A spindle motor structure includes a rotor, a stator accommodated mainly inside the rotor, and an internal roof magnet located on an inner roof surface of a rotor bell of the rotor. Such methods include use of directional drilling equipment which include a drill string with a hollow bottom rod connected to a boring tool by means of an obtuse-angle connection piece or \u201cbent sub\u201d. A pair of meshed gears is disposed in the pump chamber and separate the pump chamber into a fluid inlet area and a fluid outlet area accessible through respective inlet and outlet ports in the pump housing.