Gravity Equal Force

Launched in 2019, the System 78 Gravity Equal Force tackles a classic problem in mechanical watchmaking — the mainspring's driving force, which progressively decreases as the spring unwinds, affecting precision — without resorting to the best-known historical solution, the fusee-chain, which is bulky and complex to produce at scale. Armin Strom instead developed its own more compact "constant force" system, one that could be integrated into a compact automatic calibre.

The mechanism, called "declutch stop-work," works by limiting the mainspring barrel's useful rotation to just 9 of the 12.5 physically possible rotations: a mechanical stop disengages the barrel beyond this range, preventing use of the portion of the wind where the delivered torque would drop below the threshold needed for stable precision. The result is a more even energy delivery across (almost) the entire stated power reserve, without the mechanical complexity and production costs of a traditional fusee-chain.

The ASB19 calibre housing this system is also Armin Strom's first "compact" automatic movement with a micro-rotor and barrel-motor, fitted in a 41 mm case — the smallest ever produced by the brand at that point — a clear sign of intent to broaden the manufacture's audience beyond pure complication enthusiasts, toward an everyday automatic watch with genuinely substantial technical content.