MOTORCYCLE AND POWERTRAIN

The present invention relates to an improved motorcycle structure and powertrain arrangement.

To date, seeking benefits in terms of efficiency and top speed, numerous attempts have been made to improve the aerodynamic efficiency, structure and powertrain of motorised wheeled vehicles. However, whilst significant improvements have been made in reducing the aerodynamic drag of four wheeled vehicles such as motor cars, attempts to improve the aerodynamic efficiency of motorcycles have been, to date, less successful. Aerodynamic efficiency is of particular importance for electric vehicles, where higher aerodynamic efficiency can result in significantly greater range for a given battery capacity, or a greater top speed for a given motor power output.

An early attempt to improve the aerodynamic efficiency of a motorcycle was to incorporate a partially-enclosed aerodynamic fairing on the front of a motorcycle. Such designs were common in competition motorcycles from the inter war period until the late 1950’s and included models such as the NSU Sportmax and Moto Guzzi 500 V8.

Streamlined nose fairings were successful in reducing the aerodynamic drag on a competition motorcycle and, consequently, such designs had a correspondingly higher top speed for a given engine power when compared to conventional designs. However, whilst such designs were efficient in a straight line, they presented significant and dangerous drawbacks when cornering. In essence, the aerodynamic fairing placed the centre of pressure of the motorcycle well ahead of the centre of gravity. This resulted in a strong yaw force on the motorcycle, leading to significant lateral instability during cornering or in crosswind conditions. This resulted in numerous accidents and such designs were banned from competitive motorsport in 1958.

In more recent times, aerodynamic efficiency gains in motorcycles have been modest and have resulted in the main from more efficient packaging or reduced size of the component parts of the motorcycle (e.g. transmission, engine, radiators, heat exchangers etc.) rather than dedicated aerodynamic design perse. However, tight and compact packaging can be problematic in terms of ease of access for repair and maintenance, and presents problems for efficient cooling. Therefore, to date, attempts to improve the aerodynamic efficiency of motorcycles have met with limited success. In addition, packaging arrangements and structural configuration of known motorcycles is sub-optimal to achieve improved aerodynamic and structural efficiency whilst also maintaining ease of use. It is a technical object of the present invention to address, in embodiments, these issues.

According to a first aspect of the present invention, there is provided a motorcycle comprising a vehicle body, the vehicle body comprising a lower structural portion and an upper structural portion removable from the lower structural portion, wherein the lower structural portion comprises a central frame, a front wheel assembly pivotably connected to a front portion of the central frame and a rear wheel assembly pivotably connected to a rear portion of the central frame, wherein the rear wheel assembly comprises a power unit.

In an example, there is provided a motorcycle comprising a vehicle body, the vehicle body comprising a lower structural portion and an upper structural portion removable from the lower structural portion, wherein the lower structural portion comprises a central frame, a front wheel assembly pivotably connected to a front portion of the central frame and a rear wheel assembly pivotably connected to a rear portion of the central frame, wherein the rear wheel assembly comprises a power unit and a drivetrain assembly.

In one embodiment, the rear wheel assembly further comprises a rear wheel and at least one swingarm pivotably connected to the central frame at a first end and connected to the rear wheel at a second end.

In one embodiment, the rear wheel assembly comprises a pair of swingarms pivotably connected to the central frame at respective first ends and to the rear wheel at respective second ends.

In one embodiment, the power unit is located between the pair of swingarms.

In one embodiment, the power unit is located between and adjacent the respective first ends of the swingarms.

In one embodiment, the central frame comprises a box structure. In one embodiment, the power unit is located within the rear wheel. In one embodiment, the drivetrain assembly is located within the interior of one of the swingarms. In one embodiment, the drivetrain assembly comprises a chain and sprocket assembly.

In one embodiment, the upper structural portion and the central frame are separable along a substantially horizontal plane. In one embodiment, the upper structural portion and central frame are connected by means of a connection member.

In one embodiment, the vehicle body comprises one or more fairings forming part of the external surface of the motorcycle. In one embodiment, one or more fairings are secured to the connection member. In one embodiment, the power unit comprises at least one electric motor.

In one embodiment, the front wheel assembly comprises a front wheel and at least one swingarm pivotably connected to the central frame at a first end and connected to the rear wheel at a second end.

In one embodiment, the front wheel assembly further comprises a pair of swingarms pivotably connected to the central frame at respective first ends and connects to the rear wheel at respective second ends.

In one embodiment, the front wheel assembly further comprises a further power source to drive the front wheel. In one embodiment, the front power source comprises at least one front electric motor. In one embodiment, the at least one front electric motor is located within the front wheel.

In one embodiment, the power unit comprises an electric motor. In one embodiment, the central frame further comprises a battery compartment arranged to receive at least one battery.

According to a second aspect of the present invention, there is provided a motorcycle comprising a vehicle body and a rear wheel assembly pivotably connected to the vehicle body, the rear wheel assembly comprising at least one rear wheel, at least one swingarm pivotably connected to the vehicle body at a first end and connected to the rear wheel at a second end, a power unit and a drivetrain assembly, wherein the power unit is connected to the swingarm and at least a part of the drivetrain assembly is at least partially enclosed within the swingarm.

In one embodiment, the rear wheel assembly comprises a pair of swingarms pivotably connected to the vehicle body at respective first ends and connected to the rear wheel at respective second ends. In one embodiment, the power unit is located between the swingarms. In one embodiment, the power unit is secured to both swingarms. In one embodiment, the power unit is located between and adjacent the first ends of the respective swingarm.

In one embodiment, the drivetrain assembly comprises a chain and sprocket assembly and/or a reduction gear assembly enclosed within the swingarm. In one embodiment, the drivetrain assembly further comprises an oil feed arrangement operable to lubricate the chain in use.

In one embodiment, at least a part of the drivetrain assembly is fully enclosed within the swingarm. In one embodiment, the power unit comprises an electric motor.

According to a third aspect of the present invention, there is provided a front wheel assembly for a motorcycle comprising: at least one front wheel comprising a wheel hub; at least one electric motor located within the front wheel; at least one swingarm having a first end for connection to a vehicle body and a second end connected to the at least one front wheel; and a hub-centre steering arrangement connected to the at least one front wheel to enable the at least one front wheel to be steered.

In one embodiment, a plurality of electric motors is located within the front wheel. In one embodiment, two electric motors are arranged either side of a centreline of the at least one front wheel.

In one embodiment, the hub-centre steering arrangement comprises at least one central steering bearing. In one embodiment, the at least one electric motor is located adjacent the central steering bearing. In one embodiment, the electric motors are arranged either side of the central steering bearing.

In one embodiment, the at least one electric motor has a rotor and a stator, at least a part of the rotor being connected to the at least one front wheel. In one embodiment, electrical connections for the at least one electric motor extend between the at least one swingarm and the at least one electric motor. In one embodiment, the assembly further comprising a brake disc arrangement located either side of the at least one electric motor.

In one embodiment, a cooling arrangement is provided to cool the at least one electric motor.

In one embodiment, the cooling arrangement comprises an airflow channel arranged to draw cooling air through or past at least a part of the at least one electric motor. In one embodiment, the cooling channel comprises at least one outlet located adjacent a centreline of the at least one front wheel. In one embodiment, the cooling channel comprises at least one inlet spaced from a centreline of the at least one front wheel.

According to a fourth aspect of the present invention, there is provided a motorcycle comprising at least one front wheel, at least one rear wheel and a vehicle body comprising a nose portion forming at least a part of the external surface of the vehicle body and a substantially open elongate duct extending longitudinally through a central portion of the vehicle body between at least one open inlet aperture formed in the nose fairing and at least one open outlet aperture arranged at a rear portion of the vehicle body, wherein the inlet aperture is delimited by an inlet lip formed in the nose portion, wherein at least a portion of the inlet lip has a smoothly varying curvature.

In one embodiment, there is provided a motorcycle comprising at least one front wheel, at least one rear wheel and a vehicle body comprising a nose portion forming at least a part of the external surface of the vehicle body and a substantially open elongate duct extending longitudinally through a central portion of the vehicle body between an open inlet aperture formed in the nose fairing and an open outlet aperture arranged at a rear portion of the vehicle body, wherein the inlet aperture is delimited by an inlet lip formed in the nose portion, wherein at least a portion of the inlet lip has a smoothly varying curvature.

In one embodiment, there is provided a motorcycle comprising at least one front wheel, at least one rear wheel and a vehicle body comprising a nose portion forming at least a part of the external surface of the vehicle body, wherein an open inlet aperture is formed in the nose fairing and comprises an inlet lip delimiting at least a part of the inlet aperture, wherein the inlet lip has a smoothly varying curvature and wherein the inlet aperture has a frontal cross-sectional area between 10 and 40% of the total frontal cross-sectional area of the motorcycle.

In one embodiment, there is provided a motorcycle comprising at least one front wheel, at least one rear wheel and a vehicle body comprising a nose portion forming at least a part of the external surface of the vehicle body, wherein an open inlet aperture is formed in the nose fairing and comprises an inlet lip delimiting at least a part of the inlet aperture, wherein the inlet lip has a smoothly varying curvature and wherein the inlet aperture has a width greater than In one embodiment, at least a portion of the intake lip has a radius of curvature in the range of 5 to 50 mm. In one embodiment, at least a portion of the intake lip has a radius of curvature in the range of 10 to 40 mm. In one embodiment, the open inlet aperture is located adjacent the front wheel and/or the open outlet aperture is located adjacent the rear wheel.

In one embodiment, the elongate duct extends substantially parallel to a longitudinal centreline plane of the vehicle body between the inlet and outlet apertures. In one embodiment, the longitudinal centreline plane extends through at least a part of the elongate duct.

In one embodiment, the vehicle body further comprises a seat for a rider and a power unit located between the front and rear wheels, wherein the elongate duct extends through the vehicle body between the seat and the power unit.

In one embodiment, the inlet aperture, outlet aperture and elongate duct are located and arranged to define a line of sight between at least a part of the inlet aperture and at least a part of the outlet aperture through the elongate duct.

In one embodiment, the inlet aperture, outlet aperture and elongate duct are located and arranged to define a line of sight between at least a part of the inlet aperture and at least a part of the outlet aperture through the elongate duct in a direction substantially parallel to the longitudinal centreline plane of the vehicle body.

In one embodiment, the elongate duct comprises an inlet portion adjacent the inlet aperture, a central portion and an outlet portion adjacent the outlet aperture, and wherein the central portion of the duct has a smaller cross-sectional area than the inlet aperture and/or the outlet aperture.

In one embodiment, the inlet portion of the duct tapers inwardly from the inlet aperture towards the central portion such that the cross-sectional area of the inlet portion of the duct decreases from the inlet aperture to the central portion and/or the outlet portion of the duct tapers outwardly from the central portion towards the outlet such that the cross-sectional area of the outlet portion of the duct increases from the central portion to the outlet aperture.

In one embodiment, the elongate duct has a central longitudinal axis and wherein one or more interior walls of the inlet portion and/or outlet portion of the duct are arranged at an angle to the central longitudinal axis in the range of 1 to 10 degrees. In one embodiment, the elongate duct has a venturi profile.

In one embodiment, the inlet aperture and/or the outlet aperture has a frontal cross-sectional area between 10 and 40% of the total frontal cross-sectional area of the motorcycle. In one embodiment, the inlet aperture and/or the outlet aperture has a width greater than 50% of the total width of the motorcycle body. In one embodiment, central portion has a cross-sectional area in the range of 10,000 mm ² to 90,000 mm ² . In one embodiment, the inlet aperture, outlet aperture and/or elongate duct has a substantially rectangular cross-section and/or the elongate duct comprises substantially planar surfaces.

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings, in which:

Figure 1 is a perspective view of a motorcycle according to an embodiment of the present invention;

Figure 1 a is a magnified version of Figure 1 showing the front portion of the motorcycle;

Figure 2 is a rear perspective view of the motorcycle of Figure 1 ;

Figure 3 is a front view of the motorcycle of Figure 1 ;

Figure 4 is a rear view of the motorcycle of Figure 1 ;

Figure 5 is a side view of the motorcycle of Figure 1 ;

Figure 6 is an underneath view of the motorcycle of Figure 1 ;

Figure 7 is a plan view of the motorcycle of Figure 1 ;

Figure 8 is a perspective view of the motorcycle of Figure 1 with a lower fairing removed;

Figure 9 is a side view corresponding to Figure 8;

Figure 10 is a perspective view of a lower structure of the motorcycle of Figure 1 ; Figure 11 is a perspective view of a central frame forming part of the lower structure of Figure 10;

Figure 12 is a perspective view of a front wheel arrangement forming part of the lower structure of Figure 10 shown separate from the remainder of the motorcycle of Figure 1 ;

Figure 13 is a side view of the front wheel arrangement of Figure 12;

Figure 14 is a perspective view of the lower structure similar to Figure 10 but showing control arrangements;

Figure 15 is a perspective view of a rear wheel arrangement forming part of the lower structure of Figure 10 shown separate from the remainder of the motorcycle of Figure 1 ;

Figure 16 is a further perspective view of the rear wheel arrangement of Figure 15;

Figure 17 is an underneath view of the rear wheel arrangement of Figure 15;

Figure 18 is a perspective view of the rear wheel arrangement of Figure 15 with a part of a swingarm cover removed to show the internal components;

Figure 19 is a section taken through the rear wheel arrangement of Figure 15 alone a plane perpendicular to the centreline plane X-X;

Figure 20 is a side view of the rear wheel arrangement attached to the central frame of Figure 11 ;

Figure 21 is a section taken parallel to the centreline plane X-X of the motorcycle;

Figure 22 is a perspective view similar to Figure 10 but showing the battery arrangement; Figure 23 is a perspective view of an upper body portion of the motorcycle of Figure 1 ;

Figure 24 is a side view of the upper body portion of Figure 23; Figure 25 is a front view of the upper body portion of Figure 23;

Figure 26 is a perspective view of a structural duct arrangement forming part of the upper body portion of Figure 23;

Figure 27 is a perspective view of the structural duct arrangement of Figure 26 attached to the central frame of Figure 11 ;

Figure 28 is a perspective view similar to Figure 27 showing the lower structure of Figure 10 attached to the structural duct arrangement of Figure 26;

Figure 29 is a perspective view similar to Figure 27 showing additional fairings attached;

Figure 30 is a perspective view of the upper body portion of Figure 23 attached to the central frame of Figure 11 ;

Figure 31 is a view similar to Figure 30 but showing additional fairings attached;

Figure 32 is a simplified side section view of the motorcycle of Figure 1 taken along the plane B-B of Figure 7;

Figure 33 shows simplified front and rear views of the motorcycle showing the reduced frontal area;

Figure 34 is a side section view of the motorcycle of Figure 1 taken along the plane B-B of Figure 7;

Figure 35 is a plan section view of a venturi duct taken along the plane C-C of Figure 5;

Figure 36 is a magnified and simplified view of Figure 35;

Figure 37a is a side view showing different section planes i) to iii) shown in Figures 37b to 37d;

Figures 37b to 37d show sections taken along planes i) to iii) of Figure 37a with corresponding sections of a venturi duct shown alongside; and Figures 38 to 40 show various views of a second embodiment of front wheel arrangement;

Figure 41 shows a wheel of the front wheel arrangement of Figures 38 to 40 removed from the remainder of the wheel arrangement to show a motor located therein;

Figure 42 shows a perspective section view taken through a vertical plane and showing the internal components of a front motor power source in the wheel arrangement;

Figure 43 shows a further section view in the vertical plane of the internal components of the front motor power source; and

Figure 44 shows a view similar to Figure 43 but showing cooling pathways for the front motor.

In embodiments, the motorcycle body and motorcycle is arranged to provide a significant improvement in aerodynamic drag when compared to a motorcycle of conventional design. The reduced aerodynamic drag can be utilised to provide a higher top speed for a given engine size and power output, or can be used to provide greater efficiency. These achievements are attained through a unique aerodynamic and packaging structure of the improved motorcycle described herein.

In embodiments, this improvement is achieved through a reduction in frontal area of the motorcycle. This results from the provision of a substantially unrestricted passageway through the centre of the motorcycle. This is achieved structurally through an efficient modular structure of the motorcycle and powertrain.

Throughout the description and claims, the term motorcycle is intended to be non-limiting in terms of specific vehicle configuration. In the context of the present description, the term motorcycle is intended to refer to motor vehicles which are substantially open and driven by a rider straddling the motorcycle body or sitting on a seat and which may generally have two wheels but may alternatively have three wheels (two front, one rear or one front, two rear) or four wheels (two front, two rear). If more than two wheels are provided, the paired wheels may be structurally connected by a common axle or may be fully independent. In certain arrangements, it may be necessary for the wheels to tilt with the body of the motorcycle in use.

Figures 1 to 9 show different views of a motorcycle 10 according to an embodiment of the present invention. Figures 1 to 7 show the motorcycle 10 from different views. Figures 8 and 9 shows the motorcycle 10 with a number of lower fairings removed to show internal components.

The motorcycle 10 has a body 12, a front wheel 14 and a rear wheel 16. The body 12 may be formed in different ways. For example, the body 12 may comprise a frame with fairing panels for aerodynamic/aesthetic purposes, or the body 12 may be a monocoque structure or, as described in this embodiment, may comprise a combination of these components connected together. In this embodiment, the body 12 comprises two main elements - a lower structure 18 (Figures 8 and 9) and an upper body section 20. However, whilst these elements are described separately for clarity, they need not be separate elements and may be formed as a unitary chassis, or may comprise multiple parts connected together.

The body has a longitudinal centreline plane X-X (shown in Figures 3, 4, 6 and 7). The body 12 further comprises a seat 22 for a rider and a windshield 24.

Lower body structure and powertrain arrangement

The body structure of the motorcycle 10 comprises, in this embodiment, the lower structure 18 and the upper body section 20. These main elements are separable from one another for replacement, repair or to interchange different sections. This is not possible with a conventional motorcycle design comprising a frame structure and non-structural fairings.

Figures 8 and 9 show the motorcycle 10 with part of a lower fairing removed to show the lower structure 18. The lower structure 18 comprises the necessary mechanical components (e.g. powertrain suspension etc.) for the motorcycle 10. The upper body section 20 is at least partly structural and may be formed as a monocoque, for example, from carbon fibre or may comprise a central monocoque with additional fairings. Alternatively, only a part of the upper body section 20 may be structural as described later.

This enables a modular construction of the motorcycle 10. Given the structural independence of the lower structure 18 and the body portion 20, the body portion 20 can be easily interchanged for a different structure and shape, or easily replaced in the event of damage. By providing an upper section 20 of the motorcycle 10 which extends from the front of the motorcycle 10 to the rear, ease of construction, repair and modification is possible. Further, this arrangement enables the body portion 20 to be shaped and dimensioned for optimal aerodynamic or packaging requirements without the restraints of incorporating drivetrain components.

In addition to the modularity of the lower structure 18 relative to the upper body portion 20, the motorcycle 10 has an additional modularity in terms of the lower structure 18 itself. In other words, the motorcycle 10 comprises a lower structure 18 having a modular core structure, a powertrain assembly and a steering assembly. The core structure, in this embodiment, is utilised for energy storage in the form of a battery assembly, although this is not to be taken as limiting.

This has numerous advantages. Firstly, by providing the entire powertrain assembly, including motor, swingarms and drivetrain as part of a modular rear wheel assembly/powertrain assembly, it is possible to replace, repair or swap out different powertrain combinations easily. For example, a whole rear wheel assembly could be replaced with a more powerful drivetrain or a drivetrain adapted for a different purpose (e.g. acceleration, cruising, efficiency) etc.

The lower structure 18 will now be described with reference to Figures 10 to 19. Figure 10 shows an isometric view of the lower structure 18 which comprises a central frame 26, a front wheel assembly 28 and a rear wheel assembly 30. Each of these sections of the lower structure 18 is modular.

The central frame 26 is shown in Figure 11 isolated from the remainder of the motorcycle 10. The central frame 26 has a box-like structure and comprises a front wall 32, a rear wall 34, side walls 36, 38 and a support base 40. The central frame 26 is a primary support structure on the motorcycle and is central structural component of the motorcycle 10. As will be described later with respect to Figure 13, the central frame 26 is configured and arranged to contain a battery pack. However, this need not be limiting and other components may be contained within the central frame 26.

The central frame 26 comprises connection means 42 arranged on the side walls 36, 38. The connection means 42 is operable to connect the central frame 26 to the upper body section 20 and to various fairings as will be described later.

The front wheel assembly 28 will now be described. Figures 12 and 13 show the front wheel assembly 28 separately from the remainder of the lower structure 18. The front wheel assembly 28 comprises a hub-centre steering arrangement. The front wheel 14 has a tyre 14t and is connected to the central frame 26 by a pair of front swing arms 44 which extend from connection pivots 46 on the side of the central frame 26 to a central hub 14a of the front wheel 14.

The front swing arms 44 are connected to the front wheel hub 14a by means of a rotating connection to enable the front wheel to be rotated about a plane perpendicular to the rotational axis of the wheel to enable the motorcycle 10 to be steered in use. This is known as hub-centre steering. A suspension damper 48 extends between the base 40 of the central frame 26 and a cross member 50 linking the front swingarms 44.

The use of this type of fork-less arrangement has numerous advantages. It enables a modularity to the structure of the motorcycle 10 as described above, because all the components of the front wheel assembly are located below the separation line S-S.

In order to effect steering of the motorcycle 10, handlebars 52 are provided. The handlebars 52 are connected to the front wheel assembly 28 by control cables 54. These are shown schematically in Figure 14 which shows the front wheel assembly 28 connected to the central frame 26 together with the handlebars 52 and steering linkage 54. Therefore, easy removal of the upper body section 20 can be effected easily as shown.

Further, by providing such a front wheel assembly 28, this leads to improved aerodynamic properties because the front wheel assembly 28 does not interfere with the aerodynamics of the upper body section 20. Further, the front wheel arrangement 28 comprising such a swingarm arrangement does not suffer from issues of dive, squat or stiction which can affect front fork-equipped designs. Further, the body structure can be made lighter and the steering can be isolated from braking and acceleration forces.

As described, steering is effected by means of a hub-centre arrangement. However, other arrangements could be used with the present invention; for example, pushrod steering arrangements. In some circumstances, conventional forks could be used but these are less preferred due to the poorer aerodynamic properties. However, if front forks are sufficiently and necessarily widely spaced (in, for example, a motorcycle arrangement having two spaced front wheels), then front forks may be effective. The rear wheel assembly 30 will now be described with reference to Figures 15 to 21 . Figures 15 to 18 show the modular rear wheel assembly 30 removed from the remainder of the lower structure 18. Figures 19 to 21 show the rear wheel assembly 30 attached to the central frame 26.

With reference to Figures 15 to 18, the rear wheel assembly 30 comprises the rear wheel 16 and a pair of rear swingarms 56, 58. The rear wheel 16 has a tyre 16t. The rear swingarms 56, 58 are connected to pivots 60 located on the central frame 26 and extend from the central frame 26 to either side of a rear wheel hub 16a of the rear wheel 16. A pair of dampers 62 extend from each swingarm 56, 58 respectively to the central frame 26.

The rear wheel assembly 30 is unique in that it contains all of the powertrain components therein. An electric motor 64 is located on the rear wheel assembly 30 between the swingarms 56, 58.

In other words, the electric motor 64 is connected between and supported by the rear swingarms 56, 58. The electric motor 64 is located towards respective first ends of the swingarms 56, 58 adjacent the pivots 60 connecting the rear swingarms 56, 58 to the central frame 26. The swingarms 56, 58 are shaped and arranged to shield and hold the motor 64 therebetween. The motor 64 is connected to at least one, preferably both swingarms 56, 58 by any suitable fixing means.

This arrangement has numerous advantages. First, the rear wheel assembly 30 is a modular unit with the power unit and drivetrain components all located as a single removable unit. This enables the rear wheel assembly 30 to be swapped out or replaced easily in contrast to known arrangements. A further advantage of this arrangement is that the chain length or motor- sprocket distance/orientation remains independent of the movement of the swingarms 56, 58 and suspension since all components are fixed to and/or integrated with the swingarms 56, 58.

The electric motor 64 drives the rear wheel 16 through a drive assembly 66. The drive assembly 66 will be shown and described with reference to Figures 18 to 21 . The drive assembly 66 is formed within the rear swingarm 56 and is enclosed therein. In embodiments, it is fully enclosed within the rear swingarm 56.

The drive assembly 66 is configured and arranged such that it is laterally narrow to reduce the width of the rear wheel assembly 30 and the corresponding aerodynamic drag generated thereby. This is achieved, in part, by locating the drive assembly 66 entirely within the swingarm 56 as will be described. This means that there is no need to provide lateral space for a chain to run parallel to the swingarm, and the swingarm 56 can be correspondingly closer to the rear wheel 16, reducing the total width of the rear drive assembly 30.

The drive assembly 66 is shown in in Figures 18 to 21 with an outer cover of the swingarm 56 removed for clarity. As shown, the drive assembly 66 is located entirely within an interior compartment 68 of the swingarm 56. In other words, the swingarm 56 delimits an interior chamber 68 which fully encloses the drive assembly 66. However, other arrangements may be used. For example, a cut out or window may be provided within the swingarm 56 such that at least a part of the drive assembly 66 is visible or accessible, whilst the drive assembly 66 remains within the lateral width of the swingarm 56.

The drive assembly 66 comprises a drive gear 70 connected to a drive shaft of the motor 64. The drive gear 70 drives a reduction gear 72 which in turn drives a drive sprocket 74. The rear wheel 16 has drive shaft 76 which is connected to the rear wheel hub 16a by a spline drive. A driven sprocket 78 is connected to the drive shaft 70 and held captive within the interior of the rear swingarm 52. A chain 80 connects the drive sprocket 74 and driven sprocket 78.

The chain 80 is O-ring free. In other words, the chain 80 does not comprise O-rings, which may generate drivetrain losses in use. In order to maintain the chain in a state of sufficient tension, a chain tensioner 82 is provided. However, this is not to be limiting and other arrangements may be used, for example, a chain comprising an O-ring or a drive belt.

The gear and chain arrangements of the drive assembly 66 are formed entirely within an interior compartment 68 of the swingarm 56. The interior compartment 68 is, in use, a sealed unit. This avoids external dirt and debris from entering the drive assembly 66 and prevents the chain 80 from becoming damaged or dirty.

It is useful to provide a source of lubrication for the chain 80 and sprockets 74, 78. This may be achieved by lubricating the chain 80 with an oil feed. This may, in embodiments, drop oil onto the chain 80 from a centrifugally-activated port on or adjacent the drive sprocket 74. Oil so dispensed may be collected within the interior compartment 68. A scavenger pump (not shown) may be utilised to recover the dispensed oil in a feedback loop. It is, of course, possible to utilise the interior compartment 68 as a sump for oil, with the chain 80 running through this oil. However, this is less desirable since frictional losses from running through the oil results in drivetrain losses.

The motor 64 is powered by a battery assembly 84. The battery assembly 84 is shown in Figures 22 located within a battery compartment 86 formed within the central frame 26. The battery assembly 84 and comprises a plurality of battery cells 86. A cooling assembly comprising cooling pipes 88 is also provided. However, any suitable arrangement of battery or battery storage may be provided. For example, the battery assembly 84 may not fill the entirety of the battery compartment 86 as shown and may take up a smaller portion or other components may be located therewith.

By providing a battery storage facility within the central frame 26, the relatively heavy batteries can be located centrally and low within the motorcycle 10. In addition, the central frame 26 is structural and of significant strength, providing security for the battery assembly 84.

As shown in Figures 8 to 22, the arrangement of the present embodiment enables a separation between the main powertrain, steering and suspension components and the upper body section 20. In other words, the lower structure 18 comprises all the necessary elements for operation of the motorcycle, save for the headstock/handlebars which are connected to the front wheel 14 for steering. As shown, all major drivetrain and control components form part of the lower structure 18 such that the upper body portion 20 can be removed in its entirety without affecting the lower structure 18. This is assisted by providing the motor 64 on the swingarms 56, 58 where the motor can form part of the swingarm assembly and by enclosing the drivetrain elements within a swingarm to enable modularity.

In addition, the front wheel assembly including the front wheel swingarms can be swapped for a different arrangement if desired.

Upper body structural arrangement

The structure of the upper body section 20 will now be described with reference to Figures 22 to 31 . The functionality of the components will be discussed in the next section.

The upper body section 20 forms part of the external surface of the motorcycle 10 and is at least in part structural. As described above, the entire upper body section 20 may be formed as a single monocoque in which structural loads pass through the external surfaces of the upper body section 20.

However, this need not be the case. Whilst the upper body section 20 comprises the entire upper section of the motorcycle 10, only specific elements are required to be structural. For example, the upper body section 20 may comprise a central structural unit which includes the minimum of required structural components. A non-limiting and non-exhaustive list of these components would be: the headstock, the seat 22 of the base section 18. A central structural element of the upper body portion 20 may include these elements with other areas of the upper body section 20 (e.g. the front and rear portions) may be non-structural fairing-type structures. This would allow easier replacement in the event of damage.

The upper body section 20 comprises a venturi duct 90, a nose fairing 92 and a rear fairing 94. These components may each comprise more than one unit, or may each comprise a single piece. Alternatively, these components may be unitary and comprise a single monocoque.

In this embodiment, the nose fairing 92 comprises the windshield 24 and is fitted to the front portion of the venturi duct 90. In this embodiment, the rear fairing 94 is fitted to the rear portion of the venturi duct 90.

The structural duct arrangement 90 is shown isolated from the other components in Figure 26. As shown, the structural duct arrangement 90 has a relatively flat lower section. In this embodiment, the structural duct arrangement 90 is a structural component and comprises a significant structural element of the upper body portion 20. The structural duct arrangement 90 may be formed from any suitable material, for example, carbon fibre or derivatives, aluminium or other metals, or GRP/reinforced GRP. The structural duct arrangement 90 may also be provided in different sections as required, although in this embodiment the structural duct arrangement 90 comprises a unitary piece.

In the present embodiment, as will be described, the structural duct arrangement 90 itself forms the structural core of the upper body section 20 and the other components may comprise non- structural or structural fairings as appropriate. This approach makes it straightforward to repair components in the event of crash damage or other requirements.

Figure 27 shows the connection of the upper and lower structure portions 20, 18. As shown, the central frame 26 and structural duct arrangement 90 are connected along the plane S-S. As shown, the structural duct arrangement 90 and central frame 26 are connected by means of a mounting flange plate 96. In other words, the body section 20 is connected to the lower structure 18 by means of the mounting flange plate 96. The mounting flange plate 96 lies in the separation plane S-S (shown in Figures 9 and 27). This defines the separation between upper and lower body portions along a substantially horizontal plane S-S which is perpendicular to the longitudinal centreline plane X-X.

In addition, the mounting flange plate 96 acts as a central coupling part for non-structural fairings, both on the upper body and the lower body as will be described.

Figure 28 illustrates the modular nature of the motorcycle 10 and shows the front and rear wheel assemblies 28, 30 connected to the central frame 26 whilst also connected to the structural duct arrangement 90. This illustrates the core structure of the motorcycle 10 together with powertrain and steering components.

Figure 29 corresponds to the components shown in Figure 27 but with a lower fairing attached to the mounting flange plate 96. This illustrates again the modular nature of the motorcycle 10.

Figures 30 and 31 illustrate further permutations of this. In Figure 30, the nose and rear fairings 92, 94 of the upper body section 20 are connected to the venturi and central frame 26. Figure 31 shows a lower fairing 118 added (the lower fairing will be described later).

Such modularity is impossible with a conventional motorcycle and can only be achieved through the primary separation of upper and lower structural sections with an associated coupling (in this case, the central flange plate 96).

The central flange plate 96 is not intended to be limiting and other securing arrangements and configurations may be used as appropriate, for example, additional or fewer mounting points may be provided, the mounting points may not lie in a common horizontal plane S-S perpendicular to the motorcycle longitudinal centreline X-X (e.g. the rear mounting points may be higher than the front mounting points and lie in a plane which is at an acute or obtuse angle to the centreline plane X-X). The skilled person would be aware of variations of this. Venturi duct arrangement

The aerodynamic functionality of the motorcycle 10 and structural duct arrangement 90 will now be described with reference to Figures 1 to 9 and 23 to 33.

The upper body section 20 of the motorcycle body 12 comprises a structural duct arrangement 90. This defines a venturi duct 98 therethrough. This is shown in Figures 32 to 34.

The venturi duct 98 extends continuously from the front of the motorcycle 10 through to the rear of the motorcycle 10. At a general level, the venturi duct 98 comprises a substantially unrestricted and open passageway or elongate duct extending directly through the centre of the motorcycle 10 from a front portion of the body 12 to a rear portion of the body 12. The venturi duct 98 comprises an intake 100 at a front portion 102 of the body 12 and an outlet 104 at a rear portion 106 of the body 12.

One purpose of the venturi duct 98 is to reduce the frontal area of the motorcycle 10. This is because the drag force F _d on a moving object in a fluid such as air is proportional to the frontal area of the object and the drag coefficient C _d of the object as set out in equation 1 ) below:

Where F _d is the drag force, C _d is the coefficient of drag, p is the density of air, v the velocity and A the frontal area of the object.

In general, the frontal area A of a vehicle is the orthographic projection of the vehicle on a plane perpendicular to the direction of motion. For a motorcycle under steady-state, straight- line conditions, the direction of motion D along a ground surface R will generally by coincident with the longitudinal centreline plane X-X of the motorcycle 10 and so the frontal area A of the motorcycle 10 can be considered to be the frontal area measured in a plane perpendicular to the centreline plane X-X. The longitudinal centreline plane X-X is shown in Figures 3, 4, 6 and 7.

By providing a substantially open channel through the centre of the motorcycle 10, it is possible to significantly reduce the frontal area of the motorcycle 10. Figure 32 shows a side section view of the motorcycle 10 taken a plane B-B shown in Figure 7. Figure 33 shows simplified front and rear views, similar to Figures 3 and 4 but highlighting the open area of the venturi duct 98.

As shown in Figures 32 and 34, the venturi duct 98 extends along an axis V-V which is substantially parallel to the longitudinal centreline plane X-X. In normal, straight-line motion conditions, the axis V-V is also substantially parallel to the direction of motion D of the motorcycle 10 and, therefore, substantially parallel to the direction of the oncoming airflow (assuming the absence of a crosswind).

The shaded region in Figure 32 and 33 shows schematically a substantially unobstructed and open region VA of the venturi duct 98 when viewed along the centreline plane X-X and parallel to the axis V-V. The unobstructed region VA is delimited by the narrowest section of the venturi duct 98, which is at the centre as will be described in more detail later. In other words, the region VA comprises an elongate channel or duct having a longitudinal and cross-sectional profile such that a line drawn in this region parallel to the axis V-V will not contact any portion of the motorcycle 10.

The shaded region VA is also shown in Figure 33. As shown, the region VA has a substantially trapezoidal cross-section VAc defined by the cross-sectional area of the central region of the venturi duct 98.

The cross-sectional area VAc is defined, in part, by the positional relationship between the intake 100, the venturi duct 98 and the outlet 104 with respect to the longitudinal centreline plane X-X. In other words, to minimise the frontal area A (and concomitantly maximise the cross-sectional area VAc) then the intake 100 and outlet 104 are required to be aligned in the direction of the longitudinal centreline plane X-X and the axis V-V of the venturi duct 98 is required to be parallel to the longitudinal centreline plane X-X.

In other words, in order to reduce the frontal area A of the motorcycle 10, it is required that there is a line of sight between the intake 100 and the outlet 104 through the venturi duct 98, preferably in the direction of the longitudinal centreline plane X-X. The greater the overlap between the intake 100 and the outlet 104 in the relevant plane when viewed in the relevant direction (in this case, the plane X-X), the larger the value of the cross-sectional area VAc of the unobstructed region VA and so the greater the reduction in frontal area A. It is noted that the front and rear wheels 14, 16 impinge slightly into the region VA in normal use. This is, in embodiments, arranged as a trade-off between overall size and area of the venturi duct 98, the height of the venturi duct 98 above the ground and the height of the motorcycle 10.

However, the amount by which the front and rear wheels 14, 16 impinge into the region VA will of course vary in use depending upon the loads on the front and rear wheels and movement of the wheels 14, 16 relative to the chassis in use; for example, during braking, acceleration, cornering or other situations where the suspension is under variable loads.

When considering frontal area, the orthographic projection of the frontal area in a direction of motion would of course mean that the impingement of the front and rear wheels 14, 16 would reduce the cross-sectional area VAc of the venturi duct 98 and increase the frontal area A. However, the ultimate effect of this on the total drag is more complex due to the limited projections of the wheels in certain regions of the motorcycle 10 and the effect of airflow through the venturi duct 98.

Nevertheless, this effect can be mitigated in practice through the use of streamlined fairings 14b and 16b on the front and rear wheels 14, 16 respectively. These smooth the airflow into and out of the venturi duct 98.

As shown particularly in Figure 33, the substantially open venturi duct 98 having an orthographic cross-sectional area VAc reduces the frontal area A of the motorcycle 10 considerably. In embodiments, the reduction of frontal area A may be in the region of 10 - 50%, and generally in the range of 15-40% when compared to a similar motorcycle without a venturi duct 98.

In other words, the ratio of A/(VAc+A) may typically be in the range of 0.6- 0.85. As set out in equation 1 ), this will reduce the drag force on the motorcycle 10 by a corresponding amount, before any of the further aerodynamic benefits of the shape are considered.

As set out above, by reducing the frontal area of the motorcycle 10 by an amount equal to the dimensions of the cross-section of the venturi duct 98 (for example, at the narrowest point of the venturi), the drag force F _d is correspondingly reduced. In addition, the provision of a more aerodynamically efficient shape with lower pressure build up may also have an effect on the coefficient of drag C _d . For example, the different form of the motorcycle 10 with a venturi duct 98 present may lead to reduced form drag or parasitic drag, reducing the C _d of the design. For example, the presence of the venturi duct 98 changes the central frontal shape of the motorcycle 10 from a relatively wide blunt structure to two relatively narrow, high aspect ratio side walls separated by the venturi duct 98. These side walls may have more favourable aerodynamic properties than a wide blunt nose shape as found in conventional motorcycles.

In addition to reducing the total frontal area of the motorcycle 10, the venturi duct 98 can be utilised to provide aerodynamic benefits. For example, a key region of pressure build up for a motorcycle at speed is a region of the nose of the motorcycle above the front wheel. In conventional designs, a centre of pressure above the nose and front wheel of a motorcycle can lead to significant problems in terms of front wheel lift. However, by use of a venturi duct 98, air is accelerated through the interior of the venturi duct 98, creating a region of lower pressure in the intake 100.

Indeed, the skilled person would appreciate that the aerodynamic benefits of the use of the venturi duct 98 may be advantageous even without a significant reduction in the frontal area A. This may be the case if, for example, instead of a single central intake 100 as described above, a pair of laterally or vertically offset intakes are provided. This may be necessary in cases where it is not possible to provide a central intake; for example, where legal requirements demand a headlight or other item to be located centrally.

Additionally or alternatively, a plurality of laterally or vertically offset outlets may be provided instead of a central outlet if, for example, it is necessary to provide items in the central tail region (e.g., tail lights or exhaust components). As a further alternative, a single intake and/or outlet may be provided but the intake(s) and outlet(s) are offset vertically and/or laterally with respect to one another. The venturi duct 98 may then have one or more curved sections.

As an alternative, the central region of the venturi duct may split in two or more sections if, for example, powertrain or power unit elements need to pass therethrough.

As a further alternative, there may be line of sight between the intake and the outlet through the venturi duct 98, but the venturi duct 98 may have an axis V-V which is parallel to the longitudinal centreline plane X-X but at an angle to the road surface or direction of travel. This may occur if, for example, there is a particular rake on the motorcycle 10 with respect to the ground surface.

These alternatives would not, in contrast to the example described above, minimise the total frontal area A because there would less (or no) overlap between the intake and outlet regions when viewed in the relevant plane. However, in situations where such overlap is not possible (e.g. due to packaging constraints), there may still be significant advantages to the use of a venturi duct 98.

The venturi duct 98 is made possible and practical by competing constraints on motorcycle design. Firstly, it is necessary to provide a seat for a rider at a sufficient height above the ground to enable the rider to lean into corners. If the rider is sat at too low a height, then the rider will have insufficient a moment arm to lean the motorcycle in a corner. However, this is contrary to the general desire to reduce frontal area of a motorcycle to reduce drag.

By providing a substantially open passageway through the centre of the motorcycle chassis extending longitudinally between the front and rear wheels and extending vertically between the seat 22 for the rider and the lower structure (including the power unit and energy storage, such as a battery), both of these issues can be addressed. The venturi duct 98 reduces the frontal area, whilst still maintaining the seat 22 at a height suitable to enable a rider to control the motorcycle as desired.

Figures 34 to 37 show a selection of views of the venturi duct 98 in more detail. Figure 34 shows a side section view of the motorcycle 10 taken along plane B-B of Figure 7 and Figure 35 shows a plan section taken along plane C-C shown in Figure 5. Figures 37b to 37d show sections taken through planes i) to iii) shown in Figure 37a.

As shown in Figures 34 and 35, the venturi duct 98 extends through the centre of the body 12 extending from the intake 100 to the outlet 104. The venturi duct 98 has an intake portion 108, a central portion 110 and a diffuser portion 1 12.

The central portion 110 has a smaller cross-sectional area than the intake and outlet portions 108, 112 thereby creating a venturi flow section. In other words, the cross-sectional area of the venturi duct 98 reduces from the intake 100 to the central portion 110 and then increases through the length of the diffuser portion 112 to the outlet 104. Airflow entering the intake 100 will pass through the intake portion 108 into the central portion 110 and will be accelerated due to the reducing cross-sectional area from the intake 100 to the central portion 110, before slowing in the diffuser portion 112 as the cross-sectional area increases from the central portion 110 to the outlet 104. The acceleration of the airflow into the central portion 110 creates a pressure gradient between the central portion 110 and the intake 100, which reduces the pressure at the front of the motorcycle 10 when in motion.

In embodiments, the venturi duct 98 is formed integrally with the upper body section 20 of the body 12. In other words, the upper body section 20 of body 12 is formed as a monocoque and the venturi duct 98 is defined as part of the body 12. However, other arrangements may be utilised. As described above, the upper body section 20 may comprise a central structural monocoque (which may extend from the headstock to the seat 22 and include connection points at a lower surface to connect to the mounting flange plate 96) with non-structural fairings 92, 94 at the front and rear.

For example, the parts of the upper body section 20 defining the intake portion 108 (i.e. the nose fairing 92) and/or diffuser portion 112 (i.e. the rear fairing 94) may be formed as non- structural fairings. This enables straightforward replacement in the event of damage, and allows greater freedom of materials and structures. For example, the parts of the upper body section 20 defining the intake portion 108 and/or diffuser portion 112 may be formed from transparent or translucent materials such as polycarbonate or formed from cheaper non- structural materials such as GRP.

Whilst cooling ducts and channels are well known in motorcycle design, the inventor of the present application has discovered that provision of such a large substantially open and unobstructed duct extending directly between the front and the rear of the motorcycle 10 between the front and rear wheels 14, 16 can lead to significant efficiency and aerodynamic advantages for motorcycle design, leading to improved performance.

In embodiments, the venturi duct 98 is arranged to have a minimum cross-sectional area (i.e. in the central region where the duct is narrowest) in the range of 10,000 mm ² ( 01 m ² ) to approximately 90,000 mm ² ( 09m ² ). In a specific embodiment, the smallest cross-sectional area of the duct 98 is approximately adjacent the seat (section ii) in Figure 37a) and is of the order of 65,000 mm ² . This will be described later. In addition, it is desired that the intake portion has a cone angle of between 0.5° and 10°, and a diffuser portion having a cone angle between 0.5° and 20°. By this is meant that the angle of each surface of the intake portion relative to the centreline is within this range. Therefore, the total angle between the (for example) upper and lower surfaces of the intake portion should be in the range of 0.5° to 20°. However, these dimensions and configurations are exemplary and may be varied as appropriate.

Detailed structure of venturi duct

The structure of the venturi duct 98 will now be described with reference to Figures 1 to 9 and 33 to 37.

As shown in Figure 1a, the intake 100 is delimited by the nose fairing 92 of the upper body portion 20. The intake 100 is broad and substantially trapezoidal in shape and forms a significant portion of the front region of the motorcycle 10. In this embodiment, the intake 100 is slanted forwardly so that the upper wall of the interior of the venturi duct 98 extends forwardly of the lower wall of the venturi duct 98. The walls of the venturi duct 98 are substantially flat and slab-sided.

The intake 100 is located adjacent the front wheel 14. The base of the intake 100 is located approximately level with and offset to the rear of the axis of rotation of the front wheel 14. This is shown best in Figures 1 , 1a, 3 and 5, where the lower wall of the intake portion 108 is at a lower height than the top of the front wheel 14. This arrangement allows laminar air to flow into the intake 100 whilst the turbulent air from the front wheel 14 is arranged to pass around the lower cover (described later).

As shown in Figure 3, when viewing along a longitudinal axis of the motorcycle 10, the uppermost portion of the tyre of the front wheel 14 extends slightly into the region defining the intake 100. The lower wall of the intake portion of the venturi duct 98 has a cut-out formed therein (see Figures 1 a and 15) in the region of the rearmost portion of the lower wall.

This is to provide room for the front wheel 14 to move in use; for example, to provide space for suspension travel when under braking, load or cornering, and to allow space for the front wheel 14 to turn to enable steering of the motorcycle 10. Ideally, it is desirable to isolate the intake 100 entirely from the turbulent air generated by movement of the front wheel 14 to ensure that the air entering the venturi duct 98 is as laminar as possible. The fairing/hugger structure 14b over the front wheel assists in isolating the duct 98 from the turbulent air around the front wheel 14.

However, a trade-off is necessary to achieve usability and performance. In the present embodiment, whilst the uppermost portion of the front wheel 14 impinges into the area defined by the intake 100, this enables the intake 100 to be larger and therefore reduce the frontal cross-sectional area of the motorcycle 10. Further, because of the provision of the cut-out, under front suspension load (e.g. under braking or large undulations in the road surface) the front wheel 14 may briefly impinge into the region defined by the intake 100.

However, for a large proportion of the time the motorcycle 10 is being ridden the front wheel 14 is further away from the intake 100 and the venturi 58 may be more effective.

In addition to the shape and configuration of the intake 100, the inventor of the present application has recognised that the shape of the structure surrounding the intake 100 has an impact on performance and aerodynamics.

In the described embodiment, the intake 100 is formed in the nose fairing 92 forming part of the upper body portion 20. The nose fairing 92 may be structural or non-structural as required. In this embodiment, it is non-structural and is removable from the structural duct 90

The nose fairing 92 comprises walls 114 which extend either side of the intake 100 and up towards the windscreen 24. The nose fairing 92 defines an intake lip 116 surrounding at least a part of the intake 100 and arranged between the external walls 1 14 of the nose fairing 92 and the internal walls of the duct 98.

It has been determined that the shape of the intake lip 116 can influence the aerodynamic efficiency of the motorcycle 10. It is desirable for the oncoming airflow to be guided smoothly either around the sides of the motorcycle 10 or into the venturi duct 98. If the air is forced to undergo too sharp a transition, the flow breakaway may occur, or flow pressure may oscillate between the sides of the intake 100. Both lead to reduced efficiency.

Therefore, it has been determined that a smoothly varying curvature of the intake lip 116 can improve the performance and efficiency of the motorcycle. A cross section taken along the line C-C of Figure 5 is shown in Figures 35 and 36, with Figure 36 being a simplified and magnified version of Figure 35. As shown, the intake lips 116 either side of the intake 100 curve smoothly from forwardmost points both inwards towards the interior of the duct 598 and outwards towards the walls 112 of the nose fairing 92. Note that the walls 1 14 of the nose fairing 92 curve outwards away from the intake lip 116.

The nose fairing 92 is designed to bridge the width difference between the outer portions of the wall 112 adjacent the rider’s legs in use to the interior of the duct 98. The intake lips 116 and walls 1 12 are smoothly varying to achieve this transition in a manner in which the airflow is smoothly guided into the duct 98 and around the side walls 112 of the motorcycle 10.

In embodiments, the radius of curvature of portions of the intake lip 116 may vary between 5 mm to 50 mm, and preferably between 10 mm and 40 mm.

As shown, the cross-sectional area of the central portion 110 of the venturi duct 98 is smaller than that of the intake portion 108 and diffuser portion 112 in order to create the correct acceleration of flow.

Turning to the intake portion 108, the cross-sectional area of the intake portion 108 reduces towards the central portion 110 as the intake portion 108 tapers to meet the central portion 110. The rate of taper may be varied as appropriate; for example, the rate may be constant (in the manner of a frustum or cone).

Alternatively, the rate of taper may be varied with linear distance from the intake 100, e.g. in the manner of a trumpet such that the rate of change of cross-sectional area is in some way proportional to the cross-sectional area itself. In many areas of aerodynamics, it is desirable to maintain a smooth variation in cross-sectional area to reduce drag and breakaway turbulence. However, an angle of 0.5 to 10° is desired. Further, the tapering occurs in both the lateral and vertical planes as shown in the figures.

With regard to the diffuser portion 112, as shown in Figure 34 and 35, the diffuser portion 112 flares away from the rear section of the central portion 110 to the broad outlet 104. The rate of expansion of the cross-sectional area of the diffuser portion 112 is therefore greater than that of the intake portion in the direction of the intake 100. In embodiments, the area schedules between portions of the intake portion 108, central portion 110 and diffuser portion 112 may vary. The area schedules represent the change in cross- sectional area of the duct 98 as a function of distance through the duct 98. The smallest cross- sectional area of the duct 98 is at the central portion 58.

Figures 37a to 37d show cross-sections through planes i), ii), and iii) in Figure 37a. The shape of the ducts has been isolated alongside for clarity.

In this embodiment, the areas are 71750 mm ² for the intake portion section, 65380 mm ² for the central section and 87362 mm ² for the diffuser section portion. This corresponds, in embodiments, to ratios of approximately 1 .1 :1 .0:1 .34.

However, this need not be the case and the area schedule ratio of the cross-sectional area of at least a part of the intake portion to the cross-sectional area at least a part of the central portion may be in the range of 1 .05 to 1 .2.

Concomitantly, the area schedule ratio of the cross-sectional area of at least a part of the diffuser portion to the cross-sectional area at least a part of the central portion may be in the range of 1 .5 to 1 .1 .

As shown, the airflow entering the venturi duct 98 is guided by the intake portion 108 and accelerated as the air enters into the central portion 110 of the venturi duct 98. Therefore, the pressure in the central portion 110 is considerably lower than that in the intake portion 108 due to its higher velocity.

Once the air exits the central portion 110 the diffuser portion 112 has a trapezoidal shape with sharp outward taper towards the rear of the motorcycle 10. This causes the air to expand and, consequently, slow in velocity. The reduced air velocity results in a higher air pressure.

Consequently the venturi duct 98 presents as small a restriction on the incoming airflow as possible, reducing the pressure at the front of the motorcycle 10 and therefore reducing pressure builds up with increased velocity. This, in combination with the reduced frontal area of the motorcycle 10, significantly reduces the resistance of the motorcycle 10 to forward motion, making the motorcycle 10 more efficient and faster for a given power output. In addition, the inventor has found that the outlet of the venturi duct 98 assists in further aerodynamic improvements. It is known that for a vehicle passing through a medium such as air, it is desirable to recouple the air flowing around the vehicle into a single stream behind the vehicle as efficiently as possible and with minimal turbulence.

A teardrop shape is optimal for this effect, with the extended portion of the teardrop facing rearwards. However, it has been found that this is not necessary with a venturi duct 98. Since the air flowing out of the venturi duct 98 is of much higher energy than in the corresponding region on a conventional motorcycle, it is only necessary to recouple the airflow either side of the motorcycle 10 to within the width of the venturi duct 98. This, the wide and sharply cut-off outlet behaves aerodynamically in a similar manner as if the sides of the outlet came to a smooth point. This may be used to reduce the rear overhang of the motorcycle, amongst other benefits.

Lower Fairing

Referring back to Figures 1 to 6, the motorcycle 10 comprises a lower fairing 118 arranged to cover the lower structure 18 of the motorcycle 10.

The lower fairing 118 is arranged to cover the lower structure 18 to provide environmental protection for lower components of the motorcycle 10 and to improve aerodynamic efficiency of the motorcycle 10. The lower fairing 118 comprises multiple sections although this need not be the case. The lower fairing 118 has, in general, three main functions: to ease the turbulent air created by the front wheel 14 around the remainder of the motorcycle 10, to house the central frame 26 in an aerodynamic fairing and to provide an efficient fairing to provide aerodynamic efficiency in region below the rider’s legs.

As shown best in Figures 2, 3 and 6, the lower fairing 1 18 comprises multiple fairing portions. The lower fairing 118 has a substantially curved shape which has a cross-section tapering to a point at a lowermost end of the lower fairing 118 in a vertical direction. The lower fairing 118 extends rearward from the front portion 86 to cover the motor 64 and some of the powertrain components and integrate into the rear hugger structure 16a.

Further elements may be used in and around the lower cover. For example, bargeboards or other aerodynamic devices (not shown) may be located forwardly of and adjacent the lower fairing 118 to define a narrow duct therebetween. The high flow speed of airflow through such a narrow duct may be utilised for aerodynamic benefit; for example: to mitigate boundary layer stagnation; to reduce form drag by reducing turbulent wake downstream of the front portion 86 of the lower cover; and to guide airflow around the rider’s legs.

In addition, if an ICE engine is provided in contrast to the present electric drive, it is necessary to provide an inlet aperture to an air box of the ICE. The engine inlet aperture may be located in any suitable location; for example, formed in a lower wall of the venturi duct 98, or located between the intake 100 and the lower fairing 118. The location may be arranged in a region of higher pressure such that the intake pressure into the ICE is increased, providing an increase in induction pressure.

As shown, the venturi outlet 104 is located at the rear of the motorcycle adjacent the rear wheel 16. The venturi outlet 104 is delimited by a rear portion of the duct body 20 which forms the diffuser portion 112 of the venturi duct 98. The diffuser portion 112 forms a trapezoidal cone expanding outwardly towards the rear of the motorcycle 10 in the region adjacent and rearward of the seat 22.

However, whilst the outlet 104 is shown as having a substantially trapezoidal cross-section, this need not be the case and any suitable shape may be used; for example, the outlet 104 and/or diffuser portion 112 may take any suitable cross-sectional shape such as circular, ovoid or rectangular.

Turning to the diffuser portion 112 in more detail (Figure 2), the diffuser portion 112 comprises an upper wall, a lower wall and sidewalls. As shown in Figure 2, a portion of the rear wheel 16 extends into the space defined by the diffuser portion 112. In addition, the rear wheel 16 extends into the outlet 104 itself. In embodiments, the rear wheel 16 rotates within a cut out 102 formed in the lower wall 60 and comprises the wheel hugger fairing 16b.

However, the arrangement need not be as shown. The skilled person would readily understand that variations could be made which would fall within the scope of the present disclosure. For example, the rear wheel 16 need not project into the diffuser portion 112 of the venturi duct 98 and maybe separated there from, for example by the lower wall 98. Alternative front wheel arrangement

A second embodiment showing an alternative front wheel assembly will now be described with reference to Figures 38 to 42. The alternative front wheel assembly is suitable for use with the motorcycle 10 and may be used in place of the first embodiment of the front wheel assembly 28. For clarity, where necessary, features of the motorcycle 10 will be referred to with the same reference numerals as used in the examples above.

Figures 38 to 44 show a front wheel assembly 200 according to a second embodiment. The front wheel assembly 200 is shown separately from the remainder of the lower structure 18 of the motorcycle 10.

As for the first embodiment, the front wheel assembly 200 comprises a hub-centre steering arrangement as generally described above. However, in this embodiment an electric motor arrangement comprising two electric motors 202 is provided on the front wheel assembly 200. The provision of electric motors 202 driving the front wheel 204 of the motorcycle 10 provides a number of benefits.

First, in combination with an electric motor or motors driving the rear wheels, this provides all wheel drive for the motorcycle 10. This has advantages in terms of power delivery and traction.

Secondly, the location of the motors 202 on the front wheel 204 also provides the opportunity for energy recovery (or regeneration) via the front wheel motors 202 under braking or off acceleration. This is not generally efficient or practical through a rear wheel electric motor because under deceleration conditions the rear wheel is only lightly loaded and so efficient regeneration is difficult.

The front wheel arrangement 200 will be described below with reference to Figures 38 to 44. The front wheel 204 has a front tyre 204t and is connected to the central frame 26 by a pair of front swing arms 44 which extend from connection pivots 46 (Figure 14) on the side of the central frame 26 to a central hub 206 of the front wheel 204.

The front swing arms 44 are connected to the front wheel hub 206 by means of a rotating connection to enable the front wheel 204 to be rotated about an axis R-R (Figures 40 and 42) perpendicular to the rotational axis of the wheel to enable the motorcycle 10 to be steered in use. This is known as hub-centre steering and is described in detail below for the second embodiment of the front wheel arrangement 200. A suspension damper 48 extends between the base 40 of the central frame 26 and a cross member 50 linking the front swingarms 44.

As described above the use of this type of fork-less arrangement has numerous advantages. It enables a modularity to the structure of the motorcycle 10 as described above, because all the components of the front wheel assembly are located below the separation line S-S. In addition, the arrangement provides further benefits when used with a front electric motor drive as described below.

In order to effect steering of the motorcycle 10, handlebars 52 (see Figure 14) are provided. The handlebars 52 are connected to the front wheel assembly 200 by control cables 54. As described for the first embodiment shown in Figure 14, by providing such a front wheel assembly 200, this leads to improved aerodynamic properties because the front wheel assembly 200 does not interfere with the aerodynamics of the upper body section 20.

Further, the front wheel arrangement 200 comprising such a swingarm arrangement does not suffer from issues of dive, squat or stiction which can affect front fork-equipped designs. Furthermore, the body structure can be made lighter and the steering can be isolated from braking and acceleration forces.

As shown in Figures 38 to 44, first and second motors 202 are provided in the front wheel arrangement 200. The motors 202 are located centrally within the hub 206 of the front wheel 204 and are integrated thereto.

Figures 41 to 44 show the integration of the motors 202 into the hub 206 in more detail. As shown in Figure 41 , the motors 202 are integrated into the centre of the wheel hub 206. A brake disc assembly 208 is located outwardly of the motors 202 and wheel hub 206.

For convenience the parts of each motor 202 are referenced with the same reference numerals. With reference to Figures 42 and 43, each motor 202 comprises a stator 202a and a rotor 202b. The stator 202a further comprises control electronics and coils 202c which are arranged in a fixed relationship to the stator 202a.

The stator 202a is connected to the non-rotating parts of the wheel assembly 200, comprising inter alia a central bearing carrier 210, the brake disc assembly 208 and swing arms 44, by means of a stator retaining ring 212 and stator mount 214. The central bearing carrier 210 comprises a plurality of pivot bearings 216 which enables the wheel assembly to rotate about a steering axis R-R which is substantially perpendicular to the axis of rotation of the front wheel 204. As described above, steering is effected by means of a hub-centre arrangement which actuates the steering of the front wheel about the axis R-R of the pivot bearing 216. As shown, the pivot bearings 216 of the hub-centre steering arrangement are located between the motors 202. In other words, the motors 202 are located either side of the steering axis R-R.

Whilst the stator 202a of each motor 202 is fixed to the non-rotating parts of the front wheel assembly 200, the rotor 202b of each motor 202 is connected to the rotating wheel hub 206 and wheel 204 as shown in Figures 42 and 43. The rotors 202b are connected to the wheel hub 206 by means of wheel mount rings 218. The rotors 202b and hub 206 rotate on wheel bearings 220 which are connected to the central bearing carrier 210.

The motors 202 may be connected to a power source (such as battery assembly 84) via suitable electrical connections (not shown). The electrical connections may comprise connections which extend from the motors 202 to the swingarms 44 and may extend internally of the swingarms. Alternatively, the wires may be carried externally or within fairings.

By providing such an arrangement, the motors 202 can be seamlessly integrated into front wheel 14 of the motorcycle 10 to provide additional power delivery or regeneration without an increase in drag or frontal area of the motorcycle 10.

Cooling of the motors 202 is important to ensure robust operation. Figure 44 shows the cooling for the motors 202. A cooling airflow (shown by the dashed white arrows in Figure 44) is drawn into the wheel hub from adjacent the brake disc assembly 208 through a cooling arrangement 222 and through each motor 200 between the wheel hub 206 and stator 202a (flow F1 ), between the stator 202a and rotor 202b (flow F2) and/or between the rotor 202b and wheel hub 206 (flow F3), and along a guide member 224 forming part of the cooling arrangement on the wheel 204 adjacent the wheel hub 206. The guide member 224 is shaped and arranged to guide airflow out into a region adjacent a centreline of the wheel hub 206.

The guide member 224 is located between the motors 202 and defines one or more plenum chambers for each or both motor 202 and is arranged to extract cooling airflow therefrom. The guide member 224 may take any suitable form and may be an integral part of the wheel 204 and/or hub 206 or may be a separate part. If a separate part, this can be designed for optimal airflow extraction for the design of motor used.

The cooling arrangement 222 may further comprise one or more inlets (not shown) for drawing cooling air in past the motor(s) 202. The inlets may be shared by the brake discs or may be separate. A fairing (not shown) for the cooling arrangement may further be utilised to guide and/or shield electrical connections to the motors 202.

By providing such an arrangement, numerous advantages are presented. For example, the combination of hub-centre steering and an in-wheel front motor confers numerous benefits not found in the known art. For example, a significant issue with high power hub electric motors is that power cables of significant diameter are required. Given the suspension travel and steering necessary in a functioning motorcycle, cable arrangements are often problematic in front fork- based arrangements.

However, hub-centre steering allows cabling to be considerably better packaged since the non moving parts of the front wheel arrangement 200 are much closer to the motors 202 so the distance any cabling has to move by when suspension is under load or under steering movement is considerably less than known arrangements. Further, the advantages described above of the modular chassis construction are particularly useful for the front wheel arrangement 200 which can be swapped easily for a different motor configuration, for example.

Various additions or alternatives are possible within the scope of the present disclosure. For example, whilst the particular shapes of the sections of the venturi duct 98 have been described herein, it is to be understood that these are purely exemplary and alternatives may well be used.

Whilst most of the venturi duct 98 surfaces are shown as substantially planar (resulting in a substantially trapezoidal cross-section of the venturi duct), this need not be the case. For example, the cross-section of the venturi duct may be circular, elliptical or any other suitable shape as best to maximise the reduction in frontal area whilst also conforming to the desired shape of body 12 of the motorcycle 10.

Whilst embodiments have been illustrated with respect to two swingarms both front and rear, again this need not be the case and only a single swing arm may be provided. Whilst the above examples have described a single rear motor and two front motors, this need not be the case. Any number of front or rear motors may be provided. For example, a single front motor may replace the motors 202 described above, and two or more motors may replace the rear motor described above. Variations will be apparent to the skilled person. Whilst the above examples have been described with reference to a rear motor spaced from the rear wheel(s), this need not be so. One or more rear in-wheel electric motor may also be provided either with or without a drivetrain assembly. If without this may be a direct drive. In wheel motors may have certain advantages in terms of packaging although such a configuration may impose limitations on the size and power available for such motors.

Embodiments of the present invention have been described with particular reference to the examples illustrated. While specific examples are shown in the drawings and are herein described in detail, it should be understood, however, that the drawings and detailed description are not intended to limit the invention to the particular form disclosed. It will be appreciated that variations and modifications may be made to the examples described within the scope of the present invention.