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CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of provisional patent application Ser. No. 61/624,273 filed on Apr. 14, 2012. 
    
    
     FIELD OF THE INVENTION 
     The subject invention generally pertains to workover vehicles for servicing well bores and more specifically to a method for removing well strings. 
     BACKGROUND 
     Drilling rigs are used for drilling new wells, and workover units typically are for servicing or repairing completed wells. Drilling rigs usually comprise a broad range of equipment that is assembled and set up in a modular manner at a well site. Workover units, on the other hand, comprise a generally self-contained vehicle carrying various components. After traveling to a well site, the workover vehicle is reconfigured for use. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of a workover vehicle at a well site according to some example embodiments of the invention. 
         FIG. 2  a front end view of the vehicle of  FIG. 1 , but with the mast lowered. 
         FIG. 3  is a back end view of the vehicle of  FIG. 1 , but with the mast lowered and the robot jib in its transport position. 
         FIG. 4  is similar to  FIG. 2  but showing the mast raised. 
         FIG. 5  is similar to  FIG. 3  but showing the mast raised and the robotic jib partially deployed. 
         FIG. 6  is similar to  FIG. 5  but showing the mast further deployed. 
         FIG. 7  is a back view of  FIG. 4 . 
         FIG. 8  is a perspective view of the workover vehicle in the process of being aligned to the wellbore. 
         FIG. 9  is similar to  FIG. 8  but showing the mast raised and proximate a pump jack with a walking beam. 
         FIG. 10  is a side view showing the mast and hydraulic tank lowered to a transport position. 
         FIG. 11  shows the mast and hydraulic tank raised. 
         FIG. 12  is a top view with the mast raised, robotic jib deployed and a rod storage rack extended to an operative configuration. 
         FIG. 13  is a top view with the mast down, and both the rod storage rack in its transport configuration. 
         FIG. 14  is a duplicate of  FIG. 12 . 
         FIG. 15  is similar to  FIG. 14  but showing the robotic jib in its transport configuration. 
         FIG. 16  is similar to  FIG. 12  but showing the robotic jib further deployed. 
         FIG. 17  is a front view of the upper trolley mechanism about to engage the upper end of a well rod. 
         FIG. 18  is a bottom view of  FIG. 17 . 
         FIG. 19  is a back view of  FIG. 17 . 
         FIG. 20  is a perspective view of the upper trolley mechanism. 
         FIG. 21  is a side view of  FIG. 17 . 
         FIG. 22  is a back view showing the upper trolley mechanism guiding the upper end of a well tube. 
         FIG. 23  is a bottom view of  FIG. 22 . 
         FIG. 24  is a front view of  FIG. 22 . 
         FIG. 25  is a perspective view of  FIG. 22 . 
         FIG. 26  is a side view of  FIG. 22 . 
         FIGS. 27-33  pertain to the upper robot  90 . 
         FIG. 27  is a perspective view of the articulated arm portion of the upper robot, wherein the arm portion is shown extended. 
         FIG. 28  is a side view of  FIG. 27 . 
         FIG. 29  is a bottom view of  FIG. 27 . 
         FIG. 30  is a back view of  FIG. 27 . 
         FIG. 31  is a perspective view similar to  FIG. 27  but showing the arm portion of the upper robot retracted. 
         FIG. 32  is a side view of  FIG. 31 . 
         FIG. 33  is a top view of  FIG. 31 . 
         FIGS. 34-45  pertain to the lower robot  36 . 
         FIG. 34  is a front view of the articulated arm portion of the lower robot, wherein the arm portion is extended. The end effectors of the upper and lower robots  90  and  36  are controlled to travel horizontally generally in unison. 
         FIG. 35  is a bottom view of  FIG. 34 . 
         FIG. 36  is a back view of  FIG. 34 . 
         FIG. 37  is a perspective view of  FIG. 34 . 
         FIG. 38  is a side view of  FIG. 34 . 
         FIG. 39  is a top view of  FIG. 34 . 
         FIG. 40  is a front view similar to  FIG. 34  but showing the arm portion of the lower robot retracted. 
         FIG. 41  is a top view of  FIG. 40 , which is similar to  FIG. 39  but with the arm portion of the lower robot retracted. 
         FIG. 42  is a back view of  FIG. 40 . 
         FIG. 43  is a perspective view of the articulated arm portion of the lower robot. 
         FIG. 44  is a side view of  FIG. 43 . 
         FIG. 45  is a bottom view of  FIG. 43 . 
         FIGS. 46-49  show various views of an end effector  92  of the upper robot  90 . 
         FIGS. 50-54  show various views of an end effector  96  of the lower robot  36 . 
         FIG. 55  is a front view of the lower robot  36  with its articulated arm portion retracted. 
         FIG. 56  is a back view of  FIG. 55 . 
         FIG. 57  is a perspective view of the lower robot  36  with its articulated arm portion retracted. 
         FIG. 58  is a side view of the lower robot  36  with its articulated arm portion retracted. 
         FIG. 59  is a top view of the lower robot  36  with its articulated arm portion retracted. 
         FIG. 60  is a perspective view of a gripper portion of the upper trolley mechanism. 
         FIG. 61  is a timing chart showing the workover system&#39;s sequence of operation in pulling sucker rods  66  out from within the wellbore. Various method steps are plotted versus a horizontal time reference that progresses generally from left to right. The chart shows several horizontal lines of method steps, wherein each line show a series of sequentially performed method steps, and a comparison of the horizontal lines identifies which method steps can occur simultaneously to minimize the overall cycle time. Completion of one cycle of method steps ending at the far right column of asterisks initiates a subsequent cycle that begins at the two left asterisks. Encircled hollow arrows function as a gate that blocks work flow from left to right through the arrow until the gate is opened by completion of a method step tied to the arrow via a dotted line. The encircled hollow arrows are analogous to a transistor or SCR that is triggered open by input to its gate terminal (dotted line). 
         FIGS. 61A ,  61 B,  61 C and  61 D are enlarged views of the corresponding  61 A,  61 B,  61 C and  61 D portions identified in  FIG. 61 . 
         FIG. 62  is a timing chart similar to  FIG. 61  but showing the steps involved in inserting sucker rods  66  in the wellbore. 
         FIGS. 62A ,  62 B,  62 C and  62 D are enlarged views of the corresponding  62 A,  62 B,  62 C and  61 D portions identified in  FIG. 62 . 
         FIG. 63  is a timing chart similar to  FIG. 61  but showing the steps involved in removing tubing  64  out from with the wellbore. 
         FIGS. 63A ,  63 B and  63 C are enlarged views of the corresponding  63 A,  63 B and  63 C portions identified in  FIG. 63 . 
         FIG. 64  is a timing chart similar to  FIG. 61  but showing the steps involved in inserting tubing member  66  in the wellbore. 
         FIGS. 64A ,  64 B,  64 C and  64 D are enlarged views of the corresponding  64 A,  64 B,  64 C and  61 D portions identified in  FIG. 64 . 
         FIG. 65  is a back view of the upper robot  90  with its articulated arm portion that holds end effector  92 . 
         FIG. 66  is a perspective view of the upper robot  90 . 
         FIG. 67  is a side view of the  FIG. 65 . 
         FIG. 68  is a top view of  FIG. 65 . 
         FIG. 69  is a perspective view of a hydraulic drive system that drives the vertical travel of the main trolley which carries elevator  106 . The hydraulic drive system comprises a larger cylinder  152 , a smaller cylinder  154  and a plurality of sheaves and cables.  FIG. 69  shows elevator  106  in its lowermost position. 
         FIG. 70  is a perspective view similar to  FIG. 69  but showing the larger cylinder  152  extended to raise elevator  106  to an intermediate height. 
         FIG. 71  is a perspective view similar to  FIG. 70  but showing the both cylinders extended to raise elevator  106  to its uppermost position. 
         FIGS. 72 ,  73  and  74  are side views corresponding to  FIGS. 69 ,  70  and  71  respectively. 
         FIG. 75  is a perspective view showing the upper robot  90  with its articulated arm extended and its end effector  92  at a laterally centered position. 
         FIG. 76  is a perspective view similar to  FIG. 75  but showing the articulated arm retracted. 
         FIG. 77  is a perspective view similar to  FIG. 76  but showing the shuttle  122  and the articulated arm both shifted laterally to one side of carriage  120 . 
         FIG. 78  is a perspective view similar to  FIG. 77  but showing the shuttle  122  and the articulated arm both shifted laterally to the other side of carriage  120 . 
         FIG. 79  is a schematic side view of an example workover vehicle driving to and parking at a well site. 
         FIG. 80  is a schematic side view similar to  FIG. 79  but showing a mast of the workover vehicle being raised. 
         FIG. 81  is a schematic side view similar to  FIGS. 79 and 80 . 
         FIG. 82A  is a schematic side view of the workover vehicle being used for removing a well string. 
         FIG. 82B  is a schematic right end view of  FIG. 82A . 
         FIG. 83A  is another schematic side view of the workover vehicle being used for removing the well string. 
         FIG. 83B  is a schematic right end view of  FIG. 83A . 
         FIG. 84A  is another schematic side view of the workover vehicle being used for removing the well string. 
         FIG. 84B  is a schematic right end view of  FIG. 84A . 
         FIG. 85A  is another schematic side view of the workover vehicle being used for removing the well string. 
         FIG. 85B  is a schematic right end view of  FIG. 85A . 
         FIG. 86A  is another schematic side view of the workover vehicle being used for removing the well string. 
         FIG. 86B  is a schematic right end view of  FIG. 86A . 
         FIG. 87A  is another schematic side view of the workover vehicle being used for removing the well string. 
         FIG. 87B  is a schematic right end view of  FIG. 87A . 
         FIG. 88A  is another schematic side view of the workover vehicle being used for removing the well string. 
         FIG. 88B  is a schematic right end view of  FIG. 88A . 
         FIG. 89A  is another schematic side view of the workover vehicle being used for removing the well string. 
         FIG. 89B  is a schematic right end view of  FIG. 89A . 
         FIG. 90A  is another schematic side view of the workover vehicle being used for removing the well string. 
         FIG. 90B  is a schematic right end view of  FIG. 90A . 
         FIG. 91A  is another schematic side view of the workover vehicle being used for removing the well string. 
         FIG. 91B  is a schematic right end view of  FIG. 91A . 
         FIG. 92A  is another schematic side view of the workover vehicle being used for removing the well string. 
         FIG. 92B  is a schematic right end view of  FIG. 92A . 
         FIG. 93A  is another schematic side view of the workover vehicle being used for removing the well string. 
         FIG. 93B  is a schematic right end view of  FIG. 93A . 
         FIG. 94A  is another schematic side view of the workover vehicle being used for removing the well string. 
         FIG. 94B  is a schematic right end view of  FIG. 94A . 
         FIG. 95A  is another schematic side view of the workover vehicle being used for removing the well string. 
         FIG. 95B  is a schematic right end view of  FIG. 95A . 
         FIG. 96A  is another schematic side view of the workover vehicle being used for removing the well string. 
         FIG. 96B  is a schematic right end view of  FIG. 96A . 
         FIG. 97A  is another schematic side view of the workover vehicle being used for removing the well string. 
         FIG. 97B  is a schematic right end view of  FIG. 97A . 
         FIG. 98A  is another schematic side view of the workover vehicle being used for removing the well string. 
         FIG. 98B  is a schematic right end view of  FIG. 98A . 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 79-98B , with further reference to  FIGS. 1-78 , illustrate an example method for removing a well string  172  from within a wellbore  14  at a well site  12 . In the illustrated example, well site  12  includes a pumpjack  174  with a walking beam  34  and a horse head  176 . Pumpjack  174  is used for actuating a reciprocating downhole pump. Wellbore  14  defines a longitudinal centerline  84 . Well string  172  when assembled comprises a plurality of shafts  180  interconnected end-to-end, wherein the plurality of shafts  180  includes at least an upper shaft  182  having an upper shaft weight, a lower shaft  184  having a lower shaft weight, and a remaining well string  186  below lower shaft  184 . The term, “shaft” means any solid or hollow elongate member used within a wellbore. Examples of shafts include, but are not limited to, sucker rods and tubing. In some examples, upper shaft  182  comprises a plurality of interconnected shaft segments (e.g., two or three). In some examples, upper shaft  182  is a single shaft segment. The same is true for lower shaft  184 . 
     Upper shaft  182  and lower shaft  184  can be anywhere along the full length of the total well string  172 . In some examples, shafts  182  and  184  are near the top of well string  172 . In some examples, shafts  182  and  184  are near the bottom of well string  172 . In some examples, shafts  182  and  184  are at some intermediate elevation along the length of well string  172 . The described method for removing well string  172  will explicitly cover the removal of two example shafts  182  and  184  and thus also cover the method for transitioning between the removal of two shafts. The method as described with reference to shafts  182  and  184  also applies to other shafts of well string  172 . 
     The method involves driving a workover vehicle  10  to well site  12 . Workover vehicle  10 , in some examples, comprises a mast  20 , an upper robot  90 , a lower robot  36 , an upper trolley mechanism  98 , and a main trolley  156  carrying an elevator head  106 . Mast  20  includes a trolley track system  88  and a transfer track system  86  that are parallel to each other. In some examples, trolley track system  88  is one pair of continuous rails. In some examples, trolley track system  88  comprises an upper set of tracks for upper trolley mechanism  98  and a lower set of tracks for main trolley  156 . In some examples, transfer track system  86  is one pair of continuous rails. In some examples, transfer track system  86  comprises an upper set of tracks for upper robot  90  and a lower set of tracks for lower robot  36 . 
     Upper robot  90  comprises an upper carriage  120 , an upper shuttle  122  and an articulated upper arm assembly  158 . Upper carriage  120  travels vertically along transfer track system  86 , as indicated by arrow  198  in  FIG. 82A , thus arrow  198  illustrates upper robot  90  selectively ascending and descending along transfer track system  86 . Upper shuttle  122  travels along horizontal tracks on upper carriage  120 , as indicated by arrows  160  in  FIG. 82B . Upper arm assembly  158  travels along horizontal tracks on upper shuttle  122 , as indicated by arrows  162  in  FIG. 82B . The term, “robot” and derivatives thereof means any computer or microprocessor controlled mechanism for moving a part (e.g., a shaft such as a sucker rod or tubing) in multiple dimensions or directions simultaneously or sequentially. 
     Likewise, lower robot  36  comprises a lower carriage  121 , a lower shuttle  123  and an articulated lower arm assembly  164 . Lower carriage  121  travels vertically along transfer track system  86 , as indicated by arrow  200  in  FIG. 82A , thus arrow  200  illustrates lower robot  36  selectively ascending and descending along transfer track system  86 . Lower shuttle  123  travels along horizontal tracks on lower carriage  121 , as indicated by arrows  166  in  FIG. 82B . Lower arm assembly  164  travels along horizontal tracks on lower shuttle  123 , as indicated by arrows  168  in  FIG. 82B . The various components of robots  36  and  90  are capable of moving independently and in unison, depending on the need. Arrow  210  of  FIG. 83A , for instance, shows lower carriage  121  descending while upper carriage  120  is stationary to vary a vertical separation distance  212  between robots  36  and  90 , thus arrow  210  illustrates varying vertical separation distance  212  between upper robot  90  and lower robot  36  as a result of lower robot  36  traveling relative to upper robot  90 . 
     After driving vehicle  10  to well site  12 , a mast  20  of vehicle  10  is pivotally raised at well bore  14 , as indicated by arrow  188  of  FIG. 80 . To provide working clearance  48  ( FIG. 82A ) with adjacent pumpjack  174 , horse head  176  plus sometimes walking beam  34  are removed from pumpjack  174 , as indicated by arrows  190  and  192  of  FIG. 80 .  FIG. 81 , for instance, shows an example where horse head  176  is removed while walking beam  34  is left in place. 
     In some examples, removing well string  172  involves various actions, which are illustrated in the drawings but not necessarily performed in the following order. Arrow  170  of  FIG. 79  represents driving workover vehicle  10  to well site  12 , and  FIGS. 80 ,  81  and  82 A illustrate leaving at least a portion  174 ′ of pumpjack  174  intact at well site  12 . Arrow  170  and  FIGS. 79 ,  80 ,  81  and  82 A represent parking workover vehicle  10  at well site  12  such that longitudinal centerline  84  is interposed between workover vehicle  10  and intact portion  174 ′ of pumpjack  174 . An imaginary vector  112   a ′ pointing horizontally from intact pumpjack portion  174 ′, passing through longitudinal centerline  84  toward workover vehicle  10  defines a forward direction, and an imaginary horizontal line  112   b  perpendicular to forward direction  112   a ′ defines a lateral direction. 
       FIGS. 82A and 82B  show a wellhead slip  110  clamping onto upper shaft  182  and supporting most of the weight of upper shaft  182 , lower shaft  184  plus the weight of the remaining well string  186 . In some examples, wellhead slip  110  comprises a series of wedges circumferentially distributed around well string  172 . In some examples, the wedges are selectively clamped (e.g.,  FIG. 82A ) and released (e.g.,  FIG. 84A ) by air-over-hydraulic actuation under command of a controller  129  (e.g., computer, programmable logic controller, etc.). 
     In some examples, controller  129  controls the movement and timing coordination of generally all of the working components associated with workover vehicle  10 . In some examples, controller  129  controls the movement and timing coordination of less than all of the working components associated with workover vehicle  10 . Examples of such working components include, but are not limited to, tongs mechanism  132 , main trolley  156 , elevator head  106 , lower robot  36 , upper robot  90 , upper trolley mechanism  98 , various sensors, encoders, motors, piston/cylinders, pumps, hydraulic valves, actuators, pneumatic valves, etc. In some examples, the movement of the various working components is driven by available means examples of which include, but are not limited to, piston/cylinders, electric motors, hydraulic motors, pneumatic motors, chain and sprockets, etc. 
     While wellhead slip  110  is supporting the weight of well string  172 , controller  4  commands main trolley  156  to travel upward (arrow  194  of  FIG. 82A ) along trolley track system  88  until elevator head  106  captures an upper end  196  of upper shaft  182  as shown in  FIGS. 83A and 83B . In some examples, upper end  196  is a coupling or collar with internal threads for joining two shafts end-to-end.  FIGS. 86A and 86B  show the jaws of elevator head  106  retracted and open, and  FIGS. 83A and 83B  show the jaws of elevator head  106  extended and closed for capturing upper shaft  182 . Elevator head  106  is schematically illustrated to represent any device for engaging and lifting a shaft (e.g., shaft  182  and  184 ). In some examples, elevator head  106  includes jaws for selectively engaging and releasing the upper end of a shaft. In some examples, such jaws clamp onto and capture the shaft or a collar thereon. In some examples, elevator jaws do not clamp onto the shaft or collar thereon but instead hook onto or otherwise capture the upper end of the shaft. Examples of non-clamping elevator jaws include, but are not limited to, a U-shaped holder, latch, hook, fork, yoke, clevis, etc. In some examples, elevator head  106  selectively extends and retracts (in direction  112   a ) relative to main trolley  156 . 
     Referring to  FIGS. 83A and 83B , arrows  214  represent wellhead slip  110  releasing upper shaft  182 . Arrow  216  represents transferring most of the upper shaft&#39;s weight and the lower shaft&#39;s weight from wellhead slip  110  to elevator head  106 . Arrow  216  of  FIGS. 83A and 83B  and arrow  218  of  FIGS. 84A and 84B  represent main trolley  156  traveling upward at a first peak velocity along trolley track system  88 , thereby raising well string  172  and lifting upper shaft  182  out from within well bore  14 .  FIGS. 84A and 84B  also show that in some examples articulated upper arm assembly  158  and articulated lower arm assembly  164  translate laterally closer to centerline  84 , as indicated by arrows  224  and  226 . 
     To determine when to stop lifting well string  172  and begin the operations shown in  FIGS. 85A ,  85 B,  86 A,  86 B,  92 A,  92 B,  93 A and  93 B, some examples of workover vehicle  10  include a coupling sensor  77  (see  FIGS. 82A and 82B ) for sensing when a well string joint is at a predetermined desired elevation. Sensor  77  enables the automation of the well string removal method without the necessity of manual intervention between each cycle (one cycle being the removal of one well string shaft). In some examples, joint sensor  77  is a non-contact proximity sensor (e.g., Hall Effect, optical detection, ultrasonic detection, laser, etc.), that provides a signal to controller  129  upon sensing the proximity of an enlarged-diameter section of well string  172 , wherein such an enlarged-diameter section is evidence of a joint. The step of sensing a joint (first joint, second joint, etc.) is at a predetermined desired elevation is illustrated in  FIGS. 61B and 63A  by way of the encircled action labeled, “Sensor detects collar: stop.” 
     Referring to  FIGS. 85A and 85B , arrows  220  represent wellhead slip  110  clamping onto lower shaft  184 . Arrow  222  represents main trolley  156  momentarily lowering well string  172  while well head slip  110  is clamping onto lower shaft  184 . During the well string&#39;s relatively short perceptible descent (e.g., about 4 inches or even as little as a fraction of an inch) the wedges of wellhead slip  110  become tightly wedged against lower shaft  184 . The wedges becoming sufficiently tight results in wellhead slip  110  holding lower shaft  184  at a substantially constant elevation for a first period, as shown in  FIGS. 86A and 86B . 
     After briefly lowering well string  172  and during the first period, elevator head  106  releases upper shaft  182 , thereby transferring most of the upper shaft&#39;s weight and the lower shaft&#39;s weight from elevator head  106  to wellhead slip  110 , as illustrated by arrows  222  and  228  of  FIGS. 85A ,  85 B,  86 A and  86 B and additionally illustrated by elevator head  106  being shown retracted in forward direction  112   a ′ ( FIG. 86A ) and being shown open ( FIG. 86B ) while wellhead slip  110  is shown clamped tightly against lower shaft  184 . To help stabilize the upper end of upper shaft  182 , upper trolley mechanism  98  (which is above elevator head  106 ) travels downward (arrow  230  of  FIGS. 85A and 85B ) along trolley track system  88  to engage upper shaft  182 , as shown in  FIGS. 86A and 86B . 
     Arrow  232  of  FIG. 85A  represents tongs mechanism  132  extending, and arrow  234  of  FIG. 86A  represents tongs mechanism  132  unscrewing a first joint  236  connecting upper shaft  182  to lower shaft  184 . Tongs mechanism  132  is schematically illustrated to represent any powered tool suitable for unscrewing joints, collars or couplings of a well string  172 . In some examples, tongs mechanism  132  includes an actuator (e.g., a hydraulic cylinder) for selectively extending (arrow  232 ) and retracting (arrow  246 ) relative to centerline  84 . 
     In some examples, to save overall cycle time, elevator head  106  descends while tongs  132  is unscrewing joint  236 . Arrow  228  represents main trolley  156  lowering elevator head  106  while lower shaft  184  is at a substantially constant elevation and while tongs mechanism  132  is unscrewing joint  236 . To further save cycle time, in some examples, robots  36  and/or  90  are repositioned or are traveling while main trolley  156  is raising or lowering elevator head  106 .  FIG. 85B , for example, shows arrows  222  and  224  that when such movement occurs simultaneously, arrows  222  and  224  illustrate main trolley  156  lowering elevator head  106  while the robotic system is moving end effectors  92  and/or  96  between shaft storage area  73  and longitudinal centerline  84 . In some examples, robots  36  and/or  90  are repositioned or are traveling while tongs mechanism  132  is unscrewing joint  236 . 
     After unscrewing first joint  236 , after end effectors  92  and/or  96  gripping upper shaft  182 , and after upper trolley mechanism  98  disengages  238  upper shaft  182 , the robotic system (i.e., robots  36  and/or  90 ) transfers upper shaft  182  from longitudinal centerline  84  of well bore  14  to a shaft storage area  73  that is horizontally spaced apart from centerline  84 , wherein the robotic system transferring upper shaft  182  from centerline  84  to shaft storage area  73  involves moving upper shaft  182  in translation in forward direction  112   a ′ and lateral direction  112   b . Such translation allows the robotic system to avoid the danger and high rotational inertia associated with pivoting or swinging relatively long and heavy shafts. Examples of shaft storage area  73  include, but are not limited to, tubing storage rack  72  and rod storage rack  74 .  FIG. 87A  shows articulated arm assemblies  158  and  164  extending and end effectors  92  and  96  gripping upper shaft  182  while upper trolley mechanism  98  is above end effector  92  and/or  96  and while elevator head  106  is below end effector  92  and/or  96 . Arrows  256  of  FIG. 87A  represent robots  36  and  90  selectively engaging and releasing upper shaft  182  via the robot&#39;s end effectors  92  and  96 . 
     In transferring upper shaft  182  from centerline  84  to shaft storage area  73 , arrow  246  represents tongs  132  retracting to provide clearance for main trolley  156  to descend (arrow  248 ) below tongs  132  and to provide some clearance for upper shaft  182  to travel to shaft storage area  73 . Arrow  240  represents arm assemblies  158  and  164  retracting, whereby shaft  182  translates in a rearward direction (opposite to forward direction  112   a ′) for creating clearance during subsequent lateral translation. Arrow  242  represents end effectors  92  and  96  translating (e.g., via relative lateral movement between arm  158  and upper shuttle  122  and/or via relative lateral movement between upper shuttle  122  and upper carriage  120 ), whereby shaft  182  translates in lateral direction  112   b  toward shaft storage area  73 . Arrow  244  represents arm assemblies  158  and  164  extending, whereby shaft  182  translates from its position shown in  FIG. 88A  to its position shown in  FIG. 89A . Arrows  250  and  252  represent end effectors  92  and  96  releasing upper shaft  182  at shaft storage area  73 . 
     Referring to  FIGS. 90A ,  90 B,  91 A and  91 B, arrow  254  represents robotic arms  158  and  164  retracting after leaving upper shaft  182  at shaft storage area  73 . At this point, after having removed upper shaft  182 , workover vehicle  10  prepares for removing lower shaft  184  from the remaining well string  172 . In  FIGS. 90A and 90B , arrow  256  represents elevator head  106  capturing the upper end of lower shaft  184 . In  FIGS. 91A and 91B , arrows  214  represent wellhead slip  110  releasing lower shaft  184 , thereby transferring most of the lower shaft&#39;s weight to elevator head  106 . Arrow  218 ′ of  FIGS. 91A and 91B  represents main trolley  156  traveling upward at a second peak velocity along trolley track system  88 , thereby lifting the remaining shaft string  186  and lifting lower shaft  184  out from within well bore  14 . To reduce well string disassembly time by taking advantage of the well string&#39;s diminishing weight as additional shafts are removed, in some examples, said second peak velocity (see arrow  218 ′ of  FIG. 91A ) is greater than said first peak velocity (see arrow  218  of  FIG. 84A ). 
     In  FIGS. 92A and 92B , arrows  220 ′ represents wellhead slip  110  clamping onto the remaining shaft string  186 . Arrow  222 ′ represents main trolley  156  momentarily lowering lower shaft  184  and the remaining shaft string  186  while wellhead slip  110  is clamping onto the remaining shaft string  186 . During the well string&#39;s relatively short descent, e.g., about 4 inches, the wedges of wellhead slip  110  become tightly wedged against the remaining shaft string  186 . The wedges becoming sufficiently tight results in wellhead slip  110  holding the remaining shaft string  186  at a substantially fixed elevation for a second period, as shown in  FIGS. 93A and 93B . 
     After briefly lowering well string  172  and during the second period, elevator head  106  releases lower shaft  184 , thereby transferring most of the lower shaft&#39;s weight and the weight of the remaining shaft string  186  from elevator head  106  to wellhead slip  110 , as illustrated by arrows  222 ′ and  228 ′ of  FIGS. 92A ,  92 B,  93 A and  93 B and additionally illustrated by elevator head  106  being shown retracted in forward direction  112   a ′ ( FIG. 93A ) and being shown open ( FIG. 93B ) while wellhead slip  110  is shown clamped tightly against the remaining shaft string  186 . To help stabilize the upper end of lower shaft  182 , upper trolley mechanism  98  (which is above elevator head  106 ) travels downward (arrow  230  of  FIGS. 92A and 92B ) along trolley track system  88  to engage the upper end of lower shaft  184 , as shown in  FIGS. 93A and 93B . 
     Arrow  232  of  FIG. 92A  represents tongs mechanism  132  extending, and arrow  234  of  FIG. 93A  represents tongs mechanism  132  unscrewing a second joint  236 ′ connecting lower shaft  184  to the remaining shaft string  186 . In some examples, to save overall cycle time, elevator head  106  descends while tongs  132  is unscrewing joint  236 ′. Arrow  228 ′ represents main trolley  156  lowering elevator head  106  while the remaining shaft string  186  is at a substantially constant elevation and while tongs mechanism  132  is unscrewing joint  236 ′. 
     After unscrewing second joint  236 ′, after end effectors  92  and/or  96  gripping lower shaft  184 , and after upper trolley mechanism  98  disengages  238  lower shaft  184 , the robotic system (i.e., robots  36  and/or  90 ) transfers lower shaft  184  from longitudinal centerline  84  of well bore  14  to shaft storage area  73 , wherein the robotic system transferring lower shaft  184  from centerline  84  to shaft storage area  73  involves moving lower shaft  184  in translation in forward direction  112   a ′ and lateral direction  112   b .  FIG. 94A  shows articulated arm assemblies  158  and  164  extending and end effectors  92  and  96  gripping lower shaft  182  while upper trolley mechanism  98  is above end effector  92  and/or  96  and while elevator head  106  is below end effector  92  and/or  96 . 
     In transferring lower shaft  184  from centerline  84  to shaft storage area  73 , arrow  246  ( FIG. 94A ) represents tongs  132  retracting to provide clearance for main trolley  156  to descend (arrow  248 ) below tongs  132  and to provide some clearance for lower shaft  184  to travel to shaft storage area  73 . Arrow  240  represents arm assemblies  158  and  164  retracting, whereby shaft  184  translates in a rearward direction (opposite to forward direction  112   a ′) for creating clearance during subsequent lateral translation. Arrow  242  ( FIG. 94B ) represents end effectors  92  and  96  translating (e.g., via relative lateral movement between arm  158  and upper shuttle  122  and/or via relative lateral movement between upper shuttle  122  and upper carriage  120 ), whereby shaft  184  translates in lateral direction  112   b  toward shaft storage area  73 . Arrow  244  ( FIG. 95A ) represents arm assemblies  158  and  164  extending, whereby shaft  184  translates from its position shown in  FIG. 95A  to its position shown in  FIG. 96A . Arrows  250 ′ and  252 ′ ( FIG. 96A ) represent end effectors  92  and  96  releasing lower shaft  184  at shaft storage area  73 . Referring to  FIGS. 97A ,  97 B,  98 A and  98 B, arrow  254  represents robotic arms  158  and  164  retracting after leaving lower shaft  184  at shaft storage area  73 . 
     More specifically, additionally and/or alternatively, some example embodiments are described under the following underlined subtitles (1)-(24): 
     (1) X,Y Frame Translation after Deploying Outriggers and Leveling 
     Some example embodiments include a workover method involving the use of a workover vehicle  10  at a well site  12 , wherein the well site comprises a wellbore  14 , and the workover vehicle comprises a sub frame  16  on vehicle chassis  18  with a mast  20  attached to the sub frame, the workover method comprising: 
     parking  22  the workover vehicle at the well site; 
     deploying  24  a plurality of outriggers  26  of the workover vehicle; 
     leveling  28  the sub frame; 
     horizontally shifting  30  the sub frame relative to the chassis and the wellbore; 
     pivoting the mast upward; and further comprising an optical sensor  32  (e.g., a camera or laser) assisting in aligning a reference point of the sub frame to the wellbore. 
     (2) Lower Robot Avoids Walking Beam as Mast is Raised 
     Some example embodiments include a workover method involving a workover vehicle  10 , a wellbore  14 , and a walking beam  34  associated with the wellbore, wherein the workover vehicle comprises a mast  20  and a robot  36 , the workover method comprising: 
     positioning the workover vehicle in proximity with the wellbore and the walking beam; 
     positioning the robot at a predetermined safe location on the mast; 
     pivoting  40  the mast to an upright orientation at a location  38  proximate the walking beam, wherein the robot at the predetermined safe location clears the walking beam as the mast pivots to the upright orientation; and 
     moving  42  the robot from the predetermined safe location to an operative location  44  on the mast. 
     (3) Detect Interference with Walking Beam 
     Some example embodiments include a workover system for use at a wellbore  14  associated with a walking beam  34 , the workover system comprising: 
     a workover vehicle  10 ; 
     a mast  20  extending upright from the workover vehicle; 
     a robot  36  mounted for vertical movement along the mast; and 
     a sensor  46  (e.g., proximity sensor, limit switch, photoelectric eye, etc.) establishing and/or determining whether a predetermined minimum clearance  48  exists between the robot and the walking beam or the portion  174 ′ of pumpjack  174  that is left intact at well site  12 . 
     (4) Tilting Oil Tank 
     Some example embodiments include a workover system, comprising: 
     a vehicle bed  50 ; 
     a mast  20  mounted to the vehicle bed, the mast being moveable selectively to a lowered position and a raised position; 
     a main trolley  52  mounted for vertical movement along the mast when the mast is in the raised position, the main trolley being moveable from a descended position to an elevated position; 
     a hydraulic tank  54  mounted to the vehicle bed, the hydraulic tank being moveable selectively between a transport position and an operative position, the hydraulic tank defining a tank outlet  56 , the tank outlet being at a hydraulic pressure that is greater when the hydraulic tank is in the operative position than when the hydraulic tank is in the transport position; 
     a hydraulic pump  58  mounted to the vehicle bed, the hydraulic pump defining a suction inlet  60  connected in fluid communication with the tank outlet; and 
     a hydraulic drive unit  62  connected to move the lower trolley from the descended position to the elevated position, wherein the hydraulic tank contains more hydraulic fluid when the hydraulic tank is in the transport position than when the hydraulic tank is in the operative position. 
     (5) Mast Layout 
     Some example embodiments include a workover system for handling at least one of a plurality of tubes  64  and a plurality of rods  66  at a well site  12  that includes a wellbore  14 , the workover system comprising: 
     a mast  20  comprising a plurality of outer corner posts  68  distributed along an outer periphery  70  of the mast, the plurality of outer corner posts defining a footprint of the mast; 
     a tubing storage rack  72  for holding the plurality of tubes in a generally upright orientation, the tubing storage rack being mostly within the footprint; and 
     a rod storage rack  74  for holding the plurality of rods in a generally upright orientation, the rod storage rack being mostly beyond the footprint, and further comprising a lay-down storage area  76  for storing at least one of a first portion of the plurality of rods and a second portion of the plurality of tubes, the lay-down storage area being disposed mostly beyond the footprint, and further comprising a rack cover  78  disposed above at least one of the tubing storage rack and the rod storage rack, and further comprising a camera  80  disposed above at least one of the tubing storage rack and the rod storage rack, and further comprising a robot  36  attached to the mast with a portion  82  of the robot extending beyond the footprint, the wellbore defining a vertical centerline  84  that is interposed between the footprint of the mast and the portion of the robot, and further comprising: 
     a wider track  86  borne by the mast, the wider track lying along a first imaginary plane  94 ; 
     a narrower track  88  borne by the mast; 
     an upper robot  90  mounted for vertical travel along the wider track, the upper robot having an upper end effector  92  moveable selectively to within the footprint and beyond the footprint, the upper end effector being moveable to pass through the first imaginary plane; 
     a lower robot  36  mounted for vertical travel along the wider track, the lower robot having a lower end effector  96  moveable selectively to within the footprint and beyond the footprint, the lower end effector being moveable to pass through the first imaginary plane; 
     an upper trolley  98  mounted for vertical movement along the narrower track; 
     a lower main trolley  100  mounted for vertical movement along the narrower track; and 
     a robotic jib  102  pivotally attached the mast. 
     (6) Fold-up Racks for Transport 
     Some example embodiments include a workover system comprising: 
     a workover vehicle  10  being selectively configurable to a operative configuration and a transport configuration; 
     a mast  20  attached to the workover vehicle, the mast defining a longitudinal centerline  104 , the mast being substantially vertical in the operative configuration, the mast being laid down in the transport configuration; and 
     a rod storage rack  74 / 74 ′ pivotally attached to the mast, the rod storage rack  74  being substantially perpendicular to the longitudinal centerline when the workover vehicle is in the operative configuration, the rod storage rack  74 ′ being substantially parallel to the longitudinal centerline when the workover vehicle is in the transport configuration. 
     (7) Robotic Jib-Deployed and Transport Positions 
     Some example embodiments include a workover system, comprising: 
     a workover vehicle  10  being selectively configurable to a operative configuration and a transport configuration; 
     a mast  20  attached to the workover vehicle, the mast comprising a plurality of outer corner posts  68  distributed along an outer periphery of the mast, the plurality of outer corner posts  68  defining a footprint of the mast, the mast being substantially vertical in the operative configuration, the mast being laid down in the transport configuration; and 
     a robotic jib  102  attached to the mast, the robot jib being disposed mostly within the footprint when the workover vehicle is in the transport configuration, the robot jib being most beyond the footprint when the workover vehicle is in the operative configuration. 
     (8) Set and Update Overload Weight Limit &amp; Minimal Oil Discharge Pressure 
     Some example embodiments include a workover method comprising: 
     determining a first anticipated maximum load for a well string; 
     during a first period, shortening the well string to create a shorter well string; 
     determining a second anticipated maximum load for the shorter well string; 
     during a second period, shortening the shorter well string to create an even shorter well string; 
     establishing a first oil pressure limit based on the first anticipated maximum load for the well string; 
     establishing a second oil pressure limit based on the second anticipated maximum load for the shorter well string; 
     during the first and second period, discharging oil at a discharge pressure that varies; 
     limiting the discharge pressure to the first oil pressure limit during the first period; and 
     limiting the discharge pressure to the second oil pressure limit during the second period, wherein the first oil pressure limit is greater than the second oil pressure limit, wherein the second oil pressure limit is less than a minimum discharge pressure necessary to handle the first anticipated maximum load for the well string, and further comprising: 
     establishing an upper maximum velocity limit (e.g., 6 ft/sec) for an elevator that is generally unloaded; 
     establishing a lower maximum velocity limit (e.g., 2 ft/sec) for the elevator when the elevator is carrying a load; and 
     establishing a maximum acceleration limit (e.g., 0.1 g) for the elevator. 
     (9) Log Snag Points POOH 
     Some example embodiments include a workover method comprising: 
     supplying oil at a pressure that varies; 
     using the pressure as means for raising an elevator  106  connected to a well string  108 ; 
     monitoring an elevation of the elevator, wherein the elevation increases while raising the elevator; 
     monitoring the pressure while raising the elevator; 
     if the pressure experiences a certain spike in pressure, a controller noting the elevation at which the certain spike occurred; and 
     determining a location within the wellbore based on the elevation at which the certain spike occurred. 
     Some example embodiments include a workover method comprising: 
     determining a first anticipated maximum load for a well string; 
     during a first period, shortening the well string to create a shorter well string; 
     determining a second anticipated maximum load for the shorter well string; 
     during a second period, shortening the shorter well string to create an even shorter well string; 
     establishing a first oil pressure limit based on the first anticipated maximum load for the well string; 
     establishing a second oil pressure limit based on the second anticipated maximum load for the shorter well string; 
     during the first and second period, discharging oil at a discharge pressure that varies; 
     limiting the discharge pressure to the first oil pressure limit during the first period; and 
     limiting the discharge pressure to the second oil pressure limit during the second period, wherein the first oil pressure limit is greater than the second oil pressure limit, wherein the second oil pressure limit is less than a minimum discharge pressure necessary to handle the first anticipated maximum load for the well string. 
     (10) Detect RIH Stack-Out 
     Some example embodiments include a workover method for handling a well string  108  through the use of an elevator  106  carried by a lower trolley  52  that travels along a mast  20 , the workover method comprising: 
     the elevator suspending the well string; 
     a sensor (e.g., an encoder) determining whether the elevator is descending; 
     monitoring at least one of: cable tension, crown load strain and hydraulic pressure; 
     identifying a notable decrease in at least one of: cable tension, crown load strain and hydraulic pressure; and 
     determining a stack-out condition in the event of the notable decrease occurring while the elevator is descending. 
     (11) Push/Pull Cable and Sheaves 
     Some example embodiments include a workover method for handling at least one of a tubing string and a rod string, the workover method involving the use of a workover vehicle  10 , a mast  20  attached to the workover vehicle, a main trolley  52  attached to the mast, an elevator  106  attached to the main trolley, a large hydraulic cylinder  152 , a small hydraulic cylinder  154 , the workover method comprising: 
     during a first period, suspending the tubing string and not the rod string from the elevator; 
     while the tubing string is suspended from the elevator, extending the large hydraulic cylinder and not the small hydraulic cylinder to lift the elevator and the tubing string; 
     during a second period, suspending the rod string and not the tubing string from the elevator; and 
     while the rod string is suspended from the elevator, extending the large hydraulic cylinder and the small hydraulic cylinder to lift the elevator and the rod string, and further comprising: 
     during a third period, having the elevator be disengaged from both the tubing string and the rod string; and 
     during the third period, retracting at least one of the large hydraulic cylinder and the small hydraulic cylinder to forcibly lower by hydraulic pressure the main trolley and the elevator. 
     (12) Sense Slip and Elevator Weights to Detect Well String Freefall 
     Some example embodiments include a workover method for handling a well string  108  that under normal operating conditions has a weight carried by at least one of a wellhead slip  110  and an elevator  106 , wherein the wellhead slip is at a wellhead  112  of a wellbore  14 , and the elevator is carried by a main trolley  52  mounted for vertical travel along a mast  20  at the well site  12 , the workover method comprising: 
     sensing a first weight carried by the wellhead slip; 
     sensing a second weight carried by the elevator; and 
     identifying a freefall hazard based on a sum of the first weight and the second weight being less than a predetermined minimum, wherein the predetermined minimum varies as a function of a length of the well string. 
     (13) Upper Gripper Functions with Lost Hydraulic Pressure 
     Some example embodiments include a workover system for handling a separated section of a well string  108  at a well site  12  that includes a wellbore  14 , the workover system comprising: 
     a workover vehicle  10 ; 
     a hydraulic power unit  62  supplying active hydraulic pressure; 
     a hydraulic storage system  114  maintaining stored hydraulic pressure; 
     a mast  20  extending upright from the workover vehicle; 
     a main trolley  52  mounted for vertical travel along the mast; 
     an elevator  106  carried by the main trolley; 
     an upper robot  90  mounted for vertical travel along the mast; and 
     an upper end effector  92  borne by the upper robot, the upper end effector being mounted for two-dimensional horizontal travel  112   a  and  112   b  relative to the mast, the upper end effector having a full grip mode, a backup grip mode and a release mode, the upper end effector in the full grip mode engaging the separated section under impetus of the active hydraulic pressure, the upper end effector in the backup grip mode engaging the separated section under impetus of the stored hydraulic pressure, the upper end effector in the release mode disengaging the separated section, wherein the hydraulic storage system includes a pilot-operated check valve  116  and an accumulator  118 , and further comprising a less urgent backup pressure alarm and a more urgent low pressure alarm. 
     (14) Independent Traveling Upper Robot, Lower Robot, Main Trolley and Upper Trolley 
     Some example embodiments include a workover system for handling a well string  108  at a well site  12  that includes a wellbore  14 , the workover system comprising: 
     a workover vehicle  10 ; 
     a mast  20  mounted to the workover vehicle; 
     an upper robot  90  mounted for vertical travel along the mast; 
     a lower robot  36  mounted for vertical travel along the mast, the lower robot being movable relative to the upper robot; 
     an upper trolley  98  mounted for vertical travel along the mast, the upper trolley being movable relative to the upper robot and the lower robot; and 
     a lower trolley  52  mounted for vertical travel along the mast, the lower trolley being movable relative to the upper robot, the lower robot and the upper trolley. 
     (15) Tube/Rod Gap and Dual Track Translation Provides Robots with Greater Side Travel 
     Some example embodiments include a workover system for handling a well string member  64  or  66 , the workover system comprising: 
     a workover vehicle  10 ; 
     a mast  20  attached to the workover vehicle; 
     a carriage  120  mounted for travel in a vertical direction  112   c  along the mast; 
     a shuttle  122  mounted to the carriage, the shuttle being movable in a lateral direction relative to the carriage, the lateral direction being substantially perpendicular to the vertical direction; 
     an end effector  92  carried by the shuttle, the end effector being movable in the lateral direction relative to the shuttle, the end effector being further movable in an in-out direction  112   a  relative to the shuttle, the in-out direction being substantially perpendicular to the lateral direction and the vertical direction, wherein the carriage has a maximum width  124  in the lateral direction, the end effector having a maximum travel distance  125  in the lateral direction, the maximum travel distance being greater than the maximum width, wherein the shuttle and the carriage define therebetween a passageway  126  for the well string member, the passageway lying substantially perpendicular to the in-out direction, the passageway extending a lateral distance in the lateral direction, the lateral distance being greater than the maximum width of the carriage. 
     (16) Robots can Pick from Rack or from Robotic Jib 
     Some example embodiments include a workover method for handling a well string member  64  or  66 , the workover method involving the use of a workover vehicle  10 , a mast  20 , a storage rack  74  attached to the mast, a robotic jib  102  attached to the mast, an upper robot  90  attached to the mast wherein the upper robot includes an end effector  92 , the workover method comprising: 
     pivoting the mast relative to the workover vehicle; 
     pivoting  135  the robotic jib relative to the mast; 
     moving the upper robot vertically along the mast; and 
     transferring the well string member selectively between: (a) the end effector and the robotic jib, and (b) the end effector and the storage rack. 
     (17) Sort Well String Members 
     Some example embodiments include a workover method for handling a plurality of well string members  64  or  66  associated with a wellbore  14 , the plurality of well string members includes at least one of a better well string member, a worse well string member and a seriously flawed well string member, the workover method involves the use of at least one of a workover vehicle  10 , a mast  20  attached to the workover vehicle, an elevator  106  mounted for vertical travel along the mast, a robot  90  mounted for vertical travel along the mast, a first storage area, a second storage area and a third storage area, the workover method comprising: 
     during a first period, the elevator extracting the plurality of well string members out from within the wellbore; 
     during the first period, electronically inspecting the plurality of well string members; 
     generating a plurality of readings as a consequence of electronically inspecting the plurality of well string members, 
     identifying the better well string member based on the plurality of readings; 
     identifying the worse well string member based on the plurality of readings; 
     the robot transferring the better well string member from the elevator to the first storage area; 
     the robot transferring the worse well string member from the elevator to the second storage area; and 
     during a second period, lowering at least some of the plurality of well string members into the wellbore such that the better well string member is below the worse well string member, wherein the step of electronically inspecting the plurality of well string member involves the use of at least one of an ultrasonic sensor, Hall effect sensor, means for sensing a magnetic flux field, and a camera, and further comprising automatically marking (e.g., painting) at least one of the better well string member and the worse well string member, and further comprising: 
     identifying the seriously flawed well string member based on the plurality of readings; and 
     the robot transferring the seriously flawed well string member from the elevator toward the third storage area. 
     (18) Sense Load on Well String Member to Detect Well String Member Encountering Floor 
     Some example embodiments include a workover method for handling a well string member  64  or  66 , the workover method involving at least one of a controller  129 , a robot  90  with an end effector  92 , and a storage rack  72  with a floor  128 , comprising: 
     under command of the controller, the end effector lowering the well string member into the storage rack; 
     sensing a weight carried by the end effector; 
     while sensing the weight carried by the end effector, sensing an appreciable decrease in the weight as the end effector lowers the well string member into the storage rack; and 
     in response to sensing the appreciable decrease in the weight, the controller determining that the well string member has encountered the floor of the storage rack. 
     (19) Means for Detecting Upper End of Variable Length Tubing During RIH 
     Some example embodiments include a workover method, comprising: 
     storing the well tubing member  64  in a storage rack  72 ; 
     under command of the controller, the end effector mechanism  92  ascending at a higher speed toward the shoulder of the well tubing member; 
     the end effector mechanism sensing the shoulder; 
     upon sensing the shoulder, the end effector mechanism decelerating to a lower speed; 
     the end effector mechanism engaging the shoulder; and 
     the end effector lifting the well tubing member out from within the storage rack. 
     (20) Sense Break-out 
     Some example embodiments include a workover method for unscrewing a tubing joint  130  and a rod joint  138 , the workover method involving at least one of a controller, a tongs mechanism  132 , an upper trolley mechanism  98  above the tongs mechanism, a first sensor  136  in communication with the controller, and a second sensor  134  in communication with the controller, the workover method comprising: 
     the tongs mechanism unscrewing the tubing joint; 
     while unscrewing the tubing joint, the first sensor sensing an abrupt upward movement of the tongs mechanism; 
     in response to sensing the abrupt upward movement of the tongs mechanism, the controller recognizing the tubing joint has separated; 
     the upper trolley mechanism unscrewing the rod joint; 
     while unscrewing the rod joint, the second sensor sensing an abrupt upward movement of the upper trolley mechanism; and 
     in response to sensing the abrupt upward movement of the upper trolley mechanism, the controller recognizing the rod joint has separated. 
     (21) Upper Trolley Screws/Unscrews Rods 
     Some example embodiments include a workover method for unscrewing a tube  64  at a tubing joint  130  and a rod  66  at a rod joint  138 , the workover method involving at least one of a tongs mechanism  132  and an upper trolley mechanism  98  above the tongs mechanism, the workover method comprising: 
     the tongs mechanism unscrewing the tubing joint; 
     while unscrewing the tubing joint via the tongs mechanism, the upper trolley mechanism stabilizing  140  an upper tube end  142  of the tube; 
     during a first period, the tongs mechanism partially unscrewing the rod joint; and 
     during a second period following the first period, the upper trolley mechanism finishing unscrewing  144  the rod joint, wherein the upper trolley member includes a pinch valve for gripping and turning the rod. 
     Some example embodiments include a workover method for screwing together a tube  64  at a tubing joint  130  and a rod  66  at a rod joint  138 , the workover method involving at least one of a tongs mechanism  132  and an upper trolley mechanism  98  above the tongs mechanism, the workover method comprising: 
     the tongs mechanism screwing together the tubing joint; 
     while screwing together the tubing joint via the tongs mechanism, the upper trolley mechanism stabilizing  140  an upper tube end of the tube; 
     during a first period, the upper trolley mechanism partially screwing  114  together the rod joint; and 
     during a second period following the first period, the tongs mechanism finishing screwing together the rod joint. 
     (22) Brush-clean Box End, Lube Pin End 
     Some example embodiments include a workover system for the handling and treating a well string member  64  or  66  that includes internal threads and external threads, the workover system being operable at a wellbore  14  that defines a longitudinal centerline  84 , the workover system comprising: 
     a workover vehicle having a storage rack area  72  or  74 ; 
     a robot system attached to the workover vehicle, the robot system  36  and  90  transferring the well string member between the storage rack area and the longitudinal centerline of the wellbore such that the internal threads travel along an upper path and the external threads travel along a lower path; 
     a powered cleaner  146  proximate the upper path; and 
     a powered lubricator  148  proximate the lower path. 
     (23) Overall Logic Sequence: POOH/RIH Simultaneous with Rack Transfer 
     Some example embodiments include a workover method  150  for removing a well string from a wellbore, wherein the well string includes an upper well string member and a lower well string member, the wellbore defines a longitudinal centerline, the workover method involving the use of a workover vehicle that includes at least one of a tongs mechanism, a mast, a work area, a storage rack, a main trolley with an elevator, an upper trolley mechanism, a robotic system with an end effector, and a robotic jib, the workover method comprising: 
     aligning the work area of the workover vehicle with the longitudinal centerline of the wellbore; 
     the tongs mechanism unscrewing the upper well string member from the lower well string member concurrently with the main trolley descending; 
     the tongs mechanism unscrewing the upper well string member from the lower well string member concurrently with the upper trolley mechanism stabilizing the upper well string member; 
     the end effector taking the upper well string member from the upper trolley mechanism; 
     the robotic system transferring the upper well string member to the storage rack; and 
     the elevator lifting the well string concurrently with the end effector translating in a lateral direction that is perpendicular to the longitudinal centerline of the wellbore. 
     With reference to  FIGS. 61 ,  61 A,  61 C,  61 D and particularly the far left blocks of  FIGS. 61 and 61A , “Rods POOH” means rods pulling out of hole, i.e., removing sucker rods. “Upper Trolley Gripper” refers to upper trolley mechanism  98 . “Cylinder A+B” refers to the actuators for raising and lowering main trolley  156 , wherein “extending” corresponds to lifting main trolley  156 , and “lowering” corresponds to main trolley  156  descending. “Elevator Jaws” refers to the elevator head  106 , wherein “closed” means elevator head  106  is configured and positioned to capture the upper end of a shaft, and “open” means elevator head  106  is retracted and configured to release the shaft&#39;s upper end. “Rod Tongs” refers to tongs mechanism  132 , wherein “extend” corresponds to arrow  232  ( FIG. 85A ) and “retracting” corresponds to arrow  246  ( FIG. 87A ). “Tubing Arm” refers to arm assembly  158  of upper robot  90 . “Lower Arm” refers to arm assembly  164  of lower robot  36 . “Wellhead Slips” refers to wellhead slip  110 . 
     With reference to  FIGS. 62 ,  62 A,  62 C,  62 D and particularly the far left blocks of  FIGS. 62 and 62A , “Rods RIH” means rods running in hole, i.e., installing sucker rods. “UTG” refers to upper trolley mechanism  98 . “Cylinder A  30 ” refers to the actuator for raising and lowering main trolley  156 , wherein Cylinder-A extending corresponds to lifting main trolley  156 , and Cylinder-A lowering corresponds to main trolley  156  descending. “Elevator Jaws” refers to the elevator head  106 , wherein “closed” means elevator head  106  is configured and positioned to capture the upper end of a shaft, and “open” means elevator head  106  is retracted and configured to release the shaft&#39;s upper end. “Rod Tongs” refers to tongs mechanism  132 , wherein “extend” corresponds to arrow  232  ( FIG. 85A ) and “retracting” corresponds to arrow  246  ( FIG. 87A ). “Cleaning Lubrication Station” refers to cleaning or lubricating the upper and lower ends of a shaft. “Tubing Arm” refers to arm assembly  158  of upper robot  90 . “Lower Arm” refers to arm assembly  164  of lower robot  36 . “Wellhead Slips” refers to wellhead slip  110 . 
     With reference to  FIGS. 63 ,  63 A,  63 B,  63 C and particularly to the far left blocks in  FIGS. 63 and 63A , “Tubing POOH” means tubing pulling out of hole, i.e., removing tubing. “Upper Trolley Gripper” refers to upper trolley mechanism  98 . “Cylinder A  30 ” refers to the actuator for raising and lowering main trolley  156 , wherein Cylinder-A extending corresponds to lifting main trolley  156 , and Cylinder-A lowering corresponds to main trolley  156  descending. “Elevator Jaws” refers to the elevator head  106 , wherein “closed” means elevator head  106  is configured and positioned to capture the upper end of a shaft, and “open” means elevator head  106  is retracted and configured to release the shaft&#39;s upper end. “Tubing Tongs” refers to tongs mechanism  132 , wherein “extend” corresponds to arrow  232  ( FIG. 85A ) and “retracting” corresponds to arrow  246  ( FIG. 87A ). “Tubing Arm” refers to arm assembly  158  of upper robot  90 . “Lower Arm” refers to arm assembly  164  of lower robot  36 . “Wellhead Slips” refers to wellhead slip  110 . 
     With reference to  FIGS. 64 ,  64 A,  64 C,  64 D and particularly the far left blocks of  FIG. 64A , “Tubing RIH” means tubing running in hole, i.e., installing tubing. “UTG” refers to upper trolley mechanism  98 . “Cylinder A  30 ” refers to the actuator for raising and lowering main trolley  156 , wherein Cylinder-A extending corresponds to lifting main trolley  156 , and Cylinder-A lowering corresponds to main trolley  156  descending. “Elevator Jaws” refers to the elevator head  106 , wherein “closed” means elevator head  106  is configured and positioned to capture the upper end of a shaft, and “open” means elevator head  106  is retracted and configured to release the shaft&#39;s upper end. “Tubing Tongs” refers to tongs mechanism  132 , wherein “extend” corresponds to arrow  232  ( FIG. 85A ) and “retracting” corresponds to arrow  246  ( FIG. 87A ). “Doping/Cleaning Station” refers to cleaning of the upper and lower ends of a shaft. “Tubing Arm” refers to arm assembly  158  of upper robot  90 . “Lower Arm” refers to arm assembly  164  of lower robot  36 . “Wellhead Slips” refers to wellhead slip  110 . 
     (24) Hero Valve 
     Some example embodiments include a workover system for servicing a well that includes a tubular well string with an upper shoulder, the tubular well string defining a fluid passageway therethrough, the workover system comprising: 
     a mast; 
     a main trolley mounted for vertical movement along the mast; 
     an elevator carried by the main trolley, the elevator comprising a shoulder engaging surface being moveable selectively to an operating mode and a relocating mode, the shoulder engaging surface engaging the upper shoulder when the elevator is in the operating mode, and the shoulder engaging surface being spaced apart from the upper shoulder when the elevator is in the relocating mode; and 
     a hero valve carried by the main trolley, the hero valve being movable by the main trolley selectively to a clear position and a deployed position, the hero valve in the clear position being spaced apart from the tubular well string, and the hero valve in the deployed position engaging the tubular well string and obstructing the fluid passageway. 
     Although the invention is described with respect to a preferred embodiment, modifications thereto will be apparent to those of ordinary skill in the art. The scope of the invention, therefore, is to be determined by reference to the following claims:

Summary:
An example robotic method for disassembling and removing a well string (e.g., a string of sucker rods or tubing within a wellbore) involves a computer controlled track and trolley system. Movement of multiple trolleys, carriages, shuttles, articulated arms and other hardware is orchestrated in a manner that minimizes cycle time and thus reduces the overall time for removing the entire well string. In some examples, upper and lower robots travel along and share a first set of tracks while an upper trolley mechanism and a main trolley travel along and share a second set of tracks. In some examples, the two sets of tracks are mounted vertically to a mast, wherein the mast is part of a workover vehicle.