The wheel train of a watch is a series of reduction gears designed to transfer energy from the mainspring to the escapement. It is comprised of several components that pass along the energy in order: the mainspring barrel (technically the 1st wheel), the center wheel & pinion (the 2nd wheel but also not called by that name), the 3rd wheel & pinion, the 4th wheel and pinion, and the escape wheel & pinion. The wheel is brass; the pinion is the smaller gear: Here's how the center, 3rd and 4th wheel mesh in place: The train helps govern the torque of the mainspring and allows the power to be spread out over a long period of time by releasing it in small increments. The size of and number of teeth on each wheel & pinion is determined by its function. That individual ratio must also be part of the larger equation where 1 revolution of the center wheel occurs for every 18,000 vibrations of the balance & hairspring assembly. Of course, the ratios will change if the frequency of the movement rises to a higher bph. The center wheel's pinion (2) is pushed by the mainspring barrel (1). It causes the center wheel (3) to make 8 turns for each 1 turn of the uncoiling mainspring. The minute hand is attached to the top of the center wheel's axel. The rest of the wheel train's ratios are calculated to cause the center wheel to revolve once every hour provided that the escapement controls the release of energy in correct timing. The center wheel (3) meshes with the 3rd wheel's pinion (4). For each rotation of the center wheel, the 3rd wheel revolves 8 times. The 3rd wheel (5) meshes with the 4th wheel's pinion (6). For every revolution the 3rd wheel makes the 4th wheel spins 7.5 times. This means the 4th wheel revolves 60 times for each rotation of the center wheel. The 4th wheel has the second hand attached to the end of it's pivot on a watch that has a subdial seconds display. The 4th wheel (7) meshes with the escape pinion (8). It causes the escape wheel to turn 10 times per each rotation of the 4th wheel. Technically, the escape pinion is the last piece of the wheel train and the escape wheel is part of the escapement. To finish the math, the escape wheel (9) has 15 teeth which meet the 2 pallet jewels. Each pallet jewel is associated with one directional oscillation of the balance & hairspring assembly. Simplifying the equation: 1 center wheel turn X 8 3rd wheel turns X 7.5 4th wheel turns X 10 escape wheel turns X 15 teeth on escape wheel X 2 pallet jewels= 18,000 The rhythm of the balance & hairspring assembly regulates the rate of the flow of energy. The interval needed to complete each vibration (or beat) in one direction is the time between ticks. If the balance & hairspring is called the heart of a watch and the escapement is the brain, then the wheel train is the circulatory system. All of a movement's other functions and complications are supplied with power through additional branches off the basic train. Thanks to Steve / N2FHL for his assistance!
Very much enjoying your posts from horology 101. Do you have one about jewels and what they do/how they work?
There are two: https://omegaforums.net/threads/horology-101-jewels-part-1.76575/ https://omegaforums.net/threads/horology-101-jewels-part-2.76577/