A planetary gearbox is a gearbox with the input shaft and the result shaft aligned. A planetary gearbox is used to transfer the largest torque in the the majority of compact form (referred to as torque density).

The bicycle’s acceleration hub is a good exemplory case of a planet-wheel mechanism: Perhaps you have ever wondered how you can get so much power and capabilities in such a small hub? For a three-rate hub, a one-stage planetary equipment system can be used, for a five-rate hub a 2-stage. Each planet gear program includes a reduction state, a primary coupling and an acceleration mode.

In mathematical terms, the tiniest reduction ratio is 3: 1, the largest is 10: 1. At a ratio of less than 3, sunlight gear becomes too large against the planet gears. At a ratio higher 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 isn’t known, but was functionally described by Leonardo da Vinci in 1490 and has been used for years and years.