Foucault & clock (n° 25)

Foucault pendulum and clock built on the old chassis of my very first pendulum, No. 1. As a child had broken it at an exhibition in 2021, the question arose as to whether it should be repaired. In the end, it was much better to destroy it. Designed as it was at the time, it really was a miracle that it worked at all. “It’s the sum of the mistakes you’ve made that makes your pendulum tick” (Bob Holmström, 2004)

June 2024

The specifications, as well as the components, are subject to further refinement and are likely to change over the next few months as improvements are made. But it works, and does it very well.

Specifications:

Zero expansion Invar suspension wire.

The pendulum is a brass sphere filled with 2 kilos of molten lead.

The pendulum measures one metre, i.e. one oscillation per second, and drives the hands of the clock.

The top plate supports the thread guide, which adjusts the height and therefore the frequency.

The lower plate supports the Charron ring, adjustable in X/Y.

The two plates slide on the graduated rail and can be adjusted ‘hot’ without having to stop the pendulum.

The total amplitude is exactly 51 millimetres: it is regulated by an eddy current brake located under the pendulum (the large bronze cylinder). Precision tests will soon be carried out with this cylinder used as an eddy-current Charron ring, once the friction ring at the top has been eliminated.

Rotation measurements and temporal precision measurements are available here.