Wheel system type
There are two main types of gear trains: fixed-shaft gear trains (fixed-axis gear trains or fixed-shaft gear trains) and planetary gear trains (moving-axis gear trains or epicyclic gear trains).
Fixed axle gear train
When the gear train is running, if the position of the axis of each gear relative to the frame is always fixed, the gear train is called a fixed-axis gear train.
The fixed-axis wheel system is divided into a plane fixed-axis wheel system and a spatial fixed-axis wheel system.
When the gear is running, the axis of the gear rotates relative to a fixed axis or plane, then this gear train is called a revolving gear train.
The epicyclic gear system is divided into differential gear system and planetary gear system.