Eterna released a new model- the Eterna Madison Spherodrive in 2010. This watch has a stainless steel case, measuring 35mm x 38mm x 10mm, with a sapphire crystal and display back. A self-winding Eterna in-house caliber 3505 with 17 jewels, 28,800bph beating, and a 56 hours power reserve constitute the movement of the Eterna Madison Spherodrive. Other features, including a water resistance to 50 meters and visibility of the inside machine system, are nothing new. But the Eterna Madison Spherodrive are indeed an innovative model for its ball bearing-mounted low-friction rotor system, which was introduced in 1948 as a breath breaking astonishment in the watch industry.
As a development of the “Eterna Matic”, the ball bearing-mounted barrel is applied to the new timepiece. Patrick Kury, the Eterna’s Technical Director, explained: “This dual ball bearing represents a quantum leap in the quality of the gear train mechanism.” We know, the conventional winding mechanism operates the movement running on the basis that the barrel revolves around the static arbor, which delivers a steady supply of energy to the gear train, while this process results in great pressure on the arbor, which will certainly reduce the useful time.
In Eterna’s improved system, the winding process has been separated from the gear train. Two ball bearings support the winding stem integrated into the winding mechanism, while a ball bearing incorporated in the gear train mechanism supports the spring barrel, which has no direct connection with the winding process. This innovative development reduces the friction and maintains the energy in rolling motion. Above all, the ball bearing-mounted rotor system, compared to conventional designs, can reduce vertical play and cant by up to the factor of ten, simply and efficiently.