This mechanism is the external-gear counterpart to the adjustable-angle internal drive. Instead of meshing inside a curved ring, the yellow gear works along the outside of a specially shaped green spur gear whose tooth geometry supports constant engagement. As the purple input block pivots the shaft, the yellow gear slides along the gear¡¯s curvature while still transmitting torque cleanly. The output gear rotates smoothly despite the shaft tilt, demonstrating a compact way to achieve flexible angular alignment without using a universal joint.

Components — Yellow external spur gear, green curved-profile spur gear, purple tilting input housing, input shaft, and supporting frame.

How it works — Rotating the input shaft turns the yellow gear, which meshes with the green spur gear on its outer surface. Because the green gear is shaped with a continuous curved tooth band, the yellow pinion can swing through a large angular range while staying fully engaged. As the shaft tilts, the contact point simply slides along the curvature without losing mesh, allowing torque to flow uninterrupted into the green gear regardless of input angle.

Applications — Adjustable tool heads, flexible couplings, variable-angle rotary drives, compact robotic joints, and small machinery needing consistent rotation across misaligned axes.

Why it matters — This design provides angular freedom while keeping the gearing rigid and backlash-free. It avoids the vibration and wear common in universal joints at high angles, offering a smoother, more compact solution when precise motion must be preserved through changing alignment.