent that they could be hopelessly harmed just by opening the watch case and at both Vacheron and Piaget, servicing the watches when they came in often meant essentially discarding the movement and installing a new one. The extraordinary thinness was achieved by putting all the train wheels in the baseplate itself – since there were no scaffolds, not only the mainspring barrel however all the pinion wheels also, were “hanging” and must be upheld in metal rollers. This is generally a poorly conceived notion for watch movements, as the bearings can introduce undesirable variations in force stream. Be that as it may, it was a strong design, if at last doomed.

In our next installment, we’ll look at how a portion of Lasalle’s thoughts, and other ingenious concepts, eventually proved to be fruitful, and how modern watchmakers are using cutting edge manufacturing strategies to take some initially unsuccessful thoughts and turn them into resounding successes.

Check out Part 1 here . Part 3 is here.

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