We commonly repair Synchronous Electric Clocks by various manufacturers. These use the frequency of the mains electricity supply to rotate the hands at the appropriate speed. They were manufactured for particular frequencies and so this was usualy mentioned on the clock somewhere as can be seen in the photo to the right. This particular clock would not work in the USA, where the frequency of the mains is 60Hz. You can also see this clock is self starting, which wasn’t the case with all synchronous movements; I’ll show a feature that allows this later.
The most common reason clocks stop is the build-up of dust and dirt, and old oil and grease becoming too thick for the wheels to easily turn. You can clearly see a large amount of dust near the contacts - this is where the protective case has to be open to allow the wires into the movement. You can also see the state of the bearing for the seconds wheel - it’s filthy and it’s no wonder this movement wouldn’t work. In general synchronous clocks are incredibly reliable and run for many years with no attention. This actually works to their detriment as it means they can have gone decades without care and often wear themselves out badly.
After disassembling the mechanism to thoroughly clean all parts and address wear and tear, they need to be correctly oiled and reassembled. Below is a video showing the self starting mechanism which ensures the hands more in the correct direction. Normally a synchronous movement requires manual intervention to start the movement in the correct direction, as the mains frequency motor will happily run clockwise or counter clockwise. You can see a wheel with three ‘teeth that interact with a paddle. This paddle allows the wheel to rotate freely in one direction only, so after running backwards for a moment , the clock is then forced to run the correct direction. Once running the movement is incredibly smooth, putting the ‘rolex sweep’ to shame!
After thorough testing the movement can be returned to the case for a final fully assembled test period. This particular clock is in a Bakelite case which has been hand polished with beeswax to bring back its original sheen.