Accurate Clock Pendulums

Accurate Clock Pendulums

by Robert James Matthys
     
 

The Shortt clock, made in the 1920's is the most famous accurate clock pendulum ever known, having an accuracy of one second per year when kept at nearly constant temperature. Almost all of a pendulum clock's accuracy resides in its pendulum. If the pendulum is accurate, the clock will be accurate. In this book, the author describes many scientific aspects of

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Overview

The Shortt clock, made in the 1920's is the most famous accurate clock pendulum ever known, having an accuracy of one second per year when kept at nearly constant temperature. Almost all of a pendulum clock's accuracy resides in its pendulum. If the pendulum is accurate, the clock will be accurate. In this book, the author describes many scientific aspects of pendulum design and operation in simple terms with experimental data, and little mathematics. It has been written, looking at all the different parts and aspects of the pendulum in great detail, chapter by chapter, reflecting the degree of attention necessary for making a pendulum run accurately. The topics covered include the dimensional stability of different pendulum materials, good and poor suspension spring designs, the design of mechanical joints and clamps, effect of quartz on accuracy, temperature compensation, air drag of different bob shapes and making s sinusoidal electromagnetic drive. One whole chapter is devoted to simple ways of improving the accuracy of ordinary low-cost pendulum clocks, which have a different construction to the more expensive designs of substantially well-made ones. This book will prove invaluable to anyone who wants to know how to make a more accurate pendulum or pendulum clock.

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Product Details

ISBN-13:
9780198529712
Publisher:
Oxford University Press, USA
Publication date:
08/05/2004
Pages:
280
Product dimensions:
9.80(w) x 7.60(h) x 0.90(d)

Meet the Author

Robert J. Matthys was a Senior Research Engineer at Honeywell, Inc., from 1952 to 1987. He has spent thirty-seven years designing a wide variety of hardware and instrumentation in the fields of electronics, optics, acoustics, mechanics, and photography. In addition, he has spent nine years designing and testing pendulums of various kinds, along with their electronic drive systems and servos, both pulsed and continuous sine wave. He lives in Minneapolis, Minnesota.

Table of Contents

General
1. Better accuracy from simple pendulums
2. A short history of temperature compensation
3. Scaling the size of a pendulum
4. Finding a pendulum's axis of rotation
5. Does a pendulum's axis of rotation shift with amplitude?
6. Some practical properties of quartz
7. Putting Q in perspective
8. The Allan variance and the root mean square time error
9. Transient temperature effects in a pendulum
10. Transient response of a pendulum to temperature change
11. Dimensional stability of pendulum materials
12. Variations on a Riefler bob shape
13. Bob shape
14. Rate adjustment mechanisms
Suspension spring
15. Spring suspensions for accurate pendulums
16. James' suspension spring equations
17. Barometric compensation with a crossed spring suspension?
18. Solid one-piece suspension springs
19. Stable connections to a suspension spring
20. Stability of suspension spring materials
Pendulum rod
21. Pendulum rod materials
22. The heat treatment of invar
23. The instability of invar
24. Position sensitivity along the pendulum rod
25. Fasteners for quartz pendulum rods
26. Effect of the pendulum rod on Q
Air and clock case effects
27. Correcting the pendulum's air pressure error
28. Pendulum air movement: a failed experiment
29. Pendulum air movement: a second try
30. Time error due to air pressure variations
31. Effect of the clock case walls on a pendulum
Electronics
32. An electronically driven pendulum
33. Sinusoidal drive of a pendulum
34. Photoelectronics for pendulums
35. Check your clock against WWV
36. Electronic correction for air pressure variations

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