Conical pendulum clock
Instead of swinging to and fro, its pendulum sweeps a steady circle, so the clock runs almost silently and its hands glide rather than tick.
What is a conical pendulum clock?
A conical pendulum clock is regulated by a pendulum that moves in a circle rather than back and forth. The bob travels around a horizontal loop while the rod sweeps out the shape of a cone, which gives the clock its name.
Most were made as novelties for the home in the second half of the 19th century. Royal Museums Greenwich notes that they were never good timekeepers but were prized for being pleasant to watch and running virtually without noise.
How it works
An ordinary pendulum clock, the kind Christiaan Huygens invented in 1656, relies on an escapement. Each time the pendulum swings, it releases the gear train by one small step, which is what makes the tick and the jerky movement of the seconds hand.
A conical pendulum needs no escapement of that kind. As the Linda Hall Library explains, because the pendulum circles steadily instead of swinging to and fro, the clock can do without an escapement, so the seconds hand moves smoothly rather than in small jerks. With no stop-start action in the train, the movement also makes almost no noise, which the Halim Time and Glass Museum calls the type's main advantage.
There are practical costs. The circling pendulum needs open space around it, which shapes the whole design: on the big Farcot clocks the dial ended up low beneath the pendulum. And however smooth the motion looks, Royal Museums Greenwich sums up the type as never good timekeepers.
See also: where the escapement sits in an ordinary movement on OnlineClock.app.
A brief history
The idea is nearly as old as the pendulum clock itself. The Linda Hall Library dates Christiaan Huygens's invention of the ordinary pendulum clock to 1656, and the Halim Time and Glass Museum says the first conical pendulum followed shortly after, around 1659, though it does not name an inventor. Besides novelty clocks, the museum notes, conical pendulums were used by astronomers to drive equatorial telescopes, where smooth, continuous motion mattered more than a crisp tick.
The domestic version had its moment in the later 1800s. It was an experimental branch of clockmaking, the Halim museum says, and relatively few were produced.
Their stage was the world's fair. International exhibitions became fashionable in Britain and France after the Great Exhibition at the Crystal Palace in London in 1851, and a clock whose pendulum circled in a statue's hand was ideal for crowds. The Linda Hall Library notes the drawbacks: the big Farcot clocks were very expensive, perhaps because each came with a full-size sculpture, and their dials sat so low beneath the pendulum that they were hard to read unless raised on a plinth.
Famous makers and examples
The name most associated with the type is Henri-Eugène-Adrien Farcot, a Paris clockmaker born in 1830 who began making conical pendulum clocks in 1855. He was also a balloonist: during the siege of Paris in 1870-71 he flew the mail balloon Louis Blanc out of the city to Belgium, and later published an account of the flight. Farcot's showpieces held the pendulum in the hand of a life-size statue of Urania, the muse of astronomy, usually sculpted by Albert-Ernest Carrier-Belleuse.
Farcot exhibited these clocks at world's fairs, including London in 1862 and Paris in 1867. A Farcot clock now at Drexel University in Philadelphia was shown at the 1867 Paris exposition, according to the Linda Hall Library. Royal Museums Greenwich adds that at the Paris Exhibition of 1878 he showed a longcase clock with a 25-meter conical pendulum hung from the ceiling.
In the United States, the Halim museum names E. N. Welch and Florenz Kroeber (1840-1911) of New York as the main makers, with Kroeber the more successful. Its Kroeber clock of about 1878, labeled Eight Day Noiseless Rotary No. 1, gives a Cortland Street address and cites a patent of June 18, 1878. The Seiko Museum in Tokyo holds a French clock of about 1865 in which a doll holds the pendulum, kept turning at a steady speed by the spring-driven movement.
How to recognize one
The giveaway is motion: watch the pendulum, and if it travels around in a circle instead of side to side, you have a conical pendulum clock. Many hang the pendulum from a figure's hand or from an open support above the dial, and the clock runs without a tick.
On smaller examples the dial may sit below the pendulum. Royal Museums Greenwich holds one shaped like a domed colonnade of five brass columns, with the pendulum circling inside and the hours shown on a ring in the base.
Smaller clocks often use a conventional train below the pendulum. The Kroeber example at the Halim museum, for instance, has a strip-frame movement that strikes on a gong using a countwheel, with the circling pendulum hung from a pierced, ebonized wooden support. On the Greenwich example, a pointer on the pendulum's crutch moves over a rough scale of seconds.
See also: time one full circuit of a pendulum yourself on OnlineClock.app.
Questions people ask
Why doesn't a conical pendulum clock tick?
Its pendulum moves in a continuous circle rather than stopping and reversing, so the clock does not need a stepping escapement to release the gears. Without that stop-start action there is no tick.
Are conical pendulum clocks accurate?
Not especially. Royal Museums Greenwich describes them as never good timekeepers. They were valued for their quiet running and the spectacle of the circling bob.
Who invented the conical pendulum?
No single inventor is named in the museum sources used here. The Halim Time and Glass Museum dates the first conical pendulum to around 1659, shortly after Huygens's pendulum clock of 1656. In the 19th century Eugène Farcot in France and Florenz Kroeber in the United States made the best-known domestic versions.