Grandfather Clock Pendulum and Weights - How to Choose a Grandfather Clock

An important thing to keep in mind when choosing a grandfather clock is the pendulum and weights. Find our full selection of grandfather clocks here.

Grandfather Clock Pendulum

A grandfather clock pendulum played a significant role in shaping the design and style of a grandfather clock. Christian Huygens came up with a new method to create a pendulum to help clockmakers. His idea was to step aside from powering clocks by springs and weights to a new way where a pendulum would swing every second with the anchor escapement system. The new formula required a longer pendulum.

The advantage of the longer pendulum and shallower swing is that less power, in the form of weights driving the clock, was needed, as well as slower beats and less wear on the moving parts. All this makes for better long term accuracy of the clock. Creating a clock with a new mechanism required a long pendulum that had to be put in a long case.

Grandfather clock pendulums are made of Invar due to its near zero coefficient linear thermal expansion enabling accurate timekeeping. When the clock pendulum was first invented, accuracy was compromised due to the varying temperatures throughout the seasons. However, by using Invar, the length of the pendulum didn’t change and therefore the time was always correct.

The pendulum in most grandfather clocks has a metal rod with a metal weight that is often called the bob and is located on the end.

Howard Miller Grandfather Clock Pendulum and Weights - How to Choose a Grandfather Clock

Grandfather Clock Weights

Grandfather clocks classically were made with one weight or two weights, and later on, a third weight was added. Each weight is responsible for a different task. The weights are usually pretty heavy because they are made with cast iron in a brass casing.

Grandfather clocks with one weight have a strike only on an hour which indicates that this is a 30-hour clock. It needs winding everyday and has only one winding hole because it uses the same weight for timekeeping and for the strike. Due to this, these grandfather clocks are less expensive. Interesting fact is that manufacturers started producing 30-hour grandfather clocks with two winding holes to give it a more expensive look: one was an actual winding hole and the other one was a dummy.

Grandfather clocks with two weights are often called an 8-day clock. This kind of grandfather clock has a separate weight: one to power the clock, and one to drive the striking mechanism of the chimes. Eight day grandfather clocks require two winding holes to wind the weights to their initial position with the help of a winding ‘key’.

Grandfather clocks with three weights appeared at the beginning of the 20th century and means that there is an additional 1/4-hour strike. Similar to the two weight clocks, it should be wound back every week. Nowadays, most grandfather clocks have three weights with separate purposes. One weight on the right powers the chime melody, one weight in the middle drives the pendulum, and one weight on the left controls the striking mechanism.