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Finding a pendulum’s axis of rotation

Robert James Matthys

in Accurate Clock Pendulums

Published in print:
2004
Published Online:
January 2010
ISBN:
9780198529712
eISBN:
9780191712791
Item type:
chapter
Publisher:
Oxford University Press
DOI:
10.1093/acprof:oso/9780198529712.003.0004
Subject:
Physics, History of Physics

To determine a pendulum's axis of rotation, a small piece of paper is temporarily mounted on the front of the pendulum rod at the rod's top end, so that the paper extends up an inch or two past the ... More


Accurate Clock Pendulums

Robert J. Matthys

Published in print:
2004
Published Online:
January 2010
ISBN:
9780198529712
eISBN:
9780191712791
Item type:
book
Publisher:
Oxford University Press
DOI:
10.1093/acprof:oso/9780198529712.001.0001
Subject:
Physics, History of Physics

The Shortt clock, made in the 1920s, 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 ... More


James’ suspension spring equations

Robert James Matthys

in Accurate Clock Pendulums

Published in print:
2004
Published Online:
January 2010
ISBN:
9780198529712
eISBN:
9780191712791
Item type:
chapter
Publisher:
Oxford University Press
DOI:
10.1093/acprof:oso/9780198529712.003.0016
Subject:
Physics, History of Physics

In 1983, K. James published two useful but rather complicated equations whose purpose was to help design the suspension spring. The equations show the effect that different spring lengths, widths, ... More


Pendulum air movement: A failed experiment

Robert James Matthys

in Accurate Clock Pendulums

Published in print:
2004
Published Online:
January 2010
ISBN:
9780198529712
eISBN:
9780191712791
Item type:
chapter
Publisher:
Oxford University Press
DOI:
10.1093/acprof:oso/9780198529712.003.0028
Subject:
Physics, History of Physics

A previous experiment showed that the walls of a pendulum clock case can slow down the pendulum via air drag by about 1 second per day. The pendulum has a 2-second period. This chapter describes an ... More


An electronically driven pendulum

Robert James Matthys

in Accurate Clock Pendulums

Published in print:
2004
Published Online:
January 2010
ISBN:
9780198529712
eISBN:
9780191712791
Item type:
chapter
Publisher:
Oxford University Press
DOI:
10.1093/acprof:oso/9780198529712.003.0032
Subject:
Physics, History of Physics

An electromagnetically driven pendulum is more accurate than a mechanically (escapement) driven pendulum. This is because a pendulum is disturbed less by an electromagnetic drive pulse than by ... More


Better accuracy from simple pendulums

Robert James Matthys

in Accurate Clock Pendulums

Published in print:
2004
Published Online:
January 2010
ISBN:
9780198529712
eISBN:
9780191712791
Item type:
chapter
Publisher:
Oxford University Press
DOI:
10.1093/acprof:oso/9780198529712.003.0001
Subject:
Physics, History of Physics

This chapter deals with simple pendulums and with several things that can be done to improve their accuracy. Most of the items have only a minor effect on accuracy, but they add up. The pendulum ... More


Scaling the size of a pendulum

Robert James Matthys

in Accurate Clock Pendulums

Published in print:
2004
Published Online:
January 2010
ISBN:
9780198529712
eISBN:
9780191712791
Item type:
chapter
Publisher:
Oxford University Press
DOI:
10.1093/acprof:oso/9780198529712.003.0003
Subject:
Physics, History of Physics

Making a pendulum bigger or smaller involves more than just a linear scaling up or down of the pendulum's dimensions. If you want to make a larger or smaller pendulum than the one you have now, how ... More


Some practical properties of quartz

Robert James Matthys

in Accurate Clock Pendulums

Published in print:
2004
Published Online:
January 2010
ISBN:
9780198529712
eISBN:
9780191712791
Item type:
chapter
Publisher:
Oxford University Press
DOI:
10.1093/acprof:oso/9780198529712.003.0006
Subject:
Physics, History of Physics

The big attraction of quartz as a pendulum material is its good dimensional stability over time. Stability over time is the biggest and most needed characteristic in an accurate pendulum. In contrast ... More


Transient temperature effects in a pendulum

Robert James Matthys

in Accurate Clock Pendulums

Published in print:
2004
Published Online:
January 2010
ISBN:
9780198529712
eISBN:
9780191712791
Item type:
chapter
Publisher:
Oxford University Press
DOI:
10.1093/acprof:oso/9780198529712.003.0009
Subject:
Physics, History of Physics

This chapter describes some transient temperature measurements made on a pendulum with a quartz pendulum rod. Time offset error occurs because different parts of the pendulum change temperature at ... More


Bob shape

Robert James Matthys

in Accurate Clock Pendulums

Published in print:
2004
Published Online:
January 2010
ISBN:
9780198529712
eISBN:
9780191712791
Item type:
chapter
Publisher:
Oxford University Press
DOI:
10.1093/acprof:oso/9780198529712.003.0013
Subject:
Physics, History of Physics

The sphere and the vertically oriented cylinder are more repeatable and predictable bob shapes than the more efficient, lower-drag prolate spheroid and football shapes. As a bob shape, prolate ... More


Rate adjustment mechanisms

Robert James Matthys

in Accurate Clock Pendulums

Published in print:
2004
Published Online:
January 2010
ISBN:
9780198529712
eISBN:
9780191712791
Item type:
chapter
Publisher:
Oxford University Press
DOI:
10.1093/acprof:oso/9780198529712.003.0014
Subject:
Physics, History of Physics

The usual coarse adjustment for trimming a pendulum's clock rate is a threaded nut beneath the bob, which moves the whole bob up and down the pendulum rod. The surface of the thread is somewhat ... More


Barometric compensation with a crossed spring suspension?

Robert James Matthys

in Accurate Clock Pendulums

Published in print:
2004
Published Online:
January 2010
ISBN:
9780198529712
eISBN:
9780191712791
Item type:
chapter
Publisher:
Oxford University Press
DOI:
10.1093/acprof:oso/9780198529712.003.0017
Subject:
Physics, History of Physics

A crossed spring suspension provides an axis of rotation characterised by extremely low friction, something that a pendulum can use. The suspension typically consists of four flat strips of spring ... More


Stable connections to a pendulum’s suspension spring

Robert James Matthys

in Accurate Clock Pendulums

Published in print:
2004
Published Online:
January 2010
ISBN:
9780198529712
eISBN:
9780191712791
Item type:
chapter
Publisher:
Oxford University Press
DOI:
10.1093/acprof:oso/9780198529712.003.0019
Subject:
Physics, History of Physics

Chops, located on the ends of a pendulum's suspension spring, are designed to get a more solid grip on the spring. With a degree of helpfulness varying from outstanding to useless, chops give a ... More


Pendulum rod materials

Robert James Matthys

in Accurate Clock Pendulums

Published in print:
2004
Published Online:
January 2010
ISBN:
9780198529712
eISBN:
9780191712791
Item type:
chapter
Publisher:
Oxford University Press
DOI:
10.1093/acprof:oso/9780198529712.003.0021
Subject:
Physics, History of Physics

Over time, several different materials have been used for the pendulum rod such as steel, wood, and invar. The best material is quartz because of its proven stability and low thermal expansion. Steel ... More


The heat treatment of invar

Robert James Matthys

in Accurate Clock Pendulums

Published in print:
2004
Published Online:
January 2010
ISBN:
9780198529712
eISBN:
9780191712791
Item type:
chapter
Publisher:
Oxford University Press
DOI:
10.1093/acprof:oso/9780198529712.003.0022
Subject:
Physics, History of Physics

Even though invar is the most common material used for the pendulum rod in a good clock, it is still a poor material for the purpose because of its relatively poor dimensional stability over time ... More


The instability of invar

Robert James Matthys

in Accurate Clock Pendulums

Published in print:
2004
Published Online:
January 2010
ISBN:
9780198529712
eISBN:
9780191712791
Item type:
chapter
Publisher:
Oxford University Press
DOI:
10.1093/acprof:oso/9780198529712.003.0023
Subject:
Physics, History of Physics

Almost since its invention in 1896, invar has been known to be a dimensionally unstable pendulum rod material. A few articles have been published over the years, trying to address the dimensional ... More


Position sensitivity along the pendulum rod

Robert James Matthys

in Accurate Clock Pendulums

Published in print:
2004
Published Online:
January 2010
ISBN:
9780198529712
eISBN:
9780191712791
Item type:
chapter
Publisher:
Oxford University Press
DOI:
10.1093/acprof:oso/9780198529712.003.0024
Subject:
Physics, History of Physics

Every clock's pendulum needs a fine trim to adjust its rate to the desired value. This is frequently done by adding small weights to a weight pan, which is usually located about one-third of the way ... More


Effect of the pendulum rod on Q

Robert James Matthys

in Accurate Clock Pendulums

Published in print:
2004
Published Online:
January 2010
ISBN:
9780198529712
eISBN:
9780191712791
Item type:
chapter
Publisher:
Oxford University Press
DOI:
10.1093/acprof:oso/9780198529712.003.0026
Subject:
Physics, History of Physics

A pendulum rod's air drag has a significant effect on the pendulum's Q. Many years ago, an experiment was carried out to determine the effect of bob shape on a pendulum's Q. The results showed that a ... More


Correcting the pendulum’s air pressure error

Robert James Matthys

in Accurate Clock Pendulums

Published in print:
2004
Published Online:
January 2010
ISBN:
9780198529712
eISBN:
9780191712791
Item type:
chapter
Publisher:
Oxford University Press
DOI:
10.1093/acprof:oso/9780198529712.003.0027
Subject:
Physics, History of Physics

This chapter describes how to calculate and remove the air pressure error from a clock's time error versus time chart. Depending on geographic location and the density of the pendulum materials, air ... More


Time error due to air pressure variations

Robert James Matthys

in Accurate Clock Pendulums

Published in print:
2004
Published Online:
January 2010
ISBN:
9780198529712
eISBN:
9780191712791
Item type:
chapter
Publisher:
Oxford University Press
DOI:
10.1093/acprof:oso/9780198529712.003.0030
Subject:
Physics, History of Physics

The rate of a pendulum clock is affected by air pressure. As the air pressure increases, the clock slows down, and vice versa. The basic cause is that the pendulum floats in a sea of air, and when ... More


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