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Submitted by: Geoff Howard
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The fusee was invented around 1450 and was developed to even out the turning force, or torque, of a clock spring as it wound down. This was needed to improve the accuracy of clocks by maintaining a more constant speed for the gears. The fusee is a conical shaped drum with a groove shaped around it. When the spring is fully wound and at maximum torque, the fusee causes the force to be exerted at the small end of the drum and move up to the more easily turned large diameter of the drum as the spring unwinds.