The DOT concept for offshore wind energy is a seawater hydraulic network where turbines are directly coupled to a centralized hydro-power platform. The essential missing component is a low-speed hydraulic pump that uses seawater as its hydraulic medium. This low speed hydraulic pump is currently being designed and tested by DOT, where novel machine components have been developed. This paper describes the development of an interface between an oval running track which is used as eccentricity to actuate a hydraulic piston. Several approaches have been performed as well as prototyping and validation steps. These steps as well as the design approach are presented in this work.@en