Abstract:
A testing machine tests the durability of backer pads on the track shoe assembly and the surface of the road wheel. The test machine utilizes two eccentric drives to move a section of a road wheel to simulate actual vehicle conditions. A positioning system positions the track shoe assembly with respect to the road wheel to adjust the loading between the two components.

Description:
FIELD 
       [0001]    The present disclosure relates to tracked vehicle track backer pads and road wheel tires. More particularly, the present disclosure relates to a test machine and method for testing the track backer pads and the road wheel tires. 
       BACKGROUND 
       [0002]    This section provides background information related to the present disclosure which is not necessarily prior art. 
         [0003]    Track backer pads and road wheel tires for tracked vehicles are currently fatigue tested primarily on the tracked vehicle itself. The tracked vehicle is equipped with the specified track backer pads and/or road wheel tires and the tracked vehicle is then driven through a representative fatigue course for a specified number of miles or a specified number of cycles through the representative fatigue course. 
         [0004]    Testing these components using the actual vehicle requires producing an entire track of track pitches which is very expensive and time consuming for experimental components. Once fitted on the actual vehicle, the test vehicle has to be driven around the representative fatigue course causing additional expense. While the actual use of a test vehicle is a realistic test, the testing is subjective and not repeatable because the actual vehicle test can be affected by the weather, the representative fatigue course deterioration, the driver and the other components on the tracked vehicle. 
         [0005]    Some shortened tracks are tested by being run on track-dynamometers but the use of a track dynamometer requires most of the track to be constructed and then requires a significant amount of energy to operate the track dynamometer. Some simplistic fatigue tests are run on individual components using hydraulic test machines but these simplistic tests do not apply representative stresses and strains to test the specimen in the loading characteristics the specimen would receive when in an actual vehicle. 
       SUMMARY 
       [0006]    This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features. 
         [0007]    The present disclosure provides a test machine and a testing method which economically tests the elastomer on a single track backer pad and/or on a single road wheel using stresses and strains which simulate actual vehicle stresses and strains. The test machine and test method will allow the materials for the backer pad and/or the road wheel to be tested one piece at a time in a testing lab using representative stresses and strains. This testing will be more responsive, less expensive and more repeatable than the testing that is currently being performed using actual tracked vehicles. 
         [0008]    Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
     
    
     
       DRAWINGS 
         [0009]    The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure. 
           [0010]      FIG. 1  is a perspective schematic view of a crawler track having track backer pads and road wheels; 
           [0011]      FIG. 2  is a perspective view of a road wheel illustrated in  FIG. 1 ; 
           [0012]      FIG. 3  is a perspective view of a track shoe including the track backer pads illustrated in  FIG. 1 ; 
           [0013]      FIG. 4  is a perspective view of a testing machine in accordance with the present disclosure; 
           [0014]      FIG. 5  is a perspective view similar to  FIG. 4  but with some components removed; 
           [0015]      FIG. 6  is a side view of the testing machine illustrated in  FIG. 5 ; and 
           [0016]      FIGS. 7A-7E  is a schematic view illustrating the operation of the testing machine illustrated in  FIG. 4 . 
       
    
    
       [0017]    Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. 
       DETAILED DESCRIPTION 
       [0018]    Example embodiments will now be described more fully with reference to the accompanying drawings. 
         [0019]    There is illustrated in  FIG. 1 , a perspective of a crawler track which is represented generally by reference numeral  10 . Crawler track  10  comprises a plurality of track shoe assemblies  12 , a plurality of road wheel assemblies  14  (only one shown) and a pair of spoked wheels  16  (only one shown) as is known in the art. Typically one of the spoked wheels  16  is driven which in turn drives a chain link  18  which is attached to the plurality of track shoe assemblies  12 . 
         [0020]    Referring to  FIG. 2 , a road wheel  30  is illustrated. Road wheel assembly  14  typically includes a pair of road wheels  30 , one of which is illustrated in  FIG. 2 . Each road wheel  30  includes a central wheel  32  which has its outer circumference covered by an annular elastomeric member  34 . 
         [0021]    Referring to  FIG. 3 , one of track shoe assemblies  12  is illustrated. Track shoe assembly  12  typically includes a track shoe  36  which is adapted to be secured to chain link  18  and a detachable elastomeric wear pad  38  which is attached to one side of track shoe  36 . 
         [0022]    Both annular elastomeric member  34  and elastomeric wear pad  38  exhibit wear during the operation of crawler track  10  and new elastomeric materials for elastomeric member  34  and elastomeric wear pad  38  are being developed.  FIGS. 4-7E  illustrate a testing machine  40  which is designed to test the durability of elastomeric member  34  and elastomeric wear pad  38  in a laboratory setting. 
         [0023]    Testing machine  40  comprises a support frame  42 , a positioning system  44  for track shoe assembly  12  and a drive system  46  for driving road wheel  30 . Support frame  42  is a generally box-like structure which includes a plurality of upright legs  50 , a lower support structure  52  and a middle support structure  54 . Both lower support structure  52  and middle support structure  54  are secured to the plurality of upright legs  50  as is illustrated in  FIGS. 4-6  with lower support structure  52  being located near the lower end of the plurality of legs  50  and middle support structure  54  being located near the middle portion of the plurality of legs  50 . The attachment of lower support structure  52  and middle support structure  54  to the plurality of legs  50  create the box-like structure for testing machine  40 . 
         [0024]    Positioning system  44  includes a track shoe locating frame  60 , a track shoe positioning frame  62  and a positioning mechanism  64 . Track shoe locating frame  60  is rotatably secured at one end to two of the plurality of upright legs  50  using a pair of bearing blocks  66 . An attachment structure  68  is attached to the opposite end of track shoe locating frame  60 . Attachment structure  68  is adapted to receive and support the track shoe assembly  12  being tested. One or more support plates  70  are attached to the pair of upright legs  50  to which track shoe locating frame  60  is attached as illustrated in  FIGS. 4-6 . 
         [0025]    Track shoe positioning frame  62  is rotatably secured to lower support structure  52  using a pair of bearing blocks  66 . A positioning pad  72  is attached to track shoe positioning frame at a position spaced from bearing blocks  66  in a direction towards the end of track shoe positioning frame  62  opposite to the end of track shoe positioning frame to which bearing blocks  66  are attached. Positioning pad  72  is attached to track shoe locating frame  60  through a generally horizontal beam  74  and a pair of vertical arms  76 . Pivotal movement of track shoe positioning frame  62  causes pivotal movement of track shoe locating frame  60  due to the attachment of positioning pad  72 , the attachment of beam  74  and the attachment of vertical arms  76 . 
         [0026]    Positioning mechanism  64  includes a hydraulic cylinder  80  which is attached to the end of track shoe positioning frame  62  opposite to the end attached to bearing blocks  66  and to one or more of support plates  70 . The stroking movement of hydraulic cylinder  80  causes pivotal movement of track shoe positioning frame  62  which in turn causes pivotal movement of track shoe locating frame  60  as described above. The pivotal movement of track shoe positioning frame  62  moves track shoe assembly  12  with respect to drive system  46  to control contact and loading between track shoe assembly  12  and road wheel  30  as discussed below. 
         [0027]    Drive system  46  comprises a power source  82 , a first mechanical eccentric drive  84  and a second mechanical eccentric drive  86 . Power source  82  is an electric motor which is attached to middle support structure  54  and drives first and second mechanical drives  82  and  84  through a drive belt and pulley system. A drive pulley  88  is attached to the drive shaft of power source  82 . 
         [0028]    First mechanical eccentric drive  84  comprises a drive shaft  90  rotatably attached to middle support structure  54  using a pair of bearing blocks  66 . Drive shaft  90  is driven by drive motor  82  through drive pulley  88  and a driven pulley  92  attached to drive shaft  90  using a toothed drive belt  94 . An eccentric  96  is part of drive shaft  90  and rotates with drive shaft  90 . A first driving arm  98  is rotatably attached at one end to eccentric  96  and at the opposite end to a road wheel support  100 . 
         [0029]    Second mechanical eccentric drive  86  comprises a drive shaft  102  rotatably attached to middle support structure  54  using a pair of bearing blocks  66 . Drive shaft  102  is driven by power source  82  through a pair of drive pulleys  104  attached to drive shaft  90  and a pair of driven pulleys  106  attached to drive shaft  102  using a pair of synchronized toothed drive belts  108 . The pair of synchronized toothed drive bolts  108  maintain and control the timing between the rotation of the first and second mechanical eccentric drives  84 ,  86 . An eccentric  110  is part of drive shaft  102  and rotates with drive shaft  102 . A second driving arm  112  is rotatably attached at one end to eccentric  110  and to the opposite end to road wheel support  100 . 
         [0030]    Road wheel support  100  is supported by first and second driving arms  98  and  112  and road wheel support  100  is also attached to track shoe locating frame  60  using a pair of linkage arms  118 . Linkage arms  118  are pivotably attached to road wheel support  100  and pivotably attached to track shoe locating frame  60 . As illustrated in  FIGS. 4-6 , a section of road wheel  30  which is to be tested is secured to road wheel support  100 . 
         [0031]    The operation of testing machine  40  is illustrated in  FIGS. 7A-7E . First a track shoe assembly  12  including elastomeric wear pad  38  to be tested is secured to attachment structure  68  which is attached to track shoe locating frame  60 . A section of a road wheel  30  including a section of annular elastomeric member  34  to be tested is secured to road wheel support  100 . Hydraulic cylinder  80  is then actuated to position track shoe locating frame  60  and thus track shoe assembly  12  in the proper location in relation to the section of road wheel  30  for testing. Power source  82  powered to rotate both first and second mechanical eccentric drives  84  and  86 . The rotation of drive shafts  90  and  102  causes the relative movement of the section of road wheel  30  in relation to the track shoe assembly illustrated in  FIGS. 7A-7E .  FIG. 7A  illustrates the start of a test cycle where the section of road wheel  30  is spaced from track shoe assembly  12 . Rotation of drive shafts  90  and  102  cause the initial contact of the section of road wheel  30  and track shoe assembly  12  as illustrated in  FIG. 7B . Continued rotation of drive shafts  90  and  102  causes the section of road wheel  30  to roll across track shoe assembly  12  as illustrated in  FIGS. 7C to 7D . Continued rotation of drive shafts  90  and  102  causes the section of road wheel  30  to separate from track shoe assembly  12  as illustrated in  FIG. 7E . Continued rotation of drive shafts  90  and  102  moves the section of road wheel  30  from the position illustrated in  FIG. 7E  to the position illustrated in  FIG. 7A  and the process repeats itself. The relative rotation between first and second mechanical eccentric drives  84  and  86  controlled by the pair of synchronized toothed drive belts  108  control the motion of the section of road wheel  30  in relation to track shoe assembly  12  such that the section of road wheel  30  moves in a predetermined rolling manner with respect to track shoe assembly  12 . 
         [0032]    This testing machine and process simulates the actual engagement between road wheel  30  and track shoe assembly  12  during movement of crawler track  10 . A load cell  130  attached to positioning pad  72  to monitor and adjust the loading between the section of road wheel  30  and track shoe assembly  12 . The load and contact between the section of the road wheel  30  and track shoe assembly  12  are adjusted by using hydraulic cylinder  80  which pivots track shoe positioning frame  62  to position track shoe assembly  12  with respect to the section of road wheel  30 . A controller (not shown) can continuously monitor the loading using load cell  130  and can make the necessary adjustments to the load in real time using hydraulic cylinder  80 . 
         [0033]    The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.