In hitherto known embodiments of radial piston motor of the above-mentioned kind
, the piston force has been transmitted to each cam-follower roller via a piston rod which is similar in design to a conventional connecting rod. The roller hasheretofore been journalled at its mid-point in a bearing at the outer end of the piston rod and formed with roller ways on either side of the bearing. At its radially inner end, the piston rod has been journalled in the piston. The journalling of theroller means that the length of the roller increases with the width of the bearing in the rod. The width of the roller way in the motor housing becomes wider by a corresponding measure, and its mid-portion is therefore not fully utilized.