A cycloidal drive or cycloidal planetary gearbox quickness reducer is a mechanism for reducing the quickness of an input shaft by a certain ratio. Cycloidal rate reducers are capable of fairly high ratios in compact sizes. 
The input shaft drives an eccentric bearing that subsequently drives the cycloidal disc within an eccentric, cycloidal motion. The perimeter of the disc is targeted at a stationary ring gear and has a group of output shaft pins or rollers positioned through the face of the disc. These result shaft pins straight drive the result shaft as the cycloidal disc rotates. The radial motion of the disc isn’t translated to the result shaft.