Patent Publication Number: US-9897014-B2

Title: Variable rate push/pull twist throttle

Description:
The following is a non-provisional patent application which claims priority to provisional application 61/105,732 filed Oct. 15, 2008 to the same inventors. 
    
    
     TECHNICAL FIELD 
     The present invention relates generally to devices for adjusting fuel flow to engine carburetors and more particularly to hand throttles for motorcycle engines. 
     BACKGROUND ART 
     Motorcycles and other small vehicles typically use a hand throttle to regulate the speed and acceleration of the vehicle, as opposed to using a gas pedal. The hand throttle is generally used in a rotary manner, so that the rider twists the hand throttle to increase the speed from minimum (idle) to maximum. The hand throttle is linked to a carburetor or fuel injected throttle body, and this linkage allows the twisting of the hand throttle to control the operation of the carburetor or throttle body by controlling the amount of fuel and air that flows through the carburetor or throttle body. 
       FIG. 2  illustrates elements of a carburetor  2 , as mounted on an engine  1 . The carburetor  2  is a device that mixes air and fuel for an internal combustion engine. The majority of older motorcycles are carbureted and new motorcycles are fuel injected. The carburetor and fuel injection system works on Bernoulli&#39;s principle, which is that moving air has lower pressure than still air, and that the faster the movement of the air, the lower the pressure. 
     The air flow in the carburetor  2  is controlled by rotational movement of a bell crank  3 , which is connected to butterfly valves (not shown) in the interior of the carburetor  2  through movement of the butterfly shaft  4 . The rotation of the bell crank  3  is implemented by movement of a push cable  5  and a pull cable  6  which are attached to the bell crank  3 . Barrel wire end fittings  8  at the end of the cables  5 ,  6 , are lodged in capture notches  9  in the bell crank  3  to secure them. Thus, there is a type of pulley system created by which the throttle on the handle acts to rotate the bell crank  3  and thus open and close the internal butterfly valves through the butterfly shaft  4 . 
     Acceleration of the vehicle ranges from a minimum, where the engine idles, to maximum acceleration, and the opening of the butterfly valves in the carburetor or throttle body over this range can vary from a gradual increase over a relatively large angular twist range of the hand throttle to a very sharp increase from minimum to maximum over a relatively small twist range of the hand throttle. 
     If the carburetor or throttle body control is sensitive to angular rotation, a small rotation of the hand throttle will result in a large carburetor or throttle body adjustment. Conversely, if the carburetor or throttle body control is less sensitive, the hand throttle twist range between minimum and maximum acceleration will be larger, allowing finer control. This degree of control or sensitivity will be referred to as the “throttle rate”. A throttle which goes from minimum to maximum in a small angular range will be referred to as having a “fast rate”, and one which has a large throttle angle range will be referred to as having a “slow rate”. 
     Different rates are useful for different situations and environments. For example, a rider in the desert who is on very flat terrain with no obstacles may be primarily interested in applying maximum acceleration as quickly as possible, and therefore a more sensitive throttle with a fast rate may be preferred. Conversely, a rider in the woods who is operating in hilly terrain, or in rain or mud-slickened conditions, may want to have more precise control, and thus a less sensitive throttle with a slow rate is preferred. 
     Typically, a vehicle is configured to have a fixed throttle rate, which is not variable. Modifying the throttle rate is not an operation which is easily done. 
     Thus, there is a need for a throttle which can be easily modified to produce a variety of throttle rates to provide varying sensitivity and thus variable throttle control. 
     DISCLOSURE OF INVENTION 
     An advantage of the present invention is that it provides a throttle assembly that is easily modified to change the throttle rate. 
     Another advantage of the present invention is that it provides a throttle assembly with interchangeable throttle reels. 
     And another advantage of the present invention is that it provides a throttle assembly which includes elbows with flared portions which allow optimum routing of cables to a variety of throttle reels of differing radii. 
     A further advantage of the present invention is that it provides a throttle assembly which works with push/pull cables of a standard carburetor or throttle body to provide a variable throttle rate. 
     A yet further advantage is that it provides a throttle assembly which can be easily retrofitted to existing carburetor or throttle body with minimal modification. 
     Another advantage of the present invention is that it provides a throttle assembly with throttle reels having varying track radii, and varying capture notch angles. 
     And another advantage of the present invention is that the reels have been designed to eliminate the need to make cable adjustments when changing throttle reels having varying track radii. 
     A further advantage of the present invention is that the capture notch locations for the pull cable have been designed so that the throttle handle will not rotate on the handlebar when you change throttle reels having varying track radii. This eliminates the need to make cable adjustments when using a directional grip with a specific pattern that requires it to be kept in the same position for rider comfort and or performance. 
     A further advantage of the present invention is that the reels have been designed so that they can only be installed onto the throttle handle in one direction, thus eliminating the possibility of putting the reels on incorrectly. 
     A further advantage of the present invention is that the reels have been designed so that the inner wire is captured between the side walls of the reel to prevent the inner wire from getting caught between the side of the reel and throttle housing. 
     A further advantage of the present invention is that the capture notches on the reels have been located to prevent the need to adjust the cables when changing the reels. 
     Briefly, one preferred embodiment of the present invention is a variable rate throttle for controlling a vehicle carburetor having control cables. The variable rate throttle includes a housing surrounding a cavity, a plurality of interchangeable throttle reels, each throttle reel having a different track radius, where a particular one of the throttle reels is positioned at a time in the cavity of the housing and which engages the control cables. A throttle handle engages the interchangeable throttle reel so that rotation of the handle causes rotation of the throttle reel and thus moves the control cables of the vehicle carburetor. 
     These and other advantages of the present invention will become clear to those skilled in the art in view of the description of the best presently known mode of carrying out the invention and the industrial applicability of the preferred embodiment as described herein and as illustrated in the several figures of the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The purposes and advantages of the present invention will be apparent from the following detailed description in conjunction with the appended drawings in which: 
         FIG. 1  shows a front isometric view of a variable rate push/pull throttle of the present invention in use with a carburetor; 
         FIG. 2  shows a carburetor as used with the variable rate push/pull throttle of the present invention; 
         FIG. 3  shows a side plan view of a variable rate push/pull throttle of the present invention in use with a carburetor; 
         FIG. 4  shows a rear isometric view of a variable rate push/pull throttle of the present invention in use with a carburetor; 
         FIG. 5  shows a front isometric view of the throttle assembly of the present invention with one of the housing pieces removed; 
         FIG. 6  shows an isometric exploded view of the major components of a variable rate push/pull throttle of the present invention; 
         FIGS. 7 and 8  show isometric views of two variations of throttle reels of the present invention; and 
         FIG. 9  illustrates an isometric view of a first elbow of the present invention showing the path of a cable attached to throttle reels of varying radius. 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     The present invention is a variable rate push-pull throttle assembly, which will be referred to by the reference number  10 , and thus, for simplicity, shall be referred to as throttle assembly  10 . 
     To better understand the operation of the present invention the interaction of the throttle with the carburetor should be appreciated.  FIGS. 1, and 3-4  are a front isometric view, a side plan view and a rear isometric view, respectively, of a carburetor  2  and throttle assembly  10 , showing the interaction of these elements. Reference is also made to  FIG. 2  which shows a view of a carburetor  2  mounted on an engine  1 . 
     Referring particularly to  FIG. 2 , the carburetor  2  includes a bell crank  3  rotatably mounted on a butterfly shaft  4 . Rotation of the bell crank  3  controls the air-fuel mixture which is fed to the engine  1 . The rotation of the bell crank  3  is enabled by a push cable  5  and a pull cable  6  which travel through cable housings  7  (see  FIG. 1 ). The push cable  5  and pull cable  6  each include barrel wire end fittings  8  which are lodged in capture notches  9  in the bell crank  3 . The push cable  5  and pull cable  6  travel through the cable housings  7  to reach the throttle assembly  10  at their other ends. It is to be understood that although a push/pull cable configuration is assumed in the following discussion, that this is not to be construed as a limitation and the present invention can be used in configurations in which there is only a pull cable involved or any other variation that will be obvious to one skilled in the art. 
     The throttle assembly  10  is shown in detail in  FIGS. 5-7 , in addition to  FIGS. 1 and 3-4 . The throttle assembly  10  generally includes a throttle housing  12 , which includes a first housing portion  14  and a second housing portion  16 , which are held together by fasteners  18 , preferably socket head cap screws. The throttle housing  12  surrounds a central cavity  20  which holds one of a variety of interchangeable throttle reels  22 . A throttle handle  24  is also rotatably captured by the throttle housing  12 , as will be discussed in more detail below. 
       FIG. 6  shows an exploded view of the major components of the throttle assembly  10 . The central cavity  20  includes an elongated cavity portion  26  in each of the first housing portion  14  and second housing portions  16  which receive the first elbow  28  and second elbow  30 . Each of these first elbow  28  and second elbow  30  have a flared portion  60  at the end which will be located closest to the throttle reel  22  when the throttle assembly  10  is completed. The throttle handle  24  has a tube portion  32  and a head portion  34  having a retaining ring  36 , an engaging shaft  38  and engaging flanges  40 . 
     The throttle reels  22  are interchangeable, and any one of a number of variations of these throttle reels is available to be mounted in the central cavity  20  to produce a variety of throttle rates, as will be discussed below. Four of these interchangeable throttle reels  22  are shown as a set in  FIG. 6 , but it is to be understood that many other variations including non-constant radius profiles are possible. Two such variations are shown in detail in  FIGS. 7 and 8 . 
     The throttle reel  22  generally includes a reel body  42  having two side walls  44  which define a groove  46  having a groove floor  48 . The side portions  44  thus have a greater radial dimension than the groove floor  48 , thus making a track  50  that the push cable  5  and pull cable  6  will travel upon and to which they will be confined. This is noted on  FIGS. 7 and 8 , wherein a central axis line  100  is shown and a side wall radius R 1    101  is shown from this central axis line  100  to the outer rim of the side wall  44 .  FIG. 7  illustrates a first throttle reel  52  showing a second, smaller radius R 2    102  extending to a dashed line corresponding to the groove floor  48 , thus showing the radial distance from the central axis line  100  to the groove floor  48 .  FIG. 8  illustrates a second throttle reel  54  having a still smaller radius R 3    103  from the central axis line  100  to the groove floor  48 . In  FIGS. 7 and 8 , therefore R 1 &gt;R 2 &gt;R 3 . 
     Both the first throttle reel  52  and second throttle reel  54  include receiving notches  56  which receive the engaging flanges  40  of the throttle handle  24  (see  FIG. 6 ). The throttle reels  52 ,  54  also include capture notches  58  for barrel wire end fittings  8  for the throttle assembly  10  ends of the push cable  5  and the pull cable  6 . 
     As discussed above, in comparing  FIGS. 7 and 8 , R 2 &gt;R 3 , and it should be noted that the capture notches  58  for the first throttle reel  52  having R 2 , are closer together than the capture notches  58  of second throttle reel  54  having R 3 . This will be discussed in more detail below. 
     Returning to  FIGS. 1 and 6 , the push cable  5  and pull cable  6  have been inserted through the cable housings  7  and the first and second elbows  28 ,  30 . Barrel wire end fittings  8  are attached to both ends of the cables  5 ,  6 . The barrel wire ends  8  at the ends of the cable  5 ,  6  nearest the carburetor  2  are fitted to the capture notches  9  in the bell crank  3 , and generally remain in this position. When the throttle assembly  10  is to be assembled, an interchangeable throttle reel  22  is selected from the provided variety of interchangeable throttle reels  22  having differing track radii R N    104  (see  FIG. 6 ). The throttle handle  24  is positioned so that the engaging flanges  40  of the engaging shaft  38  enter the receiving notches  56  of the throttle reel  22 . It should be noted that the reels  22  have been designed so that they can be installed onto the throttle handle  24  in only one direction, thus eliminating the possibility of putting the reels  22  on incorrectly. The barrel wire end fittings  8  at the throttle assembly  10  ends of the push cable  5  and pull cable  6  are placed within the capture notches  58  of the throttle reel  22 . The throttle handle  24  with attached throttle reel  22  is placed within either the first or second housing portions  14 ,  16  of the throttle housing  12 . The throttle reel  22  is positioned within the central cavity  20 , and with retaining ring  36  of the throttle handle  24  is positioned within the retaining ring cavity  27 . The first elbow  28  is fitted into the elongated cavity portion  26  of the first housing portion  14  and the second elbow  30  is fitted into the elongated cavity portion  26  of the second housing portion  16 . The first housing portion  14  and second housing portion  16  are fitted together and attached with fasteners  18  to make the completed throttle housing  12 . A boot  62  is provided (see  FIG. 5 ) which overlaps a portion of the throttle housing  12  and prevents dirt and grime from entering the throttle assembly  10 . 
     The push cable  5  and the pull cable  6  travel in the track  50  created between the side walls  44 , and as the throttle reel  22  is rotated by rotating the attached throttle handle  24 , the push and pull cables  5 ,  6  push and pull at their opposite ends in the manner of a pulley to rotate the bell crank  3  of the carburetor  2 . The push cable  5  and pull cable  6  each travel a limited linear distance D  11  (see  FIG. 1 ) when twisting the throttle handle  24  from an idling position to maximum acceleration. It should be noted that the reels  22  of the present invention have been designed so that the push/pull cable wires  5 ,  6  are captured between the side walls  44  of the reel  22  to prevent the cables from getting caught between the side of the reel  22  and throttle housing  12 . This is considered to be an advantage over throttles of the prior art, which did not include this feature. 
     As discussed above, the throttle reels  22  are configured with varying track radii R N    104 . In a throttle reel  22  with a large track radius R 2    102 , such as discussed earlier with regard to  FIG. 7 , the circumference of the throttle reel track  50  is larger than the circumference of the throttle reel track  50  when the track radius R 3    103  is smaller, such as discussed with regard to  FIG. 8 , according to the formula Circumference=2πR. Thus, since the limited linear travel distance D  11  (see  FIG. 1 ) of the push and pull cables  5 ,  6  is fixed by the carburetor or throttle body, in a throttle assembly  10  having a larger track radius R 2    102  needs less angular rotation to move the push and pull cables  5 ,  6  the limited linear travel distance D  11 . Thus, for a large track radius R 2    102 , the angular throttle travel range shown as β 1   68  from minimum to maximum will be smaller than for a smaller track radius R 3    103 . This means that in a reel  52  with a large radius R 2    102 , the throttle control will be more sensitive to angular rotation. A small rotation of the throttle handle  24  will result in a large carburetor adjustment. Conversely, in a reel  54  having a small track radius R 3    103 , the angular throttle travel range shown as β 2   70  between minimum and maximum will be larger, and throttle control will be less sensitive, allowing finer control over acceleration. This variable degree of throttle control or sensitivity will be referred to as throttle rate. A throttle which goes from minimum to maximum in a small angular range will be referred to as having a “fast rate”, and one which has a large throttle angle range will be referred to as having a “slow rate”. 
     The capture notches  58  in throttle reel  22  are located to compensate for the difference in circumference of the throttle reel track  50 . Thus the capture notches  58  on a large track radius R 2    102 , are placed farther apart than the capture notches  58  on a smaller track radius R 3    103 . This is apparent in comparing  FIGS. 7 and 8  where the separation angle of capture notches  58  for throttle reel  52  having large track radius R 2    102  is shown in  FIG. 7  as capture notch range angle α 1   64  and the capture notch range angle α 2   66  is shown in  FIG. 8  for smaller track radius R 3    103 . This novel feature eliminates the need to adjust the cables  5 ,  6  when changing reels  22  with varying track radii R N    104 . 
     The variable rate has several advantages. In an essentially flat, level terrain, it may be desirable to obtain maximum acceleration very quickly, thus a fast rate may be desirable. However, in more rugged terrain, in the woods or in wet or muddy conditions, a slow rate may be better, to assure that too much acceleration is not applied, or that it should be applied with more discrimination. The interchangeable throttle reels  22  allow a rate to be selected from a variety of choices. 
     In conjunction with the variable throttle reels  22 , the configuration of the elbows  28 ,  30  is important. The flared portion  60  of the elbows  28 ,  30  was referred to above and pointed out in  FIG. 6 . A detailed view is provided in  FIG. 9  showing an elbow  30  with dashed circles which represent the radii  102 ,  103  of the first and second throttle reels  22  discussed above. A portion of pull cable  6  is shown routed through the elbow  30  and attaching to the circumference of the dashed lines. It can be seen how the angle of the cable  6  varies as it leaves the confines of the elbow  30  and attaches to the first and second throttle reels  52 ,  54  at their radii  102 ,  103 . 
     The flared portion  60  feature is important because with the variation in track radii R N    104  possible, the angle at which the push and pull cables  5 ,  6  emerge from the elbows  28 ,  30  and wrap around the reel tracks  50  will vary as demonstrated in  FIG. 9 . By providing the flared portion  60 , the push and pull cables  5 ,  6  are free to run naturally into groove  46  in the reel  22  without binding to ensure a precise and smooth operation with excellent throttle return characteristics. It can be appreciated that without the flared portion  60 , the pull cable  6  (and also push cable  5 , in a similar manner) would abrade at the exit of elbows  28 ,  30 . If the cables were constrained to exit at a steep angle and to rub on the elbows  28 ,  30 , there would be more friction, leading to a throttle that drags and possibly hold the throttle in the open position requiring the operator to use the push cable to close it. This is thus an important and novel feature. 
     It is noted that the capture notch locations for the push/pull cable have been designed so that the throttle handle will not rotate on the handlebar when you change throttle reels having varying track radii. This eliminates the need to make cable adjustments when using a directional grip with a specific pattern that requires it to be kept in the same position for rider comfort and or performance. (i.e. half waffle, etc.) This is considered to be a considerable advantage. 
     It is also noted that capture notches on the reels have been located to prevent the need to adjust the cables when changing the reels. There is little or no “slack” to be adjusted for when changing the reels. This, too, is considered to be a considerable advantage. 
     While various embodiments have been described above, it should be understood that they have been presented by way of example only, and not limitation. Thus, the breadth and scope of a preferred embodiment should not be limited by any of the above described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents. 
     INDUSTRIAL APPLICABILITY 
     The present variable throttle  10  is well suited generally for use in motorcycles and other small vehicles. Acceleration of the vehicle ranges from a minimum, where the engine idles, to maximum acceleration, and the opening of the butterfly valves in the carburetor or throttle body over this range can vary from a gradual increase over a relatively large angular twist range of the hand throttle to a very sharp increase from minimum to maximum over a relatively small twist range of the hand throttle. 
     If the carburetor or throttle body control is sensitive to angular rotation, a small rotation of the hand throttle will result in a large carburetor or throttle body adjustment. Conversely, if the carburetor or throttle body control is less sensitive, the hand throttle twist range between minimum and maximum acceleration will be larger, allowing finer control. This degree of control or sensitivity will be referred to as the “throttle rate”. A throttle which goes from minimum to maximum in a small angular range will be referred to as having a “fast rate”, and one which has a large throttle angle range will be referred to as having a “slow rate”. 
     It is well known that different throttle rates are useful for different situations and environments. For example, a rider in the desert who is on very flat terrain with no obstacles may be primarily interested in applying maximum acceleration as quickly as possible, and therefore a more sensitive throttle with a fast rate may be preferred. Conversely, a rider in the woods who is operating in hilly terrain, or in rain or mud-slickened conditions, may want to have more precise control, and thus a less sensitive throttle with a slow rate is preferred. 
     Typically, a vehicle is configured to have a fixed throttle rate, which is not variable. Modifying the throttle rate is typically not an operation which is easily done. A variable throttle which can facilitate this operation in a quick and easy manner will have great utility and industrial applicability. 
     The present variable throttle  10  includes throttle reels  22  that are interchangeable, and any one of a number of variations of these throttle reels is available to be mounted in the central cavity  20  to produce a variety of throttle rates. 
     The interchangeable throttle reel  22  generally includes a reel body  42  having two side walls  44  which define a groove  46  having a groove floor  48 . The side portions  44  thus have a greater radial dimension than the groove floor  48 , thus making a track  50  that the push cable  5  and pull cable  6  will travel upon and to which they will be confined. 
     As examples of the operation of the variable throttle  10 , a first throttle reel  52  includes a second, smaller radius R 2    102  extending to a dashed line corresponding to the groove floor  48 , thus showing the radial distance from the central axis line  100  to the groove floor  48 . A second throttle reel  54  includes a still smaller radius R 3    103  from the central axis line  100  to the groove floor  48 . 
     Both the first throttle reel  52  and second throttle reel  54  include receiving notches  56  which receive the engaging flanges  40  of the throttle handle  24 . The throttle reels  52 ,  54  also include capture notches  58  for barrel wire end fittings  8  for the throttle assembly  10  ends of the push cable  5  and the pull cable  6 . The capture notches  58  for the first throttle reel  52  having R 2 , are closer together than the capture notches  58  of second throttle reel  54  having R 3 . 
     The push cable  5  and pull cable  6  are inserted through the cable housings  7  and the first and second elbows  28 ,  30 . Barrel wire end fittings  8  are attached to both ends of the cables  5 ,  6 . The barrel wire ends  8  at the ends of the cable  5 ,  6  nearest the carburetor  2  are fitted to the capture notches  9  in the bell crank  3 , and generally remain in this position. When the throttle assembly  10  is to be assembled, an interchangeable throttle reel  22  is selected from the provided variety of throttle reels  22  having differing track radii R N    104 . The throttle handle  24  is positioned so that the engaging flanges  40  of the engaging shaft  38  enter the receiving notches  56  of the throttle reel  22 . It should be noted that the reels  22  have been designed so that they can be installed onto the throttle handle  24  in only one direction, thus eliminating the possibility of putting the reels  22  on incorrectly. The barrel wire end fittings  8  at the throttle assembly  10  ends of the push cable  5  and pull cable  6  are placed within the capture notches  58  of the throttle reel  22 . The throttle handle  24  with attached throttle reel  22  is placed within either the first or second housing portions  14 ,  16  of the throttle housing  12 . The throttle reel  22  is positioned within the central cavity  20 , and with retaining ring  36  of the throttle handle  24  is positioned within the retaining ring cavity  27 . The first elbow  28  is fitted into the elongated cavity portion  26  of the first housing portion  14  and the second elbow  30  is fitted into the elongated cavity portion  26  of the second housing portion  16 . The first housing portion  14  and second housing portion  16  are fitted together and attached with fasteners  18  to make the completed throttle housing  12 . A boot  62  is provided which overlaps a portion of the throttle housing  12  and prevents dirt and grime from entering the throttle assembly  10 . 
     The push cable  5  and the pull cable  6  travel in the track  50  created between the side walls  44 , and as the throttle reel  22  is rotated by rotating the attached throttle handle  24 , the push and pull cables  5 ,  6  push and pull at their opposite ends in the manner of a pulley to rotate the bell crank  3  of the carburetor  2 . The push cable  5  and pull cable  6  each travel a limited linear distance D  11  when twisting the throttle handle  24  from an idling position to maximum acceleration. The push/pull cable wires  5 ,  6  are captured between the side walls  44  of the reel  22  to prevent the cables from getting caught between the side of the reel  22  and throttle housing  12 . 
     The throttle reels  22  are configured with varying track radii R N    104 . In a throttle reel  22  with a large track radius R 2    102 , the circumference of the throttle reel track  50  is larger than the circumference of the throttle reel track  50  when the track radius R 3    103  is smaller, according to the formula Circumference=2πR. Thus, since the limited linear travel distance D  11  of the push and pull cables  5 ,  6  is fixed by the carburetor or throttle body, in a throttle assembly  10  having a larger track radius R 2    102  needs less angular rotation to move the push and pull cables  5 ,  6  the limited linear travel distance D  11 . Thus, for a large track radius R 2    102 , the angular throttle travel range shown as β 1   68  from minimum to maximum will be smaller than for a smaller track radius R 3    103 . This means that in a reel  52  with a large radius R 2    102 , the throttle control will be more sensitive to angular rotation. A small rotation of the throttle handle  24  will result in a large carburetor adjustment. Conversely, in a reel  54  having a small track radius R 3    103 , the angular throttle travel range shown as β 2   70  between minimum and maximum will be larger, and throttle control will be less sensitive, allowing finer control over acceleration. This variable degree of throttle control or sensitivity will be referred to as throttle rate. A throttle which goes from minimum to maximum in a small angular range will be referred to as having a “fast rate”, and one which has a large throttle angle range will be referred to as having a “slow rate”. 
     The capture notches  58  in throttle reel  22  are located to compensate for the difference in circumference of the throttle reel track  50 . Thus the capture notches  58  on a large track radius R 2    102 , are placed farther apart than the capture notches  58  on a smaller track radius R 3    103 . 
     In conjunction with the variable throttle reels  22 , the configuration of the elbows  28 ,  30  is important. The flared portion  60  of the elbows  28 ,  30  is important because with the variation in track radii R N    104  possible, the angle at which the push and pull cables  5 ,  6  emerge from the elbows  28 ,  30  and wrap around the reel tracks  50  will vary. By providing the flared portion  60 , the push and pull cables  5 ,  6  are free to run naturally into groove  46  in the reel  22  without binding to ensure a precise and smooth operation with excellent throttle return characteristics. It can be appreciated that without the flared portion  60 , the pull cable  6  (and also push cable  5 , in a similar manner) would abrade at the exit of elbows  28 ,  30 . If the cables were constrained to exit at a steep angle and to rub on the elbows  28 ,  30 , there would be more friction, leading to a throttle that drags and possibly hold the throttle in the open position requiring the operator to use the push cable to close it. 
     The capture notch locations for the push/pull cable have been designed so that the throttle handle will not rotate on the handlebar when the user is to change throttle reels having varying track radii. This eliminates the need to make cable adjustments when using a directional grip with a specific pattern that requires it to be kept in the same position for rider comfort and or performance. 
     Capture notches on the reels have been located to prevent the need to adjust the cables when changing the reels. There is little or no “slack” to be adjusted for when changing the reels. 
     In changing from a “fast” variable rate, such as used on flat terrain, where fast acceleration is desired, to a “slower” rate, an operator would be involved in changing a reel  52  with a large radius R 2    102 , to a reel  54  having a small track radius R 3    103 , where the throttle control will be less sensitive, allowing finer control over acceleration. 
     To accomplish this, the throttle assembly  10  is partially disassembled. The boot  62  is disengaged from the throttle housing  12  by sliding it down the cable housing  7 . Fasteners  18  are then loosened, allowing the first housing portion  14  and second housing portion  16  to be separated. Handle  24  is then withdrawn so that engaging flanges  40  disengage from the receiving notches  56  in the reel  52 . The barrel wire end fittings  8  of the pull cable  6  and the push cable  5  are then removed from the capture notches  58  of the reel  52 , and the reel  52  is thus disengaged from the throttle assembly  10 . A new reel  54  of appropriate throttle rate is then selected, and the barrel wire end fittings  8  of the pull cable  6  and the push cable  5  are then inserted into the capture notches  58  of the reel  54 . The handle  24  is then replaced so that engaging flanges  40  engage the receiving notches  56  in the reel  54 . The first housing portion  14  and second housing portion  16  are reassembled and fasteners  18  are then used to attach the housing portions  14 ,  16 . The boot  62  is the slipped up the cable housing  7  to re-engage the throttle housing  12 , and the vehicle is ready to be operated. 
     Thus, it is apparent that the replacement of the throttle reels is a very quick and easy operation, and far superior to previous methods of modification, which may require the user to grind off material or add more material, such as epoxy and then file it smooth. 
     For the above, and other, reasons, it is expected that the variable throttle  10  of the present invention will have widespread industrial applicability. Therefore, it is expected that the commercial utility of the present invention will be extensive and long lasting.