Patent Publication Number: US-11021186-B2

Title: Movable rig and steering system

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 15/349,661, filed Nov. 11, 2016, which is a continuation-in-part of U.S. patent application Ser. No. 15/285,946, filed Oct. 5, 2016, the disclosure of each are hereby incorporated by reference herein in their entirety. 
    
    
     FIELD OF THE INVENTION 
     The present application is generally directed to oil rig assemblies. Particularly, the present application relates to movable oil rig assemblies that may include moving systems and may be driven. More particularly, the present application relates to a movable rig having steerable wheel assemblies allowing for driving the rig in any direction. 
     BACKGROUND 
     Rigs drilling in the high Arctic may include sealed units to retain heat during drilling operations and rig moves. These rigs may move as a convoy of trailers towed by trucks and self-propelled units as they move between pads in the high Arctic. The typical rig move between pads may be several hundred yards or several miles. The complete rig may also move from well to well on the pad during drilling operations. During rig moves, the loads may be maintained below the tire capacity, bridge capacity, ice road capacity or other limiting factors. In some rigs, each of the 4 corners of the drilling modules may include 2 tires and two hydraulic drives all mounted onto a trunnion style suspension. The rig may include 4 trunnions in total and the rig may include a vertical hydraulic lift cylinder over each of the trunnions. 
     One style of rig for the Arctic drilling is a cantilevered style. In a cantilevered style rig, the drillfloor, mast, and well center may be cantilevered out over the well and wellhead to provide suitable vertical clearance for drilling operations. The cantilevered nature of the rig may enable the rig to traverse along a row of wells completing each well as it moves parallel to the wells. 
     These large drilling rigs and modules may be driven utilizing hydraulic motors. Hydraulic moving systems use several hundred gallons of hydraulic oil under pressures of 5000 psi and high flow rates to enable hydraulic motors to power each of the 8 tires. This hydraulic system may provide the tractive effort to move the rig. In an environmentally sensitive area such as the shoreline of the Arctic Ocean, the risk of a large environmental oil spill exists and may be caused by the high pressure and high flow rate of these hydraulic systems. The volume of hydraulic fluid used in these systems to move the rig is substantial and the risk of a hose failure or other substantial leak is great. 
     The steering mechanisms of these rigs may be known as Akermann steering and it may include a steering bar and hydraulic cylinders. This particular system of driving and steering can lead to tire scrubbing, notably while turning a corner, because the outside tires travel at a different RPM than the inside tires. These differing speeds of the tires at each corner of the drilling module cannot be controlled easily with hydraulics. Additional issues with the Akermann approach is that this steering system cannot rotate each of the 4 wheel sets 90 degrees without removal of the Akermann steering bar which can exceed 15 feet in length and 1000 pounds in weight. User intervention is commonly required and the Akerman steering bar is typically replaced with a different steering bar to provide for 90 degrees of travel. This current style of moving systems cannot enable the drilling module to travel at angles between the longitudinal direction and the transverse direction. 
     Current drilling modules have Akermann steering in the front and the back of the rig. The current steering geometry does not allow for the wheel sets at the front of the drilling module and the rear of the drilling module to steer together and point to one turn center for proper geometry, while the unit is negotiating a curve while travelling in a longitudinal direction. The turn center only works with current designs with either the front or rear steer acting alone, and pointing to the turn center, for proper geometry. This causes the turning radius of the drilling module vehicle to be larger, and more difficult to maneuver. Without proper steering on a tight curve, as the drilling module traverses the curve, tires may walk off the rims because each tire travels about a different center of rotation. This can be caused by the driver using both front and back steering mechanisms at the same time when each mechanism is not designed for such use. Thus, each tire follows a different radial path rather than a series of concentric radial paths that all converge to the same center point. The tire scrub produced by a lack of steering geometry with all wheel steering, can cause the tires to separate from the rims. 
     The tires on these rigs may be 40×57 tires and may have a pressure of 120 psi while loaded with over 100 tons per tire. Any excessive flexing of a tire while it is moving, produces heat. Excess heat can cause a tire failure. A tire failure of this size of tire could rupture the moving system hydraulic hoses, and cause an environmental spill on the tundra next to the Arctic Ocean. Moreover, this can result in a dangerous situation where, for example, an explosive tire deflation caused by tire/rim separation occurs and/or stability is reduced. In particular, where the rig includes a very tall vertically extending mast riding on it, the risk of overturning and catastrophic failure may be great. The overall height of the drilling module may exceed 230 feet and placing such a structure at risk of toppling is a grave concern. 
     SUMMARY 
     In one or more embodiments, an electric drive, hydraulic steer, moving system may enable a drilling rig with a gross vehicle weight of 1000 tons to be driven on 8 tires, utilizing its own power and in any direct. For example, the vehicle may be drive in any direction ranging from 0 to 90 degrees. The system may be capable of perfect steering while travelling in a longitudinal direction. The rig may also travel under its own power in a transverse direction. The rig may also travel under its own power at any angle between the transverse and longitudinal direction. At any direction past the longitudinal direction, the unit may include the ability for steering correction during this travel. 
     In one or more embodiments, a rig may include 8 AC electric motors driving 8 right angle gearboxes built into the trunnions, driving 8 planetary gearboxes which are bolted to the rims thus driving the 8 rim and tire assemblies. One drive unit per tire may be provided and each drive unit may be controlled independently. Each of the 4 corners of the drilling module may have 2 of these drives, one per tire, two tires per corner, and 8 tires total. The 8 AC electric motors may be controlled from a Variable Frequency Drive (VFD) house. The controls may be remote and wireless for the driver. The driver may walk alongside the drilling module and control the speed and the steering remotely. There may be 4 trunnions on the system such as one in each corner. The rig may have a vertical hydraulic lift cylinder over each of the trunnions. The AC motors may have electrical cables attached to them such that power may be drawn from drilling rig power such as a generator set inside the drilling module. With the VFD house and the controls for these motors, the unit may be programmed with constant torque in each of the wheels in order to balance the load and speed of each of the wheels as they negotiate a corner. In addition, the electronics may be capable of custom programming such that the speed can be controlled in the moving system to match or approach the safe working speed of the tires in the moving system. This may allow the tires to run safely and avoid overheating from excessive speed. Data may also be collected from this style of moving system. The data may include maximum speed, time travelled, and current load used. The data may be transmitted back to the drilling contractors main office for purposes of analysis and crew monitoring, for example. The moving system may also be governed to a selected speed for tire safety and heat dissipation. 
     The steering mechanism may include a linkage type of geometry having a double ended cylinder for driving the linkage and the wheel assemblies. This double ended cylinder assembly may be mounted inside a box that is free to travel up and down on 4 guides that have springs, hydraulic cylinders, or other biasing mechanisms on the bottom of the system. Thus, each steering cylinder may be free to travel up and down within its respective wheel assembly as the driller&#39;s side and off-drillers side hydraulic cylinders move up or down to lift or lower the load in order to achieve the final ride height of the drilling module. The springs or hydraulic cylinders may prevent the unit from bottoming out on a bottom stopper. The top of the guides may be attached to the body of the drilling module. The amount of hydraulics used to power the moving system may be much smaller than previous systems because less hydraulic fluid at slower speeds may be used to power the steering cylinder, lift cylinder, and the locking or engagement pins as compared to the drive systems of known rigs. The oil for these cylinders may not get as hot as the hydraulic drive moving systems and the cylinders may use a lower oil pressure of 3000 psi to operate and may not require a large volume flow rate. 
     The front and back steering may be set and/or controlled such that both units may point to one single turn center at the minimum possible turning radius. This is the point where proper steering geometry may be set for the rig, thus reducing tire scrub. Depending on the hole pattern in the steering system, the tire set may turn approximately 22.5 degrees when the drilling module is travelling in a longitudinal direction. All perpendicular radials from each tire may point to the same turn center, thus, resulting in a smooth turn and minimal steer cylinder force needed to make the turn. 
     For travelling longitudinally along a row of wells, the tires may be rotated 90 degrees on the centerline of each hydraulic lift cylinder using the double ended steering cylinder. For example, and as described in more detail below, the end of the barrel of the lift cylinder has a series of holes for the steering arm link to be capable of locking into any of the desired holes in this setup of holes. Once the maximum stroke is obtained from the steering cylinder, small cylinders connected to pins may disengage the pins from these holes at the end of the barrel. Using a guide, the steering arm link can be repositioned using the steering cylinder. Then the small cylinders connected to pins may reengage these pins in order to lock steering arm link to a new position. Thus the pair of wheels in each corner may be rotated to any angle so desired, such as 90 for transverse movement or 0 degrees for longitudinal movement, or any angle in between. This acts as a ratchet mechanism, and once the steering is set where the steering bars are symmetrical between the driller&#39;s side and off-drillers side, the rig may be moved under its own power. Since the steering mechanism is reset to symmetrical before travel, there exists the possibility of small steering adjustments with the steering mechanism, +/−1 to 2 degrees, in order to correct the location of the drilling module as it moves. This slight steering adjustment angle features locked stoppers, because the limit of steer may be 1 to 2 degrees. This degree of adjustment is small enough to avoid tire scrub, due to the very large turning radius in play and the short travel distance involved on a row of wells on a pad. In addition, since the steering arm is adjustable in any radial direction on the barrel of the lift cylinder, a right hand and left hand lift cylinder is not required for steering. 
     The moving system may perform opposite steering between front and back moving systems, such as when navigating a corner. That is, the front wheels may be turned toward the right and the rear wheels may be turned toward the left to allow the vehicle to navigate a right turn. This may occur on long road moves, for example. However, the system may also be capable of all 8 tires being pointed in the same direction in an angle between 0 degrees longitudinal and 90 degrees transverse, such as 45 degrees but not limited to this angle. Thus the entire drilling module may crab over at this angle while maintaining its longitudinal and transverse position as it travels. Since the steering mechanism is reset to symmetrical before travel, there exists the possibility of small steering adjustments with the steering mechanism, ±/−1 to 2 degrees, in order to correct the location of the drilling module as it moves. This slight steering adjustment angle features locked stoppers, because the limit of steer would be 1 to 2 degrees. This is small enough to avoid undue tire scrub due to the very large turning radius in play. This may occur over short travel distances such as on a row of wells, for example. 
     The moving system may additionally perform opposite steeling between adjacent wheels or adjacent wheel pairs by providing for individual rotation of each wheel or wheel pair. That is, the pins for a first pair of wheels may be disengaged from the holes at the end of the barrel of the lift cylinder, so as to disengage the steering arm link, while the pins for a second, adjacent pair of wheels may be engaged in one or more corresponding holes so for that lift cylinder so as to engage the steering arm link for that wheel pair. The steering cylinder may then be used to rotate the first of the two adjacent wheels pairs, while not rotating the second wheel pair. Once a desired rotation is obtained for the first wheel pair, the pins may be disengaged from that wheel pair, and pins may engage for the second wheel pair so as to allow for rotation of the second wheel pair. Once both sets of wheels are arranged in a desired rotational position, the pins may be reengaged for both wheel pairs in order to lock the steering arm link to a position. Thus two front wheel pairs and/or two rear wheel pairs may each be independently rotated to any angles desired, such as 90 for transverse movement or 0 degrees for longitudinal movement, or any angle in between. 
     Movement between wells may be done at the 90 degree position. This may save the rig from driving off of the well patterns and then backing up again. The wheelbase of the drilling module may be long and even with proper steering geometry at 22.5 degrees the maneuverability of this unit may be limited. With the wheels turned 90 degrees the drilling module is free to move sideways. The moving system does not have any pieces of equipment that need removal before turning the wheels 90 degrees, such as the removal of the Akermann steering bar, or the reinstallation of a different steering bar once the wheels are at 90 degrees. The entire process of repositioning the wheels under the drilling module can be done remotely by the operator in a safe environment with no overhead lifting of any of the components, and no one getting in between the tires. 
     The moving system at each end of the rig may also include vertical play of up to 6″ on each side in order accommodate any lack of levelness between the driller side and off-drillers side lift cylinders. The 4 lift cylinders may all be symmetrical with the adjustable steering arm pinning system, thus ensuring interchangeability with each other for spare parts or cylinder swapping. 
     In some embodiments, the moving system described herein for moving a rig may be used to move a support complex such as a mud system, pipeshed, or other system or device. The system may also be scalable for small rigs rather than large rigs. In still other embodiments, the moving system may be useable for desert rigs or large loads in the Middle East rather than Arctic applications. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter that is regarded as forming the various embodiments of the present disclosure, it is believed that the invention will be better understood from the following description taken in conjunction with the accompanying Figures, in which: 
         FIG. 1  is a perspective view of a drill rig and supporting systems, according to one or more embodiments. 
         FIG. 2  is a close-up view of the rig of  FIG. 1  in isolation from the supporting systems, according to one or more embodiments. 
         FIG. 3  is a side view of the rig of  FIGS. 1 and 2 , according to one or more embodiments. 
         FIG. 4  is a perspective view of a wheelhouse portion of the rig of  FIG. 1 , according to one or more embodiments. 
         FIG. 5  is a perspective bottom view of the wheelhouse portion of  FIG. 4 , according to one or more embodiments. 
         FIG. 6  is a perspective bottom view of a pair of wheel assemblies of the wheelhouse of  FIG. 4 , according to one or more embodiments. 
         FIG. 7A  is a perspective rear/left view of a pair of wheel assemblies in a drilling or retracted position, according to one or more embodiments. 
         FIG. 7B  is a perspective front/left view of the pair of wheel assemblies of  FIG. 7A , according to one or more embodiments. 
         FIG. 7C  is a top view of the pair of wheel assemblies of  FIG. 7A , according to one or more embodiments. 
         FIG. 7D  is a right side view of the pair of wheel assemblies of  FIG. 7A , according to one or more embodiments. 
         FIG. 7E  is a front side view of the pair of wheel assemblies of  FIG. 7A , according to one or more embodiments. 
         FIG. 7F  is a left side view of the pair of wheel assemblies of  FIG. 7A , according to one or more embodiments. 
         FIG. 8A  is a perspective rear/left view of a pair of wheel assemblies in a driving or deployed position, according to one or more embodiments. 
         FIG. 8B  is a perspective front/left view of the pair of wheel assemblies of  FIG. 8A , according to one or more embodiments. 
         FIG. 8C  is a top view of the pair of wheel assemblies of  FIG. 8A , according to one or more embodiments. 
         FIG. 8D  is a right side view of the pair of wheel assemblies of  FIG. 8A , according to one or more embodiments. 
         FIG. 8E  is a front side view of the pair of wheel assemblies of  FIG. 8A , according to one or more embodiments. 
         FIG. 8F  is a left side view of the pair of wheel assemblies of  FIG. 8A , according to one or more embodiments. 
         FIG. 9A  is a perspective rear/left view of a pair of wheel assemblies in a driving or deployed position and turned 90 degrees, according to one or more embodiments. 
         FIG. 9B  is a perspective front/left view of the pair of wheel assemblies of  FIG. 9A , according to one or more embodiments. 
         FIG. 9C  is a top view of the pair of wheel assemblies of  FIG. 9A , according to one or more embodiments. 
         FIG. 9D  is a right side view of the pair of wheel assemblies of  FIG. 9A , according to one or more embodiments. 
         FIG. 9E  is a front side view of the pair of wheel assemblies of  FIG. 9A , according to one or more embodiments. 
         FIG. 9F  is a left side view of the pair of wheel assemblies of  FIG. 9A , according to one or more embodiments. 
         FIG. 10A  is a top view of a pair of wheel assemblies, according to one or more embodiments. 
         FIG. 10B  is a top view of the pair of wheel assemblies of  FIG. 10A  where the wheels are turned 22.5 degrees relative to the position of  FIG. 10A , according to one or more embodiments. 
         FIG. 10C  is a top view of the pair of wheel assemblies of  FIG. 10A  where the wheels are turned 22.5 degrees relative to the position of  FIG. 10B , according to one or more embodiments. 
         FIG. 10D  is a top view of the pair of wheel assemblies of  FIG. 10A  where the wheels are turned 22.5 degrees relative to the position of  FIG. 10C , according to one or more embodiments. 
         FIG. 10E  is a top view of the pair of wheel assemblies of  FIG. 10A  where the wheels are in the process of turning the remaining degrees for a 90 degree turn relative to the position of  FIG. 10A , according to one or more embodiments. 
         FIG. 10F  is a top view of the pair of wheel assemblies of  FIG. 10A  where the wheels are turned 22.5 degrees relative to the position of  FIG. 10D  and 90 degrees relative to the position of  FIG. 10A , according to one or more embodiments. 
         FIG. 11  is a perspective view of a pair of wheel assemblies according to one or more embodiments. 
         FIG. 12  is a perspective view of a pair of wheel assemblies according to one or more embodiments. 
         FIG. 13  is a perspective view of a pair of wheel assemblies according to one or more embodiments. 
         FIG. 14  is a perspective view of a pair of wheel assemblies according to one or more embodiments. 
         FIG. 15  is a perspective view of a pair of wheel assemblies according to one or more embodiments. 
         FIG. 16  is a perspective view of a pair of wheel assemblies according to one or more embodiments. 
         FIG. 17  is a top view of a pair of wheel assemblies according to one or more embodiments. 
         FIG. 18  is a rear view of a pair of wheel assemblies according to one or more embodiments. 
         FIG. 19  is a close-up view of a steering mechanism of a pair of wheel assemblies, according to one or more embodiments. 
         FIG. 20  is a perspective view of a pair of wheel assemblies according to one or more embodiments. 
         FIG. 21  shows a method of driving and/or steering a drill rig, according to one or more embodiments. 
         FIG. 22  is a top view of a pair of wheel assemblies, according to one or more embodiments. 
         FIG. 23  is a top view of two pairs of wheel assemblies of a drill rig, the wheel assemblies arranged in a rotational configuration for rotating the rig about a central axis, according to one or more embodiments. 
         FIG. 24A  is a top view of two pairs of wheel assemblies of a drill rig, according to one or more embodiments. 
         FIG. 24B  is a top view of the two pairs of wheel assemblies of the drill rig of  FIG. 24A , where the wheels are turned inward approximately 80.35 degrees relative to the position of  FIG. 24A , according to one or more embodiments. 
         FIG. 24C  is a top view of the two pairs of wheel assemblies of the drill rig of  FIG. 24A , where the drill rig is rotated about its central axis, according to one or more embodiments. 
         FIG. 25  shows a method of rotating a drill rig about a central axis, according to one or more embodiments. 
         FIG. 26  is a top view of a drill rig rotating about a central axis, according to one or more embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     The present application, in one or more embodiments, relates to a moving system for a drill rig. In particular, the moving system may be an electrically driven system having a steering mechanism providing for a high level of directional range of motion allowing for travel at 90 degrees relative to a primary direction, for example. The moving system may be operated completely automatically without the need for physical intervention or adjustment by operators making the system easier to use and safer to operate. The steering mechanism may be configured to accommodate various radii turns and may allow for coordinated steering between the front and rear mechanisms thereby avoiding tire scrub and further avoiding having tires walk off of rims or other dangerous conditions. The electrically driven system may provide an alternative to high pressure, high flow, hydraulic drive systems and thereby may reduce the risks of environmental effects associated with hydraulic failures and, in particular, hydraulic fluid leaks. The flexibility of the present drive system allows for a high level of rig moving versatility and positioning advantage. 
     With reference to  FIG. 1 , a drill rig assembly  100  is shown. The drill rig assembly  100  may include a drill rig portion  102  and various assemblies and systems  104  for supporting drilling operations. In particular, the assemblies and systems  104  may include a pipeshed, a mud tank module, a mud pump module, a power module, and a cutting module. Still other facilities and systems may be provided. In some embodiments, the drill rig  102  and supporting assemblies and systems  104  may be configured for arctic operations and, as such, may be partially or fully enclosed. In  FIG. 1 , the drill floor  106  and mast  108  of the drill rig  102  is shown in a cantilevered condition. That is, the drill rig  102  may include a cantilevering rail system  110  allowing the drill floor  106  and mast  108  to shift laterally relative to a supporting structure of the rig  102  such that drilling operations may be performed in an offset position relative to the supporting structure. 
       FIG. 2  shows the drill rig in isolation from the other supporting assemblies and systems. In  FIG. 2 , the rig  102  has been shifted back from its cantilevered condition and is being viewed from the rear of  FIG. 1 , for example. Of particular note with respect to the present application is the presence of a wheelhouse  112  on each of the front or cab end  114  and rear or well end  116  of the rig  102 . Each wheelhouse  112  may be configured to enclose a moving system  118 . In particular, the wheelhouse  112  may function to support the rig  102  during drilling operations and may provide for deployment of a moving system  118  allowing the rig  102  to be picked up and supported by the moving system  118  for purposes of transport between drilling locations. A side view of the drill rig  102  is shown in  FIG. 3  where it can be seen that a front cab  120  or drive location may be provided extending from the front  114  of the rig. It is to be appreciated that while an operator may drive the rig  102  from the front cab  120 , the automated nature of the system may also allow the operator to drive the rig  102  from outside the rig  102  such as, for example, while walking with the rig  102  and monitoring the position of the rig  102  relative to the travel path or roadway or monitoring the rig  102  relative to a drilling location or well center. In this embodiment, the operator may use a tablet or other mobile computing device such as an ipad or other computing device having a moving system interface. 
       FIG. 4  shows a wheelhouse  112  in isolation from the rig  102 . The wheelhouse  112  may be configured to support the rig  102  and enclose the moving system  118 , while allowing for deployment of the moving system  118  to move the rig  102 . The wheelhouse  112  may include a rig interface  122 , a cage or truss walls portion  124 , and a foot or bearing pad portion  126 . As shown, the moving system  118  may be arranged within the truss walls  124  and may have a deployed position where a bottom of the moving system  118  is below the bearing pad  126  and a retracted position where a bottom of the moving system  118  is at or above the bearing pad  126 . As such, when the moving system  118  is deployed, the rig  102  may be fully supported by the moving system  118  and the bearing pad  126  may be raised off of the ground. When the moving system  118  is retracted, the bearing pad  126  may be in contact with the ground to support the rig  102  during drilling operations. 
     As discussed, the bearing pad  126  of the wheelhouse  112  may be configured to support the rig  102  during drilling operations. The bearing pad  126  may extend around all or a portion of the wheelhouse  112 . In some embodiments, the bearing pad  126  may extend along each of two sides of the wheelhouse  112  or it may extend along each of four sides. The bearing pad  126  may be attached to a bottom of the truss walls  124  and may be configured to receive rig loads from the truss walls  124  and transfer rig loads to the ground. The bearing pad  126  may include a relatively flat ground-contacting surface configured for distributing loads to the surface of the ground. The bearing pad  126  may be relatively plate like and may have a tapered shape where the pad is thinner near its outer edges and thicker near its inner portion so as to accommodate shear and bending forces resulting from rig loads. In some embodiments, the tapered shape may be provided in the form of stiffeners arranged on a relatively flat constant thickness plate rather than varying the thickness of the plate. In some embodiments, a combination of both may be provided. The bearing pad  126  may be pivotally connected to the truss walls  124  to accommodate unevenness in the ground or the bearing pad  126  may be more rigidly connected as shown. 
     The truss walls  124  may extend upwardly from the bearing pad  126  to form a surrounding structure to house the moving system  118 . The truss walls  124  may include a plurality of upright support elements and a series of diagonal and/or cross braces. In some embodiments, the series of diagonal and/or cross braces may be removable so as to allow access to the moving system  118  and allow for maintenance and/or repair. For example, one or more diagonal and/or cross braces may be removed to allow for tire changing or repair. 
     With reference to  FIGS. 5 and 6 , the rig interface  122  of the wheelhouse  118  may include a relatively flat roof-like structure supported by the truss walls  124  and extending across the top of the moving system  118 . The rig interface  122  may be structurally designed to receive rig loads and transfer them to the supporting structure. In some conditions of use, the supporting structure may include the truss walls  124  of the wheelhouse  112  when the moving system  118 , for example, is not deployed. In other conditions of use, the supporting structure may include the moving system  118  when, for example, the moving system  118  is deployed. The rig interface  122  may include a series of cross members extending across the wheelhouse  112  and above the moving system  118  from one side of the truss walls  124  to an opposing side, for example. The rig interface  122  may include one or more cover plates or surfaces above and/or below the cross members. In one or more embodiments, the rig interface may include a deployment point or points  128  and a steering control point  130 . The deployment point or points  128  may include locations where jacking cylinders may engage the rig interface  122  to deploy the moving system. In one or more embodiments the cross members may be arranged to extend across the wheelhouse  112  so as to pass above the deployment point  128  and, as such, allow for connection of the jacking cylinder to the cross member. In some embodiments, the cross members may drop near the deployment point  128  so as to increase the strength of the cross members and accommodate the high loads imparted when the moving system  118  is deployed. The steering control point  130  may include a location of attachment for a steering mechanism and may provide a reference point for lateral shifting and/or movement used in steering the moving system  118 . 
     As mentioned, the moving system  118  may be housed within the above-described wheelhouse  112 . The moving system  118  may be configured for deployment from the wheelhouse  112  and retraction within the wheelhouse  112 . The moving system  118  may also be configured to move the rig  102  in a selected direction and may further allow for steering the rig  102  while moving and/or otherwise adjusting the direction of travel of the rig  102  before beginning travel in that particular direction. The moving system  118  may include a pair of same or similar wheel assemblies  132  arranged substantially adjacent to one another within the wheelhouse  112 . In some embodiments, more or fewer wheel assemblies  132  may be provided. The moving system  118  may also include a steering system  134  for steering the wheel assemblies  132  relative to the rig  102  and allowing the direction of travel to be controlled. 
     The wheel assemblies  132  may be configured for rolling engagement with the ground to allow the rig  102  to move and may also be configured for rotation about a substantially vertical axis  136  to accommodate steering of the rig  102 . In one or more embodiments, the wheel assemblies  132  may each include a central core element  138 , an outer wheel system  140  arranged to an outer side of the central core element  138  and an inner wheel system  142  arranged to an inner side of the central core element  138 . The wheel assemblies  132  may also each include a jacking element  144  arranged between outer and inner wheel systems and between the core element  138  and the rig interface  122 . 
     With reference now to FIG. sets  7 A- 7 F,  8 A- 8 F, and  9 A- 9 F, each of the outer wheel system  140  and inner wheel system  142  may each include a wheel  146  offset from the central core portion  138  and an electric drive motor  148  arranged on the central core portion  138 . The wheels  146  may be arranged adjacent to the central core portion  138  to form a pair of wheels. The electric drive motors  148  may be configured to impart rotational force to their respective wheels  146  to drive the rig  102 . The electric drive motors  148  may be arranged vertically between the inner and outer wheels of each wheel assembly  132  and may include a vertically extending drive shaft. The drive shaft may extend downwardly into the central core  138  portion. The central core portion  138  may include a right angle gear box. The gear box may be connected to a planetary gear system that may be provided to drive a respective wheel arranged in a substantially vertical plane. The wheels  146  may be supported relative to the central core portion  138  by the planetary system, which may be bolted to a substantially horizontally extending trunnion axle supported off of the central core  138  portion by a pin. The trunnion axle may allow the pair of wheels  146  to function together and accommodate uneven surfaces where the trunnion axle may be able to rotate about a longitudinal substantially horizontal axis defined by its supporting pin. 
     A jacking or deployment system  144  may be arranged on the central core portion  138  between the inner and outer wheel and may extend upwardly from the central core portion  138  to engage the rig interface portion  122  of the wheelhouse  112 . The jacking or deployment system  144  may be configured to extend a respective wheel assembly  132  away from the rig interface  122  beyond the foot  126  of the wheelhouse  112  thereby deploying the wheel assembly  132  for use. The jacking or deployment system  144  may include a hydraulic cylinder system. The hydraulic cylinder may be arranged such that the base or cap of the cylinder is secured to the central core portion  138  and rod portion extends upwardly therefrom to the rig interface  122 . The rod portion may include a flange plate and may be secured to rig interface  122  at a deployment point  128 . As the cylinder is actuated, the rod portion may extend out of the barrel thereby elongating the cylinder and driving the central core portion  138  away from the rig interface  122 . 
     The jacking or deployment system  144  may be a non-keyed cylinder such that the rod is free to rotate relative to the barrel, for example. As will be explained in more detail below, the steering system  134  may engage the barrel portion of the jacking or deployment system  144  so as to rotate the barrel relative to the rod and, thus, rotate the wheel assemblies  132 . As part of the engagement of the steering system  134 , the cylinder head of the jacking system  144  may include a plate or a series  150  of plates to be engaged by the steering system  134 . 
     In one or more embodiments, the plate or series of plates  150  may include a sandwich plate including a pair of plates spaced apart from one another and configured to receive a portion of the steering mechanism therebetween. The pair of plates  150  may be generally or substantially annular in shape allowing the rod and/or the barrel of the jacking cylinder  144  to pass therethrough. The pair of plates  150  may be rigidly secured to the barrel of the jacking cylinder  144  such that rotational forces applied to the pair of plates  150  may impart rotational motion on the wheel assembly  132  relative to the jacking rod  144  and the rig  102 . In some embodiments, the pair of plates  150  may be directly secured to the barrel of the jacking cylinder  144 . In other embodiments, the separation of the pair of plates  150  may be created by a bushing or collar arranged on and secured to the barrel of the cylinder and the plates  150  may be secured thereto. In either case, the cylindrical element extending between the pair of plates  150  may define a neck having a substantially circular shape and having an outer diameter. In some embodiments, the plates  150  may be arrange one above the other and the space between the plates may be sufficient to receive a jaw plate of the steering system as described in more detail below. 
     The pair of plates  150  may include a series of holes or apertures  152  for receiving an engagement pin  154 . The plates  150  may be arranged in spaced apart position and the holes  152  in one plate may be aligned with holes  152  in the other plate  150 . The holes  152  in the pair of plates  150  may be arranged to accommodate particular angular motions or rotations of the wheel assembly  132 . In some embodiments, the holes  152  may be arranged in an annular array or row along a circular centerline of the annular plate. In some embodiments, the holes  152  may be in multiple rows and may be staggered from one row to another row. Still other arrangements of holes  152  may be provided. In some embodiments the holes  152  in a particular row may be spaced from one another such that adjacent holes are approximately 10 degrees, 22.5 degrees, 30 degrees, 45 degrees, 90 degrees, or other angles apart from one another. Still other angular spacings may be provided. 
     In some embodiments, the wheels may be sized to accommodate a 1000 ton rig. Where eight wheels are provided, each wheel may be configured to support 250,000 pounds. In some embodiments, the tires may be 40×57, for example, and may include a tire pressure of approximately 120 psi. Other tires sizes may be used. 
     Having discussed the wheel assemblies  132  in great detail, it is noted that adjacent wheel assemblies  132  may be spaced from one another sufficiently to allow for full rotation or at least 90 degrees of rotation. The wheel assemblies  132  may, thus, be spaced from one another a distance equal to one wheel diameter and, in some embodiments, 1¼ or 1½ wheel diameters. The wheelhouse  112  may be sized accordingly, and may also provide sufficient clearance around the wheel assemblies  132  to allow for full rotation or at least 90 degrees of rotation of the wheel assemblies  132 . 
     With reference to  FIGS. 10A-10F , the moving system  118  may include a steering system  134  configured for controlling the planetary orientation of the wheel assemblies  132  and, as such, the travel direction of rig. The steering system  134  may include a control device  156 , a linkage assembly  158 , and a wheel assembly engaging portion  160 . The steeling system  134  may be connected to the rig interface  122  portion of the wheelhouse  112  and, as such, may forcibly impart rotational motion of the wheel assemblies  132  relative to the rig  102 . 
     The control device  156  may be configured for actuating motion of the wheel assemblies  132  and may be further configured to do so in the deployed and/or retracted position. The control  156  device may, thus, include an actuating portion  162  for actuating steering motions and a guide system  164  allowing the control device  156  to track and/or follow the deployment and retraction of the wheel assemblies  132 . The control device  156  may be positioned between the one or more wheel assemblies  132  and may be configured to simultaneously control the orientation of the wheel assemblies  132  such that a change in orientation of one wheel assembly  132  is correspondingly changed in the other wheel assembly  132 . 
     The guide system  164  of the control device  156  may include one or a series of guides such as guide rods  165  secured to the steering control point  130  and extending downwardly from the steering control point  130 . The guide system  164  may include a housing  166  arranged on the guide rods  165  and configured for sleevably travelling up and down along the length of the guide rods  165 . The guide rods  165  may include one or more biasing elements  168  arranged thereon and configured for biasing the housing  166  in an upward position. In some embodiments, the biasing elements  168  may include springs concentrically arranged on the guide rods  165  and biased between a guide rod flange and the housing  166 . In other embodiments, the biasing elements  168  may be hydraulic cylinders that may be actuated to control the position of the control device. In other embodiments, the control device may be free floating using counter-weights and pulleys, instead of cylinders or springs. In this embodiment, it may function as a weightless component within the suspension, as the suspension system moves over uneven terrain. In the case of biasing elements, such as springs, the biasing elements  168  may be relatively stiff, but may have a stiffness that is overcome when the wheel assemblies are moved to a deployed position. The length of the guide assemblies may be such that the control system  156  may move a distance away from the rig interface  122  that is substantially the same as the deployment distance of the wheel assemblies  132 . That is, a stroke length of the housing  166  along the guide system  164  may be the same or similar to the stroke length of the jacking or deployment cylinder  144  of the wheel assembly  132  such that the control system  156  may move together with the deployment of the wheel assemblies  132 . 
     The actuating portion  162  of the control device  156  may include a laterally moving mechanism that may push on one wheel assembly  132  while pulling on another wheel assembly  132 . The actuating portion  162  may be offset rearward or forward from a laterally extending centerline of the wheel assemblies  132  and by pushing/pulling on the wheel assemblies (i.e., from side to side in  FIG. 10A ), the actuating portion  162  may create a torsional or torque force on the wheel assemblies  132  causing them to rotate. By virtue of being positioned between the assemblies  132 , the push/pull of the actuating portion  162  may cause each wheel assembly to rotate in the same direction. (i.e., clockwise or counter clockwise in  FIG. 10A ). 
     The actuating portion  162  may include a double-ended cylinder. The double-ended cylinder may include a barrel having a rod extending from each end where extension of a rod out one side of the barrel may simultaneously cause retraction of a rod into the other side of the barrel. In some embodiments, the actuating portion may include a rack and pinion driven by an electric or hydraulic motor, for example. In the case of the double-ended cylinder, the amount of extension of the rod out of or into the barrel may provide for a partial rotation of a wheel assembly  132 . For example, the extension of the rod out of or into the barrel may create rotation of a wheel assembly  132  less than the full available rotation of the wheel assembly  132 . Further rotation of the wheel assembly may be provided for by disengaging the actuation portion  162  from the wheel assembly  132 , retracting the rod (or extending the rod as the case may be), reengaging the actuation portion  162  with the wheel assembly  132  and further rotating the wheel assembly  132 . Accordingly, the stroke of the cylinder may be less than that which may be used to induce a larger rotation, for example. 
     A linkage assembly  158  may extend from each end of the actuating portion  162  and may be configured to transfer the lateral force and motion from the actuating portion  162  to the wheel assembly engaging portion  160  while accommodating the rotation of the engaging portion  160 . The linkage assembly  158  may include a laterally extending bar  170  having a first jaw connection at the rod of the actuating portion  162  and a second jaw connection at the wheel assembly engaging portion  160 . In some embodiments, the bar  170  may be a solid bar or a hollow bar, such as a pipe or tube. The bar  170  may be pivotally connected to the rod with a pin or other pivotal connection and may similarly be connected to the wheel assembly engaging portion with a pin or other pivotal connection. 
     The wheel assembly engaging portion  160  may engage the wheel assembly  132  and transfer forces from the actuation portion  162  to induce rotational motion of the wheel assembly  132 . The engaging portion  160  may be configured for selectively engaging the wheel assembly allowing for a ratcheting, stepping, or incremental approach to rotating the wheel assembly  132 . The engaging portion  160  may include a jaw plate  172  configured for selective engagement with the jacking or deployment cylinder  144 . In particular, the jaw plate  172  may be configured for engagement with the jacking or deployment cylinder  144  at or near the cylinder head of the barrel of the jacking cylinder  144 . As such, the engaging portion  160  may be configured to cause the barrel portion of the jacking cylinder  144  to rotate relative to the rod portion thereof thereby causing the wheel assembly  132  to rotate. 
     The jaw plate  172  may extend from the linkage assembly  158  and may be configured to engage the sandwich plates  150  arranged at or near the cylinder head of the jacking cylinder  144 . The jaw plate  172  may be substantially planar so as to slidably engage the pair of plates  150  and allow for relative rotation of the jaw plate  172  between the pair of plates  150 . When viewed from above, the jaw plate  172  may define a jaw or an inner radiused surface  173  configured for abuttingly engaging the neck extending between the pair of plates  150 . The inner radiused surface  173  may extend around the neck to a point just past the half-way point and may then divert from its path along the neck outwardly. The engaging portion  160  may also include a closure plate  174  extending across the open end of the jaw plate  172  on an opposing side of the neck. The closure plate  174  may include an inner radiused surface  175  configured for abuttingly engaging the neck. Accordingly, the jaw plate  172  and the closure plate  174 , together, may extend the full circumference of the neck area between the pair of plates  150 . The closure plate  174  may be pinned bolted or otherwise secured to the jaw plate  172  on each side and may be removable as required for removal of the steering mechanism  134  from the wheel assembly  132 . 
     The jaw plate  172  may include a pair of engagement holes  176  configured for engagement by the engagement or locking pins  154 . The engagement holes  176  may be arranged on either side of the neck at or near opposite sides of the neck. In some embodiments, as shown, the engagement holes  176  may be arranged 180 degrees from one another and along a centerline extending through the holes  176  and through the center of the jacking cylinder  144 . The engagement holes may be arranged along a circle having a radius that is the same or similar to the radius of the row or rows of holes  152  in the pair of plates  150 . As such, the engagement holes  176  may be configured to align with a corresponding pair of holes  152  in the pair of plates  150 . 
     The engagement or locking pins  154  may be arranged in the pair of holes  176  of the jaw plate  172  and in the holes  152  in the pair of plates  150 . That is, each pin  154  may extend upwardly through a lower plate of the pair of plates  150 , through the jaw plate  172 , and through an upper plate of the pair of plates  150 . As shown, an engagement pin  154  may be provided corresponding to each of the engagement holes  176  and, as such, the jaw  172  plate may be configured for rotational engagement with the pair of plates  150  via the engagement pins  154 . 
     The engagement pins  154  may be actuatable pins such that the jaw plate  172  may selectively engage the pair of plates  150  and selectively impart rotational motion in the pair of plates  152  and, thus, the corresponding wheel assembly  132 . The engagement pins  154  may include a hydraulic cylinder  178  that may be controlled to engage and disengage the pins  154  from the holes  152  in the pair of plates  150  and the jaw plate  172 . By way of controlling the hydraulic cylinder  178  the pins  154  may be selectively engaged or disengaged from the holes  150 / 176 . In some embodiments, the hydraulic cylinder  178  may be actuatable only in conditions of rotation that allow for hole alignment. For example, upon disengaging the pins  154 , the pins  154  may not be actuatable unless/until a rotation substantially equal to the radial position of the holes  152  in the pair of plates  150  is turned by the jaw plate  172 . In other embodiments, no limitation on the timing of the hydraulic cylinder  178  may be included. 
     In some embodiments, the engagement pins  154  may be integral to steering operations and may allow for a ratcheting, stepping, and/or incremental steering operation. That is, with the engagement pin  154  in place, the actuating portion  162  of the steering system  134  may shift laterally to impart rotation in the wheel assemblies  132 . Once the actuating portion  156  has passed through a selected stroke length, the actuating portion  162  may stop, the engagement pin  154  may be disengaged from the jaw plate  172  and the pair of plates  150  and the actuating portion  162  may return to its position before the selected stroke length. The engagement pin  154  may be reengaged with the jaw plate  172  and the pair of plates  150  and the process may be repeated to further rotate the wheel assembly  132 . Depending on the stroke length of the actuating portion  156  and the radial spacing between the holes  152  in the plates  150 , the steering or wheel assembly rotation may be performed in resulting increments. Still further, the wheel assemblies  132  may be capable of rotation that is not limited by the stroke length of the actuating portion  162  or by other features. In some embodiments, the wheel assemblies  132  may be rotated up to 90 degrees, up to 180 degrees, up to 270 degrees, or up to 360 degrees. 
     With continued reference to  FIGS. 10A-10F  and  FIG. 21 , a method may be described for rotating one or more wheel assemblies  132 . As shown in  FIG. 10A , the wheel assemblies  132  may be positioned in a substantially longitudinal direction. In some cases, particularly when it is desirable to move a rig  102  along a series of wells, an operator may wish turn the wheel assemblies 90 degrees with or, more likely, without moving the rig  102 . By comparing  FIGS. 10A and 10B , it is apparent that both wheel assemblies  132  in  FIG. 10B  have rotated approximately 22.5 degrees about the jacking/deployment cylinder  144  relative to that shown in  FIG. 10A . The underlying method to arrive at the condition of  FIG. 10B  may include disengaging the engagement pins  154  of the wheel assembly engagement system  160  from each pair of plates  150  and jaw plate  172 , allowing the plate systems to rotate freely relative to one another without rotating the wheels  132 . The actuating portion  162  of the control device  156  may then be activated by shifting it to the left from its position in  FIG. 1.0A , thereby extending the hydraulic rod out of the left of the barrel and retracting the hydraulic rod into the right of the barrel. The particular amount of shift may be sufficient to rotate each plate system approximately 22.5 degrees. At that point, the engagement pins  154  of the wheel assembly engagement system  160  may be reengaged with the pair of plates  150  and the jaw plate  172 . The actuating portion  162  may then be shifted back to the right thereby retracting the left rod and extending the tight rod and returning the position of the jaw plate back  172  to its position of  FIG. 10A  so as to rotate the wheel assemblies  132  approximately 22.5 degrees. By comparing the wheel assemblies  132  of  FIG. 10B  to those of  FIG. 10C , it is apparent that the wheel assemblies  132  of  FIG. 10C  have rotated yet another 22.5 degrees relative to the position of the wheel assemblies  132  of  FIG. 10B . The process for creating this rotation and having the control device  156  return to the position shown in  FIG. 10C  may be the same or similar to that described for the transition between  FIGS. 10A and 10B . The process may again be repeated to create the condition shown in  FIG. 10D  and the process may be repeated again to create the condition shown in  FIG. 10F .  FIG. 10E  shows an intermediate position between the positions of  FIGS. 10D and 10F  and shows the actuating portion  162  shifted to the left as described above. 
     It is to be appreciated that, alternatively, the transitions illustrated between each of  FIGS. 10A through 10F  may be achieved by actuating the actuating portion  162  before disengaging the engagement pins  154  for each rotation of the wheels  132 . For example, the method to transition from the position show in  FIG. 10A  to the position shown in  FIG. 10B  may include first actuating the actuating portion  162  by shifting it to the right from its position of  FIG. 10A  so as to rotate the wheel assemblies  132 , disengaging the engagement pins  154  from the plates  150  and jaw plate  172 , shifting the actuating portion  162  back to the left so as to return the position of the jaw plate back  172  to its position of  FIG. 10A  without rotating the wheels  132 , and reengaging the engagement pins  154 . 
     In one or more embodiments a method  200  of operating a drive system of a rig may include deploying a wheel assembly from a drill rig. ( 202 ) The method  200  may also include activating the actuating port of the control device by shifting it to the left or right from its position in  FIG. 10A  to rotate a wheel assembly. ( 204 ) For purposes of allowing for further rotation, the method may also include disengaging the pins of the wheel assembly engagement system from the pair of plates and the jaw plate ( 206 ), shifting the actuating portion back to the tight or left (opposite the initial direction) back to its position of  FIG. 10A  without rotating a wheel assembly ( 208 ), and reengaging the locking or engagement pins into the pair of plates and the jaw plate ( 210 ). The method may also include repeating or reversing these steps to further rotate the wheel assembly or reverse the direction of rotation. ( 212 ) The method may also include actuating an electric drive motor to drive a wheel of the wheel assembly. ( 214 ) In one or more embodiments, the method may also include coordinating drive speeds of one or more wheel assemblies ( 216 ) and/or coordinating wheel torques of one or more wheel assemblies ( 218 ). It is to be appreciated that the method steps included herein may be performed in one of several available orders and the order is not to limited to the order shown in  FIG. 21 . 
       FIGS. 11-20  show additional perspective views of pairs of wheel assemblies according to embodiments of the present application. 
     In some embodiments, wheel assemblies of the present disclosure may provide for rotation of a drill rig about a central axis of the rig so as to change direction without, or substantially without, changing location of the rig. The wheel assemblies may be generally rotated inward, such that a pair of wheel assemblies controlled by a same steering system are rotated in opposing directions. In some embodiments, this may be accomplished by separately rotating the wheel assemblies. Turning now to  FIG. 22 , a pair of wheel assemblies  332  coupled to a steering system  334  is shown in a position configured for rotating a drill rig. As shown, each wheel assembly may have an inner wheel  342  and an outer wheel  340  rotated inward toward a center of the rig. In some embodiments, each wheel assembly  332  may be rotated approximately 80.35 degrees in some embodiments. In other embodiments, the wheels assemblies  332  may be rotated to a different degree of rotation so as to be configured about a central axis of the rig. Generally, the degree of rotation may relate, at least in part, to a distance between wheel assemblies  332 . By rotating each of the wheel assemblies  332  inward in this way, the rig may be capable of turning about itself at a central axis so as to change direction. For example,  FIG. 23  shows four wheel assemblies  332  of a drill rig coupled to two steering systems  334 . The wheel assemblies  332  of  FIG. 23  are shown in a position configured for rotating the drill rig about a central axis  333 . 
     As shown in  FIG. 22 , the steering system  334  may include a control device  356  for actuating motion of the wheel assemblies  332 , a pair of linkage assemblies  358  extending from the control device toward each of the wheel assemblies, and wheel assembly engaging portion  360  coupled to each wheel assembly. Each wheel assembly engaging portion  360  may have jaw plate  372  configured to engage one or more sandwich plates  350 , as described above. Moreover, a pair of actuatable engagement pins  354  may be configured to engage the jaw plate  372  and/or sandwich plates  350 . To achieve a desired angle of rotation of the wheel assemblies  332  so as to angle the wheels about a central axis of the rig, in some embodiments, the wheel assembly engaging portion  360  may have a locking pin  355 . The locking pin  355  may operate similar to engagement pins  354 , but may be arranged at an angle different than that of engagement pins  354 . That is, for example, the locking pin  355  may be arranged at an angle of approximately 12.85 degrees from a nearby engagement hole of the jaw plate  372 . In this way, the locking pin  355  may provide for an alternate degree of rotation than that provided by the engagement pins  354  (i.e. a degree of rotation in an increment not based on evenly spaced holes in the sandwich plates  350 .) The position of the locking pin  355  may be selected so as to provide a degree of rotation that accommodates the wheel assembly  332  position. That is, the wheel assembly  332  position may define a diameter with a degree of curvature which, in turn, may define the degree of rotation of the wheel assemblies  332 . When the locking pin  355  is actuated to engage an engagement hole in the jaw plate  372  and/or sandwich plates  350 , the engagement pins  354  may be disengaged, and vice versa. 
     With reference to  FIGS. 24A-24C and 25 , a method may be described for rotating one or more wheel assemblies  332  to a rig rotation position. As shown in  FIG. 24A , the wheel assemblies  332  may be positioned in a substantially longitudinal direction. In some cases, particularly when the rig approaches a tight corner as shown in  FIG. 24A , an operator may wish to rotate the rig about a central axis  333  of the rig in order to alter direction of travel. By comparing  FIGS. 24A and 24B , it is apparent that all four wheel assemblies  332  in  FIG. 24B  have rotated inward at approximately 80.35 degrees about the jacking/deployment cylinders relative to that shown in  FIG. 24A . In other embodiments, the four wheel assemblies  332  may be rotated inward at any other suitable degree of rotation about the jacking/deployment cylinders. The underlying method to arrive at the condition of  FIG. 24B  may include separately rotating each wheel assembly  332  by actuating the steering systems  334 . That is, for a pair of wheel assemblies  332 , the engagement pins  354  and/or locking pin  355  may be disengaged from one or both wheel assemblies. The steering system  334  may then be actuated to rotate one of the wheel assemblies by shifting the actuating portion  362  to the left or right (as needed to bring the wheel assembly  332  inward) and engaging the engagement pins  354  and/or locking pin  355  in the sandwich plates  350  and jaw plate  372 . The engagement pins  354  and/or locking pin  355  may then be disengaged from the rotated wheel assembly  332  and may operate with the actuating portion  362  to rotate the second wheel assembly of the pair of wheel assemblies. As shown in  FIG. 24C , once each wheel assembly  332  has been rotated, the an electric drive motor may be actuated to drive the wheel assemblies so as to rotate the drill rig about a central axis. 
     In one or more embodiments a method  400  of operating a drive system of a rig may include deploying a pair of wheel assemblies from a drill rig. ( 402 ) The method  400  may also include disengaging the pins of the wheel assembly engagement from the pair of plates and jaw plate for at least one wheel assembly of the pair of wheels assemblies. ( 404 ) The method may include activating the actuating portion of the control device by shifting it to the left or right to rotate a first wheel assembly without rotating a second wheel assembly. ( 406 ) The method may include disengaging the engagement pins and/or locking pin from the first wheel assembly once the first wheel assembly is rotated to desired degree of rotation. ( 408 ) In some embodiments, only the locking pin may be used to engage the sandwich plates and jaw plate to rotate a wheel assembly. In other embodiments, the engagement pins may be engaged first for one or more rotations, followed by engagement of the locking pin for one or more rotations to achieve a final desired degree of rotation. In this way, the rotation of a wheel assembly may be an iterative process involving the engagement pins and/or the locking pin. Once the desired degree of rotation is achieved in the first wheel assembly and the pins are disengaged from the first wheel assembly, the engagement pins and/or locking pin may engage the second wheel assembly ( 410 ), and the actuating portion may be activated by shifting it to the left or right to rotate the second wheel assembly. ( 412 ) Once the second wheel assembly is rotated to a desired degree of rotation, the engagement pins and/or locking pin may be reengaged with the first and/or second wheel assemblies. ( 414 ) Once again, an iterative process of multiple rotations using the engagement pins and/or the locking pin may be used to achieve the desired degree of rotation. The method may also include repeating or reversing these steps to further rotate the wheel assembly or reverse the direction of rotation. ( 416 ) The method may also include actuating an electric drive motor to drive one or more wheels of the wheel assemblies. ( 418 ) in one or more embodiments, the method may also include coordinating drive speeds of one or more wheel assemblies ( 420 ) and/or coordinating wheel torques of one or more wheel assemblies ( 422 ). It is to be appreciated that the method steps included herein may be performed in one of several available orders and the order is not to be limited to the order shown in  FIG. 25 . 
     The systems and methods described with respect to  FIGS. 22-25  provide improvements over conventional drill rig steering systems. These systems and methods allow a rig to be rotated about a central axis in order to negotiate relatively sharp turns or corners and generally without the need for excessive repositioning of the rig. That is, under conventional steering systems, such as a rack-and-pinion-type steering system, changing direction of a drill rig may generally require either a large turning radius or a relatively large number of forward and backward movements. In contrast, methods and systems of the present disclosure may allow a drill rig to rotate about itself, without the need for a large turning radius and without the need for excessive forward and backward movements of the rig. By the use of pins and selectable engagement holes at each wheel, wheel assemblies of the present disclosure may be individually rotated, such that two wheels coupled to the same actuating device may be turned in opposing directions, thus allowing for rotation of the entire rig. This is a great improvement over conventional rig steering systems. 
       FIG. 26  illustrates a drill rig  500  having two pairs of wheel assemblies  532  in a rotational configuration such that the drill rig may rotate about a central axis to change direction of travel. 
     As used herein, the terms “substantially” or “generally” refer to the complete or nearly complete extent or degree of an action, characteristic, property, state, structure, item, or result. For example, an object that is “substantially” or “generally” enclosed would mean that the object is either completely enclosed or nearly completely enclosed. The exact allowable degree of deviation from absolute completeness may in some cases depend on the specific context. However, generally speaking, the nearness of completion will be so as to have generally the same overall result as if absolute and total completion were obtained. The use of “substantially” or “generally” is equally applicable when used in a negative connotation to refer to the complete or near complete lack of an action, characteristic, property, state, structure, item, or result. For example, an element, combination, embodiment, or composition that is “substantially free of” or “generally free of” an ingredient or element may still actually contain such item as long as there is generally no measurable effect thereof. 
     In the foregoing description various embodiments of the present disclosure have been presented for the purpose of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise form disclosed. Obvious modifications or variations are possible in light of the above teachings. The various embodiments were chosen and described to provide the best illustration of the principals of the disclosure and their practical application, and to enable one of ordinary skill in the art to utilize the various embodiments with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the present disclosure as determined by the appended claims when interpreted in accordance with the breadth they are fairly, legally, and equitably entitled.