Superior handling not only enhances a racer's chance at victory, it renders any motorcycle safer to ride. An improved ride also makes motorcycling more enjoyable. To improve a motorcycle's handling and ride characteristics, manufacturers will devise different ways to reduce the weight of the bike without adversely affecting its structural integrity, such as employing lighter wheels and brakes. They will also experiment with variations in the bike's weight distribution and strive to improve motorcycle brakes and their suspension systems.

Manufacturers will also experiment with variations in the configuration of the motorcycle, although such variations are generally very minor and the improvements realized are generally slight. The present invention relates to a motorcycle configuration which substantially improves the handling characteristics of motorcycles designed for on- road use and makes such bikes more"user friendly." Included in this novel configuration is a new swing arm suspension system for the rear wheel which cooperates with the new motorcycle configuration to enhance further the performance characteristics of the motorcycle.

In designing any motorcycle, numerous compromises must be made. For example, a bike having a longer wheel base will generally be more stable in straight-line operation than one with a shorter wheel base, but may have less torsional rigidity and produce handling problems. A shorter wheel base should produce more responsive steering and is thus normally quicker to react but tends to produce less straight-line stability. A motorcycle with a shorter wheel base is also more susceptible to flipping over

backwards during very rapid acceleration (a"wheelie") and over forwards (a"stoppie") during hard braking when the weight of the motorcycle and its rider are thrust forwardly, predominantly onto the front wheel. To reduce the chance of flips resulting from wheelies and stoppies, the wheel base can be lengthened, but at the probable expense of responsiveness. It would be highly desirable to provide a motorcycle configuration which combined the benefits of both long and short wheel bases but not their detriments.

Aerodynamics is another aspect of motorcycle design.

An important part of the aerodynamic performance of a motorcycle includes the frontal area package made up of both bike and rider. Other things being equal, the larger the package, the greater the wind resistance. On most conventional motorcycles, frontal area is largely determined by the positioning of the rider on the bike. The handle bars are lowered and the foot pedals are moved rearward to lower the profile of the rider. While this may reduce wind resistance, it also reduces comfort and is tiring on the rider's arms, wrists, back and neck. Again, it would be desirable to obtain the benefits of a smaller frontal area package, but without a tradeoff in comfort.

The motorcycle configuration of the present invention provides the improved handling characteristics associated with a reduction in weight, improved braking and suspension systems, both long and short wheel bases and a smaller frontal package area but without the negative tradeoffs generally associated with many of these features. As a result, the motorcycle of the present application has excellent handling and performance characteristics and is both easy and fun to ride.

Summary of the Invention Briefly, the present invention relates to a motorcycle having improved handling characteristics as a result of a configuration providing a substantial

reduction in the elevation of the center of gravity relative to conventional motorcycle configurations. The motorcycle of the present invention positions the fuel tank between the engine and rear wheel on the lowermost portion of the frame and the rider's seat directly over the fuel tank. As a result, the seat is disposed below the elevation of the tops of the motorcycle wheels. By so positioning the rider's seat, the composite center of gravity defined by the rider and motorcycle is substantially lowered and the handling characteristics of the motorcycle and the overall ride are substantially improved. It also allows for a slight increase in the wheel base of the bike to enhance stability while concurrently improving the responsiveness of the bike. In addition, the motorcycle is more resistant to flipping rearwardly and forwardly during rapid acceleration and deceleration thereby further enhancing the rider's control over the bike and increasing the effectiveness of the brakes during attempted rapid deceleration. The aforesaid positioning of the rider's seat also allows for the positioning of the rider's feet forwardly of the rider thereby providing a more comfortable riding positing while concurrently presenting a smaller frontal package to reduce wind resistance.

The motorcycle of the present invention is preferably provided with a horizontally disposed swing arm which provides a protective housing for the rear shock absorber and carries the shock absorber in a bell-crank mounting to provide an adjustable and highly durable rear suspension system. The horizontal disposition of the swing arm and shock absorber additionally complements the above- described motorcycle configuration by further lowering of the center of gravity of the motorcycle. The present invention also preferably employs a single or twin- cylinder engine to reduce the transverse dimension of the motorcycle forwardly of the seat and facilitate the

comfortable positioning of the rider's legs in a forward position.

It is the principal object of the present invention to provide an improved motorcycle for on-road use which exhibits superior handling and other ride characteristics.

It is another object of the present invention to provide an on-road use which is easier and safer to ride than conventional motorcycles and is also fun to ride.

It is yet another object of the present invention to provide a motorcycle for on-road use which is both highly stable and very responsive.

It is still another object of the present invention to provide a motorcycle for on-road use which is both highly responsive and resistant to flipping during rapid acceleration and deceleration.

It is a further object of the present invention to provide a motorcycle for on-road use which is both comfortable to ride and presents a small frontal package to minimize wind resistance.

It is a still further object of the present invention to provide an adjustable, highly durable swing arm assembly for a motorcycle which provides an adjustable and highly durable mounting of the rear shock absorber and which positions the shock absorber in a horizontal disposition to lower further the center of gravity of the motorcycle.

These and other objects and advantages of the present invention will become readily apparent from the following detailed description, taken in conjunction with the accompanying drawings.

Brief Description of the Drawings Figure 1 is a side view of a motorcycle of the present invention.

Figure 2 is a side view of the motorcycle of the present invention with a rider illustrated thereon in phantom lines.

Figure 3 is a top plan view of a portion of the preferred embodiment of the motorcycle of the present invention showing the positioning of the preferred swing arm thereon.

Figure 4 is a side view of the preferred embodiment of the motorcycle of the present invention.

Figure 5 is a partial top plan view of the preferred swing arm assembly of the present invention.

Figure 6 is a side schematic view of the preferred swing arm assembly of the present invention showing the movement of the swing arm as the rear motorcycle wheel moves upwardly with respect to the frame.

Figure 7 is a schematic side view of the preferred swing arm assembly of the present invention showing the movement of the swing arm as the rear motorcycle wheel moves downwardly with respect to the frame.

Figure 8 is a sectional view taken along the line 8-8 in Figure 6.

Figure 9 is a sectional view taken along the line 9-9 in Figure 1.

Figure 10 is a side view of the bell crank employed in the swing arm assembly of the present invention.

Description of the Preferred Embodiments The motorcycle 10 of the present invention differs from conventional motorcycles primarily in the configuration of the frame 12 and the positioning of various components so as to lower the driver's seat 14 to an elevation of not more than 20 inches above the ground, and more preferably, an elevation of not more than about eighteen inches. So positioned, the seat 14 is disposed below the tops of both the front and rear wheels 16 and 18. A typical seat elevation for a motorcycle designed for on-road use is about twelve inches higher than seat 14.

Motorcycle seats are padded for comfort and seat 14' is preferably provided with padding 14'. The thickness of

padding 14'will necessarily affect the elevation of the rider relative to the ground and thus affects the elevation of the composite center of gravity of the motorcycle and rider. However, the thickness of padding 14'is only relevant here when the padding is compressed (when a rider is sitting on the seat) and different paddings will vary in the extent to which they will compress even under identical loads. Accordingly, the seat elevations recited above refer to the distance above the ground of the substantially horizontal rider support surface S defined by seat 14 and do not include the thickness of any compressible padding 14'thereon.

To effect the positioning of seat 14 at such a low elevation, the frame 12, which is preferably of a metal tubular construction, is configured so as to extend rearwardly and downwardly at a relatively steep inclination from the forward upper end 20 thereof in which the front forks 22 are mounted in a conventional manner.

The forward end portion 20 of frame 12 is triangularly shaped so as to form an enclosure 21 for the oil tank (not shown). A centrally disposed forward support bar 24, preferably formed of box-shaped metal tubing, extends downwardly and slightly rearwardly from the forward end portion 20 of the frame to the laterally and rearwardly extending lowermost tubular supports 25 of frame 12. A support truss (not shown) is provided on both sides of bar 24 which extends between and is welded to bar 24 and the upper forward end portion 20 of the frame for additional support. Support bar 24 also carries the foot rests 26 proximate its lower end, forwardly of and below seat 14.

A pair of converging tubular members 28A and 28B project downwardly and rearwardly from both sides of the forward frame end portion 20 to a pair of vertical support members 30 disposed on opposed sides of the gas tank 32 proximate the forward ends 32A of gas tank 32 and 14A of seat 14.

A tubular member 28C extends diagonally adjacent gas tank

32 to lower supports 25 from the junctures of members 28A and 28B and vertical members 30.

Frame 12 also includes a pair of vertically extending tubular members 31 disposed on opposite sides of the frame proximate the rearward ends 32B of gas tank 32 and 14B of seat 14. Members 31 extend upwardly from the lowermost frame members 25 on opposite sides of frame 12 and are spanned by a pair of vertically spaced horizontal frame members (not seen) disposed proximate the upper and lower rear edges of fuel tank 32. Another pair of tubular support members 33 extend from the lowermost tubular supports 25 of frame 12 on opposite sides thereof to an upper rear frame member (not shown) disposed within rear fender 35 and to which the upper ends of the rear shock absorber 44 are secured. It is to be understood that numerous variations in the above-described frame design could be employed in the present invention to provide the necessary structural support for the motorcycle, protection for the gas tank 32, and the positioning of the gas tank 32, seat 14 and engine 15 as above-described.

The swing arm assemblies 34 for carrying the twin suspension on motorcycle 10 are pivotally mounted on opposite sides of frame 12 on the vertical supports 30 at 37. The swing arm assemblies 34 each compromise four tubular members 34A-34D which are joined together adjacent a hub 39 and rearwardly diverge therefrom. Members 34A- 34D terminate at their divergent end in a pair of spaced parallel upstanding members 36 (only the outermost member being shown). A pair of vertically spaced laterally extending tubular members (not seen) extend between members 34A and 34C and members 34B and 34D at their divergent ends and an array of four converging tubular members (only 40A and 40B being seen) extend from members 34A-D at their divergent ends to a wheel pivot mounting fitment 42. The spring shocks 44 are carried by and extend between upstanding flanges 46 on the rear ends of the swing arm assemblies 34 and opposite sides of the

frame 12 on the upper end portions of tubular members 33 adjacent fender 35.

As seen in Figure 1, the motorcycle 10 can also include an air box 52 defining air inlets 54 (only one being shown) which communicate with the carburetor throats 56 via air ducts 58. An air bag 60 can also be carried by the air box to protect the rider. The engine 15, exhaust tube 62, muffler 64 front and rear fenders 35 and 66 are also shown in Figures 1 and 2.

The above-described frame configuration enables the gas tank 32 to be mounted on the lowermost portion of frame 12 and the rider's seat 14 to be disposed directly over the gas tank 32, while the motorcycle frame 12 and swing arm assemblies 34 cooperate to project about and protect the gas tank. The elevation of the seat 14 above the ground is thus minimized, limited solely by the presence of the drive chain. Through such a configuration, a seat elevation of about 18 inches is obtained plus the thickness of the seat padding 14'. The use of a direct drive in lieu of a drive chain could allow for further reduction in the elevation of the motorcycle seat.

The effect of the lowering of the elevation of the rider's seat is illustrated in Figure 2 wherein a motorcycle rider 70 is depicted thereon in phantom lines.

As is apparent from Figure 2, the center of gravity of motorcycle 10 with the rider 70 seated thereon (referred to herein as"the composite center of gravity") is substantially lower than the composite center of gravity of the same rider seated on a conventionally configured motorcycle. Additionally, such a seating position allows for the foot rests 26 to be positioned below and forwardly of the rider which is both a comfortable riding position and, in cooperation with the positioning of seat 14, presents a small frontal package to minimize wind resistance. Through such a configuration, motorcycle 10

provides both comfort and superior handling characteristics.

A preferred embodiment of the present invention is shown in Figures 3-8 and 10. The motorcycle 100 illustrated therein differs from motorcycle 10 primarily in the configurations of the swing arm assemblies and the shock absorbers carried thereby. While Figure 4 includes minor modifications in the configuration of the motorcycle frame, such modifications do not affect the positioning of motorcycle components described above, e. g., seat, gas tank, engine, footrests, etc. and thus are merely illustrative of variations in the frame configuration which can be made in carrying out the present invention.

As best seen in Figures 3-5, swing arm 102 comprises a tapered protective housing portion 108 for a shock absorber 106, a transversely disposed cylindrical pivot mount 110 formed at the forward end of housing portion 108 for the pivotal securement of the forward end of the swing arm 102 to opposite sides of the motorcycle frame 112 at 114. This pivotal connection is provided by a pair of locking bolts (not shown) threadably engaging the opposed ends 110'and 110''of pivot mount 110 (see Fig. 5). The protective housing portion 108 of swing arm 102 is open at its upper end 115 to facilitate the mounting of the shock absorber 106 therein and is provided with a smaller cutout area 116 in the lower surface thereof to provide visual and physical access to the under side of the shock absorber 106.

A tubular portion 118 of swing arm 102, substantially rectangular in cross-section, extends rearwardly from housing portion 108, terminating in a hub mount 124 to provide a bolted securement of the rear end 126 of swing arm 102 to the rear axle of the motorcycle adjacent rear wheel hub 128 as shown in Figure 5. The tubular portion 118 includes a curvilinear portion 120 so as to provide clearance for the rear motorcycle wheel 112. A bolt anchor 130 is provided on swing arm 102 adjacent the

rearward end of the curvilinear portion 120 of the swing arm 102 to anchor the swing arm to the rear brake calipers (not shown).

The shock absorber 106 preferably utilized with swing arm 102 is a small oil or gas filled spring shock such as a Koni model no. 2812. Shock absorber 106 is secured at its forward end within the housing portion 108 of swing arm 102 by means of a conventional flexible ball joint connection 134 intermediary of the extended ends 110'and 110"of pivot mount 110 as seen in Figure 5. The rear extensible portion 136 of shock absorber 106 is also secured by means of a flexible ball joint connection 138 to a bell crank 140. Bell crank 140 is pivotally mounted on and between a pair of spaced-apart flanges 142 projecting downwardly from the underside of the swing arm 102 at the forward end of the housing portion 108 thereof as shown in Figures 6-8. One end 144 of a push/pull rod 144 is pivotally mounted on the bell crank 140 at 147.

The other extended end 148 of push/pull rod 146 is pivotally mounted on the motorcycle frame 112 at 149.

The configuration of bell crank 140 is best seen in Figures 8 and 10. As seen therein, the bell crank comprises a lower base portion 140A and a pair of spaced- apart plates 140B and 140C projecting upwardly from base portion 140A. Plates 140B and 140C can be welded onto base portion 140, or the bell crank 140 can be formed of single-piece construction. Bell crank 140 is provided with a pair of spaced and axially aligned apertures 152 in the upper end portions of plates 140B and 140C for the pivotal mounting thereon of the rear end portion 136 of the shock absorber 106 by means of ball joint connection 138. An aperture 154 is provided in the lower base portion 140A of the bell crank for pivotally mounting the bell crank between the depending flanges 142 on the underside of the swing arm 102. A pair of axially aligned apertures 156 are also provided in bell crank plates 140B

and 140C for the pivotal securement of the bell crank to the push/pull rod 146.

To provide the desired shock absorption characteristics for the rear wheel of the motorcycle 100, the relative positioning of apertures 152,154 and 156 on bell crank 140 are significant. For use with a Koni model no. 2812 shock absorber and a rider weighing from about 150 to 220 pounds, excellent performance has been realized by vertically aligning apertures 152 and 154 such that the spacing therebetween is 4.3 inches. This spacing is designated L2 in Figure 10. The distance between apertures 154 and 156 (L1) is 1.4 inches. As illustrated in Figure 10, L1 defines an angle of 40 degrees with respect to L2.

L3 defines an angle of 15.5 degrees with respect to L2 and aperture 156 is disposed 3.227 inches below aperture 152 as measured along L2.

The operation of the swing arm assembly 102 is illustrated in Figures 6 and 7. Figure 6 illustrates in dotted lines the positioning of the rear motorcycle wheel 122 and swing arm 102, including bell crank 140 and push/pull rod 146, as the rear wheel 122 is forced upwardly relative to the frame (not shown) when the shock absorber 106 is compressed. These same elements are shown in solid lines for level riding conditions to illustrate the relative movements of the various components when the tire encounters a significant irregularity in the road surface. Similarly, Figure 7 illustrates these same components in solid lines for normal, smooth riding conditions and in dotted lines when rear wheel 122 is extended relative to the frame (not shown) as occurs, for example, when the rear wheel raises off the roadway. The result of the multiple pivot point mountings provided by the aforesaid swing arm and shock absorber configurations is a very smooth riding motorcycle with excellent handling characteristics, a well protected rear shock absorber and a low center of gravity. By configuring the push/pull rod 146 such that it is adjustable in length, the ride height

of the motorcycle could be varied for different applications. In addition, variations in the relative positioning of the mounting apertures in the bell crank 140 allow for the fine tuning of the rear suspension system of the motorcycle for different riders and conditions.

Various changes in modifications may be made in carrying out the present invention without departing from the spirit and scope thereof. Insofar as these changes and modifications are within the purview of the appended claims, they are to be considered as part of the present invention.