Abstract: A multistage centrifugal pump has a rotatable shaft, a plurality of pump stages and a thrust module. Each of the plurality of pump stages has an impeller connected to the rotatable shaft and a stationary diffuser. The thrust module has a thrust runner and a unitary thrust pad. The unitary thrust pad has an axial wear face adjacent the thrust runner and a radial wear surface adjacent the rotatable shaft. The axial wear face and radial wear surface are integrated as a unitary component. The unitary thrust pad is secured to a thrust pad support with threaded fasteners that are torqued to a predetermined extent.

Abstract: A method of performing a logging operation at a wellbore includes providing first and second pipe segments respectively including a first internal electrical cable and a second internal electrical cable, connecting a first end of the first internal electrical cable to a wireline cable of a logging tool to form a drill pipe string, lowering the drill pipe string, including the logging tool and the first pipe segment, into the wellbore, connecting a first end of the second internal electrical cable to a second end of the first internal electrical cable to add the second pipe segment to the drill pipe string, lowering the drill pipe string, including the logging tool, the first pipe segment, and the second pipe segment, into the wellbore, and connecting a second end of the second internal electrical cable to a surface logging unit to couple the surface logging unit to the drill pipe string.

Abstract: A downhole assembly includes a first tubular including a first shoulder and a second tubular including a second shoulder. The assembly further includes a transmission element having a first portion disposed in the first shoulder, the first portion includes an electrically conductive member having a first arc length and a second portion disposed in the second shoulder. The second portion includes a contacting element having a second arc length that is substantially less than the first arc length and further includes an outer insulating carrier that defines a groove. The contacting element is disposed in the groove. When the first tubular is joined to the second tubular, the contacting element contacts the electrically conductive member and the second portion defines at least one region between the electrically conductive member and the second portion in areas of the groove where the contacting element does not contact the electrically conductive member.

Abstract: A downhole system includes a drill string having a drilling fluid flow channel and at least one turbine alternator deployed in the flow channel. The turbine alternator is configured to convert flowing drilling fluid to electrical power. A voltage bus is configured to receive electrical power from the turbine alternator and at least one electrical motor is configured to receive electrical power from the voltage bus. An electronic controller is configured to provide active control of the turbine alternator via processing a desired speed of the electrical motor to generate a desired torque current and feeding the desired torque current forward to the turbine alternator. The turbine alternator is responsive to the desired torque current such that it modifies the electrical power provided to the voltage bus in response to the desired torque.

Abstract: A multilateral entry tool enables an operator to identify a target lateral wellbore, and efficiently guide a bottom hole assembly (BHA) into the target lateral for diagnostic, servicing or other wellbore operations. The multilateral entry tool provides independent control over both kick-over and orientation mechanisms such that the operator may either pivot the BHA without rotating, or rotate the BHA without pivoting. The BHA may be rotated in either direction, and the degree that the BHA can be pivoted may be fully adjustable. Sensors on the entry tool may penult the operator to verify a successful lateral entry, and the BHA may be straightened to reduce drag as the BHA is advanced into the lateral wellbore.

Abstract: A bottomhole assembly may include a downhole motor and bearing assembly. The downhole motor may include a rotor and stator. The bearing assembly may include a bearing mandrel. The bearing mandrel may be coupled to the rotor by a transmission shaft. The bottomhole assembly may include one or more sensors positioned in the bearing mandrel, transmission shaft, or rotor. The bottomhole assembly may include a conductor that passes through one or more of the bearing mandrel, transmission shaft, and the rotor from the sensor to a communications package.

Abstract: In a snubbing operation, a method is used for determining when a wellbore should be circulated by comparing calculated torque and drag values from a clean wellbore against actual torque and drag values. In a more expansive application, for working a well, a method is used for optimizing performance of the drilling operation by comparing calculated torque and drag values from a clean well against actual torque and drag values.

Abstract: Apparatus and methods for bi-directional drilling using a bi-rotational bottom hole assembly. In preferred embodiments, the bottom hole assembly combines electric and mud motors. A central combination retrieval and electrical power cable supplies power to the motor and provides for retrieval of the bottom hole assembly to the surface. The pipe string is bi-rotational combination drill and casing pipe and connections.

Abstract: Provided is an apparatus for use in directional drilling, which apparatus comprises: (a) a drill bit; (b) at least one steering actuator capable of exerting a longitudinal force on the drill bit, so as to change the direction of drilling; and/or (c) at least one drill bit steering insert, capable of extending and retracting so as to change the cutting characteristics of the drill bit and thereby change the direction of drilling. Further provided is a method of directional drilling, employing the apparatus of the invention.

Abstract: An apparatus and method for alleviating spiraling in boreholes is disclosed. The apparatus includes a sub, which adjusts the length of the bottom-hole assembly in response to tension/compression, flexural bending and/or torque measurements made above and below the reamer so that the drill bit and the reamer cut at the same depth rate. The sub is connected between the drill bit and the reamer. The apparatus further includes measurement devices disposed on the bottom-hole assembly above and below the reamer, which are capable of measuring the tension/compression, flexural bending and torque in the bottom-hole assembly. The method includes use of a data processor, which determines which operational output signals to supply to the sub in order to adjust its length and thereby accomplish the desired drilling rates.

Abstract: The disclosure includes a method of placing a wireline device in a deviated well having a hydrostatic column, the method comprising placing a positioning device in a wellbore of the deviated well, electrically powering the positioning device, moving the wireline device across a deviated region of the wellbore using the positioning device, wherein moving includes creating a driving force using the positioning device, and wherein the driving force is at least one of: a mechanical driving force and a fluid pressure driving force.

Abstract: An apparatus for mounting one or more transducers to a drill pipe. The apparatus comprises a sub-pipe having a bore and a transducer-holding assembly, wherein the transducer-holding assembly is insertable into the bore of the sub-pipe from an axial end of the sub-pipe. The apparatus further comprising a tension collar connected to the bore-defining surface of the sub-pipe and bearing upon the transducer-holder.

Abstract: An electrical submersible pump assembly has a pump driven by a motor. A pressure compensator has first and second bellows units axially separated from each other. Each of the first and second bellows units are movable between an increased volume position and a decreased volume position and have a bias toward the decreased volume position. The bias of the first bellows unit is greater than the bias of the second bellows unit. The greater bias of the first bellows unit over the second bellows unit causes the second bellows unit to be at a full volume position at a lower level of the pressure differential than the level at which the first bellows unit is at the full volume position.

Abstract: A wired pipe system includes a wired pipe segment having a first end and a second end, a first coupler in the first end and a second coupler in the second end and a transmission line disposed in the wired pipe segment between the first and second ends. The transmission line includes a transmission cable that includes an inner conductor and an insulating material disposed about the inner conductor as well as a a wire channel surrounding the insulating material and the inner conductor for at least a portion of a length of the transmission cable. The wire channel and the insulating material are mated together by at least one mating feature.

Abstract: An example embodiment of a pipe-in-pipe electric motor assembly includes a drilling string that includes an inner pipe, an outer pipe, and an electric motor. The electric motor is provided with power supplied by the inner pipe and the outer pipe acting at least as conductors. A latching mechanism connects the drilling string and an electric motor output shaft. The electric motor output shaft is driven by the electric motor. The latching mechanism prevents the electric motor output shaft from rotating slower than the drilling string and associated methods.

Abstract: A downhole rotational rate control apparatus, adapted for coupling to the lower end of a drill string, includes a progressive cavity pump or motor, a mud flow control valve, and an electronics section. Drilling mud flowing downward through the drill string is partially diverted to flow through the pump or motor, with the mud flow rate and, in turn, the pump or motor speed being controlled by the mud flow control valve. The control valve is actuated by a control motor in response to inputs from a sensor assembly in the electronics section. By varying the rotational rate of the pump or motor relative to the rotational rate of the drill string, the tool face orientation or non-zero rotational speed of the controlled device in either direction can be varied in a controlled manner.

Abstract: A drilling system including a drill string, an EM telemetry assembly, and an electric contact assembly that defines an electrical connection with the drill string. The electric contact assembly permits a portion of the EM tool to slide along a portion of the drill string during drill string assembly.

Abstract: A pipe in pipe electric motor assembly comprising: a drilling string comprising an inner pipe and an outer pipe and an electric motor; wherein the electric motor is provided with power supplied by the inner pipe and the outer pipe acting at least as conductors and associated methods.

Abstract: An electrical device for well stimulation comprising a plurality of sections configured to be assembled, end to end, to form a tool. The tool comprises first and second electrodes. The second electrode is an electrically insulated peripheral electrode of the first electrode. The first and second electrodes of the tool forming, at one of the ends of the tool, a stimulation head. Additionally, one end of a body of a first section comprises a peripheral ring that is rotatably movable and translatably immobile relative to the body of the first section. The peripheral ring comprises a thread configured to engage with a thread of the second electrode of one end of a second section.

Abstract: The present invention relates to a downhole driving unit (11) for insertion into a well, comprising a driving unit housing (51), a hydraulic motor comprising a hydraulic motor housing (93), the hydraulic motor comprising a cam ring (24), a wheel assembly (90) comprising a stationary part (91) and a rotational part, the stationary part (92) being connected with the driving unit housing and a rotatably connected with a rotational part, the stationary part and the rotational part constituting the hydraulic motor housing, said hydraulic motor comprising a rotatable section (84) connected with the rotational part, the cam ring being connected with or forming part of the stationary part of the wheel assembly, the rotational part comprising a wheel ring (99), where in a bearing (36) is arranged between the cam ring and the wheel ring. The present invention also relates to a downhole system comprising the driving unit and to use of such driving unit.

Abstract: A method and system for steering a rotary steerable tool in a borehole. A method includes determining an azimuthal angle between a reference direction and a reference point on a direction determination component of a tool string. The direction control component is remote from the rotary steerable tool. The azimuthal angle and a time at which the angle was determined are communicated to a rotary steerable tool direction control system. A steerable shaft of the rotary steerable tool is deflected based on the azimuthal angle and the time at which the angle was determined, thereby directing the rotary steerable tool in a predetermined direction.

Abstract: A WD sidewall coring tool includes: an outer cylinder set (34); a retrieving mechanism (35); a drilling sealer mechanism (36); a power mechanism (37); and a coring mechanism (38); wherein the outer cylinder set (34) includes a stabilizer (1), a limiting connector (22), and a turning connector (23) connected in sequence; wherein the retrieving mechanism (35) includes a retrieving cylinder (39), a retrieving head set (40), and a steel rope (33); wherein the drilling sealer mechanism (36) includes a connecting rod (28), a universal joint (24), a plug sleeve (29), and a sealing plug (30); wherein the power mechanism (37) includes a flat thrust bearing (17), a screw stator (18), a screw rotor (19), a limiting piston (20), and a first spring (21); wherein the coring mechanism (38) includes a coring cylinder (25), a core grabber (26), and a coring bit (27).

Abstract: The present invention relates to a drill-pipe communication assembly. The drill-pipe communication assembly includes a first drill pipe and an insulated tube disposed within, and generally concentric with, the first drill pipe. A male insert is disposed within a first end of the first drill pipe and a female insert is disposed within a second end of the first drill pipe. A conductor is electrically coupled to the male insert and the female insert. The conductor extends along a length of the first drill pipe. The conductor facilitates transmission of electrical signals from the first end of the first drill pipe to the second end of the first drill pipe.

Abstract: A drill bit assembly that includes a shank including a shank axis, first and second ends, a drill bit seat at the second end and a central flow bore extending axially from the first end. Additionally, the assembly includes a sleeve disposed about and translatable axially relative to the shank and a drill bit rotatably coupled to the sleeve. The drill bit includes a first bit face having a first cutting structure configured to engage an earthen formation, and a second bit face having a second cutting structure configured to engage the earthen formation. The drill bit is configured to rotate about the about the shank axis in a cutting direction, and to rotate about an axis of rotation being orthogonal to the shank axis to selectively expose the first or second cutting surface to the earthen formation. The seat is configured to receive the first or second bit face.

Abstract: The present invention is a subsurface formation cutter for directional cutting into a subterranean formation. The subsurface formation cutter includes a transmission unit, a cutter bit, a bit brace, and a ram unit. The transmission unit has a driver shaft operatively connected to a bottom hole assembly. The cutter bit has a connector member, a cutter body rotatably coupled to the connector member, and a bit shaft connected to the cutter body. The bit shaft is operatively coupled to the driver shaft of the transmission unit. The ram unit has a moveable ram shaft connected to a traveling member. The bit brace is pivotably connected to the connector member and the traveling member. A connection member is attaches the ram unit to the transmission unit, and is configured to receive and guide the traveling member to travel in a direction parallel with a longitudinal axis of the subsurface formation cutter.

Abstract: The mining vehicle has a carriage, driving equipment for moving the carriage, at least one mining work device, an electric motor for supplying power to the mining work device, a connection for supplying electric power to the electric motor from an electrical network of the mine, and an energy source. The electric motor has at least a primary stator winding and a secondary stator winding galvanically isolated from each other. When the mining vehicle is connected to the electrical network of the mine via the primary stator winding, the electric motor is arranged, at least for a period of time, to supply power to the at least one mining work device and, at least for a period of the time, to supply power via the secondary stator winding for charging the energy source. A method for energy supply of a mining vehicle is also provided.

Abstract: A bottom hole assembly for a drill string has a mud motor and a mandrel. The motor has a rotor and a stator, and the rotor defines a bore for passage of conductors. The mandrel has a bore for passage of the conductors and for drilling fluid, and rotation of the mandrel rotates a drill bit. A shaft and universal joints covert orbital motion at the rotor to rotational motion at the mandrel. To pass the conductors from a sonde uphole of the motor to electronics disposed with the mandrel, an inner beam disposes in a bore of the shaft. This inner beam has an internal passage for the conductors, and seal caps dispose on each end of the inner beam to seal inside the universal joints. The inner beam and seal caps prevent drilling fluid passing from the motor and around the shaft from communicating in the shaft's bore.

Abstract: A method for forming a subsurface wellbore is disclosed. The method includes operating a drilling string in a first direction of rotation. A first motor located near the end of the drilling string is operated in a direction of rotation opposite that of the drilling string. A drill bit is rotated using a second motor that is coupled to the first motor.

Abstract: A pipe in pipe electric motor assembly comprising: a drilling string comprising an inner pipe and an outer pipe and an electric motor; wherein the electric motor is provided with power supplied by the inner pipe and the outer pipe acting at least as conductors and associated methods.

Abstract: A rotating control device for sealing about a drill pipe can include a seal which can sealingly engage the drill pipe, and a generator which generates electricity in response to rotation of the drill pipe while the seal sealingly engages the drill pipe. A method of generating electricity from rotation of a drill pipe can include sealingly engaging the drill pipe with a seal of a rotating control device, and generating electricity in response to the rotation of the drill pipe. A system for generating electricity can include a rotating control device which seals about a drill pipe while the drill pipe rotates, the rotating control device comprising a seal and a generator which generates electricity in response to rotation of the drill pipe.

Abstract: The present disclosure relates to a power isolation adapter which can enable the use of multiple power sources in a bottom hole assembly (BHA) by isolating the power sources on a tool bus while maintaining a communication bus across the BHA. Such power sources may be part of a measurement-while-drilling (MWD) module, such as a mud turbine generator, providing power as a DC signal. The power isolation adapter isolates the power sources by blocking DC signals, but maintains an AC communication bus across the BHA. The ability to use multiple power sources in a BHA thus allows for more complex BHA configurations that normally could not be powered using a single power source.

Abstract: A control circuit for a coiled tubing injector includes a circuit controller (14). One or more counterbalance vales (3) may be responsive to the circuit controller to prevent the tubing string from descending into the wellbore during rate of penetration movement. In one embodiment, a control valve (4) allows fluid to flow through a bypass line around the counterbalance valves when drilling in a weight-on-bit mode. Other hydraulic control circuits allow for the release of fluid pressure to control the injector hydraulic motor. In yet another embodiment, the control circuit regulates power to an electric motor of the injector.

Abstract: Shock waves produced during electro-hydraulic drilling can be reflected into a rock body where the reflected shock waves are converted from compression waves to tension waves, which are more efficient at breaking down the rock body. A system configured for electro-hydraulic drilling where shock waves produced during drilling are reflected into the rock body includes two electrodes and a shock wave reflector disposed at an electro-hydraulic drill head. The two electrodes are configured to (1) facilitate formation of a spark along a spark path spanning the two electrodes and (2) facilitate a pulse of electricity being passed through the spark to form a primary shock wave emanating from the spark path. The shock wave reflector is configured to reflect a portion of the primary shock wave such that the reflected shock wave is concentrated to a focal region within the rock body.

Abstract: In one aspect, a drill bit is disclosed that in one embodiment includes a pad configured to extend and retract from a surface of the drill bit, and a force application device configured to extend and retract the pad, wherein the force application device includes a screw driven by an electric motor that linearly moves a drive unit to extend and retract the pad from the drill bit surface. In another aspect, a method of drilling a wellbore is provided that in one embodiment includes: conveying a drill string having a drill bit at an end thereof, wherein the drill bit includes a pad configured to extend and retract from a surface of the drill bit and a force application device configured to extend and retract the pad, wherein the force application device includes a screw driven by an electric motor that moves a drive unit to extend the pad from the drill bit face; and rotating the drill bit to drill the wellbore.

Abstract: Various embodiments relate to bearing assemblies configured to enable removal and replacement of superhard bearing elements, and bearing apparatuses that may utilize such bearing assemblies. The disclosed bearing assemblies may be used in a number of applications, such as downhole motors in subterranean drilling systems, directional drilling systems, roller-cone drill bits, and many other applications. In an embodiment, a bearing assembly includes a support ring and a retention ring assembled with the support ring. The bearing assembly further includes a plurality of superhard bearing elements. The retention ring and at least a number of the superhard bearing element are collectively configured to restrict displacement of the at least a number of the superhard bearing elements.

Abstract: A motor includes: a rotor including an undulated surface; a rod disposed about the rotor; and a coil disposed about the rod to induce shape changes in the rod, which in turn impart forces to the undulated surface to rotate the rotor.

Abstract: Rotational locking mechanisms for drill string assemblies, bottom hole assemblies, and drilling motors are presented herein. A fluid-driven motor assembly is disclosed for use in a drill string to drill a borehole in an earth formation. The drill string includes a drill pipe and a drill bit. The motor assembly includes a housing that is configured to operatively connect to the drill pipe of the drill string to receive drilling fluid therefrom. A stator, which is disposed within the housing, is configured to rotate at a stator speed. A rotor is disposed within the stator and coupled to the drill bit. The rotor is configured to rotate at a rotor speed. The motor assembly also includes a rotational locking assembly operatively coupled to the rotor and the housing. The rotational locking assembly is configured to prevent the stator speed of the stator from exceeding the rotor speed of the rotor.

Abstract: An apparatus for use in a wellbore is provided that in one embodiment includes a load, a motor coupled to the load to provide electrical power to the load and an alternator directly coupled to the motor driving the motor. In one aspect, the apparatus further includes a switch between the alternator and the motor that in a first position connects the alternator to the motor in a first configuration that rotates the motor in the clockwise direction and in a second configuration that rotates the motor in the counterclockwise direction.

Abstract: Various embodiments relate to bearing assemblies configured to enable removal and replacement of superhard bearing elements, and bearing apparatuses that may utilize such bearing assemblies. The disclosed bearing assemblies may be used in a number of applications, such as downhole motors in subterranean drilling systems, directional drilling systems, roller-cone drill bits, and many other applications. In an embodiment, a bearing assembly includes a support ring and a retention ring assembled with the support ring. The retention ring includes a plurality of through holes. The bearing assembly further includes a plurality of superhard bearing elements, with each superhard bearing element inserted partially through and projecting from a corresponding one of the through holes of the retention ring. The retention ring and each superhard bearing element are collectively configured to restrict displacement of each superhard bearing element beyond a selected position in a direction away from the support ring.

Abstract: An apparatus and process is disclosed for drilling a borehole into a subterranean formation with reverse circulation of drilling fluid. A tubular drill pipe extends into a subterranean formation. A bottom hole assembly connected to the drill pipe includes a drill bit for excavating the subterranean formation. A downhole motor is adapted for receiving electrical power from a cable extending into the subterranean formation. A downhole pump is powered by the motor and is configured for reverse circulating drilling fluid from the annular space surrounding the drill pipe to the interior space of the drill pipe. The drilling fluid is pumped upwards in the drill pipe by the downhole pump to carry excavated cuttings upwards through the interior space of the drill pipe.

Abstract: Procedures and devices are described for electric energy generation from electrochemical use of substances for powering downhole devices. According to some other embodiments procedures and devices are described for electric energy generation from nuclear decay for powering downhole devices. According to some embodiments, the types of devices being powered are untethered or otherwise cannot benefit from direct power transmission from the surface. Examples of devices include small devices in downhole environments. Other examples of devices are sensors and other hardware such as flow control valves installed during completion. According to one example permanent and/or semi-permanent monitoring sensors make use of the energy generation techniques described herein.

Abstract: The present invention discloses a cutting tool integrated in a drillstring for enlarging a borehole, where the cutting tool at least comprises: one or more side mills (12, 13, 14) arranged along the axis of said drillstring in a reamer housing (11), where the side mills (12, 13,14) are adapted to be rotated relative to the tool housing (11) by individual driving means. The self driven rotational side mills may be dome shaped cones where expand radially out of the reamer housing (11), or may be a special non-circular dome shaped cones where rotates without expanding.

Abstract: An expandable reamer apparatus and methods for reaming a borehole, wherein a laterally movable blade carried by a tubular body may be selectively positioned at an inward position and an expanded position. The laterally movable blade, held inwardly by blade-biasing elements, may be forced outwardly by drilling fluid selectively allowed to communicate therewith by way of an actuation sleeve disposed within the tubular body. Alternatively, a separation element may transmit force or pressure from the drilling fluid to the movable blade. Further, a chamber in communication with the movable blade may be pressurized by way of a downhole turbine or pump. A ridged seal wiper, compensator, movable bearing pad, fixed bearing pad preceding the movable blade, or adjustable spacer element to alter expanded blade position may be included within the expandable reamer. In addition, a drilling fluid pressure response indicating an operational characteristic of the expandable reamer may be generated.

Abstract: A self-contained system for drilling a drainhole laterally to a wellbore that includes a drill head with a tool for boring a drainhole and a self-propelled device for advancing the head into the drainhole during boring; a relay unit lowered into the wellbore, arranged to position the drill head against the sidewall of the wellbore in order to initiate the boring of the drainhole laterally to the wellbore; a cable for supplying electric power to the drill head, reeled out from the relay unit; and a mechanical system for removing cuttings from the drainhole during boring, the debris removed falling downhole.

Abstract: A self-contained system for drilling a drainhole laterally to a wellbore that includes a drill head with a tool for boring a drainhole and a self-propelled device for advancing the head into the drainhole during boring; a relay unit lowered into the wellbore, arranged to position the drill head against the sidewall of the wellbore in order to initiate the boring of the drainhole laterally to the wellbore; a cable for supplying electric power to the drill head, reeled out from the relay unit; and a mechanical system for removing cuttings from the drainhole during boring, the debris removed falling downhole.

Abstract: A bottom hole assembly is run into the wellbore on slickline with a tractor to assist in movement of the bottom hole assembly through a deviation in either direction. The tractor can have retractable drive components and can be responsive to tension in the slickline to turn it on and to avoid overrunning the slickline if driving out.

Abstract: A downhole tool string, comprising a tool string bore and a drill bit located at the bottom of the tool string. The drill bit comprises a body intermediate a shank and a working surface. The working surface may comprise a substantially coaxial rotationally isolated jack element with a portion of the jack element extending out of an opening formed in the working surface to engage a subterranean formation. The tool string may comprise a driving mechanism adapted to rotate the jack. The clutch assembly disposed within the tool string bore may comprise a first end in communication with the jack element and second end in communication with the driving mechanism.

Abstract: Various embodiments of the present invention relate to bearing assemblies configured to accommodate non-uniform loading and misalignment with an adjacent bearing assembly. In one embodiment of the present invention, a bearing assembly for use in a subterranean drilling system is disclosed. The bearing assembly includes a support ring and a retention ring attached to the support ring, with the retention ring including a plurality of through holes. The bearing assembly includes a plurality of bearing elements each of which includes a superhard bearing surface. Each of the bearing elements is positioned in and extends from a corresponding through hole of the plurality of through holes. At least a number of the bearing elements are configured to restrict displacement through the corresponding through hole and away from the support ring.

Abstract: An electrically powered and controlled tractor system includes one or more electric gripper assemblies and one or more electric power train assemblies. Power and control signals for the gripper assemblies and power train assemblies can be delivered from a ground surface via a wireline. The gripper assembly employs a motor-activated lead screw and nut combination to expand passage-gripping elements, preferably by pushing the gripping elements radially outward from locations between opposing ends of the gripping elements. A failsafe mechanism can retract the gripping elements during a power interruption. The power train assembly employs a motor-activated lead screw and nut combination to expand and contract two or more telescoping members. The tractor system can include multiple tractor units that each includes one gripper assembly and one power train assembly. A tractor can include one power train assembly and two gripper assemblies.

Abstract: A method for the directional control of a rock-drilling ma-chine, the drilling unit (1) of the rock-drilling machine, which is located in a borehole (2), comprising at least a pi-lot drill bit (6) or an underreamer drill bit (8), the drill bit(s) (6, 8) being driven by an electric motor (10) via a gearbox (12), and the drill bit(s) (6, 8) being moved into the rock (3) by means of a feeding rod (4) extending from a feeding machine at the outside the borehole (2), and the drill bit(s) (6, 8), gearbox (12) and motor (10) being pivoted in a controlled manner about a steering axis (18) which is approximately perpendicular to the center axis (26) of the feeding rod (4).