Abstract:
A vehicle chassis that incorporates the engine structure, transaxle structure and a backbone structure provided as a unitary structure onto which other components of a vehicle, such as suspension, steering, body and crash absorbers may be attached. The backbone structure is a closed tubular structure in which a relatively rigid drive shaft can be supported for rotational power delivery between the engine and the transaxle. Several variations of the basic chassis embodiment are disclosed to accommodate rear wheel drive, front wheel drive, four wheel drive, as well as internal combustion, electrical and hybrid powered vehicles. Front and rear energy absorbing crash structures are rigidly fixed to front and rear sub-frames of the vehicle chassis.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation-in-part of U.S. patent application Ser. No. 12/019,490 filed on Jan. 24, 2008. The disclosure of the above application is incorporated herein by reference. 
     
    
     FIELD 
       [0002]    This invention is related to the field of automotive chassis design and more specifically to the area of interchangeable chassis for use with many models of vehicles. 
       BACKGROUND 
       [0003]    The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
         [0004]    Traditionally, vehicles are made up on framed chassis or on a rigid uni-body chassis. These two types of chassis have both advantages and disadvantages when compared to each other and are well known in the automotive industry. A main deficiency attributed to each of the traditional chassis types is that they are not readily adaptable to a wide variety of vehicles without forcing major and expensive redesign work for each vehicle. As a result, almost every model of vehicle has a unique chassis that is unusable for other vehicle designs. The present invention is based on an attempt to address the disadvantages known in the two commonly used chassis types and also to provide a simple chassis that can be used in a wide variety of vehicle designs. 
       SUMMARY 
       [0005]    The unique features of this invention include the combination of a rigid backbone structure connecting front and rear structures (in the preferred embodiment, the front engine and rear transaxle), in combination with the front and rear suspensions rigidly affixed to the front and rear structures (or backbone mounting surfaces) such that suspension loads (in the preferred embodiment) stress the engine block and transaxle case, to create a complete, self-supporting chassis without the need for a separate frame, or the need to attach the front and rear suspension subassemblies to a rigid uni-body. In addition, the front and rear structures incorporate energy absorbing crash boxes affixed to the front and rear structures so that crash impact energy is transferred from the bumper beams, absorbed by the deformable energy boxes, and reacted by front and rear structures that transfer loads to the rigid backbone. 
         [0006]    The problems solved by the present invention include an ability to attach different bodies, or body styles to the same uni-chassis; an ability to scale the uni-chassis to different size vehicles (e.g., wheelbase) by increasing or decreasing the length of the backbone structure. Weight savings are provided by using the backbone to serve the functions of (1) torsion and bending support for the chassis and (2) a torque tube to support drive torque from the engine to transaxle through a quill shaft mounted inside the backbone. Other problems solved by the present invention include an ability to de-couple chassis loads (e.g., ride and handling loads including drive, braking, steering) from (1) body loads and (2) absorb impact (crash) loads through the crash boxes to the backbone rather than the body; (3) an ability to create a “rolling chassis”, before installation of the body structure; (4) an ability to reduce weight by stressing the normally unstressed engine and transaxle structures with chassis loads thereby reducing chassis structure and weight; and (5) an ability to optimize total vehicle weight, weight distribution and minimize polar moment of inertia (about the yaw axis) through minimization of weight and location of the major vehicle masses within the wheelbase of the vehicle. 
         [0007]    Advantages of the present invention over prior constructions are simplicity (minimizing cost and manufacturing investment), weight reduction, reduction in polar moment of inertia about the yaw axis, and an ability to adapt to different bodies and body styles, and to create a rolling chassis. Other advantages include elimination of a traditional frame and its associated weight and cost, or the need to transfer suspension loads into a uni-body structure, which also effects weight and cost; and flexibility in creating unique chassis for different engines, transaxles and suspension components while maintaining the same uni-chassis architecture. Thus, a series of modules could be created for front, rear and backbone structures, allowing the creation of many different chassis using the three essential building blocks (front, backbone, and rear structures along with front and rear energy absorbing crash boxes). Still further advantages are an ability to scale the uni-chassis to different sizes and de-couple chassis loads from body loads. The backbone structure also provides a secure environment to pass electrical wiring, fuel lines and brakes lines through the bearing supports so that these components are protected from the environment and impact (crash) events. 
         [0008]    The sales and market potential of this invention are particularly well suited to specialty vehicles since multiple vehicles can be made off the same uni-chassis as engineering and tooling investment can be spread among multiple models. This invention is also particularly well suited for Battery Electric Vehicles (BEVs) and Plug-in Hybrids (PHEVs), since the battery pack can be mounted inside the backbone—eliminating the need for a separate battery box—thus reducing cost and weight. Manufacturing investment is low. The uni-chassis is scaleable to different sizes. The uni-chassis is modular, in that different front, rear and backbone modules and energy absorbing crash boxes can be combined to create different chassis. The uni-chassis can be sold as a complete rolling chassis, or as three independent modules plus front and rear crash boxes, to the aftermarket, allowing others to create unique vehicles. For high volume production, this invention continues to offer advantages of lower cost, weight and manufacturing investment. 
         [0009]    Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
     
    
     
       DRAWINGS 
         [0010]    The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
           [0011]      FIG. 1  is a schematic plan view of a universal chassis according to one example of the present teachings and shown on an exemplary vehicle; 
           [0012]      FIG. 2   a  is a detail top plan view of the universal chassis of  FIG. 1 ; 
           [0013]      FIG. 2   b  is a detail side view of the universal chassis of  FIG. 1 ; 
           [0014]      FIG. 2   c  is a detail bottom plan view of the universal chassis of  FIG. 1 ; 
           [0015]      FIG. 3   a  is a perspective view of the universal chassis of  FIG. 1  illustrating a backbone structure coupled to a front and rear structure according to one example; 
           [0016]      FIG. 3   b  is a cross-section of the bearing support taken along line  5 - 5  of  FIG. 3   a  according to one example; 
           [0017]      FIG. 4  is a cross-sectional view of the universal chassis taken along line  4 - 4  of  FIG. 3   a;    
           [0018]      FIG. 5  is a front perspective view of a bell housing associated with the universal chassis of  FIG. 3 ; 
           [0019]      FIG. 6  is a cross-sectional view of the bell housing taken along line  6 - 6  at  FIG. 5 ; 
           [0020]      FIG. 7  is a side view of the universal chassis shown coupled to the rear structure depicting the rigid attachment of the transaxle shown in  FIG. 2   a;    
           [0021]      FIG. 8   a  is a detail side view of the transaxle attachment to the rear structure of  FIG. 7 ; 
           [0022]      FIG. 8   b  is a detail rear view of the transaxle and rear structure; 
           [0023]      FIG. 8   c  is a detail top plan view of the transaxle and rear structure; 
           [0024]      FIG. 9   a  is a partial front view of the front structure of the universal chassis of  FIG. 3   a  and shown with suspension elements represented as being rigidly attached to the front structure; 
           [0025]      FIG. 9   b  is a partial side view of the front structure and engine; 
           [0026]      FIG. 9   c  is a partial bottom plan view of the front structure; 
           [0027]      FIG. 10  is a cross-sectional view of an exemplary universal chassis represented as being associated with a vehicle body; the body is isolated from the Uni-Chassis by body mounts. As shown, the body floorpan encapsulates the backbone with a floorpan tunnel that is capped from the bottom by an undertray, so as to create a closed section. This is done so that side impact forces to the body during crash impacts are transferred to, and reacted by the Uni-Chassis backbone. 
           [0028]      FIG. 11  is a top view of a universal chassis shown with body mounts according to additional features; 
           [0029]      FIG. 12  represents the universal chassis according to the present teachings that accommodates various rear wheel drive configurations; 
           [0030]      FIG. 13  represents the universal chassis according to the present teachings that accommodates various front wheel drive configurations; 
           [0031]      FIG. 14  represents the universal chassis according to the present teachings that accommodates various four wheel drive configurations; 
           [0032]      FIG. 15  represents the universal chassis according to the present teachings that accommodates an electrically powered four wheel drive configuration; 
           [0033]      FIG. 16  represents the universal chassis according to the present teachings that accommodates a plug-in series hybrid type powertrain configuration; 
           [0034]      FIG. 17  represents the universal chassis according to the present teachings that accommodates a dual-mode hybrid type configuration; 
           [0035]      FIG. 18  represents a Finite Element model of the front engine, rear transaxle and backbone reacting torsional and bending suspension loads; 
           [0036]      FIG. 19  is a front perspective view of the front structure of the universal chassis constructed in accordance to one example of the present disclosure; 
           [0037]      FIG. 20  is a cross-sectional view taken along lines  20 - 20  of  FIG. 19 ; 
           [0038]      FIG. 21  is a bottom perspective view of the front structure of  FIG. 19 ; 
           [0039]      FIG. 22  is a front perspective view of the rear structure of the universal chassis constructed in accordance to one example of the present disclosure; 
           [0040]      FIG. 23  is a cross-sectional view taken along lines  23 - 23  of  FIG. 22 ; and 
           [0041]      FIG. 24  is a rear perspective view of the rear structure of  FIG. 23 . 
       
    
    
     DETAILED DESCRIPTION 
       [0042]    The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. 
         [0043]    While the present invention is summarized above as being applicable for several types of vehicles, it is exemplified herein as being installed in a conventional front engine vehicle with a rear transaxle. 
         [0044]    Referring initially to  FIGS. 1-2   c , a plan view of a unitary or uni-chassis constructed in accordance to the present teachings is shown and generally identified at reference numeral  10 . The uni-chassis  10  is shown associated with an exemplary vehicle  12 . The uni-chassis  10  includes five major assemblies: a front structure  14  which is coupled to a front energy absorbing crash structure XX, a rear structure  16  which is attached a rear energy absorbing crash structure YY, and a backbone structure  18 . The front structure  14  is rigidly attached to an engine  20 . Suspension loads are fed directly to the engine  20  through rigid engine mounts ZZ (located substantially near the front of the engine  20 , see also  FIG. 21 ), such that the torsional and bending loads are transferred directly through an engine block  20   a  of the engine  20  to a front mounting flange  22 . 
         [0045]    The backbone structure  18  is rigidly attached to the front structure  14  through the front mounting flange  22  and rigidly attached to the rear structure  16  through a rear mounting flange  24 . The rear structure  16  is rigidly mounted to a transaxle  26 . Suspension loads are fed directly into the transaxle  26  through a rigid mount MM (located substantially near the rear of the transaxle  26 , see also  FIG. 24 ), such that the torsional and bending loads are transferred through a transaxle case  26   a  of the transaxle ( FIG. 24 ) to the rear mounting flange  24 . As shown in  FIG. 2   a , a front and rear mounting plate  28  and  30  may be incorporated to couple the front and rear mounting flanges  22  and  24  to the front and rear structures  14  and  16 , respectively. As shown in the finite element model  FIG. 18 , the engine block  20   a  and transaxle case  26   a  are of sufficient rigidity such that no other structural members are required to provide adequate chassis stiffness. Explained further, suspension loads are successfully received and accommodated by the engine block  20   a  at engine mounts ZZ and the transaxle case  26   a  at mounts MM. 
         [0046]    The front structure  14  includes the engine  20  rigidly attached to a front sub-frame  34 . In one example, the front structure  14  can be integrally defined with the front mounting plate  28 . Attached to the engine  20  and front sub-frame  34  are all the front chassis systems typically mounted to a chassis, including, but not limited to: a suspension system  36  with control arms  38 , springs and dampers  40 , knuckle and spindle  42 ; steering system  44  including rack and pinion  45  and tie rods; tire/wheel/brake assemblies  46  attached to the suspension spindle and knuckle; accessory drives including power steering pump, water pump, alternator, etc. (not specifically shown), attached to the engine  20  and front sub-frame  34 . Attached to the front structure  14  are the energy management boxes XX having laterally offset frame members that are rigidly fixed (such as by fasteners and/or welding) to the front structure  14  on one end and rigidly fixed to the bumper beam  55  on an opposite end. The energy management boxes XX are configured to ( FIG. 2   a ) deform and absorb front crash loads from a bumper beam SS; transfer them through the front structure  14 ; to be reacted by the backbone structure  18 . The energy management boxes XX are designed to absorb nominally 35 mph front impact loads. The energy boxes XX are bolted to the front structure  14 , such that frontal impact loads are transferred through the front structure  14  to the backbone structure  18 . The front structure  14  and backbone structure  18  have nominally twice the stiffness of the energy management boxes XX, so that in the majority of crash scenarios the front structure  14  and engine  20  remain undamaged. Optionally, the vehicle cooling system can be attached to the energy management boxes XX, and the bumper beam SS can be either bolted or welded to the energy management boxes XX, depending upon serviceability requirements. 
         [0047]    The rear structure  16  of the preferred embodiment, as shown in  FIG. 1 , consists of the transaxle  26  with a rear sub-frame  50  rigidly attached to it, and optionally, to the rear mounting flange  24  of the backbone structure  18 . Attached to the transaxle  26  and rear sub-frame  50  are all the rear chassis systems typically mounted to a chassis, including, but not limited to: a rear suspension system  52  including control arms  54 , springs and dampers, knuckle and spindle (not specifically shown); drive shafts  56 ; and tire/wheel/brake assemblies  58  attached to the knuckle. Coupled to the rear structure  16  are the energy management boxes YY (see also  FIG. 22 ) having laterally offset frame members that are rigidly fixed (such as by fasteners and/or welding) to the rear structure  16  on one end and rigidly fixed to a rear bumper beam TT on an opposite end. The energy management boxes YY are configured to deform and absorb rear crash loads from the rear bumper beam TT; transfer them through the rear structure  16 ; to be reacted by the backbone structure  18 . The energy management boxes YY are designed to absorb nominally 35 mph rear impact loads. The energy boxes YY are bolted to the rear structure  16 , such that rear impact loads are transferred through the rear structure  16  to the backbone structure  18 . The rear structure  16  and backbone structure  18  have nominally twice the stiffness of the energy management boxes YY, so that in the majority of crash scenarios the rear structure  16  and transaxle  26  remain undamaged. Optionally, the fuel tank (not specifically shown) can be attached to the rear structure  16 . 
         [0048]    With additional reference now to  FIGS. 3   a - 9 , the backbone structure  18  includes a main section  60  having the front mounting flange  22  and the rear mounting flange  24 . As described, the front and rear mounting flanges  22  and  24  can be coupled to the front structure  14  and rear structure  16 , respectively ( FIG. 1 ) by way of conventional fasteners. Alternatively, the backbone structure  18  can be partially or entirely coupled to the front and/or rear structures  14  and  16  by other methods, such as, but not limited to, welding. In addition, the backbone structure  18  can be integrally formed with the front and/or rear structures  14  and  16 . 
         [0049]    The main section  60  defines a tube  64  having a quill shaft  66  ( FIG. 4 ) rotatably disposed therewithin. The quill shaft  66  can be co-axial to a longitudinal centerline L of the tube  64 . The quill shaft  66  is attached at a front end to an engine output shaft  68  through a first coupler  70 . The quill shaft  66  is attached at a rear end to a transaxle input shaft  72  through a second coupler  74 . The quill shaft  66  is supported by isolated bearings  76  mounted inside and attached to the backbone structure  18 , in order to control run-out of the quill shaft  66 . The isolated bearings  76  are supported by bearing supports  78 . As depicted in the cross-section ( FIG. 3   b ), the bearing supports  78  incorporate dedicated slots that provide a secure passage for routing of fuel lines AA, electrical lines BB and brake lines CC from the front to the rear of the vehicle. These lines are isolated from the bearing support by grommets DD. This unique positioning of these lines in the slots protects them from external environmental elements (salt, water, corrosion, etc.) and prevents damage in the event of a vehicle crash. In one example, the front mounting flange  22  may be integrally formed with a bell housing  80 . The bell housing  80  can house a flywheel/clutch assembly  82 , starter motor RR, and also define a bleeder assembly  84  for a hydraulic clutch actuator EE. 
         [0050]    The primary function of the backbone structure  18  is to rigidly connect the front and rear structures  14  and  16  to form the uni-chassis  10 . The backbone structure  18  is a one-piece closed section tubular structure, and as shown in the preferred embodiment, has the tube  64  that defines a circular cross-section. The tube  64  may be changed in size and form to optimize backbone properties. The size, shape and material of the backbone structure  18  must be selected so that acting in unison with the front and rear structures  14  and  16 , the uni-chassis  10  provides sufficient torsional and bending rigidity and strength. Because the uni-chassis  10  does not incorporate a conventional frame, the backbone structure  18  forms the connection between the front and rear structures  14  and  16 . The chassis loads are therefore transmitted solely by the backbone structure  18  between the front and rear structures  14  and  16 . 
         [0051]    In a typical automotive application, the backbone structure  18  should provide approximately 10,000 ft-lb/deg. (minimally 4000) torsional stiffness and 25,000 lb/in (minimally 10,000) bending stiffness; and must have sufficient strength, such that it can withstand at least 2 g vehicle loads in bending and torsion (transmitted through the suspensions  38  and  52  of the front and rear structures  14  and  16 , respectively), without permanent yield. In one example, the tube  64  can define an outer diameter of between 6 and 10 inches, and preferably 8 inches. The tube  64  can be formed of a rigid lightweight material such as, but not limited to, aluminum. The tube  64  can have a wall thickness of substantially about 0.5 inch. As shown in  FIG. 18 , finite element modeling confirmed that an 8 inch diameter, 0.5 inch wall aluminum backbone will provide 13,000 ft-lbs/degree torsion and 47,000 lbs./inch bending stiffness—far exceeding the above mentioned requirements. 
         [0052]    The secondary function of the backbone structure  18  as shown in the preferred embodiment is to act as a torque tube to provide support for the transfer of torque from the engine  20  in the front structure  14  to the transaxle  26  in rear structure  16  through the quill shaft  66 . 
         [0053]    The backbone structure  18  may be flared out at the front (e.g. the bell housing  80 ) through the front mounting flange  22  to get around the flywheel/clutch assembly  82  to attach to the engine  20 . This bell housing  80  may be a separate part, but maintains backbone stiffness by being rigidly attached to the backbone structure  18 . Similarly, the rear of the backbone structure  18  can be flared to attach to the rear structure  16  through the rear mounting flange  24 . The backbone structure  18  may also incorporate additional holes, such as holes  86  ( FIGS. 3 ,  5  and  19 ) and cover plates, such as cover plates  88  ( FIG. 4 ) to provide access to the quill shaft  66  and/or the first and second couplers  70  and  74 . 
         [0054]    With reference to  FIGS. 10 and 11 , various exemplary body mounts  90  are shown. A vehicle body  92  includes a lateral beam or cross-member  94  coupled to the backbone structure  18 . As can be appreciated, the vehicle body  92  can comprise various body components, such as seats  96 . The cross-member  94  can be suitably attached to the backbone structure  18  at or near a torsional node defined in the tube  64 . The uni-chassis  10  of the present invention allows various loads associated with the vehicle body  92  to be substantially de-coupled from various loads associated with the uni-chassis  10 . A body tunnel  98  can be defined by the body  92 . The body tunnel  98  can accommodate the tube  64 , and is designed to interfere with the backbone tube, so that side impact crash forces on the body can be reacted by the backbone. 
         [0055]    While the preferred embodiment depicts a uni-chassis  10  utilizing the engine  20  as part of the front structure  14  and transaxle  26  as part of the rear structure  16 , connected by a backbone structure  18 , the uni-chassis concept can be applied to other powertrain arrangements. For example, a typical rear wheel drive (RWD) vehicle (such as the one shown in  FIG. 1 ) with front engine  20  and transmission and rear axle and drive shaft  56  can utilize the engine  20  and transmission as the core of the front structure  14  for attaching the front chassis systems, and the rear axle as the core of the rear structure  16  for attaching the rear chassis systems, connected by a backbone structure  18  incorporating a quill shaft  66  similar to that depicted in the preferred embodiment. 
         [0056]    The application of the uni-chassis concept to this, and other powertrain arrangements, including front wheel (FWD) and four wheel (4 WD) drive; are tabulated below: 
         [0000]    
       
         
               
             
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Alternative uni-chassis Powertrain Arrangements 
               
             
          
           
               
                   
                 Front Structure 
                 Backbone 
                 Rear Structure 
               
               
                   
                   
               
             
          
           
               
                 A. 
                 RWD 
                 Engine 
                 Engine to 
                 Transaxle 
               
               
                   
                   
                   
                 Transaxle 
               
               
                   
                   
                 Engine &amp; 
                 Transmission to 
                 Axle 
               
               
                   
                   
                 Transmission 
                 Axle 
               
               
                   
                   
                 Front Chassis 
                 Front Structure to 
                 Engine &amp; Transaxle 
               
               
                   
                   
                 Structure 
                 Engine 
               
               
                   
                   
                 Front Chassis 
                 Front Structure to 
                 Transaxle &amp; Engine 
               
               
                   
                   
                 Structure 
                 Transaxle 
               
               
                 B. 
                 FWD 
                 Engine &amp; Transaxle 
                 Transaxle to Rear 
                 Rear Chassis 
               
               
                   
                   
                   
                 Structure 
                 Structure 
               
               
                   
                   
                 Transaxle &amp; Engine 
                 Engine to Rear 
                 Rear Chassis 
               
               
                   
                   
                   
                 Structure 
                 Structure 
               
               
                 C. 
                 4WD 
                 Engine, Front Axle 
                 Engine to 
                 Transaxle 
               
               
                   
                   
                   
                 Transaxle 
               
               
                   
                   
                 Engine, 
                 Transmission to 
                 Rear Axle 
               
               
                   
                   
                 Transmission, Front 
                 Axle 
               
               
                   
                   
                 Axle 
               
               
                   
                   
                 Front Axle 
                 Front Axle to 
                 Engine &amp; Transaxle 
               
               
                   
                   
                   
                 Engine 
               
               
                   
                   
                 Front Axle 
                 Front Axle to 
                 Transaxle &amp; Engine 
               
               
                   
                   
                   
                 Transaxle 
               
               
                   
               
             
          
         
       
     
         [0057]    The uni-chassis concept is not limited in application to conventional powertrain technology. For example, an electric powertrain application ( FIG. 15 ) might use a front and/or rear motor for the front and rear structures, and the backbone structure to house the batteries, to create a two or four wheel drive (4 WD) electric vehicle. A hybrid powertrain ( FIG. 16 ) might use a front internal combustion engine and motor generator on a first end and an electric motor on an opposite end. Again, a backbone structure can house the batteries and connect front and rear structures. A dual mode hybrid powertrain ( FIG. 17 ) might incorporate a differential at one end and a dual mode electronic transmission incorporated in the backbone structure. Many other arrangements of new powertrain technologies can be applied to the uni-chassis concept, by using one or more of the powertrain elements e.g., engine, transmission or axle, to create the core of the front or rear structures and connect them with a backbone. 
         [0058]    An exemplary method of constructing a vehicle according to the present teachings will now be described. The present invention provides flexibility in creating a unique chassis for any given conventional vehicle (internal combustion engine, transaxle, suspension etc.) electric vehicle or hybrid vehicle while still maintaining the same uni-chassis architecture. In this way, a vehicle manufacturer (or assembler) can select a desired vehicle configuration and powertrain. A front and rear structure with front and rear energy management structure can then be assembled to accommodate the selected vehicle configuration and vehicle powertrain. A central backbone structure can be assembled between the front and rear structures to create a rolling chassis. During attachment of the central backbone between the front and rear structures, the operational components (e.g., quill shaft for conventional vehicle, battery for electric or hybrid vehicle), are suitably coupled or connected. The closed tube of the central backbone can be made to any desired length suitable for the desired application. The desired vehicle body can then be coupled to the rolling chassis. 
         [0059]    With particular reference now to  FIGS. 19-21 , additional features of the front structure  14  will be described in greater detail. The front structure  14  can generally include the front sub-frame  34 . The front sub-frame  34  can include an upper cross member  110 , a middle cross member  112 , and a lower cross member  114  all rigidly connected between front lateral frame members  120 . The upper cross member  110 , the middle cross member  112 , and the lower cross member  114  can all be rigidly affixed to the front lateral frame members  120  such as by way of rigid fasteners and/or welding. It will be appreciated that the front lateral frame members  120  may consist of a collection of rigidly connected frame components. Engine brackets  122  ( FIG. 21 ) are rigidly affixed between the lower cross member  114  and the engine block  20   a . Specifically, first ends of the engine brackets  122  can be welded to the lower cross member  114  while second ends of the engine brackets  122  are rigidly connected to the engine block  20   a  at the engine mounts ZZ. In the particular example shown in  FIG. 21 , the engine mount ZZ includes a flange that is bolted by way of bolts  130  into the engine block  20   a . In addition, bolts  132  ( FIG. 19 ) rigidly connect the front mounting flange  22 , the front mounting plate  28  and the engine block  20   a  of the engine  20  (see  FIG. 20 ). Bolts  132  can be arranged around the front mounting flange  22  for directly threadably mating into the engine block  20   a . The bolts  132  can extend through complementary bores defined in the front mounting flange  22  and the front mounting plate  28 . A pair of dowels  134  can additionally be located through the front mounting flange  22 , the front mounting plate  28 , and the engine block  20   a  of the engine  20 . The front sub-frame  34  can further comprise a pair of angled frame members  34   a  that are generally rigidly affixed between the front lateral frame members  120  and the front mounting plate  28 . 
         [0060]    The front mounting plate  28  comprises two pairs of outwardly extending arms  28   a  and  28   b  that nestingly and fixedly receive the angled frame members  34   a . The angled frame member  34   a  can be welded to the arms  28   a  and  28   b . The configuration facilitates accommodation of torsioned forces in the front structure  14 . 
         [0061]    With reference now to  FIGS. 22-24 , additional features of the rear structure  16  will be further described. The rear sub-frame  50  of the rear structure  16  can generally include an upper cross member  140 , a middle cross member  142 , and a lower cross member  144  all rigidly connected between a pair of rear lateral frame members  148 . The upper cross member  140 , the middle cross member  142 , and the lower cross member  144  are all rigidly attached to the respective rear lateral frame members  148  by way of fasteners such as bolts and/or welding. The rear lateral frame members  148  can comprise a collection of rigidly attached frame components. The rear mounting plate  30  can collectively comprise a first rear mounting plate  30   a  and a second rear mounting plate  30   b . The first and second rear mounting plates  30   a  and  30   b  are rigidly connected between the rear lateral frame members  148  and the rear mounting flange  24  by way of bolts  154 . As illustrated in  FIG. 23 , the bolt  154  can extend through the rear mounting plate  30   b , the rear mounting flange  24 , and a transaxle mounting flange  26   a  of the transaxle  26 . It will be appreciated that the mounting arrangement of the first rear mounting plate  30   a  may be rigidly attached in a similar manner. A transaxle mounting bracket  160  rigidly connects the rigid mount MM with the middle cross member  142 . In the example provided, the transaxle mounting bracket  160  is rigidly affixed to the transaxle  26  by way of bolts  162  extending through the rigid mount MM and into the transaxle  26 . 
         [0062]    Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the present invention can be implemented in a variety of forms. Therefore, while this invention has been described in connection with particular examples thereof, the true scope of the invention should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, the specification and the following claims.