The Spring Detent Escapement

Created to give the "exact" time to generations of seamen, to enable them to sail across the seas. The variant shown here - the Spring Detent escapement, was created mainly by Ferdinad Berthoud



Awful weather
This is the beginning of one chapter in the book "Longitude" by Dave Sobel, where the tragically events of Admiral Shovell and 2000 of his seamen is told. It happened in 1707, when continuous daily fog put the victorious fleet of association the Eagle, the Romney and... home into great standby. The reason for it was, that in those days mankind was not able to make out the exact position of a ship on the open sea. This inability of locating the exact position caused the just mentioned tragedy. Only because Admiral Shovel and his officers did not know the position of their fleet but had to decide which course to take. They made the wrong decision with the result that all ships mentioned above were run to the ground at "Land's End" and ...
The Price
Everybody knew, that it could not go on like this. Too many people had to die, too much precious load was lost, too much was at stake at naval wars; only because no Captain was able to make out the exact position of their ships on the open sea, without being able to see land. It was the British government, that put a price on the solution of this problem (a real big reward). Now they were looking for methods that were to help making out the exact position of a ship approximately 30 sea miles of shore.
The solution
Of the countless solution methods that were then represented, only two seemed possible. At one of them the constellation of certain celestial bodies were measured and observed; calculations that lasted for hours were carried out and with these results and extensive books of tables the position of the ships could be determined. In the case of the other method, the altitude of the sun was ascertained at a certain time and then found the longitude with the aid of tables readings of appropriate co-ordinates. In those days the first method was possible, but could only be carried out by a few, because the calculations were almost too extensive for the average human being. It was not unusual that the same calculation was worked out three times, each time with a different result. The second method was easy really, but impossible, as there wasn't such a clock that could give the exact time when the altitude of the sun was ascertained. But it only took 50 years until an ex-carpenter, that turned into a horologist represented the solution of the time. It was John Harrison, that unflustered the impossible into possible. He created a clock that was accurate enough to give the seamen the correct time. He introduced the age of the chronometer.
The heirs
As John Harrison showed that it was possible, the following generations concentrated on making it available to everyone and to design Chronometers in such a way that they were very accurate, very secure and reasonable. They could only be exact though, if they did not need any oil, as oil grew old quickly and than caused disturbances in the flow of power to the balance. Secure means, that the functioning was not allowed to be disturbed due to long usage (wear). Reasonable: That required a simple construction because complicated mechanisms caused a lot of work at manufacturing and therefore would have been expensive. The escapement shown here is one of two variants that gained acceptance, that were build into many chronometers that have definitely saved many seamen's life's.