Patent Publication Number: US-2023162889-A1

Title: Radial and axial interface between conductor rod and work machine

Description:
TECHNICAL FIELD 
     The present disclosure relates to a radial and axial interface between a conductive rod and a work machine. More specifically, the present disclosure relates to a conductive rod having electrical connectors positioned radially and pneumatic connectors positioned axially for interfacing with a work machine, and to an electrically powered work machine coupled electrically and pneumatically to the conductive rod. 
     BACKGROUND 
     Heavy work machines, such as earth-moving vehicles or hauling trucks, require significant power to carry out their functions. The machines themselves can be of substantial weight, and their loads require large amounts of power to move. Diesel engines typically provide that power, but they can have disadvantages. For instance, in some implementations, heavy work machines may need to travel large distances through rugged terrain. At a remote mining site, for example, groups of these machines are often employed to ferry extreme loads along roadways, or haul routes, extending between various locations within the mining site. Supplies of diesel fuel may be far away from such locations or not easily delivered to such locations. In addition, the groups of diesel machines can generate significant pollution. 
     Electrical power has been used to supplement these diesel engines while the work machines move. In some environments, the electrical power is delivered from wires over the haul route to a pantograph on the work machine as the machine travels the haul route, as in a cable car. But overhead wires cannot reliably provide sufficient electrical energy to power a heavy work machine during long movements. Nor can the overhead delivery provide enough current to charge backup batteries for an electric machine at the same time. As a result, electrical power through overhead wires typically supplements, rather than replaces, diesel engines in heavy work machines. 
     Alternatively, a power rail based on the ground may provide electrical power to heavy work machines. An axially moveable cylindrical rod includes at one end an interface with the work machine and at an opposite end a connection with the power rail at the side of a haul route, for example. In some situations, the interface with the work machine not only provides electrical power from the rod to the work machine, but also passes pressurized air from the work machine into the rod for energizing pneumatic controls. In addition, signaling data may need to be passed between the rod and the work machine for electrical sensors or controls. Accommodating these interfaces in a cylindrical rod handling high-voltage electrical power can be challenging. 
     One approach for providing electrical power through a rod to a traveling vehicle is described in International Patent App. Pub. No. WO 2009/007879A2 (“the &#39;879 application”). The &#39;879 application describes a hybrid transport system in which a rechargeable hybrid vehicle, in some embodiments, has contactors made of round or rectangular tubes that can extend from either side of the vehicle to connect with a metal strip along a roadside providing electrical power. While the contactors can be maneuvered with hydraulic or pneumatic cylinders, the cylinders are distinct from the contactors and can cause the contactors to pivot outwardly from the vehicle about axles. As a result, the contactors described in the &#39;879 application are prone to disconnection from the roadside metal strips, thereby causing temporary interruptions in the flow of electrical power from the metal strips to the vehicle. Such interruptions are undesirable, and may not be permissible in many worksite applications. In particular, the system of the &#39;879 application is not suited for use with machines, such as construction machines, mining machines, paving machines, and the like, requiring relatively high-voltage electrical power for propulsion and other functions. 
     Examples of the present disclosure are directed to overcoming deficiencies of such systems. 
     SUMMARY 
     In an aspect of the present disclosure, an apparatus for conducting electrical energy includes a rigid outer tube with a first end, a second end, an outer diameter, and a longitudinal center defining an axis between the first end and the second end. A first conductor within the rigid outer tube includes a first metal tube surrounding and extending along the axis from proximate the first end to the first metallic endplate and a first metallic endplate having a first longitudinal thickness extending orthogonally from the first metal tube to the outer diameter. A second conductor includes a second metal tube concentrically surrounding and separated from the first metal tube by an annular space and a second metallic endplate. The second metal tube extends from proximate the first end to the second metallic endplate, while the second metallic endplate has a second longitudinal thickness extending orthogonally from the second metal tube to the outer diameter. The second metallic endplate is farther from the second end than the first metallic endplate. 
     In another aspect of the present disclosure, a conductor assembly includes a first conductor and a second conductor. The first conductor includes a first conductive tube and a first conductive annulus, where the first conductive tube surrounds and extends along a longitudinal axis from a distal end to the first conductive annulus and the first conductive annulus has a first longitudinal thickness extending radially from the first conductive tube to an outer diameter. The second conductor includes a second conductive tube and a second conductive annulus, where the second conductive tube is concentrically inside the first conductive tube and extends from the distal end to the second conductive annulus. The second conductive annulus has a second longitudinal thickness extending radially from the second conductive tube to the outer diameter, and the second conductive annulus is farther from the distal end than the first conductive annulus. 
     In yet another aspect of the present disclosure, a work machine includes an electric engine, a battery, traction devices configured to cause movement of the work machine when powered by the electric engine, and a conductor rod having a first end and second end and configured to convey electrical energy to the work machine during the movement of the work machine. The conductor rod has a rigid outer tube with an outer diameter and a longitudinal center defining an axis between the first end and the second end. The conductor rod further includes tubular conductors, successively arranged concentrically around the axis and separated, at least in part, by air, and metallic rings. The metallic rings are attached respectively to terminations of the tubular conductors proximate the first end, and individual ones of the metallic rings extend orthogonally from corresponding ones of the tubular conductors to the outer diameter and are spaced apart along the axis. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    illustrates an isometric view of a work machine within an XYZ coordinate system as one example suitable for carrying out the principles discussed in the present disclosure. 
         FIG.  2    illustrates a longitudinal section of a conductor rod with an arm disposed in a barrel, in accordance with one or more examples of the present disclosure. 
         FIG.  3    is a longitudinal cross-sectional view of a conductor rod and a connector assembly, in accordance with one or more examples of the present disclosure. 
         FIG.  4    is an isometric view of a head-end interface having multiple tiers, in accordance with one or more examples of the present disclosure. 
         FIG.  5    is an isometric cross-sectional view of a portion of a conductor rod with head-end interface, along the cut lines shown in  FIG.  4   , in accordance with one or more examples of the present disclosure. 
         FIG.  6    is a flowchart depicting a method of powering a work machine from a moveable conductor rod using multi-tier head-end interface, in accordance with one or more examples of the present disclosure. 
         FIG.  7    is a partial isometric rear view of a conductive rod and head-end interface in accordance with an example of the present disclosure. 
         FIG.  8    is an isometric view of a longitudinal section of the conductive rod and connector of  FIG.  8    in accordance with an example of the present disclosure. 
         FIG.  9    is a flowchart depicting a method of powering a work machine from a moveable conductive rod in accordance with an example of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Wherever possible, the same reference numbers will be used throughout the drawings to refer to same or like parts.  FIG.  1    illustrates an isometric view of a work machine  100  within an XYZ coordinate system as one example suitable for carrying out the principles discussed in the present disclosure. The exemplary work machine  100  travels parallel to the X axis along a roadway, also termed a haul route  101 , typically from a source to a destination within a worksite. In one implementation as illustrated, work machine  100  is a hauling machine that hauls a load within or from a worksite within a mining operation. For instance, the work machine  100  may haul excavated ore or other earthen materials from an excavation area along haul route  101  to dump sites and then return to the excavation area. In this arrangement, work machine  100  may be one of many similar machines configured to ferry earthen material in a trolley arrangement. While a large mining truck in this instance, work machine  100  may be any machine that carries a load between different locations within a worksite, examples of which include an articulated truck, an off-highway truck, an on-highway dump truck, a wheel tractor scraper, or any other similar machine. Alternatively, work machine  100  may be an off-highway truck, on-highway truck, a dump truck, an articulated truck, a loader, an excavator, a pipe layer, or a motor grader. In other implementations, work machine  100  need not haul a load and may be any machine associated with various industrial applications including, but not limited to, mining, agriculture, forestry, construction, and other industrial applications. 
     Referring to  FIG.  1   , an example work machine  100  includes a frame  103  powered by electric engine  102  to cause rotation of traction devices  104 . Traction devices  104  are typically four or more wheels with tires, although tracks or other mechanisms for engagement with the ground along haul route  101  are possible. Electric engine  102  functions to provide mechanical energy to work machine  100  based on an external electrical power source, such as described in further detail below. An example of mechanical energy provided by electric engine  102  includes propelling traction devices  104  to cause movement of work machine  100  along haul route  101 , but electric engine  102  also includes components sufficient to power other affiliated operations within work machine  100 . For instance, in some implementations, electric engine  102  includes equipment for converting electrical energy to provide pneumatic or hydraulic actions within work machine  100 . While electric engine  102  is configured to operate from an external electrical power source, electric engine  102  typically includes one or more batteries for storing electrical energy for auxiliary or backup operations. 
     In accordance with the principles of the present disclosure, and relevant to the presently disclosed subject matter, the work machine  100  further includes a conductor rod  106  configured to receive electrical power from a power rail  108 . In some examples, power rail  108  is one or more beams of metal arranged substantially parallel to and a distance above the ground. In  FIG.  1   , power rail  108  is positioned to be substantially parallel to the X axis and the direction of travel of work machine  100 . Support mechanisms hold power rail  108  in place along a distance at the side of haul route  101  for work machine  100  to traverse. The support mechanisms and power rail  108  may be modular in construction, enabling their disassembly and reassembly at different locations or their repositioning along the existing haul route  101 . Moreover, while shown in  FIG.  1    to the left of work machine  100  from the perspective of an operator sitting in the cab of the work machine  100 , power rail  108  may be disposed to the right of work machine  100  or in other locations suitable to the particular implementation. 
     Power rail  108  provides a source of electrical power for work machine  100  as either AC or DC. In some examples, power rail  108  has two or more conductors, each providing voltage and current at a different electrical pole. In one implementation (e.g., an implementation in which the power rail  108  includes three conductors), one conductor provides positive DC voltage, a second conductor provides negative DC voltage, and a third conductor provides 0 volts relative to the other two conductors. The two powered conductors within power rail  108  provide +1500 VDC and −1500 VDC. These values are exemplary, and other physical and electrical configurations for power rail  108  are available and within the knowledge of those of ordinary skill in the art Further, it should be understood that the voltages described herein are merely exemplary, as various levels of AC voltage may be used, as well as a combination of AC and DC voltages, depending on the particular configuration. 
     Conductor rod  106  enables electrical connection between work machine  100  and power rail  108 , including during movement of work machine  100  along haul route  101 . In the example shown in  FIG.  1   , conductor rod  106  is an elongated arm resembling a pole.  FIG.  1    shows conductor rod  106  positioned along a front side of work machine  100 , with respect to the direction of travel of work machine  100  in the direction of the X axis. In this arrangement, conductor rod  106  is located in  FIG.  1    in the Y-Z plane essentially along the Y axis with a first end  107  near a right side of work machine  100  and a second end  111  at a left side of work machine  100 . Conductor rod  106  may be attached to any convenient location within work machine  100 , such as to frame  103 , in a manner to couple conductor rod  106  to power rail  108 . Shown in  FIG.  1    as extending to a left side of work machine  100  toward power rail  108 , conductor rod  106  may alternatively be arranged to extend to a right side and at any desired angle from work machine  100  such that conductor rod  106  may be coupled to power rail  108  for obtaining electrical power. 
     As embodied in  FIG.  1   , conductor rod  106  includes a barrel  109  mounted to frame  103  of work machine  100 . Barrel  109  has a hollow interior and may be a conductive metal having suitable mechanical strength and resiliency, such as aluminum. Within barrel  109 , an arm  110  is retained. Arm  110  is engaged within conductor rod  106  along the Y axis in  FIG.  1   . A length of conductor rod  106  roughly spans the width of work machine  100 . A junction  112  serves as the junction or interface between arm  110  and barrel  109 , which is the main body of conductor rod  106 . When arm  110  is fully retracted or collapsed into barrel  109 , junction  112  essentially becomes the left edge of conductor rod  106 . On the other hand, when arm  110  is extended from barrel  109  of conductor rod  106 , arm  110  may reach from work machine  100  to proximate power rail  108  on the side of haul route  101 . 
     Within, and possibly including barrel  109 , conductor rod  106  includes a series of electrical conductors passing longitudinally, at least from a head  122  at a proximal end of the conductor rod  106  to a tip  124  at a distal end of the conductor rod  106 . Typically, the conductors within conductor rod  106  are formed of a metallic material and are rigid. In some examples, the conductors are concentric tubes, or hollow cylinders, of solid metal such as copper, aluminum, gold, silver, nickel, zinc, or alloys thereof nested together and sized to provide electrical capacity sufficient for powering work machine  100 . Other conductive materials may be used, such as graphite, and are considered to be within the scope of the presently disclosed subject matter. Tubular conductors within arm  110  engage with corresponding tubular conductors within barrel  109  to provide for electrical continuity. In other examples, one or more concentric copper tubes, rather than aluminum, of varying diameters may be used as tubular conductors. Other types of conductive tubes may be used and are within the scope of the presently disclosed subject matter. 
     At tip  124 , a connector assembly  114  provides an interface to power rail  108  via trailing arms  116  and contactor  118 . Power rail  108  is typically arranged along a side of haul route  101 , and work machine  100  is steered so that it traverses haul route  101  substantially in parallel with power rail  108 . Thus, in reference to  FIG.  1   , power rail  108  and a travel path for work machine  100  are substantially in parallel with each other and with the X axis. Contactor  118  is configured to maintain an electrical connection with power rail  108  while sliding along its surface in the direction of the X axis as work machine  100  moves. In some examples, trailing arms  116  are conductors coupled to contactor  118 , each conducting voltage and current at a different electrical pole and corresponding to the conductors within conductor rod  106 . In operation, electrical power is accessed from power rail  108  via contactor  118 , which remain in contact during movement of work machine  100 , and the electrical power is conducted through trailing arms  116  into connector assembly  114 . 
     From connector assembly  114 , the electrical power is conveyed at tip  124  through the nested tubular conductors within arm  110  and barrel  109  to head  122  of conductor rod  106  and through a head-end interface  120  to work machine  100 . Head-end interface  120  provides at least an electrical connection between conductor rod  106  and work machine  100  for powering electric engine  102  and otherwise enabling operations within work machine  100 . In some examples, head-end interface  120  may also provide an interface for inputs to control mechanical operation of conductor rod  106 . 
     As noted above, the tubular or cylindrical nature of conductor rod  106 , lending to a degree of rigidity greater than a solid conductor of similar or smaller mass or weight to conductor rod  106  due to a larger moment of inertia of a hollow tube than a solid rod of similar mass. Thus, by forming the conductive material into a hollow tube rather than a solid rod, for similar conductive performance, conductor rod  106  can provide a mechanism to conduct electrical power from a source to a load over an unsupported distance. As described above, trailing arms  116  are conductors coupled to contactor  118 , each conducting voltage and current at a different electrical pole and corresponding to the conductors within conductor rod  106 . Different cylindrical conductors within conducting rod  106  can provide for the transmission of different potentials along conducting rod  106 , illustrated in more detail in  FIG.  2   , below. 
       FIG.  2    illustrates a longitudinal cross-section of a section of conductor rod  106  with arm  110  disposed in barrel  109 , in accordance with one or more examples of the present disclosure. More specifically,  FIG.  2    depicts a longitudinal cross-section of a section of conductor rod  106  between head-end interface  120  and connector assembly  114 , from head  122  to tip  124 , when viewed facing in the direction of travel for work machine  100 , i.e., in the direction of the X axis along . Thus, conductor rod  106  lies in the Y-Z plane, as indicated in  FIG.  2   . 
     Referring to the right side of  FIG.  2   , barrel  109  contains an arrangement of concentric conductors of tubular shape, i.e., as hollow cylinders. In this example, from an axial center AB outward, first cylinder conductor  202  is positioned concentrically along axial center AB (i.e. the longitudinal axis of barrel  109 ) of barrel  109  and is a tubular conductor made of aluminum or a similar metal with high electrical conductivity and high mechanical strength. For instance, an aluminum alloy such as 6061-T6 may be used for first cylinder conductor  202  and other conductive tubes in conductor rod  106 . Other suitable metals or alloys thereof may be used and are considered to be within the scope of the presently disclosed subject matter. In some examples, first cylinder conductor  202  has an outer diameter of approximately 3.5 inches to 4.5 inches. However, it should be understood that dimensions provided herein are merely for purposes of illustration and are not intended to be limitations, as dimensions described in relation to various components may be greater or less than the examples provided herein. First cylinder conductor  202  begins at head  122  and extends axially along conductor rod  106  around axial center AB to a barrel end  205 . As a tube, first cylinder conductor  202  defines first cylinder cavity  204  within inner surface  207  of first cylinder conductor  202 . If arm  110  were removed from barrel  109  in  FIG.  2   , first cylinder cavity  204  would be an open space within first cylinder conductor  202  from head  122  to barrel end  205 . In one example, first cylinder cavity  204  has a diameter of about 2.5 to 3 inches. 
     A second cylinder conductor  206  is positioned concentrically along axial center AB and surrounds first cylinder conductor  202 . As with first cylinder conductor  202 , second cylinder conductor  206  is a tubular conductor made of aluminum or a similar metal with high electrical conductivity and high mechanical strength. Second cylinder conductor  206  is similarly positioned around a Y axis within  FIG.  2    and spans a distance from head  122  to barrel end  205 . In one example, second cylinder conductor  206  has an outer diameter of about 5 inches to 5.5 inches. These dimensions, as well as other dimensions discussed below, are merely examples and could be greater or lesser than the stated values. Being arranged concentrically around and, by definition, having a larger diameter than first cylinder conductor  202 , second cylinder conductor  206  forms a radial gap between it and first cylinder conductor  202 . In the example of  FIG.  2   , that gap is filled by second cylinder insulation  208 , which is an insulation comprised of a closed cell polyurethane foam. Other types of materials for second cylinder insulation  208  that provide electrical insulation and lightweight support within conductor rod  106  will be available and apparent to those of ordinary skill in the field. In some examples, second cylinder insulation  208  has a thickness of about 1.5 inches to 0.75 inches. 
     In some examples, second cylinder insulation  208  can be a dielectric. Dielectric materials can be solids, liquids, or gases. Some solids can be used as dielectrics, such as porcelain, glass, plastics, and the closed cell polyurethane foam described above. In configurations in which a cylinder conductor or piston conductor is hermetically sealed on both ends of the cylinder conductor or piston conductor, fluidic dielectrics can be used in gaps, such as radial gap first cylinder conductor  202  and second cylinder conductor  206 . Fluid dielectrics can include some forms of oil or gaseous dielectrics such as air, nitrogen, helium, and other dry gases such as sulfur hexafluoride. In further configurations in which a cylinder conductor or piston conductor is hermetically sealed on both ends of the cylinder conductor or piston conductor, a partial vacuum can be used. In various examples, a partial vacuum can be used as a nearly lossless dielectric even though its relative dielectric constant is unity. It should be noted that the dielectrics disclosed herein are merely examples, as other dielectrics may be used and are considered to be within the scope of the presently disclosed subject matter. Different dielectrics can be used in various radial gaps of conductor rod  106  to allow for different voltages and different types of potentials to be conducted by conductor rod  106 . A partial vacuum can be created by pulling air from within a conductor rod, such as from within a cavity, explained in more detail in  FIG.  7   . 
     Moving farther out radially on the right side of  FIG.  2   , third cylinder conductor  210  is positioned concentrically along axial center AB and surrounds second cylinder conductor  206  and first cylinder conductor  202 . Third cylinder conductor  210  is a tubular conductor made of aluminum or a similar metal with high electrical conductivity and high mechanical strength. As with the other tubes discussed, third cylinder conductor  210  extends from head  122  to barrel end  205  within conductor rod  106 . In one example, third cylinder conductor  210  has an outer diameter of about 8 to 9 inches. A third cylinder cavity  212  between second cylinder conductor  206  and third cylinder conductor  210  is an open space, which, if arm  110  were removed from barrel  109  in  FIG.  2   , would form a tubular cavity extending from head  122  to barrel end  205 . 
     Concentrically along axial center AB and around third cylinder conductor  210  and the other tubular conductors, fourth cylinder conductor  214  forms an outer conductive path from head  122  to barrel end  205 . Similarly, fourth cylinder conductor  214  is a tubular conductor made of an aluminum alloy or a similar metal with high electrical conductivity and high mechanical strength. In one example, fourth cylinder conductor  214  has an outer diameter of about 14 inches. A gap  215  defined as a space between outer surface  217  of third cylinder conductor  210  and an inner surface  219  of fourth cylinder conductor  214 , in some examples, is about 0.75 inches and is filled with fourth cylinder insulation  216 , which is a closed cell polyurethane foam, dielectric, or similar substance. 
     Radially beyond fourth cylinder conductor  214 , a covering or barrel shell  218  encases conductor rod  106 . Barrel shell  218  is typically a metal or similar substance providing structural integrity to conductor rod  106 . Barrel shell  218  has an inner diameter in excess of an outer diameter of fourth cylinder conductor  214 . As a result, a retraction cavity  220  of a tubular shape is formed between fourth cylinder conductor  214  and barrel shell  218  that extends from head  122  to barrel end  205 . A stop  222 , which is part of a housing for conductor rod  106  at junction  112 , defines a longitudinal end for retraction cavity  220  away from head  122 . 
     The various annular or tubular cavities within barrel  109 , namely, first cylinder cavity  204 , third cylinder cavity  212 , and the head end of retraction cavity  220  (barrel shell cavity  242 , described below), are sealed or capped by the attachment of head-end interface  120  to their ends at head  122 . The attachment of head-end interface  120  is designed to provide an airtight (or hermetic) seal within these cavities, for purposes to be understood further below. 
     Viewing  FIGS.  1  and  2    together, arm  110  is a substantially cylindrical body having an outer diameter D 1  that is smaller than inner diameter D 2  of barrel shell  218 , allowing arm  110  to slidable engage into barrel  109 . As well as providing a longitudinal end for retraction cavity  220 , stop  222  also defines an inner diameter D 3  through which arm  110  slides, as shown to the left of  FIG.  2   . By sliding, it is meant that arm  110  may move longitudinally along the Y axis within barrel  109  as arm  110  is moved axially with respect to conductor rod  106 , from left to right in  FIG.  2    for retraction and from right to left in  FIG.  2    for extension. The result of the sliding is the increase or decrease in the overall length of conductor rod  106  via arm  110 , as illustrated in  FIG.  1   . 
     Referring now to the left side of  FIG.  2   , arm  110  also contains a series of concentric conductors of cylindrical or tubular shape. In this example, from the axial center outward, first piston conductor  224  is positioned at a center of arm  110  and is, as with the other tubular conductors of arm  110 , made of a metal such as aluminum 6061-T6 or similar substance having high electrical conductivity and high mechanical strength. First piston conductor  224  extends from tip  124  to an arm end  225 , shown at the right side of  FIG.  2   . Being tubular, first piston conductor  224  has a first piston cavity  226  within its inner diameter that is filled with air or another gas. A second piston conductor  228  concentrically surrounds first piston conductor  224  and extends from tip  124  to arm end  225 . Second piston conductor  228  is made of a conductive material, and in some examples has an inner diameter of between about 5 and 6 inches. A space defined as second piston cavity  230  is formed between the inner diameter of second piston conductor  228  and the outer diameter of first piston conductor  224 , which is left unfilled other than with air or a similar gas. 
     Moving radially outward from second piston conductor  228 , a third piston conductor  232  axially centered on the Y axis concentrically surrounds second piston conductor  228 . Similarly made of a conductive material, third piston conductor  232  is set off radially from second piston conductor  228  a distance of less than 1 inch, which is filled with a third piston insulation  234 . As with second cylinder insulation  208  and fourth cylinder insulation  216 , third piston insulation  234  can be a closed cell polyurethane foam or comparable substance providing electrical insulation and lightweight stability. An arm shell  236  of conductive material such as metal concentrically surrounds third piston conductor  232  from tip  124  to about arm end  225 . In some examples, arm shell  236  has an outer diameter of about 11.625 inches. Within an inner diameter of arm shell  236 , an arm shell cavity  238  of free space exists between arm shell  236  and third piston conductor  232 . 
     In some examples, the outer surface of arm shell  236  includes gasket  240 , which serves to stably set apart arm shell  236 , and arm  110  generally, from barrel shell  218 . As illustrated in  FIG.  2   , as arm  110  is retracted or extended within barrel  109 , gasket  240  separates retraction cavity  220  from a barrel shell cavity  242 . As well, gasket  240  can help retain arm  110  within conductor rod  106  in a state of maximum extension by butting against stop  222 . 
     As illustrated,  FIG.  2    represents an arrangement in which conductor rod  106  essentially has two longitudinal halves. It should be noted, however, that a conductor rod of the presently disclosure does not require multiple halves, illustrated in  FIG.  3   , below. Returning to  FIG.  2   , a first half, barrel  109 , on the right side of  FIG.  2   , includes barrel shell  218  enclosing a series of tubular cylinder conductors aligned along the Y axis. Those cylinder conductors, viewed radially from axial center AB, are first cylinder conductor  202 , second cylinder conductor  206 , third cylinder conductor  210 , and fourth cylinder conductor  214 . Within that concentric arrangement, tubular regions of open space exist within first cylinder cavity  204  and third cylinder cavity  212 . Further, barrel shell  218  encases barrel  109  and forms an open space  244  within retraction cavity  220  and barrel shell cavity  242 . On the left side of  FIG.  2   , arm  110  includes arm shell  236  enclosing a series of tubular piston conductors also aligned along axial center AB of conductor rod  106 . Those piston conductors, viewed radially from axial center AB, are first piston conductor  224 , second piston conductor  228 , and third piston conductor  232 . Within that concentric arrangement, tubular regions of open space exist within first piston cavity  226  and second piston cavity  230 . Further arm shell  236  encases arm  110  and forms an open space  246  within arm shell cavity  238 . 
     In an operating state for conductor rod  106 , arm  110  is inserted into barrel  109  to form a nested configuration of the piston conductors and the cylinder conductors. For example, when arm  110  is inserted into barrel  109 , the outer surface  227  of first piston conductor  224  fits within an internal space formed by an inner surface  229  of first cylinder conductor  202 . During operation, first piston conductor  224  maintains electrical contact with first cylinder conductor  202 , permitting electrical conductivity between those tubular conductors. When first piston conductor  224  is mated within first cylinder conductor  202 , first piston cavity  226  and first cylinder cavity  204  connectively extend axially through conductor rod  106  from head  122  to tip  124 . 
     Similarly, when the combination of second piston conductor  228 , third piston conductor  232 , and interposed third piston insulation  234  are slid as part of arm  110  into barrel  109 , an outer surface  231  of third piston conductor  232  fits within an inner surface  233  of third cylinder conductor  210 , and an inner surface  235  of second piston conductor  228  fits over an outer surface  237  of second cylinder conductor  206 . As a result, second piston conductor  228 , third piston conductor  232 , and third piston insulation  234  are disposed in the empty space defined by third cylinder cavity  212 . In this configuration, third piston conductor  232  electrically contacts third cylinder conductor  210 , and second piston conductor  228  electrically contacts second cylinder conductor  206 . In some examples, and as shown similarly in  FIG.  2   , when conductor rod  106  is fully collapsed, at least some volume of empty space will remain within third cylinder cavity  212 , which will have an annular or tubular shape and be defined radially by portions of second cylinder conductor  206  and third cylinder conductor  210 . 
     Conversely, when arm  110  is inserted into barrel  109 , the cylinder conductors will be disposed within cavities within the piston from left to right in  FIG.  2   , and the cylinder conductors are nested with the piston conductors. For example, the combination of first cylinder conductor  202 , second cylinder conductor  206 , and second cylinder insulation  208  are in the open space defined by second piston cavity  230  within arm  110 , during which, as mentioned, first cylinder conductor  202  electrically contacts first piston conductor  224  and second cylinder conductor  206  electrically contacts second piston conductor  228 . Likewise, in the illustrated example, the sandwich of third cylinder conductor  210 , fourth cylinder conductor  214 , and fourth cylinder insulation  216  are in the open space defined by arm shell cavity  238  within arm  110 . Third cylinder conductor  210  will contact third piston conductor  232 , and fourth cylinder conductor  214  will do the same against arm shell  236 . 
     As mentioned above, head-end interface  120  provides at least an electrical connection between conductor rod  106  and work machine  100  for powering electric engine  102  and otherwise enabling operations within work machine  100 . Head-end interface  120  also provides the physical securement of first cylinder conductor  202 , second cylinder conductor  206 , third cylinder conductor  210 , and fourth cylinder conductor  214  to work machine  100 , allowing arm  110  to extend and retract in relation to conductor rod  106 , illustrated in more detail in  FIGS.  3  and  4   , below. 
       FIG.  3    is a longitudinal cross-sectional view of a conductor rod  300  on the side of a tip  324  proximate to connector assembly  312 , in accordance with one or more examples of the present disclosure. For purposes of simplicity, only the side of conductor rod  300  proximate to connector assembly  312  is illustrated, though the technologies and techniques described in  FIG.  3    and below are applicable to conductor rod  300  proximate to a head-end interface, such as head-end interface  120  of  FIGS.  1  and  2   .  FIG.  3    depicts a longitudinal cross-sectional of a portion of conductor rod  300  when viewed facing in the direction of travel for a work machine, such as work machine  100  of  FIG.  1   , i.e., in the direction of the X axis. Thus, conductor rod  300  lies in the Y-Z plane, as indicated in  FIG.  3   . Conductor rod  300  includes first cylinder conductor  302 , second cylinder conductor  304 , third cylinder conductor  306 , and barrel  308 . Conductor rod  300  includes connector assembly  312 . Similar to the conductor rod  106  of  FIG.  1   , connector assembly  312  is located proximate to a power supply to conduct power from the power supply to work machine  100  (or load). 
     First cylinder conductor  302 , second cylinder conductor  304 , and third cylinder conductor  306  are concentric conductors of tubular shape, i.e. as hollow cylinders. In  FIG.  3   , from axial center CD outward, first cylinder conductor  302  is positioned at a center of barrel  308 . Second cylinder conductor  304  concentrically surrounds first cylinder conductor  302 . As with first cylinder conductor  302 , second cylinder conductor  304  is a tubular conductor made of aluminum or a similar metal with high electrical conductivity and high mechanical strength. Second cylinder conductor  304  is similarly positioned concentrically around axial center CD. Moving farther out radially, third cylinder conductor  306  concentrically surrounds second cylinder conductor  304  and first cylinder conductor  302 . Concentrically around third cylinder conductor  306  and the other tubular conductors, barrel  308  forms an outer conductive path. In some examples, barrel  308  can act as a fourth cylinder conductor if constructed from a conductive material. First cylinder conductor  302 , second cylinder conductor  304 , third cylinder conductor  306 , and barrel  308  span a distance from head-end interface  310  to connector assembly  312 . Radially beyond fourth cylinder conductor  214 , barrel  308  encases conductor rod  300 . Barrel  308  is typically a metal or similar substance providing structural integrity to conductor rod  300 . However, in some examples, barrel  308  is a non-conductive material that isolations the electrically energized interior of conductor rod  300  from an environment. Barrel  308  has an inner diameter in excess of an outer diameter of fourth cylinder conductor  214 . 
     As tubes, first cylinder conductor  302  defines first cylinder cavity  314  within inner surface  315  of first cylinder conductor  302 , second cylinder conductor  304  defines second cylinder cavity  316  between inner surface  317  of second cylinder conductor  304  and outer surface  319  of first cylinder conductor  302 , third cylinder conductor  306  defines third cylinder cavity  318  between inner surface  321  of third cylinder conductor  306  and outer surface  323  of the second cylinder conductor  304 , and barrel  308  defines fourth cylinder cavity  320  between inner surface  325  of barrel  308  and outer surface  327  of the third cylinder conductor  306 . First cylinder cavity  314 , second cylinder cavity  316 , third cylinder cavity  318 , and/or fourth cylinder cavity  320  can be filled with insulative materials such as closed cell polyurethane foam. In other examples, first cylinder cavity  314 , second cylinder cavity  316 , third cylinder cavity  318 , and/or fourth cylinder cavity  320  are filled with a dielectric. Dielectric materials can be solids, liquids, or gases. Some solids can be used as dielectrics, such as porcelain, glass, plastics, and the closed cell polyurethane foam described above. In configurations in which a cylinder conductor is hermetically sealed on both ends of cylinder conductor  300 , fluidic dielectrics can be used in cavities, First cylinder cavity  314 , second cylinder cavity  316 , third cylinder cavity  318 , and/or fourth cylinder cavity  320 . Fluid dielectrics can include some forms of oil or gaseous dielectrics such as air, nitrogen, helium, and other dry gases such as sulfur hexafluoride. In further configurations in which a cylinder conductor or piston conductor is hermetically sealed on both ends of the cylinder conductor or piston conductor, a partial vacuum can be used. In various examples, a partial vacuum can be used as a nearly lossless dielectric even though its relative dielectric constant is unity. It should be noted that the dielectrics disclosed herein are merely examples, as other dielectrics may be used and are considered to be within the scope of the presently disclosed subject matter. 
     Different dielectrics can be used in various cylinder cavities of conductor rod  300  to allow for different voltages and different types of potentials to be conducted by conductor rod  300 . For example, first cylinder conductor  302  and second cylinder conductor  304  can be configured to conduct a DC voltage and third cylinder conductor  306  can be configured to conduct an AC voltage. Because both first cylinder conductor  302  and second cylinder conductor  304  are conducting DC voltage, there may be no need or requirement to have a dielectric other than air between first cylinder conductor  302  and second cylinder conductor  304 . However, if the AC voltage being carried on third cylinder conductor  306  is of a certain voltage level or frequency, a dielectric of suitable strength can be used to prevent a short between second cylinder conductor  304  and third cylinder conductor  306 . 
     The various annular or tubular cavities within barrel  308 , namely, first cylinder cavity  314 , second cylinder cavity  316 , third cylinder cavity  318 , and/or fourth cylinder cavity  320 , are sealed or capped by the attachment of the ends of the cylinder conductors to an interface. In  FIG.  3   , the interface is connector assembly  312 , though the same technology and techniques can be used to attach the other ends of cylinder conductors to another interfaces, such as head-end interface  120  of  FIG.  2   . The attachment is designed to provide an airtight (or hermetic) seal within these cavities. For example, when using fluidic insulative materials or dielectrics, or a partial vacuum, a hermetic seal maintains the fluid within the particular cavity to which the fluid is inserted, or, maintains the partial vacuum from which the air was pumped out. To provide for an airtight seal, the ends of the cylinder conductors can be affixed to interfaces using various technologies, including welding, glue, adhesive, gaskets, and the like. To removably affix the ends of the cylinder conductors, whereby the ends can be installed, removed, and reinstalled, the cylinder conductors can use a terminal connector assembly. The terminal connector assemblies use a threaded member inserted into a terminal receiver. The terminal receiver is affixed to a respective cylinder conductor, thereby providing for affixing and removing the cylinder conductors from either a head-end interface, such as head-end interface of  FIGS.  1  and  2   , or connector assembly  312 . 
     In  FIG.  3   , first cylinder conductor  302  is affixed to head-end interface  310  using terminal connector assembly  330  and threaded members  332 A and  332 B. Threaded members  332 A and  332 B are inserted through head-end interface  310  and into terminal connector assembly  330 . Second cylinder conductor  304  is affixed to head-end interface  310  using terminal connector assembly  360 A and  360 B and threaded members  346 A and  346 B. Threaded members  346 A and  346 B are inserted through head-end interface  310  and into terminal connector assembly  360 A and  360 B. Third cylinder conductor  306  is affixed to head-end interface  310  using terminal connector assembly  362 A and  362 B and threaded members  348 A and  348 B. Threaded members  348 A and  348 B are inserted through head-end interface  310  and into terminal connector assembly  362 A and  362 B. Barrel  308  is affixed to head-end interface  310  using terminal connector assembly  364 A and  364 B and threaded members  350 A and  350 B. Threaded members  350 A and  350 B are inserted through head-end interface  310  and into terminal connector assembly  364 A and  364 B. 
     In  FIG.  3   , threaded members  332 A/ 332 B,  346 A/ 346 B,  348 A/ 348 B, and/or  350 A/ 350 B are used to provide electrical power from their respective conductor cylinders to a load, such as work machine  100 . It is noted that threaded members  350 A and  350 B may provide electrical power or may be connected to a ground, such as work machine  100 . However, as illustrated in  FIG.  3   , threaded members  332 A/ 332 B,  346 A/ 346 B,  348 A/ 348 B, and/or  350 A/ 350 B are disposed substantially along the same plane or the Z axis. In some examples, however, threaded members may be disposed on different planes of a head-end connector, as illustrated by example in  FIG.  4   . 
       FIG.  4    is an isometric view of a head-end interface  400  having multiple tiers, in accordance with one or more examples of the present disclosure. Head-end interface  400  is within an XYZ coordinate system. Head-end interface  400  can be used as head-end interface  120  of  FIG.  1   . Head-end interface  400  may be constructed of various types of materials, including metals, ceramics, and plastic. If constructed of a metal, head-end interface  400  may be coated with an insulative material to prevent electrical shorts. Head-end interface  400  includes structural features that enable electrical connection with a conductor rod, such as conductor rod  300  of  FIG.  3   , using threaded members. Head-end interface  400  provides access for passing electrical power from a conductor rod to a work machine, such as work machine  100 . Head-end interface  400  is shown illustrated with threaded members  402 A and  402 B,  404 A and  404 B,  406 A and  406 B, and  408 A and  408 B. Threaded members  402 A and  402 ,  404 A and  404 B,  406 A and  406 B, and  408 A and  408 B are constructed in a manner similar to threaded members of  FIG.  3   . Threaded member  408 A is shown in  FIG.  4    as being partially extracted from head-end interface  400 . As illustrated in  FIG.  4   , load  437  can receive electrical power through electrical connector  434  connected to head-end interface  400  by threaded member  408 A. Load  437  can also receive electrical power through electrical connector  436 . In some examples, if threaded member  408 A is connected to a barrel or outer tube, rather than being connected to load  437 , electrical connector may be connected to a ground. 
     Head-end interface  400  includes one or more tiers, for example tiers  410 - 416 , that are disposed above each other longitudinally along the Z axis, which in  FIG.  4   , are generally circular in shape. Head-end interface  400  includes a central axis GT that extends through the center of head-end interface  400  in the direction of the Z axis. Tier  410  is defined by a substantially planar surface  418  extending substantially perpendicular to the central axis GT. The tier  410  also includes a riser section  420  extending substantially perpendicularly from the surface  418 . The riser section  420  comprises a substantially cylindrical outer wall of the tier  410 , and the central axis GT extends substantially centrally through the surface  418  and the riser section  420 . As shown in  FIG.  4   , the tier  410  has an axial height A as measured from the surface  418  to a substantially planar surface  422  of the tier  412 . In some examples, the height A of the tier  410  comprises an axial height of the substantially cylindrical riser section  420 . Tier  412  is defined by a substantially planar surface  422  extending substantially perpendicular to the central axis GT. The tier  410  also includes a riser section  424  extending substantially perpendicularly from the surface  422 . The riser section  424  comprises a substantially cylindrical outer wall of the tier  412 , and the central axis GT extends substantially centrally through the surface  422  and the riser section  424 . As shown in  FIG.  4   , the tier  412  has an axial height B as measured from the surface  422  to a substantially planar surface  426  of the tier  414 . In some examples, the height B of the tier  412  comprises an axial height of the substantially cylindrical riser section  424 . Tier  414  is defined by a substantially planar surface  426  extending substantially perpendicular to the central axis GT. The tier  414  also includes a riser section  428  extending substantially perpendicularly from the surface  426 . The riser section  428  comprises a substantially cylindrical outer wall of the tier  414 , and the central axis GT extends substantially centrally through the surface  426  and the riser section  428 . As shown in  FIG.  4   , the tier  414  has an axial height C as measured from the surface  426  to a substantially planar surface  430  of the tier  416 . In some examples, the height C of the tier  414  comprises an axial height of the substantially cylindrical riser section  428 . In some examples, height A, height B, and height C are substantially the same or similar. In other examples, height A, height B and/or height C can be different from each other. 
     Threaded members  402 A and  402  are located on tier  410 . Threaded members  404 A and  404 B are located on tier  412 . Threaded members  406 A and  406 B are located on tier  414 . Threaded members  408 A and  408 B are located on tier  416 . Head-end interface  400  is shown with bore  438 . Bore  438  is an annular space  439  in head-end interface  400  that extends through head-end interface  400  and provides an opening through head-end interface  400  into which fluids such as air may be introduced or removed. Bore  438  cylindrical structure extending substantially perpendicularly from surface  418  along axis GT,  438 . Bore  438  through annular space  439  is a channel extending substantially centrally through head-end interface  400  formed by the structure to some other location (not shown). For example, bore  438  may be used to deliver pressurized air within a conductor rod. In some examples, the pressurized air provides an axial force that can affect a movement of a conductor rod. 
     Head-end interface  400  provides for a multi-tier interface to which cylinder conductors may be affixed. Threaded members can be physically and electrically connected to respective conductive cylinders to transfer electrical energy received from a power source, through one or more piston conductors and cylinder conductors, and into their respective terminal connectors, illustrated by way of example in  FIG.  5   , which uses head-end interface  400  connected to conductor rod  300  of  FIG.  3   . 
       FIG.  5    is an isometric cross-sectional partial view of a conductor rod  500  with head-end interface  400  along the cut lines shown in  FIG.  4    revealing internal conductors, as discussed below, in accordance with one or more examples of the present disclosure. Head-end interface  400  is physically and electrically connected to conductor rod  300  of  FIG.  3   . Threaded members  402 A and  402 B are located on tier  410 . Threaded members  404 A and  404 B are located on tier  412 . Threaded members  406 A and  406 B are located on tier  414 . Threaded members  408 A and  408 B are located on tier  416 . Conductor rod  500  includes first cylinder conductor  502 , second cylinder conductor  504 , third cylinder conductor  506 , and barrel  508 . First cylinder conductor  502 , second cylinder conductor  504 , third cylinder conductor  506 , and barrel  508  are mechanically affixed to head-end interface  400 . Conductor rod  500  further includes first piston conductor  512 , second piston conductor  514 , third piston conductor  516 , and arm  518 . 
     In some examples, tier  416  has a diameter D 1  through axial length FG defined by the substantially cylindrical riser section  428  and/or by the substantially planar surface  430  ( FIG.  4   ), tier  414  has a diameter D 2  through axial length FG defined by the substantially cylindrical riser section  428  and/or by the substantially planar surface  426  ( FIG.  4   ) that is less than diameter D 1 , tier  412  has a diameter D 3  through axial length FG defined by the substantially cylindrical riser section  424  and/or by the substantially planar surface  422  ( FIG.  4   ) that is less than diameter D 1  and diameter D 2 , and tier  410  has a diameter D 4  through axial length FG defined by the substantially cylindrical riser section  420  and/or by the substantially planar surface  418  ( FIG.  4   ) that is less than diameter D 1 , diameter D 2 , and diameter D 3 . 
     An inner surface  568  of first cylinder conductor  502  concentrically surrounds and is slidably engaged with an outer surface  570  of first piston conductor  512  from radius HI along axial length FG. An inner surface  572  of second piston conductor  514  concentrically surrounds is slidably engaged with an outer surface  574  of second cylinder conductor  504  from radius HI along axial length FG. Third cylinder conductor  506  concentrically surrounds third piston conductor  516  from radius HI along axial length FG. Barrel  508  concentrically surrounds arm  518  from radius HI along axial length FG. First piston conductor  512 , second piston conductor  514 , third piston conductor  516 , and arm  518  are insertable into and retractable from first cylinder conductor  502 , second cylinder conductor  504 , third cylinder conductor  506 , and barrel  508 . First cylinder conductor  502  is mechanically affixed to internal surface  564  of head-end interface  400  tier  410  by threaded members  402 A and  402 B extending from an outer surface  566  of head-end interface  400  thru internal surface  564  and into first cylinder conductor  502 . Second cylinder conductor  504  is mechanically affixed to internal surface  564  of head-end interface  400  tier  412  by threaded members  404 A and  404 B extending from outer surface  566  of head-end interface  400  thru internal surface  564  and into second cylinder conductor  504 . Third cylinder conductor  506  is mechanically affixed to internal surface  564  of head-end interface  400  tier  414  by threaded members  406 A and  406 B extending from outer surface  566  of head-end interface  400  thru internal surface  564  and into third cylinder conductor  506 . Barrel  508  is mechanically affixed to internal surface  564  of head-end interface  400  tier  416  by threaded members  408 A and  408 B extending from outer surface  566  of head-end interface  400  thru internal surface  564  and into barrel  508 . In use, if the outermost tube, barrel  508  acts as a rigid outer tube of conductor rod  500 . 
     Piston conductors  512 - 516  and arm  518  are in electrical and physical communication with their respective cylinder conductors  502 - 506  and barrel  508  via one or more conducting interfaces. For example, a conducting interface  528  comprises a contacting interface between an exterior contacting surface  529  of arm  518  and an interior contacting surface  531  of barrel  508 . Conducting interface  528  provides both a slidable physical interface as well as an electrical interface between barrel  508  and arm  518 . Acting as an electrical interface, electrical power is transferred from piston conductors  512 - 516  to their respective cylinder conductors  502 - 506 , allowing for the continuous transfer of electrical power while the conductor rod  500  extends and retracts. Various technologies may be used to provide for a physical and electrical interface. Arm  518  extends and retracts by sliding along the conducting interface  528 , maintaining a physical and electrical interface. In  FIG.  5   , the interface is head-end interface  400 , though the same technology and techniques can be used to attach piston conductors  512 - 516  to connector assembly  114  of  FIG.  1    using threaded members. The attachment is designed to provide an airtight (or hermetic) seal within these cavities. 
     Another example of a conducting interface is conducting interface  530 . Rather than direct contact between a cylinder conductor and a piston conductor acting as an electrical and physical interface, conducting interface  530  uses carbon brushes, such as brush  532 . Brush  532  is a solid material formed from a conductive material, such as carbon or graphite, that provides both a physical and electrical interface between second cylinder conductor  504  and second piston conductor  514 . Brush  532  may be formed by compacting a mix of materials such as carbon, graphite, and metallic power (e.g. copper) into a solid piece of material sized and shaped to be used in conducting interface  530 . 
     Another example of an electrical interface material that provides for the conduction of electrical power from a piston conductor to a cylinder conductor is a metallic alloy that is liquid at a certain temperature, such as room temperature. An example of a metallic alloys is GALINSTAN. GALINSTAN is a eutectic alloy composed of gallium, indium, and tin which melts at −19 C (−2 F) and is thus liquid at room temperature. It should be noted, however, that other metal allows with properties similar to GALINSTAN may be used and are considered to be within the scope of the presently disclosed subject matter. 
     In order to keep a metallic alloy at an interface, the metallic alloy will be contained within a space enclosed by the surfaces of the piston conductor and the cylinder conductor in which the liquid alloy is being used. For example, conducting interface  534  is a space defined by an interior surface  539  of first cylinder conductor  502  and an exterior surface  541  of first piston conductor  512 . Conducting interface  534  is configured to act as a fluidic barrier, reducing or eliminating potential leaks of the liquid metallic alloy contained therein into other areas of the conductor rod  500 . As first piston conductor  512  extends and retracts within first cylinder conductor  502 , conducting interface  534  with a liquid metallic alloy contained therein provide for a constant electrical connection between first cylinder conductor  502  and first piston conductor  512 . 
     During use, the conducting interface  534  may be filled with additional liquid metallic alloy.  FIG.  5    illustrates one manner in which this may be accomplished, though other technologies for filling or refilling conducting interface  534  with additional liquid metallic alloy may be used and are considered to be within the scope of the presently disclosed subject matter. In  FIG.  5   , to introduce a liquid metallic alloy into conducting interface  534 , piston channel  536 , and interface channel  538  are used. To introduce a liquid metallic alloy into conducting interface  534 , conductor rod  500  is in a retracted configuration so that first piston conductor  512  abuts or nearly abuts interface channel  538  so that interface channel  538  is in liquid communication with piston channel  536 . Terminal connector  520  is removed, creating a fluidic input bore  537  extending through the head-end interface  400  providing for interface channel  538  to extend from an outer surface  559  of head-end interface  510  to piston channel  536 . The liquid metallic alloy can be introduced at input  540 , through interface channel  538 , through fluidic input bore  537 , through piston channel  536 , and into conducting interface  534 . Bore  438  may also be used to introduce air or other fluids into an inner volume  560 , or annular space, of first piston conductor  512 . In some examples, the fluid is pressurized air that is used to increase a pressure in inner volume  560 , forcing first piston conductor  512  away from head-end interface  400 . 
     Turning from the structure of work machine  100 , conductor rod  500 , and head-end interface  400  as illustrated in  FIG.  5   ,  FIG.  6    illustrates a method  600  involving these structures.  FIG.  6    is a flowchart of a representative method  600  for using multi-tiered head-end interface of a rod conductor rod to power a work. As shown in  FIG.  6   , at step  602  at least a proximal end of a conductor rod  500  is secured to a work machine. For example, step  602  may be performed by connecting cylinder conductors  502 , 504 , and  506  to head-end interface  400  using terminal connectors. As discussed in detail above, work machine  100 , such as a hauling truck at a mining site, can include conductor rod  106  with a plurality of conductive tubes, typically made of an aluminum alloy, arranged concentrically around a longitudinal axis. Near a head  122  of conductor rod  106  proximal to work machine  100 , head-end interface  400  is integrated into conductor rod  500 , as reflected in  FIG.  5   . Conductor rod  500  can be mounted to work machine  100  in any convenient fashion depending on the implementation, including securing the conductor rod to work machine  100  in some situations to be stationary and in other situations to be rotational about its longitudinal axis. 
     Further, in a step  604 , a distal end of conductor rod  500  is connected to a connector assembly, such as connector assembly  114  of  FIG.  1   . In step  604 , piston conductors are affixed to connector assembly  114  of  FIG.  1   . For example, piston conductors  512 - 516  are affixed to connector assembly  114  of  FIG.  1   . Connecting cylinder conductors  502 ,  504 , and  506  to head-end interface  400  and piston conductors  512 - 516  to connector assembly  114 , when piston conductors  512 - 516  are slidably engaged to cylinder conductors  502 - 506  provide for a continuous electrical path from a power source, through connector assembly  114 , piston conductors  512 - 516 , cylinder conductors  502 - 506 , into and through head-end interface  400 . 
     In step  606 , work machine  100  is electrically connected to head-end interface  400  using one or more terminal connectors and wire or cables. The head-end interface  400  is a multi-tier interface, meaning the electrical connection to each cylinder conductor through a terminal connector is at a different tier of head-end interface. To provide power to work machine  100 , at step  608 , connector assembly  114  is connected to power rail  108  via trailing arms  116  and contactor  118 . 
     At step  610 , electrical power is delivered through the terminal connectors into work machine  100 . In some examples, trailing arms  116  are conductors coupled to contactor  118 , each conducting voltage and current at a different electrical pole and corresponding to the conductors within conductor rod  106 . The voltages are designed to service various loads in work machine  100 , including electric engine  102  of work machine  100 . 
     In step  612 , a pneumatic connection is established with a bore, such as bore  438  of  FIG.  5   , positioned at a longitudinal end of the head-end interface. The connection with bore  438 , in the illustrated examples, provides passage for pressurized air into cavities within conductor rod  500  for providing forces to move or position arm  110  with respect to barrel  109 . 
     While  FIGS.  1 - 6    illustrate a first example of head-end interface  120 ,  FIGS.  7  and  8    depict a second example of a head-end interface  700  for use with work machine  100 . Head-end interface  700  includes structural features that enable electrical connection with conductor rod  106  radially around its exterior, as well as pneumatic connection with conductor rod  106  axially through an interface end  702 . Head-end interface  700 , with an interface on the circumference of conductor rod  106 , provides radial access for passing electrical power from conductor rod  106  to work machine  100  and enables continued electrical conductivity during rotation of conductor rod  106  around a longitudinal central axis YZ.  FIG.  7    is a view of a portion of conductor rod  106 ).  FIG.  8    is a longitudinal section of conductor rod  106  along the cut lines shown in  FIG.  7   , revealing internal conductors, cavities, and conduits as discussed below. 
     Referring first to  FIG.  7   , conductor rod  106  includes head-end interface  700  connected to head  122  of barrel  109 . Barrel  109  has an outer shell  703  around its exterior, which may be a conductive material having mechanical rigidity, such as an aluminum alloy. In some implementations, outer shell  703  serves as an electrical grounding path for conductor rod  106 . Radially around its exterior, head-end interface  700  includes rings of conductive material, specifically first metallic contact  704  and second metallic contact  706 . First metallic contact  704  and second metallic contact  706  are connected within head-end interface  700  to conductors extending longitudinally within conductor rod  106  that carry electrical power from power rail  108 . First metallic contact  704  and second metallic contact  706  function as interfaces for the electrical power from power rail  108  to work machine  100 . The example depicted in  FIG.  7    contains two contacts as first metallic contact  704  and second metallic contact  706  corresponding to two conductors within conductor rod  106 . In other examples, more or fewer conductors and contacts may be used to correspond to the arrangement of conductors within conductor rod  106 . For instance, a version of head-end interface  700  not shown could employ one or more rings of conductive material in addition to first metallic contact  704  and second metallic contact  706 . 
     Separators in the form of an insulative material such as plastic are positioned longitudinally between first metallic contact  704  and second metallic contact  706 . First separator  708 , for instance, serves as a structural interface between head-end interface  700  and head  122  of barrel  109 , while electrically separating outer shell  703  and second metallic contact  706 . Second separator  710  spaces first metallic contact  704  from second metallic contact  706 . Third separator  712  acts as an endcap for head-end interface  700 , while providing insulation longitudinally for first metallic contact  704 . As shown in  FIG.  7   , third separator  712  has an annular shape and includes interface end  702  having a surface  709  extending perpendicular from central axis YZ and forming a structural terminus for conductor rod  106 . The insulative material of third separator  712  can serve to protect equipment and personnel from voltages present on first metallic contact  704  and second metallic contact  706  present farther inward longitudinally along central axis YZ on conductor rod  106 . Thus, in some examples, first separator  708 , second separator  710 , and third separator  712  help electrically insulate first metallic contact  704 , and second metallic contact  706 , and provide structural and mechanical form to head-end interface  700 . 
     When installed on work machine  100 , conductor rod  106  enables electrical connection radially via one or more of first metallic contact  704  and second metallic contact  706 . Extending around a circumference of head-end interface  700 , first metallic contact  704  and second metallic contact  706  of head-end interface  700  can provide a substantial surface area for interfacing electrical power from conductor rod  106  to work machine  100  with a high level of conductivity. A mating mechanism (not shown) within work machine  100  can grasp or otherwise contact first metallic contact  704  and second metallic contact  706  around the exterior of head-end interface  700 . In addition, in some examples, first metallic contact  704 , second metallic contact  706 , and the mating mechanism may facilitate a sliding connection. For instance, in implementations where conductor rod  106  rotates about central axis YZ, such as to enable vertical movement of trailing arms  116 , first metallic contact  704  and second metallic contact  706  permit head-end interface  700  to stay in electrical contact with a mating mechanism while the rotation occurs, ensuring the continued delivery of electrical power to work machine  100 . 
       FIG.  7    further illustrates a pneumatic interface within interface end  702  of third separator  712 . In general, third separator  712  includes one or more openings through interface end  702  in which pressurized air may be passed axially to the inside of conductor rod  106  from a compressor within work machine  100 . The pressurized air may be used as an energy source to drive mechanical movement of conductor rod  106 . In some examples, the pressurized air can be used in a pneumatic control system to force nested conductor tubes within conductor rod  106  to move axially with respect to each other, such as when arm  110  is forced to slide axially with respect to barrel  109 . In other examples, the pressurized air can be routed through conductor rod  106  to be used near or beyond tip  124 , such as to provide force relating to contactor  118  on power rail  108 . As embodied in  FIG.  7   , the openings for pressurized air through interface end  702  include center bore  714 , first middle bore  716 , second middle bore  718 , first outer bore  720 , and second outer bore  722 , which are explained below with respect to  FIG.  8   . Center bore  714  is at an axial center of head-end interface  700  along the central axis YZ. In some examples, such as shown in  FIG.  7   , first middle bore  716  and second middle bore  718  are positioned a first radial distance outward from the central axis YZ, while first outer bore  720  and second outer bore  722  are located a second radial distance outward from the central axis YZ, where the second radial distance is greater than the first radial distance. 
       FIG.  8   , which is a longitudinal section of conductor rod  106  in  FIG.  7   , illustrates the internal structure of barrel  109  and head-end interface  700 .  FIG.  8    reveals that the contactor rings on the exterior of head-end interface  700 , which are first metallic contact  704  and second metallic contact  706 , are annular-shaped rings or discs that connect with a respective tubular conductor and extend radially for a portion through the interior of head-end interface  700 . For instance, a first barrel conductor  802  is a metallic material such as an aluminum alloy in the shape of a tube or a hollow cylinder centered axially along the central axis YZ. A first barrel cavity  804  is defined by an inner surface  805  of first barrel conductor  802 . First barrel conductor  802  is a central conductor within barrel  109  and, in the example of  FIG.  8   , terminates longitudinally in the direction of Y of central axis YZ axis into first metallic contact  704 . First barrel conductor  802  and first metallic contact  704  are configured to be substantially orthogonal to each other, and together provide a conductive path for electrical voltage radially from an interior to an exterior of conductor rod  106 . First metallic contact  704  extends from first barrel conductor  802  to an outer surface  835  of head-end interface  700 , as shown, where mechanical and electrical connection can be made to work machine  100 . In one example, first barrel conductor  802  and first metallic contact  704  conduct +1500 VDC from within barrel  109  to first metallic contact  704  at an exterior of conductor rod  106 . In some examples, first metallic contact  704  and first barrel conductor  802  are the same material and structure, although they may be different substances or separate pieces connected together. In general, first barrel conductor  802  and first metallic contact  704  form a shape resembling a tubular pole (first barrel conductor  802 ) arranged along central axis YZ with a flat base or endplate (first metallic contact  704 ) positioned along the X axis. 
     Similarly, second barrel conductor  806  is a conductor formed of a metallic material such as an aluminum alloy in the shape of a tube or a hollow cylinder as part of barrel  109 . Second barrel conductor  806  is axially centered along central axis YZ and concentrically positioned surrounding first barrel conductor  802 . A distance between the concentric tubes of first barrel conductor  802  and second barrel conductor  806  results in second barrel cavity  808 . Radially outside second barrel conductor  806  and within an outer shell  703  of barrel  109  is third barrel cavity  810 . Second barrel conductor  806  terminates longitudinally in the direction Y of the YZ axis in  FIG.  8    into second metallic contact  706 , which is substantially orthogonal with second barrel conductor  806 . Together, second barrel conductor  806  and second metallic contact  706  form a conductive path for electrical voltage, such as −1500 VDC from within barrel  109  to second metallic contact  706  at an exterior of conductor rod  106 . In some examples, second metallic contact  706  and second barrel conductor  806  are the same material and structure, although they may be different substances or separate components connected together. As with first barrel conductor  802  and first metallic contact  704 , second barrel conductor  806  and second metallic contact  706  collectively form a shape resembling a tubular pole arranged along the central axis YZ having a flat base or endplate positioned along the X axis. 
       FIG.  8    further illustrates a portion of arm  110  nested within outer shell  703  and barrel  109 . Specifically, arm  110  includes first arm conductor  812  arranged axially along the central axis YZ. First arm conductor  812  is a conductor made of a metallic material such as an aluminum alloy and has a tubular or hollow cylinder shape. An outer diameter of first arm conductor  812  is sized so that first arm conductor  812  contacts an inner surface of first barrel conductor  802  and yet can slide axially into the annular first barrel cavity  804 . The tubular configuration of first arm conductor  812  leads to a central arm cavity  814  along the axial center of first arm conductor  812 . The combination of central arm cavity  814  and first barrel cavity  804  provides a central passageway of open space longitudinally within conductor rod  106 . Similarly, arm  110  includes a second arm conductor  816  as a tube-shaped conductive element arranged concentrically around first arm conductor  812 . Second arm conductor  816 , which may also be an aluminum alloy or another material having an acceptable level of electrical conductivity and mechanical resilience, has an outer diameter sufficient to cause contact with an inner diameter of second barrel conductor  806 . At the same time, the sizing of second arm conductor  816  and second barrel conductor  806  are such that second arm conductor  816  may freely slide within second barrel conductor  806  and move into second barrel cavity  808  during retraction of arm  110 . 
     Finally, in the example of  FIG.  8   , arm  110  includes third arm conductor  818 . Third arm conductor  818  is also a conductive material such as an aluminum alloy and is sized to slide in contact within an inner diameter of outer shell  703 . In a position of retraction for arm  110 , third arm conductor  818  will slide into third barrel cavity  810  within barrel  109 . The axial ends of first arm conductor  812 , second arm conductor  816 , and third arm conductor  818  leading into barrel  109  are respectively covered by first arm cap  820 , second arm cap  822 , and third arm cap  824 . First arm cap  820  essentially fills the radial diameter of first barrel cavity  804  within first barrel conductor  802  but for central arm cavity  814 . Second arm cap  822  substantially fills the radial distance of second barrel cavity  808  (i.e., the distance between the outer diameter of first barrel conductor  802  and the inner diameter of second barrel conductor  806 ). Third arm cap  824  substantially fills the radial distance of third barrel cavity  810  (i.e., the distance between the outer diameter of second barrel conductor  806  and the inner diameter of outer shell  703 ). 
     Head-end interface  700  further includes a series of bores and passageways through which pressurized air may be delivered within at least barrel  109 . As arm  110  is axially slidable within barrel  109 , pressurized air from a pneumatic control system may provide forces to cause the extension or retraction of arm  110 . As noted above, the pressurized air is provided to conductor rod  106  from work machine  100  through interface end  702 . As shown in  FIG.  8   , center bore  714  passes from interface end  702  along the central axis YZ and into first barrel cavity  804 . As first barrel cavity  804  and central arm cavity  814  adjoin each other in forming a central passageway through conductor rod  106 , center bore  714  serves to feed pressurized air from work machine  100  into barrel  109  and along the length of arm  110 , possibly to tip  124 . First outer bore  720  and second outer bore  722  provide passageways for pressurized air to enter third barrel cavity  810  of barrel  109 . In some examples, the pressurized air within third barrel cavity  810  provides an axial force against third arm cap  824  that, depending on other pneumatic forces acting on arm  110 , may affect the movement of arm  110  axially within barrel  109 . 
     Likewise, first middle bore  716  and second middle bore  718  (not shown in  FIG.  8   ) provide passageways for pressurized air to enter second barrel cavity  808  of barrel  109 . First middle bore  716  and second middle bore  718  in some implementations are in the same plane as center bore  714 , first outer bore  720 , and second outer bore  722 , namely, the longitudinal section shown in  FIG.  8   . As illustrated in  FIG.  8   , however, in other implementations first middle bore  716  and second middle bore  718  are offset angularly about the central axis YZ with respect to first outer bore  720  and second outer bore  722 . In some examples, first middle bore  716  and second middle bore  718  are each about 90 degrees apart from first outer bore  720  and second outer bore  722 , although other angles are within the scope of this disclosure. This angular offset may, for instance, provide room between each of the bores along interface end  702  for connection of equipment to supply the pressurized air. 
     In some examples, one or more of first metallic contact  704 , second metallic contact  706 , first separator  708 , second separator  710 , and second separator  710  include ringed conduits to provide passageways for pressurized air circumferentially around the central axis Y-Y from where axial bores radially enter interface end  702 . For instance, at the upper right in  FIG.  8   , second outer bore  722  provides access for pressurized air into conductor rod  106  that leads into third barrel cavity  810 . Third ringed conduit  832  intersects with second outer bore  722  and forms a pathway (not shown) of circular or similar shape for the pressurized air to travel about axis Y-Y (i.e., in the X-Z plane). At the lower right in  FIG.  8   , third ringed conduit  832  intersects first outer bore  720 . Similarly, first middle bore  716  extends longitudinally parallel to central axis YZ and intersects with first ringed conduit  828  within third separator  712 . From first ringed conduit  828 , the pressurized air can pass through internal middle bore  826  and into second barrel cavity  808 . Second ringed conduit  830  provides an additional example of a pneumatic connection or pathway made from a radial position of first outer bore  720  and second outer bore  722  circumferentially around head-end interface  700  (i.e., in the X-Z plane). The various ringed conduits may be made as grooves within longitudinal sides of first metallic contact  704  or second metallic contact  706  or within first separator  708 , second separator  710 , or third separator  712 . Moreover, additional bores connecting from one or more of the ringed conduits may be present within head-end interface  700  to provide other paths for pressurized air to enter any one of first barrel cavity  804 , second barrel cavity  808 , or third barrel cavity  810 . 
     In addition, although discussed in terms of pneumatic control, one or more of center bore  714 , first middle bore  716 , second middle bore  718 , first outer bore  720 , or second outer bore  722  could be used to facilitate the passage of signals into conductor rod  106 . For instance, conductor rod  106  could contain electrical sensors or controls, such as for monitoring its position, temperature, or movement, and signals relating to those activities may be passed through interface end  702  via the one or more bores. The signals could be passed optically using line-of-sight arrangements, such as through center bore  714 , first barrel cavity  804 , and central arm cavity  814 , or they could be passed through wires, optical fibers, or other media. Additional orifices within interface end  702  and through head-end interface  700  could be added to facilitate the passage of electrical or optical signals as desired without departing from the principles discussed. 
     Therefore, the example head-end interface  700  in  FIGS.  7  and  8    provides a structure configured to enable work machine  100  to have an electrical connection radially with conductor rod  106  and a pneumatic connection axially. The electrical connection can provide sufficient power to operate electric engine  102 , while the pneumatic connection can deliver pressurized air to selective cavities within conductor rod  106  to cause at least axial movement of arm  110  with respect to barrel  109 . Moreover, head-end interface  700  provides a configuration sufficient, if desired for the implementation, for conductor rod  106  to rotate about its longitudinal axis while maintaining electrical connection between head-end interface  700  and work machine  100 . 
     Turning from the structure of work machine  100 , conductor rod  106 , and head-end interface  700  as illustrated in  FIGS.  7  and  8    to a method  900  for powering a work machine from a moveable conductive rod. As shown in  FIG.  9   , at step  902  at least a proximal end of a rod of concentrically arranged tubular conductors is secured to a work machine. As discussed in detail above, work machine  100 , such as a hauling truck at a mining site, can include conductor rod  106  with a plurality of conductive tubes, typically made of an aluminum alloy, arranged concentrically around a longitudinal axis. Near a head  122  of conductor rod  106  proximal to work machine  100 , head-end interface  700  is integrated into conduction rod  106 , as reflected in  FIGS.  1 ,  7 , and  8   . Conductor rod  106  can be mounted to work machine  100  in any convenient fashion depending on the implementation, including securing the conductor rod to work machine  100  in some situations to be stationary and in other situations to be rotational about its longitudinal axis. 
     Further, in a step  904 , an electrical connection is established with two or more ringed contacts positioned around the circumference of a head-end interface on the conductor rod. As implemented in the example of  FIG.  7   , head-end interface  700  includes first metallic contact  704  and second metallic contact  706  around the outside of conductor rod  106 . According to step  904 , connection is made between one or both of first metallic contact  704  and second metallic contact  706  and compatible contacts within work machine  100  at the radial sides of head-end interface  700 . In step  906 , a pneumatic connection is established with two or more bores positioned at a longitudinal end of the head-end interface. The two or more bores may include center bore  714 , first middle bore  716 , second middle bore  718 , first outer bore  720 , or second outer bore  722 , for example. The connection with these bores, in the illustrated examples, provides passage for pressurized air into cavities within conductor rod  106  for providing forces to move or position arm  110  with respect to barrel  109 . 
     In subsequent steps, the work machine is powered with electricity, and the conductor rod is power with pressurized air. Specifically, in step  906 , a distal end of the rod is connected to a power rail providing electrical power. As shown in  FIG.  1   , the connection between contactor  118  and power rails  108  provides access for work machine  100  to electrical power present on power rails  108 . In step  910 , the electrical power is delivered through the two or more ringed contacts on the conductor rod to the electrical connection. As shown in part in  FIG.  8   , concentric conductor tubes convey the electrical power from power rail  108  through arm  110  and barrel  109  to the series of annular or disk-shaped terminals, first metallic contact  704  and second metallic contact  706 . From those contacts, the electrical power may pass through a connection into work machine  100 . In a step  912 , pressurized air is delivered from the work machine through the pneumatic connection to the two or more bores. In some examples, the delivery of pressurized air through interface end  702  and into head-end interface  700  provides a means under a pneumatic control system to manipulate the position of at least arm  110 . Accordingly, head-end interface  700  can provide an interface that enables radial attachment for electrical power and axial attachment for pneumatic power between conductor rod  106  and work machine  100 , enabling the efficient powering of work machine  100  and conductor rod  106  including the flexibility to permit rotation of conductor rod  106  about its longitudinal axis as desired. 
     Those of ordinary skill in the field will also appreciate that the principles of this disclosure are not limited to the specific examples discussed or illustrated in the figures. For example, while conductor rod  106  for  FIGS.  7  and  8    are illustrated with two conductors, three or more conductors may be employed following the principles explained in the present disclosure. In addition, the principles disclosed are not limited to implementation on a work machine. Any moving vehicle deriving electrical power from a ground-based conductor rail could benefit from the examples and techniques disclosed and claimed. 
     INDUSTRIAL APPLICABILITY 
     A head-end interface of the conductor rod proximate the work machine includes metallic rings spaced apart and extending circumferentially around the head-end interface. Bores pass longitudinally through the head-end interface and into annular cavities within the conductor rod between the concentric metal tubes. The metallic rings enable the delivery of electrical power radially from the conductor rod across substantial surface area for powering the work machine, while the bores enable the delivery of pneumatic power longitudinally into the conductor rod for powering axial movement of the conductor rod. As a result, the head-end interface enables radial connection to the conductor rod for electrical power with an option for rotating the conductor rod about its longitudinal axis. 
     As noted above with respect to  FIGS.  7  and  8   , an example conductor rod and head-end interface generally includes a conductor rod  106  that is extendable or retractable from a work machine  100 . Conductor rod  106  includes a barrel  109  and an arm  110  axially moveable within barrel  109 . A first conductor within barrel  109  includes a first barrel conductor  802  in the shape of a tube extending along a longitudinal axis and a first metallic contact  704  extending orthogonally from the first barrel conductor to an outer diameter of a head-end interface  700 . A second conductor within barrel  109  includes a second barrel conductor  806  in the shape of a tube concentrically surrounding and separated from the first barrel conductor  802  by a second barrel cavity  808  and a second metallic contact  706  extending from the first barrel conductor to the outer diameter. The second metallic contact  706  is farther from the end of the conductor rod  106  than the first metallic contact  704 . Orifices within the head-end interface  700  enable insertion of pressurized air from work machine  100  to the conductor rod  106 . 
     In the examples of the present disclosure, the head-end interface  700  enables a radial connection to electrical contacts on the exterior of conductor rod  106 . A first metallic contact  704  and second metallic contact  706  in the shape of rings permit engagement by work machine around the circumference of head-end interface  700 , increasing conductive surface area between conductor rod  106  and work machine  100 . Moreover, in implementations where conductor rod  106  may rotate about its longitudinal axis, the radial connection through first metallic contact  704  and second metallic contact  706  permits continued electrical connection and flow of electrical power during the rotation. Further, bores within an interface end  702  serve as passageways for pressurized air into head-end interface  700 , which provide energy for pneumatically controlling extension and retraction of arm  110  with respect to barrel  109 . Thus, with head-end interface  700 , high levels of electrical power may be conducted from power rail  108  to work machine  100  while pressurized air provided into conductor rod  106  can help position arm  110 . 
     Unless explicitly excluded, the use of the singular to describe a component, structure, or operation does not exclude the use of plural such components, structures, or operations or their equivalents. As used herein, the word “or” refers to any possible permutation of a set of items. For example, the phrase “A, B, or C” refers to at least one of A, B, C, or any combination thereof, such as any of: A; B; C; A and B; A and C; B and C; A, B, and C; or multiple of any item such as A and A; B, B, and C; A, A, B, C, and C; etc. 
     While aspects of the present disclosure have been particularly shown and described with reference to the embodiments above, it will be understood by those skilled in the art that various additional embodiments may be contemplated by the modification of the disclosed machines, systems and methods without departing from the spirit and scope of what is disclosed. Such embodiments should be understood to fall within the scope of the present disclosure as determined based upon the claims and any equivalents thereof.