Manufacturer: Urban Jürgensen
Year: Circa 2011
Reference No: Reference 11C
Movement No: 14
Material: Stainless steel
Calibre: Manual, Cal 8P detent escapement, 25 jewels
Bracelet/Strap: Leather
Clasp/Buckle: Stainless steel Urban Jurgensen pin buckle
Dimensions: 41mm Diameter
Signed: Case, dial, movement and buckle signed
Accessories: Accompanied by a blank Certificate of Origin, operating instructions, product literature and the book The Jurgensen Dynasty: Four Centuries of Watchmaking in Two Countries by John M.R. Knudsen
Provenance: From the private collection of Dr. Helmut Crott
Literature: The Jurgensen Dynasty: Four Centuries of Watchmaking in Two Countries by John M.R. Knudsen
Provenance
From the private collection of Dr. Helmut Crott
Catalogue Essay
A grail of chronometry and the result of a historical pursuit for precision, the detent (or chronometer) escapement is one of the most accurate types of escapements. Developed in the mid-18th Century, it was mostly used in marine chronometers.

In the detent escapement, the balance wheel swings undisturbed during most of its cycle, except the brief impulse period, which is only given once per cycle (which explains why the seconds hand is only moving 3 times per second for a frequency of 21’600 vibrations per hour). It runs virtually without friction and the escape wheel teeth do not require oiling.

The greatest downfall of the detent escapement was the fact that it was very sensitive to shocks and as such this escapement was found rarely in pocket watches and none in wristwatch format… until a genius dream team at Urban Jurgensen composed of Derek Pratt, Kari Voutilainen and Jean-Francois Mojon set out to create the world’s first wristwatch movement with detent escapement.

In 2003 Urban Jurgensen’s master watchmaker, Derek Pratt one of the greatest watchmakers that only the cognoscenti know of and a contemporary of George Daniels whom he helped perfect the co-axial escapement started working on a pivoted detent escapement in an existing Unitas caliber. After Pratt’s encouraging results it was decided to create a wristwatch movement with a pivoted detent escapement in series, enter Jean-Francois Mojon a movement constructor and watchmaker, to whom the project was handed over to. The third member of this incredible “galactic team” was Kari Voutilainen who was trusted with the difficult task of finishing, regulating and assembling the first series prototypes.

Finally, the UJS caliber P8 with pivoted detent escapement was introduced to an enthusiastic public at Basel Fair 2011.

Designed from the ground up, this groundbreaking movement has two barrels in series that provide a power reserve up to 72 hours (indicated by a differential system, also patented). The large variable-inertia balance is equipped with a free sprung balance. The profile of the escape wheel teeth has also been optimized in order to reduce the friction even more thanks to a greater rigidity and reduced inertia.

The weak point of the detent escapement – sensitivity to shocks – was addressed by designing a limiting plate (patented) that would permit—as its name implies—limiting any movement of the detent that would be caused by a shock. The very small detent itself was also designed in order to make it less sensitive to shocks. This shock resistance was Chronofiable tested (an independent laboratory that test the reliability of watches) having been subjected to 20,000 shocks during two weeks.

About 40 prototype movements were built with caliber P8. According to Urban Jurgensen archives 25 were either cased in steel, pink gold or platinum and each one with a different dial making each one unique. The majority of these finished watches were used for testing or presentations and never offered for sale.

The present steel example is from the collection of collector and scholar Dr. Helmut Crott who was pivotal in bringing Urban Jurgensen’s Detent Escapement wristwatches to the market after the untimely death of Peter Baumberger, the brand’s previous owner and the man who’s vision made this incredible movement a reality.