Ask a Watchmaker
There are definite differences between mechanical and quartz watches when it comes to timekeeping and accuracy. Mechanical watches rely on a mainspring as its power source (which can either be manually wound, or, for automatic movements, perpetually wound by the wearer’s wrist motion). Then, the mechanical movement relies on a complex system of gears, springs, and escapements to regulate the release of energy from a wound mainspring. In a Rolex watch, the balance wheel beats at 28,800 beats per hour or 8 beats per second. Visually, this is why the second hand of a mechanical watch moves about 8 times per second.
As far as accuracy, a quartz watch is 60 times more accurate than the finest mechanical watch. A mechanical movement could gain or lose a couple seconds per day, but a quartz watch only deviates by a few seconds per month. This goes back to how a quartz watch works. Basically, the battery passes its current/energy through a quartz crystal which has a set vibration frequency of 32,768 times per second. Then, these vibrations are sent through the watch’s circuit board which continually cuts this number in half (again, and again) until it reaches a precise one-second interval. Visually, this is why a quartz watch’s second hand only ticks 60 times per minute.
Energy efficiency between the two is a much harder metric to compare, but basically the mechanical watch relies on either the manual wind of a mainspring (by rotating the crown) or by self-winding through an oscillating weight which moves based on the wearer’s wrist motion. Whereas, a quartz movement relies on a small alkaline or lithium battery; time between battery changes greatly depends on the quartz movement and how fast it drains the battery’s energy.
What are some of the key differences in the physics behind a mechanical watch versus a quartz watch, particularly in terms of timekeeping accuracy and energy efficiency?
How does the escapement mechanism in a mechanical watch work, and how does it contribute to the accuracy of timekeeping?
First, there are a few different types of escapements in mechanical watches. The “Swiss lever escapement” is the most common variety, and is used in 98% of mechanical watches. The escapement is like the traffic controller of a watch. It makes sure that the back-and-forth swing of the balance wheel, which keeps time, is translated into the steady ticking motion of the watch’s gears.
Think of the escape lever as a gatekeeper allowing only one car (or tooth) at a time to pass through. As the tooth moves past one bump (or pallet jewel), the gate closes behind it, stopping the next tooth from moving. When the balance wheel swings back, it opens the gate again, letting the next tooth through.
At the same time, the energy from the escape wheel keeps the balance wheel swinging, so the watch keeps ticking accurately.
What role does friction play in the function of the watch, and how is it managed within the movement?
Friction plays a significant role in the function of a mechanical watch because it can slow down or even stop the movement of the gears, affecting the accuracy of timekeeping. In a watch movement, various parts rub against each other as they move, causing friction.
To manage friction, watchmakers use lubricants, which are applied to the moving parts to reduce friction and wear. These lubricants help the gears move smoothly and prevent them from wearing out quickly. However, too much lubrication an attract dust and dirt, leading to problems over time.
Additionally, watchmakers design the movement with precise tolerances to minimize friction. This means that the parts are manufactured to very tight specifications to ensure they fit together with minimal play, reducing the amount of friction generated during operation.
Regular maintenance, such as cleaning and oiling, is also essential to manage friction in a mechanical watch and ensure its continued accuracy and longevity.
Traditionally, whale and fish oils were used as early lubricants pre-1960s. These were much more likely to gum up and get sticky after a year; thus, the customer would have to get their watch serviced yearly. Synthetic oils used today greatly prolong the span between servicing and last 4+ years before breaking down. Further, the use of synthetics now makes the concept of “overwinding” a myth.
A quick note on the use of jewels in timepieces. A jewel count refers to the synthetic jewels used within the watch, usually made from synthetic ruby, sapphire, or diamond. These are integral to reducing the friction wear and tear within the movement. They are used as bearings or pivot points for moving parts of the watch, such as the gears and arbors. They also help distribute lubricants evenly, ensuring that the moving parts remain well-lubricated and reducing the risk of dry friction. By incorporating synthetic jewels into the watch movement, watchmakers can achieve greater precision and longevity, as these jewels contribute to the smooth operation of the watch over time.