Abstract:
A brake assembly for use on vehicles includes a rotor having connection tabs and a hub having bobbins, integrally formed or separate, with the rotor connection tabs being positioned between the hub bobbins and clamped together with a top plate. An ABS tone ring is fastened to the hub and is circumscribed by the rotor. Alternatively, an ABS tone ring can be formed as part of the top plate. A spring clip can be used with the top plate to accommodate thermal expansion of the rotor and eliminate rotor rattling. Torque is transferred from the brake rotor to the hub in a common plane to prevent twisting in the fastener connection.

Description:
[0001]    This application claims priority under 35 U.S.C. §119 from U.S. Provisional application No. 60/722,096 filed Sep. 30, 2005. The contents of this application are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention relates to brake assemblies, especially vehicular brakes including brake rotors attached to wheel hubs. This invention also relates to brake assemblies that include anti-lock braking systems (ABS). 
         [0004]    2. Description of Related Art 
         [0005]    One type of common prior art brake design for vehicles is a two piece hat rotor and hub in which a hat rotor that carries the braking surface is detachably connected to a wheel hub. Another common type of brake design is an integrated one-piece rotor and hub assembly. 
         [0006]    Integrated one-piece rotor and hub assemblies have the advantage that no fasteners are required between the rotor and the hub. As a result, the integrated assemblies do not face problems associated with fasteners such as wear and fatigue near fastener openings and potential misalignment due to imperfect machining and tolerance stack ups. A significant drawback, however, is that the assembly is constrained at the hub, which causes thermal distortion of the rotor. Such thermal distortion can damage the rotor, and when the rotor is damaged or worn, the entire integrated assembly must be replaced. This is expensive and time consuming. 
         [0007]    Complete replacement is avoided by using a two piece hat rotor and hub assembly, which facilitates rotor replacement. When a rotor becomes worn or cracked, the rotor disc can be detached from the hub for a lower cost and easier replacement than with the integrated design. Hat rotors are typically one piece metal castings having a rotor portion integrally cast with a hat portion. The hat portion of the hat rotor is a large flange that fits over a mounting surface of the hub. The hat portion includes wheel stud apertures through which wheel studs can pass. Hat rotors can also be made as two pieces with a flat rotor disc fastened to the hat portion. 
         [0008]    Hat rotors, however, also have some drawbacks. In particular, hat rotors and hubs are typically individual metal castings. Subsequent to casting, the hat rotor and the hub must both be individually machined. The machined surfaces of the rotor hat portion, the rotor braking surfaces, and the mounting surface of the hub must all be in the proper plane to minimize rotor run-out, which is the rotational misalignment of the rotor. Specifically, rotor run-out is the measurement of the extent to which the rotor wobbles, or deviates outside the intended plane of rotation, as the rotor rotates with the hub about the wheel shaft. Rotor run-out causes excessive and uneven wear in the rotor braking surfaces and in brake pads which contact the rotor braking surfaces. Rotor run-out also increases thermal distortion of the brake rotor. The thermal distortion results in thermal judder, noise, and vibrations during braking, as well as causing irregular braking pulsations. This can be a significant problem as it is very difficult to achieve perfect machining. 
         [0009]    Another deficiency with hat rotor hub assemblies results from the manner in which a hat rotor and a wheel are mounted together on the hub. The hat rotor is installed over a mounting surface of the hub, and then the hat rotor is loosely mounted on the hub until a wheel is subsequently mounted on the hub. As wheel lug nuts are tightened to the wheel studs, the hat rotor is sandwiched between the wheel and the hub, thus securing the hat rotor to the hub. However, if the wheel lug nuts are not evenly tightened, the uneven forces acting on the hub may result in the distortion of the hub. Additionally, if the wheel rim has been improperly manufactured, the wheel rim might impose a distortion on the hub as the lug nuts are tightened. Any distortion on the hub will be directly transferred to the rotor, as the portion of the hub that is potentially distorted is also the mounting surface for the rotor in all hat rotor designs. This induces stress concentrations in the rotor during use. 
         [0010]    A further concern of both integrated rotor hubs and hat rotor hubs is that the rotor in both of these designs is fixed with respect to the hub. During braking, the rotor in such an assembly is subjected to high frictional forces that generate heat in the rotor causing thermal expansion/distortion, temperature variation across the face of the rotor, and heat transfer to the adjacent components including the hub and the bearings. Thermal expansion of the rotor is very limited, in the radial direction, because of the integral connection between the rotor and the hub. This creates thermal coning in the rotor surface and a large thermal gradient, which will induce high thermal stress leading to thermal cracking. The high thermal gradient generated during braking and the effects of the thermal expansion and distortion can cause vibration and thermal judder across the brake surfaces, resulting in rough or irregular braking pulsations. The high thermal stress and thermal distortion also reduce the life and performance of the rotor and increase maintenance costs. 
         [0011]    One way the thermal stresses have been addressed is to provide a “floating” rotor in which the fastener connection between the rotor and the hat or hub is provided with a small clearance or float that allows thermal expansion. Two-piece rotors also allow greater flexibility with respect to use with different hubs as the same rotor disc can be used with different hat portions. This reduces the cost since generic rotor discs may be used and only the hat portion requires specialized casting, tooling and machining steps. However, stresses induced by fastener assemblies in this design are also a consideration in two-piece hat rotors. 
         [0012]    Typical rotor discs in two-piece hat designs have an attachment flange that is perforated to accept a fastener. The hat portion is placed on one side of the attachment flange and a fastener connects the hat portion to the side of the attachment flange. During braking, a frictional force is applied to the rotor surface, which creates torque that is transferred to the attachment flange, to the fastener, through the hat portion and to the hub. Because the hat portion is attached to one side of the attachment flange, which is in a plane axially displaced from the friction braking surface, a moment arm is created at this connection joint. When the torque is transferred through a moment arm, bending stresses are formed in the connection. This creates twisting in the areas adjacent the fastener, which can create fatigue leading to cracking and breaking. The perforated flange tends to become fatigued because the material of the rotor, cast iron for example, weakens at high temperatures leading to fatigue fractures. This also creates problems with run-out, as discussed above, along with premature fracture of components in the connection. 
         [0013]    Torque transfer also tends to be non-uniform through the perforated flange, especially in a floating design, as the machining tolerance at each aperture causes certain connections to receive more torque than other connections. This creates high stresses at individual apertures and can cause the attachment flange to crack or to have portions break off. 
         [0014]    The two-piece hat rotor assemblies discussed above also have drawbacks associated with the hat portion, which typically has slots that match with the perforations in the rotor attachment flange. Some floating type two piece hat rotor assemblies use a spacer, sometimes called a bobbin, to provide the clearance that accommodates thermal expansion. The bobbin fits in the slots of the hat piece or in slots of the rotor flange, and when torque is applied to the hat through the rotor, the bobbin twists in the slot. This twisting causes the edges of the bobbin, which are typically square to match the slot, to gouge the sides of the slots, thus damaging the slotted piece. This is especially true when the hat piece is manufactured from a material having a lower hardness, such as aluminum, which is popular in high performance and racing applications, or when the rotor is formed of cast iron. 
         [0015]    In summary, prior art brake rotors have suffered from problems associated with wear and material fatigue due to stresses induced during the braking process, particularly bending stresses caused during torque transfer and non-uniform transfer of torque caused by machining tolerances. It would be desirable to reduce the stresses experienced by the rotor and, in the case of a two piece rotor, the hat piece to increase performance and durability. 
         [0016]    This problem has been addressed in U.S. Pat. No. 7,077,247, which is commonly assigned with this application and incorporated by reference herein. In this patent, the fastener assembly includes a plurality of bobbins and fasteners. The fasteners extend through the hat portion and each bobbin to clamp the attachment flange between the hat portion and the bobbin. If desired, a spring can be disposed between the attachment flange and bobbin. The fastening assembly transfers torque from the braking surface to the hat portion in a common plane to prevent twisting. A crush zone can also be provided in association with the fastener assembly to promote uniform torque transfer distribution from the attachment flange to the hat portion. 
         [0017]    While the above described system is effective, many braking assemblies now use anti-lock braking systems (ABS) in which an exciter or tone ring is associated with the rotor and hub so that the rotation of the wheel assembly can be detected by a sensor. There is a need to accommodate ABS technology in brake rotor assemblies while addressing the problems inherent in these assemblies relating to thermal expansion and bending stresses. 
       SUMMARY OF THE INVENTION 
       [0018]    An aspect of embodiments of the invention provides a two-piece hat rotor with a tone ring that connects the components in a way that allows in plane torque transfer. 
         [0019]    Another aspect of embodiments of the invention provides a fastener assembly to connect a rotor and hub including an ABS system that securely clamps the rotor to the wheel hub. 
         [0020]    The invention is directed to a brake assembly comprising a rotor having a braking surface and an attachment flange, wherein the attachment flange includes a plurality of spaced tabs, and a hub having an axial body, a mounting surface extending from the axial body for attachment to a vehicle component, and a rotor support extending from the axial body. The rotor support includes a radial surface that abuts the tabs of the rotor. A tone ring including a plurality of exciter formations is mounted for rotation with the hub. A clamping mechanism attaches the spaced tabs of the rotor to the radial surface of the rotor support. 
         [0021]    The invention is also directed to a brake assembly comprising a rotor having a braking surface and an attachment flange, wherein the attachment flange includes a plurality of spaced tabs, and a rotatable hub having an axial body, a mounting surface extending from the axial body for attachment to a vehicle component, and a rotor support extending from the axial body. The rotor support includes a radial surface that abuts the tabs of the rotor and a plurality of spaced bobbins. A plate is fastened to the bobbins to clamp each tab of the rotor between a pair of bobbins so as to cause torque generated during braking to transfer from the rotor tabs to the bobbins and the hub in a common plane. An anti-lock braking system is coupled to the brake assembly including a tone ring. 
         [0022]    These and other aspects of the invention will become apparent in view of the detailed description and drawings herein. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]    The invention is described in conjunction with the following drawings in which like reference numerals designate like elements and wherein: 
           [0024]      FIG. 1  is a front perspective view of a brake rotor assembly in accordance with an embodiment of the invention; 
           [0025]      FIG. 2  is a front perspective cross sectional view taken along line I-I of  FIG. 1 ; 
           [0026]      FIG. 3  is a front view of the hub of the brake rotor assembly of  FIG. 1 ; 
           [0027]      FIG. 4  is a side view in cross section taken along line II-II of  FIG. 3 ; 
           [0028]      FIG. 5  is a reduced front perspective view of the hub of  FIG. 3 ; 
           [0029]      FIG. 6  is an enlarged detail of section III of  FIG. 3 ; 
           [0030]      FIG. 7  is a front view of the rotor in accordance with the assembly of  FIG. 1 ; 
           [0031]      FIG. 8  is a front view of the tone ring in accordance with the assembly of  FIG. 1 ; 
           [0032]      FIG. 9  is an enlarged side view of the clip for use with the assembly of  FIG. 1 ; 
           [0033]      FIG. 10  is an enlarged view of another side of the clip of  FIG. 9 ; 
           [0034]      FIG. 11  is an enlarged top view of the clip of  FIG. 9 ; 
           [0035]      FIG. 12  is a front view of the assembly of  FIG. 1  partially assembled with the rotor and tone ring positioned on the hub; 
           [0036]      FIG. 13  is an enlarged detail of section IV of  FIG. 12 ; 
           [0037]      FIG. 14  is an enlarged top view of the top plate for use with the assembly of  FIG. 1 ; 
           [0038]      FIG. 15  is a front view of the fully assembled brake rotor assembly of  FIG. 1 ; 
           [0039]      FIG. 16  is a side view in cross section taken along line V-V of  FIG. 15 ; 
           [0040]      FIG. 17  is an enlarged detail of section VI of  FIG. 16 ; 
           [0041]      FIG. 18  is an enlarged detail of section VII of  FIG. 16 ; 
           [0042]      FIG. 19  is front view of the hub in accordance with second embodiment of the invention, shown assembled in  FIG. 26 ; 
           [0043]      FIG. 20  is a side view in cross section taken along line VIII-VIII of the hub of  FIG. 19 ; 
           [0044]      FIG. 21  is a front perspective view of the hub of  FIG. 19 ; 
           [0045]      FIG. 22  is a front view of the second embodiment partially assembled with the hub of  FIG. 19  and the rotor and bobbins positioned thereon; 
           [0046]      FIG. 23  is an enlarged front view of a bobbin for use with the second embodiment; 
           [0047]      FIG. 24  is a side perspective view of the bobbin of  FIG. 23 ; 
           [0048]      FIG. 25  is a front view of the top plate with integral tone ring of the second embodiment; 
           [0049]      FIG. 26  is a front view of the brake rotor assembly of the second embodiment; 
           [0050]      FIG. 27  is a side cross sectional view of the assembly taken along line IX-IX of  FIG. 26 ; 
           [0051]      FIG. 28  is an enlarged detail of section X of  FIG. 27 ; and 
           [0052]      FIG. 29  is an enlarged detail of section XI of  FIG. 27 . 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0053]    The brake assembly disclosed herein is preferred for use on vehicles, including automobiles, racing vehicles, trucks, heavy duty trucks, motorcycles and the like. The vehicles suitable for use with this invention can include those vehicles having a gross vehicle weight of less than about 5,000 pounds, a gross vehicle weight of about 5,000 pounds to 12,000 pounds, and a gross vehicle weight of more than about 12,000 pounds, for example 30,000 pounds. However, the inventive concepts discussed herein can be used in any type of application that uses rotary brakes, including automotive, other types of motorized vehicles, or railcars. 
         [0054]      FIG. 1  shows a brake rotor assembly  10  in accordance with a first embodiment of the invention. The assembly  10  includes a hub  12  that supports a rotor  14 . The hub  12 , as used herein, can be a wheel hub, a rotating flange, a bearing housing of a hub assembly or the hat portion of an integrated rotor. The term hub in this application is intended to cover all known possible mountings for a rotor. 
         [0055]    The hub  12 , seen in detail in  FIGS. 3 ,  4 , and  5 , includes an axial body in the form of a central cylinder  16  with a radial mounting flange  18  on one end having a plurality of mounting apertures  20  therein and a rotor support flange  22  on the other end. The rotor support flange  22  extends outwardly from cylinder  16  and has an outward end that is radially spaced from the central cylinder  16 . A series of axially extending threaded bores  21  are located on the central cylinder  16  in the space between the cylinder  16  and the flange  22 . The outward end of the rotor support flange  22  is an annular ring that extends around the central cylinder  16  and presents a radial face for mounting the rotor  14  thereon. The radial face has a plurality of spaced bobbin tabs  24  that form axially raised portions with depressed portions  25  therebetween. Each bobbin tab  24  is formed in a generally trapezoidal shaped with angled side walls. A threaded aperture  26  is formed in each bobbin tab  24 . As seen in detail in  FIG. 6 , preferably a generally u-shaped clip  28  may be attached to the side of a number of bobbin tabs  24 . Of course, a single clip  28  or a smaller segment could also be used. 
         [0056]    The hub  12  can be made of any conventional material, such as cast iron or ductile iron. Typically, hubs are not corrosion protected. The clip  28 , therefore, is preferably made of a corrosion resistant material, such as stainless steel. The clip  28  forms a shim between the hub  12  and the rotor  14  when assembled to offer corrosion protection between the elements. 
         [0057]    The rotor  14  is seen in detail in  FIG. 7 . The rotor  14  is formed as a disc having opposed braking surfaces  32  separated by vanes  34  (seen in  FIGS. 1 and 2 ) to form a ventilated disc. Of course, a disc formed as a flat plate with a single surface or opposed braking surfaces can also be used, as would be readily recognized by one of ordinary skill in the braking art. The braking surface  32  preferably carries a friction material. On the inner periphery of the annular disc, a series of spaced connection tabs  36  are formed. Each tab  36  extends radially inwardly and is preferably formed as a solid tab, with no aperture needed for a fastener, as would be required for a conventional or two-piece floating rotor. However, apertures could be present without affecting the operation of the invention. Each tab  36  presents a pair of side surfaces  38  that extend radially or at an angle, which will engage with the hub  12 , as discussed below. If desired, the side surface  38  can have a surface treatment, such as threads, serrations, or dimples, to yield in response to stresses induced by manufacturing irregularities. The rotor disc  14  is preferably made of cast iron. For example, a suitable material would be Class 35 cast iron, which has a tensile strength of about 35 ksi and a yield strength of about 28 ksi. 
         [0058]    The brake rotor assembly  10  of this invention is designed for use with an anti-lock braking system (ABS) in which an exciter or tone ring  40  is provided to operate with a sensor, not shown, to sense rotation of the assembly. As ABS assemblies are well known, no further description of the sensor and its operation is necessary. This invention can operate with any known conventional ABS assembly. The tone ring  40  in accordance with this invention is shown in detail in  FIG. 8 . The ring  40  is formed with radially spaced teeth  42 , or ridges and valleys, that extend around the circumference of the ring on a radially face thereof. The tone ring  40  can be made as a single ring and can be made of powder metal, steel, or cast steel, for example. Any known type of exciting mechanism may be used in place of the teeth, including for example slots. A series of spaced connection shoulder  44  are provided around the inner periphery of the ring. Each shoulder  44  has a through hole  46 . 
         [0059]    A spring clip  50  preferably used with this invention is shown in  FIGS. 9-11 . The spring clip  50  is formed of a body  52  of bent metal forming a U-shape with side walls  54  and a base  56 . Extending from each side of the base  56  are wings  58  that form a leaf spring. A shelf  59 , or some protrusion such as dimples, extends slightly inwardly from each side wall  54 . The spring clip  50  can be made of stainless steel, powder or stamped, for example. The assembly and operation of the clip  50  is described below. 
         [0060]      FIG. 12  shows the components partially assembled with the rotor  14  positioned on the hub  12  and the tone ring  40  mounted to the hub  12 . As seen in detail in  FIG. 13 , the tone ring  40  is secured to the hub  12  by a fastener  60  extending through the hole  46  in the shoulder  44  and into the threaded bore  21 . The rotor  14  is positioned such that each connection tab  36  is mounted in the depressed area  25  between two bobbin tabs  24 . The clips  28  are positioned between the side walls  38  of the connection tabs  36  and the side walls of the bobbin tabs  24  to form a non-corrodible connection. As can be appreciated, the shear forces generated during braking are transferred from the rotor  14  to the hub  12  in a common plane through the side walls of tabs  24 ,  36 , which eliminates bending stresses. 
         [0061]    To secure the rotor  14  in place on the hub  12 , a top plate  64  is used to clamp the connection tab  36  to the rotor support flange  22 . The top plate  64  is formed as a partial arcuate segment. A series of top plates  64  are used to cover the entire inner circumference of the rotor  14 . Of course, a solid annular ring or semi-circular segments could also used rather than segments. As seen in  FIG. 14 , the top plate  64  is formed as a flat plate with spaced indented sections  66 . The top plate  64  is preferably formed of carbon steel, but can be any known material suitable for brake applications. A plurality of fastener openings  68  are provided to align with the openings  26  in the tabs  24 . 
         [0062]    The complete assembly is shown in  FIGS. 1 ,  2 , and  15 . The top plates  64  clamp over the connection tabs  36  and are secured to the bobbin tabs  24  by fasteners  70 , seen in detail in  FIGS. 16 and 18 . The bobbin tabs  24  are slightly larger or higher than the connection tabs  36 . As seen in detail in  FIGS. 16 and 17 , the spring clips  50  are fastened to the indented sections  66  of the top plate  64  to bias the top plate with respect to the tabs  36  in the space formed between the top plate  64  and the connection tabs  36  due to the slightly larger height of the bobbin tabs  24 . The spring clip  50  provides a tight rattle-free connection and accommodates thermal expansion. A spring clip  50  is also shown schematically positioned on the tab  36  in  FIG. 12 . 
         [0063]    This assembly provides a secure connection in which forces are transferred in a common plane, while accommodating an ABS component. In operation, the rotor disc  14  rotates with the wheels of the vehicle. Upon application of a braking force by pressing brake pads against the braking surface  32 , the friction force times the distance from the center of the piston to the center of the disc creates torque. The torque is transferred from the rotor  14  to the hub  12  to the wheel to effect braking. Specifically, torque is transferred through the connection tabs  36  to the bobbin tabs  24 . The bobbin tabs  24  transfer the torque to the support flange  22 , which then transfers it to the wheels through the mounting flange  18 . The interaction between the side edges of the tabs  36  and the bobbin tabs  24  will only allow in-plane torque transfer, which reduces the twisting moment on the rotor flange and the ABS ring, which is conventionally attached to the disc rotor. In this invention, the reduction in twisting of the ABS ring prevents a failed ABS signal caused by induced runout to the sensor. 
         [0064]    A significant advantage that this configuration has over prior art configurations is that the connection of the hub  12  to the rotor  14  is effected in the same plane as the rotor disc. By clamping the tabs  36  of the rotor  14  with the fastening assembly, the friction force experienced by the braking surface  32  is transferred as torque directly in the same plane to the hub  12 . As the connection created by the fastener assembly is in axial alignment with the rotor disc, no moment arm is created. This transfers the torque without bending, which can create problems with run-out and premature fracture. 
         [0065]    This invention also offers the advantage of a lower rotor failure rate. As the rotor  14  in accordance with this invention has tabs for attachment, rather than perforations as in conventional rotors, failure of the attachment flange is greatly reduced. In conventional rotors, the attachment flange has a plurality of apertures that receive fasteners. As the rotor is heated due to the braking force, the strength of the flange drops since cast iron has a low fatigue strength. In the perforated flange, which is typically made of cast iron, the connection between the fastener and the perforated flange induces stress concentrations on the edge of the perforations. As a result, the flange tends to fail. In this invention, use of the perforations for making the connection is eliminated. The rotor is driven through the radial side edges of the tabs, which are stronger and accordingly resist failure. 
         [0066]    This invention also accommodates thermal expansion of the rotor in each direction, while eliminating rattling. The spring clip can be compressed a certain amount, which allows for thermal expansion, and clearance is provided at the outer edges of the connection tabs that face radially inwardly, which also accommodates thermal expansion. Further, since the spring clip  50  is compressed against the tab upon assembly, the tab will not rattle due to the clearances described above. This configuration also has the advantage of only compression loading the spring clip  50 . Since the clip  50  is not restrained in the circumferential direction or the radial direction of the rotor, it does not experience torsional and bending loading, which could cause a spring to fail. 
         [0067]    A second embodiment is shown in  FIGS. 19-29 , with  FIG. 26  showing the entire assembly  100 . In this embodiment, the tone ring and the top plate are formed as one structure to reduce the number of components needed and to simplify assembly. Referring to  FIGS. 19-21 , the difference between the hub  12  and the modified hub  102  is the rotor mounting flange. Hub  102  has a central cylinder  104  with a radial mounting flange  106  on one end having a plurality of mounting apertures  108  therein and a rotor support flange  110  on the other end. The rotor support flange  110  is spaced from the central cylinder  104 . The rotor support flange  110  is an annular ring that extends around the central cylinder  104  with a series of spaced threaded apertures  112  and presents a radial face for mounting the rotor  14  thereon. An inner raised lip  114  is provided on the inner periphery of the flange  110 . The same rotor  14  shown in  FIG. 7  is used with this embodiment. 
         [0068]    As seen in  FIG. 22 , the rotor  14  is positioned on the hub with the tabs  36  overlapping the rotor support flange  110 . The tabs  36  are positioned with the assistance of the raised lip  114 . A series of bobbins  120 , seen in detail in  FIGS. 23 and 24 , are provided between the tabs  36  positioned over the apertures  112 . Each bobbin  120  is trapezoidal in shape with side walls  122  and a through hole  124 , similar in shape and function to the bobbin tabs  24  of the first embodiment. The bobbins  120  are preferably made of a strong corrosion resistant material, such as stainless steel. 
         [0069]    A top plate  128 , seen in detail in  FIG. 25 , is formed as an integral ring with the inner periphery  130  defining a tone ring having a series of radial teeth  132 , or peaks and valleys, that may be detected by an ABS sensor, as is known. The top plate  128  has spaced indents  134  formed on the outer periphery and matching slots  136  formed in the central portion. A series of spaced apertures  138  are also formed therethrough. Of course, the top plate  128  could also be formed as series of arcuate or semi-circular segments. 
         [0070]    When completely assembled, the top plate  128  is secured over the tabs  36  and bobbins  120  with a fastener  140 , as seen in  FIGS. 26 and 29 . The spring clip  50 , as in the first embodiment, is clipped to the top plate  128  adjacent to the tabs  36 , as seen in  FIGS. 22 and 28 . As the bobbins  120  are slightly larger than the tabs  36 , the spring clips  50  are accommodated in the space created above the tabs  36 . This is seen in the detail of  FIG. 28 . The side walls  54  of the clips  50  snap over the indents  134  and slots  136  via the protrusions  59 . 
         [0071]    This embodiment operates in the same manner as the first embodiment in that forces are transferred in the same plane through the connection tabs  36  of the rotor  14  and the bobbin side walls  122  and fastener  140 . The spacing also allows for thermal expansion as in the first embodiment. 
         [0072]    Various applications are suitable for this invention. The rotor assembly can be used on automobiles, both road vehicles and racing cars. It is also applicable to motorcycles and off road vehicles, such as all terrain vehicles and earth moving equipment. In short, the invention can be applied to any motorized vehicle. It is further contemplated that this invention can be used in a railway environment on railcars. 
         [0073]    The invention is not limited to those embodiments described herein and may encompass various changes and modifications. It will be understood that the various modifications shown herein can be used in any combination. It is also possible to eliminate various components of the assembly and still have an effective connection. For example, the springs or clips may be omitted. Further, different materials may be used to obtain similar results.