Introduction

Clock and watch escapments are the mechanical mechanisms which keep the pendulum or balance wheel moving. They are the most interesting part of these timekeepers. It is hard to understand how they work unless you see them in action. Fortunately, there are a number of Web pages featuring animations of escapments.

When a pendulum (or balance wheel) reaches a specific position in its cycle the escapement pushes it, giving it just enough energy to continue. Most mechanical escapements give one or two pushes during each cycle.

Some electrical escapements, such as the Synchronome escapement, give pushes once every thirty cycles. Another escapement, the Hipp toggle, gives a push, perhaps every ten minutes, when the swing has gotten too small.

The classic mathematical analysis of escapements and their errors was presented by English Astronomer Royal George Biddell Airy in 1826. The full article (which uses calculus) On the Disturbances of Pendulums and Balances, and on the Theory of Escapements. is on the Web. This topic is extended in Rawlings' book.

Some technical horological books on escapements available from horological book dealers:

Some Books on Escapements

• Watch Escapement - Fried, H. B. - 191 pp - 5 x 8
• Clock & Watch Escapements - Gazeley, W.J. - 294 pp - 5 1/2 x 8 3/4 - HB
• Clock and Watch Escapement Mechanics - Mark Headrick
• Practical Clock Escapements - Laurie, Penman - 248pp - 7 x 10 HB
• Science of Clocks & Watches, The, 3rd edition - Rawlings, A. L. - 393 pp - 6 x 9 - HB. Technical discussion of many escapements and their errors.

Horological Book Lists and Sources

Clock Explanations

• How Stuff Works: Pendulum Clocks
• How Stuff Works: Inside an Alarm Clock
• How Stuff Works: Digital Clock
• Introduction to escapement mechanics by Mark Headrick

Escapement Animations

• Mark Headrick's Escapements
• Robert Terwilliger's Watch Escapement

The NAWCC Clock and Watch Museum in Columbia, PA has an excellent collection of operating escapement models.