How Does an Automatic Watch Work?

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First of all, let’s describe what we mean by an ‘automatic’ watch, as, in these days of Smart Watches, there may be some confusion. Let’s go back in time to when watches were first invented, some time back in the 1500s. It was the time during the introduction of a mechanism known as the pocket watch, which allowed a clock to be powered by a spring and was miniaturized to be carried in one’s pocket. 

I’m lucky enough to have inherited a pocket watch which my grandfather, a simple farmer, must have carried and displayed with pride. It still works, a tribute to the craftsmanship with which it was made back in 1855. 

Pocket watches, the design of which evolved over the centuries, were then cutting edge technology in their time. It evolved in a more fashionable term which is the wristwatch during the first World War (1914-1918). The wristwatch was then patronized by many as it is more convenient to glance at your wrist than fish around in your pocket just to check the time.

The Invention of the Automatic Winding Mechanism for Watches

In the 1770’s a fellow by the name of Abraham-Louis Perrelet devised an ingenious solution to powering the pocket watch. As you may know, until this point in time, all pocket watches needed winding each day to coil the mainspring. 

This process would ultimately unwind over the next 24 hours or so, providing power for the hands to turn, telling you the time. In some cases, a bevel protruding from the watch was connected to the winding mechanism. 

In the case of my grandfather’s watch, a tiny key is required to correctly wind the watch and care must be taken not to ‘overwind’ the mainspring. 

Perrelet was perhaps a forgetful person (I’m speculating here) and felt he could save himself from having to remember to wind his watch each day. 

So, he devised a mechanism best described as a part-circle weight, free to rotate around its axis. The movement of the weight as a result of the movement of the human watch owner provided the energy to wind the mainspring and hence power the watch. 

Only if you were having a particularly lazy day was it even necessary to add further energy to the mechanism by winding. Unfortunately for Perrelet (assuming he had hoped to make his fortune from this invention – again, I speculate), this method of winding one’s watch, which gave rise to the term ‘self-winding’ did not really take off in his day, perhaps simply because the pocket watch is less inclined to move with the human to quite the extent that the wrist-worn watch is.

The Evolution of the Wrist Watch in the 20th and 21st Centuries

Today, the word watch summons an image of a small device worn on the wrist. While fashions did at one time dictate that a ladies watch should be very tiny, less than half an inch across in some cases and the need for embellishments such as numerals on the face was disregarded, the tide has turned and now ladies will wear huge-seeming watches as long as they can also take selfies with them. 

As I’ve explained, the move from the pocket to the wrist was largely a practical move. (Nurses can still buy watches which are upside down and pinned to the breast in order to facilitate easy reading without any interruption of sterile practices) and one might assume that adoption of Perrelet’s brilliant system of the automatic or self-winding watch, so well suited to wrist-worn timepieces would be practically adopted overnight, but that was not the case. 

Perhaps the handed down learning of winding one’s watch every day needed a generation or so to disappear, but to my knowledge the self-winding watch did not really gain popularity until the 1930s, with the development and marketing of Rolex Perpetual, a flagship of the Automatic watch world and something every young man of my era hoped to own one day. In fact, I recall being instructed on how to tell if such a watch was real or fake, simply from the movement of the second hand which was perfectly smooth on the real thing and a little jerky in the fakes. 

Nowadays, most automatic watch mechanisms are made by ETA, which is a subsidiary of the Internationally-known firm Swatch. The quartz crystal watch was another marvel of the last century, requiring a battery to cause vibration of a crystal with such an exact frequency that it could be used to determine the passing of time. That is a whole separate story in itself, but it was a shortage of these piezoelectric crystals which caused the resurgence (perhaps the survival) of the mechanical automatic watch. 

For although some automatic watches may also be wound and some of them (my own Seiko included) also do contain batteries, the timing mechanism is still the basic clockwork design of timepieces from centuries before, only the source of energy or power to maintain the movement is ‘automatic’.

Further effects of fashion and the workings of the self-winding mechanism

Time marches on, though, and the beautiful and finely crafted wristwatches of yesteryear look like being replaced by ugly digital and now more beautiful ‘smart’ watches, on which you can choose how time is displayed and change it to suit your mood (not to mention, text and call your pals, take selfies and check your pulse and facebook page). The automatic watch still sells in huge quantities, as do quartz watches, however, the digital alternative is generally cheaper. This is a watch based on a chip – no moving parts. The best quality versions of all of the above though will likely continue to hold a place in the heart of the consumer. 

There is a new trend among quality watchmakers which allows the owner some insight into the workings of the automatic watch. While I have seen both my grandad’s pocket watch and my own beloved Seiko stripped down to the most basic parts during refurbishment, most people never see inside the watch they own unless they care to see how the battery is changed. As an aside, the automatic Seiko I own was bought on a flight from the UK to Canada in 1993 and has been refurbished due to the one time I took it diving without first checking that the bezel was screwed tight to the body. Repairs cost me near the original $600 price of the watch but I’m delighted to say it still keeps perfect time. So I can personally vouch for the efficacy of the design.

Automatic Watch

So, how exactly does this thing work?

As I mentioned above, Rolex developed the first truly commercially successful automatic watch, based on their design of a weight which was almost semi-circular and which could spin in either direction throughout 360 degrees. This allowed the mechanism to maximize the energy gained from any movement of the watch on a person’s wrist. This movement is translated to a ‘keyless works’ (remember grandad’s watch required a key to wind it?) via the usual cogged teeth one might expect to see in a clockwork device.

The keyless works transfer this power through a system of reduction gears which increase the torque until it is sufficient to tighten the mainspring – effectively ‘winding’ the watch. You can imagine how this works when the weight is spinning in the right direction. When it spins in the opposite direction a transfer gear wheel simply kicks out of place preventing the watch from ‘unwinding’ due to this kind of motion or a switching gear allows the power to be collected in both directions of spin.

The ratchet wheel or first wheel is directly connected to the main spring and on some watches, this can also be hand wound (say, if you took the watch off for a day or two and found it was not moving). A small ‘click’ spring prevents the ratchet wheel from backing off and releasing the energy of the mainspring all at once. The mainspring of course ‘wants’ to uncoil and is allowed to slip gradually through the mainspring Barrel instead. This is the primary drive mechanism which must be kept greased and teeth on the outside of this barrel engage the second wheel which engages the third and so on to gear the power back to, at the fourth wheel level, for example, one revolution per minute. 

This wheel drives the second hand, but it also drives the ‘Escape’ wheel which is the one, alluded to earlier, which really regulates the energy of the mainspring. In conjunction with a balance wheel, the escape wheel momentarily locks the movement of the watch while setting in motion the balance wheel, which, upon its return, unlocks the escape wheel for one more movement. The locking and unlocking of the escape wheel are achieved by a palette and the strange hook-shaped teeth of the escape wheel. It is engineered to perform this function in such a way that the timing can perfectly describe one second (for example, four ‘locks’ per second).

The Centre wheel, located centrally as you’d expect, is geared to rotate once an hour and of course drives the minute hand, further gearing to one-sixtieth of this speed drives the hour hand. Some of this will be apparent to you if you purchase one of these upscale automatic watches with a clear back which are so popular these days. 

I feel sure that if you do, this intricate dance of moving parts which has been so exquisitely fine-tuned over the centuries will provide you with a satisfaction and feeling of luxurious quality that no electronic gadget will ever provide you, and I’m equally certain that no firmware upgrade will ever be required and that your automatic clockwork or piezoelectric watch will last you for many more years than you’d ever expect a digital or smartwatch to. So much so, in fact, that you might also enjoy that old tradition of passing it on to your son or daughter one day.

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