Féry’s electrically driven pendulum

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Féry’s electrically driven pendulum
Manufacturer	Professor Charles Féry
Production years	20th century
Production location	France

In this device, invented and patented by Professor Charles Féry of Paris in 1907, a pendulum receives impulses form an electro-magnet every swing, but the contact-making is done by a subsidiary pendulum driven from the main pendulum by electro-magnetic attraction. The main pendulum is thus free in so far as it makes no material contacts, but the interference with its motion due to contact-making, though indirect, is still very considerable.

[edit] How it works

The bob on the main pendulum consists of a horseshoe magnet, one pole of which threads a fixed coil, while the other passes through a copper ring carried on the subsidiary pendulum. Eddy currents are set up in the copper ring, and the forces between these and the magnet of the main pendulum tend to reduce relative motion, so that the subsidiary pendulum is kept swinging. The left-hand contact makes the circuit through the fixed coil which gives the impulse to the main pendulum, while the right-hand contact can by used to drive or control a subsidiary clock or system of dials. The coil is made of high resistance in order to reduce the relative importance of variations of contact resistance.

[edit] Memories

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[edit] In the Science Museum's Records

Inv. No: 1913-568