Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. A radial piston pump is an element of the hydraulic. At this pump the working pistons are in radial direction and symmetrical arranged around the drive shaft - in contrast to the axial piston pump. The stroke of each piston is caused by an eccentric drive shaft or an external eccentric tappet (e. g. stroke ring). When filling the workspace of the pumping pistons from "inside" (e. g. over a hollow shaft) so it''s called a inside impinged (but outside braced) radial piston pump (picture 1). If the workspace is filled from outside it''s called an outside impinged radial piston pump. The general mode of operation will be explained at the movement of one pumping piston by means of picture 1: The outer ring for bracing of the pumping pistons is in eccentrical position to the hollow shaft in the center. This eccentricity determines the stroke of the pumping piston.