A rotary fluid-displacement assembly, comprising: a housing (110; 410; 610) defining an internal cavity having an inner wall surface, wherein the housing has a housing longitudinal axis (Axis A) extending transverse to a housing plane that bisects the inner wall surface, and wherein the housing has a front surface and an opposed back surface; a rotor (150; 450; 650) having a peripheral surface and being positioned within the internal cavity of the housing, the rotor configured to rotate about a rotor axis of rotation (Axis B) eccentric to the housing longitudinal axis, wherein the rotor has a first side surface and an opposed second side surface; a gate (160; 260; 360; 460; 560a; 560b; 660) having a distal end, the gate being slidably mounted within the rotor and translates radially relative to the rotor about and between a first position, in which the distal end of the gate is positioned at a first distance from the peripheral surface of the rotor, and a second position, in which the distal end of the gate is positioned at a second distance from the peripheral surface of the rotor, wherein the distal end of the gate is constrained to be spaced proximate from the inner wall surface of the housing as the rotor rotates about the rotor axis of rotation; wherein at least portions of the peripheral surface of the rotor, portions of the inner wall surface and varying portions of the gate proximate the distal end of the gate define a fluid chamber (102; 104) of varying volume as the rotor rotates about the rotor axis of rotation; and wherein a pair of end plates (151a, 151b; 451b) are mounted to and rotate therewith the respective first and second side surfaces of the rotor; characterised in that portions of a first end plate of the pair of end plates sealingly and slidably contact portions of the front surface of the housing, and in that portions of a second end plate (151b; 451b) of the pair of end plates sealingly and slidably contact portions of the back surface of the housing. a housing (110; 410; 610) defining an internal cavity having an inner wall surface, wherein the housing has a housing longitudinal axis (Axis A) extending transverse to a housing plane that bisects the inner wall surface, and wherein the housing has a front surface and an opposed back surface; a rotor (150; 450; 650) having a peripheral surface and being positioned within the internal cavity of the housing, the rotor configured to rotate about a rotor axis of rotation (Axis B) eccentric to the housing longitudinal axis, wherein the rotor has a first side surface and an opposed second side surface; a gate (160; 260; 360; 460; 560a; 560b; 660) having a distal end, the gate being slidably mounted within the rotor and translates radially relative to the rotor about and between a first position, in which the distal end of the gate is positioned at a first distance from the peripheral surface of the rotor, and a second position, in which the distal end of the gate is positioned at a second distance from the peripheral surface of the rotor, wherein the distal end of the gate is constrained to be spaced proximate from the inner wall surface of the housing as the rotor rotates about the rotor axis of rotation; wherein at least portions of the peripheral surface of the rotor, portions of the inner wall surface and varying portions of the gate proximate the distal end of the gate define a fluid chamber (102; 104) of varying volume as the rotor rotates about the rotor axis of rotation; and wherein a pair of end plates (151a, 151b; 451b) are mounted to and rotate therewith the respective first and second side surfaces of the rotor; characterised in that portions of a first end plate of the pair of end plates sealingly and slidably contact portions of the front surface of the housing, and in that portions of a second end plate (151b; 451b) of the pair of end plates sealingly and slidably contact portions of the back surface of the housing.