Abstract:
An energy absorbing system. The system includes two anchors, a net mechanically coupled thereto and spanning a roadway, and a first raising/lowering arm arranged on one side of the roadway. The first raising/lowering arm mechanically coupled to and supporting an upper portion of the net via a first upper frangible tensioner and mechanically coupled to and supporting a lower portion of the net via a first lower frangible tensioner. A second raising/lowering arm arranged on another side of the roadway, the second raising/lowering arm mechanically coupled to and supporting an upper portion of the net via a second upper frangible tensioner and mechanically coupled to and supporting a lower portion of the net via a second lower frangible tensioner. The first and second upper and first and second lower frangible tensioners decouple from the net upon application of a predetermined force.

Description:
This application is a continuation of U.S. patent application Ser. No. 10/726,839, filed Dec. 2, 2003, now U.S. Pat. No. 7,210,873, which is hereby incorporated by reference. 
    
    
     BACKGROUND 
     This invention relates to an energy absorbing system with a support where the system can be used to dissipate unwanted energy such as, e.g., the energy of an errant vehicle. The system may be used in a variety of applications, including HOV lane traffic control, drawbridges, security gates, or crash cushion applications. In one application, the system may be used to prevent a vehicle from crossing a railroad track while the warning gates are down or there is a train in the area. 
     SUMMARY OF THE DISCLOSURE 
     The present disclosure relates to an energy absorbing system. In one embodiment, the energy absorbing system includes a first anchor and a second anchor, located on opposite sides of a roadway, a net mechanically coupled to each of the first and second anchors and spanning the roadway, a first raising/lowering arm arranged on one side of the roadway, the first raising/lowering arm mechanically coupled to and supporting an upper portion of the net via a first upper frangible tensioner and mechanically coupled to and supporting a lower portion of the net via a first lower frangible tensioner, a second raising/lowering arm arranged on another side of the roadway, the second raising/lowering arm mechanically coupled to and supporting an upper portion of the net via a second upper frangible tensioner and mechanically coupled to and supporting a lower portion of the net via a second lower frangible tensioner, wherein the first and second upper and first and second lower frangible tensioners decouple from the net upon application of a predetermined force. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view which illustrates an energy absorbing system with support arranged at a railroad crossing of a single-lane roadway according to one aspect of the system of the present disclosure. 
         FIG. 2  is a perspective view which illustrates an energy absorbing system with support arranged at a railroad crossing of a single-lane roadway and restraining a vehicle according to one aspect of the system of the present disclosure. 
         FIG. 3A  is a side view of a stanchion, joint, shock absorber and capture net according to one aspect of the system of the present disclosure. 
         FIG. 3B  is a side view of a stanchion and capture net according to one aspect of the system of the present disclosure. 
         FIG. 4A  is a front view of a support, breakaway device and capture net according to one aspect of the system of the present disclosure. 
         FIG. 4B  is a side view of a support according to one aspect of the system of the present disclosure. 
         FIG. 4C  is a side view of a support according to one aspect of the system of the present disclosure. 
         FIG. 5  is a front view of a capture net according to one aspect of the system of the present disclosure. 
         FIG. 6A  is a top view of a bearing sleeve clamp according to one aspect of the system of the present disclosure. 
         FIG. 6B  is a side view of a bearing sleeve clamp according to one aspect of the system of the present disclosure. 
         FIG. 7A  is a side view of a joint according to one aspect of the system of the present disclosure. 
         FIG. 7B  is a top view of a joint according to one aspect of the system of the present disclosure. 
         FIG. 8A  is a side view of a shock absorber in a compressed state according to one aspect of the system of the present disclosure. 
         FIG. 8B  is a side view of a shock absorber in an expanded state according to one aspect of the system of the present disclosure. 
         FIG. 9A  is a side view of a shock absorber in a compressed state according to one aspect of the system of the present disclosure. 
         FIG. 9B  is a side view of a shock absorber in an expanded state according to one aspect of the system of the present disclosure. 
         FIG. 10  is a side view which illustrates an energy absorbing system with support arranged at a roadway according to one aspect of the system of the present disclosure. 
         FIG. 11  is a side view which illustrates an energy absorbing system with support arranged at a roadway according to one aspect of the system of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The energy absorbing system in one aspect may comprise an anchor or other mechanism for providing a fixed point, for example, a stanchion, one or more energy absorbing mechanisms coupled to the anchor for absorbing forces, a restraining capture net or other barrier coupled to one or more the energy absorbing mechanisms, and a support or other mechanism for supporting the restraining capture net or other barrier. In another aspect, the restraining capture net or other barrier may be coupled to the anchor without an energy absorbing mechanism between the restraining capture net and stanchion. 
     In another aspect, the support may be attached to the restraining capture net or other barrier via a frangible breakaway mechanism which breaks and thereby decouples the support and the restraining capture net in response to tensile forces that meet or exceed a minimum threshold force. In one aspect, it is envisioned that static tension from the restraining capture net in its quiescent state would not exceed this minimum threshold force, but that increased tension due to the dynamic forces exerted upon the frangible breakaway mechanism from a vehicle driving into the restraining capture net would exceed this minimum threshold force. 
     In another aspect, the support may be attached to the restraining capture net via a non-frangible connector and the support may be disturbed by the impact of the vehicle, or the non-frangible connector may expand or extend. In another aspect, the support may include a frangible or releasable portion, for example, a post, which decouples the support from the net in response to a minimum threshold force. In another aspect, the support may include a retractable mechanism for supporting the restraining capture net from above. 
     In yet another aspect, the support may be raised and lowered, thereby raising and lowering the restraining capture net or other barrier which it supports. 
     The energy absorbing mechanism may be mounted for rotation about the axis and be expandable in a direction substantially orthogonal to the axis. In another aspect, the energy absorbing mechanism may be a shock absorber, braking mechanism, or other friction damper, and may include a securing mechanism such that an expandable section of the energy absorbing mechanism, for example, a piston, does not expand except in response to tensile forces that meet or exceed a minimum threshold force. In one aspect, the static tension from the restraining capture net in its quiescent state will not exceed this minimum threshold force, and increased tension due to the dynamic tensile forces exerted upon the shock absorber from a vehicle driving into the restraining capture net would exceed this minimum threshold force. 
     Referring to the drawings, wherein like reference numerals represent identical or corresponding parts throughout the several views, and more particularly to  FIG. 1 , a general layout of an embodiment according to one aspect of the system of the present disclosure is shown installed at a railroad crossing. A roadway is indicated generally by reference numeral  10  and railroad tracks are indicated generally by reference numeral  20 . A capture net  500  is stretched across roadway  10  parallel to tracks  20 . Capture net  500  extends between anchors, for example, stanchions  300 , and supports  400  located on opposite sides of roadway  10 . The capture net  500  may be coupled at each end to a braking mechanism, for example, shock absorbers  800  which in turn may be coupled to a joint  700 , which may be coupled to a bearing sleeve  330  surrounding stanchion  300 , as described in greater detail below. 
     In  FIG. 1 , the shock absorbers  800  are substantially parallel to roadway  10 , and shock absorber pistons  804  are in a compressed state. In this aspect, the supports  400  are arranged with respect to stanchions  300  in a manner such that, on impact, the pistons  804  may extend in a direction substantially the same as the direction in which the vehicle  30  is traveling. 
     The capture net  500  may be coupled to supports  400  via a breakaway connector  450 . The supports  400 , which may be raised and lowered, are shown in a raised position in  FIGS. 1 and 2 . When supports  400  are lowered, the capture net  500  may rest in a position such that vehicles may drive over the capture net  500  unimpeded. In another aspect, when supports  400  are lowered, capture net  500  may be tucked into, for example, a slot cutout spanning roadway  10 , and having sufficient depth and width to accommodate some or all of the capture net  500 ; such a cutout may be incorporated into a speed-bump. 
     Shown at the top of  FIG. 2  is a vehicle  30  which has crashed into capture net  500  and is restrained by capture net  500  to prevent it and its occupants from encroaching onto tracks  20 . Capture net  500  has been deflected by the collision from its quiescent state so as to form a shallow “V” shape. Bearing sleeve  330  has rotated about stanchion  300  and shock absorbers  800  are now pointed inward toward roadway  10 , with shock absorber pistons  804  no longer in a compressed state. Joints  700  may pivot vertically depending on certain factors such as, for example, the height of the vehicle impact with capture net  500 . Further, breakaway connectors  450  have been severed, and, therefore, supports  400  no longer support capture net  500 . 
     The ability of capture net  500  to be deflected, yet provide a restraining force, allows vehicle  30  to be progressively stopped, thereby lessening adverse effects of the impact forces acting on vehicle  30  and its occupants. The deflecting and restraining functions are achieved by a unique energy absorbing system, described in greater detail below. 
       FIG. 3A  is a side view of a stanchion, joint, shock absorber and capture net according to one aspect of the system. Stanchion  300  may include a pipe  302 , which may be reinforced by inserting, a bar or other support (not shown) therein, may be filled with concrete (not shown) and embedded into a concrete base  320 , which has been poured into the ground. Stanchion  300  has an axis  310 , which may be a vertical axis, whose function will become clear hereinafter. 
     The system of the present disclosure may also include a bearing sleeve  330  fitted around stanchion  300  and which may be rotatable about stanchion  300 . Bearing sleeve clamps  600  fitted around stanchion  300  may be used to prevent bearing sleeve  330  from sliding vertically on stanchion  300 . Bearing sleeve  330  and bearing sleeve clamps  600  may be fabricated from pipe having approximately the same inner diameter as the outer diameter of stanchion  300 . 
     An example of a bearing sleeve clamp  600  according to one aspect of the system of the present disclosure is shown in  FIGS. 6A  (top view) and  6 B (side view). As shown in  FIGS. 6A and 6B , bearing sleeve clamp  600  may include a sleeve clamp ring  602  attached to a sleeve clamp flange  604  for securing about stanchion  300 . Sleeve clamp flange  604  may contain one or more holes  606  for accommodating one or more bolts or other securing mechanisms. 
     Returning to  FIG. 3A , stanchion  300  may be coupled to capture net  500  via shock absorber  800  and joint  700 . Accordingly, cable ends  530  of top cable  510  and bottom cable  520  may be coupled to piston connectors  806 , using a pin or other mechanism. Shock absorber  800  may have a shock absorber flange  802  which may be secured using bolts to joint front flange  702 . Joint rear flange  720  may be secured to bearing sleeve  330 , by a weld, bolts or other means to a bearing sleeve flange (not shown) coupled to bearing sleeve  330 . Alternatively, joint  700  may be omitted, with shock absorber flange  802  secured to bearing sleeve  330 , by a weld, bolts or other suitable means. to the bearing sleeve flange. 
     In another aspect, a crossbar  900  may be attached vertically between two or more cables, joints  700 , or shock absorbers  800  arranged on a stanchion  300 . The crossbar  900  may alleviate vertical torque on the cables, joints  700  and shock absorbers  800 , which might otherwise occur due to the fact that a vehicle  30  colliding with the capture net  500  may cause the top cable  510  and bottom cable  520  and, therefore, the joints  700  and shock absorbers  800  connected thereto, to tend to squeeze together. Thus, the crossbar  900  may act as a stabilizer against this vertical torque. The crossbar  900  may also cause top and bottom pistons  804  to expand with increased uniformity upon impact by vehicle  30 . In one aspect, the crossbar  900  may be formed of a rigid material such as, for example, steel or other hard metal. In another aspect, crossbar  900  may be constructed of non-rigid material, for example, cable. 
       FIG. 3B  shows a side view of a stanchion and capture net according to another aspect of the system of the present disclosure. In this aspect, shock absorbers  800  are not present, and cable ends  530  may be coupled to the stanchion  300  or bearing sleeve  330 . In other aspects, cable ends  530  may be coupled to joint front flange  702 , or joint inner prongs  722  using pin  712 . In each of these aspects, because shock absorbers  800  are not present, vehicle  30  will come to a halt in a shorter distance with greater deceleration. In these aspects, capture net  500  may be constructed of cable having a greater strength than in a system in which shock absorbers  800  are present. 
       FIGS. 4A  (front view),  4 B (side view) and  4 C (side view) show a support  400  according to one aspect of the system of the present disclosure. As shown in  FIGS. 4A and 4B , the support  400  may include a post  402 , which may include top cable securing point  404  for attaching, for example, a breakaway connector  450  to top cable  510 , and bottom cable securing point  406  for attaching, for example, a breakaway connector  450  to bottom cable  520 . 
     Post  402  may be inserted into a spool  426  around which a spring  424  is coiled in a manner such that in the spring&#39;s uncompressed state, post  402  is in an upright, vertical position as shown in  FIGS. 4A and 4B . Post  402  may pivot with the spool  426  in the direction shown by arrow  430 . Spring  424  and spool  426  may be encased in housing  410  which may include top plate  412 , base plate  414 , and side plates  420 , as well as back plate  418  and back support  422 . Post  402  may also include securing point  408  which may be used by a raise-lowering mechanism (not shown). Post  402  may also include a hook or other device (not shown) for connecting to a latching mechanism which may be placed on the ground or incorporated as part of an extension of housing  410  and which secures the post  402  when the spring  424  is in a compressed state. 
     In another aspect, a levered system or a powered drive system, for example, an electric motor, located within or external to housing  410  may be used in place of the spring-based system described above. 
     As shown in  FIG. 4C , post  402  may have a raised and lowered position. Support  400  may be positioned such that, in the lowered position, the distal end of post  402 , i.e. that end not in contact with spool  426 , is pointed in the direction of oncoming vehicle  30 . 
     As described above, breakaway connector  450  disconnects the support  400  and the capture net  500  in response to forces that meet or exceed a minimum threshold force. In one aspect, static tension from the capture net  500  in its quiescent state would not exceed this minimum threshold force, but increased tension due to the dynamic tensile forces exerted upon the breakaway connector  450  from a vehicle  30  driving into the capture net  500  would exceed this minimum threshold force. 
     An eyebolt-turnbuckle-cable-clamp combination may be used to couple support  400  to capture net  500  and act as breakaway connector  450 . The eyebolt may connect to top cable securing point  404 . The eyebolt then may be coupled to an adjustable turnbuckle which may control the height and/or tension of capture net  500  when the support  400  is in the upright position. The other end of the adjustable turnbuckle may by coupled to a cable, for example, a 5/16 inch cable, which couples to a cable clamp attached to capture net  500 . It may be expected that at least the 5/16 inch cable will break, thereby disconnecting turnbuckle and cable clamp, when the minimum threshold force is exceeded. It will be apparent to one skilled in the art that, according to this aspect of the system of the present disclosure, the type, style and thickness of breakaway connector  450  used will depend on a number of factors, including, but not limited to, the type of capture net  500  and the amount of static tension applied to capture net  500  in its quiescent state. 
     Breakaway connector  450  and surrounding equipment may also include one or more of the following, alone or in combination: a turnbuckle, cable, come-along, bolt, or other frangible connection device. It will be apparent to one skilled in the art that a mechanism may be used for both its tensioning and frangible properties. 
     The raise-lowering mechanisms controlling post  402  may be under the control of a standard train-detecting system, such as is commonly used to control gates at railroad crossings. In operation, a control system (not shown) may sense the presence of an oncoming train and may thereby control capture net operations. In addition to railroad crossings, the system can also be used in a variety of other applications, including HOV lane traffic control, drawbridges, security gates, or crash cushion applications. One can readily appreciate that the control system for such applications may differ from that used in a railroad crossings. At security gates, for example, the capture net  500  may be in a raised position, and actuation of the security system (e.g., by a guard, a key card, keyboard punch, etc.) would lower the barrier and permit passage. In another application, the capture net  500  may be in a lowered position and raised when warranted, for example, in an emergency. 
     In another aspect, the support  400  may be attached to the restraining capture  500  net via a non-frangible connector. In this aspect, the non-frangible connector will not uncouple the support  400  from the capture net  500  in response to the threshold force. In one such aspect, the support  400  may be disturbed by the impact of the vehicle  30 . In another aspect, the support  400  may be integrated into the net  500 . In another aspect, the non-frangible connector may expand or extend in response to a threshold force. In another aspect, the non-frangible connector may compress in response to a threshold force. 
     In yet another aspect, the support  400  may include a frangible or releasable portion, for example, the post  402  may decouple the support  400  from the capture net  500  in response to a minimum threshold force. 
     In another aspect, the support  400  may include a retractable mechanism (not shown) for supporting the restraining capture net  500  from above. 
       FIG. 5  shows a capture net  500  which includes a top cable  510  and bottom cable  520 , each having cable ends  530 , where the top cable  510  and bottom cable  520  may be coupled by a number of vertical cables  540 . The vertical cables  540  may be coupled by a center cable  550 . 
     Vertical cables  540  may be coupled to center cable  550 , for example, by using a u-bolt, or the two may be interwoven. In another aspect of the system of the present disclosure, the vertical cables  540  may be, for example, woven into the top cable  510  and bottom cable  520 . Other suitable nets may be used. 
       FIGS. 7A and 7B  show side and top views, respectively, of joint  700  according to one aspect of the system of the present disclosure. A prong stop plate  706 , may make contact with joint rear flange  720  to support the weight of the capture net  500  and shock absorber  800  and may prevent joint front flange  702  from pivoting downward beyond a predetermined level, for example, a horizontal level. Joint outer prongs  708  may be supported by joint outer prong supports  710  which attach to joint front flange  702  and fit on either side of joint inner prongs  722 . Joint inner prongs  722  attach to joint rear flange  720  and may be supported by joint inner prong support  724 . Joint outer prongs  708  and joint inner prongs  722  may be rotatably fixed using a pin  712 , thereby allowing shock absorber  800  to pivot on a vertical plane. Joint front flange  702  may have bolt holes  704  for securing to shock absorber flange  802 . 
       FIGS. 8A and 8B  show a side view of a shock absorber in a compressed state and expanded state, respectively. Shock absorber  800  has shock absorber flange  802  which may couple to joint front flange  702 . 
     Shock absorber piston  804  may be removably attached to capture net  500  via a piston connector  806 , which may be an eyelet extension, through which a cable, clamp or other appropriate securing mechanism may be passed in order to secure the cable end  530  to the shock absorber piston  804 . 
     Prior to vehicle  30  colliding with capture net  500 , shock absorber  800  may be in a compressed state and may be secured by a threshold force securing mechanism. The threshold force securing mechanism may be capable of withstanding a predetermined threshold tensile force. In one aspect, a threshold force securing mechanism includes one or more shear pins  808  which may be inserted through a shear pin collar  810  into a shear pin ring  812 . A number of shear pins  808 , for example, four, may be arranged radially about the longitudinal axis of shock absorber  800 . The shear pin collar  810  may be integral or separate from other parts of the shock absorber. The shear pin  808  may be a self-setting screw type pin or shear pin  808  optionally may be secured by a set screw  814 . Other threshold force securing mechanisms can be used in combination with, or instead of, a shear pin. For example, a securing mechanism such as a brake pad, a counterweight, or other counter-force may be used. The threshold force securing mechanism allows the shock absorber  800 , without expanding from its compressed state, to assist the support  400  in pulling capture net  500  taut. The shock absorber  800  on the other side of roadway  10 , in an identical configuration, will assist the other corresponding support  400  in pulling the other side of the capture net  500  taut. 
     Capture net  500  may be installed with a pre-tension horizontal load, for example, 1,000-20,000 pounds, on its cables. This load will depend on a number of factors including, but not limited to, the length of capture net  500 , the desired height of capture net  500 , and construction and materials of the capture net  500 . 
     When a vehicle  30  collides with capture net  500 , the vehicle deflects the capture net  500 , causing it to exert a tensile force exceeding the minimum threshold force upon shock absorber  800 . When the threshold force securing mechanism includes shear pins  808 , the tensile force causes the shear pins  808  to shear and thereby permits the expansion of piston  804  of shock absorber  800  against the resistance of the hydraulic fluid in cylinder  816  ( FIG. 8B ). Shock is thereby absorbed during its expansion, while the force of the capture net  500  may rotate shock absorber  800  and bearing sleeve  330 , and may cause joint  700  to pivot about a horizontal axis. Forces applied upon capture net  500  are thereby translated through the center of stanchion  300 , which is solidly anchored in foundation  320 . Therefore, energy may be distributed among and absorbed by capture net  500 , the shock absorbers  800 , joint  700  and the stanchion  300 . 
     The shock absorbing mechanism may alternatively include a torque protection structure as illustrated in  FIGS. 9A and 9B , which show side views in a compressed and expanded state, respectively. According to this aspect, shock absorbers  800  include a protective sleeve  818  which may be coupled to and travel with piston  804  in order to add structural strength to resist deformation of the housing or other parts of the shock absorber  800  due to the torque that the capture net  500  exerts upon capturing a vehicle and deflecting shock absorbers  800 . The protective sleeve  818  may be made of any suitable structural material, for example, aluminum or steel. 
       FIG. 10  is a side view which illustrates an energy absorbing system with support  400  arranged at a roadway according to one aspect of the system of the present disclosure. Net  500  is connected to an anchor, for example, a tie back  1002 , which may be located above, at, or below ground level. In the aspect shown, cable ends  530  of top cable  510  and bottom cable  520  are each coupled to tie back  1002  which is embedded below ground level in concrete  1004  alongside roadway  10 . In another aspect, each of top cable  510  and bottom cable  520  may be coupled to a separate tie back  1002 . In another aspect, tie back  1002  may be coupled to net  500  via a socket (not shown). 
       FIG. 11  is a side view which illustrates an energy absorbing system with support  400  arranged at a roadway according to one aspect of the system of the present disclosure. Net  500  is coupled to a shock absorber  800  which is coupled to an anchor, for example, a tie back  1002 , which may be located above, at, or below ground level. In the aspect shown, cable ends  530  of top cable  510  and bottom cable  520  are each coupled to shock absorber  800  which is coupled to tie back  1002  which is embedded below ground level in concrete  1004  alongside roadway  10 . In another aspect, each of top cable  510  and bottom cable  520  may be coupled to any combination of shock absorbers  800  and tie backs  1002 . 
     An embodiment similar to that shown in  FIGS. 1 and 2  was constructed as follows. It will be apparent to one skilled in the art that size and thickness of the materials used will vary based on, for example, the expected potential energy encountered by the system, determined by such factors as the expected size and velocity of the vehicles to be arrested. 
     The overall width of the installation was 12 feet centerline to centerline of the stanchions  300 . The capture net  500  width was 25 feet, and included top cable  510 , bottom cable  520  and center cable  550  spaced 1.5 feet apart and coupled by seven vertical cables  540  spaced 1.5 feet apart. The uninstalled constructed capture net  500  height was 3 feet. The height of the capture net  500  when installed and tensioned was 50.25 inches to the center of the top cable and 15.75 inches to the center of the bottom cable as measured at the centerline of the capture net  500 . The top cable  510  and bottom cable  520  were 1.25 inch 6×26 galvanized MBL 79 tons, the vertical cables  540  and center cable  550  were ⅝ inch 6×26 galvanized MBL 20 tons, and the vertical cables  540  were coupled to the top cable  510  and bottom cable  520  by swage sockets. Cable ends  530  were also swage sockets. 
     Cable ends  530  of top cable  510  and bottom cable  520  were coupled to the stanchion  300  via shock absorber  800 , joint  700  and bearing sleeve  330  at points 2 feet 10 inches and 1 feet 7 inches as measured from ground level to the cable center point, respectively. 
     In an aspect where shock absorbers  800  are not present, top cable  510  and bottom cable  520  may be, for example, 1.5 inch thickness, and center cable  550  and vertical cables  540  may be ¾ inch thickness. 
     In another aspect a 50 foot capture net  500  may be used for a 36 foot distance between stanchions  300 , which may include top cable  510 , bottom cable  520  and center cable  550  spaced 1.5 feet apart coupled by twenty-three vertical cables  540  spaced 1.5 feet apart. 
     The supports  400  were located 13 feet in front of, and 3 feet to the outside of the stanchions  300 , with a pole  402  height of 4 feet 8 and ⅝ inches and top securing height of 4 feet 7 inches and bottom securing height of 1 feet 8 inches. 
     Concrete base size may vary by installation and application. In the embodiment constructed, the hole used for the concrete base  320  was measured as 15 feet in direction vehicle  30  was traveling, 27 feet between stanchions  300  and 3.5 feet deep. 
     The spring  424  used had 1000 ft lbs torque, an inner diameter of 9 inches and an outer diameter of 11 inches. Joint front flange  702  included four holes for bolting to shock absorber flange  802 . Joint rear flange  720  was welded to bearing sleeve  330 . Pin  712  had a length of 10 and ¾ inches and diameter of 2 and ⅜ inches. 
     The shock absorbers  800  used were hydraulic with about a 130,000 pound resistance with a 36 inch stroke and had an accumulator with a 5,000 pound return force for use with a 15,000 pound, 50 mph vehicle impact. The length of shock absorber  800  was 97 inches extended and 61 inches compressed, with a diameter of 10.8 inches. 
     Stanchion  300  included a 2 inch thick steel pipe, which had a 16 inch outside diameter and was 94 inches long. The stanchion  300  was reinforced by inserting a 4 inch thick steel bar, which had a width of 11.3 inches and length of 94 inches. Stanchion was filled with concrete and was embedded approximately 3.5 feet deep below ground level and extended approximately 3.8 feet above ground level. 
     Bearing sleeve  330  was 31″ long. Bearing sleeve clamp  600  had an outside diameter of 18 inches. Sleeve clamp flange  604  included two holes  606  to accommodate two bolts for tightening about stanchion  300 . Bearing sleeve clamp  600  had an inner diameter of 16 inches and was fabricated of the same material as bearing sleeve  330 . 
     Numerous additional modifications and variations of the present disclosure are possible in view of the above-teachings. It is therefore to be understood that within the scope of the appended claims, the present disclosure may be practiced other than as specifically described herein.