A robotic device and mobility module for navigating through a passageway whose diameter may vary comprises a central support member, a first casing coupled to the elongate support member via a first expandable and collapsible linkage, the first casing having an external surface including a first movable track, and a second casing coupled to an opposite side of the elongate support member from the first casing, the second casing coupled to the elongate support member via a second expandable and collapsible linkage and including an external surface including a second movable track.