A planetary gearbox is a gearbox with the input shaft and the output shaft aligned. A planetary gearbox is utilized to transfer the largest torque in the the majority of compact form (known as torque density).
The bicycle’s acceleration hub is a superb exemplory case of a planet-wheel mechanism: Have you ever wondered how you can get so much power and features in such a little hub? For a three-velocity hub, a one-stage planetary equipment system can be used, for a five-rate hub a 2-stage. Each planet gear system has a reduction state, a direct coupling and an acceleration setting.
In mathematical terms, the tiniest reduction ratio is 3: 1, the largest is 10: 1. At a ratio of significantly less than 3, sunlight gear becomes too large against the planet gears. At a ratio greater than 10 sunlight wheel becomes too small and the torque will drop. The ratios are usually absolute i.e. an integer number.
Whoever invented the planetary gearbox isn’t known, but was functionally described simply by Leonardo da Vinci in 1490 and has been used for years and years.