This speed reducing system is based on an ingeniously simple principle. The speed reducer has only three major moving parts: the high speed input shaft with an integral eccentric cam and roller bearing assembly; the cycloid disc; and the slow speed output shaft assembly. The smooth, progressive rolling action of the cycloidal disc eliminates friction and the pressure points of conventional gears. All of the torque transmitting components roll, and are symmetrically placed around the shaft for balanced, smooth, and quiet operation.
Unlike many other drive mechanisms the cycloidal drive is not backdrivable, the input and output shafts of the cycloidal drive can not be reversed. This is because rotating the output pins will not rotate the cycloidal disc in the correct way.
Also, the eccentrically mounted cycloidal disk will cause vibration in the drive which will propagate through the drive/driven shafts. This will also cause increased wear on the exterior teeth of the cycloidal disk, as well as the interface with the output roller pins due to small relative motion caused by the vibrations. A second cycloidal disc installed a half-rotation relative to the first will balance the input shaft and reduce vibration.
A video of gearless speed reducer which describes major parts of this mechanism
A student project which show components of a gearless speed reducer.
You can watch fallowing video for detailed description of this speed reducer.