Mar 8, 2024
Explained: Barrels, Mainsprings, and the Trade-off Between Power Reserve and Energy
Every mechanical watch employs at least one mainspring barrel as its energy source. When a watch is wound, the coils of the mainspring tighten, storing potential energy which is then slowly released through the gear train to the escapement. The mainspring is enclosed in a toothed barrel, essentially a drum covered by gear teeth. As a result the barrel is often considered to be the first wheel of the going train. Although one is the norm, two or even more barrels can be employed, typically to generate more energy. Double barrel movements usually feature two mainsprings kinematically linked in one of two ways: in parallel or in series. The number of mainsprings, energy stored, and power reserve are illustrated with equations (1), (2), and (3): As described by equation (1), the energy of a single barrel E is a function of its torque, angular discharge velocity and running time (autonomy). Linking two identical barrels naturally means having twice the energy, so 2E. By convenient association, equation (2) exploits the available energy to double the torque sent to the gear train, while equation (3) takes advantage of the total energy by doubling the running time. Parallel barrels The parallel arrangement of barrels embodies equation (2), which delivers twice the torque, increasing the energy available to run the movement (but not increasing the running time). Here two barrels unwind at the same time on a centre pinion connected to a second mobile of the going train. An embo...
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