Patent Publication Number: US-2011068620-A1

Title: Wear protectors for protecting guide and/or drive lugs of an endless track for traction of an off-road vehicle

Description:
FIELD OF THE INVENTION 
     The invention relates to endless elastomeric tracks for traction of vehicles operable in off-road conditions. 
     BACKGROUND 
     Certain off-road vehicles, such as construction vehicles (e.g., loaders, bulldozers, excavators, etc.), agricultural vehicles (e.g., harvesters, combines, tractors, etc.) forestry vehicles (e.g., feller-bunchers, tree chippers, knuckleboom loaders, etc.) and military vehicles (e.g., combat engineering vehicles (CEVs), etc.) to name a few, are often equipped with endless elastomeric tracks that enhance their traction and floatation on soft, low friction and/or uneven grounds (e.g., soil, mud, sand, ice, snow, etc.) on which they operate. 
     One type of endless elastomeric track comprises an inner side including a plurality of projections, commonly referred to as “lugs”, which are spaced apart in its longitudinal direction and used for guiding and/or driving the track around wheels of a vehicle to which the track provides traction. Very often, a main factor reducing the track&#39;s useful life is wear of the lugs due to their motion relative to the wheels of the vehicle. For instance, as they move relative to the wheels of the vehicle, the lugs can come into contact with (e.g., rub or otherwise frictionally contact) one or more of these wheels and this contact can wear out their elastomeric material (e.g., rubber). This contact can be particularly strong when the vehicle is turning or moving on a hill or other sloped terrain. Over time, such contact wears out the elastomeric material of the lugs, possibly to a point where the lugs are so degraded that the track can no longer be used efficiently and has to be repaired or replaced. In some cases, such degradation of the lugs can occur although a carcass of the track remains in acceptable condition. In other words, the lugs can wear out at a significantly greater rate than the carcass of the track. 
     For these and other reasons, there is a need to improve endless elastomeric tracks for traction of off-road vehicles. 
     SUMMARY OF THE INVENTION 
     According to a first broad aspect, the invention provides a cover for protecting a lug of an inner side of an endless track for traction of an off-road vehicle. The lug comprises elastomeric material and is used for at least one of guiding the endless track and driving the endless track. The cover is shaped to cover at least part of a periphery of the lug. The cover comprises an aperture for admitting a fastener to fasten the cover to the lug such that the fastener extends inside the lug and is capable of being put in a state of tension. 
     According to a second broad aspect, the invention provides an endless track for traction of an off-road vehicle. The endless track comprises a ground-engaging outer side for engaging the ground and an inner side for facing a plurality of wheels of the off-road vehicle. The inner side comprises a plurality of lugs for at least one of guiding the endless track and driving the endless track. Each lug comprises: elastomeric material; a periphery on which is placeable a cover for protecting the lug; and a cavity for admitting a fastener to fasten the cover to the lug. 
     According to a third broad aspect, the invention provides a cover for protecting a lug of an inner side of an endless track for traction of an off-road vehicle. The lug comprises elastomeric material, a periphery, and a cavity extending inwardly from the periphery. The cover is shaped to cover at least part of the periphery of the lug and comprises: a protrusion positionable within the cavity to retain the cover on the lug; and an aperture for admitting a fastener to fasten the cover to the lug. 
     According to a fourth broad aspect, the invention provides an endless track for traction of an off-road vehicle. The endless track comprises a ground-engaging outer side for engaging the ground and an inner side for facing a plurality of wheels of the off-road vehicle. The inner side comprises a plurality of lugs for at least one of guiding the endless track and driving the endless track. Each lug comprises: elastomeric material; a periphery on which is placeable a cover for protecting the lug, the cover comprising a protrusion; and a cavity for receiving the protrusion and admitting a fastener to fasten the cover to the lug. 
     According to a fifth broad aspect, the invention provides a cover for protecting a lug of an inner side of an endless track for traction of an off-road vehicle. The lug comprises elastomeric material, a periphery, and a cavity extending inwardly from the periphery. The cover is shaped to cover at least part of the periphery of the lug. The cover comprises a protrusion positionable within the cavity to retain the cover on the lug. The protrusion is configured to restrain movement of the cover relative to the lug in two or more directions. 
     According to a sixth broad aspect, the invention provides an endless track for traction of an off-road vehicle. The endless track comprises a ground-engaging outer side for engaging the ground and an inner side for facing a plurality of wheels of the off-road vehicle. The inner side comprises a plurality of lugs for at least one of guiding the endless track and driving the endless track. Each lug comprises: elastomeric material; a periphery on which is placeable a cover for protecting the lug, the cover comprising a protrusion; and a cavity for receiving the protrusion, the protrusion restraining movement of the cover relative to the lug in two or more directions when the protrusion is in the cavity. 
     According to a seventh broad aspect, the invention provides a cover for protecting a lug of an inner side of an endless track for traction of an off-road vehicle. The lug comprises elastomeric material, a periphery, and a cavity extending inwardly from the periphery. The periphery of the lug comprises a first surface and a second surface opposite the first surface. The cover comprises: a first covering member for covering at least part of the first surface of the lug; and a second covering member, separate from the first covering member, for covering at least part of the second surface of the lug. 
     According to an eighth broad aspect, the invention provides an endless track for traction of an off-road vehicle. The endless track comprises a ground-engaging outer side for engaging the ground and an inner side for facing a plurality of wheels of the off-road vehicle. The inner side comprises a plurality of lugs for at least one of guiding the endless track and driving the endless track. Each lug comprises: elastomeric material; a periphery comprising a first surface and a second surface opposite the first surface, at least part of the first surface being coverable by a first covering member, at least part of the second surface being coverable by a second covering member separate from the first covering member; and a cavity extending from the first surface to the second surface for admitting a fastener interconnecting the first covering member and the second covering member. 
     These and other aspects of the invention will now become apparent to those of ordinary skill in the art upon review of the following description of embodiments of the invention in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A detailed description of embodiments of the invention is provided below, by way of example only, with reference to the accompanying drawings, in which: 
         FIG. 1  shows an example of an off-road vehicle in accordance with an embodiment of the invention; 
         FIGS. 2 to 4  respectively show a top view, a side elevation view, and a bottom view of part of an endless track of the off-road vehicle, wherein lugs of the endless track are protected by wear protectors; 
         FIG. 5  shows a cross-sectional view of the endless track, without the wear protectors; 
         FIGS. 6A and 6B  respectively show a perspective view and a cross-sectional view of one of the lugs of the endless track; 
         FIG. 7  shows a cross-sectional view of one of the lugs with its wear protector; 
         FIGS. 8 to 10  respectively show a perspective view, a side elevation view, and a rear view of a covering portion of one of the wear protectors; and 
         FIG. 11  shows the endless track in relation to a drive wheel of the off-road vehicle. 
     
    
    
     It is to be expressly understood that the description and drawings are only for the purpose of illustrating certain embodiments of the invention and are an aid for understanding. They are not intended to be a definition of the limits of the invention. 
     DETAILED DESCRIPTION OF EMBODIMENTS 
       FIG. 1  shows an off-road vehicle  10  in accordance with an embodiment of the invention. In this embodiment, the off-road vehicle  10  is a construction vehicle for performing construction work. More specifically, in this example, the construction vehicle  10  is a bulldozer. In other examples, the construction vehicle  10  may be a backhoe loader, a skid steer loader, an excavator, or any other type of construction vehicle. 
     The construction vehicle  10  comprises a frame  12  supporting a prime mover  14 , a pair of track assemblies  16   1 ,  16   2 , a working implement  18 , and an operator cabin  20 , which enable an operator to move the construction vehicle  10  on the ground to perform construction work. 
     The prime mover  14  provides motive power to move the construction vehicle  10 . For example, the prime mover  14  may comprise an internal combustion engine and/or one or more other types of motors (e.g., electric motors, etc.) for generating motive power to move the construction vehicle  10 . The prime mover  14  is in a driving relationship with each of the track assemblies  16   1 ,  16   2 . That is, power derived from the primer mover  14  is transmitted to each of the track assemblies  16   1 ,  16   2  via a power train of the construction vehicle  10 . 
     The working implement  18  is used to perform construction work. In this embodiment, the working implement  18  is a dozer blade that can be used to push objects and shove soil, debris or other material. In other embodiments, the working implement  18  may take on various other forms, such as a bucket, a backhoe, a fork, a grapple, a scraper pan, an auger, a saw, a ripper, a material handling arm, or any other type of construction working implement. 
     The operator cabin  20  is where the operator sits and controls the construction vehicle  10 . More particularly, the operator cabin  20  comprises a set of controls that allow the operator to steer the construction vehicle  10  on the ground and operate the working implement  18 . 
     The track assemblies  16   1 ,  16   2  are drivable by the prime mover  14  to propel the construction vehicle  10  on the ground. More particularly, in this embodiment, each track assembly  16   i  (i=1 or 2) comprises an endless track  22  disposed around a plurality of wheels, including a drive wheel  24 , an idler wheel  26 , and a plurality of roller wheels  28   1 - 28   R . 
     The drive wheel  24  is rotatable by power produced by the prime mover  14  for driving the endless track  22  to propel the construction vehicle  10  on the ground. The idler wheel  26  and the roller wheels  28   1 - 28   R  do not convert power supplied by the prime mover  14  to motive force, but rather guide the endless track  22  and/or maintain it under tension as it is driven by the drive wheel  24 . As the endless track  22  is driven by the drive wheel  24 , the roller wheels  28   1 - 28   R  roll on a lower run of the endless track  22  to apply it on the ground for traction. 
     The endless track  22  provides traction to the construction vehicle  10 . With additional reference to  FIGS. 2 to 5 , the endless track  22  comprises an inner side  25  and a ground-engaging outer side  27 . The inner side  25  faces the wheels  24 ,  26 ,  28   1 - 28   R  and defines an inner area in which these wheels rotate. The ground-engaging outer side  27  engages the ground for traction of the construction vehicle  10 . The endless track  22  has a longitudinal axis  45  defining a longitudinal direction of the endless track  22  (i.e., a direction generally parallel to the longitudinal axis  45 ) and transversal directions of the endless track  22  (i.e., directions transverse to the longitudinal axis  45 ), including a lateral direction of the endless track  22  (i.e., a widthwise direction generally perpendicular to the longitudinal axis  45 ). 
     The endless track  22  comprises a main body  36  underlying the inner side  25  and the ground-engaging outer side  27 . In view of its underlying nature, the main body  36  can be referred to as a “carcass”. In this embodiment, the carcass  36  comprises elastomeric material  38  in which are embedded a plurality of reinforcements  42 ,  43 . 
     The elastomeric material  38  allows the carcass  36  to elastically change in shape as the endless track  22  is in motion around the wheels  24 ,  26 ,  28   1 - 28   R . The elastomeric material  38  can be any polymeric material with the property of elasticity. In this embodiment, the elastomeric material  38  includes rubber. Various rubber compounds may be used and, in some cases, different rubber compounds may be present in different areas of the carcass  36 . In other embodiments, the elastomeric material  38  may include another elastomer in addition to or instead of rubber (e.g., polyurethane elastomer). 
     The reinforcement  42  comprises a plurality of reinforcing cables  37   1 - 37   M  adjacent to one another. The reinforcing cables  37   1 - 37   M  extend generally in the longitudinal direction of the endless track  22  to enhance strength in tension of the track  22  along its longitudinal direction. In this embodiment, each of the reinforcing cables  37   1 - 37   M  is a cord or wire rope including a plurality of strands or wires. In other embodiments, each of the reinforcing cables  37   1 - 37   M  may be another type of cable and may be made of any material suitably flexible longitudinally (e.g., fibers or wires of metal, plastic or composite material). 
     The reinforcement  43  may comprise a layer of reinforcing cables or a layer of reinforcing fabric. The reinforcing cables may be cords or wire ropes including a plurality of strands or wires (e.g., of metal, plastic or composite material). Reinforcing fabric comprises pliable material made usually by weaving, felting, or knitting natural or synthetic fibers. For example, a layer of reinforcing fabric may comprise a ply of reinforcing woven fibers (e.g., nylon fibers or other synthetic fibers). Various other types of reinforcements may be provided in the carcass  36  in other embodiments. 
     The ground-engaging outer side  27  comprises a tread pattern  40  to enhance traction on the ground. The tread pattern  40  comprises a plurality of traction projections  58   1 - 58   T  distributed on the ground-engaging outer side  27  for enhancing traction on the ground. In this embodiment, each of the traction projections  58   1 - 58   T  has an elongated shape and is angled (i.e., defines an acute angle θ) relative to the longitudinal direction of the endless track  22 . The traction projections  58   1 - 58   T  may have various other shapes in other examples (e.g., curved shapes, shapes with straight parts and curved parts, etc.). 
     In this embodiment, each of the traction projections  58   1 - 58   T  comprises elastomeric material  41 . The elastomeric material  41  can be any polymeric material with the property of elasticity. More particularly, in this embodiment, the elastomeric material  41  includes rubber. Various rubber compounds may be used and, in some cases, different rubber compounds may be present in different areas of each of the traction projections  58   1 - 58   T . In other embodiments, the elastomeric material  41  may include another elastomer in addition to or instead of rubber (e.g., polyurethane elastomer). 
     The inner side  25  of the endless track  22  contacts the drive wheel  24  in order to cause motion of the endless track  22  around the wheels  24 ,  26 ,  28   1 - 28   R . The inner side  25  also contacts the idler wheel  26  and the roller wheels  28   1 - 28   R  which help to guide the endless track  22  and maintain it under tension as it is driven by the drive wheel  24 . 
     The inner side  25  comprises a plurality of track-directing projections  34   1 - 34   N  that are spaced apart in the longitudinal direction of the endless track  22 . Each of the track-directing projections  34   1 - 34   N , which can be referred to as a “lug”, is used for at least one of guiding the endless track  22  and driving the endless track  22  around the wheels  24 ,  26 ,  28   1 - 28   R . In that sense, the track-directing projections  34   1 - 34   N  can be referred to as “guide/drive projections”. 
     More particularly, in this embodiment, the track-directing projections  34   1 - 34   N  are guide projections for guiding the endless track  22  around the wheels  24 ,  26 ,  28   1 - 28   R  as the endless track  22  is driven by the drive wheel  24 . The guide projections  34   1 - 34   N , which will be referred to as “guide lugs”, cooperate with the wheels  24 ,  26 ,  28   1 - 28   R  to guide the endless track  22  as it moves around these wheels without themselves being responsible for imparting motion to the endless track  22 . 
     The inner side  25  comprises a friction drive surface  30  that frictionally engages the drive wheel  24  such that, as the drive wheel  24  rotates, friction between the friction drive surface  30  and the drive wheel  24  causes motion of the endless track  22  around the wheels  24 ,  26 ,  28   1 - 28   R  to propel the construction vehicle  10  on the ground. The endless track  22  is tensioned around the wheels  24 ,  26 ,  28   1 - 28   R  to create sufficient friction between the friction drive surface  30  and the drive wheel  24  to drive the track  22 . 
     For example, as shown in  FIG. 11 , in this embodiment, the drive wheel  24  comprises a first wheel portion  29   1  and a second wheel portion  29   2  that are spaced apart in the lateral direction of the endless track  22  to define a space  31  therebetween. In this case, the wheel portions  29   1 ,  29   2  are two (2) wheel members that are separate from one another and noncontiguous. In other cases, the wheel portions  29   1 ,  29   2  may be contiguous. As the endless track  22  is driven by the drive wheel  24  via friction between its friction drive surface  30  and the wheel portions  29   1 ,  29   2 , the guide lugs  34   1 - 34   N  pass in the space  31  between the wheel portions  29   1 ,  29   2 . By being constrained to move in the space  31 , the guide lugs  34   1 - 34   N  help to guide the motion of the endless track  22  around the wheels  24 ,  26 ,  28   1 - 28   R  in order to prevent undesired lateral movement or detracking of the track  22 . The guide lugs  34   1 - 34   N  may interact in a similar way with other ones of the wheels  26 ,  28   1 - 28   R  as they pass by them. 
     Each guide lug  34   n  (1≦n≦N) has a periphery  70 . With additional reference to  FIGS. 6A and 6B , in this embodiment, the periphery  70  includes a top surface  72  and four (4) surfaces that extend downwardly from the top surface  72 , namely a front surface  69   1 , a rear surface  69   3  and side surfaces  69   2 ,  69   4  opposite one another. The guide lugs  34   1 - 34   N  may have various other shapes in other embodiments. 
     Each guide lug  34   n  comprises elastomeric material  67 . The elastomeric material  67  can be any polymeric material with the property of elasticity. More particularly, in this embodiment, the elastomeric material  67  includes rubber. Various rubber compounds may be used and, in some cases, different rubber compounds may be present in different areas of the guide lug  34   n . In other embodiments, the elastomeric material  67  may include another elastomer in addition to or instead of rubber (e.g., polyurethane elastomer). 
     The guide lugs  34   1 - 34   N  are provided with wear protectors  50   1 - 50   N  for protecting them against wear due to their motion relative to the wheels  24 ,  26 ,  28   1 - 28   R . Without the wear protectors  50   1 - 50   N , as the guide lugs  34   1 - 34   N  move relative to the wheels  24 ,  26 ,  28   1 - 28   R , the guide lugs  34   1 - 34   N  could come into contact with one or more of the wheels  24 ,  26 ,  28   1 - 28   R  and this contact could wear out their rubber  67 . For instance, as each guide lug  34   n  would pass in the space  31  between the wheel portions  29   1 ,  29   2  of the drive wheel  24 , one or both of the side surfaces  69   2 ,  69   4  of the guide lug  34   n  could rub against or otherwise frictionally contact inner surfaces of the wheel portions  29   1 ,  29   2 . This frictional contact could be particularly strong when the construction vehicle  10  is turning or moving on a hill or other sloped terrain. Over time, such frictional contact would wear out the rubber  67  of each of the guide lugs  34   1 - 34   N , possibly to a point where the guide lugs  34   1 - 34   N  are so degraded that the endless track  22  could no longer be used efficiently and would have to be repaired or replaced. In some cases, such degradation of the guide lugs  34   1 - 34   N  could occur although the carcass  36  of the endless track  22  remains in acceptable condition. In other words, the guide lugs  34   1 - 34   N  could wear out at a significantly greater rate than the carcass  36  of the endless track  22 . However, by virtue of the wear protectors  50   1 - 50   N , such undesirable wear of the guide lugs  34   1 - 34   N  can be significantly reduced if not prevented altogether. 
     With additional reference to  FIGS. 7 to 10 , in this embodiment, each wear protector  50   n  (1≦n≦N) comprises a cover  52  mountable on the periphery  70  of the guide lug  34   n  and a fastener  54  for fastening the cover  52  to the guide lug  34   n . The guide lug  34   n  comprises a cavity  60  used in connection with the wear protector  50   n . In this case, the cavity  60  extends through the guide lug  34   n  from the side surface  69   2  to the side surface  69   4 . The cavity  60  may be created when the guide lug  34   n  is molded or thereafter (e.g., by drilling). 
     The cover  52  is shaped to cover at least part of the periphery  70  of the guide lug  34   n . More particularly, in this embodiment, the cover  52  comprises a first covering portion  56   1  for covering at least part of the side surface  69   2  of the guide lug  34   n  and a second covering portion  56   2  for covering at least part of the side surface  69   4  of the guide lug  34   n . In this case, the first covering portion  56   1  and the second covering portion  56   2  are two (2) covering members that are separate from one another and noncontiguous. This allows protection of the side surfaces  69   2 ,  69   4  of the guide lug  34   n  while minimizing a weight of the cover  52 . 
     The covering member  56   1  covers the side surface  69   2  of the guide lug  34   n  such that it is interposed between the side surface  69   2  and the wheels  24 ,  26 ,  28   1 - 28   R . In this way, as the guide lug  34   n  moves relative to the wheels  24 ,  26 ,  28   1 - 28   R , the covering member  56   1  may come into contact with these wheels and thus preclude contact between the side surface  69   2  of the guide lug  34   n  and these wheels. In turn, this reduces wearing of the rubber  67  of the guide lug  34   n . 
     Various materials may be used for the covering member  56   1 . For example, in some embodiments, the covering member  56   1  may comprise material having an abrasion resistance greater than that of the rubber  67  of the guide lug  34   n . The material of the covering member  56   1  may also have other desirable properties, such as a low coefficient of friction with the wheels  24 ,  26 ,  28   1 - 28   R . For instance, in some cases, the covering member  56   1  may comprise rigid polymeric material (e.g., ultra-high molecular weight polyethylene (UHMWPE)), metallic material, or composite material. 
     The covering member  56   1  may be designed to resist forces exerted on it to restrain its movement relative to the guide lug  34   n  when it comes into contact with one of more of the wheels  24 ,  26 ,  28   1 - 28   R  as the track  22  is in motion. 
     For example, in this embodiment, the covering member  56   1  overlaps part of the top surface  72 , the front surface  69   1 , and the rear surface  69   3  of the guide lug  34   n . Thus, the covering member  56   1  is essentially “saddled” on the guide lug  34   n . In other cases, the covering member  56   1  may overlap part of only one or two of the top surface  72 , the front surface  69   1 , and the rear surface  69   3  of the guide lug  34   n . 
     Also, in this embodiment, the covering member  56   1  comprises a protrusion  64  that projects away from an external surface  66  of the covering member  56   1  and is positioned within the cavity  60  of the guide lug  34   n  to help retain the covering member  56   1  in place on the guide lug  34   n . The protrusion  64  can restrain movement of the covering member  56   1  relative to the guide lug  34   n  in each of two or more directions. For example, in this case, the protrusion  64  can restrain movement of the covering member  56   1  relative to the guide lug  34   n  in a thickness direction of the endless track  22  (i.e., a generally vertical direction normal to both the longitudinal direction and the lateral direction of the endless track  22 ) and in various transversal directions of the endless track  22 , including its lateral direction. 
     The protrusion  64  may be shaped in various ways in various embodiments. For instance, in this embodiment, the protrusion  64  has a shape complementary to a shape of the cavity  60  of the guide lug  34   n . More particularly, in this embodiment, the cavity  60  comprises a first tapering cavity portion  61   1  at a first end of the cavity  60 , a second tapering cavity portion  61   2  at a second end of the cavity  60 , and an intermediate cavity portion  63  between the tapering cavity portions  61   1 ,  61   2 . The protrusion  64  is positioned in the tapering cavity portion  61   1  and has a tapering shape complementary to the tapering cavity portion  61   1 . In this case, the protrusion  64  and the tapering cavity portion  61   1  have complementary generally truncated conical shapes. 
     The covering member  56   1  comprises an aperture  74  for admitting the fastener  54  fastening the cover  52  to the guide lug  34   n . More particularly, in this embodiment, the aperture  74  extends from the external surface  66  to an internal surface  68  of the covering member  56   1  through the protrusion  64 . The aperture  74  comprises a first aperture portion  75   1  extending inwardly from the external surface  66  and a second aperture portion  75   2  extending from the first aperture portion  75   1  to the internal surface  68 . The first aperture portion  75   1  is larger in cross-section than the second aperture portion  75   2  in order to accommodate an end portion of the fastener  54  such that this end portion does not extend beyond the external surface  66  when the fastener  54  fastens the cover  52  to the guide lug  34   n . For instance, as in this example, the first aperture portion  75   1  may be a counterbore or countersink. 
     In this embodiment, the covering member  56   1  is shaped to prevent it from interfering or at least reduce any interference with the carcass  36  as the carcass  36  bends around the wheels  24 ,  26 ,  28   1 - 28   R . More particularly, in this embodiment, the covering member  56   1  has a curved bottom edge  51  allowing the carcass  36  to bend around the wheels  24 ,  26 ,  28   1 - 28   R  without engaging the covering member  56   1 . Also, in this case, the covering member  56   1  has a bottom part  44  that thins down towards the bottom edge  51  to allow a more gradual load distribution at a base of the guide lug  34   n , thereby reducing the potential for cracks to develop at the base of the guide lug  34   n  where most stress concentrations take place (e.g., over time, the base of the guide lug  34   n  may slightly deform under load and acquire a shape conforming to a bottom part of the covering member  56   1 ). 
     The covering member  56   2  is configured similarly to the covering member  56   1  and covers the side surface  69   4  of the guide lug  34   n  such that it is interposed between the side surface  69   4  and the wheels  24 ,  26 ,  28   1 - 28   R . 
     The fastener  54  may comprise any device or group of devices capable of being used to fasten the cover  52  to the guide lug  34   n . For example, in various embodiments, the fastener  54  may comprise one or more of a threaded fastener (e.g., a bolt or stud with a nut, a screw, etc.), a cable (e.g., a cord or wire rope including a plurality of strands or wires, etc.), or any other hardware capable of being used to fasten the cover  52  to the guide lug  34   n . 
     In this embodiment, the fastener  54  fastens the cover  52  to the guide lug  34   n  such that the fastener  54  extends inside the guide lug  34   n  and is capable of being put in a state of tension. For example, in this embodiment, the fastener  54  comprises a first retaining portion  55   1  and a second retaining portion  55   2  spaced apart from one another and an elongated portion  57  extending between the retaining portions  55   1 ,  55   2  inside the guide lug  34   n . The retaining portions  55   1 ,  55   2  are positionable (e.g., by a tightening action) relative to one another such that the elongated portion  57  is put under tension. This state of tension of the fastener  54  may enhance retention of the cover  52  on the guide lug  34   n  (e.g., by allowing some preload). Also, this state of tension may allow the cover  52  to compress part of the rubber  67  of the guide lug  34   n . Such a state of compression of the rubber  67  may increase its durability. For instance, this state of compression may be such that, in use, the rubber  67  of the guide lug  34   n  does not experience a stress cycle that alternates between tensile and compressive stresses, but rather remains in the compression stress domain. This can hinder crack propagation and thus enhance a fatigue resistance of the rubber  67  of the guide lug  34   n . Putting the fastener  54  under tension may thus enhance the efficiency of the wear protector  50   n  in protecting the guide lug  34   n . While the fastener  54  is capable of being put in a state of tension, it may be decided in some cases to not put the fastener  54  in such a state of tension. 
     More particularly, in this embodiment, the fastener  54  fastens the covering members  56   1 ,  56   2  to the guide lug  34   n  by extending inside the guide lug  34   n  and interconnecting the covering members  56   1 ,  56   2 . The fastener  54  comprises a bolt  32  and an internally threaded element  33  (e.g., a nut or threaded insert) to which the bolt  32  is secured. Thus, in this case, a head of the bolt  32  and the internally threaded element  33  constitute the retaining portions  55   1 ,  55   2  of the fastener  54 , while a shank of the bolt  32  constitutes the elongated portion  57  of the fastener  54 . 
     When the wear protector  50   n  is installed on the guide lug  34   n , each of the covering members  56   1 ,  56   2  is placed on the guide lug  34   n  such that it covers one of the side surfaces  69   2 ,  69   4  of the guide lug  34   n , overlaps part of the top surface  72 , the front surface  69   1 , and the rear surface  69   3  of the guide lug  34   n , and has its protrusion  64  positioned within the cavity  60  of the guide lug  34   n . The bolt  32  is inserted through the aperture  74  of each of the covering members  56   1 ,  56   2  and is secured in place by being screwed into the internally threaded element  33 . The head of the bolt  32  is positioned in the counterbore  75   1  of the covering member  56   1  and the internally threaded element  33  is positioned in the counterbore  75   1  of the covering member  56   2 , thereby preventing the head of the bolt  32  and the internally threaded element  33  from projecting beyond the external surface  66  of each of these covering members and contacting one or more of the wheels  24 ,  26 ,  28   1 - 28   R . The bolt  32  may be placed in a state of tension by further screwing it into the internally threaded element  33 . This may be continued to increase pressure applied by the covering members  56   1 ,  56   2  on the rubber  67  of the guide lug  34   n  so as to put at least part of the rubber  67  in a state of compression. 
     The wear protectors  50   1 - 50   N  thus provide an efficient way of protecting the guide lugs  34   1 - 34   N  against wear due to their motion relative to the wheels  24 ,  26 ,  28   1 - 28   R . 
     The wear protectors  50   1 - 50   N  may be configured in various other ways in other embodiments. 
     For example, in other embodiments, the cover  52  of the wear protector  50   n  may have various other shapes to protect different portions of the periphery  70  of the guide lug  34   n . In particular, in other embodiments, the cover  52  may cover a greater part (including all) or a lesser part of the periphery  70  of the guide lug  34   n . For instance, in some cases, the cover  52  may cover the top surface  72 , front surface  69   1 , rear surface  69   3  and side surfaces  69   2 ,  69   4  of the guide lug  34   n . 
     As another example, in some embodiments, instead of extending between the side surfaces  69   2 ,  69   4  of the guide lug  34   n , the cavity  60  of the guide lug  34   n  may extend from the front surface  69   1  to the rear surface  69   3  of the guide lug  34   n , in which case the cover  52  may comprise covering portions (similar to the covering portions  56   1 ,  56   2 ) that cover at least part of these front and rear surfaces of the guide lug  34   n  and that have protrusions (similar to the protrusion  64  of each of the covering portions  56   1 ,  56   2 ) positionable within the cavity  60  to help retain the cover  52  in place on the guide lug  34   n . 
     As another example, instead of constituting two separate and noncontiguous covering members  56   1 ,  56   2 , in some embodiments, the first covering portion  56   1  and the second covering portion  56   2  may be part of a one-piece covering member. For instance, in some cases, the one-piece covering member may cover the top surface  72 , front surface  69   1 , rear surface  69   3  and side surfaces  69   2 ,  69   4  of the guide lug  34   n . 
     As yet another example, the fastener  54  may comprise any other device or group of devices capable of being used to fasten the cover  52  to the guide lug  34   n . For instance, in some embodiments, the fastener  54  may comprise a cable and a pair of fittings (e.g., rings) mounted to the cable, in which case the fittings constitute the retaining portions  55   1 ,  55   2  of the fastener  54  and the cable constitutes the elongated portion  57  of the fastener  54 . As yet another example, the wear protector  50   n  may comprise more than one fastener such as the fastener  54  to fasten the cover  52  to the guide lug  34   n . 
     As yet another example, in some embodiments, the wear protectors  50   1 - 50   N  may be designed to prevent one or more of the wheels  24 ,  26 ,  28   1 - 28   R  from jumping on top of the guide lugs  34   1 - 34   N  (e.g., due to terrain irregularities and/or motion of the construction vehicle  10 ). For instance, a top part  59  of the cover  52  may extend by a certain distance above the top surface  72  of the guide lug  34   n  to prevent one or more of these wheels from jumping on top of the guide lug  34   n . 
     Although in this embodiment the track-directing projections  34   1 - 34   N  are guide lugs, in other embodiments, the track-directing projections  34   1 - 34   N  may be drive projections, referred to as “drive lugs”, which interact with the drive wheel  24  in order to move the endless track  22  around the wheels  24 ,  26 ,  28   1 - 28   R  and which are protected against wear by wear protectors such as the wear protectors  50   1 - 50   N . For instance, in such embodiments, the drive wheel  24  may comprise a drive sprocket including teeth or bars and the drive lugs  34   1 - 34   N  interact with the teeth or bars of the drive wheel  24  in order to cause the endless track  22  to move around the wheels  24 ,  26 ,  28   1 - 28   R . The drive lugs  34   1 - 34   N  may also serve to guide the endless track  22  as it is driven around the wheels  24 ,  26 ,  28   1 - 28   R . 
     While in this embodiment the endless track  22  is a one-piece jointless track, in other embodiments, the endless track  22  may be a “segmented” track comprising a plurality of track sections connected to one another at a plurality of joints. In yet other embodiments, the endless track  22  may be a one-piece track that can be closed like a belt with connectors at both of its longitudinal ends to form a joint. 
     The track assembly  16 ; may be configured in various other ways in other embodiments. For example, in some embodiments, the track assembly  16 ; may comprise a front drive wheel (e.g., the idler wheel  26  may be replaced by a drive wheel) instead of or in addition to the drive wheel  24 . As another example, in some embodiments, the track assembly  16 ; may comprise more or less roller wheels such as the roller wheels  28   1 - 28   R . As yet another example, rather than have a generally oblong configuration as in this embodiment, in other embodiments, the track assembly  16 ; may have various other configurations (e.g., a generally triangular configuration). 
     While in embodiments considered above the off-road vehicle  10  is a construction vehicle for performing construction work, in other embodiments, the off-road vehicle  10  may be an agricultural vehicle (e.g., a harvester, a combine, a tractor, etc.) for performing agricultural work, a forestry vehicle (e.g., a feller-buncher, a tree chipper, a knuckleboom loader, etc.) for performing forestry work, a military vehicle (e.g., a combat engineering vehicle (CEV), etc.) for performing work in a military application, a transporter vehicle (e.g., a heavy hauler, a flatbed truck, a trailer, a carrier, etc.) for transporting equipment, materials, cargo or other objects, or any other vehicle operable off paved roads. Although operable off paved roads, an off-road vehicle may also be operable on paved roads in some cases. Also, while in embodiments considered above the off-road vehicle  10  is driven by a human operator in the vehicle  10 , in other embodiments, the off-road vehicle  10  may be an unmanned ground vehicle (e.g., a teleoperated or autonomous unmanned ground vehicle). 
     Although various embodiments and examples have been presented, this was for the purpose of describing, but not limiting, the invention. Various modifications and enhancements will become apparent to those of ordinary skill in the art and are within the scope of the invention, which is defined by the appended claims.