In the early 1400s came the invention of the coiled spring or fusee which maintained constant force to the gear wheels of the timekeeper despite the changing tension of its mainspring.

Constant force spring hanger is a device which puts invariable tension on the thing it hangs in limited displacement.

Check the wear of the electric brush and see whether the constant force spring has distorted or not. Over-worn electric brush and distorted force spring should be replaced.