Notes

Outline

Evolution of the Marine Chronometer The development of the Marine Chronometer from 1714 to 1942

Clocks in Navigation The Earth’s poles are stationary and this allows the North-South position to be determined by the apparent height of a known star above the horizon. The North Star, Polaris, provides the most accurate reading. The East-West position is more difficult and eluded navigators for centuries. Early navigators found a North-South position and then sailed East or West until they made landfall. They estimated their position by dead reckoning of their speed on the sea. The use of local time with a precision clock showing the time at a known location allowed precise East-West position calculation. The Earth rotates 360° in 24 hours Each hour time difference equals 15° in longitude

Act of Queen Anne

The International Competition The nation that could provide a commercial solution for the problem of the longitude would have a great advantage on the seas. The English had the Act of Queen Anne and the Longitude Board to spur interest. The French and Spanish governments offered similar prizes. Philip of Portugal had been a major influence in the earlier development of the use of the compass and North Star. The major competition in the 18th century was between the French and the English.

Harrison and the Act of Queen Anne John Harrison built the first successful Marine Chronometer, H1 in 1735, in response to the £20,000 prize offered under the November 12th, 1713 Act of Queen Anne. His final development, in H4, completed in 1759, was a very different mechanism but was the first true Marine Chronometer capable of supporting world wide navigation. We are indebted to the work of Rupert Gould for the restoration of these pieces and the the publication of his magnificent book Marine Chronometer in 1923 that spurred the revival of interest in the topic of early chronometers.

Working Model  of H1

Harrison’s H4 The Chronometer that won the Longitude Prize

The Chronometer Problem First, the machine must be insensitive to the amount of power available to drive the regulator. Second, the machine must be insensitive to the temperature. Third, the machine must operate reliably for long periods of time in harsh conditions.

Power and Isochronism Harrison’s first problem can be solved in two ways. The power from the driving force to the governor can be kept constant over time. Fuzees, detached escapements and remontoires were the main approaches to this problem. The elegant constant force escapements were the ultimate development of the remontoire concept. The governor can be insensitive to the power used to drive it. Isochronal hairsprings were the main expression of this solution to the problem

Temperature Harrison’s second problem was also approached from two directions. In a balance/spring oscillator the temperature problem is primarily due to changes in elasticity of the balance spring with temperature. The compensation curb is a device that changes the effective length of the hairspring as a function of temperature This is the method Harrison used and was the dominant method for the first 30 years of development The compensation balance is a device that changes the moment of inertia of the balance as a function of temperature. The first temperature compensating balance was developed by Leroy in 1765 and the first practical form was patented by Arnold in 1775 Both of these approaches were finally perfected with metallurgy in the early part of the 20th Century

Compensation

Durability The major foes of durability were oil deterioration, rust and metal fatigue over time. Harrison addressed the problem with the use of lignum vitae laminated parts, anti-friction rollers and the Grasshopper escapement. Later Arnold used gold hairsprings to avoid rust Continuous improvements in steel during the 19th Century produced better and better hairsprings and mainsprings The production of Palladium Hairsprings by Paillard solved both the rust and magnetism problem introduced when iron replaced wood in the ships The final problem solved was the deterioration of oil. It finally fell to “A prize for whoever knows this” in the early 20th Century

Working Model  of H1

Harrison’s H4 The Chronometer that won the Longitude Prize

Larcum Kendall Harrison had a difficult time convincing the Board of Longitude to pay his prize money. (Eventually the King ordered parliament to pay him.) The board insisted in knowing all the secrets of how to make the machines before they would award the prize. They also believed the chronometer was too expensive. Harrison was reluctant to part with what he had learned and developed. He agreed to train another chronometer maker, Larcum Kendall, to try to convince the Board that “one skilled in the art” could make the chronometers. Kendall produced 3 chronometers roughly to Harrison’s design that had performance equal to that of H4. One of these chronometers was in use by Capt. Bligh on the Bounty at the time of the mutiny and it remained on Pitcairn Island for the next 50 years.

Pierre LeRoy and the French School Pierre LeRoy invented the detent escapement in 1765. LeRoy’s thermometric balance solved the temperature compensation problem 100 years before Loseby invented the same solution. Berthoud introduced gimbals to stabilize the motion of the chronometer. The works of Berthoud, Breguet and Motel continued a tradition of highly artistic but impractically expensive chronometers.

Pierre Le Roy’s Marine Chronometer

Ferdinand Berthoud’s Montre Marine

Pocket Chronometer by Louis Berthoud

Three Chronometers by Breguet from Antiquorum “Art of Breguet”

Mudge’s Remontoire Thomas Mudge invented the lever escapement mechanism that was the dominant timekeeping mechanism in watches until the introduction of quartz electric watches. Mudge interrupted his career as a major maker of watches to pursue the prize for further improvements in Marine Chronometers. His “Green” and “Blue” represent the ultimate development of the remontoire concept. Mudge’s son commissioned several additional chronometers on his father’s design.

Mudge’s Green

Arnold and Earnshaw Arnold invented a practical pivoted detent chronometer several years after Leroy. Arnold invented the bi-metallic temperature compensation balance. Arnold invented the helical hairspring and terminal coils. Earnshaw conceived of using a flat spring in place of the pivot on the Arnold detent. Earnshaw conceived of laminating the brass and steel components of the bi-metallic balance. Arnold invented a less practical form of spring detent escapement. There was considerable controversy over who had precedence

Arnold Marine Chronometer

Large Arnold Pocket Chronometer

Arnold & Son Chronometer 1789

Earnshaw Pocket Chronometer  “In the Grey”

Chronometer Escapement

Brockbanks Peto Cross Detent ca 1800

Practical Chronometers Dozens of English makers entered the competition in the early 19th Century for the annual prize chronometer to furnish to the Admiralty. The Kew trails spurred an intense competition that soon solved essentially all the problems of adjusting for isochronism and temperature. The remaining problem that plagued makers in the middle of the 19th Century was the error in the middle temperature region.

Wm. Bond & Son Survey Chronometer

John Roger Arnold Chronometer w/ Prest’s Keyless Works

Kelvin & White 8 Day

The Middle Temperature Problem The hairspring loses elasticity as the temperature rises (it also elongates slightly) This causes the oscillation of the balance to slow down. A plain balance expands as the temperature rises which also causes the oscillation of the balance to slow down. A bi-metallic balance decreases its radius as the temperature rises This causes the oscillation of the balance to speed up. Unfortunately, these two phenomena do not have the same shape as a function of temperature Therefore the period as a function of temperature will only be correct at two temperatures

Middle Temperature Solutions Discontinuous Compensation A mechanical stop inhibits the movement of the balance either in heat or cold Non-linear Compensation A secondary bi-metallic system partially corrects the bi-metal function of the balance Thermometric Compensation Glass thermometers either replace or supplement the the bi-metal function of the balance Inherent Material Compensation (Metallurgy) The hairspring material is insensitive to temperature (Elinvar) The balance material has an expansion curve that matches the hairspring (Guillaume)

Middle Temperature Balances

Kelvin & White w/ Poole’s Auxiliary

Dent Staple Balance

The Golden Age 1880 to 1910 Springers and Adjusters became the stars of the industry by the 1880s Kullberg, Johannsen, Walsh, and the Frodsham family took leadership of the British chronometer industry.  Ditisheim, Paillard, and Nardin led the development of the Swiss chronometer industry. Lange began the development of a German chronometer industry in Glasshutte.

Fletcher Marine Chronometer w/ Airy’s Bar

Johannsen Marine Chronometer

Johannsen Deck Watch

The Decline of the Chronometer Industry

Jurgensen Conversion to Deck Watch

Hamilton WW I Deck Watch

WW II Revival The US Navy issued a request for mass produced Marine Chronometers at the beginning of WW II. Hamilton developed a new design loosely based on the Swiss Nardin ebauche using a newly designed balance, hairspring and detent. Elgin developed a new design with special features for maintainability using the proven Guillaume Balance The Elgin entry failed the purchase trials and was not used by the Navy. It was sold in small numbers for civilian use after the war. Large numbers of lever pocket watches were finished and adjusted for navigation use

Hamilton Marine Chronometer M21

Elgin Marine Chronometer Grade 600

Satellites and the Final Solution to the Longitude Problem Global Positioning Satellite System is the ultimate solution to the navigation problem. The satellites allow the position of an observer to be determined by “triangulation” from a set of known objects in the sky. GPSS is oddly similar to one of the “insane proposals” brought to the Longitude Commission in the early 18th Century. The idea was to station ships across the ocean that would place flares in the sky for ships to observe and determine their position.