timberland sweater History of Famous British Engineers
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England is one of the oldest European countries ( over 1000 years old ) and London itself was founded by the Romans in 43 AD. As I have many generations going back to the 7th. century England I thought it would be of interest to write about England’s famous people and events.
As I am a direct descendent of Sir Christopher Wren and I have a keen interest in English and British history especially English hero’s like John Harrison I thought I would write this article.
John Harrison (24 March 1693 24 March 1776) was a self educated English Clockmaker and Yorkshire Carpenter who invented the marine chronometer, a long sought device in solving the problem of establishing the East West position or Longitude of a ship at sea, thus revolutionising and extending the possibility of safe long distance sea travel in the Age of Sail. The problem was considered so intractable that the British Parliament offered a prize of 20,000 (comparable to 2.87million / 3.65million / $4.72million in modern currency) for the solution.
John Harrison was born in Foulby near Wakefield in West Yorkshire the first of five children in his family. His father worked as a carpenter at the nearby Nostell Priory estate. The house where he was born bears a blue plaque.
Around 1700, the family moved to the North Lincolnshire village of Barrow upon humber. Following his father’s trade as a carpenter, Harrison built and repaired clocks in his spare time. Legend has it that at the age of six while in bed with smallpox he was given a watch to amuse himself, spending hours listening to it and studying its moving parts.
In 1730 Harrison created a description and drawings for a proposed marine clock to compete for the
Longitude Prize and went to London seeking financial assistance. He presented his ideas to Edmond Halley, the Astronomer Royal. Halley referred him to George Graham the country’s foremost clockmaker. He must have been impressed by Harrison, for Graham personally loaned Harrison money to build a model of his marine clock.
It took Harrison five years to build Harrison Number One or H1. He demonstrated it to members of the Royal Society who spoke on his behalf to the Board of Longitude. The clock was the first proposal that the Board considered to be worthy of a sea trial. In 1736, Harrison sailed to Lisbon on HMS Centurion and returned on HMS Oxford. On their return, both the captain and the sailing master of the Orford praised the design. The master noted that his own calculations had placed the ship sixty miles east of its true landfall which had been correctly predicted by Harrison using H1.
This was not the transatlantic voyage demanded by the Board of Longitude, but the Board was impressed enough to grant Harrison 500 for further development. Harrison moved on to develop H2, a more compact and rugged version. In 1741, after three years of building and two of on land testing, H2 was ready, but by then Britain was at war with Spain in the War of Austrian succession and the mechanism was deemed too important to risk falling into Spanish hands. In any event, Harrison suddenly abandoned all work on this second machine when he discovered a serious design flaw in the concept of the bar balances. He was granted another 500 by the Board while waiting for the war to end, which he used to work on H3. Harrison spent seventeen years working on this third ‘sea clock’ but despite every effort it seems not to have performed exactly as he would have wished. Despite this, it had proved a very valuable experiment. Certainly in this machine Harrison left the world two enduring legacies the bimetallic strip and the caged roller bearing.
After steadfastly pursuing various methods during thirty years of experimentation, Harrison moved to London in the late 1750’s where to his surprise he found that some of the watches made by Graham’s successor Thomas Mudge kept time just as accurately as his huge sea clocks. Harrison then realized that a mere watch after all could be made accurate enough for the task and was a far more practical proposition for use as a marine timekeeper. He proceeded to redesign the concept of the watch as a timekeeping device, basing his design on sound scientific principles.
He had already in the early 1750’s designed a precision watch for his own personal use, which was made for him by the watchmaker John Jefferys C. 1752 53. This watch incorporated a novel frictional rest escapement and was also probably the first to have both temperature compensation and a going fusee, enabling the watch to continue running whilst being wound. These features led to the very successful performance of this “Jefferys” watch and therefore Harrison incorporated them into the design of two new timekeepers which he proposed to build. These were in the form of a large watch and another of a smaller size but of similar pattern. However only the larger No. 1 (or “H4” as it sometimes called) watch appears ever to have been finished. (See the reference to “H6” below) Aided by some of London’s finest workmen, he proceeded to design and make the world’s first successful marine timekeeper that for the first time, allowed a navigator to accurately assess his ship’s position in Longitude. Importantly, Harrison showed everyone that it could be done. This was to be Harrison’s masterpiece an instrument of beauty, resembling an oversized pocket watch from the period. It is engraved with Harrison’s signature, marked Number 1 and dated 1759.
This first marine watch (or “Sea watch” as Harrison called it) is a 5.2″ diameter watch in silver pair cases. The movement has a novel type of escapement which can be classed as a frictional rest type, and superficially resembles the verge escapement with which it is often incorrectly associated. The pallets of this escapement are both made of diamond, a considerable feat of manufacture at the time. The balance spring is a flat spiral but for technical reasons the balance itself was made much larger than in a conventional watch of the period. The movement also has centre seconds motion with a sweep seconds hand. The Third Wheel is equipped with internal teeth and has an elaborate bridge similar to the balance cocks of the period. It runs at 5 beats (ticks) per second, and is equipped with a tiny remontoire. A balance brake stops the watch half an hour before it is completely run down, in order that the remontoire does not run down also. Temperature compensation is in the form of a ‘compensation curb’ (or ‘Thermometer Kirb’ as Harrison put it). This takes the form of a bimetallic strip mounted on the regulator sector rack, and carrying the curb pins at the free end. During development of No.1, Harrison abandoned the regulator, but left the regulator disc in place for sthetic reasons, and the compensation.
H4 took six years to construct and Harrison, by then 68 years old, sent it on its transatlantic trial in the care of his son, William, in 1761. When HMS Deptford reached Jamaica the watch was 5 seconds slow, corresponding to an error in longitude of 1.25 minutes, or approximately one nautical mile. When the ship returned, Harrison waited for the 20,000 prize but the Board believed the accuracy was just luck and demanded another trial. The Harrisons were outraged and demanded their prize, a matter that eventually worked its way to Parliament, which offered 5,000 for the design. The Harrisons refused but were eventually obliged to make another trip to the Caribbean city of Bridgetown on the island of Barbados to settle the matter.
At the time of the trial, another method for measuring longitude was ready for testing: the Method of Lunar Distances. The moon moves fast enough, some twelve degrees a day, to easily measure the movement from day to day. By comparing the angle between the moon and the sun for the day one left for Britain, the “proper position” (how it would appear in Greenwich, England at that specific time) of the moon could be calculated. By comparing this with the angle of the moon over the horizon, the longitude could be calculated.