Grasshopper skeleton clock ( # 2)

	My # 2 clock is fitted with a grasshopper type escapement, the one originally invented by John Harrison to win the £ 20,000 prize offered by the Board of Longitude for a clock able to compute the longitude of a ship at sea and with a maximum error of thirty nautical miles after a six weeks trip. As a matter of fact John Harrison's clock gave even better results. At the end of his voyage to Jamaica, Captain Digges master of HMS Deptford reported on the ship log the clock error : 5 seconds or less than 1 nautical mile. In John Harrison's escapement each pallet is freed by the action the escape-wheel tooth gives to the other pallet and giving them the characteristic movement of the grasshopper legs, after which the escapement name. With almost no friction between the teeth of the escape-wheel and the pallets there is no need of lubrication and virtually no energy dissipation.
The clock keeps so regular and constant motion, John Harrison was able to state its error was just 1 second in a month: an exceptional result for a pendulum which didn't move in vacuum. The clock I built, based on W.R. Smith design, is of classical English type; its winding lasts 8 days .The clock is fitted with fusee and maintaining power features; the pendulum frequency is 72 oscillations per minute.