Torsion clock

These clocks are very fiddly to repair.  Most repairers won't touch them but I quite enjoy working on them even if they can be time wasters.  They are usually called Anniversary clocks or 400 day clocks.  This was a marketing term so they could be bought to remember a special event and would only need winding on the anniversary of that event.  They do go for a long time but often don't make the anniversary!  This clock keeps time with a mechanism called a torsion pendulum. This is a weighted disk or wheel, often decorative with 3 or 4 chrome balls on ornate spokes, suspended by a thin wire or called a torsion spring (also known as a suspension spring). The torsion pendulum rotates about the vertical axis of the wire, twisting it, instead of swinging like an ordinary pendulum. The force of the twisting torsion spring reverses the direction of rotation, so the torsion pendulum oscillates slowly, clockwise and counterclockwise. The clock's gears apply a pulse of torque to the top of the torsion spring with each rotation to keep the balls going.
The thickness of the wire is critical.  I have fitted one that is 0.058mm.  If I fitted one that was 0.061mm it would make a lot of difference to the timekeeping.  The timekeeping can be adjusted by narrowing or widening the rotating circumference of the balls using the knurled wheel (think of ice skaters who spin faster when they have their hands by their sides.)