MOTORCYCLE

Abstract: A motorcycle comprises an engine/transmission assembly (5) having an output sprocket (6) which is connected to the rear wheel (3) by a chain drive (7), and to the front wheel (4) via a train drive comprising a first chain (8), a sprag clutch (9), a second chain (10), a CV joint (12), a third chain (15), and a fourth chain (21). The sprag clutch (9) permits the front wheel to over run the rear wheel during steering, and the CV joint transfers drive from chassis mounted components to the front forks without interfering with the steering action of the motorcycle.

Description: MOTORCYCLE This invention relates to a motorcycle, and in the preferred embodiment provides a motorcycle which has front and rear wheels which are driven from a common engine. It is clear that off-the-road performance of high power motorcycles would be improved if both front and rear wheels were driven. However, there are two significant problems in obtaining this result. Firstly, there is no satisfactory simple mechanical system fcr transmitting drive power from the prime mover o the front wheel. Secondly, even if some means is devised for transmitting power from the prime mover to the front wheel, means must be provided to permit differential rotation of the front and rear wheels during cornering. According to the present invention there is provided a motorcycle comprising: a source of rotary power; and drive means coupling the front and rear wheels of the motorcycle to the source of rotary power, wherein the drive means incorporates a one way drive device whereby one wheel may turn faster than the rotational speed imposed upon it by the drive means. Preferably, the one way drive device permits the front wheel of the motorcycle to turn at a rotational speed greater than the rotational speed imposed upon it by the drive means. This arrangement permits differential rotation of the front and rear wheels as necessitated by, for example, steering of the motorcycle. Preferably, the one way drive device is in the form of a sprag clutch which allows the front wheel to over-run the rear wheel when necessary. Preferably the drive means comprises a constant velocity joint mounted on or adjacent the steering head of the motorcycle in such a way that the input of the CV joint is constrained to rotate about an axis fixed relative to the motorcycle frame, and the output of the CV joint is constrained to rotate about an axis fixed relative to the front forks. In this manner, drive can be transmitted to the front wheel without substantially interfering with the steering action of the motorcycle. In one embodiment of the invention drive from the CV joint to the front wheel is via an idler gear which is mounted at the juncture of two pivotally connected arms, the first arm being constrained at the end remote from the idler gear to pivot about the axis of the output shaft of the CV joint, and the second arm being constrained to pivot at the end thereof remote from the idler gear about the axis of rotation of the front wheel. This arrangement enables chain tension to be maintained without interfering with the telescopic suspension of the front wheel. In a second embodiment of the invention, the motorcycle includes a front suspension assembly mounted on the frame for pivotal movement about a steering axis, the front suspension assembly comprising: a first arm which extends from adjacent the steering axis downwardly and rearwardly to a point to the rear of the front wheel; second and third arms connected to the lower end of the first arm for pivotal movement about a common pivot axis, the second and third arms extending along respective sides of the front wheel from the pivot axis to the axis of rotation of the front wheel where they are rotatably connected to the front wheel to support the front wheel in use; and a linkage interconnecting the second and third arms with the first arm, said linkage including a resiliently deformable member which resiliently opposes upward movement of the front wheel relative to the chassis and means constraining the second and third arms to move conjointly as the front wheel moves up and down relative to the chassis in use whereby the axis of rotation of the wheel at all times remains parallel to the p vot axis. The front arm preferably comprises two rigidly interconnected members spaced apart one on either side of the longitudinal central plane of the front wheel. The linkage may then comprise a wishbone pivotally connected to the members of the first arm to provide a pair of forwardly extending legs having terminal ends which respectively overlie the second and third arms, and a single rearwardly extending leg. Each forwardly extending leg is connected to the one of the second and third arms which it overlies by a rigid strut, and the rearwardly extending leg is coupled to the lower end of the first arm by a spring damper. With this arrangement, vertical upward movements of the front wheel causes upward movement of the struts thereby pivoting the wishbone to produce downward movement of the rearwardly extending leg thereof to compress the spring damper. This arrangement has the advantage that the characteristics of the suspension may readily be varied by altering the length of the struts, and/or the position of the interconnection between the struts and the second and third arms. Further, the use of a first arm comprising spaced apart members, in combination with a wishbone as described above enables the periphery of the wheel to enter the zone between the members of the first arm in the extreme upper position of the front wheel, thereby enabling a relatively compact arrangement to provide substantial front wheel travel. The invention will be better understood from the following description of a preferred embodiment, given by way of example only, reference being had to the accompanying drawings wherein: Figure 1 is a schematic side view of a preferred embodiment of the invention; Figure 2 is a schematic front view of part of the embodiment of Figure 1 ; Figure 3 illustrates schematically a side view of a portion of a second embodiment of the invention; and Figure 4 is a view in the direction of the arrow IV of Figure 1 , with the wheel partly broken away in the interests of clarity. Referring to Figure 1 the motorcycle 1 illustrated comprises a frame 2, rear wheel 3, and front wheel 4. An engine and transmission assembly 5 is mount on the frame in conventional manner and includes an output sprocket 6 which drives the rear wheel 3 via a chain 7 in conventional manner. A second chain 8 is driven from the sprocket 6 and in turn drives a sprag clutch 9. The output of the sprag clutch 9 drives a chain 10 which in turn drives the input shaft 11 of a constant velocity joint 12. The input shaft 11 is mounted in a manner which permits it to rotate only about an axis which is fixed relative to the chassis 2. The pivotal axis 13 of the constant velocity joint is located on the axis of the steering head, and the output shaft 14 of the constant velocity joint is constrained to rotate about an axis which is fixed relative to the front forks of the motorcycle. A sprocket is mounted on the output shaft 14 and drives a chain 15 which in turn drives an idler wheel 16 mounted at the apex of two articulated arms 17,18. The end of the arm 17 remote from the idler wheel 16 pivots about the axis of the output shaft 1 , and the end of the arm 18 remote from the idler wheel 16 pivots about the axis of rotation 19 of the front wheel 4. The idler wheel 16 drives a sprocket 20 fast with the front wheel via a chain 21. The bearings upon which the idler wheel 16 is mounted are contained in a variable eccentric mounting which enables the chains 15,21 to be tensioned. The arrangement of the arms 17,18 enables the chain drive arrangement to accommodate the telescopic movement of the front wheel in conventional manner. Referring now to Figures 3 and 4, the motorcycle 101 comprises a chassis 102 defining a steering axis 103 about which the front suspension 104 is pivotally turned in use by means of conventional handle bars (not shown). The front suspension assembly comprises a first arm 105 which extends from adjacent the pivot axis 103 downwardly and rearwardly to a point behind the front wheel 106 and substantially at the same horizontal level as the axis of rotation 107 of the front wheel, when the motorcycle is at a nominal loading. The lower end 108 of the first arm defines a pivot axis 109 about which second and third arms 110,111 are pivotally mounted. The front ends of the arms 110,111 are interconnected by the spindle 115 about which the front wheel rotates, and accordingly the arms 110,111 support the front wheel in use. Referring particularly to Figure 4, it will be seen that the first arm 105 comprises a pair of members 112,113 rigidly interconnected by plates 114 at the upper ends thereof, and by a suitable member (not shown) at the lower ends thereof. The members 112,113 are spaced apart on either side of the central plane 116 of the front wheel 106. A wishbone 117 is pivotally mounted via pivot pins 118,119 on the members 112,113 to provide a pair of forwardly extending legs 120,121 and a single rearwardly extending leg 122. The legs 120,121 each terminate at a point vertically above one of the arms 110,111, and each arm 110 r 111 is connected to the overlying leg of the wishbone by a respective strut 123. A combined spring and damper 124 of conventional design is located between the rearwardly extending leg 122 of the wishbone and the member which interconnects the lower ends of the members 112,113. In use, upward movement of the wheel 106 relative to the chassis is transferred via struts 123 to the wishbone 117 and causes pivotal movement of the wishbone which is resiliently opposed by the spring damper 124. The effect of the wishbone is to ensure that the arms 110,111 move conjointly in use so that the axis of rotation 107 of the front wheel always remains parallel to the pivot axis 109. It will be noted that in the extreme upper position of the front wheel illustrated in broken line at 125 the periphery of the front wheel is able -co enter the space between the legs 120,121 of the wishbone 117 and the space provided between the members 112,113 of the first arm 115. The characteristics of the suspension can be adjusted by varying the length of the struts 123 and/or the position of the point 126 along the arms 1l0 r 111 at which the struts 123 are connected. Although of general utility the above described arrangement is particularly well suited to a motorcycle of which the front wheel is driven by a chain drive extending from a constant velocity joint 127 mounted on the first arm 105 immediately below the pivotal connection with the chassis. Drive for the CV is derived from a one way drive device, as in the embodiment of Figures 1 and 2. Drive can be taken from the constant velocity joint 127 via a first chain 128 to an idle sprocket 129 mounted to rotate about the pivot axis 109, and from the idle sprocket 129 via a second chain 130 to a drive sprocket 131 rotationally fast with the front wheel. It will be noted that with the above described suspension arrangement there is no change in length of the chains 128 or 130 as the front wheel moves up and down in use, and accordingly no arrangements need be provided to accommodate such changes of length.

Claims: CLAIMS 1. A motorcycle comprising a source of rotary power and drive means coupling the front and rear wheels of the motorcycle to the source of rotary power characterized in that the drive means comprises a one way drive device (9) whereby one wheel (4) may turn faster than the rotational speed imposed upon it by the drive means. 2. A motorcycle according to claim 1 characterized in that the one way drive device (9) is a sprag clutch. 3. A motorcycle according to claim 1 and claim 2 characterized in that the drive means comprises a constant velocity joint (12) mounted on or adjacent the steering head of the motorcycle in such a way that the input (11) of the CV joint (12) is constrained to rotate about an axis fixed relative to the motorcycle frame and the output (14) of the CV joint is constrained to rotate about an axis fixed relative to the front forks. 4. A motorcycle according to claim 3 characterized in that drive from the CV joint (12) is taken by a chain (15) to an idle wheel (16) which is mounted at the juncture of two pivotally connected arms (17 18) / the first arm (17) being constrained at the end remote from the idle gear (16) to pivot about the axis of the output shaft (14) of the CV joint, and the second arm (18) being constrained to pivot at the end thereof remote from the idle gear (16) about the axis of rotation (19) of the front wheel. 5. A motorcycle according to claim 3 or claim 4 characterized in that the drive means comprises a first chain (8) which drivingly connects an output sprocket of the source of rotary power to the sprag clutch, and a second chain (10) which connects the output of the sprag clutch to the input of the CV joint. 6. A motorcycle according to any preceding claim characterized in that the front suspension assembly comprises a first arm (105) which extends fro« adjacent the steering axis (103) downwardly and rearwardly to a point to the rear of the front wheel (106); second and third arms (110,111 ) connected to the lower end of the first arm (105) for pivotal movement about a common pivot axis (109), the second and third arms extending along respective sides of the front wheel (106) from the pivot axis (1£)9) to the axis (107) of rotation of the front wheel where they are rotatably connected to the front wheel to support the front wheel in use; and a linkage interconnecting the second and third arms with the first arm, said linkage including a resiliently deformable member (124)_which resiliently opposes upward movement of the front wheel relative to the chassis (102) and means constraining the second and third arms (110,111 ) to move conjointly as the front wheel moves up and down relative to the chassis (102) in use whereby the axis of rotation (107) of the front wheel at all times remains parallel to the pivot axis (109). 7. A motorcycle according to claim 6 wherein the first arm comprises two rigidly interconnected members (112,113) spaced apart one on either side of the longitudinal central plane (116) of the front wheel and the linkage comprises a wishbone (117) pivotally connected to the members (112,113) to provide a pair of forwardly extending legs (120,121) each of which is connected to one of the second and third arms (110,111) by a rigid strut, the rearwardly extending leg (112) of the wishbone being coupled to the lower end of the first arm by a spring damper.

Inventors: WATTS CHRISTOPHER DAVID GEORGE, WATTS, CHRISTOPHER, DAVID, GEORGE
Applicants: WATTS CHRISTOPHER DAVID GEORGE, WATTS, CHRISTOPHER, DAVID, GEORGE
Application year: 1988
Main classification: B62M7
IPC codes: B62K25, B62M7, B62M23