Various Foucault clocks…

The TF1 pendulum (April 2010)

Built for a TV report. It has two new specifications compared to the others previously built: the suspension head is placed on two computer hard disks, which allows to centre it, and the Charron ring is also made of two hard disks.

Otherwise, all the components are classical: suspension wire made with a quitare string, centering ruby and electromagnetic propulsion.

This is the only pendulum that I thought would work the first time. It did. Two other pendulums built earlier did start like this, but it was more a matter of luck than anything else. Not this one: it’s the sum of the experience of the other 18. Proof that you have to stop making them and move on.

PYRAMID (Foucault pendulum)

A small Foucault pendulum, less than 1 metre long, which shows the rotation of the earth hour by hour. It is propelled by an electromagnet located at the bottom of the pendulum. It is driven by a 1.5 volt battery that must be changed every year. The reading of the progress of the pendulum is done on the graduated disc at the bottom. The graduations are divided into hours

It is not a clock as there is no fixed time base and no temperature compensation. The correction of the advance of the ellipse is done by a Charron ring, as for Léon. No special precautions are required when the pendulum is first thrown: just push it and that’s all. It stabilizes itself after 1 or 2 hours. The Foucault effect can already be seen after waiting half an hour.

POINTEAU

(Foucault clock indicating the time on the floor)

This ultra-strong steel cone is a hydroelectric power station needle. When it was in use, it regulated the flow of water that drove the turbine. The grooves were caused by the flow of water. This piece of steel weighing about 40 kilos is the centrepiece of the pendulum. A laser beam passes through it and is aimed at the pendulum, a polished stainless steel sphere. The reflected beam illuminates a dial at the base of the cone. The earth rotates. The plane of the balance wheel remains fixed in relation to the universe, but we can see that the laser beam is moving forward in a clockwise direction. We can thus read the time on the ground by following the course of the reflected beam.

There is no need for a frame for this pendulum. The suspension is fixed directly to the ceiling. The length of the wire can go from 1 meter to 4 meters. This pendulum is made to be displayed in the middle of a hall so that people can see it from all sides.

Right: Léon, Moréno, Conti. Left: L’Anachrone, Aprilia and Cyclostyle

THE TUBE Foucault’s pendulum

Short Foucault pendulum whose damping of the ellipse effect is caused by another of Léon Foucault’s discoveries, the magnetic brake. A moving magnet on a non-magnetic conducting metal will be braked and induce an electric current. On this pendulum, this brake is the brass ring that can be seen under the balance wheel. This ring also regulates the amplitude of the pendulum and prevents it from hitting the glass tube.

Mini Foucault

This short (12 cm) Foucault pendulum was not designed to enter the Guinness Book, but it probably belongs there. I originally made it as a test rig to test the strength of different suspension materials. As the pendulum swings much faster than the others (more than 171 swings per minute instead of 60) and its amplitude is much greater (20°), the materials wear and fatigue much faster. The lessons learned are used to improve the other clocks.

(The bottle only serves as a scale)

The construction of this pendulum was, because of its length, much more difficult than that of all the others. The suspension wire is guided by ceramics. I had to put two successive Charron rings of different diameters to avoid parasite vibrations in the pendulum’s course. The upper Charron ring is a ruby, and the second is made of brass. The use of two rings also reduces the angle given to the wire by the amplitude of the pendulum, thus prolonging the longevity of the suspension.

The frame is made of cast aluminium and comes from a Berkel scale. It was cast in one piece. It may look like it is oversized, but it should be noted that the slightest torsion influences the pendulum and cancels the force that makes it turn. And this force is extremely reduced here because of the small amplitude and the reduced weight of the pendulum.