Transmitting torque from the barrel to the escapement is the main responsibility of the gear train. When you look at it, it has multiple wheels and pinions properly arranged for its intended function. It is arranged as a multiplying gear train to achieve a faster output rotation rather than input rotation. Just like a bicycle, as the pedal revolves, the rear wheel’s revolution is times faster. A single pedal will create many revolutions of the rear wheel.
The relationship of the speed of output and the torque is inversed. The higher the output speed, the more the torque decreases. In the concept of the bicycle, this is supported by the fact that you need to pedal harder when the gear is higher which is why there is a higher torque in the first wheel as compared to the last. It is important to observe extraordinary care in the gear train to achieve a lower friction. This is to avoid torque loss. The most common means to minimize torque loss is to use sapphire jewels at the pivots. In addition, polishing and hardening the pinion leaves should also be done.
There are commonly four wheels in a gear train. First is the center wheel which is powered by the barrel. It rotates once an hour and is usually located at the center of the movement. There is also a second wheel and third wheel. The third wheel rotates once in a minute. Lastly is the escape wheel.
The gear train serves as the transmitter from the barrel to the escapement. Without the gear train, the watch would only display a short period of time. Multiplying output rotation allows the watch to run for hours. It is also the main player in segmenting the hours, minutes, and seconds of the timepiece. All in all, the gear train is vital in the totality of the watch. Without it, no timekeeping device can be made.
Featured Image Credit: hautehorlogerie.org