One of the main defects in the earliest watches was the variation in the torque. The force of the mainspring was greater when fully wound than when it was almost run down. The time keeping of the watches fitted with the verge escapement was influenced by the force driving it, this was quite a serious problem.
However, the application of the fusee advanced the solution of the problem when the mainspring was invented (around 1450). The mainspring is the element that drives the watch and the fusee was a cone shaped pulley that was used together with a barrel containing the mainspring.
The mainspring would rotate a barrel which had a length of catgut (later replaced by a chain) wound on it, with the other end coiled around the fusee. With the correct proportioning between the mainspring and the fusee an almost constant torque was maintained as the mainspring was unwound.
Nowadays the going-barrel has superseded the fusee.
However, the application of the fusee advanced the solution of the problem when the mainspring was invented (around 1450). The mainspring is the element that drives the watch and the fusee was a cone shaped pulley that was used together with a barrel containing the mainspring.
The mainspring would rotate a barrel which had a length of catgut (later replaced by a chain) wound on it, with the other end coiled around the fusee. With the correct proportioning between the mainspring and the fusee an almost constant torque was maintained as the mainspring was unwound.
Nowadays the going-barrel has superseded the fusee.