MARCEL BETRISEY CREATIONS  Sion Switzerland Phone: ++41 273238808 Mobile ++41 793801679 Email: see "Contact"

PYRAMID (Foucault pendulum)

Small  (less than 1 meter) Foucault pendulum, showing the Earth's rotation hour after hour. It is activated by an electro-magnet
at the bottom of the device. Power is supplied by a 1.5 volt battery that needs to be replaced every year. The pendulum
rotation can be observed on the hour-graduated circle at the bottom. This is a very suitable piece for a school or university

This is not a clock as there is no fixed time reference or temperature compensation. The elliptical distortion is cancelled through
a Charron ring, as for Leon. No specific care is required to launch the pendulum: just swing it once, that's all. It will stabilise
after 1 or 2 hours. The Foucault effect is already visible after half an hour. (On this picture the dial is graduated for the North
pole latitude).

"It's the very accumulation of the errors you've made that make this pendulum work". (Bob Holström)
It's not too difficult to design a long pendulum. If you have a good suspension with a balanced propulsion system just launch
your pendulum and you're OK.
On the contrary a short Foucault pendulum that operates correctly is just miraculous. Even if designed to perfection it will
never work at the first attempt but will always need subtle adjustments that will take time to pinpoint.
The pendulum installation must be done once and for all. It will not be possible to move it around and have it operate in
different places because the adjustments and levelling are very critical and must not be tampered with once the pendulum is
operating correctly. When everything goes well the adjustments can take up to 2 weeks at installation time.

Please email or call me if you want to order. The minimum manufacturing delay is three months. Please specify the
latitude at which the pendulum is to be used, to allow customisation of the hour ring. A full custom design based on
your own specifications is also possible (glass protection, special base or accessories, different design, different

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English translation by Jean-Marc Julia