Two stage planetary gearbox 3D model

In general two stage gearbox means in which the torque is stepped down or up twice that is using two pairs of gears. But if we use this term in case of an automobile gearbox , then the meaning then a lot more comes into play. Gear boxes are used to get variable output torque as per requirement. This type of gearing is sometimes used in tractors and construction equipment to provide high torque to the drive wheels. In bicycle hub gears, the sun is usually stationary , being keyed to the axle or even machined directly onto it. The planetary gear carrier is used as input