Sunday, 28 May 2017

Fusee Maintaining Power

One drawback of a Fusee is that power to the movement is lost whilst the watch is being wound, very often this was accepted on Verge Fusee watches but most Lever Fusee watches were equipped with "Maintaining Power" to overcome the problem.

The components fitted to the Fusee cone to provide "Maintaining Power"

To provide maintaining power the Fusee has some additional components, on the right of the picture above we see the underside of the Fusee cone which now does not have the teeth on its edge to engage with the centre wheel pinion.

Instead there are teeth to engage with the two sprung loaded paws on the piece shown in the centre which fits beneath it.

The teeth on the edge of this piece engage with a paw on the movement to prevent it turning the wrong way. The paw is shown in the picture to the right bottom centre, it is swung away from the Fusee in the picture as its spring would push it over without the top plate in position.

The piece on the left has the teeth to engage with the centre wheel and a flat circular spring running in this picture from 3 o'clock around to 12.

The top of the spring has freedom to move about 2 teeth along the rim of the disk, a stud just visible (click on the image for a larger view) engages with the small hole at 12 o'clock on the centre piece, it will be under tension and will provide power to the train during the brief period power comes off with each turn of the key.

The assembly is kept together with a collar pinned to the arbour as shown in the final picture. The slot near the top of the disk is the business end of the maintaining spring. The rivet to the left is securing the other end of the spring.

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