A Two-Wheeled Vehicle

Technical Field

Two-wheeled vehicles are often termed 'cycles' of some sort and may be categorised as vehicles comprising a frame or chassis to which two ground-engaging wheels lying substantially in the same longitudinal plane are fitted. Typically the forward wheel determines direction, and is steered by the cycle rider with handlebars.

Forward motion requires power which is generally provided by a motor or the rider's legs, and a transmission system to drive the rear wheel. Bicycles are often fitted with gear-change devices which alter the transmission drive ratio.

A cycle will generally have a braking system, and a saddle to seat the rider in a suitable posture.

In order for a cycle to exhibit good riding characteristics, the direction control wheel must be installed in such a way as to be independent of the other wheel. This necessitates more complex wheel support and location designs than that of a wheel which is free only to rotate about its axle within a frame, as a bicycle rear wheel generally functions.

A feature of the present invention is a means of supporting and steering the steered wheel of a cycle without the requirement of forks or similar steerers.

Background Art

The traditional bicycle that exhibits a 'diamond' shaped frame and forks has been almost universally adopted as the preferred design since its inception in the late 19 ^th century. Bicycles of this type have useful properties, such as satisfactory strength, stiffness and light weight, combined with adequate rider control and comfort, but

also present a range of problems which cannot be adequately resolved with a design of this form. The aspects of traditional bicycle design which the invention is intended to improve upon are as follows.

i. A typical bicycle frame enables direction control to take place by allowing the front fork as a whole to turn relative to the cycle frame. In this design the upper ends of the fork arms are fixedly connected through a head assembly or fork crown to a rotatable steering column which is journalled to the cycle frame. Handlebars fixedly connect to the steering column; actuation of the handlebars about their only axis of freedom turns the steered wheel.

ii. Traditionally, the front wheel axle is fixedly attached at each end to drop-outs forming the fork arm ends, and the rear wheel axle is fixedly attached at each end to drop-outs which form the rear-most parts of the frame at the junction of each chainstay and seatstay frame members.

iii. The geometries of the steering mechanism positioning are chosen not only for rider comfort and avoiding interference, but also to provide a satisfactory steering response of the cycle.

iv. The steering pivot axis inclination from the vertical is known as the castor angle. The steering column is journalled within a frame member often named the head tube, at a position and at a castor angle such that the handlebars are located where the cycle rider can actuate them, and hence the direction control wheel, comfortably. By means of a raked fork, the direction control wheel hub axis is positioned longitudinally offset forward of the steering axis, thus avoiding interference between the steered wheel and parts of the frame and cycle rider.

v. The aforementioned offset combined with the castor angle determines a measurement named trail. This has a significant effect on vehicle steering response and stability. It is the distance between the steering axis intersection

with the ground plane and the steered wheel ground-contact point. The ground- contact point is located directly below the hub axis. Trail is measured in the longitudinal plane of the cycle with no angular steering input, and with the cycle positioned on a flat horizontal ground plane in an upright attitude. Generally, to provide a vehicle with satisfactory steering characteristics - that is one which tends to self-align the steered wheel to the vehicle direction when in forward motion, while still providing good sensitivity of response to steering inputs from the rider - the steering axis intersection with the ground is forward of the wheel ground-contact point. A vehicle with this steering geometry is said to have a positive trail value.

vi. Forward motion occurs when power is transmitted through a driven ground- engaging wheel, almost universally the rear wheel. A bicycle power transmission system is generally provided with foot pedals joumalled to opposed crank arms fitted at each end of an axle which is joumalled to the frame. At least one drive sprocket or 'chainwheel' is attached to a crank arm. An endless roller-chain connects the chainwheel to a driven sprocket which is mounted coaxially on the rear hub thus transmitting power to the rear wheel. A freewheel mechanism is often fitted to the driven sprocket assembly, allowing the rider to cease pedalling ('coast') whilst the vehicle is in motion.

The above aspects of traditional bicycle design result in technical deficiencies which are enumerated below.

First, the frame and fork layout results in pivot journals which are shared for both front wheel steering and handlebar rotation, which have a common axis. These journals are located within a frame member in a region above the direction control wheel. This limits steering geometry and other aspects of vehicle design. It is therefore often difficult to select a suitable cycle frame geometry which provides good rider control properties, power efficiency and comfort. This feature also

generally determines a steering ratio of 1 :1 between the handlebar angular displacement and the steered wheel angular displacement.

Second, the journals of this common pivot axis which are necessarily located above the steered wheel do not permit the castor angle, trail value or longitudinal position of the steered wheel to be specified wholly independently of the handlebar pivot axis angle and location. Additionally, such a cycle frame determines a fixed steering axis castor angle with no means of adjustment. Similarly, a raked fork provides a fixed offset between the steering and hub axes. An example of a problem caused by a fork- steered cycle would be a frame designed for a short rider; this requires handlebars positioned relatively close to the rider who will have limited reach. A frame which provides this feature also locates the front wheel closer to the rider. Problems then occur whilst pedalling the vehicle, where the feet of the rider interfere with the steered wheel at moderate steering angles. The steered wheel, would be in close proximity to the frame's down tube, which would then not provide the necessary clearance for the fitting of a mudguard. Additionally, without a front mudguard, the lower steering pivot bearing is subjected to debris and water being flung from the revolving front tyre which can reduce the life of the bearing. A second example is a frame geometry which provides a satisfactory compromise between rider ergonomics and steering response, but which causes the vehicle to become unstable when subjected to crosswinds.

Third, forks have an inherent design feature which results in the rigidity of the steered wheel installation being compromised; cycle forks reduce in structural section at an upper location where the section should be at its most substantial. Cycle forks may be viewed as a twin-armed cantilever which is rotatably mounted to the head tube of a cycle frame. In a typical cantilever-supported beam, the beam section increases to a maximum dimension at the root/fixed end of the cantilever; cycle forks do not. The cantilever root, and hence the maximum bending stress position can be viewed as the fork crown/steering tube intersection where the lower steering pivot journal seat is located. This cylindrical-sectioned cantilever root is of reduced dimensions when compared to the two upper ends of the tapered fork arms which are positioned close to

the journal seat, thus creating a stress-intensified structural weakness at the cantilever root. Forks are subjected to a variety of dynamic stresses; steered wheel braking loads are transferred into the frame via the forks and cause a rearward deflection in the fork arms; this deflection/bending strain can result in an unwanted longitudinal resonance or 'judder' within the fork structure. Furthermore, a portion of the vehicle and rider weight also applies a non-axial/bending load to the steering tube and fork arms as the steering axis is positioned on a non-vertical axis.

Ideally, a lightweight thin-walled steering tube would be specified of a sufficient diameter to ensure that the steering tube strain at the point of maximum bending stress is within the safe stress limits of the material. However, selection of a large diameter steering tube is not possible as the steering tube is housed within the head tube of the cycle frame which has a relatively small bore. Therefore a steering tube with a greater wall thickness and marginally smaller diameter is generally specified resulting in a heavier steering tube to achieve adequate strength.

Fourth, the frame similarly requires reinforcement in the region of the head tube to resolve the high stresses presented by the cantilevered fork structure. A fork-steered frame presents a relatively long and angled path along which the front wheel loads are transferred to the main frame structure.

Fifth, large steering pivot bearings are required to support the fork-mounted steered wheel, the loads being of a greater magnitude than wheel loads measured in a region close to the wheel centre.

Sixth, the steered wheel/fork/ handlebar assembly may exhibit an undesirable steering oscillation or 'shimmy' at certain vehicle speeds when certain frame geometries and rider combinations interact unfavorably. This is due in part to the steering axis passing behind the steered wheel hub axis which places unequal portions of the steerable part's masses in front of and behind the steering axis which may then induce the shimmy when the cycle is ridden. Additionally, the longitudinal offset between the

steering and hub axes can result in the aforementioned sensitivity to crosswinds, causing the vehicle to veer unexpectedly.

Seventh, the steering characteristics of a typical cycle are adversely affected by the amount of castor angle generally required to achieve an acceptable compromise between rider comfort and vehicle handling. The angled steering axis causes the front of the frame to exhibit noticeable rise and fall as the vehicle is steered.

Eighth, the wheels require removal from the frame to replace a tyre during maintenance, as the wheel axles are secured at each end.

Ninth, wheel theft is straightforward as wheels are generally secured with a quick- release lever, or standard sized hexagonal nuts fitted at each end of the axle.

Tenth, the steering lock of a typical bicycle allows a steering angle of over ninety degrees in each direction which is not necessary when riding a cycle. At ninety degrees of steering, the vehicle will remain stationary regardless of power applied to the driven wheel. At steering angles over ninety degrees, the vehicle steers in the direction opposite to the direction in which the handlebars have been steered. At steering angles close to ninety degrees it is difficult to maintain balance as the vehicle speed is necessarily very low. Therefore it is generally detrimental to vehicle control to have steering locks in the region of ninety degrees.

Additionally, the maximum steering lock of bicycles is generally reached when a part of the steered assembly contacts a part of the frame assembly. There is generally no part fitted which has been designed specifically to act as a steering angle limiter. This leads to parts such as the brake caliper, brake lever, handlebars, or the fork crown contacting the frame to act as the steering lock limiter. The maximum steering lock may also be reached when a brake or gear cable sheath is made taut at high steering angles. All of these steering lock limiting parts may be damaged whilst performing this function which they were not designed to fulfill.

Eleventh, traditional cycle frames constructed from thin tubes are not well suited to the use of composite materials such as carbon fibre in their construction, whose anisotropic properties are underutilised. Tubular cycle frames are ideally suited to isotropic materials such as metals where an efficient placement of the material to achieve a high stiffness/weight ratio is in the form of a triangulated structure composed of thin-wall tube sections.

Additionally, cycle frames of tubular construction are not well suited to the internal installation of features such as lighting embedded into the frame structure. If a thin- walled isotropic material tube section is pierced with apertures, the tube is weakened. Similarly, tube bores in cycle frames are generally too small to allow the internal fitting of energy storage devices such as batteries, electrical generators and liquid fuel tanks which may power the vehicle and/or lighting.

Twelfth, a bicycle's control cables and/or hydraulic brake lines are generally routed on the outside of the frame where they may be easily damaged and are exposed to environmental degradation. A cycle frame constructed from thin tubes is not well suited to the internal routing of cables and hydraulic lines, as the frame tube connections present an angled and obstructive route for the smooth path that control lines require. Similarly, tubular construction makes it impracticable to install electrical or fibre optic cables internally to supply a lighting system.

Thirteenth, traditional bicycles, unlike other road vehicles, do not have lighting systems installed as an integral part of the vehicle. Brackets must be fitted to the cycle for the attachment of front and rear lights, or the lights must be clamped obstructively to parts of the cycle such as handlebars. Lights also require removal from the cycle to prevent theft. Batteries are generally required and fit either within the light unit or are clamped to a frame tube as a separate unit which can be subject to theft. Alternatively, an electrical generator is fitted to the exterior of the cycle which is energised by a rotating cycle wheel.

Fourteenth, cycle frames do not shield any part of the transmission chain from contaminants; a separate shield, if available, must be fitted to protect the chain. John Kemp Starley's un-patented 'Rover' Safety Bicycle of 1885 is considered to be the original embodiment of the traditional bicycle which consists of a diamond frame with approximately equal wheel diameters, forks for steering, chain drive, and tensioned wire spoked wheels.

Patent WO0043261 discloses a single armed bicycle wheel steerer, embodying suspension, which can replace the traditional twin-armed fork to support a front bicycle wheel on one side only. The steering geometry and steering journal positioning are that of a traditional twin-armed fork. The principal elements of the single arm are two concentric telescopically connected tubes containing a spring/damper assembly which enables wheel suspension. The design permits only axial movement between the telescoping tubes. A wheel hub is journalled to an axle which is fitted to the lower telescoping tube. The upper tube is fitted with a head assembly which pivots within the frame's head tube completing the assembly.

This device could be said to be similar to a typical twin-armed telescopic suspension fork with one of the telescoping tubes omitted.

Disclosure of Invention

The invention allows a significant change in the design of cycle frames, whereby the steering pivot is repositioned from above the steered wheel to within the region of the hub of the steered wheel, and hence the frame has no requirement for a secondary pivotal frame structure such as forks. The steered wheel is 'cantilever- supported', i.e. supported on one side only by a front frame arm, which is formed so as to allow steering to take place without interference between parts of the frame and the steered wheel. This feature enables the frame to be produced as a single component with the front frame arm integrated with a middle portion of the frame which in turn is integrated with a rear frame arm.

The invention is intended to realise vehicles with vehicle control, ease of maintenance, security, illumination, structural integrity and ergonomic properties superior to those of a traditional fork-steered vehicle. The invention also aims to ameliorate certain disadvantages of traditional fork-steered cycles, or any cycles where the steering pivot journals are positioned outside the periphery of the steerable front wheel.

The invention allows more design freedom than with a traditional bicycle so that riding positions and cycle designs can be optimised for desired combinations of vehicle application, vehicle handling, aerodynamics and rider comfort. The rider's power transfer to the cycle's forward motion may also be enhanced with an increase in stiffness of vehicle parts.

A cantilever-supported wheel has advantages in both security and maintenance: the wheel does not have to be removed for tyre replacement; wheel theft may be reduced with more secure wheel attachment.

The invention allows frames of increased stiffness because the front, middle and rear frame regions are integrated. An embodiment provides further integration whereby a seat-supporting arm and a handlebar-supporting arm are both integrated into the frame. The integrated frame may permit a reduction in vehicle weight when compared to a traditional frame of similar stiffness.

An embodiment provides a frame having a front frame arm, a middle portion and a rear frame arm; a rear wheel is rotatably mounted to the rear frame arm of the frame, and a steerable front wheel is rotatably and steerably mounted to the front frame arm of the frame at a steering pivot, characterised in that: the front frame arm extends substantially to the centre of the steerable front wheel from the middle portion of the frame, such that the steering pivot is located in the region of the centre of the steerable front wheel.

An embodiment provides a frame having a front frame arm which extends substantially to the centre of the steerable front wheel in a downward direction from the middle portion of the frame, such that the steering pivot is located in the region of the centre of the steerable front wheel.

A further embodiment provides a frame having a front frame arm, a middle portion and a rear frame arm which is substantially rigid.

An embodiment provides a frame whereby the front wheel is mounted to the frame on the opposing side from the rear wheel mounting, thus providing a frame structure which is approximately balanced about the median longitudinal plane of the vehicle.

An embodiment provides a more resilient front wheel mounting; wheel support and steering loads are transferred to a forward frame arm close to the wheel centre and hence at a lower load location than in a traditional frame and fork design where the wheel support loads are transferred to the frame at the fork steering column pivot journals. This permits the steering pivot journal dimensions to be reduced when compared to fork pivot journals, enabling the pivotal hub parts to be compact and lightweight.

An embodiment provides a forward frame arm having a continuous tapering structural section forming an efficient cantilevered pivotal hub support, which is integrated with the central part of the frame.

A further embodiment provides a two-wheeled vehicle wherein the steerable front wheel is provided with a hub shell, wherein the hub shell is rotatably mounted to a hub-carrier and the hub-carrier is rotatably mounted to the front frame arm about a steering pivot axis at the steering pivot.

Another embodiment of the invention provides a two-wheeled vehicle where the steering pivot axis substantially intersects with the centre of the steerable front

wheel hub axis. This is unlike traditional frame and fork geometries where the steering axis passes behind the wheel hub axis. This enables a nearer to vertical steering axis castor angle to be specified, for a predetermined trail value. This nearer to vertical castor angle improves steering response by reducing the castor angle- induced vertical frame rise and fall caused by steering the vehicle.

Another embodiment of the invention provides a two-wheeled vehicle where the hub shell has a hub axle, wherein the hub axle engages with the hub-carrier by bearing means and wherein the hub-carrier is provided with at least one steering pin which engages with the front frame arm by bearing means. The bearing means may be located above, below or both above and below the hub axle. This freedom to choose where the bearing means are located brings advantages such as ease of removal of the hub-carrier and greater choice when specifying steering-link attachment and braking system positioning on the hub-carrier.

Another embodiment of the invention provides a two-wheeled vehicle where the hub- carrier has a hub axle, wherein the hub shell engages with the hub-carrier by bearing means and wherein the hub-carrier is provided with at least one steering pin which engages with the front frame arm by bearing means. The bearing means may be located above, below or both above and below the hub axle.

Another embodiment of the invention provides a frame incorporating offsets from the median longitudinal plane of the vehicle in order that the two wheels, each cantilever-supported, can both be positioned substantially on the longitudinal median plane of the vehicle.

A further embodiment provides a two-wheeled vehicle wherein the rear wheel is supported by a single cantilever arm that forms a part of the frame. This arm is laterally offset, to enable the rear wheel to be positioned on the median longitudinal plane of the vehicle. The rear-most section of the arm supports a joumalled wheel

hub axle and sprocket assembly on one side only. The wheel hub axle journals are positioned each side of the rear wheel drive.

Another embodiment of the invention provides a front wheel mounted to the end portion of the frame arm via a pivotal hub assembly allowing rotation about the steering axis. The hub-supporting frame arm incorporates a lateral offset to give turning clearance to the steered wheel and pivotal hub parts at all allowed steering angles, whilst permitting the steered wheel to lie substantially on the median longitudinal plane of the vehicle.

Another embodiment of the invention provides a rotating hub with a braking surface and the pivotal hub-carrier with braking means suitable for exerting pressure on the braking surface. The braking means may operate on a disc by a piston and caliper arrangement which may be hydraulically actuated, but may equally be cable-actuated or rod-actuated. The braking means may alternatively be of a brake drum and shoe type arrangement, with similar actuation means.

An embodiment provides the central region of the steered wheel with the necessary functions of vehicle steering and hub rotation, and incorporates a braking function. The internal hub location of the steered wheel's steering pivot journals and braking function provides a shield from damage and contaminants. Braking efficiency may thus be maintained by reduced water ingress.

A further embodiment provides control means suitable for steering the front wheel, comprising handlebars and connecting means connecting the handlebars to the hub- carrier.

An embodiment provides a connection point on the pivotal hub that links the steered wheel to the steering input device. The connection may be by one or more steering links which connect to steering lever arms with spherically journalled ends to minimise steering linkage hysteresis and to accommodate linkage angularity changes

during steering. The connecting means for connecting the handlebars to the hub- carrier may comprise linkage rods and levers, and/or a hydraulic link, and/or cables, and/or cardan joints and/or torque tubes.

An embodiment allows the steering ratio, and hence the mechanical advantage of the steering system to be specified above, below or equal to 1 :1 to suit a specific rider or vehicle application. The effective steering lever arm lengths may be fixed or be made adjustable to set a desired steering ratio.

An embodiment provides a steering axis intersecting with the steered wheel rotational axis. This can also reduce the detrimental rider control properties that occur when a fluctuating lateral pressure due to crosswinds acts on the steered wheel. The centre of this lateral pressure is approximately coincident with the wheel's rotational axis and thus exerts negligible steering torque on the steered parts.

In a further embodiment a two-wheeled vehicle has a frame having a front frame arm, a middle portion and a rear frame arm, wherein the frame is substantially rigid, a rear wheel rotatably mounted to the rear frame arm, and a steerable front wheel rotatably and steerably mounted to the front frame arm at a steering pivot, characterised in that: the rear frame arm is of hollow construction and encloses at least one chain sprocket, whereby the rear frame arm is provided with an upper aperture and a lower aperture through which a drive chain passes. The size, shape and location of the upper and lower apertures within the rear frame arm are specified with respect to maintaining adequate clearances between the rear frame and the chainwheel, drive chain and sprockets, regardless of the selected transmission ratio.

An embodiment has a steering pivot mechanism which requires a minimum of one resilient frame arm to support the steered wheel on one side only.

An embodiment has a rear wheel which requires a minimum of one resilient frame arm to support the rear wheel on one side only.

An embodiment of the invention provides a cantilever-supported rear wheel frame arm which may partially enclose the drive to the driven sprockets, shielding transmission components from contaminants. The form of this enclosure may also provide a frame arm with an increased structural section which can raise the stiffness of the rear part of the frame.

An embodiment provides a two-wheeled vehicle which is a bicycle. The invention also provides for vehicles which may be a motorcycle or a bicycle with a motor attached.

An embodiment of the invention provides a frame structure made principally from composite materials in the form of a monocoque whereby the frame's structural loads are supported by the frame's external 'skin'. By layering the composite's fibres directions appropriately, the frame's structural design can exploit the anisotropic properties of the material, with high strength and stiffness in one direction whilst not wasting material in another. The frame structure need be no heavier or stiffer than needed at any point. Parts of the frame, for example the cantilever-mounted seat arm, can be built to be compliant in a vertical plane for rider comfort when constructed from composite materials.

An embodiment of the invention provides a cycle frame wherein a lighting system may provide lighting directed ahead, behind and to each side of the vehicle. A frame surface is provided with apertures in which lights are embedded into the frame. The lights may be light emitting diodes, high intensity discharge lamps, or filament type bulbs powered by batteries or a generator with electrical cable routed within the frame. The lighting system may alternatively feature a light-emitting source located within the frame from which fibre optic cables are routed internally to the desired lighting locations on the frame; the frame's surface-mounted lenses would convert the fibre optic transmitted light into a suitable light beam and may be cheaply replaced if damaged; such lights would be difficult to steal.

An embodiment of the invention provides a targe volume within the monocoque frame structure which permits the internal fitting of additional components which are shielded from environmental degradation and difficult to remove by theft. These may include cyclocomputers, alarm systems and aforementioned lighting parts. Electronic radio wave transmitting and receiving equipment such as Geographic Positioning Systems (GPS) and audio/video devices may also be fitted internally to provide navigation, communication, theft alert and location notification of a stolen cycle.

An embodiment provides a means of transmission drive ratio selection that derails a chain to a different sprocket. Other ratio selection devices may include an epicyclic gear-change mechanism often known as a hub-gear, or employ a gearbox driven directly or indirectly by the cranks, which then transmits power to the rear wheels via a chain, belt or shaft drive.

The invention enables the disassociation of functions unavoidably linked in a traditional two-wheeled vehicle design. The steering input device and the steered front wheel can be positioned in locations and geometries not possible with traditional fork-steered designs, as there is no need for a rigid connection between the steering input device and the steered wheel. This permits ergonomic and vehicle response qualities not achievable with traditional fork-steered frames, where handlebars are fixed to a stem which is fixed to the forks, causing these qualities to be rigidly constrained regardless of frame geometry.

The invention allows vehicles designed to suit a particular application and rider. For example, the castor angle and longitudinal position of the direction control wheel within the frame are specified independently of the steering input device's pivot axis inclination and location.

The invention provides turning clearances which allow a range of steering angles between 0 and 45 degrees when turning to the left and 0 and 45 degrees when turning to the right.

The invention also allows the fitting of steering angle limiting stops that ensure parts of the steerable front wheel do not interfere with parts of the vehicle frame at the steering angle limits.

The invention may provide a steering mechanism whereby the castor angle is set between minus 45 degrees and plus 45 degrees, and may additionally provide adjustment means to set the castor angle to suit vehicle application rider preferences.

The invention allows vehicle designs in which the steering input device may not necessarily be handlebars but could be levers, tiller, steering wheel, joystick or suchlike. Cycle riders with limited limb mobility could use these alternative steering control input means.

The invention allows the front wheel to be steered via a control system with electric motor, and/or hydraulic and/or electro-hydraulic actuation comprising inputs from the hand, and/or the eye, and/or the brain, and/or the posterior and/or other parts of the body. These alternative means provide further scope for cycle control by riders with limited limb mobility.

The invention may provide a frame or chassis structure which encloses within the frame some or all of the steering connection parts which link the steering input device to the pivotal hub. Internal placement of movable steering parts minimizes the risk of damage to them. The enclosing of steering connection parts may provide a shield from the degrading effects of environmental exposure to water, salt and acids, thus extending steering system maintenance intervals.

The invention may reduce the aerodynamic drag of the vehicle as only a single arm, which can be suitably profiled, is required to support each wheel. Minimal externally mounted control cables and steering parts may also reduce drag and reduce potential interference between steering parts and the rider.

The invention provides for a pivotal hub assembly which may contain as a single unit the majority of the features necessary to control the steered wheel of a cycle: hub bearings permit wheel rotation, a joumalled steering swivel or king-pin device enables pivotal movement of the hub, a steering link attachment connects the steering system to the hub, and a braking system provides a braking capability. The invention provides for a steerable hub assembly which may be mounted to the cantilevered frame arm rigidly or via a suspension system.

The invention allows the steering input device a degree of compliance to reduce vibration transmitted to the rider from the surface over which the vehicle is travelling. The mounting of the steering input device can provide adjustability to suit the riding style and dimensions of the rider.

The invention provides for an alternative frame design with twin rear frame arms supporting the rear wheel on both sides, as in a traditional cycle frame design.

The invention provides a structure to support a saddle or other form of seat. The seat-supporting structure may be formed as an integral part of the frame and/or as an integral part of the seat or saddle.

The invention allows the seat-supporting structure to connect to the front, middle or rear of the frame. Freedom to choose from a range of seat support positions enables frames to be designed for different riders and applications. For example: an embodiment has a front-mounted cantilevered seat support structure which may provide a degree of aforementioned compliance for rider comfort; a frame with a centrally mounted seat support structure is suited to the fitting of a goods-carrier above the rear wheel; a rear-mounted seat support structure is suitable for a cycle where the rider can 'step-through' the frame to mount the vehicle.

The invention provides a transmission drive that may employ an endless chain, toothed belt, or a shaft drive and bevel gears. Alternative power devices may supply

power to a rear wheel by direct means, where a motor is located in the hub, or indirectly, where the motor drives a wheel via a transmission system.

The aforementioned transmission drives and motors may be partially or fully enclosed by the frame and rear frame arm.

The invention provides for motors powered by internal combustion, electrical, or hydraulic means. Fuel types may be combustibles such as petroleum, DERV, alcohol or compressed liquefied gas. Electrical energy storage/generation would be provided with batteries and/or generator and/or fuel cells. These and fuel storage parts may be partially or fully enclosed by the monocoque frame.

The cycle may be provided with a regenerative braking capability.

Additionally, small apertures within the monocoque structure made for the embedding of lights, camera lenses, cyclocomputers displays, navigation displays and electrical power/charging sockets will not significantly weaken the frame. The particular qualities of composite materials may be more fully exploited for these purposes than in a traditional frame constructed from metal tubes.

Brief Description of Drawings

Figure 1 depicts a side elevation of a cycle viewed from the left hand side of the vehicle. The Frame 100 cantilever-supports the Front Wheel 102 and Rear Wheel 103. The wheels lie approximately on the longitudinal median plane of the vehicle. The Front Frame Arm 104 is offset from the longitudinal axis of the cycle to avoid interference with the pivotal Front Wheel when the steering is actuated by the Handlebars 105. The Rear Frame Arm 106 which cantilever-supports the Rear Wheel 103 is also offset from the longitudinal axis of the cycle. Crank Arm 107 and Pedal 108 are joumaUed to the /Middle of Frame 101. A Seat Arm 109 which forms a part of the Frame 100 extends upwards and rearwards from the upper region of the Front Frame Arm 104 to locate a Seat Post 110 which supports a Saddle 111. Seat Post Bolt 112

secures the Seat Post 110 which can be height adjusted. Brake Levers 113 are fitted to each end of the Handlebars 105. Lights 115 are embedded in the frame at the front and rear of the cycle.

Figure 2 depicts a side view of a hub steering unit. Vehicle forward motion is indicated with an arrow. The steering pivot axis which passes through the centre of Upper and Lower Steering Pins 206, 207 is inclined at Castor Angle Y measured from a vertical axis. Upper and Lower Yokes 201 and 202 are shown sectioned. The Front Frame Arm 104 is not shown attached to the yokes. Hub-Carrier 203 is connected to the frame via Upper Yoke 201 and Lower Yoke 202. Upper and Lower Pivot Bearings 204 and 205 allow rotation about the upper and Lower Steering Pins 206 and 207. Axial thrust loads are taken by Upper and Lower Thrust Bearings 208 and 209. Steering Pins 206 and 207 press into the Hub-Carrier 203 with the Yokes 201 , 202 in place. The Hub-Carrier 203 locates an Inner Steering Link Bearing 210 secured by a Bolt 211. The Hub Shell 212 rotates on two bearings, of which the Outer Hub Bearing 213 is shown secured by threaded Bearing Retainer 214. Hydraulic Brake Caliper 215 forms a part of the Hub-Carrier 203. During hub assembly, the Brake Disc 216 is positioned within the Brake Caliper 215. The Hub Shell 212 and its inward facing radial Tangs 217 then locate the Disc 216 which has slots in its outer edge.

Figure 3 depicts a further side view of the hub steering unit in figure 2, fitted to a suitable cycle frame arm. Vehicle forward motion is indicated with an arrow. Steering Tube 301 protrudes from the Front Frame Arm 104 close to the hub axis. Attached to the Steering Tube 301 is the Steering Arm 302. Outer Steering Link Bearing 303 is located in the Lower Steering Arm 302 with Nut and Bolt 304,

Figure 4 depicts a part-sectioned front elevation of the hub steering unit in figure 2. From section X-X in Figure 2, the Hub-Carrier 203 is shown connected to an un- sectioned Front Frame Arm 104 with Upper and Lower Yokes 201 and 202. The Inner Hub Bearing 401 and Outer Hub Bearing 213 are fitted to the Hub-Carrier 203. The hollow Hub Axle 402 is secured within the hub-carrier assembly with the

threaded Bearing Retainer 214, and is attached to the Hub Shell 212 with Bolts 403 positioned equally on a pitched circle. The front wheel braking force is applied to the radial Tangs 217 via the Brake Disc 216. A hydraulic Brake Caliper 215 comprises Pistons 404, Seals 405, and Brake Pads 406 which are positioned each side of the Brake Disc 216. An externally threaded Sealing Plug 407 seals the hydraulic fluid cavity. Steering actuation apparatus is omitted from this view.

Figure 5 depicts an isometric view of figure 2 embodiment. Vehicle forward motion is indicated. Vehicle forward motion is indicated with an arrow. The lower portion of the Front Frame Arm 104 is shown assembled to the Hub-Carrier 203. The Hub Shell 212 is depicted without a Front Wheel 102 attached and is cut away to display the embodiment. Steering actuation is most clearly shown in this view. An angular steering input displacement causes a rotation of the Steering Tube 301 which is joumalled within the Front Frame Arm 104. The Lower Steering Arm 302 which is fixedly attached to the Steering Tube 301 connects to the Hub-Carrier 203 via Lower Steering Link 501. Inner 210 and Outer 303 spherical Steering Link Bearings form both ends of the Lower Steering Link 501. The Bearing Retainer 214 is shown securing the Outer Hub Bearing 213. An internal spline in Bearing Retainer 214 permits a securing torque to be applied to the threaded assembly with appropriate tooling. The Brake Disc 216 can be seen to pass through the hydraulic Brake Caliper 215 and in close proximity to Upper and Lower Yokes 201 and 202.

Figure 6 depicts an isometric view of a steering actuation embodiment on a cycle frame. This embodiment can connect to every hub steering device depicted. Vehicle forward motion is indicated with an arrow. The Handlebar Support Arm 608 is shown connected to the Middle of Frame 101. Handlebars 105 are fixedly connected to a Pivot Boss 601 which rotates about a Handlebar Pivot 602. Fixedly connected to the Pivot Boss 601 is the Handlebar Arm 603. The Upper Steering Link 604, fitted with spherically joumalled Upper Steering Link Bearings 605 positioned at each end, connects Handlebar Arm 603 to the Upper Steering Arm 606. Bolt and Nut fixings 607 secure the Upper Steering Link Bearings 605. The Upper Steering Arm 606 is fixedly

connected to the Steering Tube 301 which is joumalled within the Front Frame Arm 104. Rotation of the Handlebars 105 causes a rotation of the Steering Tube 301. The mechanism which translates this rotational displacement into vehicle steering is described in Figure 5 above.

Figure 7 depicts a part-sectioned front elevation of a hub steering unit. Steering actuation is similar to Embodiment 5 whereby a steering linkage would connect to the pivotal Hub Axle 701 as in Embodiment 2. The steering linkage parts are not shown in this embodiment. A similar castor angle applies to the steering axis as in figures 1 to 6, A Front Frame Arm 104 supports a pivotal Hub Axle 701 with Upper Yoke 201 and Lower Yoke 202. Upper 702 and Lower 703 Steering Pins which form the upper and lower part of the pivotal Hub Axle 701 rotate in Yokes 201 and 202. Inner Hub Bearing 704, Spacer Cone 705, and Outer Hub Bearing 706 are mounted to the pivotal Hub Axle 701 and retained with a Bolt 707 and a Washer 708. A Hub 709 mounts to the Hub Bearings 704, 706 and is retained with a Circlip 710. Spoke Holes 711 are provided in the outer flanges of the Hub 709. A braking system is not shown in this embodiment.

Figure 8 depicts a part-sectioned front elevation of a hub steering unit where the two steering pivot journals are located above the hub axis. A similar castor angle applies to the steering axis as in figures 1 to 7, Steering linkage parts which are not shown in this part-sectioned view are similar to that of Embodiment 5. A Front Frame Arm 801 houses Upper 802 and Lower 803 Steering Pivot Bearings. Pivoting within this twin- joumalled housing is the pivotal Hub-Carrier 804. Retention of the pivotal Hub-Carrier 804 within the joumalled Front Frame Arm 801 employs an Outer Ring Clip 805 securing the Lower Pivot Bearing's 803 outer journal in the bearing housing. Similarly, the Lower Steering Pivot Bearing 803 employs an Inner Ring Clip 806 to secure the inner journal to the Hub-Carrier 804. The Hub 807 is joumalled to the pivotal Hub- Carrier 804 with Outer Hub Bearing 808 and Inner Hub bearing 809. Hub Bearing Retainer 810 secures the hub bearing assembly. A Brake Disc 811 locates to the hub with radial Tangs 217. A brake caliper forms a part of the pivotal Hub-Carrier 804, but is not shown in this view.

Figure 9 depicts a part-sectioned front elevation of a hub steering unit where the two steering pivot journals are located below the hub axis. A similar castor angle applies to the steering axis as in figures 1 to 8. A pivotal hub steering connection and lower steering link and brake caliper are similar to Figure 5 and are omitted from this view. A Front Frame Arm 901 houses Upper 902 and Lower 903 Steering Pivot Bearings whose inner journals are spaced apart with conical Bearing Spacer 904. Pivoting within this twin-journalled housing is the pivotal Hub-Carrier 905. Retention of the pivotal Hub-Carrier 905 within the joumalled Front Frame Arm 901 is achieved by bolting a Stepped Washer 906 with a countersunk Screw 907 into the pivotal Hub- Carrier 905. The outer journal of the Lower Steering Pivot Bearing 903 is retained with a Threaded Cap 908. The Hub 909 is joumalled to the pivotal Hub-Carrier 905 with Outer Hub Bearing 910 and Inner Hub Bearing 911. Hub Bearing Retainer 912 secures the hub bearing assembly. Protruding from the lower end of the Front Frame Arm 901 is the lower part of the Steering Tube 913 to which is attached a Sleeve 914 which is profiled to permit rotation about the Front Frame Arm 901. Lower Steering Lever 915 is fixed to the Sleeve 914. A lower steering link similar to 501 connects the Lower Steering Lever 915 to the pivotal Hub-Carrier 905. A Brake Disc 916 locates to the hub with radial Tangs 217. A Brake caliper forms a part of the pivotal Hub-Carrier 905, and is not shown in this view.

Figure 10 depicts a rear elevation of a vertically sectioned rear hub fitted to a suitable cycle frame. An Axle 1001 is supported by a Rear Frame Arm 106 with Inner Hub Bearing 1002 and Outer Hub Bearing 1003. The Rear Frame Arm 106 houses an internally threaded bore into which an externally threaded Backing Disc 1004 fits. The outer journal of the Inner Hub Bearing 1002 is clamped securely to the Backing Disc 1004 with a Clamp Ring 1005 and Screws 1006. The inner journal of Inner Hub Bearing 1002 is fitted adjacent to Bearing Seat 1007 which abuts a shoulder on the Axle 1001 and is securely located via an internally threaded Ratchet Ring 1008 which forms a part of a freewheel mechanism. The inner journal of the Outer Hub Bearing 1003 is located on a Spigot 1009 which forms the end internal profile of the Rear Frame Arm 106. Bearing Retainer 1010 secures the inner bearing journal of Outer Hub Bearing

1003 to the Spigot 1009. The outer journal of the Outer Hub Bearing 1003 is housed in the outermost part of the Axle 1001. An internally threaded Derailleur Gear Change Boss 1011 forms a part of the Rear Frame Arm 106, and supports a derailleur type gear-change mechanism. The Axle 1001 has Spoke Holes 1012 for attaching a wheel rim to the Axle 1001 via spokes 1013. Also attached to the Axle 1001 is a Brake Disc 1014. This is retained to the Axle 1001 on Headed Pins 1015. A hydraulic Brake Caliper 1016 which forms a part of the Rear Frame Arm 106 provides a means of applying pressure to the Brake Disc 1014 via Brake Pads 1017. Pressure is applied to a fluid which acts on Pistons 1018 within two cavities sealed with Piston Seals 1019 and a threaded Cylinder Plug 1020. The freewheel device locates a pair of Ratchet Pawls 1021, Pawl Pins 1022, and Pawl Springs 1023 within the Freewheel Body 1024. These spring- loaded Ratchet Pawls 1021 ratchet about the Ratchet Ring 1008 whenever the Freewheel Body 1024 under-speeds the Axle 1001. Freewheel Bush 1025 provides a journal surface for the Freewheel Body 1024 to under-speed the Axle 1001. Chain sprockets 1026 are splined to the Freewheel Body 1024 which transmits power from a roller chain to the Axle 1001. When a torque is applied to the transmission to generate forward motion, the Freewheel Body 1024 rotates the Axle 1001, via the Ratchet Pawls 1021 engaging with the Ratchet Ring 1008. Sprocket Spacers 1027 set the Chain Sprockets 1026 apart from each other and a Sprocket Clamp 1028 secures the sprocket assembly with a Circlip 1029.

Figure 11 depicts a rear elevation of a vertically sectioned rear hub fitted to a suitable cycle frame. The hydraulic Brake Caliper 1101 bridges the outer periphery of the Brake Disc 1102. A Brake Disc Locator 1103 which locates the inner periphery of the Brake Disc 1102 forms a part of the Axle 1001.

Figure 12 depicts a rear elevation of a vertically sectioned rear hub fitted to a suitable cycle frame. A braking system is not depicted in this view. The Rear Frame Arm 1201 has a cylindrical housing which locates the outer journal of the axle Outer Hub Bearing 1202. The Axle 1203 is provided with a concentric spigot on which the inner journal of the Outer Hub Bearing 1202 is installed. The Axle 1203 is also

provided with an internally threaded section which permits secure clamping of the inner journal of Outer Hub Bearing 1202 with a threaded Bearing Retainer 1204. A Freewheeled Sprocket 1205 is mounted concentrically to the Hub Axle 1203 and secures the inner journal of Inner Hub Bearing 1206 with a threaded connection.

Figure 13 depicts a side elevation of Figure 11 embodiment viewed from the right hand side of the vehicle. Rear Frame Arm Upper Chain Aperture 1305 and Rear Frame Arm Lower Chain Aperture 1306 enable the Transmission Chain 1302 to pass through the Sprocket Shroud 1301 which forms the end of the Rear Frame Arm 106, and to engage with each of the shrouded Chain Sprockets 1026 shown in Figure 10. A typical Rear Derailleur 1303 mechanism is shown attached to the Rear Frame Arm 106. A Chainset and Crank Arm 1304 complete the typical cycle transmission system.

Figure 14 depicts a side elevation of a cycle viewed from the right hand side of the vehicle. An alternative rear frame embodies a Chain Shroud 1401. The upper run of the Transmission Chain 1302 exits a Rear Frame Arm Upper Chain Aperture 1402 in the Chain Shroud 1401 close to the Chainset 1304. The aperture is generally smaller than the Rear Frame Arm Upper Chain Aperture 1305 shown in Figure 13. The Rear Frame Arm Lower Chain Aperture 1403 is similar to Rear Frame Arm Lower Chain Aperture 1306 in Figure 13,

Best Mode for Carrying Out Invention

The frame and steering components may be made from materials such as metals, ceramics, metal matrix composites, conventional and reinforced plastics, plastics reinforced with carbon, aramid, boron or glass fibres and materials containing carbon nanotubes.