Abstract: As a serial element of a drill string, the drill string is adjustably bent by rotating one end of the sub relative to the other end. The opposite ends rotate about a tilted center line such that in one rotational position the sub is straight. One half turn of one end relative to the other bends the sub to the maximum angle. Between straight and maximum bend, any angle can be achieved by control of the amount of the relative rotation between the opposite ends of the sub.

Abstract: A by-pass valve is part of an apparatus arranged to function as a serial element of a drill string. An arbor is attached to the top end of a tubular motor rotor and extends some distance along the generally central opening of the housing which is attached to the top end of the motor housing. A head on the arbor comprises a normally closed valve which is capable of conducting fluid from inside the housing to the well annulus outside the drill string by way of the bore of the tubular rotor. The valve is opened by downward movement, in excess of a selected amount, of the rotor of the motor. The excessive downward movement of the rotor indicates problems in the motor bearing structure, or disruptive failure elsewhere in the bottom hole assembly. The opening of the by-pass valve reduces standpipe pressure which is a signal detectable at the surface. The signal indicates disruptive failure in the down hole assembly.