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Pecqueur Motorists
Dual Time Differential Calibre LTM 5021

  By Hubert de Haro

To build a new watch movement, you need a dash of bravery and a whole lot of tenacity. Amid intense secrecy, a manufacturer based in the Val-de-Travers has just completed the first prototype of an incredible new mechanical movement. We set out on a voyage of discovery to learn more about the new LTM 5021 calibre, the first concrete evidence of the “Pecqueur Motorists” project.

The watchmaking ecosystem is not just about a few major groups. A number of independent businesses, producing no more than a hundred watches each year, prove every day that it’s still possible to design an original movement, by relying on a dense and dynamic network of suppliers. One of these, Le Temps Manufacture (LTM), offers six mechanical calibres – manual and automatic – entirely designed and developed in-house, to around 20 clients. This company, founded in the Val-de-Travers in 2008 by Sylvain Jacques, employs some 100 employees in Fleurier and Couvet.

This company of “motorists”, as they are sometimes known, was selected by Patrick Bornhauser, founder of BPM Group (Bornhauser Performance Motors, a different kind of “motorist”), to anchor the ambitious Pecqueur Motorists project. The first phase of this industrial partnership will come to completion in the spring, during the Geneva watch fair season, when the first Pecqueur watch, reserved for members of the Pecqueur Motorists Club, will be launched.

The Pecqueur LTM 5021 movement, top view
Onésiphore Pecqueur, a forgotten master of the mechanical arts

Despite his rather marvellous name, the work of clockmaker-scientist Onésiphore Pecqueur is virtually unknown. And yet, in 1828 he patented a mechanism that can still be found in practically every motor vehicle today: the differential. In the inventor’s own words, this mechanism “shares the power between both rear wheels without affecting their independence.”

Pecqueur, considered the world’s first automobile engineer, was head of the workshops of the Conservatoire des arts et métiers (National Conservatory of Arts and Crafts) in Paris. In 1823 he was awarded a gold medal at the Exposition des produits de l’industrie française (Exhibition of products of French Industry) for his “Pecqueur gears”, about which the jury opined, “make it possible to solve a host of mechanical problems, the answers to which are of direct relevance to the industrial arts.” This was an exciting discovery for Patrick Bornhauser, a mechanical enthusiast and great-grandson of a Swiss master watchmaker.

“The biggest challenge when developing this calibre was incorporating the ‘original’ differential in a watch movement, given its considerable size.”

Assembling the Pecqueur differential
The differential: the keystone

Hamdi Chatti, who is overseeing the Pecqueur Motorists watchmaking project, is unequivocal: “The differential will be the through line of all our watchmaking developments.” The brief for the first Pecqueur watch could not be clearer: it will systematically showcase this ingenious mechanism, which will also be the unifying theme of all watchmaking creations to come. The differential is the keystone of the edifice now under construction.

Exploded view of the differential mechanism inside the Pecqueur Calibre LTM 5021,
which will equip the first Pecqueur Motorists model to be unveiled this spring.

Such prestigious watchmakers as Philippe Dufour and Greubel Forsey have employed the same mechanism in some very special movements equipped with two escapements. The role of the differential in this scenario is to establish an average rate for the two escapements, a little like an old-fashioned weighing scale. It can be found under European patent application EP2264551B1, where its role is to optimise the power reserve function.

Nevertheless, the construction of the differential inside the Pecqueur Calibre LTM 5021 is radically different from that of its cousins. The key was to avoid the trap of creating an exact replica. “The biggest challenge when developing this calibre was incorporating the ‘original’ differential in a watch movement. Although the differential provides a significant advantage in terms of correction, we had to think about it very carefully from the very beginning, because of its considerable size,” explains Yoann Paulin, LTM’s project manager.

At first glance, the result achieved by LTM immediately brings to mind Onésiphore Pecqueur’s historic invention. By capturing the Pecqueur spirit, LTM’s engineers were able to reference its unique pedigree. This bold vision helped them steer clear of contemporary technical solutions. All aficionados of fine mechanics will appreciate the fact that the Pecqueur Calibre LTM 5021 is just 7.75 mm thick – a genuine tour de force given the volume of the Pecqueur gearing mechanism alone.

In 1828 Onésiphore Pecqueur, considered the world’s first automobile engineer, registered a patent for a mechanism that is found in every mechanical vehicle even today: the differential.

The Pecqueur LTM 5021 movement, bottom view
GMT at your service

The differential of the Pecqueur Calibre LTM 5021 fulfils a vital role for the traveller: it provides a second time zone. This function is sometimes called Dual Time, or GMT (Greenwich Mean Time) after the time at the Greenwich Meridian, which is where all 43 of the time zones currently in use worldwide originate. It’s also a nod to the first clock made by Onésiphore Pecqueur, which featured two dials, one showing standard time and the other sidereal time.

The Pecqueur Calibre LTM 5021 with GMT module
But how does a differential contribute to a GMT function?

“The point of using a differential in the Pecqueur Calibre LTM 5021 is so that the timing function is not disturbed when setting the second time zone,” explains Hamdi Chatti. In other words, the balance and spring assembly continues to vibrate while the user sets the Dual Time function. This solution has the great advantage of preserving the isochronism of the Pecqueur watch, which means that the rate of the escapement’s regulating organ remains constant throughout the 60 hours of the power reserve.

Time zone display of the Pecqueur Motorists watch

“The first push-piece sets the number of the time zone, while the second sets the time zone number and the hour of the second time zone simultaneously,” notes Yoann Paulin. And that’s the real beauty of the “Pecqueur complication”. It ensures a virtually instantaneous reading of the time in the second time zone, while preserving the accuracy of home time.

“The point of the differential in the Pecqueur Calibre LTM 5021 is that timekeeping continues unaffected when the second time zone is set.”

Final thoughts

The bold construction of the 100% Swiss Made Pecqueur Calibre LTM 5021 draws from a prestigious historical repertoire. Its engineers completely rebuilt the gears of the differential in the spirit of their inventor, Onésiphore Pecqueur.

The harmonious arrangement of the 237 components of the Pecqueur Calibre LTM 5021 is sure to be one of the most talked-about revelations of this spring. And that will no doubt please the connoisseurs and members of the Pecqueur Motorists Club.