- Magneto’s watch - the sleeping beauty IWC Ingenieur Ref. 3508

Magneto’s watch - the sleeping beauty IWC Ingenieur Ref. 3508

Nov 16, 2018,02:01 AM

Dear Purists,

From time to time we encounter watches which are sailing quite below the radar of the horological mainstream. A few of them mark glorious failures of the watchmaker, others show exceptional technological advances, and some just have been cutting edge in at least one horological aspect.

The Ingenieur 500,000 A/m represents all three of these points. The “Inge” was a commercial flop, but a technical highlight even by nowadays standards.

“During the early eighties, IWC had developed two exceptional amagnetic movements based on the ETA calibre 2892, the Porsche compass watch (ref. 3551 with calibre 37541 and 37542) and the “Minentaucheruhr” for the German Bundeswehr (ref. 3519 with cal. 3755AM). Now, IWC planned to commercialise the acquired technical know-how by developing an even more resistant calibre for a new leader model of their “Ingenieur” line. The goal was not to shield the movement against magnetic fields in a soft iron Faraday’s cage as in the previous models, but to make the movement itself amagnetic.

(Sounds familiar by today’s standards? Read on...)

The expectations were even surpassed when the new calibre 35790 set a new world record surviving a field of 3.9 million A/m (= 49,000 Gauss). These astonishing results were achieved by a set of technical innovations, including using rubies as rotor ball-bearings, a special amagnetic material for pallet fork and roller, as well as a new alloy (niobium-zirconium) for the balance spring.

In 1989 (or late in 1988) the new flagship was released, its name and case proudly stating the fact that the factory guaranteed it could resist magnetic fields up to 500,000 A/m. But soon technical problems emerged. The calibre 35790 proved to be very sensible to temperature changes. The troubles were caused by the hairspring whose new alloy lacked the isochronous characteristics which we take for granted in a modern watch. Basically, IWC ended up with a model which could keep accurate time even in the rare occasion when the movement was exposed to extremely high magnetic fields, but which stayed out of step in the more likely event of a sudden jump in temperature.

Of course, IWC tried everything to save its prestigious project. But its engineers found no solution how the niobium-zirconium balance spring could be mass produced with a reliable isochronous quality. For a time, each hairspring was individually tested for its temperature characteristics, and only the best suited were picked for production (only a few per mil according to M. Fitz). This testing procedure guaranteed that the “Ingenieur 500.000” met IWC high internal accuracy standards, but was of course very expensive. Most probably, it didn’t cure the fundamental problem of the movement’s susceptibility. After four years and less than 3000 pieces produced, IWC replaced the “500,000 A/m” with the ref 3521, a more conventional model, yet graced by an official chronometer certificate.”*

Even today the “Ingenieur 500.000 A/m” can be regarded as a sleeper. It’s in every respect a technologically extreme solution, and pretty rare: from the Mixte version only 290 pieces were made...

*) Kudos for Mr. Moeb, who collected these informations at his website http://www.moeb.ch/Ingenieur/10d_500000Am.html