An electric machine (10) comprises a rotor (14a, b) having permanent magnets (24a, b) and a stator (12) having coils (22) wound on stator bars (16) for interaction with the magnets across an air gap (26a, b) defined between them. The bars (16) and coils (22) are enclosed by an annular stator housing (42a, b) that extends between the air gap. A chamber (52, 54, 56) is defined that incorporates cooling medium to cool the coils. The stator housing comprises two mating clamshells (42a, b) that mount the stator bars and coils in the machine. Each clamshell is molded from reinforced plastics and interconnected (optionally through one or more intermediate components). At least one clamshell has over-molded therein stator bar shoes that form part of said radial wall, and optionally one or more of the following components: cylindrical boss supports extending along the cylindrical outer wall part; connection studs that communicate electrically the chamber externally; stator coils; coolant inlet and outlet ports; and an outer race of a rotor bearing.