Abstract:
A crash load absorption structure for a motor vehicle. The structure includes a compressible load absorbing structure. The compressible load absorbing structure includes a front portion and a rear portion. The front portion and the rear portion are arranged to compress under a crash load along a generally longitudinal direction. The compressible load absorbing structure also includes a structural joint located within the compressible load absorbing structure, the joint is between at least two structural members. A load transfer element is configured to promote breaking of the structural joint during a vehicle crash.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to United Kingdom application no. 1100653.3 filed 14 Jan. 2011 entitled “Crash Load Absorption Structures for Motor Vehicles,” which is hereby incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     The present invention relates to crash load absorption structures for motor vehicles, and to motor vehicles containing such structures. 
     BACKGROUND 
     Production motor cars are required to pass various safety tests to ensure that they are sufficiently safe for use on public roads. It is desirable that the occupants of a motor car do not suffer injury when the motor car is in a collision. Therefore, at least one of the tests a motor car type has to pass is to ensure that a motor vehicle occupant will not suffer an acceleration higher than a certain amount during a collision. One of the safety tests carried out for vehicles is the United States of America Federal front impact test when the motor car is projected forwards at a speed of 35 miles per hour (15.65 meters per second) into a substantially solid immovable flat wall arranged perpendicular to the direction of motion of the motor car. This test therefore simulates what may happen if a motor car is accidentally driven directly into a solid and substantially immovable object such as a reinforced concrete bridge support at the side of the road or a very heavy vehicle. 
       FIG. 1  shows part-schematically a known motor vehicle type undergoing the United States of America Federal front impact test. As shown, the motor car  10  has four wheels  12  and is projected into the flat front, wall  14  of a substantially rigid immovable object  16 . During the collision, a front crash load absorption structure  18  deforms as shown in  FIGS. 2A to 2D . The front crash load absorption structure  18  has on each side of the car a primary crush can  20 , a secondary crush can  22  and a tertiary crush can  24 . The primary, secondary and tertiary crush cans  20 ,  22 ,  24  are permanently deformably crushable. The primary crush can  20  and secondary crush can  22  are joined together by an interface casting  26  and the secondary crush can  22  and tertiary crush can  24  are joined together by an upper wishbone casting  28  onto which an upper wishbone  30  of the front suspension is mounted. The tertiary crush can  24  is connected by a rear interface casting  32  to a front structure mounting member  34  of the body structure of the motor car  10 . 
     As shown by the sequence of views from  FIG. 2A to 2D , the crush cans  20 ,  22 ,  24 , and also parts  186  and  96  are engineered to provide increasing crush strength from front to rear. Can  24 , brackets  186  and underfloor longitudinal member  96  initiate at sufficiently high load to allow suitable crush of  20  and  22 . Accordingly, during the collision, the primary crush cans  20  are first longitudinally crushed from the pre-collision configuration of  FIG. 2A  to the configuration of  FIG. 2B  in which the primary crush cans  20  are crushed, but the secondary  22  and tertiary  24  crush cans are still substantially undeformed. As the collision continues to the configuration of  FIG. 2C , the secondary crush cans  22  are then crushed with the tertiary crush can  24  remaining substantially undeformed. As the collision continues to the configuration of  FIG. 2D , the tertiary crush cans  24  and the underfloor  96  and brackets  186  are next at least partially crushed. After the collision, the primary, secondary and tertiary crush cans  20 ,  22   24  remain in substantially the crushed configuration shown in  FIG. 2D . This sequential crush system has been considered highly advantageous since, dependent upon the extent of the collision, parts further back in the vehicle may not be damaged and may not need replacing and the cost of repairing relatively minor collisions can be minimised. Also, the sequential crush system is relatively predictable and parts of the vehicle further towards the rear where the occupants are located are not easily deformed such that the occupants  36 ,  38  are maintained safely in their occupant space  48  with only a negligible deformation of this space in relatively minor collisions. 
     The motor car  10  shown in  FIG. 1  and  FIGS. 2A to 2D  has performed very well in front impact tests and it is noted that this vehicle has a 4.7 litre V8 engine  40  which has a relatively short block  42  leaving a sizable gap  44  longitudinally between the engine block  42  and structural cross-members  46  joining the two sides of the front crash load absorption structure  18  in the region of the interface castings  26 . 
     However, in certain cases, it may be desirable from a product definition point of view to use an engine with a longer block whereby it may be more difficult to achieve good low acceleration of the occupants  36 ,  38 , especially the driver who has a more confined space due to the steering wheel and a smaller main front airbag than the front passenger during frontal impacts. 
     The present invention aims to alleviate at least to a certain extent the problems and/or address at least to a certain extent the difficulties of the prior art. 
     SUMMARY 
     According to a first aspect of the present invention there is provided a crash load absorption structure for a motor vehicle, the structure comprising a compressible load absorbing structure having a front portion and a rear portion and being arranged to compress under a crash load along a generally longitudinal direction, and a load transfer element for applying crash load to the load absorbing structure at a location part-way along the load absorbing structure. 
     The load transfer element may apply the crash load directly to the load absorbing structure at the location part-way along the load absorbing structure. The load transfer element advantageously may promote a lower energy mode of compression or collapse of the load absorbing structure in a crash and may extend the duration of the acceleration pulse and/or increase the time that a motor vehicle takes to decelerate to zero velocity and/or provide a lower acceleration for the driver and/or other occupants during a crash. The load transfer element may advantageously affect frontal impact performance, such as in the United States of America Federal front impact test without being detrimental to the behaviour of the vehicle in other tests which the vehicle must pass such as an offset front impact test. Whereas prior thinking has been to engineer a sequential collapse such as in three stages sequentially from front to back in a frontal collision as shown in  FIGS. 2A to 2D , the load transfer element can initiate a compression or collapse/crushing part-way along the load absorbing structure early on in the crash sequence and at low load. Given that the crash sequence is not necessarily sequential in stages e.g. from front to back through primary, secondary and tertiary collapsible structures in at least some embodiments in accordance with the invention, good performance can nevertheless be achieved. This jump away from prior thinking in the present invention is considered highly innovative. The acceleration of the driver during the deceleration of a crash may therefore surprisingly be lowered and the likelihood of occupant injury is lowered. Many occupant criteria are generally linked to acceleration. 
     Each of the three crush stages requires a certain amount of energy to overcome its initiation load. In the prior three-stage sequential collapse, for a particular vehicle weight, the remaining inertia available after crush of the first two stages may be insufficient to overcome the tertiary stage initiation load. This results in an increased deceleration of the vehicle as it is approaching zero velocity, which is not likely to provide such good performance for occupant injury levels. The load transfer element causes the tertiary crush stage initiation to occur earlier in the crash sequence whilst there is still ample inertia available to overcome its initiation load. The short blip in force due to this earlier initiation has a less detrimental effect on the occupant deceleration than the prior arrangement, hence lower occupant injury levels. 
     According to a second aspect of the present invention there is provided a crash load absorption structure for a motor vehicle, the structure comprising a compressible load absorbing structure having a front portion and a rear portion and being arranged to compress under a crash load along a generally longitudinal direction, a structural joint being located within the compressible load absorbing structure, the joint being between at least two structural members, and a load transfer element which is arranged to promote breaking of the structural joint during vehicle crash. 
     The promotion of breaking of a structural joint between two structural members is advantageous in certain circumstances. It can result in a longer duration for the deceleration of the vehicle to zero velocity and a lower acceleration for the driver during a frontal impact. The structural joint may be between a front lower sub-frame member, and an upper structural member, such as part of a suspension tower assembly and/or an upper wishbone member or casting, in which case the lower sub-frame member may be suitable for the location thereon of at least one lower suspension wishbone, and both of the lower sub-frame member and upper structural element may be solid castings or of other construction making them substantially rigid and uncrushable during vehicle crash. The load absorbing structure may be a longitudinal structure incorporating one of these members, such as the upper structural member, and may have compressible elements either sides of it, such as in front of and behind it, longitudinally in line. The promotion of breaking of the structural joint by the load transfer element is highly advantageous since it has been found that the length of the load transfer element can be tuned to affect the time at which it receives load during collision and therefore the time at which it transfers load to the load absorbing structure, such as the upper structural element thereof, so that the point or time in the collision at which the structural joint breaks can be tuned, which is useful when modifying or engineering new vehicle platforms. This, in turn, can enable the behaviour of parts of the load absorbing structure distant from the point at which the crash impact is applied to the load absorbing structure to be tuned so as to allow more easily a compression thereof earlier in the collision sequence and this may advantageously result in a longer duration of collision pulse and lower acceleration forces on the driver and/or passengers of the vehicle. 
     The structure may include a structural joint located within the compressible load absorbing structure, the joint being between at least two structural members, the load transfer element being arranged to promote breaking of the structural joint during vehicle crash. 
     A said structural member may comprise a sub-frame member which is substantially uncrushable during vehicle crash. 
     A said structural member comprises a suspension tower assembly, or part of a suspension tower assembly such as a wishbone mounting member. 
     The structural joint may include at least two substantially flat mating faces. 
     The structural joint may include four said mating surfaces arranged to mate generally within the same plane or substantially parallel planes with groups of two said mating faces being spaced apart by a gap. 
     The gap may be formed by a generally circular bore formed through the structural joint, a longitudinal axis of the bore being generally parallel to the plane or planes of mating surfaces of the joint. 
     At least one, preferably two or four, fasteners (such as bolts) may be provided for clamping each two mating faces together. The structural joint includes in one example two lots of two such fasteners, each two said mating faces of part of the joint being joined by two such fasteners. 
     The load transfer element may be secured to a structural member, the structural member preferably being substantially uncrushable during vehicle crash. 
     The load transfer element may be arranged to apply load to the load absorbing structure at a location part-way along the uncompressed load absorbing structure. 
     The compressible load absorbing structure may include at least one elongate tubular-walled member which is arranged to absorb energy by crushing along a longitudinal direction thereof. 
     At least one said tubular-walled member may be hollow or may contain hollow cells. 
     At least one said tubular-walled member may be arranged to crush and deform permanently. 
     At least one said tubular-walled member may be a crushable metal can-like structure. 
     The compressible load absorbing structure may comprise a plurality of distinct crushable portions, the distinct crushable portions being arranged to crushably deform at different applied crush loads to one another. 
     The distinct crushable portions may be arranged in an elongate configuration one behind the other in a longitudinal crushing direction. 
     Three said distinct portions may be arranged one behind the other in the longitudinal crushing direction. 
     Two said distinct crushable portions may be connected substantially directly to one another. 
     Two said distinct crushable portions may be spaced apart by a substantially uncrushable rigid structural member, such as a wishbone casting member for holding an end of a suspension wishbone. 
     The load transfer element may be arranged to extend in a direction generally parallel to a said elongate tubular-walled member. 
     The load transfer element may have one end fixed to a substantially rigid structural member and the load transfer element may have a free cantilevered distal end opposite to the end fixed to the substantially rigid structural member. 
     The load transfer element may, at a position approximately half way along its length, be fixed to the crushable load absorbing structure. 
     The substantially rigid structural member may comprise an upper wishbone mounting member. 
     The load transfer element may be arranged to begin transmitting load to the load absorbing structure part-way through compression of the load absorbing structure. The point at which the load transfer element begins transmitting load to the load absorbing structure may be during or at the end point of crushing of a first one of said distinct crushable portions to be crushed during vehicle crash. 
     The load transfer element may have an end located part-way along a said elongate tubular wall element which is arranged to crush before other said tubular wall elements during vehicle crash. 
     The load transfer element may have a front end positioned part-way along a front-most said tubular wall element. 
     The load transfer element may have a load surface arranged to receive load from an object into which a motor vehicle is to be crashed, the load surface being located longitudinally between front and rear ends of the compressible load absorbing structure. 
     The load surface may be at least partially curved. This curving of the load surface is advantageous in that it may prevent the load surface from catching on a deforming/crushing or otherwise in relative terms moving adjacent part of the load absorbing structure. 
     The compressible load absorbing structure may be arranged to compress at least partially by way of a permanent crushing action. 
     The crash load absorption structure may comprise part of vehicle front crash load absorption structure. 
     According to a further aspect of the present invention there is provided a vehicle including a crash load absorption structure in accordance with one or more of the previous aspects of the invention. 
     In this case, two said crash load absorption structures may be located spaced apart and preferably alongside one another. 
     The vehicle may include a vehicle engine located at least partially between the crash load absorption structures. 
     At least one structural member may extend across between the crash load absorption structures at least partly directly in front of the engine. 
     The present invention may be carried out in various ways and two embodiments of crash load absorption structures for motor vehicles in accordance with the invention will now be described by way of example only and with reference to the accompanying drawings in which: 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a schematic side view of a prior art motor vehicle undergoing a United States Federal front impact test; 
         FIGS. 2A to 2D  are perspective views showing part of the prior art motor vehicle of  FIG. 1  and how a front crash load absorption structure of the vehicle is arranged to crush sequentially in three steps during a substantial front impact; 
         FIG. 3  is a partial quarter perspective and partially sectioned view of a crash load absorption structure for a motor vehicle in accordance with a first embodiment of the present invention; 
         FIG. 4  is a view of the arrangement of  FIG. 3  but with certain body panels and other components including a load transfer element not shown, and with certain other elements, such as suspension wishbones and front suspension hub carrier/suspension upright shown; 
         FIG. 5  is a view of the embodiment of  FIG. 3  but with many parts not shown for the purposes of clarity, and with a modified load transfer element thereof modified so as to form a second embodiment of a crash load absorption structure for a motor vehicle in accordance with the invention; 
         FIG. 6  is a side view of part of the components shown in  FIGS. 3 to 5 ; 
         FIGS. 7A and 7B  are perspective views from behind and in front, respectively, of the load transfer element of  FIG. 5  showing in detail how it is connected to an interface casting and upper wishbone casting; 
         FIGS. 8A and 8B  are perspective views from behind and in front, respectively, of the load transfer element of  FIGS. 5 ,  7 A and  7 B; 
         FIGS. 9A to 9D  show a simulated crash sequence for the second embodiment of  FIGS. 5 and 7A  to  8 B; 
         FIGS. 10A to 10D  show a simulated crash sequence for the first embodiment of  FIG. 3 ; 
         FIGS. 11A and 11B  are computer modelling of average B-post acceleration and velocity (i.e., average of measured left and right B-posts to damp out noise) during United States of America Federal front impact tests for a 50 th  percentile driver at 35 miles per hour (15.6 meters per second); 
         FIG. 11C  is a graph of vehicle B-post velocity curves for the United States Federal front impact test for a 50 th  percentile driver at 35 miles per hour (15.65 meters per second) both for a computer aided engineering prediction for the second embodiment of  FIGS. 5 and 7A  to  9 D without the load transfer element thereof, and as actually tested with the load transfer element fitted; and 
         FIGS. 12A to 12D  are Madymo (trade mark) crash dummy simulations for the collisions of  FIGS. 10A to 10D  and  9 A to  9 D. 
     
    
    
     DETAILED DESCRIPTION 
     As shown in  FIG. 4 , in a first embodiment of a crash load absorption structure  18  in accordance with the present invention, the structure  18  and motor car  10  are generally similar to that shown with reference to  FIGS. 1 to 2D . Therefore the same reference numerals are used in this description of the preferred embodiments to those used with reference to  FIGS. 1 to 2D  in order to denote the same or similar components. One difference which will be seen in  FIG. 4  is that the engine  40  of the preferred embodiments is substantially larger than that shown in  FIGS. 2A to 2D  and its block  42  is substantially longer, and this is due to the fact that the engine in the preferred embodiments is a 6 litre engine with a V12 configuration, with the extra two cylinders in each cylinder bank in particular making the block  42  substantially longer. Although the secondary crush can  22  is 38 mm longer in the preferred embodiments than in the arrangements shown in  FIGS. 2A to 2D , this longer secondary crush can  22  being 96 mm long. The lengths of the primary crush can  20  and tertiary crush can  24  are the same in the preferred embodiments of  FIGS. 3 to 10D  as the equivalent components in  FIGS. 2A to 2D  at 343 mm and 187 mm, respectively, of crush length between the substantially uncrushable cast components at either end thereof, i.e. between a front interface member  50  and the interface casting  26 , and the upper wishbone casting  28  and the rear interface casting  32 , respectively. This means that the front  48  of the engine block  42  is further forwards in the preferred embodiments relative to the tertiary crush can  24  than in the arrangement of  FIGS. 2A to 2D . 
     Additionally, as shown in  FIGS. 3 and 10A  to  10 D, in this embodiment, a load transfer element or pusher element  52  is provided secured to a forward facing surface  54  of the upper wishbone casting  28 . It will be noted that the load transfer element  52  is not shown in  FIG. 4  or  FIG. 6  for the purposes of clarity. The load transfer element  52  is a solid bar of aluminium alloy which extends from the upper wishbone casting  28  all of the way along underneath the secondary crush can  22 , forward past the interface casting  26  and then along underneath the primary crush can  20 . As shown in  FIG. 10A , in the undeformed configuration of the front crash load absorption structure  18  the load transfer element  52  extends along to a position under the primary crush can  20  which is about one quarter to one third of the distance along the primary crush can  20  between the interface casting  26  and the front interface member  50 . This distance can be tuned in other embodiments to change the point at which the load transfer element starts transferring load. The load transfer element  52  has a flat front face member  56  and includes a first main portion  58  which is straight and horizontal and extends rearwardly from the flat front face member  26 , about two thirds of the way from the flat front face member  56  to the forward facing surface  54  of the upper wishbone casting  28 . The first main portion  58  merges into a slightly upwardly and rearwardly inclined portion  60  and then into a short horizontal straight rear portion  62  which attaches to the forward facing surface  54  of the upper wishbone casting  28 . This configuration means that the load transfer element  52  is spaced downwardly away from the primary crush can  20 , interface casting  26  and secondary crush can  22 . 
     As shown in  FIG. 10A , (and  FIG. 10D  which shows the upper wishbone casting  28  broken way from a lower sub-frame member  64 ), the upper wishbone casting is joined to the lower sub-frame member at a structural joint  66 —this is also shown in  FIG. 6 . The structural joint  66  consists of two planar surface interface joints  68 ,  70 , which are in the same plane or substantially the same plane as one another, between two pairs of substantially planar surfaces  72 ,  74  and  76 ,  78  (see  FIGS. 10C and 10D  as well as  FIG. 6 ). The planar surface interface joints  68 .  70  are spaced apart by a cylindrical gap  80  ( FIG. 6 ) through which a steering rack  82  of the motor car  10  passes ( FIG. 10A ). It will be appreciated that the steering rack  82 , wishbones  30  and lower wishbone  31  ( FIG. 3 ) are connected via pivots  33 ,  35  to a hub carrier and a spring/damper strut  37  extends from near lower part  39  of the lower wishbone  31  as does a front roll bar  41  so as to provide steerable front double wishbone suspension. A top end portion  43  of the strut  37  is attached to or sits in a top  45  of suspension tower  182 . 
     Two fastening bolts (not shown) which are M12 grade 10.9 bolts, pass vertically through the structural joint  66  through bores (not shown) in the lower sub-frame member  64  into threaded bores (not shown) in the upper wishbone casting  28 , each planar surface interface joint  68 ,  70  having two of said bolts and bores spaced apart from one another laterally. It will be noted that the load transfer element  52  is attached to the forward facing surface  54  of the upper wishbone casting  28  just above the front planar surface interface joint  70  ( FIG. 6  where the load transfer element  52  is not shown for the purposes of clarity—see also  FIG. 10A ). 
     The primary can  20  is a hollow octagonal tube formed with three cells (not shown) by virtue of two internal horizontal plates extending between the top and bottom edges  84 ,  86  of respective outer  88  and inner  90  vertical wall parts thereof. The material of the primary crush can  20  is three millimeter 6060T7 alloy with a yield strength of 140 MPa. The secondary crush can  22  is a rectangular tube having three cells (not shown) formed by two horizontal plates extending across between outer  92  and inner  94  vertical walls of the crush can  22  and is made of three millimeter 6060T6 alloy with a yield strength of 200 MPa. The tertiary crush can  24  is a hexagonal tube with only one cell, i.e. it is hollow with no internal plates, and has a wall thickness of 2.4 mm and is also of 6060T6 alloy. An under floor longitudinal member  96  extends rearwardly from a lower portion  98  of the front structure mounting member  34 . The under floor longitudinal member  96  is a rectangular hollow tube with 2 mm wall thickness and is of 6060T6 alloy. During vehicle crash, the primary crush can  20 , secondary crush can  22 , tertiary crush can  24 , and under floor longitudinal member  96  are arranged to deform permanently with a crushing action to absorb the energy of the vehicle during the crash. In contrast, the front interface member  50 , interface casting  26 , upper wishbone casting  28 , rear interface casting  32  and lower sub-frame member  64  are substantially rigid and uncrushable. The cans  20 ,  22 ,  24  and underfloor longitudinal member  96  are all tuneable in alloy grade and wall thickness in order to suit other applications in other types of vehicle, as required. 
       FIGS. 10A to 10D  show sequentially a collision in which the vehicle  10  is projected at 35 mph (15.65 meters per second) straight into a solid immovable rigid object  16  ( FIG. 1 ) with its flat front wall  16  perpendicular to the direction of projection of the vehicle  10 . The collision is simulated in these figures using a computer aided engineering finite element analysis model in which the model has been correlated first with the load transfer element  52  absent between an actual and CAE collisions at 25 mph (11.18 meters per second), that correlated finite element model then being analysed at 35 mph and the load transfer element  52  added to the model. 
       FIG. 10A  shows a front portion  11  of the vehicle including the front crash load absorption structure  18  at a time 0 seconds into the collision, i.e. at the actual point of impact of the vehicle into the substantially rigid immovable object  16 .  FIG. 10B  shows the front portion  11  of the motor car at a time 10 ms into the collision when it will be seen that a front plinth  100  and front bumper structure  102  have been compressed but there is no discernable compression of the front crash load absorption structure  18  including the primary  20 , secondary  22 , tertiary  24  crush cans or under floor longitudinal member  96 . In this position, the load transfer element or pusher element  52  has no effect since it is cantilevered forwards from the front wishbone casting  28  and its flat front face member  56  is not taking load. 
       FIG. 10C  shows the collision at a time of  35 ms into the collision pulse at a point in time when the front flat face member  56  of the load transfer element  52  suddenly is in collision with the substantially rigid immovable object  16  through what is left of the front bumper structure  102  (which is relatively insignificant from the point of view of forces in this collision). It will be seen that at this point in time, the primary crush can  20  is substantially or fully at the end of its crushing action but the secondary  22  and tertiary  24  crush cans have not yet started to crush. At this point in time therefore, or shortly before or after it, the substantially rigid load transfer element  52  directly places a substantial load onto the front crash load absorption structure  18  at a point which is part way along what was the undeformed structure of  FIG. 10A , and indeed what is still partway along the deformed structure of  FIG. 10C , namely at the upper wishbone casting  28 . The application of this substantial force by the load transfer element  52  to the upper wishbone casting  28 , causes the structural joint  66  to break due to breaking of the four M12 bolts (not shown) holding the structural joint  66  together, the force applied by the load transfer element  52  to the upper wishbone casting  28  being close to and parallel to the plane of the planar surface interface joints  68 ,  70 . The substantially rigid upper wishbone casting  28  is therefore able to break away from the lower sub-frame member  64  before the secondary crush can  22  has compressed significantly. The front portion  11  of the motor car  10  then changes to the configuration shown in  FIG. 10D  at a point in time approximately 67.5 ms into the collision pulse in which it will be seen that the secondary crush can  22  is generally undeformed, but the tertiary crush can  24  is substantially deformed. The early promotion of crushing further back in the load absorption structure  18  namely at the tertiary crush can  24  is, surprisingly, highly advantageous and the breaking of the structural joint  66  helps with this. 
       FIGS. 11A and 11B  are graphs showing acceleration in G and velocity in meters per second for the collision shown in  FIGS. 10A to 10D  as well as a collision for an identical model but with the load transfer element  52  removed. The graphs in solid lines  104 ,  106  are for the model of  FIGS. 10A to 10D  and the graphs in solid lines with sideways hatching  108 ,  110  are for the collision with the load transfer element  52  absent from the model. These two graphs are for average vehicle B-post data. Madymo (trade mark) crash dummy prediction software for a 50 th  percentile driver  114  restrained by seatbelt  116  and airbag  118  can then be used to compute occupant parameters from the B-post data, as simulated in  FIGS. 12A to 12D .  FIG. 12A  is 20 ms into the collision pulse,  FIG. 12B  30 ms into the collision pulse,  FIG. 12C  40 ms into the collision pulse and  FIG. 12D  50 seconds into the collision pulse. The B-post graphs predict a time to zero velocity of 55 ms without the load transfer element  52  but 65 ms with the load transfer element as shown in  FIGS. 10A to 10D . The likelihood of occupant injury is therefore improved (i.e., lowered) and peak B-post acceleration is significantly lower too. 
       FIGS. 7A to 9D  and also  FIG. 5  show a slightly different embodiment in which the load transfer element  52  has a slightly modified shape in order for a front  120  thereof to have clearance above an engine air intake air box  122  for the engine  40 . The load transfer element  52  in this embodiment is also attached part way along its length to the interface casting  26  which is slightly modified for the purpose. The transfer element  52  has weight reduction channels  126 ,  128  formed in a rear main horizontal portion  130  thereof, as well as a rear mounting through-bore  131  and two forward mounting through-bores  134 ,  136  and is otherwise a solid bar of aluminium alloy which is substantially rigid during vehicle collision. The rear main horizontal portion  130  of the load transfer element  52  abuts against the forward facing surface  54  of the upper wishbone element/casting  28  and is held in position thereagainst by an L-shaped bracket  134  having a first bolt  136  passing through the rear bore  131  and a second bolt  138  secured into the upper wishbone casting  28 . Near the front of the main horizontal portion  130  of the load transfer element  52 , the load transfer element  52  is braced by being secured via a bracket  140  to the interface casting  26  by virtue of fasteners (bolts)  142  connecting the load transfer element  52  to the bracket  140  and fasteners/bolts  144  attaching the bracket  140  to the interface casting  26 . The rear main horizontal portion  130  of the load transfer element  52  merges via an upwardly and forwardly directed portion  148  into the front end portion  120  thereof. The load transfer element  52  has a front load accepting surface  150  which has a radiused top corner edge  152 , which advantageously prevents the crumpling/crushing primary can  20  from catching on the load transfer element  52  during crushing of the primary can  20 . 
       FIGS. 9A to 9D  show a collision for this second embodiment driven into the flat front wall  14  of the substantially rigid immovable object  16  at 35 mph (15.65 meters per second). In  FIG. 9A , this is the point in time when the collision begins. In  FIG. 9B , the front plinth  100  and front bumper structure  102  are substantially compressed but the primary  20  secondary  22  tertiary  24  crush cans and the under floor longitudinal member  96  are not compressed. Further into the collision, as shown in  FIG. 9C , the front crush can or primary crush can  20  is substantially compressed and the secondary crush can  22  tertiary crush can  24  and under floor longitudinal member  96  are substantially undeformed. The front face  150  of the load transfer element or pusher  52  is just about to come into contact with the flat front wall  14  of the substantially rigid immovable object  16  and the radiused top edge  152  has ensured that the crumpled primary crush can  20  has not caught on and become entangled with the load transfer element  52 . At this point in time in this actual, (i.e. non-simulated) crash sequence, the load transfer element  52  is just about to transfer suddenly substantial load to the front face  54  of the upper wishbone casting  28 . Although this substantial force promotes breakage of the structural joint  66  between the upper wishbone member  28  and the front sub-frame member  64 , the joint  66  does not actually break on this occasion due to friction in the mating surfaces  72 ,  74 ,  76 ,  78  of the joint  66 . Substantial load is therefore transferred by the load transfer element  52  directly to the front crash load absorption structure  18  at a position partway along its length, namely at the front surface  54  of the upper wishbone casting  28 . Part of this force is transferred through the substantially rigid and uncrushable upper wishbone casting  28  to the tertiary crush can  24  but part of the force is also transferred through the structural joint  66  and the substantially rigid and uncrushable lower sub-frame member  64  and via the front structure mounting member  34  to the under floor longitudinal member  96  which is rearwardly attached to a further structural member  160  of the body structure of the motorcar  10 . Accordingly, in the transition between the configuration of  FIG. 9C  to the configuration of  FIG. 9D  which is further into the collision, there is substantial crushing of the tertiary crush can  24  and the under floor longitudinal member  96  also crushes and the lower end  98  of the front structure mounting member  34  hinges backward to accommodate relatively rearward movement of the lower sub-frame member  64 . 
       FIG. 11C  is a velocity graph for the vehicle B-post  112  where the graph in a solid line  170  shows the velocity of the B-post in the actual test crash of  FIGS. 9A to 9D  and the graph in the dashed line is a computer aided engineering baseline simulation for the B-post with the load transfer element  52  absent. It can be seen that the velocity gradient is less steep in the region after approximately 42 ms into the crash pulse, thereby indicating a lower acceleration at the vehicle B-post  112  and the B-post reaches a zero velocity at a later time. Accelerations for the occupants are therefore also generally improved as can be predicted with the Madymo (trade mark) prediction software. The early transfer of the collision impulse to the tertiary crush can  24  and under floor longitudinal member  96  advantageously and surprisingly allows the length of duration of the acceleration pulse to be extended and initiates a collapse further back on these components earlier on in the collision at a relatively low load. It is noted that this is despite the fact that the secondary can  22  is not significantly crushed in the collision between the configurations of  FIGS. 9C and 9D . The configuration of  9 D (and indeed also the configuration of  10 D) is when the components are fully crushed in the collision, before slight spring-back of the vehicle. 
     A further feature is that as shown in  FIGS. 5 and 6 , a shock tower system  182  is secured on top of the upper wishbone casting  28  and is secured by strong brackets  184 ,  186  to a generally horizontal structural member  188  known as a “shotgun member”, the shotgun member  188  being firmly secured to a middle substantially uncrushable A-post member (not shown) rearwards behind member  192 . As can be seen from  FIGS. 9D and 10D , the brackets  184 ,  186  remain holding onto the shotgun member  188  so that the shock tower  182  does not noticeably move backwards relative to the body of the vehicle  10  during the collision, and the shock tower  182  does not break off the shotgun member  188 . This advantageously prevents the shock tower  182  from undesirably colliding with brake components  194  of the motor car  10  which could undesirably cause the transmission of a sudden very high load through the motor car&#39;s brake pedal (not shown) which could hurt a foot of the driver which is on the brake pedal and attempting to slow the motor car prior to and upon collision. 
     A further advantage of the load transfer element  52  of the preferred embodiments is that its length can easily be adjusted to tune the collision characteristics for modified or newly engineered vehicle platforms, such as when engine sizes are changed. The material of the load transfer element  52 , which in the above examples is 6082 alloy in T6 temper, and its shape and configuration can also be changed/tuned for other applications. 
     The presence of the load transfer element  52  provides the motor car  10  with very good collision characteristics when in a frontal impact into a solid immovable object such as a test impact barrier or an object like a steel reinforced bridge support at the side of a road, and the road transfer element  52  does not negatively affect the collision characteristics of the motor car  10  under different crash conditions, such as during offset collisions or side impacts. 
     The present invention may be carried out in various ways and various modifications are envisaged to the embodiments described without extending outside the scope of the invention as defined by the accompanying claims.