The rate of a clock is determined by two things – the length of the pendulum and the total gear ratio of the time train of the clock. The length of the pendulum determines its natural oscillation rate, and it requires a fairly significant force to overcome its natural rate, which makes them ideal for regulating clocks. The gear train determines how many ticks are required to move the clock hands a certain distance. While length of the pendulum and gear train are related, they are separate factors. The pendulum’s rate is determined by the laws of physics, while the gear train translates that into the human construct of the minute hand going around once per hour.
Knowing how to regulate your clock requires either empirical testing over a period of time – comparing your clock to an accurate time source and making corrections, or using a timing device, which requires knowing the target beat rate for the clock.
If you have access to the movement and a careful eye, you can count the teeth in the time train and calculate the correct beat rate for your clock. This page includes instructions and an online calculator if you wish to try this method.
The table below is a list of rates of some clocks expressed in beats per hour (BPH) and beats per minute (BPM). This is far from an exhaustive list as there are a large number of different BPH combinations used over the years. Others have published much longer listsof clock BPH rates.
It is theoretically possible to work the other direction – to start with the length of the pendulum and calculate the BPH rate it would need to swing at to keep time, however in practice this is difficult, as the critical dimension is from the top of the suspension spring to the center of mass of the pendulum. Measuring the center of mass of a pendulum is difficult as it depends on the type and design of the pendulum. For lyre pendulums, the center of mass is above the center of the bob. For stick pendulums, the center of mass is usually slightly below the center of mass.
This is a work in progress and the list will grow over time. Please Contact Us if you have any beat rates to add to the list.
Clock Beat Rates
|Clock Manufacturer||Clock Model||Beats Per Hour (BPH)||Beats Per Minute (BPM)||Tick Time (Seconds)|
|E Howard||No 70 Regulator||5084.7||84.745||0.708|
|Gilbert||No 20 Regulator||3600||60||1|
|Gilbert||No 8 Regulator||3600||60||1|
|Gilbert||No 16 Regulator||3600||60||1|
|Ithaca||No 2 Bank||4050||67.5||0.889|
|Killam & Co||Banjo||4704||78.4||0.765|
|Seth Thomas||No 2 Regulator||4800||80||0.75|
|Seth Thomas||No 1 Regulator||4800||80||0.75|
|Seth Thomas||Self-winding No 1||7200||120||0.5|
|Seth Thomas||Ships Clock||18000||300||0.2|
|Seth Thomas||Office Calendar No 6||8372||139.53||0.43|