This mechanism is a spur-gear style differential. The outer ring gear drives a pair of purple idler gears, which sit on a carrier linked to the input. These idlers mesh with the yellow and orange side gears connected to the two output shafts. When both shafts experience equal resistance, the differential locks into a unified rotation. But when one shaft encounters more load, the idlers begin to spin on their carrier axis, distributing motion so the outputs can rotate at different speeds while conserving the overall angular momentum introduced by the input.

Components — Large gray ring gear, purple planet (idler) gears, green carrier frame, yellow side gear and shaft, orange side gear and shaft, rectangular end housings, and mounting posts.

How it works — As the ring gear turns, it carries the purple idlers around with it. When both output shafts resist equally, the idlers do not spin; they simply orbit, driving both yellow and orange side gears at the same speed. If one shaft slows due to load, the idlers begin rotating on their own pins, allowing the side gears to turn at different rates. This balancing motion lets torque be transmitted smoothly even when the two outputs disagree in speed or direction, exactly as in automotive differentials or load-balancing rotary systems.

Applications — Vehicle axles, robotics with dual-wheel drives, torque balancers, synchronized conveyor rollers, and any mechanism needing flexible motion sharing between two rotating outputs.

Why it matters — The spur-gear differential distributes torque intelligently using pure geometry¡ªno sensors, clutches, or electronics. It offers smooth compensation for unequal loads, making it indispensable wherever two rotating elements must cooperate yet remain independent.