Armin Strom had the desire to transmit equal force to the balance, thereby increasing the consistency of rate. The brand developed an ingenious stop-works declutch system that operates inside the mainspring barrel to limit the torque delivered to the balance, providing smooth power delivery. Utilizing a Geneva wheel mounted to the barrel housing cover, the rotation of the mainspring barrel is limited to just 9 full turns. This represents the central 72% of the mainspring’s potential torque curve, the flattest and most consistent portion.
As the barrel housing unwinds around the arbor, a pin counts off the rotations on the Geneva wheel until it reaches the locked position and prevents further unwinding. This limit keeps the power delivery to the balance as consistent as possible and the amplitude in optimal range. Once it reaches the upper limit, the declutch mechanism guarantees the slip of the mainspring and allows the micro rotor to turn evenly when fully wound.
This innovative solution can be found in the Armin Strom Gravity Equal Force model from the System 78 collection.
