Electric generator having a liquid coolant system

An electric generator machine comprising a liquid coolant system and a shaft, at least part of the shaft being rotatable about a rotation axis, the shaft including a first part having an axial channel therein, the axial channel including an opening in an end of the first part, the shaft including a second part received in the axial channel via the opening and engaged coaxially with the first part, the second part defining a liquid channel therethrough, the liquid channel hydraulically connecting the liquid coolant system to the axial channel, the liquid channel extending from an opening defined in a base of the second part to an opening defined in an appendix of the second part, the base at least in part disposed outside of the axial channel, the appendix disposed in the axial channel and defining a space between the appendix and an inner surface of the first part, the space being part of the axial channel, the opening defined in the appendix being open to the space, the first part being rotatable relative to the second part about the rotation axis with a helical feature disposed between the first part and the second part to define a helical pump between the first part and the second part, the helical pump being hydraulically connected to the liquid coolant system.