Simanaitis Says

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ON GRAVITY CLOCKS

THE TERM “gravity clock” suggests sci-fi. In fact, though, it can be quite the traditional opposite. I learned about gravity clocks through a friend gifting me with the RM /Sotheby’s auction catalog of the Milhous Collection.

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The Milhous auction, February 24 – 25, 2012, offered a marvelous array of everything from classic cars to slot machines. Lots 501 – 533 were devoted to clocks, several of which were of the gravity escapement variety.

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E. Howard gravity escapement tower clock, 60 x 71 x 39 inches. This and other images from the RM/Sotheby’s Milhous Collection auction catalog.  

Like many gravity clocks, this E. Howard example in the Milhous Collection began life in a tower, specifically of a Muncie, Indiana, high school. Similarly, the Elizabeth Tower of the British House of Parliament also houses a Denison double three-legged gravity escapement clock.

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The clock mechanism actuating the Big Ben bell will undergo shutdown and a £29 million refurbishment next year. Image by Aaron F. Ross (Dr-Yo).

Big Ben is the name of the clock’s bell, not the clock. Edmund Beckett Denison’s idea, perfected in the 1850s, is used in tower clocks around the world. What with Denison being elevated to Baron Grimthorpe in 1886, the mechanism is also known as a Grimthorpe Escapement.

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Video of a three-legged gravity escapement.

As its name suggests, a gravity clock needs no spring to propel its pendulum. A weight drives its six escapement legs in rotation. These in turn lift, lock and release arms, their extended portions propelling the pendulum solely through gravity. The pendulum’s purpose is to regulate the clock, not to drive it. Other pendulum lore resides at “Chaotic Pendulums.”

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Seth Thomas gravity escapement tower clock, 40 x 125 x 30 inches.

The Milhous Collection’s Seth Thomas gravity escapement clock originally resided in the Billings, Montana, court house. Temperature regulation for its pendulum is one of its features. According to the catalog, perhaps no more than 12 of its kind are known to exist around the world.

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E. Howard Model 0 clock, 21 x 60 x 38 inches.

An E. Howard Model 0 wasn’t originally intended for a tower; rather, it would reside in a wealthy residence. Relatively compact, the one in the Milhous Collection has Queen Anne style legs. Its hand crank is for “winding,” that is, periodically raising its weight.

To close on a modern note, the term “gravity clock” has also come to have an entertaining digital connotation.

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The Gravity Clock app by Joerg Piringer.

Extensive though it was, the Milhous Collection contained no iPhone apps. ds

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