Timing a mechanical pendulum clock
Timing the clock is all about the overall pendulum length and rarely has anything to do with the movement itself. Mechanical clock is easy to time providing you have the correct pendulum. When the pendulum is correct for that particular movement it will hang on the leader and keep approximate time. The fine timing can be done only with the pendulum adjustment located at the very bottom. At the bottom of the bob is some adjustment threads and a nut. To turn the nut one way raises the bob and the other lowers it. A shorter pendulum will make the clock run faster. A longer pendulum makes the clock run slower.
Fine timing the clock
If the clock is timing slow, raise the pendulum bob by turning the nut at the bottom of the bob. If the clock is fast, do the same but raise the clock's pendulum bob instead. One full turn is somewhere around 1-2 minutes a day faster or slower.
If there is no more adjustment
If the bob is all the way up and its still too slow or fast, you can shorten either the pendulum or the leader it hangs on to correct.
A lyre pendulum that does not keep time with the bob all the way adjusted will need its length altered. The overall length can be altered by the pendulum itself or the leader it hangs onto. The leader is about 5 to 7 inches long and engages with the crutch on back of the movement. The leader is the part that the pendulum top hooks on to. It is possible to shorten or lengthen the pendulum leader to put the clock in time range with some solder if needed. 1 3/4 inches is a good measurement to make one of these longer or shorter as needed, as this is the length of the threads at the bottom of the bob. So it will give you a full timing adjustment range all over again and you can go up or down as needed.
German pendulum length CM stamp
The pendulum length is considered overall and not just the pendulum. For example if the clock says 94cm on the back of it, this is the way the Germans measure there pendulum lengths from the top of the movement and all the way down. This will include the suspension spring way up top, the pendulum leader or guide you can call it, and also the pendulum from tip to tip all with a 4 1/2 inch bob diameter. Of course the larger the bob, the longer it will be beyond that 94cm measurement.
Used to keep time, now does not
If the clock kept time in the past but now does not, it means a worn gear. The escape wheel is worn and it is advancing more than one tooth at a time. The escape wheel alone would be hard to find, and hard to replace both. The entire movement would be disassembled to replace this worn escape wheel if there is another one found that will work. The cost of having this done would be the same price as a new movement. There is no such thing as having a repair on a clock movement being better than a new movement. The price would be about the same for a complete overhaul or a brand new one. First see if the clock movement is in production and available new. We do this by getting the numbers off of the back plate of the movement itself, right off of the brass. The email address is [email protected] and we will check availability and quote for the new one. If the movement is not in production anymore, then a repair is the only option.
Mechanical Pendulum Clock Timing Issues - Conclusion
Fine timing of the clock is easy as you can see. If the clock kept time in the past and now too fast, its time for a new movement and has nothing to do with the pendulum. A worn escape wheel is most likely the cause and a new unit would be less cost then a repair.