Input: green face gear
Output: orange face gear that rotates faster that the input.
Assembling face gear drives is easy in comparison with bevel gear drives.
The tube is cut off half for easy understanding.
It is possible to get input and output velocities equal by selecting appropriate tooth numbers of gears and pinions to meet equation (Z2/Z1)*(Z4/Z3) = 1
Z1, Z2 are tooth numbers of gear and pinion for the outer drive respectively.
Z4, Z3 are tooth numbers of gear and pinion for the inner drive respectively.
The mechanism is used to couple the vertical shaft in the tube, with another drivetrain having a horizontal shaft to share torque. This is used in an integrated axes wind turbine concept for torque transmission at high wind speeds (US patent 14992022-developed by Bal Govind and Vignesh Gurumurthy).