Patent Publication Number: US-2018038350-A1

Title: Adapters for wind turbine refurbishment

Description:
FIELD OF THE INVENTION 
     The present disclosure relates generally to wind turbines, and more particularly to the use of adapters to facilitate refurbishment of wind turbines. 
     BACKGROUND OF THE INVENTION 
     Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a tower, generator, gearbox, machine head, and a rotor including one or more rotor blades. The rotor blades capture kinetic energy from wind using known foil principles and transmit the kinetic energy through rotational energy to turn a shaft coupling the rotor blades to a gearbox, or if a gearbox is not used, directly to the generator. The generator then converts the mechanical energy to electrical energy that may be deployed to a utility grid. 
     Wind turbine technology is rapidly progressing. Accordingly, as the technology utilized in existing wind turbines becomes outdated and/or existing wind turbines approach their designed lives, it may be desirable to refurbish such existing wind turbines. Such refurbishment can provide various advantages, including the implementation of newer, more efficient technology and components on existing base components. For example, in many cases, the machine head and, optionally, the yaw drive, can be replaced. A new, more technologically advanced machine head and optional yaw drive can be provided on to an existing tower. Accordingly, additional life and more efficient power generation can be provided with reduced capital expenses. 
     One concern, however, is that new components such as machine heads, etc. may not be manufactured to mate with existing components such as towers. For example, the new components may have mounting apparatus that is larger, smaller, or otherwise different from the mating mounting apparatus of the existing components. 
     Accordingly, improved wind turbines, and in particular improved apparatus and methods for refurbishing wind turbines, are desired in the art. Specifically, adapters which facilitate the connection of new components such as machine heads to existing components such as towers would be advantageous. 
     BRIEF DESCRIPTION OF THE INVENTION 
     Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention. 
     In accordance with one embodiment, a method for refurbishing a wind turbine is provided. The method includes removing an existing machine head from the wind turbine, and providing a new machine head and an adapter. The new machine head includes a base frame, and further includes a plurality of fastener holes defined in the base frame. The adapter includes an outer sidewall and defining a first plurality of fastener holes and a second plurality of fastener holes, the first plurality of fastener holes disposed in a first hole pattern, the second plurality of fastener holes disposed in a second hole pattern different from the first hole pattern. The method further includes connecting the new machine head and the adapter such that the adapter is connected to and between a yaw bearing and one of the base frame or a top flange of a tower of the wind turbine. 
     In accordance with another embodiment, a wind turbine is provided. The wind turbine includes a tower, the tower including a top flange and a plurality of fastener holes defined in the top flange. The wind turbine further includes a machine head, the machine head including a base frame, the machine head further including a plurality of fastener holes defined in the base frame. The wind turbine further includes a rotor coupled to the machine head, the rotor including a hub and a plurality of rotor blades. The wind turbine further includes a yaw bearing, the yaw bearing including an inner race and an outer race, the yaw bearing further including a plurality of fastener holes defined in the inner race and a plurality of fastener holes defined in the outer race. The wind turbine further includes an adapter, the adapter including an outer sidewall and defining a first plurality of fastener holes and a second plurality of fastener holes, the first plurality of fastener holes disposed in a first hole pattern, the second plurality of fastener holes disposed in a second hole pattern different from the first hole pattern. The adapter is connected to and between the yaw bearing and one of the base frame or the top flange. 
     In accordance with another embodiment, a wind turbine is provided. The wind turbine includes a tower, the tower including a top flange and a plurality of fastener holes defined in the top flange. The wind turbine further includes a machine head, the machine head including a base frame, the machine head further including a plurality of fastener holes defined in the base frame. The wind turbine further includes a rotor coupled to the machine head, the rotor including a hub and a plurality of rotor blades. The wind turbine further includes a yaw bearing, the yaw bearing including an inner race and an outer race, the yaw bearing further including a plurality of fastener holes defined in the inner race and a plurality of fastener holes defined in the outer race. The wind turbine further includes an adapter, the adapter including an outer sidewall and defining a first plurality of fastener holes and a second plurality of fastener holes, the first plurality of fastener holes disposed in a first hole pattern, the second plurality of fastener holes disposed in a second hole pattern different from the first hole pattern. The adapter is connected to and between the inner race and the top flange. A hole pattern of the plurality of fastener holes defined in the inner race matches the first hole pattern and a hole pattern of the plurality of fastener holes defined in the top flange matches the second hole pattern. 
     These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which: 
         FIG. 1  is a perspective view of a wind turbine according to embodiments of the present disclosure; 
         FIG. 2  illustrates a perspective, internal view of a machine head of a wind turbine according to embodiments of the present disclosure; 
         FIG. 3  illustrates a cross-sectional view of components of an existing wind turbine in accordance with embodiments of the present disclosure; 
         FIG. 4  illustrates a cross-sectional view of components of a refurbished wind turbine, including an adaptor connected between a tower and a yaw bearing in accordance with embodiments of the present disclosure; 
         FIG. 5  illustrates a cross-sectional view of components of a refurbished wind turbine, including an adaptor connected between a tower and a yaw bearing in accordance with embodiments of the present disclosure; 
         FIG. 6  illustrates a cross-sectional view of components of a refurbished wind turbine, including an adaptor connected between a tower and a yaw bearing in accordance with embodiments of the present disclosure; 
         FIG. 7  illustrates a cross-sectional view of components of a refurbished wind turbine, including an adaptor connected between a tower and a yaw bearing in accordance with embodiments of the present disclosure; 
         FIG. 8  illustrates a cross-sectional view of components of a refurbished wind turbine, including an adaptor connected between a machine head and a yaw bearing in accordance with embodiments of the present disclosure; 
         FIG. 9  illustrates a cross-sectional view of components of a refurbished wind turbine, including an adaptor connected between a machine head and a yaw bearing in accordance with embodiments of the present disclosure; 
         FIG. 10  illustrates a top schematic view of a first and second hole pattern in accordance with embodiments of the present disclosure; and 
         FIG. 11  illustrates a top schematic view of a first and second hole pattern in accordance with embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents. 
       FIG. 1  illustrates perspective view of one embodiment of a wind turbine  10 . As shown, the wind turbine  10  includes a tower  12  extending from a support surface  14 , a machine head  16  mounted on the tower  12 , and a rotor  18  coupled to the machine head  16 . The rotor  18  includes a rotatable hub  20  and at least one rotor blade  22  coupled to and extending outwardly from the hub  20 . For example, in the illustrated embodiment, the rotor  18  includes three rotor blades  22 . However, in an alternative embodiment, the rotor  18  may include more or less than three rotor blades  22 . Each rotor blade  22  may be spaced about the hub  20  to facilitate rotating the rotor  18  to enable kinetic energy to be transferred from the wind into usable mechanical energy, and subsequently, electrical energy. For instance, the hub  20  may be rotatably coupled to an electric generator  24  ( FIG. 2 ) positioned within the machine head  16  to permit electrical energy to be produced. 
     As shown, the wind turbine  10  may also include a turbine control system or a turbine controller  26  centralized within the machine head  16 . However, it should be appreciated that the turbine controller  26  may be disposed at any location on or in the wind turbine  10 , at any location on the support surface  14  or generally at any other location. The turbine controller  26  may generally be configured to control the various operating modes (e.g., start-up or shut-down sequences) and/or components of the wind turbine  10 . For example, the controller  26  may be configured to control the blade pitch or pitch angle of each of the rotor blades  22  (i.e., an angle that determines a perspective of the rotor blades  22  with respect to the direction  28  of the wind) to control the loading on the rotor blades  22  by adjusting an angular position of at least one rotor blade  22  relative to the wind. For instance, the turbine controller  26  may control the pitch angle of the rotor blades  22 , either individually or simultaneously, by transmitting suitable control signals/commands to a pitch controller of the wind turbine  10 , which may be configured to control the operation of a plurality of pitch drives or pitch adjustment mechanisms  32  ( FIG. 2 ) of the wind turbine, or by directly controlling the operation of the plurality of pitch drives or pitch adjustment mechanisms. Specifically, the rotor blades  22  may be rotatably mounted to the hub  20  by one or more pitch bearing(s) (not illustrated) such that the pitch angle may be adjusted by rotating the rotor blades  22  along their pitch axes  34  using the pitch adjustment mechanisms  32 . Further, as the direction  28  of the wind changes, the turbine controller  26  may be configured to control a yaw direction of the machine head  16  about a yaw axis  36  to position the rotor blades  22  with respect to the direction  28  of the wind, thereby controlling the loads acting on the wind turbine  10 . For example, the turbine controller  26  may be configured to transmit control signals/commands to a yaw drive mechanism  38  ( FIG. 2 ) of the wind turbine  10 , via a yaw controller or direct transmission, such that the machine head  16  may be rotated about the yaw axis  36 . 
     It should be appreciated that the turbine controller  26  and/or the pitch controller  30  may generally comprise a computer or any other suitable processing unit. Thus, in several embodiments, the turbine controller  26  and/or pitch and yaw controllers may include one or more processor(s) and associated memory device(s) configured to perform a variety of computer-implemented functions. As used herein, the term “processor” refers not only to integrated circuits referred to in the art as being included in a computer, but also refers to a controller, a microcontroller, a microcomputer, a programmable logic controller (PLC), an application specific integrated circuit, and other programmable circuits. Additionally, the memory device(s) of the turbine controller  26  and/or pitch and yaw controllers may generally comprise memory element(s) including, but are not limited to, computer readable medium (e.g., random access memory (RAM)), computer readable non-volatile medium (e.g., a flash memory), a floppy disk, a compact disc-read only memory (CD-ROM), a magneto-optical disk (MOD), a digital versatile disc (DVD) and/or other suitable memory elements. Such memory device(s) may generally be configured to store suitable computer-readable instructions that, when implemented by the processor(s), configure the turbine controller  26  and/or pitch and yaw controllers to perform various computer-implemented functions. In addition, the turbine controller  26  and/or pitch and yaw controllers may also include various input/output channels for receiving inputs from sensors and/or other measurement devices and for sending control signals to various components of the wind turbine  10 . 
     Referring now to  FIG. 2 , a simplified, internal view of one embodiment of the machine head  16  of the wind turbine  10  is illustrated. As shown, a generator  24  may be disposed within the machine head  16 . In general, the generator  24  may be coupled to the rotor  18  of the wind turbine  10  for generating electrical power from the rotational energy generated by the rotor  18 . For example, the rotor  18  may include a main shaft  40  coupled to the hub  20  for rotation therewith. The generator  24  may then be coupled to the main shaft  40  such that rotation of the main shaft  40  drives the generator  24 . For instance, in the illustrated embodiment, the generator  24  includes a generator shaft  42  rotatably coupled to the main shaft  40  through a gearbox  44 . However, in other embodiments, it should be appreciated that the generator shaft  42  may be rotatably coupled directly to the main shaft  40 . Alternatively, the generator  24  may be directly rotatably coupled to the main shaft  40  (often referred to as a “direct-drive wind turbine”). 
     It should be appreciated that the main shaft  40  may generally be supported within the machine head  16  by a base frame or bedplate  46  positioned atop the wind turbine tower  12 . For example, the main shaft  40  may be supported by the base frame  46  via one or more pillow blocks mounted to the base frame  46 . 
     Additionally, as indicated above, the turbine controller  26  may also be located within the machine head  16  of the wind turbine  10 . For example, as shown in the illustrated embodiment, the turbine controller  26  is disposed within a control cabinet  52  mounted to a portion of the machine head  16 . However, in other embodiments, the turbine controller  26  may be disposed at any other suitable location on and/or within the wind turbine  10  or at any suitable location remote to the wind turbine  10 . Moreover, as described above, the turbine controller  26  may also be communicatively coupled to various components of the wind turbine  10  for generally controlling the wind turbine and/or such components. For example, the turbine controller  26  may be communicatively coupled to the yaw drive mechanism(s)  38  of the wind turbine  10  for controlling and/or altering the yaw direction of the machine head  16  relative to the direction  28  ( FIG. 1 ) of the wind. Similarly, the turbine controller  26  may also be communicatively coupled to each pitch adjustment mechanism  32  of the wind turbine  10  (one of which is shown) through the pitch controller  30  for controlling and/or altering the pitch angle of the rotor blades  22  relative to the direction  28  of the wind. For instance, the turbine controller  26  may be configured to transmit a control signal/command to each pitch adjustment mechanism  32  such that one or more actuators (not shown) of the pitch adjustment mechanism  32  may be utilized to rotate the blades  22  relative to the hub  20 . 
     Referring still to  FIG. 2 , as well as  FIGS. 3 through 5 , gearbox  44  may be coupled to main shaft  40 , and may be mounted to the base frame  46 . As shown, gearbox  44  may include an outer casing  60  which may surround and generally enclose the internal gearbox components, such as the various gears, etc. thereof. Further, one or more torque arms  62  may extend from the outer casing  60 . Typically, two torque arms  62  extend from the outer casing  60  on generally opposing sides of the casing  60 . A torque arm  62  may generally facilitate reaction and transmission of loads to which the shaft  40 , etc., are subjected by transmitting these loads from the gearbox  44  to, for example, the base frame  46 . 
     As illustrated, a nacelle  17  may surround and enclose the various components within the machine head  16 . In general, the base frame  46  and nacelle  17  may form the outer surface(s) of the machine head  16 . 
     Referring now to  FIG. 3 , components of an existing wind turbine  100  in accordance with embodiments of the present disclosure are provided. The existing wind turbine  100  may include a tower  110 . The tower  110  may include a top flange  112  and a plurality of fastener holes  114  defined in the top flange  112 . The top flange  112  may connect the tower  110  to other components of the wind turbine  100  that are provided on top of the tower  110 . Further, fasteners  102 , such as bolts or other suitable mechanical fastening devices, may be extended through the fastener holes  114  and fastener holes in a mating component positioned on top of the tower  110  to connect these components together. 
     Wind turbine  100  may further include a machine head  120 , which may include a base frame  122  as shown. The base frame  122  may connect the machine head  120  to other components of the wind turbine  100  that are provided below the machine head  120 . The base frame  122  may include a plurality of fastener holes  124  defined in the base frame  122 . Fasteners  102 , such as bolts or other suitable mechanical fastening devices, may be extended through the fastener holes  124  and fastener holes in a mating component positioned below the machine head  120  to connect these components together. 
     Existing wind turbine  100  may further include a yaw drive mechanism  130 , which may include a yaw drive  132  and a yaw bearing  134 . The yaw bearing  134  may include an inner race  136  and an outer race  138 , and may further include one or more bearings  135  disposed between the inner race  136  and outer race  138 . A plurality of fastener holes  137  may be defined in the inner race  136 , and a plurality of fastener holes  139  may be defined in the outer race  139 . 
     Each plurality of fastener holes  114 ,  124 ,  137 ,  139  may be provided in a particular hole pattern. The hole pattern in generally defined as a generally annular array of the plurality of fastener holes, and is defined by a maximum outer diameter (i.e. a distance between centers of the furthest apart pair of holes) and the number of holes and spacing therebetween. In the existing wind turbine  100 , certain of the hole patterns may match, such that mating fastener holes align and allow fasteners  102  to be extended therethrough. For example, as shown, the fastener hole  114  pattern and fastener hole  137  patterns may match, thus allowing fasteners  102  to extend through each mating pair of holes  114 ,  137  to connect the top flange  112  and inner race  136 . Additionally, the fastener hole  124  pattern and fastener hole  139  pattern may match, thus allowing fasteners  102  to extend through each mating pair of holes  124 ,  139  to connect the base frame  122  and outer race  138 . 
     Existing wind turbine  100  may further include a rotor and other suitable components, as illustrated for example in  FIGS. 1 and 2 . 
     Referring now to  FIGS. 4 through 11 , embodiments of refurbished wind turbines  200  and components thereof are provided. A refurbished wind turbine  200  may include a tower, which in exemplary embodiments is an existing tower  110 . In some embodiments, an upper portion of the existing tower  110  may be removed for refurbishing purposes. In these embodiments, top flange  112  as discussed herein is the top flange  112  after such removal. Alternatively, however, no such removal is required. The refurbished wind turbine  200  may further include a yaw drive mechanism. In some embodiments, existing yaw drive mechanism  130  may be utilized. In other embodiments, a new yaw drive mechanism  230  may be utilized. New yaw drive mechanism  230  may include any combination of new and/or existing components. For example, the existing yaw drive  132 , inner race  136 , outer race  138  and/or bearings  135  may be replaced with a new yaw drive  232 , inner race  236 , outer race  238  and/or bearings  235 . New inner race  236  may include a plurality of fastener holes  237 , and new outer race  238  may include a plurality of fastener holes  239 . Each plurality of fastener holes  237 ,  239  may be provided in a particular hole pattern. If a new inner race  236  is utilized, the fastener hole  237  pattern may be different from the fastener hole  137  pattern. If a new outer race  238  is utilized, the fastener hole  239  pattern may be different from the fastener hole  139  pattern. 
     Refurbished wind turbine  200  may further include a new machine head  220 , which may include a new base frame  222  and any other combination of new and/or existing components. The base frame  222  may include a plurality of fastener holes  224  defined in the base frame  222 . The plurality of fastener holes  222  may be provided in a particular hole pattern. The fastener hole  222  pattern may be different from the fastener hole  122  pattern. 
     As shown, the refurbished wind turbine  200  may further include an adapter  250 . The adapter  250  may advantageously facilitate the retrofitting of wind turbines by allowing for new machine heads  220  and/or yaw drive mechanisms  230  to be connected to existing towers  110 . 
     In exemplary embodiments, the adapter  250  is formed from steel, cast iron, or another suitable metal. Alternatively, other suitable materials such as fiberglass, etc. may be utilized. In some exemplary embodiments, the adapter  250  may be formed from the same material as the tower  110 . 
     An adapter  250  may include an outer sidewall  252  and define a first plurality of fastener holes  254  and a second plurality of fastener holes  256 . The first plurality of fastener holes  254  may be disposed in a first hole pattern  255 . The second plurality of fastener holes  256  may be disposed in a second hole pattern  257 . The second hole pattern  257  is different from the first hole pattern  255 . 
     For example, the maximum outer diameters of the first and second hole patterns  255 ,  257  may be different. In some embodiments, as illustrated in  FIGS. 5, 7, 8 and 10 , a maximum outer diameter D 1  of the first hole pattern  255  is greater than a maximum outer diameter D 2  of the second hole pattern  257 . In other embodiments, as illustrated in  FIGS. 6, 9 and 11 , a maximum outer diameter D 1  of the first hole pattern  255  is less than a maximum outer diameter D 2  of the second hole pattern  257 . In other embodiments, the maximum outer diameters D 1 , D 2  may be the same, but other characteristics of the hole patterns, such as the spacing and/or number of holes, is different. Irrespective of the diameters, D 1 , D 2 , the number of fastener holes  254  may be different from the number of fastener holes  256 . For example, in some embodiments, the number of fastener holes  254  in the first hole pattern  255  is greater than the number of fastener holes  256  in the second hole pattern  257 . In other embodiments, the number of fastener holes  254  in the first hole pattern  255  is less than the number of fastener holes  256  in the second hole pattern  257 . 
     The adapter  250  is connected to and between the yaw bearing  134 / 234  and one of the base frame  222  or the top flange  112 . For example, as illustrated in  FIGS. 4 through 7 , in some embodiments the adapter  250  is connected to and between the yaw bearing  234  and the top flange  112 . For example, the adapter  250  may be connected, such as by fasteners  102 , to the top flange  112  and the inner race  236 . In exemplary embodiments as shown, the hole pattern of the plurality of fastener holes  237  defined in the inner race  236  matches the first hole pattern  255  and the hole pattern of the plurality of fastener holes  114  defined in the top flange  112  matches the second hole pattern  257 . Fasteners  102  may thus extend through each pair of fastener holes  114 ,  256  to connect the adapter  250  and tower  110 , and through each pair of fastener holes  237 .  254  to connect the adapter  250  and the yaw bearing  234  together. 
     It should be noted that, in these embodiments, the hole pattern of the plurality of fastener holes  239  defined in the outer race  238  may match the hole pattern of the plurality of fastener holes  224  defined in the base frame  222 . Fasteners  102  may thus extend through each pair of fastener holes  239 ,  224  to connect the yaw bearing  234  and machine head  220  together. 
     Accordingly, the adapter  250  in these embodiments advantageously facilitates the use of a new yaw bearing  234  and machine head  220 . 
     As illustrated in  FIGS. 8 and 9 , in some embodiments the adapter  250  is connected to and between the yaw bearing  134 / 234  and the base frame  222 . For example, the adapter  250  may be connected, such as by fasteners  102 , to the base frame  222  and the outer race  138 / 238 . In exemplary embodiments as shown, the hole pattern of the plurality of fastener holes  224  defined in the base frame  222  matches the first hole pattern  255  and the hole pattern of the plurality of fastener holes  139 / 239  defined in the outer race  138 / 238  matches the second hole pattern  257 . Fasteners  102  may thus extend through each pair of fastener holes  224 ,  254  to connect the adapter  250  and machine head  220 , and through each pair of fastener holes  139 / 239 ,  256  to connect the adapter  250  and the yaw bearing  134 / 234  together. 
     It should be noted that, in these embodiments, the hole pattern of the plurality of fastener holes  137 / 237  defined in the inner race  136 / 236  may match the hole pattern of the plurality of fastener holes  114  defined in the top flange  112 . Fasteners  102  may thus extend through each pair of fastener holes  114 ,  137 / 237  to connect the yaw bearing  134 / 234  and tower  110  together. 
     Accordingly, the adapter  250  in these embodiments advantageously facilitates the use of a new machine head  220  and, optionally, yaw bearing  234 . 
     In some embodiments, as illustrated in  FIGS. 4-6 and 8-9 , the adapter  250  may include an upper flange  262  and a lower flange  264 . The lower flange  264 , as shown, may be spaced from the upper flange  262 . In these embodiments, the first plurality of fastener holes  254  may be defined in the upper flange  262  and the second plurality of fastener holes  256  may be defined in the lower flange  264 . 
     The adapter  250  in these embodiments may, in some embodiments, taper between the upper flange  262  and lower flange  264 . For example, the taper may occur outwardly in a direction from the lower flange  264  to the upper flange  262 , as illustrated in  FIGS. 5 and 8 , or outwardly in a direction from the upper flange  262  to the lower flange  264 , as illustrated in  FIGS. 6 and 9 . Alternatively, the adapter  250  may have a generally constant outer diameter, as illustrated in  FIG. 4 . 
     Alternatively, in some embodiments, as illustrated in  FIG. 7 , the adapter  250  may be a disc  266 . In these embodiments, the first plurality of fastener holes  254  and the second plurality of fastener holes  256  may be defined in the disc  266 . 
     The present disclosure is further directed to methods for refurbishing wind turbines. For example, an existing wind turbine  100  may be provided. The method may include removing an existing machine head  120  from the wind turbine  100 . In some embodiments, the method may further include removing an existing yaw drive mechanism  130  (or yaw bearing  134  thereof) from the wind turbine  100 . Any suitable apparatus, including cranes and suitable tools for removing fasteners  102 , may be utilized to remove the existing machine head  220 . Any suitable apparatus, including cranes and suitable tools for removing fasteners  102 , may be utilized to remove the existing machine head  220  and existing yaw drive mechanism  230  (or yaw bearing  234  thereof). 
     In some embodiments, the method may include, for example, removing an upper portion of the existing tower  110 . Alternatively, no such removal is required. 
     The method may further include, for example, the step of providing a new machine head  220  and an adapter  250 , as discussed herein. In some embodiments, the method may further include, for example, the step of providing a new yaw drive mechanism  230  (or yaw bearing  234  thereof). 
     The method may further include, for example, the step of connecting the new machine head  220  and the adapter  250  such that the adapter  250  is connected to and between the yaw bearing  134 / 234  and one of the base frame  222  or the top flange  112 , as discussed herein. In some embodiments, the method may further include, for example, the step of connecting the new yaw bearing  234 . Such connections may be facilitated by matching fastener holes and patterns thereof, as discussed herein, and the extension of fasteners  102  through matched pairs of fastener holes to connect the various components together. 
     This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.