A Rudimentary Treatise on Clocks, Watches, and Bells Informative Summary

Overview:

This 1903 edition of “A Rudimentary Treatise on Clocks, Watches, & Bells” by Edmund Beckett, Lord Grimthorpe, is a comprehensive guide to the principles of horology. The book, originally published in the mid-19th century, has undergone numerous revisions and expansions, reflecting the author’s extensive experience in designing and building clocks for public purposes, including the famous Westminster and St. Paul’s clocks.

The treatise begins with a detailed explanation of various time measurements, such as sidereal, solar, and mean time, and explores the history of timekeeping devices, including sun-dials, water clocks, and early weight-driven clocks. The author then delves into the mechanics of clocks, covering the essential elements of a clock train, different types of flywheels, pendulums, and escapements. Beckett provides a thorough exploration of pendulum theory, including the mathematics of isochronism and the influence of circular error, various methods for compensating pendulums for temperature variations, and the effects of air pressure on pendulum performance. The book also includes discussions on the construction and maintenance of striking clocks and turret clocks, as well as a detailed analysis of the best practices for bellmaking, hanging, and tuning.

Key Findings:

Pendulums: Beckett emphasizes the importance of a long and heavy pendulum for accuracy, noting that it is less affected by variations in force and air resistance. He also explores the circular error and its counteraction by pendulum springs, and the various methods for compensating pendulums for temperature changes, favoring zinc and steel over mercurial ones.
Escapements: The book highlights the advantages of the dead escapement over the recoil escapement, particularly in astronomical clocks. Beckett meticulously analyzes the theory of dead escapements, including the influence of friction and the role of the impulse angle, concluding that a short impulse angle is preferable.
Bells: Lord Grimthorpe provides a detailed analysis of bellmaking, covering historical aspects, the importance of the bell’s shape and composition, and best practices for casting, hanging, and tuning. He argues against the use of cast steel for bells and highlights the importance of proper bell towers and frames.

Learning:

Timekeeping Basics: The reader will gain a fundamental understanding of different time measures, including sidereal, solar, and mean time, and the reasons for their variations.
Pendulum Theory: The text provides a comprehensive explanation of pendulum theory, including the mathematics behind isochronism, the circular error, and the factors affecting pendulum performance. The reader will learn about various types of compensated pendulums and how to adjust their rate.
Escapement Mechanisms: The treatise delves into the workings of recoil and dead escapements, comparing their strengths and weaknesses. The reader will understand the principles of dead escapements, including the effects of friction, impulse angle, and arc length, and learn about the half-dead escapement.
Bellmaking and Hanging: Readers will gain insights into the history, construction, and tuning of bells, learning about the materials, shapes, and hanging techniques that produce the best sound quality.

Historical Context:

The text reflects the state of clockmaking and bellmaking in the early 20th century, highlighting the advancements made since the invention of the pendulum clock and the shift towards more accurate and reliable timekeeping devices. Beckett’s work provides a valuable historical record of the technological and scientific knowledge of the era, including the ongoing debate about the best methods for compensating pendulums for temperature and barometric pressure variations.

Facts:

Sidereal day: A sidereal day is one absolute rotation of the earth, or the time between two successive passages of the same star over any given meridian.
Equation of time: The difference between true and mean solar time for each day is called the Equation of time.
Mean time: Mean time is the average length of all the solar days in the year.
Solar day: A solar day is the interval between two successive transits of the middle of the sun over the meridian.
Fan fly: A fan fly regulates the velocity of a clock train by using vanes that are resisted by the air.
Conical pendulum: A conical pendulum is a pair of weighted arms attached to a revolving vertical axis by horizontal hinges, which regulate velocity more completely than a fly wheel.
Crown-wheel escapement: The earliest known escapement, used in clocks before the invention of pendulums, is the crown-wheel escapement.
Cycloidal theory: A body moving by gravity in a cycloid describes both large and small arcs in the same time.
Circular error: The excess of the time of vibration in a circular arc over that in the cycloidal one belonging to the same length of pendulum is called the circular error.
Center of oscillation: The center of oscillation of a pendulum is not a fixed point but a relative one, determined by the axis of suspension.
French metre: The French metre was intended to be the 40 millionth part of a meridian of the earth, but it is not a rational or useful measure.
Egyptian cubit: The Egyptian cubit, used in building the Pyramids, was probably 20 of their inches, being a little more than 20 of ours.
Dead escapement: The dead escapement was invented by Graham and provides a more accurate timekeeping mechanism than the recoil escapement.
Half-dead escapement: The half-dead escapement is a compromise between the recoil and dead escapements, offering a more stable rate in large clocks.
Loseby’s isochronal spring: A large circular loop of very thin steel wire designed to isochronize a pendulum in a dead escapement, but ultimately deemed unsuccessful.
Barometric error: The barometric error refers to the variation in a clock’s rate caused by changes in air pressure.
Zinc and steel pendulum: Zinc and steel pendulums provide an effective and cost-efficient method for compensating temperature changes.
Lead bobs: Lead bobs are preferred for large clocks due to their high specific gravity, making them less resisted by the air.
Cast iron jars: Cast iron jars are superior to glass for mercurial pendulums due to their durability, ease of construction, and ability to withstand heating to remove air bubbles.
Bell metal: The best bell metal is a combination of copper and tin, with the exact proportions varying slightly depending on the bell’s size and tone.
Great Paul: The Great Paul bell, housed in St. Paul’s Cathedral, is the largest bell in England.

Statistics:

Sidereal day: A sidereal day is 3m. 56s. shorter than a solar day.
Equinoctial year: The equinoctial year is 365 days, 5 hours, 48m. 49 12s.
Expansion of steel: A steel rod expands .0064 for 1000◦(F) of heat.
Expansion of zinc: Zinc expands .016 for 1000◦(F) of heat.
Expansion of lead: Lead expands .0165 for 1000◦(F) of heat.
Expansion of wood: White deal expands .0023 for 1000◦(F) of heat.
Specific gravity of mercury: A cubic inch of mercury weighs approximately half a pound.
Weight of Westminster pendulum: The Westminster pendulum weighs 700 lbs.
Weight of St. Peter’s pendulum: The pendulum at St. Peter’s Church in St. Albans weighs 9 cwt.
Weight of St. Nicolas’s pendulum: The pendulum at St. Nicolas’s Church in Bristol weighs 12 cwt.
Barometric error: A clock pendulum may gain nearly 13 sec. a day by being put into a vacuum.
Circular error: The circular error can neutralize the barometric error in a clock with an arc of 2◦ 45′.
Greenwich sidereal clock: The normal sidereal clock at Greenwich has a zinc pendulum and a barometric compensation system using a magnet.
Westminster clock: The Westminster clock only varies 1 sec. a week on average.

Terms:

Sidereal time: Time measured by the apparent motion of the stars.
Solar time: Time measured by the apparent motion of the sun.
Mean time: The average length of all the solar days in the year.
Equation of time: The difference between true and mean solar time.
Pendulum: A weight suspended so that it can swing freely under the influence of gravity.
Escapement: A mechanism in a clock that releases a tooth of the scapewheel at each vibration of the pendulum.
Recoil escapement: An escapement in which the scapewheel recoils slightly after releasing a tooth.
Dead escapement: An escapement in which the scapewheel stops momentarily after releasing a tooth.
Center of oscillation: The point in a pendulum that would oscillate in the same time as a simple pendulum of the same length.
Moment of inertia: A measure of a body’s resistance to rotational acceleration.

Examples:

Meridian dial: A simple meridian dial can be created by fixing a plate with a vertical slit facing south on a horizontal stone slab, marking the line of brightness at solar noon.
Dipleidoscope: The Dipleidoscope, invented by J.M. Bloxam, utilizes three small plates of glass to produce a single image of the sun at solar noon, acting as a meridian instrument.
Conical pendulum: The conical pendulum, used to turn reflectors in revolving lighthouses, involves weighted arms attached to a revolving vertical axis that fly farther out as they go.
Barker’s mill: The great equatorial telescope at Greenwich utilizes a Barker’s mill, a pair of revolving hollow arms, driven by water outflow, to power the clock.
Gridiron pendulum: Harrison’s gridiron pendulum, with its alternating brass and steel rods, compensates for temperature variations by keeping the bob at the same height.
Zinc and steel pendulum: The zinc and steel pendulum, which replaced the gridiron pendulum, uses a single zinc tube for compensation.
Mercurial pendulum: The mercurial pendulum, commonly used in astronomical clocks, uses a jar of mercury to counter the effects of temperature changes.
Compound bar compensation: This type of compensation, using a brass and iron bar brazed together, bends upwards with heat, adjusting the pendulum’s center of oscillation.
Westminster clock: The Westminster clock, designed by Lord Grimthorpe, utilizes a double-barrelled crab mechanism for its striking mechanism and a heavy pendulum that is fully compensated for temperature and barometric variations.

Conclusion:

“A Rudimentary Treatise on Clocks, Watches, & Bells” by Edmund Beckett, Lord Grimthorpe, provides a wealth of knowledge for anyone interested in the workings of timekeeping devices and bellmaking. It delves into the historical evolution of timekeeping, covering a range of devices from ancient clepsydras to modern weight-driven clocks. The treatise offers a detailed analysis of pendulum theory, covering the mechanics of vibration, the effects of circular error and barometric variations, and the different methods for compensating pendulums for temperature fluctuations. The book also presents a comprehensive guide to escapement mechanisms, particularly the dead escapement and its variations. Finally, Lord Grimthorpe’s treatise provides a valuable resource for understanding the principles and practice of bellmaking, including the importance of the bell’s shape, composition, and hanging techniques.

This 1903 edition reflects a period of significant technological advancements in horology, highlighting the pursuit of ever-greater accuracy and reliability in timekeeping devices. Beckett’s work remains a valuable resource for anyone seeking to understand the history, theory, and practice of clockmaking and bellmaking, offering a fascinating glimpse into the world of horology in the early 20th century.

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