Manual wind mechanical movements form the very core of watchmaking. The manual wind mechanical movement was the first watch movement invented, and very few mechanical movements have removed the manual wind function since.
In the earliest days of watchmaking, mechanical timepieces needed to be wound by a key. This traditional prevailed until a mechanism was invested that could decouple the crown (the winding button normally on the right-hand side of the case at 3 o’clock) from the hands to wind the movement separately. This was called "the keyless work" and remains in most modern watches today.
The basic differentiator between a manual and an automatic movement is the fact that (like its name would suggest) a manual wind movement can only be wound by hand. Meanwhile, the vast majority of automatic movements can be wound by the movement of the wearer’s wrist thanks to an oscillating weight mounted on the back of the watch (though many can also be wound manually). There are exceptions, mostly from Asian manufacturers, but these are quite rare.
Winding a watch is easy, but you must remember to wind a manual watch regularly to ensure it has enough power to keep running at a good rate. Every manual wind watch has a power reserve. This is the number of hours (or maybe even days, weeks, or months) for which the watch will be able to run if it has been fully wound. Generally, the minimum for an automatic watch is around 38 hours, although most manual winds aim for above 40 hours to ensure it can continue working, even if the wearer is not able to wind it as regularly.
For example, a power reserve of 46 hours (which is the same as the ubiquitous ETA 6498-1 movement, a large, basic caliber used as an entry-level mechanical movement in thousands of watches) means you have the best part of two days between essential winds. However, it is advisable to wind your watch once a day so that timekeeping inconsistencies from waning power from the mainspring do not manifest. Generally, unless your watch has a power reserve significantly over 48 hours, it is wise to choose a time to wind your watch once a day.
Winding the watch more than necessary isn't necessarily detrimental to the watch. However, it can subject the internal components to more wear and tear then is essential. Today's technology does make it very difficult to overwind a wristwatch, due to the gearing ratios involved and the size of the crown. It is certainly possible to overwind the watch, but it normally takes either extreme strength, conscious action, or complete ignorance to achieve.
When you wind the crown by turning it clockwise, a series of wheels engage with the barrel and it starts to turn. Within the barrel is the mainspring, which is the power source of the watch. The mainspring generates power from being coiled tightly around the central post on which the barrel pivots. This post is called an arbor. The mainspring is constantly trying to expand, but is being prevented from doing so by an intelligent braking mechanism known as the escapement. The force created by the mainspring trying to expand drives the wheels forward and turns the hands of a watch. The escapement allows that power to drip feed to the hands at the perfect increments so that time can be tracked.
The wheels that sit between the mainspring in its barrel and the escapement are known as the gear-train. The hands are fitted to these wheels by the pinions (the central stalk of a wheel on which it pivots). These pinions extend through the baseplate of the watch and up onto the dial where the hands can be affixed as one of the last stages of assembly.
A balance wheel, topped by a breathing spring known as the hairspring or balance spring, vibrates backward and forwards (two vibrations of the balance wheel, so out from and back to a fixed starting point is known as one oscillation). The balance wheel can be geared to vibrate at different frequencies. The most common frequency in modern watchmaking is 28,800 vibrations per hour (vph), but the ETA 6498-1 mentioned earlier, vibrates at just 18,000vph. One often finds that manual watches are likely to have lower operating frequencies than automatic watches, simply because fewer vibrations equates to lower power requirements, which in turn results in higher power reserves, which are more important for a manual wind watch so it keeps on ticking.
In further Academy articles, we will build on the other components that make the magic of mechanical watchmaking possible.