Spring and Barrel

Know the history of the barrel spring

The first mechanical clocks used weights suspended from pulleys. The brilliant stranger who first thought of replacing this cumbersome motor system with the force of a mainspring will undoubtedly enjoy a special honour in the history of pocket clocks. Before the invention of the clockwork, the idea of a portable timepiece simply could not have been imagined. Springs were first applied to clocks in a very primitive form, and cheap clocks still do. It is wound directly around a shaft, and its expansion is limited by the columns. The first use of springs in clocks is thought to date back to 1435.

For watches, the first application is set between 1508 and 1510. The French claim that the watch first appeared in Blois, the famous watchmaking centre, around 1509. At about the same time, the Germans claimed P. Heinlein's credit for the discovery. While the power weight ensures a constant power, the spring on the contrary provides an irregular power depending on whether it is fully armed or more or less disarmed. This defect had a disastrous effect on the performance of the first watch. The weight of the string wound around the drum was the ancestor of the clock motor. The first mechanical clock with a weight almost certainly dates back to 1300.

The Germans invented a cam attached to the barrel shaft, on which a spring was pressed, the purpose of which was to regulate the power of the engine more or less. This device, called stackfreed, was replaced by a fusee, a bell-shaped drum around which a hose is wound, itself wound around a drum containing a spring.

The barrel spring in modern watches today

In modern watches, the mainspring provides 36 to 40 hours of autonomy. This means that there is a power reserve of 12 or 16 hours which is not used. But if this power is lost, it still offers an advantage because the most constant part of the driving force is used.
The force required for a watch spring is very large. It can even be said to be too great, because it always exceeds the elastic limit respected by mechanics.
The need to house the strongest possible springs in the smallest possible volume justifies this departure from the laws of mechanics.