This mechanism combines a rotating barrel cam with a helical groove to impose compound motion on the gear train. As the central shaft turns, the follower pin tracks the spiral groove, shifting the green gear sideways along the axis. Because the green gear meshes with the pink gear at a changing angle and position, its sliding rotation produces a non-uniform, continuously modulated output on the pink gear.

Components — Helical-groove barrel cam, green sliding gear, pink driven gear, central rotating shaft, yellow output disk, follower pin, and guide blocks.

How it works — When the barrel rotates, the follower pin is forced to move along the helical path, pushing the green gear to slide radially while also spinning with the shaft. This combination of translation and rotation changes the meshing geometry with the pink gear: sometimes the teeth engage deeper, sometimes shallower, and the lever arm varies as the gear shifts. The pink gear therefore speeds up, slows down, and twists in a complex pattern dictated entirely by the groove¡¯s profile. Once the groove completes a revolution, the green gear returns to its starting position and the cycle repeats.

Applications — Programmable motion mechanisms, indexing drives, decorative automata, variable-speed transmissions, packaging machinery, and systems requiring non-linear or choreographed rotation.

Why it matters — The helical groove allows designers to ¡°shape¡± motion without electronics¡ªevery nuance of the output is embedded in the geometry of the cam. This produces highly repeatable, intricate motion with only a few moving parts, ideal for compact mechanical automation.