Patent Publication Number: US-2021163085-A1

Title: Interchangeable Track Systems

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. provisional application No. 62/942,434, filed Dec. 2, 2019 and entitled INTRCHANGEABLE TRACK SYSTEMS, which provisional application is hereby incorporated by reference herein in its entirety. 
    
    
     FIELD 
     Illustrative embodiments of the disclosure relate to forestry harvester vehicles used for felling, delimbing and buckling trees. More particularly, illustrative embodiments of the disclosure relate to axle-mounted interchangeable track systems which facilitate interchangeable attachment of tracks and wheels on a forestry harvester vehicle to provide higher ground clearance, lower stabilizing center of gravity, facilitate less destructive and yet more aggressive traction properties and lower ground pressure for wet, soft or irregular terrain. 
     BACKGROUND 
     The background description provided herein is solely for the purpose of generally presenting the context of the illustrative embodiments of the disclosure. Aspects of the background description are neither expressly nor impliedly admitted as prior art against the claimed subject matter. 
     In the forestry industry, jobsite production is frequently inhibited by negative impact to property, accessibility during and after weather events, and equipment limitations in severely saturated soil and/or extreme elevation changes. Soft, wet soil conditions are often unable to adequately support the weight and traffic of conventionally configured machinery without excessive work area degradation and machine wear. Consequently, damage to the environment and stress to equipment occurs, frequently causing jobsites to shut down. Under adverse conditions, work must be limited, relocated, postponed or cancelled. Certain lowland areas may be rendered permanently inaccessible. 
     SUMMARY 
     Illustrative embodiments of the disclosure are generally directed to interchangeable track systems for interchangeable deployment with vehicle wheels on a forestry harvester vehicle having a front axle and a rear axle. An illustrative embodiment of the interchangeable track systems may include a pair of front roller frame mount arms and a pair of rear roller frame mount arms configured for mounting on the front axle and the rear axle, respectively, of the forestry harvester vehicle. A pair of front track assemblies and a pair of rear track assemblies may be configured for removable mounting on the pair of front roller frame mount arms and the pair of rear roller frame mount arms, respectively. Each of the pair of front track assemblies and the pair of rear track assemblies may include an elongated roller frame configured for pivotal attachment to each corresponding one of the pair of front roller frame mount arms and pair of rear roller frame mount arms. A front idler roller and a rear idler roller may be carried by the roller frame. A track may be trained on the front idler roller and the rear idler roller. A sprocket may be configured for driving engagement by a corresponding one of the front axle and the rear axle, with the sprocket drivingly engaging the track. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Illustrative embodiments of the disclosure will now be described, by way of example, with reference to the accompanying drawings, in which: 
         FIG. 1  is a right hand rearward side perspective view of a forestry harvester vehicle with an illustrative embodiment of the interchangeable track systems fitted on the vehicle; 
         FIG. 2  is a side view of the forestry harvester vehicle with interchangeable track system illustrated in  FIG. 1 ; 
         FIG. 3  is a side view of the forestry harvester vehicle with interchangeable track system, with the track removed from each track assembly on the vehicle and the track assembly disposed in a pivoted configuration relative to the chassis of the vehicle; 
         FIG. 4  is a top view of the forestry harvester vehicle with the illustrative interchangeable track system, with the front track assemblies oriented in a straight position relative to the rear track assemblies of the system; 
         FIG. 5  is a top view of the forestry harvester vehicle with the front track assemblies steered to the left relative to the rear track assemblies of the system; 
         FIG. 6  is a side view of a typical rear track assembly of the system with the track removed from the assembly for clarity; 
         FIG. 7  is a front view of a pair of front track assemblies mounted on the front axle of the vehicle in typical application of the interchangeable track system; 
         FIG. 8  is a front view of the front axle of the vehicle with one vehicle wheel mounted on one end of the front axle and a front track assembly mounted on the other end of the front axle and engaging level ground; 
         FIG. 9  is a front perspective view of a typical rear track assembly of the interchangeable track system, deployed on the rear axle of the forestry harvester vehicle; 
         FIG. 10  is a top view of a pair of rear track assembly mounting plates (pivot shafts extended) and connector rods of the interchangeable track system deployed on the rear axle of the vehicle; 
         FIG. 11  is a front view of a pair of front track mounting plates (pivot shafts extended) of the interchangeable track system with a pair of connecting rods (one rearmost of which is hidden) connecting the front track assembly mounting plates; 
         FIG. 12  contrasts an exploded front view of the interchangeable track system, more particularly illustrating a typical one-step method of deploying the system on and removing the system from the front axle of the forestry harvester vehicle; 
         FIG. 13  is a side view of a typical front roller frame mount arm of an assembled front arm mount assembly on a front track assembly of the interchangeable track system, with the front roller frame mount arm fastened to on the front axle of the vehicle: 
         FIG. 14  is a side view of a typical rear roller frame mount arm of an assembled rear arm mount assembly on a rear track assembly of the interchangeable track system, with the rear roller frame mount arm fastened to on the rear axle of the vehicle; 
         FIG. 15  is a side view of the roller frame mount arm of the disassembled front arm mount assembly, unfastened and removed from the front axle of the vehicle, with the connector and camber plates remaining in place for later redeployment of the system on the vehicle; 
         FIG. 16  is a side view of the roller frame mount arm of the disassembled rear arm mount assembly, unfastened and removed from the rear axle of the vehicle, with the connector and camber plates remaining in place for later redeployment of the system on the vehicle; 
         FIG. 17  is a top view (lower figure) and end view (upper figure) of a typical left-hand tapered camber block spacer of each of the front arm mount assembly and the rear arm mount assembly; 
         FIG. 18  is a top view (lower figure) and end view (upper figure) of a typical right-hand tapered camber block spacer of each of the front arm mount assembly and the rear arm mount assembly; 
         FIG. 19  is a top view (lower figure) and end view (upper figure) of a typical left-hand connector block used to connect the left tapered camber block spacer to the roller frame mount arm; 
         FIG. 20  is a top view (lower figure) and end view (upper figure) of a typical right-hand connector block used to connect the right tapered camber block spacer to the roller frame mount arm: 
         FIG. 21  is an exploded top view of a typical skid pan assembly of the interchangeable track system; 
         FIG. 22  is a top view of the skid pan assembly deployed on the front axle of the forestry harvester vehicle; 
         FIG. 23  is a top view of the assembled skid pan assembly with the front axle of the forestry harvester vehicle omitted for clarity; 
         FIG. 24  is an end view of the assembled skid pan assembly illustrated in  FIG. 23 ; 
         FIG. 25  contrasts an exploded front view of the rear interchangeable track system, more particularly illustrating an alternative, two-step method of deploying the system on and removing the system from the front axle of the forestry harvester vehicle; and 
         FIG. 26  is a front view of the front axle of the vehicle with one vehicle wheel mounted on one end of the front axle and a front track assembly mounted on the other end of the front axle and engaging sloped ground, and further illustrating higher ground clearance on the track side relative to the wheel side of the vehicle. 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description is merely exemplary in nature and is not intended to limit the described embodiments or the application and uses of the described embodiments. As used herein, the word “exemplary” or “illustrative” means “serving as an example, instance, or illustration.” Any implementation described herein as “exemplary” or “illustrative” is not necessarily to be construed as preferred or advantageous over other implementations. All of the implementations described below are exemplary implementations provided to enable persons skilled in the art to make or use the embodiments of the disclosure and are not intended to limit the scope of the disclosure, which is defined by the claims. For purposes of description herein, the terms “upper”, “lower”, “left”, “rear”, “right”, “front”, “vertical”, “horizontal”, and derivatives thereof shall relate to the invention as oriented in  FIG. 1 . Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description. It is also to be understood that the specific devices and processes illustrated in the attached drawings, and described in the following specification, are simply exemplary embodiments of the inventive concepts defined in the appended claims. Hence, specific dimensions and other physical characteristics relating to the embodiments disclosed herein are not to be considered as limiting, unless the claims expressly state otherwise. 
     Referring to the drawings, an illustrative embodiment of the interchangeable track system is generally indicated by reference numeral  1 . As illustrated in  FIGS. 1-3  and will be hereinafter further described, the interchangeable track system  1  may be configured for deployment on a forestry harvester vehicle  66  which may be used for felling, delimbing and buckling trees. The forestry harvester vehicle  66  may have a standard or conventional design with a vehicle chassis  67  and a cab  68 , a rear axle  69  and a front axle  70  on the vehicle chassis  67 . As illustrated in  FIG. 1 , a boom-operated grapple  71  may be provided on a rear end of the vehicle chassis  67  for grasping, lifting, gathering and carrying cut tree segments  76 . In some applications, a push blade  72  may be provided on a front end of the vehicle chassis  67  for pushing and moving earth, logs, tree segments and other materials. Other forestry harvester vehicles may be provided with front-mounted, powered saws or shear heads for performing the tree cutting and felling operations. 
     As further illustrated in  FIGS. 1-3 , the interchangeable track system  1  may include a pair of rear track assemblies  2   a  and a pair of front track assemblies  2   b  mounted on the rear axle  69  and the front axle  70 , respectively, of the forestry harvester vehicle  66 . The rear track assemblies  2   a  and the front track assemblies  2   b  may be mounted in interchangeable relationship with respect to the vehicle wheels  74  (one of which is illustrated in  FIG. 8 ) on the rear axle  69  and the front axle  70 . Also illustrated in  FIG. 8  is the additional ground clearance gained by deployment of the interchangeable track system  1 , comparing a front track assembly  2   b  mounted on the left to a standard or conventional vehicle wheel  74  mounted on the right of the front axle  70 . Lower center of gravity may also be realized using this comparison. Accordingly, the rear track assemblies  2   a  and the front track assemblies  2   b  may enable the forestry harvester vehicle  66  to traverse soft soil and other terrain which may not be feasible by traversing the terrain with the vehicle wheels  74 . Additionally, the rear track assemblies  2   a  and the front track assemblies  2   b  may enable the forestry harvester vehicle  66  to traverse steep terrain in the felling of timber and retrieval and transport of the cut tree segments  76 . The rear track assemblies  2   a  and the front track assemblies  2   b  of the interchangeable track system  1  may thus be mounted on the forestry harvester vehicle  66  in interchangeable relationship with respect to the vehicle wheels  74  ( FIG. 8 ) depending on which is optimal to enable the forestry harvester vehicle  66  to traverse the terrain for a particular application. As illustrated in  FIGS. 4 and 5 , the interchangeable track system  1  may enable independent steering of the rear track assemblies  2   a  relative to the front track assemblies  2   b  throughout operation of the forestry harvester vehicle  66 . 
     Each rear track assembly  2   a  and each front track assembly  2   b  may include an elongated roller frame  3 . The roller frame  3  may have a front roller frame end  4  and a rear roller frame end  5 . As illustrated in  FIG. 6 , a front roller arm  1  and a rear roller arm  17  may be mounted on the roller frame  3  according to the knowledge of those skilled in the art. A front idler roller  10  may be journaled for rotation on the front roller arm  11  at the front roller frame end  4  of the roller frame  3 . A rear idler roller  16  may be journaled for rotation on the rear roller arm  17  at the rear roller frame end  5  of the roller frame  3 . On each rear track assembly  2   a , a hydraulic track adjuster/recoil spring assembly unit  12  may engage the rear roller arm  17  to bias the rear idler roller  16  rearwardly. On each front track assembly  2   b , a hydraulic track adjuster/recoil spring assembly unit  12  may in like manner engage the front roller arm  11  to bias the front idler roller  10  forwardly. A plurality of spaced-apart bottom rollers  20  may be mounted on the roller frame  3  between the front roller arm  11  and the rear roller arm  17 . As illustrated in  FIG. 6 , a pivot shaft opening  8  may extend laterally through the roller frame  3  substantially equidistant between the front roller frame end  4  and the rear roller frame end  5  at the center of gravity of the roller frame  3  for purposes which will be hereinafter described. 
     An endless track  62  may be trained around the front idler roller  10 , the rear idler roller  16  and the bottom rollers  20 . The track  62  may be fabricated of steel and may have a standard or conventional track design or construction, 
     A roller frame mount arm  24  may pivotally mount the roller frame  3  of each rear track assembly  2   a  and each front track assembly  2   b  to the corresponding end of the rear axle  69  or front axle  70 , respectively, of the forestry harvester vehicle  66  typically at the pivot shaft opening  8 . As illustrated in  FIGS. 7, 9 and 25 , a pair of rear roller frame mount arms  24   a  ( FIGS. 9 and 25 ) may mount the roller frames  3  of the rear track assemblies  2   a  to the respective ends of the rear axle  69 . In like manner, a pair of front roller frame mount arms  24   b  ( FIG. 7 ) may mount the roller frames  3  of the front track assemblies  2   b  to the respective ends of the front axle  70 . As illustrated in  FIG. 25 , each rear roller frame mount arm  24   a  (and each front roller frame mount arm  24   b , not shown) may include a pivoting shaft frame  25 . As illustrated in  FIGS. 13 and 15 , the shaft frame  25  of each front roller frame mount arm  24   b  may be generally elongated and rectangular. As illustrated in  FIGS. 14 and 16 , the shaft frame  25  of each rear roller frame mount arm  24   a  may have a parallelogram shape. A pair of rod eyes  26  may extend from the opposite front and rear sides of each shaft frame  25  for purposes which will be hereinafter described. 
     As illustrated in  FIG. 7 , each rear track assembly  2   a  and each front track assembly  2   b  may include a sprocket  60  which is releasably and drivingly engaged for rotation by the corresponding rear axle  69  and front axle  70 . The sprocket  60  may be drivingly coupled to the corresponding rear axle  69  or front axle  70  according to any suitable technique known by those skilled in the art. In some embodiments, the sprocket  60  may be attached to the standard or conventional wheel attachment interface  61  on the rear axle  69  and front axle  70  using a plurality of sprocket fasteners  64 . Accordingly, responsive to driving rotation by the rear axle  69  and front axle  70 , each sprocket  60  drivingly engages the track  62  of the corresponding rear track assembly  2   a  and front track assembly  2   b  to traverse the front idler roller  10 , the rear idler roller  16  and the bottom rollers  20  ( FIGS. 1-3 ). The rear idler roller  16  ( FIG. 6 ), biased by the hydraulic track adjuster/recoil spring assembly unit  12  via the rear roller arm  17 , may tension the track  62  via the rear roller arm  17 . In like manner, the front idler roller  10 , bias by its corresponding hydraulic track adjuster/recoil spring assembly unit  12  via the front roller arm  11 , may tension the track  62  via the front roller arm  11 . 
     As further illustrated in  FIG. 25 , an arm mount frame  27  may extend inwardly (toward the longitudinal midline of the forestry harvester vehicle  66 ) from the shaft frame  25 . The arm mount frame  27  may include a top frame plate  28  which may be substantially perpendicular to the plane of the shaft frame  25 . A pair of parallel, spaced-apart, front and rear side frame plates  29  may extend from the shaft frame  25  beneath the top frame plate  28 . 
     An elongated roller frame pivot mount shaft  32  may extend outwardly (away from the longitudinal midline of the forestry harvester vehicle  66 ) from the shaft frame  25 . A plurality of shaft mount plates  34  may extend between the shaft frame  25  and the roller frame pivot mount shaft  32  for shaft reinforcing purposes. The roller frame pivot mount shaft  32  may be suitably sized and configured to removably receive the companion pivot shaft opening  8  ( FIG. 6 ) in the corresponding roller frame  3  to pivotally mount the roller frame  3  on the roller frame pivot mount shaft  32 . A shaft cap  40  may be detachably attached to the extending or distal end of the roller frame pivot mount shaft  32  to secure or retain the roller frame  3  on the roller frame pivot mount shaft  32 . 
     As illustrated in  FIGS. 6, 13-16 and 25 , in some embodiments, a forklift insertion frame  36  may extend outwardly from the shaft frame  25  typically between the shaft mount plates  34  of each rear roller frame mount arm  24   a  and each front roller mount frame arm  24   b . The forklift insertion frame  36  may be suitably sized and configured to receive a forklift blade (not illustrated) on a forklift to facilitate raising and lowering of each corresponding rear track assembly  2   a  and front track assembly  2   b  in installation and removal of the interchangeable track system  1  on and from, respectively, the forestry harvester vehicle  66 , as will be hereinafter further described. 
     A pair of rear arm mount assemblies  44   a  may removably mount the rear roller frame mount arms  24   a  to the respective ends of the rear axle  69 . In like manner, a pair of front arm mount assemblies  44   b  may removably mount the front roller frame mount arms  24   b  to the respective ends of the front axle  70 . As illustrated in  FIGS. 10 and 13-20 , each rear arm mount assembly  44   a  and each front arm mount assembly  44   b  may include a pair of elongated, parallel, spaced-apart front and rear base mount blocks  45  which may rest on the top frame plate  28  of the arm mount frame  27  on each corresponding rear arm mount assembly  44   a  and front arm mount assembly  44   b . As illustrated in  FIGS. 13-16 , a plurality of block fasteners  46  with securing nuts  47  may secure the top frame plate  28  to each base mount block  45 . A left camber block spacer  50  and a right camber block spacer  51  may be provided on the respective base mount blocks  45 . As illustrated in  FIGS. 17-20 , a plurality of spaced-apart axle mount fastener openings  52  may extend through each of the left camber block spacer  50  and the right camber block spacer  51 . The axle mount fastener openings  52  may align or register with respective base mount block openings (not illustrated) in each corresponding underlying base mount block  45 . Accordingly, a plurality of axle fasteners  54  may be extended through respective axle fastener openings (not illustrated) in the corresponding rear axle  69  and front axle  70  and secured with nuts (not illustrated). Accordingly, as illustrated in  FIGS. 13-16 , in some applications, each rear roller frame mount arm  24   a  ( FIG. 9 ) and each front roller frame arm  24   b  ( FIG. 7 ) may be removed from the corresponding rear axle  69  and front axle  70  by unfastening the securing nuts  47  from the respective block fasteners  46 . As illustrated in  FIGS. 15 and 16 , the rear roller frame mount arm  24   a  ( FIG. 9 ) and the front roller mount frame arm  24   b  ( FIG. 7 ) may then be lowered from the corresponding rear axle  69  and front axle  70  as the base mount blocks  45 , the left camber block spacer  50  and the right camber block spacer  51  typically remain attached to the rear axle  69  and front axle  70 . 
     As illustrated in  FIGS. 7, 9-12 and 25 , in some embodiments, two connecting rods  56 , one front and one rear, may connect the front roller frame mount arms  24   b  of the respective front track assemblies  2   b  to each other and the rear roller frame mount arms  24   a  of the respective rear track assemblies  2   a  to each other. In some embodiments, a pair of connecting rods  56  may connect the rear roller frame mount arms  24   a  to each other in front of and behind, respectively, the rear axle  69 . In like manner, a pair of connecting rods  56  may connect the front roller frame mount arms  24   b  to each other in front of and behind, respectively, the front axle  70 . Rod threads  57  may terminate the respective ends of each connecting rod  56 . Accordingly, each threaded end of each connecting rod  56  may be inserted through a rod eye  26  ( FIGS. 13-16 ) on the shaft frame  25  of each corresponding rear roller frame mount arm  24   a  and front roller frame mount arm  24   b . Nuts  58  may be threaded on the rod threads  57  to secure each end of each connecting rod  56  in the corresponding rod eye  26 . 
     As illustrated in  FIGS. 9 and 21-24 , in some embodiments, a skid pan assembly  78  may be deployed in place beneath the connecting rods  56  which connect the rear track assemblies  2   a  to each other and the front assemblies  2   b  to each other on the rear axle  69  and the front axle  70 . The skid pan assembly  78  may extend beneath the corresponding rear axle  69  and front axle  70  to protect the vehicle differential  90  ( FIG. 24 ) and other under-components of the vehicle chassis  67 . The skid pan assembly  78  may include an elongated skid pan  79 . A pair of front and rear pan flanges  80  may angle upwardly from the skid pan  79 . A pair of end pan flanges  81  may extend from opposite ends of the skid pan  79 . As illustrated in  FIG. 21 , a pair of pan mount brackets  84 , typically having flange fastener openings  85 , may secure the end pan flanges  81  of the skid pan  79  to the respective rear roller frame mount arms  24   a  and front roller mount frame arms  24   b  or other component of each corresponding pair of rear track assemblies  2   a  and front track assemblies  2   b . As illustrated in  FIGS. 9 and 24 , a connecting rod clamp plate  92  may secure each front and rear pan flange  80  of each skid pan  79  to each corresponding connecting rod  56 . The connecting rod clamp plate  92  may be secured to the corresponding front or rear pan flange  80  using a pair of clamp plate fasteners  93 . 
     As illustrated in  FIGS. 22-24 , an elongated differential guard support member  88  may extend upwardly from the skid pan  79 . A differential guard panel  89  may be supported by the differential guard support member  88 . Accordingly, in the installed skid pan assembly  78 , the differential guard panel  89  may be situated beneath the vehicle differential  90  of the forestry harvester vehicle  66  to impart additional protection to the vehicle differential  90 . 
     In typical application, the interchangeable track assembly  1  can be deployed on the forestry harvester vehicle  66  in interchangeable relationship to the vehicle wheels  74  ( FIG. 8 ) depending on the type of soil or terrain which the forestry harvester vehicle  66  will traverse during the logging operation. Some types of soil or terrain may be better suited to use of the vehicle wheels  74 . Accordingly, as illustrated in  FIG. 8 , the vehicle wheels  74  may be coupled to the rear axle  69  ( FIG. 9 ) and the front axle  70  typically at the wheel attachment interface  61  ( FIGS. 7 and 10 ) using lug bolts and nuts or the like. 
     In some applications, the rear roller frame mount arm  24   a  and the front roller frame mount arm  24   b  of each corresponding rear track assembly  2   a  and front track assembly  2   b  may remain attached to the corresponding end of the rear axle  69  and front axle  70  with either the vehicle wheels  74  or the rear track assemblies  2   a  and front track assemblies  2   b  of the interchangeable track system  1  deployed on the forestry harvester vehicle  66 . Each rear roller frame mount arm  24   a  and each front roller frame mount arm  24   b  may be mounted on the corresponding rear axle  69  and front axle  70  by assembly of the corresponding rear arm mount assembly  44   a  and front arm mount assembly  44   b , typically as was heretofore described with respect to  FIGS. 13-20 . 
     In the event that the interchangeable track assembly  1  is deemed more suitable for traversing some types of soil or terrain than the vehicle wheels  74 , the vehicle wheels  74  may initially be removed from the respective wheel attachment interfaces  61  on the rear axle  69  and front axle  70 . The sprocket  60  may be attached to the wheel attachment interface  61  on the rear axle  69  and the front axle  70  typically using the sprocket fasteners  64  as was heretofore described with respect to  FIGS. 7,12 and 25 . 
     A forklift (not illustrated) may then be used to raise each of the rear track assembly  2   a  and the front track assembly  2   b  and facilitate alignment or registration of the pivot shaft opening  8  ( FIG. 6 ) in each roller frame  3  with the roller frame pivot mount shaft  32  of each corresponding rear roller frame mount arm  24   a  and front roller frame mount arm  24   b . Engagement of the forklift with the rear track assembly  2   a  or front track assembly  2   b  may be carried out by extending the forklift blade on the forklift into the forklift insertion frame  36  on the rear roller frame mount arm  24   a  or front roller frame mount arm  24   b . The forklift may then be operated to move the rear track assembly  2   a  or front track assembly  2   b  medially (toward the longitudinal midline of the forestry harvester vehicle  66 ) until the roller frame pivot mount shaft  32  inserts through the pivot shaft opening  8  in the roller frame  3 . Simultaneously, the sprocket  60  may mesh with the track  62  for driving engagement. The shaft cap  40  may then be secured on the end of the roller frame pivot mount shaft  32  to retain the roller frame  3  thereon. 
     The forestry harvester vehicle  66  may be operated over soft, hilly or mountainous terrain to delimb and buckle trees typically using the grapple  71  ( FIG. 1 ) and the push blade  72  in the conventional manner. As illustrated in  FIG. 8 , the rear axle  69  (and front axle  70 ) may be disposed at a level orientation relative to the vehicle chassis  67  of the forestry harvester vehicle  66  as the rear track assemblies  2   a  and front track assemblies  2   b  traverse level terrain %. As illustrated in  FIG. 26 , at least the front axle  70  may be capable of pivoting vertically relative to the vehicle chassis  67 , typically via a chassis pivot point  73 , such that the front track assemblies  2   b  can engage sloped terrain  97 . As illustrated in  FIG. 3 , the roller frame  3  of each rear track assembly  2   a  and each front track assembly  2   b  may be capable of pivoting forwardly and rearwardly about the corresponding roller frame mount arm  24  to accommodate variations in the terrain during the forestry operation. As illustrated in  FIGS. 4 and 5 , because of the independent mounting of the rear track assemblies  2   a  and the front track assemblies  2   b  to the rear axle  69  and front axle  70 , respectively, the forestry harvester vehicle  66  is capable of steering without interference. In the event that the forestry harvester vehicle  66  rises and falls due to uneven terrain, the skid pan assembly  78  may protect the rear axle  69 , the front axle  70 , the vehicle differential  90  ( FIG. 24 ) and/or other under-components of the vehicle chassis  67  from damage or puncture by rocks, stumps and the like. 
     In the event that it is deemed necessary to remove the rear track assemblies  2   a  and the front track assemblies  2   b  of the interchangeable track system  1  from the forestry harvester vehicle  66  and deploy the vehicle wheels  74  on the rear axle  69  and the front axle  70 , the rear track assemblies  2   a  and the front track assemblies  2   b  may be removed from the respective rear roller frame mount arms  24   a  and front roller frame mount arms  24   b  typically by reversing the steps described above. 
     As illustrated in  FIG. 12 , in some applications, the rear roller frame mount arms  24   a  and the front roller frame mount arms  24   b  may be removed from the respective rear axle  69  and front axle  70  along with the rear track assemblies  2   a  and the front track assemblies  2   b . Accordingly, the forklift blade of a forklift may initially be extended into the forklift insertion frame  36  of each rear roller frame mount arm  24   a  and each front roller frame mount arm  24   b . As illustrated in  FIGS. 15 and 16 , the nuts  47  may be removed from the respective block fasteners  46  which attach the top frame plate  28  of each rear roller frame mount arm  24   a  and each front roller frame mount arm  24   b  to the front and rear base mount blocks  45  of the rear arm mount assembly  44   a  and the front arm mount assembly  44   b . The forklift may then be operated to lower the rear roller frame mount arm  24   a  or front roller mount frame arm  24   b  from the corresponding rear axle  69  or front axle  70 , and the vehicle wheels  74  may be replaced on the rear axle  69  and front axle  70  typically as was heretofore described. 
     It will be appreciated by those skilled in the art that the interchangeable track system  1  can be used to replace conventional round tires with substantially flattened ground-contouring steel track units that enhance power through overall gear ratio reduction. The resulting extra power eases stress on engine and powertrain components. Moreover, through the pivot shaft support system, vehicle weight is separated from the front and rear axle wheel bearings. A beneficial byproduct is the capability to transfer the tracked components into a new or different vehicle in the event that the vehicle is sold or retired. 
     It will be further appreciated by those skilled in the art that the interchangeable track system accomplishes all of the following through the design and implementation of its components: 
     A). greatly reduced ground pressure with added aggressive traction characteristics:
         a). reduced impact on forested land; and   b). greater ability to operate on steeply sloped jobsites.       

     B). higher ground clearance
         a). reduced contact with stumps and other obstacles.       

     C). lower center of gravity
         a). enables stability on extreme slopes, even traversed       

     D). Adaptability to transfer between other machines. 
     While certain illustrative embodiments of the disclosure have been described above. it will be recognized and understood that various modifications can be made to the embodiments and the appended claims are intended to cover all such modifications which may fall within the spirit and scope of the disclosure.