Grasshopper Escapement Long Case Clock MP 78
The Grasshopper escapement was invented by John Harrison about 1725, and was used by him and his younger brother James in all the long case clocks they made after that date, including the three famous marine chronometers known as H1, H2 and H3. The expression 'grasshopper' and refers to the unique action of the pallets when released from the escape wheel, with a kicking and vibrating action somewhat reminiscent of the back legs of the grasshopper.
John Harrison was no ordinary clock or watchmaker. He served no apprenticeship, and all of his timekeepers were quite different from those produced by orthodox craftsmen of his day. He was brought up as a carpenter in Lincolnshire, and his early clocks were indeed constructed to the highest skill in wood.
Harrison was responsible for some brilliant and unique ideas in clock design and construction. He invented the gridiron temperature compensating pendulum, the maintaining power to keep a clock running while being wound, the grasshopper escapement which was almost friction free and needed no oiling, balanced arms using roller bearings, and also the remontoire or automatic escapement rewind.
His first clock was a long case clock which was made in 1713 and his subsequent regulators are said to have had an accuracy within one second a month.
He responded to the Board of Longitude's offer of a prize for the first clock that could tell accurate time at sea. This was a formidable undertaking, overshadowed at the time of the almost certain success of the method of observing astronomical lunar angles promoted by the Rev N Maskalyn. It was to take John Harrison all of his life to eventually win the prize after personal communication with George III.
The Meccano Grasshopper Long Case Clock faithfully reproduces the unique grasshopper action acting on a 30 tooth escapement wheel, and is weight driven, and has a seconds pendulum.
This diagram shows the prototype Harrison grasshopper escapement
The Meccano equivalent in the long case clock
Detail of the construction of the escape wheel and teeth.
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