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This is a high-quality generic mainspring specifically designed for the Cartier in-house Caliber 1904 MC and 1904-PS MC automatic movements. Introduced in 2010, the caliber 1904 MC was one of Cartier‘s first fully in‑house automatic calibers, named after Cartier’s first wristwatch for Santos Dumont in 1904.
It measures 25.6mm (11½‴) in diameter, 4mm in thickness, and consists of 186 parts and 27 jewels. The movement features an innovative twin‑barrel system, which delivers a consistent torque for a power reserve of approximately 48 hours while ensuring chronometric precision over extended running periods.
About Caliber 1904 MC: The 1904 MC is one of Cartier’s first entirely in‑house automatic calibers, developed and manufactured at their La Chaux‑de‑Fonds manufacture. It is named after 1904, the year Cartier created the first modern wristwatch for the Brazilian aviator Alberto Santos‑Dumont. The caliber debuted in the Calibre de Cartier collection and later expanded to Drive de Cartier, Ronde de Cartier, and other lines.
Twin‑barrel System: The 1904 MC movement’s signature technical feature is its twin‑barrel configuration, in which two barrels work in parallel to maintain a balanced mainspring torque over extended running periods. This design significantly improves timekeeping stability by avoiding the torque drop typical of single‑barrel calibers in the latter part of the power reserve.
Technical Specifications: Frequency 28,800 vph (4Hz), 27 jewels, 186 parts, Glucydur antimagnetic balance, Nivarox flat hairspring, Incabloc shock protection, power reserve approx. 48 hours.
Q1: Does my 1904‑based Cartier always need mainspring replacement during service?
A: Not always. If the watch shows no drop in power reserve, amplitude is healthy (260°–300°), and winding feels smooth, replacement may not be necessary. However, for movements over 8–12 years old, many watchmakers recommend proactive replacement of both mainsprings to ensure long‑term stability and avoid the risk of breakage.
Q2: Does this generic mainspring provide the same torque curve as the original?
A: This product is engineered to deliver a torque curve closely matching the original to maintain balance between the twin barrels. After installation, a professional can verify performance by checking amplitude (target 270°–310° at full wind) and daily rate – if within Cartier factory tolerances, the replacement is successful.
Q3: Can I remove and reinstall the mainspring if I make a mistake?
A: Not recommended. Once a mainspring has been compressed and run in the barrel, the contact points at the inner and outer coils undergo micro‑elastic deformation. Reusing it is risky – slipping or breakage is much more likely. Always install correctly the first time.
Q4: Do I really need two mainsprings? Can I replace just one?
A: The 1904 MC’s automatic winding system relies on torque balance between the two barrels. Differences in elasticity between a new spring and an old one will cause uneven loading on the intermediate wheel, accelerating wear and degrading stability. It is strongly recommended to replace both springs simultaneously for optimal performance.
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