Fidget Spinner With Planetary Gear

grabcad

A metallic "Precision FIDGET SPINNER" offers double action use. Hold the middle hub between thumb and finger to speed up the internal gearwheel, causing three external ones to rotate in unison. Alternatively, fix an outer gearwheel and spin its carrier with the three external ones, resulting in all spinning at triple speed on their axes. Note that involute gearing has no isogonic rotations. Two animations were made using "KeyShot 4.6" to illustrate these actions. The ball bearings measure 22mm/8mm (height: 7mm), and the internally-toothed gearwheel features a modulus of 1.25mm, 72 teeth, and a pitch circle diameter of 90mm. Externally-toothed gearwheels have 24 teeth each and a pitch circle diameter of 30mm. The theoretical center distance is 30mm, while the practical one is slightly less at 29.8mm. The gear ratio for internally-driven gears is 1:3. The model is available in STEP format, PTC Creo Parametric 2.0 native files, and as a zipped folder.