Simulation
Inside the Classified PowerShift Hub
A two-speed planetary hub that delivers the gear range of a front derailleur from inside the rear wheel and shifts under full pedalling load, analysed with a physics-based model and test-rig validation that confirms efficiency above 99% across most of its operating range.
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The Concept
The Classified PowerShift hub removes the front derailleur from a road or gravel drivetrain by hiding a second gear ratio inside the rear hub. It keeps the clean look and chainline benefits of a 1x drivetrain while recovering the gear range the front derailleur used to provide. The mechanism is a two-speed planetary gear system with six planet gears. In direct drive at 1:1 ratio, the planetary stage locks as a single rotating unit, with no relative gear motion inside the hub. In the reduced ratio of 0.686, the sun gear is held fixed and the planet gears transfer torque between the cassette and the wheel — delivering a chainring jump roughly equivalent to moving from a 52-tooth to a 36-tooth ring.
What sets the hub apart operationally is that this shift is near-instantaneous and can be performed under full pedalling load. On steep or punchy terrain — where a conventional front shift is slow, unreliable, or simply unavailable under torque — that changes the practical calculus of gear selection.
What the Animation Shows
The animation resolves the internal kinematics of the hub in both ratios: the planetary set locked as one body in direct drive, and the fixed sun gear with orbiting planets in the reduced ratio. It is the mechanism that lets a single compact cylinder at the centre of the rear wheel stand in for an entire second chainring.
Beyond the Hub
The hub is the enabling component, not the whole story. A single-chainring setup with a constant, optimized chainline reduces chain articulation at the cassette and the friction that comes with it, while eliminating cross-chaining lowers bottom bracket forces. Its mechanical efficiency — characterized with a physics-based model and confirmed on a purpose-built test rig — stays above 99% across most of the operating range, strongest in the high-power, low-speed conditions of a steep climb, exactly when the reduced ratio is engaged. Together these effects give the Classified drivetrain a system-level advantage that the headline efficiency figure alone understates. Sometimes the most elegant engineering is the kind you never notice while riding.
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