Fusee (horology)

Fusee (horology)

Used in antique spring-powered mechanical watches and clocks, a fusee is a cone-shaped pulley with a helical groove around it, wound with a cord or chain which is attached to the mainspring barrel. Fusees were used from the 15th century to the early 20th century to improve timekeeping by equalizing the uneven pull of the mainspring as it ran down. G. Baillie stated of the fusee, "Perhaps no problem in mechanics has ever been solved so simply and so perfectly."