Device for Hydraulically operating a drive wheel of a wellbore tractor, e.g a motor, and related tractor, wellbore string, and method

A device for hydraulically operating a drive wheel of a wellbore tractor has in certain embodiments at least one cam, and a rotatable assembly arranged to be rotatable with respect to the cam about an axis of rotation. The rotatable assembly has at least one piston. The device also has a chamber and at least one supply port for supplying hydraulic fluid from the chamber to the piston for energizing the piston, the supply port being arranged to be moved between first and second positions relative to the cam. In the first position, the piston can connect to the supply port and be energized to impart force against the cam for producing forward rotation of the assembly. In the second position, the piston can connect to the supply port and be energized to impart force against the cam for producing reverse rotation of the assembly. Embodiments of a related distributor assembly, wellbore tractor, and method are also described.