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Watch Guide / Mechanical Watch Movements

The Mechanical Watch

Watchco attempts to explain the inner workings of mechanical watches

The horse and buggy are no longer a primary mode of transportation, nor is the steam locomotive. The typewriter has come and gone and the incandescent light bulb appears to be on its way out. The telephone has fundamentally changed. In less than 100 years the airplane has progressed from the Wright Brothers to the F-22 Raptor. Great inventions and new technologies have come and gone, outliving their usefulness, or surpassed by newer technologies. Throughout all this, the basic design of the mechanical watch - now more popular than ever - has changed very little.

Sure there have been refinements along the way, but the essential technology is the same. Gears and pinions turning in jeweled bearings, a mainspring, balance wheel and an escapement, all held together by a main plate and bridges turn hands which display the hour on a dial. It could be called the perfect machine, and its longevity during a period of great technological advance is a tribute to the perfectness of the concept. To the watch lover, a mechanical watch is not just a watch.

Let's explore some of the inner working of a common mechanical movement and discover what might account for the huge differences in price and quality among mechanical watches today.

A mechanical movement is powered by a mainspring. Before the mainspring was invented in the 15th Century, clocks were powered by hanging weights. You've probably seen wall clocks, or cuckoo clocks with weights suspended from chains coming out of the bottom of the clock. As gravity pulls the weight down, gears are turned powering the clock. Of course this requires the clock to remain in an upright, stationary position.

The mainspring changed everything. Coil shaped, and placed inside a cylinder called a barrel, the mainspring can be tightly wound to provide power to the watch. More importantly, the mainspring continues to work whether it is in a clock on the wall, or on somebody's wrist.

In a hand-wind movement, the mainspring is wound by turning the crown, or winding-stem of the watch. That is the small knob on the outside of most watches that is also used to set the time.

In automatic watches, there is an oscillating weight, visible through the see-through case backs of many automatic watches, that spins around as you move while wearing the watch. As it spins, it moves a series of gears which wind the mainspring - automatically.

The barrel turns on an arbor called the barrel-arbor. The outside of the barrel is ringed with teeth, which engage the pinion of the center wheel. As the mainspring loosens itself over the course of several hours - 42 hours is now pretty common - it turns the center wheel which conveys power through the third and second wheels to the escapement.

The escapement lies at the heart of any watch. It is the most important element. The type of escapement found in the large majority of mechanical watches is called a lever escapement , or Swiss lever escapement. It consists of a balance wheel and hairspring, a lever with two pallet arms and an escape wheel. As power is transferred from the mainspring through the movement, the escapement regulates the speed at which the movement works.

Without an escapement, a movement would simply deplete all of the energy stored in the mainspring within a few seconds. It would run extremely fast while the mainspring was tightly wound, and then slow down as the mainspring loosened.

However, when the escape wheel is turned by the series of gears extending from the mainspring, it is stopped and released, stopped and released by a lever attached to the axis of the balance wheel. This gives the movement its characteristic ticking motion. The lever has two pallet arms which alternately engage the escape wheel. The movement of the escape wheel is both restricted by the balance wheel and lever mechanism, and provides force to the balance wheel. Because of the regulating effect of the escapement, the energy provided to subsequent parts of the movement is nearly perfectly constant. The hairspring can be tightened or loosened to adjust the rate. See the following illustration.

From the escapement, precisely regulated energy turns a series of gears which perform functions such as displaying the time and date on the dial of the watch.

You may have heard about "jeweled movements", but aren't sure what that means exactly. Jewels, usually synthetic rubies are used in a watch movement to reduce metal-on-metal friction. At several points in a watch movement, instead of allowing the metal axel of a gear to turn inside of metal, which could wear down over time, the axel instead turns inside of a ruby cylinder inserted into the part of the plate or bridge where the gear turns. This arrangement is extremely resistant to the effects of friction and if properly lubricated at regular intervals can prolong the life of the movement almost indefinitely. While only a few jewels are necessary in most mechanical watches, many manufacturers will boost the number of jewels in order so that the watch will be perceived as more valuable, but the fact is that extraneous jewels in a movement don't really serve any function, and don't really add any real value.

Although there are a large number of companies producing mechanical watches nowadays, there really isn't much diversity in terms of movements, in fact most manufacturers excepting the high, high-end manufacturers, get their movements from only a couple of different suppliers.

The most common of these is ETA. ETA is a Swiss movement company that supplies movements to most Swiss watch companies, large and small, low and high-end. ETA movements are well made, durable and proven over years and years of use. ETA movements are found in affordable Swiss brands such as Accutron Watches and Swiss Army Watches as well as high-end brands such as Omega. Many high-end brands append additional functions onto basic movements such as dual-time, or GMT, alarms, repeaters, tourbillons, and perpetual calendars. These functions are called "complications". The can be extremely complex and can add a considerable amount to the cost of the watch. Tourbillons, perpetual calendars and minute repeaters are often priced at more the $100,000.

Well-made Swiss watches carrying very good ETA movements however, don't need to be expensive and can be found in the sub $500 range. Properly maintained, one of these watches can last a lifetime and rival the quality of much more expensive brands. As with designer clothing, you pay a lot for a name when you buy a high-end watch.

While better known for electronics, Japanese manufacturers such as Seiko and Citizen also produce watches with mechanical movements. Many Seiko diving watches carry automatic movements and Citizen, through its subsidiary, Myota, supplies automatic movements to many other manufacturers. While not perhaps as well-regarded as ETA movements, these movements are of very good quality and are a great value for anyone looking for an affordable automatic watch.