Abstract:
An efficient and effective computerized apparatus and method for determining the effects of railroad car humping on cargo in railroad cars. The invention broadly comprises a twelve-wheel test cart mounted on a pair of rails for simulating a rail car; an impact structure for simulating rail cars during humping; an electric motor drive unit for accelerating and propelling the test cart toward the impact structure, a series of hydraulic accumulator springs and valves for decelerating the test cart during the humping of the test cart with the impact structure, and a programmed computer for controlling test variables. The test apparatus allows the levels of severity to be readily changed and the test cart to be positively coupled to the impact structure or to rebound from the impact structure.

Description:
FIELD OF THE INVENTION 
     This invention relates to impact testing and more particularly to a computerized simulator and method for determining the effects on cargo during a railroad car humping. 
     BACKGROUND OF THE INVENTION 
     The coupling of rail cars is commonly referred to as a humping. During a humping of railroad cars, cargos are subjected to high inertia loads. If their containers and/or shipping provisions are inadequate, damage can occur, resulting in insurer losses and higher consumer prices. Simulators exist for evaluating the effects on cargo and their containers of humping. They rely on the deformation of rubber, plastic, springs, weights, etc. to rapidly decelerate the cargo. Tests show that the simulators do provide meaningful results for preventing damage and optimizing shipping provisions and containers. Consequently, producers and shippers must rely on actual experiences which are often costly and detrimental to customer goodwill. Moreover, many containers and shipping provisions are inadequate or more costly than necessary. A further problem with existing simulators is that they cannot be easily modified to simulate alternate levels of severity of rail car humping. 
     Turczyn, U.S. Pat. No. 4,545,236 is exemplary of existing rail car humping simulators. Turczyn discloses a cargo, carried on a sled, which is accelerated by gravity down an inclined plane. At the bottom of the plane there is a deformable cylinder which decelerates the sled and its cargo. The dynamic crush properties of the deformable cylinder are established from accelerometers mounted on railroad cars. After each test, the deformable cylinder is replaced. 
     SUMMARY OF THE INVENTION 
     The present invention completely overcomes problems and shortcomings of existing simulators by providing an efficient, easy to use, computerized apparatus and method for simulating railroad car humping. The invention resides in features which individually and collectively contribute to its ability to efficiently and reliably replicate inertia loads on cargo during “humping.” One advantage of the invention is that a manufacturer can reduce the time for developing adequate provisions for shipping a new product. Another advantage is that test conditions can be easily modified to vary levels of severity. Another advantage is that test results can be quickly obtained. Still yet another advantage is that test results are repeatable. Still yet another advantage is that test results correlate substantially better with real world conditions than those of simulators heretofore available. 
     The invention broadly comprises a twelve-wheel test cart mounted on a pair of rails; an impact structure for simulating rail cars which are coupled to the test cart; a means for propelling the test cart toward the impact structure, a means for decelerating the test cart during a humping of the test cart with the impact structure; and a programmable computer for controlling the test. Preferred means are disclosed for accelerating and decelerating the test cart during the simulated humping. 
     Further objects, benefits and features of the invention will become apparent from the ensuing detailed description and drawings which illustrate and describe the invention. The best mode which is contemplated in practicing the invention together with the manner of using the invention are disclosed and the property in which exclusive rights are claimed is set forth in each of a series of numbered claims at the conclusion of the detailed description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be better understood and further objects, characterizing features, details and advantages thereof will appear more clearly with reference to the diagrammatic drawings illustrating a presently preferred specific embodiment of the invention by way of non-limiting example only. 
     FIG. 1 is a plan view of a rail car “humping” simulator which embodies the present invention. 
     FIG. 2 is a side elevational view of the simulator. 
     FIG. 3 is an enlarged plan view of a rail cart. 
     FIG. 4 is an enlarged plan view of an impact structure. 
     FIG. 5 is an enlarged plan view of a computer control center. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings, in FIGS. 1 through 4 inclusive, a computerized rail car “humping” simulator is shown in diagrammatic form for the non-limiting purpose of describing the invention. The primary objects of the simulator is to increase profits and decrease consumer prices. These objectives are met by efficiently simulating rail car humping in a manner which closely correlates with conditions in the field. Test results are used for optimizing shipping provisions and prevent damage to cargo and containers. 
     The simulator and method were developed from data which was acquired during two years of extensive testing of different rail systems at various locations. Testing has verified that the simulator and method accurately simulate conditions which exist during rail car “humping”. The simulator is comprised of a pair of horizontal rails  11 , a twelve-wheel test cart  12  mounted on the rails  11 , a means for propelling the test cart  12 , an impact structure  13  for decelerating the test cart  12 , a programmable computer  14 ; and computer software  15  for selectively varying the severity of humping. 
     In the preferred apparatus shown in FIGS. 1 through 4, the test cart  12  is connected by a pair of chains  16  to an electric motor drive unit  17 . The chains  16  and drive unit  17  comprise the means for propelling the test cart  12  toward the impact structure  13 . Other well known devices are available which can be used for propelling the cart  12 , by way of example, ball screws, hydraulic cylinders or motors, pneumatic cylinders, cables, adjustable inclined tracks and hydrostatic transmission driven cables. The chains  16  and electric motor drive unit  17  are capable of providing cart speeds as high as 16 miles per hour. To date, the most common cart speeds with the preferred embodiment 10 have been 6 and 8 miles per hour. During a test program, the two speeds are generally used. If damage occurs at the lower speed, the testing is halted until improvements are made which result in a satisfactory test. Thereafter, a test is made at the higher cart speed. 
     The twelve-wheel test cart  12  is somewhat shorter than a typical rail car but similar in width, height and weight (19,000 pounds) to a typical rail car. The top  18  and sides  19  of the cart  12  are enclosed with an open wire grid  20  to allow viewing and photographing of a cargo in the cart  12 . A sound proof room  38  with a glass window  37  is provided for shielding observers from the excessive shock waves which occur during a humping of the cart  12  with the impact structure  13 . The front  21  of the cart  12  is a rigid bulkhead  22  and the rear  23  is left open to allow loading of the cargo. On the forward bulkhead  22  there is a male member  24  of a rail car coupling. Power is supplied to the electric motor drive  17  by an electrical power supply  25  which provides power to all systems of the humping simulator  10 . An air compressor  26  in a separate room provides power for chain tensioning. 
     The electric motor drive  17  and power supply  25  are operatively connected to the computer  14  which is located in a computer control center  27 . The acceleration and velocity of the test cart  12  are determined by the force of the chains  16  and its duration. The acceleration and speed of the cart  12  are set by an encoder signal to the computer  14  in a closed-loop feedback system with the electric motor drive  17  propelling the cart  12  on the dual rails  11 . The computer control center  27  houses all of the control system components, including the computer  14  and “E” stops. The computer&#39;s software  15  consists of a group of application programs which manage the overall operation of the system, including the motion of the cart  12  and the hydraulic system which decelerates the cart  12 . The relationship between the test variables are shown in the following 2 nd  order homogeneous differential equation: 
     
       
         m{umlaut over (x)}+c{dot over (x)}+kx=0 
       
     
     where: 
     {umlaut over (x)}=acceleration of the rail car 
     m=combined mass of rail cart and test specimen 
     {dot over (x)}=velocity of rail car 
     c=damping of hydraulic system 
     x=displacement of rail car 
     k=spring rate of hydraulic system (accumulators) 
     The solutions of the above equation fall under the following conditions: 
     c 2 &gt;4 mk overdamped 
     c 2 =4 mk critically damped 
     c 2 &lt;4 mk underdamped 
     The spring rate k is derived by correlating test data with measurements of rail car systems. In the preferred embodiment 10, the spring rate for various levels of severity was found to be within the range of 1500 pounds per inch to 3500 pounds per inch. It will be appreciated that the range may vary somewhat because of differences in test apparatus. 
     Computer programs, namely C++, Lookout, Labview, Windows and Excel are used with the preferred embodiment 10 for operating the simulator system  10 . Other well known computer programs and/or micro processors are also available for performing control functions. Test results of the preferred embodiment 10 show that cart acceleration can be controlled within 0.2 g&#39;s and cart deceleration can be varied between 50 and 400 ms, depending on the inputs at the computer control center  27 . 
     The impact structure  13  includes a usual type superstructure, a massive fixed concrete barrier  28 , two groups of accumulator gas springs  29 ,  30 , control valves  24  and a piston  32  in a hydraulic cylinder  33  which transfers oil between a blind impact end of the cylinder  33  to a pre-selected number of the accumulator springs  29 ,  30 . The accumulator springs are the usual type of hydraulic/pneumatic springs which absorb impact energy by compressing a gas, such as nitrogen. The gas is pre-loaded by a non-compressible hydraulic fluid which is separated from the gas by a piston or bladder. The gas, stored in the accumulator springs, being compressible, acts as a spring. The impact energy of the test car  12  is transmitted by the non-compressible liquid (hydraulic oil) and is absorbed by compressing the gas. The accumulator springs  29 ,  30  decelerate the test cart  12  during a humping with the impact structure  13 . Other energy absorbing systems, such as pneumatic cylinders, can be used for decelerating the cart  12 . 
     The two groups of accumulator springs  29 ,  30  are shown in FIGS. 1 and 2. In a selected number of the first group of eighteen accumulator springs  29  are fluidly connected and supply oil to the rear side of the piston  32  and provide the force for decelerating the cart  12  during the humping with the impact structure  13 . A selected number of the second group of eleven accumulator springs  30  are fluidly connected and supply oil to the front of the piston  32  and act in the opposite direction to the first group  29  to satisfy the high flow requirements to the cylinder rear end. They also establish the initial position of the piston  32  prior to an impact. A set of control valves  34  which operate by inputs from the computer  14  select the number of accumulator springs  29 ,  30  of the first  29  and second  30  groups which are used during a test. 
     The stroke of the piston  32  and the selected number of accumulator springs  29 ,  30  decelerate the cart  12  for a given impact velocity and load. The piston&#39;s stroke is manually adjustable but can be adjusted at the computer  14  by utilizing well known systems, such as servo motors, valves and controls or stepping motors, ball screws and controllers for setting the stroke. A female member  35  of the rail car coupling is attached on the forward end of the piston  32 . 
     A test is conducted in the following manner. The level of severity is specified by a requester, based on prior experience or a recommendation of the test facility, if the requester lacks experience. Test variables at the computer  14  and the piston stroke is manually set according to the level of severity. A cargo specimen  36  is preferably placed on the test cart  12  rearward of the cart&#39;s front bulkhead  22  to simulate a common real world condition. Spacing the cargo away from the bulkhead  22  increases the severity of the test over a position against the bulkhead  22 . A distance of four inches has been found to be typical of the real world. 
     At the onset of the test, the chains  16  and motor drive unit  17  accelerate the cargo specimen  36  for a specified time interval toward the impact structure  13 . This establishes the velocity at which the cart  12  impacts the piston  32 . When the cart  12  couples with the piston  32 , two options are available. With the first option, the cart  12  is not allowed to rebound away from the impact structure  13 . This is accomplished by positively coupling the male coupling member  24  of the test cart  12  with the female member  35  at the end of the piston  32 . With the second option, the female coupling member  35  allows the male member  24  to disengage and the test cart  12  to rebound. 
     When coupling occurs, the cart  12  rapidly decelerates, but the test specimen  12  continues with the same forward motion until contacting the bulkhead  22  of the decelerating cart  12 . After the contact occurs, the test specimen begins to decelerate with the cart  12  in a controlled manner to replicate real-world conditions. Physical damage to the test specimen  36  and dunnage, if present, are observed through a safety glass window  37  of the soundproof room  38 . 
     From the above it will be appreciated that our invention provides an efficient and reliable apparatus and method for evaluating the effects on a specific cargo of rail car coupling. Moreover, it can increase an insurer&#39;s profits and lower consumer prices. 
     Although only one embodiment of our invention has been disclosed, it is not our intention to limit our invention to this embodiment, since after having the benefit of our disclosure, other embodiments can be developed by such changes as inversion of elements, substitution of materials and parts and changes in materials which are known and obvious to persons skilled in the arts to which our invention relates.