Abstract:
A suspension for, and a method for suspending, a vehicle having a body is provided. The suspension includes a first suspension assembly and a second suspension assembly. The first suspension assembly extends between a first surface contact assembly and the body, and the second suspension assembly extends between a second surface contact assembly and the body. The first and second suspension assemblies each have a tranverse instant center. The first suspension assembly and the second suspension assembly are aligned so that a vertical centerline of each surface contact assembly lies within a transverse vertical plane that extends therebetween. The tranverse instant center of each suspension assembly is located within the tranverse vertical plane, below a roll center located within the tranverse vertical plane.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Technical Field  
           [0002]    This invention relates to vehicle suspensions in general, and to vehicular suspensions having vehicle roll and pitch control mechanisms, in particular.  
           [0003]    2. Background Information  
           [0004]    The suspension of a vehicle determines the ride characteristics of the vehicle &#39;such as its roll and pitch. The term “roll” refers to rotational movement of the vehicle body about a longitudinal axis of the vehicle. Roll is typically encountered during cornering. The term “pitch” refers to rotational movement of the vehicle body about a widthwise axis of the vehicle. Pitch is typically encountered during acceleration (acceleration “squat”) and during braking (braking “dive”).  
           [0005]    Vehicle suspension systems can be characterized as either active or passive. “Active” suspension systems typically adjust suspension elements during use in response to sensed operating conditions. Active suspension systems are often relatively complex, prohibitively expensive, or both. Passive suspension systems, on the other hand, typically include anti-roll or stabilizer bars, or the like that cannot be adjusted during use. Passive suspension systems are typically relatively simple and affordable.  
           [0006]    In passive suspension systems that utilize elements such as springs and anti-roll bars to reduce cornering roll, there is a trade-off between reduction in roll and the smoothness of the ride. Spring and shock rates that increase the smoothness of the ride often counteract the effect of conventional anti-roll devices. Moreover, such anti-roll devices do not compensate for variations in weight distribution of the vehicle that can also significantly affect rolling characteristics.  
           [0007]    What is needed, therefore, is a vehicular suspension system that provides favorable roll and pitch characteristics.  
         DISCLOSURE OF THE INVENTION  
         [0008]    It is, therefore, an object to provide a vehicular suspension system that provides favorable roll and pitch characteristics.  
           [0009]    According to the present invention, a suspension for a vehicle having a body is provided. The suspension includes a first suspension assembly and a second suspension assembly. The first suspension assembly extends between a first surface contact assembly and the body, and the second suspension assembly extends between a second surface contact assembly and the body. The first and second suspension assemblies each have a transverse instant center. The first suspension assembly and the second suspension assembly are aligned so that a vertical centerline of each surface contact assembly lies within a vertical plane that extends therebetween. The transverse instant center of each suspension assembly is located within the vertical plane, below a roll center located within the vertical plane.  
           [0010]    According to a further aspect of the invention, a method for suspending a vehicle having a body is provided that includes the steps of: (1) providing a first suspension assembly that extends between a first surface contact assembly and the body, wherein the first suspension assembly includes a transverse instant center; (2) providing a second suspension assembly that extends between a second surface contact assembly and the body, wherein the second suspension assembly includes a transverse instant center; (3) aligning the first surface contact assembly and the second surface contact assembly so that a vertical centerline of each surface contact assembly lies within a vertical plane that extends therebetween; and (4) positioning the first suspension assembly and the second suspension assembly so that the transverse instant center of each suspension assembly is located within the vertical plane, vertically below a roll center located within the vertical plane.  
           [0011]    The term “vehicle” as used herein includes, but is not limited to, wheeled all-terrain vehicles, snowmobiles, hydroplanes, tracked vehicles, and vehicles that travel on rails. The vehicle may be self-propelled (e.g., a snowmobile) or may be non-propelled (e.g., a rail car). The term “surface contact assembly” as used herein refers to the assembly that contacts the ground or water and extends upward to the vehicle suspension. An automobile wheel assembly, an all-terrain vehicle wheel assembly, a snowmobile ski assembly, a hydroplane ski assembly, and a track assembly of a tracked vehicle are all examples of surface contact assemblies that can be used with the present invention.  
           [0012]    An advantage of the present invention is that it is possible to create a relatively high and stable roll center, and therefore a desirable stable vehicular suspension. The relatively high roll center can be maintained in approximately the same position during expected motion of the vehicle.  
           [0013]    These and other objects, features, and advantages of the present invention will become apparent in light of the drawings and detailed description of the present invention provided below. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    [0014]FIG. 1 is a diagrammatic front view of vehicle (e.g., a snowmobile) having the present invention suspension.  
         [0015]    [0015]FIG. 2 is a diagrammatic front view of vehicle (e.g., an all-terrain vehicle) having the present invention suspension.  
         [0016]    [0016]FIG. 3 is a diagrammatic view of a support arm.  
         [0017]    [0017]FIG. 4 is a diagram that illustrates the relationship of the support arm planes within a vertical transverse (or “widthwise”) extending plane passing through the vertical centerline of the surface contact assemblies, shown in the form of ski mount assemblies.  
         [0018]    [0018]FIG. 5 is a diagram that illustrates the relationship of the support arm planes within a vertical transverse (or “widthwise”) extending plane passing through the vertical centerline of the surface contact assemblies, shown in the form of wheel mount assemblies.  
         [0019]    [0019]FIG. 6 is a diagram showing relative plane positioning.  
         [0020]    [0020]FIG. 7 is a side view diagram of the present suspension that illustrates the relationship of the support arm planes within a longitudinally extending plane passing through the vertical centerline of the wheel.  
         [0021]    [0021]FIG. 8 is a diagrammatic top view of a vehicle illustrating the orientation of the body mount lines of the present suspension relative to a longitudinally extending line.  
         [0022]    [0022]FIG. 9 is a diagrammatic view of the present suspension illustrating the position of the spindle joints and mounts relative to the surface contact assembly.  
         [0023]    [0023]FIG. 10 is a diagram that illustrates the relationship of the kingpin axis and the wheel assembly so that the positionability of the kingpin axis possible with the present suspension can be fully appreciated.  
         [0024]    [0024]FIG. 11 is a diagrammatic view of an embodiment of the present suspension includes a spring assembly.  
         [0025]    [0025]FIGS. 12-14 are diagrams illustrating Ackermann steering geometry between the front wheels of a vehicle. FIG. 12 shows wheels having Ackermann, FIG. 13 shows wheels having “neutral” Ackermann (also referred to as parallel orientation), and FIG. 14 shows wheels having reverse Ackermann.  
         [0026]    [0026]FIG. 15 is a diagrammatic side view of an embodiment of the present suspension.  
         [0027]    [0027]FIG. 16 is a diagrammatic top view of an embodiment of the present  
         [0028]    [0028]FIG. 17 is a diagrammatic view of an independent link embodiment of a support arm.  
         [0029]    [0029]FIG. 18 is a diagrammatric view of an embodiment of the support arm that includes a pair of independent links connected by a lateral member. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0030]    Referring to FIGS. 1-3, a vehicular suspension  10  is described herein that can be used on a wide variety of different vehicular applications; e.g., automobiles, trucks, all-terrain vehicles, snowmobiles, hydroplanes, tracked vehicles, rail cars, etc. The suspension  10  is used with independently suspended surface contact assemblies  12 . To simplify the description herein, unless otherwise specified the term “surface contact assembly” as used herein shall be defined as including, but not limited to, a ski mount assembly of a snowmobile and/or that of a hydroplane, a wheel mount assembly of a vehicle on wheels, a roller mount assembly for a tracked vehicle, or the like. The surface contact assembly  12  may be driven or non-driven.  
         [0031]    The present vehicular suspension  10  includes a one or more suspension assemblies  14 , each having a pair of support arms  16 , 18  extending between the body  20  of the vehicle and the surface contact assembly  12 . The terms “vehicle body” or “body of the vehicle” as used herein are defined as including the frame and chassis components attached thereto. The exact frame and chassis arrangement will vary depending on the application; e.g., snowmobile, ATV, etc. The present invention suspension  10  contemplates and is useful with all of these different types of vehicle bodies, and is not therefore limited to use with any one of the above.  
         [0032]    The elements of a surface contact assembly  12  will vary depending on the vehicular application, and in some instances the elements will also depend on the position of the surface contact assembly on the vehicle (e.g., front, rear, etc.). The surface contact assembly can be generally described as including a surface member  22  and a spindle  24 . The term “surface member” as used herein refers to a structure (e.g., a wheel or ski) which directly contacts the surface  25  over which the vehicle is traveling, or a structure (e.g., a wheel or a roller used with an endless track) that indirectly contacts the surface  25  over which the vehicle is traveling. The term “spindle” as used herein refers to a structure on which a wheel or roller is rotatably mounted, or on which a ski is pivotally mounted. The surface member  22  is mounted on the spindle  24 . The spindle  24  includes an upper spindle joint  26  and a lower spindle joint  28 . The type of each upper and lower spindle joint  26 , 28  is chosen to suit the application. Examples of acceptable types of spindle joints  26 , 28  include, but are not limited to, ball joints, compliant bushings, heim joints, etc.  
         [0033]    Referring to FIG. 3, each support arm  16 , 18  includes a spindle mount  30 , a first body mount  32 , a first member  34 , a second body mount  36 , and a second member  38 . The first member  34  extends between the spindle mount  30  and the first body mount  32 . The second member  38  extends between the spindle mount  30  and the second body mount  36 . Some embodiments further include one or more lateral members  40  extending between the first and second members  34 , 38  to increase the rigidity of the support arm  16 , 18  and/or to provide an attachment point for additional suspension members (e.g., springs, shocks, etc.). The support arm  16 , 18  is pivotally attached to the vehicle body at the first and second body mounts  32 , 36 . In some instances, one or both body mounts  32 , 36  include a pliable bushing that provides a limited amount of motion in addition to rotational motion around a pivot axis extending between the body mounts (hereinafter referred to as a “body mount line  42 ”). The spindle mount  30  and the body mounts  32 , 36  in each support arm  16 , 18  define a plane. The first and second members  34 , 38  (and the lateral member(s)  40  if present) are not necessarily disposed in the plane of the support arm  16 , 18  of which they are a part, although they can be in some applications. The exact geometry of the first and second member  32 , 36  (and lateral member(s)) will vary to accommodate the application at hand.  
         [0034]    The pair of support arms  16 , 18  extending between the body  20  of the vehicle and the surface contact assembly  12  are arranged vis-à-vis the body  20  and the surface contact assembly  12  such that one of the support arms  16  extends between the lower spindle joint  28  and a pair of upper body mounts  32 , 36  (collectively referred to in FIGS. 1 and 2 by reference numeral  35 ), and the other support arm  18  extends between the upper spindle joint  26  and a pair of lower body mounts (collectively referred to in FIGS. 1 and 2 by reference numeral  37 ). The upper body mounts  35  are disposed vertically above, but not necessarily aligned with, the lower body mounts  37  when the surface member  22  is in contact with or proximate the surface  25 . The members  34 , 38  of one of the support arms  16 , 18  are received between the members  34 , 38  of the other support arm  18 , 16 . Hence, the support arms  16 , 18  may be described as crossing one another in an “X” shaped arrangement, without normally touching one another.  
         [0035]    The support arms  16 , 18  described above represent a preferred embodiment of the present invention, but do not represent all the possible embodiments of support arms  16 , 18 . In alternative embodiments, one or both of the support arms  16 , 18  can be replaced with independent links that extend along paths similar to those of the above-described support arms  16 , 18 ; e.g., a pair of independent links, each including a spindle mount  30  on one end and a body mount  32 , 36  on the opposite end. Independent links can be used in place of one or both of the support arms  16 , 18 . The independent links may be connected to one another by a lateral member(s)  40 .  
         [0036]    [0036]FIGS. 4 and 5 each show a diagram representing a suspension  10  (see FIGS. 1 and 2) having a pair of symmetrically arranged suspension assemblies  14 , each having a surface contact assembly  12  disposed on a side of the vehicle body  20 . In the embodiment shown in FIG. 4, the surface contact assemblies  12  are shown in the form of a ski mount assembly, and in FIG. 5 the surface contact assemblies  12  are shown as a wheel or roller mount assembly. The diagrams are shown along a vertical plane  44  (see FIG. 6) that passes through the vertical centerlines  46  of both surface contact assemblies  12  and surface members  22 . FIG. 6 shows the aforesaid vertical plane  44  in a perspective view to better illustrate the position of the plane  44  relative to the surface contact assemblies  12  and surface members  22  (each depicted as a wheel). The lines  48 ,  50  formed at the intersection of each support arm plane with the vertical plane  44  are shown in FIGS. 4 and 5. Note that the support arm plane intersection lines  48 , 50  cross one another in each suspension when viewed in this plane. The intersection point of the lines is defined as the transverse instant center (IC)  52  for the front elevation view of that suspension assembly  14 . FIGS.  4  and  5  also show a pair of lines  54 , 56  that intersect at the roll center  58  of the vehicle body  20 . One line  54  passes through the center  60  of an area where the surface member  22  is in contact with the surface  25  (hereinafter referred to as the “contact patch” of the surface member), and the transverse IC  52  on one side of the vehicle body  20 . The other line  56  passes through the center  60  of the surface member contact patch and the transverse IC  52  on the opposite side of the vehicle body  20 .  
         [0037]    The vertical position of the roll center  58  relative to the center of gravity of the vehicle body  20  is significant because it affects the roll of the vehicle. The position of the roll center  58  can be adjusted by altering the relative positioning of the support arms  16 , 18  on either or both sides of the vehicle, and thereby alter the position of the longitudinal IC  52  which is defined by the planes of the support arms  16 , 18 . An advantage provided by the present suspension is that it is possible to create a relatively high and stable roll center  58 ; i.e., a relatively high roll center than can be maintained in approximately the same position during expected motion of the vehicle. It should also be noted that the roll center  58  shown in FIGS. 4 and 5 is intersected by the vertical centerline  62  of the vehicle body  20 . The roll center  58  intersects the centerline  62  because the suspension assemblies  14  on each side of the vehicle body  20  are symmetrical with one another. The roll center  58  can be moved to one side of the vehicle centerline  62  by making the suspension assemblies  14  non-symmetrical. The roll center  58  is described above at rest under normal loading conditions. The roll center  58  can move to either side of the vehicle centerline  62  under certain loading or body movement conditions.  
         [0038]    Referring to FIG. 7, the orientation of the support arm planes within a suspension assembly  14  also has important implications relative to other suspension parameters such as anti-dive, anti-squat, and anti-lift; i.e., suspension characteristics in the fore and aft direction of the vehicle (also referred to as “pitch”). FIG. 7 diagrammatically shows a side-view of a surface contact assembly  12 . The view is shown along a longitudinally extending vertical plane that passes through the centerline of the surface member  22 . The surface member  22  outline is shown in phantom in FIG. 7 (in the form of a wheel or roller) to locate the other elements of the figure. The lines  64 , 66  formed by the intersection of the support arm planes with the plane passing through the centerline of the surface member  22  on that side of the vehicle body  20 , illustrate an embodiment where the support arm planes are not parallel to a horizontal plane  68 . The lines  64 , 66  can be extended to a convergence point  70  that is the instant center of the suspension assembly in the side view (i.e., the “longitudinal IC”). Stated differently, the support arms  16 , 18  can be mounted in a position such that the lines  64 , 66  of the support arm planes are skewed toward one another to create the aforesaid convergence point  70 . A line extending between the longitudinal IC  70  and the center of the surface member contact patch  60  forms an angle β with a horizontally extending plane  68  containing the surface member contact patch  60 . The tangent of the angle β is directly related to the anti-dive of the vehicle surface contact assembly  12  being considered. Increasing or decreasing the magnitude of the angle β enables the adjustment of the anti-dive to be suited to the application. A line extending between the longitudinal IC  70  and the center of the surface member  22  forms an angle α with a horizontally extending plane  68  passing through the center of the surface member  22 . The tangent of the angle a is directly related to the anti-lift and anti-squat of the vehicle surface contact assembly  12  being considered. Increasing or decreasing the magnitude of the angle a enables the adjustment of the anti-lift and anti-squat to be suited to the application. The present suspension  10  facilitates the positioning of the convergence point  70  vertically and horizontally and thereby enables the use of a variety of advantageous β angle&#39;s for various vehicular applications. The convergence point  70  can also be positionally described in terms of a side view swing arm (SVSA) height and length. The SVSA height represents either: 1) the difference in vertical distance between the horizontal plane  68  and the longitudinal IC  70 ; or 2) the difference in vertical distance between a horizontal plane passing through the centerline of the surface member  22  and the longitudinal IC  70 . Which SVSA height is appropriate depends on the position of the surface contact assembly  12 , whether it is driven, etc. The methodology to determine which is used is known and will therefore not be discussed further herein. The SVSA length is the distance between the vertical centerline  72  of the surface contact assembly  12  and the longitudinal IC  70 .  
         [0039]    Referring to FIG. 8, each support arm  16 , 18  can be skewed from the longitudinally extending vertical axis  62  by an angle δ. The angle δ is defined as the angle between a line  42  extending between the body mounts of a support arm (described above as body mount line  42 ) and the longitudinally extending vertical axis  62  of the vehicle. FIG. 8 diagrammatically shows the suspension assemblies of a wheeled vehicle (e.g., an ATV, a tracked vehicle, etc.) in a horizontal plane to illustrate the angle δ extending between the body mount lines  42  of each suspension assembly  14  and a longitudinally extending line  74  parallel to the axis  62 . The suspension assemblies  14  shown in FIG. 8 are all equally skewed by the angle δ (i.e., δ 1 =δ 2 =δ 3 =δ 4 ). The exact amount of skew can vary to suit the application at hand and need not be similar between suspension assemblies  14 ; e.g., front and rear wheel suspension assemblies  14  can have different skew angles (e.g., δ 1 =δ 2 , δ 2 ≠δ 4 , δ 3 =δ 4 ), or suspension assemblies  14  on opposite sides can have different skew angles (e.g., δ 1 ≠δ 2 , δ 1 =δ 3 , δ 2 =δ 4 ). The ability of the present suspension  10  to have suspension assemblies  14  skewed from the longitudinally extending vertical axis  62  of the vehicle makes it advantageously adaptable to a variety of vehicular applications.  
         [0040]    Referring to FIG. 9, the crossed orientation of the support arms  16 , 18  within the present suspension assemblies  14  facilitates positioning the spindle joints  26 , 28  and spindle mounts  30  relative to the surface member  22 . A line  76  extending between the spindle joints  26 , 28  is referred to herein as the kingpin axis  76 . As can be seen in FIG. 9, the kingpin axis  76  passing through the spindle joints  26 , 28  and spindle mounts  30  forms an angle λ relative to the vertical centerline  46  of the surface member  22 . In some instances, the kingpin axis  76  may be parallel to the vertical centerline  46  of the surface member  22  (zero degree angle −0°). In other instances, the angle between the kingpin axis  76  and the vertical centerline  46  is greater than zero and the kingpin axis  76  can therefore be described as extending toward (or away from) the vertical centerline  46 . The angle of the kingpin axis  76  relative to the vertical centerline  46  and the position where the kingpin axis  76  intersects the vertical centerline  46  are both significant because of the effects they have relative to the scrub radius of the surface member  22  and the length of the spindle  24 . The crossed orientation of the support arms  16 , 18  within the present suspension enables the spindle mounts  30  and spindle joints  26 ,  28  to be positioned relatively close to the vertical centerline  46  of the surface member.  
         [0041]    Referring to FIG. 10, the crossed orientation of the support arms  16 , 18  within the present suspension assemblies  14  also provides favorable positionability of the spindle joints  26 , 28  and spindle mounts  30  vis-a-vis the caster angle  78 , the kingpin offset  79 , and the trail  80  of the kingpin axis  76 . The caster angle  78  refers to the angle between the kingpin axis  76  relative to the vertical centerline  72  of the surface member  22  in the side view of the surface contact assembly  12 . The kingpin offset  79  is the distance between the vertical side view centerline  72  and the point where kingpin axis  76  intersects a horizontally extending line passing through the center of the surface member  22 . The trail  80  refers to the distance between the vertical centerline  72  of the surface member  22  and the point of intersection between the kingpin axis  76  and the horizontal plane  68  containing the surface member contact patch  60 .  
         [0042]    Referring to FIG. 11, the present suspension assemblies  14  utilize a spring assembly  82  that extends between, and is pivotally attached to, one of the support arms  16 , 18  (or other portion of the surface contact assembly  12 , e.g., the spindle  24 ) and the vehicle body  20 . FIG. 11 shows the spring assembly  82  attached to the support arm  16  that is pivotally attached to the lower spindle joint  28 , but in alternative embodiments the spring assembly  82  could be attached to the other support arm  18  (or other portion of the spring contact assembly  12 ). A variety of spring assemblies can be utilized with the present invention and consequently the present invention is not limited to any particular spring assembly  82 . A torsion bar (not shown) may be used with, or in place of, a spring assembly  82 . The spring assembly  82  is mounted so that the assembly is skewed at an angle φ from vertical when the surface member  22  is a normal ride height.  
         [0043]    Referring to FIGS. 12-14, it is known to use Ackermann to account for the difference in turning radius between the surface member  22  (shown diagrammatically) disposed along the inner radius track in a turn and the surface member  22  disposed along the outer radius track. It is also known that turning can produce lift on the vehicle body  20 . The amount of Ackermann created by the front suspension when the steering is turned can be used to counteract the lift produced on the vehicle body  20  during the turn. For example, increasing the Ackermann can produce anti-lift. The support arms  16 , 18  of the present suspension assemblies  14  facilitate the creation of Ackermann because of their positionability relative to the vehicle body  20 .  
         [0044]    Referring to FIGS. 15-18, an embodiment of the present suspension  10  is shown extending between the body  20  of the vehicle and a surface contact assembly in the form of an axle assembly  84 . The axle assembly  84  includes a plurality of flanges  86  attached to an axle housing  88 . In terms of the above description, the flanges  86  attached to the axle housing  88  function as a part of a spindle assembly, since a wheel  22  (i.e., “surface member”) is rotatably mounted on each end of the axle assembly  84 . The plurality of flanges  86  include one or more upper flange joints  90  and one or more lower flange joints  92 .  
         [0045]    The suspension includes one or more first support arms  16  and one or more second support arms  18 , extending between the body  20  of the vehicle and the axle assembly  84 . The first support arm is shown as a single independent link, and the second support arm is shown as a pair of independent links connected by a lateral member  100 . In the embodiment shown in FIGS. 15 and 16, the support arms  16 , 18  are arranged vis-à-vis the body  20  and the axle assembly  84  such that the first support arm  16  extends between a lower flange joint  92  and an upper body mount  94 . The second support arms  18  extend between a pair of upper flange joints  90  and a pair of lower body mounts  96 . The upper body mounts  94  are disposed vertically above, but not necessarily aligned with, the lower body mounts  96  when the surface member  22  is in contact with or proximate the surface  25 . The first support arm  16  is received between the second support arms  18 . Hence, the support arms  16 , 18  may be described as crossing one another in an “X” shaped arrangement when viewed horizontally (e.g., the side view shown in FIG. 15), without normally touching one another. FIG. 15 also diagrammatically shows a spring assembly  98  extending between a second support arm  18  and the body  20 . A spring assembly  98  may extend between each second support arm  18  and the body  20 , or between the body  20  and the lateral member  100  attached to the second support arms  18 . In alternative embodiments, a spring assembly  98  can be disposed between the first support arm  16  and the body  20  in combination with or in place of the spring assembly(ies)  98  extending between the second support arm(s) and the body  20 . In a further alternative embodiment, one or more spring assemblies may extend between the axle assembly  84  (e.g., flanges  86 ) and the body  20 . As indicated above, the flanges  86 , attached to the axle housing  88 , function as a spindle in this embodiment.  
         [0046]    Although this invention has been shown and described with respect to the detailed embodiments thereof, it will be understood by those skilled in the art that various changes in form and detail thereof may be made without departing from the spirit and scope of the invention. For example, FIGS. 1 and 2 show a diagrammatic front view of a vehicle having a pair of the present suspension assemblies  14 . The support arms  16 , 18  of those suspension assemblies  14  are symmetrical and do not cross the centerline  62  of the vehicle. In alternative embodiments, the support arms  16 , 18  of one or both suspension assemblies may cross the centerline  62 , and potentially cross each other. Extending the support arms  16 , 18  can provide favorable camber characteristics for a surface contact assembly  12 . In addition, the Detailed Description above describes the use of a single suspension assembly  14  with a surface contact assembly  12 . In alternative embodiments, a plurality of suspension assemblies  14  can be utilized with a surface contact assembly  12 . In addition, some suspension assemblies  14  may also include non-crossing links to add additional stiffness, strength, and positional control.