Abstract: A body and driveshaft extension for down hole drilling motors to allow the down hole assembly to operate as part of a drill string responsive to selected manipulations of the drilling fluid flow rate, carried out at the earth surface, to assume either a straight hole drilling configuration or a directional drilling configuration by choice of the driller.In the directional drilling configuration, the drill head driving output shaft rotates about a centerline deflected from the motor general centerline. The point of deflection is between the drilling motor and the drill head.

Abstract: A body, functioning as a length of drill string, has an eccentric roller mounted for rotation around the body. The roller and body have cooperating cam surfaces that cause the roller to reciprocate axially when the body rotates relative to the roller. In use, the extended radius of the eccentric roller engages the near side of the well bore walland tends to become stationary relative to earth. The forced axial motion of the retarded roller induces some peripheral motion at each turn of the drill string. The eccentric roller turns freely with the drill string when the extended radius is adjacent the far side of the well bore wall. The extended radius of the roller tends to spend most of the drilling time between the drill string and the near side, or low side, of the well bore to aid in well bore deviation control.