Thomas Mudge and His Detached Lever Escapement

There’s no doubt that Thomas Mudge’s detached lever escapement ranks as one of the most bright and meaningful inventions in the whole field of horology. For well over 200 years now, it’s been used in watches and small clocks although, it must be admitted, with certain small refinements. Not the least of which is the balance spring, now made to be temperature compensating.

Thomas Mudge was born in Exeter in 1715. He was the second son of the Rev. Zachariah Mudge, who moved his family to Bideford in Devon where he took up the post of headmaster at the grammar school there. Thomas attended the school until he was 14, when he travelled to London and became apprenticed to George Graham in the Clockmakers Company.

Mudge himself became a Freeman in the Company in 1738. In 1750, he opened his own business at 151 Fleet Street, the colourfully named Dial and One Crown. Matthew Dutton, another of Graham’s apprentices, joined him four years later as a partner. It proved a successful enterprise, and they made a important number of high end watches. However, it was those made by Mudge himself that were truly noticeable.

Another great clock maker, John Ellicott, the man who invented the compensating, or gridiron, pendulum, was travelling to the Spanish Royal Court, and Mudge gave him a perpetual calendar watch and a series of watches which showed the equation of time, to sell to the Royal Family.

In 1750, Mudge made a watch that repeated not only the hours and the quarters, but also the minutes. King Ferdinand VI was most taken with it and eagerly bought it. In 1754, he made his first experimental watch carrying the lever escapement.

In this kind of escapement, the teeth of the escape wheel are clubbed, or flattened, across the top. One could duplicate the same sort of arrangement by taking a file to the normal escape wheel and filing the tips off each tooth, leaving a flat surface. There are 15 teeth in a lever escapement wheel, and the escape wheel itself is about three sixteenths of an inch in diameter.

Mudge was the first one to use rubies for the pallets and roller jewel. This latter drives the escapement. The roller itself is approximately one eighth of an inch in diameter and about five sixty fourths thick. It’s set beneath the balance on the balance staff and oscillates with the balance. Set into it is the roller jewel. Nowadays, it’s usually formed in a D section, or half a course of action so that there’s sufficient clearance when it passes by the fork of the lever itself.

The point about this whole escapement is that when the roller jewel enters the fork of the lever, it drives it over to one side. Unlike an escapement such as a deadbeat or keep up in a place, the lever is momentarily free. Then it’s picked up by a tooth of the escape wheel and because of the angle of the tips if the teeth in relation to the pallets, the lever is drawn across and comes to rest against a pin. Then it’s incapable of moving back again, because of the roller itself coming into slight contact with a pin attached to the centre of the fork. When the lever moves over in that way, it’s called the run to the banking.

It’s extremely difficult to give you a clear picture of the workings of this escapement simply with words, but I hope I’ve managed to give you some small idea of how it operates.

In 1771, Mudge retired from London, and left the running of the business to Dutton. Mudge himself settled in the country, and poured all his energies into making a marine chronometer. He was granted 500 pounds, and in 1779 had produced two chronometers. Nevil Maskelyne, the Astronomer Royal, and the bane of many clock makers, considered both unsatisfactory, but it was felt by many that he didn’t give either a fair trial. Nevertheless, in 1776, Mudge was made Clockmaker to the King, who of course was George III at the time, 1776 being a most meaningful date

In 1792, Mudge was granted 2,500 pounds by a Committee of the House of Commons. He died on 14th. November 1794. His contributions to horology were highly useful, and his place in history is quite rightly obtain

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