A planetary gearbox is a gearbox with the insight shaft and the output shaft aligned. A planetary gearbox can be used to transfer the biggest torque in the the majority of compact form (referred to as torque density).
The bicycle’s acceleration hub is a great example of a planet-wheel mechanism: Perhaps you have ever wondered how you can get so much power and features in such a little hub? For a three-speed hub, a one-stage planetary equipment system can be used, for a five-velocity hub a 2-stage. Each planet gear program includes a reduction state, a primary coupling and an acceleration setting.
In mathematical terms, the smallest reduction ratio is 3: 1, the largest is 10: 1. At a ratio of less than 3, the sun gear becomes too large against the earth gears. At a ratio greater than 10 the sun wheel becomes too little and the torque will drop. The ratios are usually absolute i.e. an integer number.
Whoever invented the planetary gearbox is not known, but was functionally described by Leonardo da Vinci in 1490 and has been used for years and years.