Clock movement showing fusee

From Object Wiki

Clock movement showing fusee
Manufacturer	(unknown)
Production years	(unknown)
Production location	(unknown)

The fusee is a device for obtaining a constant driving torque from a spring as it uncoils, and has been widely employed in clocks, watches and chronometers.

In the early foliot clocks of the fourteenth and fifteenth centuries the rate of the clock depended largely upon the magnitude of the driving force. When the first spring-driven clocks were made, probably towards the end of the fifteenth century, it became essential to find some means of obtaining a constant driving torque from an uncoiling spring. There is some evidence for spring-driven clocks with a fusee as early as 1450, and the fusee mechanism is shown in sketches made by Leonardo da Vinci in 1490, but the earliest fusee clock which can be dated with certainty is one made by Jacob Zech in 1525.

[edit] How it works

It consists of a tapering drum with a spiral groove cut in it, and the pull of the mainspring is exerted through a cord or chain which is unwound from this groove on to the outside of the drum or ‘barrel’ containing the spring. When the spring is fully wound and exerting its greatest pull the cord is unwinding from the smaller end of the fusee, where it has only a small leverage, while when the spring is nearly run down the chain pulls at the wider end of the fusee, with a greater leverage. By suitably shaping the fusee the torque on its axis can be made quite uniform for all states of the spring.

[edit] Memories

Do you remember stories about clocks? Add your memories.

[edit] In the Science Museum's Records

Inv. No: 1883-74