L’Ultime (n°27)
Version 1: October 2024
Foucault pendulum / compass mounted on a cardan shaft and without a Charron friction ring, but with a Foucault brake ring underneath. A Charron ring was installed beforehand, but it can be rendered inoperative simply by moving it high enough.

Its suspension is different from all the others I’ve made so far: a steel point resting on a concave bed, also made of steel.

Another specification: the pendulum itself is an authentic compass! The arrow comes from a child’s compass, glued to the top of the pendulum. It permanently keeps the pendulum in the direction given by the Earth’s magnetism. Without it, the suspension would rotate on itself and inevitably hit the stop. The red part points south and the white part north.

This prototype worked first time without any adjustments. However, the suspension is not as reliable as a wire. So I decided to modify it and add the Charron ring. Here’s the final version:
Version 2: November 2024



Specifications:
Pendulum length: adjustable between 1.10 and 1.40 metres.
Weight of the balance: 2.1 kilos (stainless steel sphere filled with molten lead and polished)
Oscillation maintained by a repulsive electromagnetic impulse each time the pendulum passes.
8 mm bronze Charron ring, adjustable in X/Y/Z direction
Electromagnet with adjustable position in X/Y
Power supply: 1.5-volt battery, to be replaced every 3 years. The revolution of the pendulum is also indicated by a laser beam located under the pendulum. The beam is reflected very far away by the sphere, so that its movement can be observed as if it were a pendulum with an oscillation length of 10 metres.
Six verniers showing the rotation of the wire, the Charron ring, the pendulum, the Charron ring support, the revolution of the pendulum in degrees and the revolution of the pendulum graduated in half-hours.