Abstract:
A motorcycle fork rake extension kit provides an increased fork rake without welding and maintains a favorable trail. The extension kit includes an upper adapter block fixedly attached to an upper end of a steering head of a motorcycle frame and a lower adapter block fixedly attached to a lower end of the steering head of the motorcycle frame. Triple trees are rotatably attached to triple tree ends of the adapter blocks through steering head bearings. The triple tree ends of the adapter blocks are spaced away from the frame, the lower adapter block having a greater spacing to increase fork rake. The lower triple tree may further space the fork tubes forward to further increase fork rake. In a preferred embodiment, approximately 45 degrees of rake is provided with favorable trail.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to custom motorcycles and in particular to apparatus for adjusting the rake and trail of motorcycle forks. 
         [0002]    Custom motorcycle riders and builders often extend the fork angle (or rake) to obtain a desired look or a desired motorcycle feel. Various methods may be employed to extend the fork angle, ranging from permanent modifications to the motorcycle frame by modifying the angle of the steering head, to an adjustable bolt-on kit. 
         [0003]    Most rake extension kits retain the original axis of rotation of the forks and angularly offset the forks with respect to the steering head of the frame. Such kits are disclosed in U.S. Pat. No. 5,967,538 for “ADJUSTABLE MOTORCYCLE TRIPLE TREE” and U.S. Pat. No. 4,565,384 for “MOTORCYCLE FORK TREE.” While these kits allow adjustment of the fork rake, they also undesirably alter the trail (see  FIG. 3A .) Such alteration of the trail often results in a less desirable and potentially unsafe motorcycle feel and/or handling. 
         [0004]    Another rake adjustment kit is described in U.S. Pat. No. 3,866,946 for “MOTORCYCLE STEERING HEAD ANGLE ADJUSTMENT.” The kit disclosed in the &#39;946 patent includes eccentrics in the steering head to adjust the fork rake, and as a result is severely limited in the amount of adjustment. 
       BRIEF SUMMARY OF THE INVENTION 
       [0005]    The present invention addresses the above and other needs by providing a motorcycle fork rake extension kit which provides an increased fork rake without welding and maintains a favorable trail. The extension kit includes an upper adapter block fixedly attached to an upper end of a steering head of a motorcycle frame and a lower adapter block fixedly attached to a lower end of the steering head of the motorcycle frame. Triple trees are rotatably attached to triple tree ends of the adapter blocks through steering head bearings. The triple tree ends of the adapter blocks are spaced away from the frame, the lower adapter block having a greater spacing to increase fork rake. The lower triple tree may further space the fork tubes forward to further increase fork rake. In a preferred embodiment, approximately 45 degrees of rake is provided with favorable trail. 
         [0006]    In accordance with one aspect of the invention, there is provided a motorcycle fork rake extender including an upper adapter block and a lower adapter block. The upper adapter block has an upper frame end and an upper triple clamp end, which upper frame end is spaced apart from the upper triple clamp end by an upper adapter spacing. The lower adapter block has a lower frame end and a lower triple clamp end, which lower frame end is spaced apart from the lower triple clamp end by a lower adapter spacing, wherein the lower adapter spacing is greater than the upper adapter spacing. The upper frame end of the upper adapter block is fixedly attached to the upper end of a frame steering head and the lower frame end of the lower adapter block is fixedly attached to the lower end of a frame steering head. The upper fork end of the upper adapter block includes a seat for an upper fork bearing and the lower fork end of the lower adapter block includes a seat for a lower fork bearing. An upper triple clamp is rotatably connected to the upper adapter block through the fork bearings and a lower triple clamp rotatably connected to the lower adapter block through the fork bearings. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         [0007]    The above and other aspects, features and advantages of the present invention will be more apparent from the following more particular description thereof, presented in conjunction with the following drawings wherein: 
           [0008]      FIG. 1  is a prior art motorcycle with a stock rake. 
           [0009]      FIG. 2  is a motorcycle with a rake extension kit according to the present invention installed. 
           [0010]      FIG. 3  shows a more detailed view of motorcycle forks with the fork rake extended using the present invention. 
           [0011]      FIG. 3A  is a diagram of trial and rake. 
           [0012]      FIG. 4  is a cross-sectional view of the fork rake extender attached to a steering head. 
           [0013]      FIG. 5  is an exploded view of elements of the fork rake extender kit. 
           [0014]      FIG. 6  is a perspective view of a lower adapter block according to the present invention of the fork rake extender kit. 
           [0015]      FIG. 6A  is a side view of the lower adapter block. 
           [0016]      FIG. 6B  is a top view of the lower adapter block. 
           [0017]      FIG. 6C  is a rear view of the lower adapter block. 
           [0018]      FIG. 7  is a cross-sectional view of the lower adapter block taken along line  7 - 7  of  FIG. 6C . 
           [0019]      FIG. 8  is a perspective view of an upper adapter block according to the present invention of the fork rake extender kit. 
           [0020]      FIG. 8A  is a side view of the upper adapter block. 
           [0021]      FIG. 8B  is a top view of the upper adapter block. 
           [0022]      FIG. 8C  is a rear view of the upper adapter block. 
           [0023]      FIG. 9  is a cross-sectional view of the upper adapter block taken along line  9 - 9  of  FIG. 8C . 
           [0024]      FIG. 10  is a top perspective view of a lower triple tree according to the present invention of the fork rake extender kit. 
           [0025]      FIG. 10A  is a front view of the lower triple tree. 
           [0026]      FIG. 10B  is a top view of the lower triple tree. 
           [0027]      FIG. 10C  is a bottom view of the lower triple tree. 
           [0028]      FIG. 10D  is a side view of the lower triple tree. 
           [0029]      FIG. 11  is a cross-sectional view of the lower triple tree taken along line  11 - 11  of  FIG. 1A . 
           [0030]      FIG. 12  is a bottom perspective view of an upper triple tree according to the present invention of the fork rake extender kit. 
           [0031]      FIG. 12A  is a rear view of the upper triple tree. 
           [0032]      FIG. 12B  is a top view of the upper triple tree. 
           [0033]      FIG. 12C  is a bottom view of the upper triple tree. 
           [0034]      FIG. 12D  is a side view of the upper triple tree. 
           [0035]      FIG. 13  is a cross-sectional view of the upper triple tree taken along line  13 - 13  of  FIG. 12A . 
       
    
    
       [0036]    Corresponding reference characters indicate corresponding components throughout the several views of the drawings. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0037]    The following description is of the best mode presently contemplated for carrying out the invention. This description is not to be taken in a limiting sense, but is made merely for the purpose of describing one or more preferred embodiments of the invention. The scope of the invention should be determined with reference to the claims. 
         [0038]    A prior art motorcycle  10  with a stock (or original) fork rake is shown in  FIG. 1 . The prior art motorcycle  10  includes forks  12  mounted to a steering head  16  by original triple trees  14  and  15 . Custom motorcycle riders often desire to increase the fork  12  rake to obtain a more custom appearance. Generally, significantly increasing the fork rake requires significant modifications to the motorcycle frame to alter the steering head angle, at significant expense and time. While small increases in rake may be achieved by using “raked triple trees” which increase rake without modification to the original steering axis, such raked triple trees adversely affect trail and is therefore limited to small rake increases due to these affects on trail. 
         [0039]    A motorcycle  10   a  with a rake extension kit according to the present invention installed is shown in  FIG. 2 . The fork rake extension kit includes an upper adapter block  22  and a lower adapter block  23  attached to the unmodified steering head  16 . An upper triple tree  18  and a lower triple tree  19  connect to the adapter blocks  22  and  23 , and the forks  12  attach to the triple trees  18  and  19 . Fork extensions  12   a  are provided to maintain the original ground height of the motorcycle  10   a.    
         [0040]    A more detailed view of the motorcycle forks  12  with the fork rake extended using the present invention is shown in  FIG. 3 . The lower adapter block  23  pushes the lower triple tree  19  forward, and the lower triple tree  19  pushes the forks  12  forward, both contributing to increased fork rake while maintaining a desired trail. 
         [0041]    A diagram of trail and rake is shown in  FIG. 3A . The combination of trail and rake is an important factor in motorcycle handling. The present invention provides some rake increase in the adapter blocks  22  and  23 , and some rake increase in the triple trees  18  and  19 . The result is a preferred trail T 1 . If the triple trees  18  and  19  did not provide some of the rake increase, a much larger and less desirable trail T 2  would result, and conversely, if all of the rake increase is obtained by the triple trees, a much smaller and less desirable trail would result. 
         [0042]    A cross-sectional view of the fork rake extender attached to the steering head  16  is shown in  FIG. 4  and an exploded view of elements of the fork rake extender kit are shown in  FIG. 5 . A rear spacer shaft  28  resides in the unmodified steering head  16 . The spacer shaft  28  includes shaft alignment features  28   a  and  28   b  at the top and bottom of the spacer shaft  28  respectively. Preferred alignment features  28   a  and  28   b  comprise a cylindrical center coaxial with the spacer shaft  28 , and opposed rectangular blocks extending radially from the cylindrical center. The upper adapter block  22  resides on the top of the steering head  16 , and the lower adapter block resides on the bottom of the steering head  16 . Each adapter block  22  and  23  includes a cylindrical portion  43  configured to fit into bearing seats in the steering head  16 . The cylindrical portions  43  further include block alignment features which are preferably rectangular notches configured to engage the shaft alignment features  28   a  and  28   b . The upper and lower adapter blocks  22  and  23  are held to the steering head by at least one adapter block fastener, and preferably by a main assembly bolt  40  inserted though the lower adapter block  23 , through the spacer  28 , and threaded into the upper adapter block  22 . Tightening the bolt  40  secures the upper and lower adapter blocks  22  and  23  to the steering head  16  and preferably vertically squeezes the adapter blocks  22  and  23  against steering head  16 . 
         [0043]    Continuing with  FIGS. 4 and 5 , upper and lower bearings  36  and  38  reside in the upper and lower adapter blocks  22  and  23  respectively. A steering shaft  26  is inserted upward through the lower triple tree  19 , the bearing  38 , the lower adapter block  23 , a front spacer shaft  24 , the upper bearing  36 , and the upper adapter block  22 . A lock nut  34  is threaded onto the upper end of the steering shaft  26 , and a double lock nut  32  is threaded onto the upper end of the steering shaft  26  and against the nut  34 . The upper triple tree  18  is then placed over the upper end of the steering shaft  26 , and a triple tree retainer nut  30  is threaded onto the steering shaft  26  over the upper triple tree  18 . Set screws  42  extend through the lower adapter block  23  to engage surfaces of the steering head  16  or motorcycle frame to prevent rotation of the lower adapter block  23 . 
         [0044]    The lower adapter block  23  has a lower steering head end  23   a  and a lower triple tree end  23   b  (see  FIG. 6B ) spaced apart by a lower adapter spacing and the upper adapter block  22  has corresponding upper steering head end and upper triple tree end spaced apart by an upper adapter spacing. The lower adapter spacing is preferably greater than the upper adapter spacing resulting in an increase in the fork rake of angle A 1  between a bolt centerline  41  and steering shaft centerline  27 . Further, the forks  12  have a fork centerline  13  offset from the steering shaft centerline  27  by a second angle A 2 . A total increase in fork rake of A 1 +A 2  results. 
         [0045]    A perspective view of the top and side of the lower adapter block  23  is shown in  FIG. 6 , a side view of the lower adapter block  23  is shown in  FIG. 6A , a top view of the lower adapter block  23  is shown in  FIG. 6B , and a rear view of the lower adapter block is shown in  FIG. 6C . A cross-sectional view of the lower adapter  23  taken along line  7 - 7  of  FIG. 6C  is shown in  FIG. 7 . The lower adapter block  23  is approximately oval with the cylindrical portion  43  for cooperation with the steering head  16  bearing seats and the spacer  28  at one end, and a stepped mouth  48  for cooperation with the lower triple tree  19  and the spacer  24  at the opposite end. The cylindrical portion  43  includes a bolt passage  52  for the main assembly bolt  40  (see  FIG. 4 ), a bolt shoulder  54  for cooperation with the bolt  40 , and rectangular notches  44  for cooperation with the spacer  28  (see  FIGS. 4 and 5 ). The stepped mouth  48  provides a passage for the steering shaft  26  and a seat  50  for the lower steering bearing  38  (see  FIGS. 4 and 5 ). The set screws  42  are positioned to tighten against features of the steering head  16 , for example the steering stop pads, or features on the motorcycle frame, and the positions of the set screws  42  may be varied for different motorcycles or motorcycle frames. The screws  42  may be used during installation for adjustment of the lower adapter block  23 , or for subsequent adjustment. The screws  42  may also be tightened to aid in preventing the lower adapter block  23  from rotating during use. 
         [0046]    A perspective view of the bottom of the upper adapter block  22  is shown in  FIG. 8 , a side view of the side view of the upper adapter block  22  is shown in  FIG. 8A , a top view of the upper adapter block  22  is shown in  FIG. 8B , and a rear view of the upper adapter block  22  is shown in  FIG. 8C . A cross-sectional view of the upper adapter block  22  taken along line  9 - 9  of  FIG. 8C  is shown in  FIG. 9 . The upper adapter block  22  is approximately oval with the cylindrical portion  43  for cooperation with the upper bearing seat of the steering head  16  and the spacer  28  at an upper steering head end  22   a , and a stepped mouth  48  for cooperation with the lower triple tree  19  and the spacer  24  at the opposite end. The cylindrical portion  43  includes a bolt passage  52  for the main assembly bolt  40  (see  FIG. 4 ), and notches  44  for cooperation with the spacer  28  (see  FIGS. 4 and 5 ). The stepped mouth  48  provides a passage for the steering shaft  26  and a seat  50  for the lower steering bearing  38  (see  FIGS. 4 and 5 ). 
         [0047]    A top perspective view of a lower triple tree  19  according to the present invention is shown in  FIG. 10 , a front view of the lower triple tree  19  is shown in  FIG. 10A , a top view of the lower triple tree  19  is shown in  FIG. 10B , a rear view of the lower triple tree  19  is shown in  FIG. 10C , and a side view of the lower triple tree  19  is shown in  FIG. 10D . A cross-sectional view of the lower triple tree  19  taken along line  11 - 11  of  FIG. 10A  is shown in  FIG. 11 . The lower triple tree  19  includes two lower fork passages  16  which include gaps  60   a  and may be tightened to clamp fork tubes of the forks  12  into the lower triple tree  19 . The lower triple tree  19  further includes a lower steering shaft passage  62  for the steering shaft  26  (see  FIGS. 4 and 5 ). The separate of the fork passages  60  from the steering passage  62  is a first length L 1 . 
         [0048]    A bottom perspective view of the upper triple tree  18  according to the present invention is shown in  FIG. 12 , a rear view of the upper triple tree  18  is shown in  FIG. 12A , a top view of the upper triple tree  18  is shown in  FIG. 12B , a bottom view of the upper triple tree  18  is shown in  FIG. 12C , and a side view of the upper triple tree  18  is shown in  FIG. 12D . A cross-sectional view of the upper triple tree  18  taken along line  13 - 13  of  FIG. 12A  is shown in  FIG. 13 . The upper triple tree  18  includes two upper fork passages  70 , and upper steering shaft passage  72 . The separate of the upper fork passages  70  from the upper steering passage  62  is a second length L 2 . The length L 1  (see  FIG. 10B ) is larger than the length L 2 , thereby increasing the fork rake. 
         [0049]    While the invention herein disclosed has been described by means of specific embodiments and applications thereof, numerous modifications and variations could be made thereto by those skilled in the art without departing from the scope of the invention set forth in the claims.