EP3337717A1

EP3337717A1 - Cycle with dog-leg or parallel offset steering input drive

Info

Publication number: EP3337717A1
Application number: EP16747797.5A
Authority: EP
Inventors: Edsel Keith Helfet; Christopher John TILLBROOK
Original assignee: Individual
Current assignee: Individual
Priority date: 2015-08-19
Filing date: 2016-08-07
Publication date: 2018-06-27
Also published as: WO2017029139A1; GB2541432A; GB201514771D0

Abstract

A semi-recumbent cycle (30) with a rearwardly offset steering input control operable from a rear seat with backrest support without lean over or weight transfer upon a steerable front wheel (25), through a steering drive of a plurality of shafts with intervening rotary couplings, a steering input axis (17) being parallel to a steerable font wheel fork pivot axis (19), to preserve a traditional intuitive cycle steering and handling feel.

Description

CYCLE WITH DOG-LEG OR PARALLEL OFFSET STEERING INPUT DRIVE

This invention relates to cycles and is particularly concerned with cycle steering, frame configuration and riding stance.

The Applicants have devised a so-called 'laid-back' cycle (LBC) configuration, the subject of UK national patent application no. GB2511917, GB1400832.0 {ex GB 1301873.4} and international patent application no. WO2014/118504, PCT/GB2014/050131 {ex GB 1301873.4}.

This is generally a semi-recumbent format with a pedal 'forward' stance and a steering input control which reaches back toward a seated rider, who can steer without forward lean or weight transfer over the front forks and steerable front wheel. Unlike known recumbents and semi-recumbent formats, the pedal crank axis need not be higher than convention, but can be closer to the ground for quick return of rider's feet to the ground to stabilise the cycle.

In order to counter the pedal reaction forces, an upholstered seat with a back-rest was also used, for a more 'armchair' comfortable riding position.

An open, hollow-section, curved frame form of hydro-formed metal or composite synthetic plastics construction is convenient, for ease of side access in rider mount and de-mount. The configuration retains a traditional so-called bottom bracket or pedal crank axis height above a ground reference plane, for quick return to the ground of a rider's feet; which is a reassurance, particularly for town use.

A steering input plane orthogonal to the outstretched (fore-)arms of a seated rider is also provided. This gives a relaxed, comfortable, 'laid-back' vehicle-like steering situation. It also allows a rider comfortably to look to one side and right behind, without inadvertent, un-commanded steering input, with consequent unintended directional change, erratic forward progress and side-to-side wobble.

Some variation in the inclination of the steering input axis is admitted, but essentially still inclined to the horizontal, relying upon tandem joints to re-route the steering drive train input axis.

However, it transpires that the different steering could be un-nerving, disconcerting or unsettling and takes time for rider familiarisation. Particularly for the more mature rider, it may require 'un-learning' and 're- learning' of basic riding skills, before being able to master the new cycle format.

The unfamiliarity may put off some riders altogether and so be a disincentive, if not an outright barrier, to commercial adoption. That said, a 'niche audience' of enthusiast riders might rise and respond to the challenge and find it appealing. Younger ridders might prove more adept at learning the requisite skill. New riders would not have any earlier reference point so no pre-conceptions and nothing to un-learn.

An electric-assist variant has also been devised, with provision for battery storage, electrical control gear and wiring harness within the frame and a drive motor integrated within a wheel hub, usually at the rear. The assist power available, if not properly regulated and applied, is capable of delivering, a disconcerting surge of torque, which can unsettle a novice rider and result in unintended steering jolt with directional change and risk of tip over sideways. The more familiar orientation of the steering input in the present case can help a seated rider recognise and counter this, particularly as it is presented back to a rider braced with a back-rest.

In essence, with the benefit of experience with user trials and feedback, the Applicants now envisage a so- called 'parallel offset' or 'dog-leg steering input so-called 'laid-back' cycle (LBC) variant, still with reach-back- to-seated-rider steering, but with a re-orientated steering input plane more akin to that of familiar traditional handle bar steering. The cycle now feels more reassuring immediately 'normal ' and familiar in response to 'natural' steering input command.

This is achieved with a (parallel) offset, or 'dog-leg' steering input drive, so the steering input axis (upon which is mounted a steering input control, such as handle bars or yoke, is parallel to, but set considerably back from, a steering output axis, which is generally also the front fork pivot axis. Thus, the steering input and output axes remain parallel. Although a 'parallel axis' (steering input drive) offset is a prime example, some modest latitude in a slight departure, of say 2-5 degrees, from this might be tolerated, whilst preserving the requisite (immediate) 'normalcy' of feel.

The cycle of the present invention with offset parallel steering is more (immediately) drivable, fathomable and ridable to an untutored rider and of wider commercial appeal. This applies to both steering directional change and lateral balance using steerable front wheel inputs, for low speed manoeuvring with sharp turns. With a 'parallel offset' steering drive of the invention, a (concomitant) range of rearward and accompanying downward displacement of the steering input axis admits a variety in rearward steering disposition.

The steering is brought back to a seated rider, whose back is supported by a back-rest, by which a rider can brace the trunk against the reaction of pushing forward, rather than downward, against a pedal crank set well forward of the seat; unlike a conventional cycle configuration, but at traditional height, rather than elevated as in known recumbent or semi-recumbent cycles, for easy transposition of feet from pedals to the ground.

Unlike the Applicants' previous design the steering input axis is kept largely parallel to the steering output or front form axis, so a rider's arms manipulate the steering in a more familiar plane and easier to relate to the perceived front wheel turn immediately below and ahead of the rider.

In a particular construction, a steering transmission features tandem joints at opposite ends of a steering (drive transfer) shaft, and a steering input control, such as handle bars or yoke, at one end just beyond or outboard of a joint. The steering transmission of the invention, including a steering shaft and end couplings, is conveniently housed within a hollow front frame upright.

The rearward displacement of the steering input control can be increased or decreased, with proportionate inverse upper or lower position height change. Effectively, a steering drive transfer shaft can pivot about a forward, and in practice lower, joint; with a pivot radius of the drive shaft span. A single steering shaft would generally suffice, with joints at opposite ends; but additional shafts and couplings are feasible. Rearward steering input control displacement or offset is a prime objective, rather than the vertical position, to bring the steering input control rearward closer to and within comfortable easy reach of a seated rider, without having to lean forward.

In a steering transmission 'drive' - in the sense of directional control, rather than motive power) train with a steering shaft and universal or constant velocity coupling joints, there is a practical limit upon the angle of joint articulation tenable for the coupling joints, whilst preserving a smooth, constant or uniform rate of angular transmission and steering feel. This may be of the order of circa 30-45 degrees or so. Beyond this, there is a risk of a jerky joint action which would be undesirable for steering input. This in turn constrains the range of fore and aft (longitudinal) and up and down (upright or vertical) steering adjustment.

The range and rate of angular steering shaft movement is limited in operational use on the road (i.e. paved highway) or un-made off road trail and is not continuously unidirectional, but subject to continual modest reversal as steering is adjusted and corrected. This unlike, say, a motive power drive shaft subject to continuous fast rotation and high articulation angles in drive transfer. That said, steering is a sensitive angular control, with immediate and direct feedback to a rider through the steering input control. Moreover, directional change can be imparted by steerable wheel to road contact and disposition of a rider weight fore and aft and laterally, which in turn impact upon balance. At speed a steering input of only a few degrees can impart a marked change in direction.

Similarly, even modest frame flex can result in directional change. Open frames are particularly susceptible to flex so the Applicants have devised extraordinary deep frame profile and broad transverse section, progressive curved transitional corner transition in frame profile to counter such flex. Another consideration is feedback of road surface irregularities to a rider, which can in turn couple back through a rider's hands and arms and unsettle the steering input. A steering damper between input control and frame might counter this, at the risk of a 'duller' or less responsive steering action. A rider intervention also serves as a damper and a left-right steering action which mirrors steerable front wheel direction is more readily controlled than the Applicant's previously proposed up-down steering action, which requires some learning familiarity.

For a stationary cycle, the steering torque reflects the friction or adhesion between a steerable front wheel tyre contact patch and the ground. As the wheel starts to rotate, there is opportunity for the tyre to lift somewhat from the surface in rotation and track laterally; even slip and skid, so reducing the steering torque. It is natural to introduce some steering input as part of gaining lateral balance, so the steering load is soon reduced. Thus steering load rapidly reduces from when at rest to when under way.

Rather than an abrupt arm or hand movement, steering can be initiated more naturally when under way by lateral weight shift, such as at the hips upon turning the head. An initial counter turn can initiate a lean. At high speed a cycle has a stronger tendency to remain upright. In practice there is a continual interplay between steered wheel turn angle, frame lean and rider weight shift.

To accommodate steering shaft articulation, joints are used at opposite ends of the shaft. For this either a universal (Hooke type) or constant velocity (double cardan, swivel bearing, Rzeppa or like) joint can be used, according to the (angular acceleration with articulation angle) performance required. It is desirable that the joints have minimal or zero backlash, to preserve continuity, precision and certainty of steering feel for optimum rider directional control and balance. The steering coupling joints could be protected by flexible gaiters, particularly with an exposed drive juxtaposed with a tubular frame, as reflected in Figure 3.

For a more elaborate adjustable cycle frame variant, such as with an articulated carrier stub frame (say, as a cantilevered rearward extension or stub projection from a forward upright stem tube) for a steering input control, a user-selected steering disposition from within a range of adjustment could be provided.

Otherwise, the steering position could be pre-set and fixed in original (OEM) frame construction. A minor adjustment in steering axis orientation, consistent with a 'close' to, if not precisely, parallel (say, within 2-5 degrees) offset disposition could be admitted, without undermining a 'normal' steering feel.

An open frame configuration lends itself to a continuous arcuate curved sweeping form, from an upper rearward canted and presented steering input support stem, downward to a pedal crank axle support, then rearward and upward to a seat support stem. The forward and rearward canted frame members are splayed apart about a lower pedal crank axis at the frame junction or bottom bracket joint, to afford ample space for rider leg step-though access movement through and across the frame in mount and dismount.

In this case a hollow hydro-formed metal alloy, such as Reynolds 953 or 931 cold rolled tube), stainless steel, or moulded synthetic plastics, such as carbon fibre reinforced, composite construction can be used. This affords frame stiffness and rigidity to preserve geometry for consistent running, yet if required can allow modes of compliance or flex for rider comfort. At the front of the frame, the internal void can contain a steering transmission, including a steering shaft and opposite end couplings or universal joints. More generally, a hollow frame void can be used storage, such as battery storage, electronic power control, charger modules, wiring harness, charger lead and ad hoc cabling in an electric assist cycle variant.

A closed tubular frame of more conventional construction aside from the remote steering configuration, such as of Figure 3, could feature a lowered upper cross-tube to allow ready rider leg step-over.

Unlike a conventional upright cycle configuration, the pedal crank axis is set (well) forward of a seat support frame upright pillar, or stem, and of the order of a conventional bottom of seat pillar location, but in a so- called 'semi-recumbent' stance. This requires a rider to push forward, not simply downward as in a conventional cycle, for effective power delivery from the legs. The seat height is set above the ground by a distance of the order of the rider inside leg, so that, with legs fully extended, a rider can place toes or even feet flat on the ground while seated., perhaps with a modest frame lean to one side.

With feet upon the pedals, they are still within ready reach of the ground, while a rider remains seated, so reassuring to a rider, for stability when stationery. This encourages a rider to lean or brace the spine backward against a seat backrest, in itself an unusual provision, to counter the reaction to rider forward leg thrust upon the pedals, again reflecting the forward crank axis and pedal disposition. Thus rider weight is not relied upon to provide or contribute to a downward pedal thrust, for cycle forward propulsion, leg power

The rider seat is kept high, to promote visibility of the cycle to other traffic and bystanders and also 'look-all- round' vision for a rider, while retaining both hands on the steering input control.This steering hold contributes to cycle stability when manoeuvring. Yet a rider can still reach the ground with legs outstretched and place feed flat on the ground. The conventional height of the pedal crank axis allows ready transition of rider's feet between the pedals and the ground. Yet the pedal crank axis is well forward of the seat to promote a push forward pedal drive action, again braced by the seat backrest.

As a rider does not have to lean forward over the handlebars to place weight upon them in order to steer, there is no tendency for a rider to look down, rather than ahead or from side to side, when turning, so again contributing to rider vision and situational awareness. There may be a penalty of greater wind resistance with a more upright rider trunk, albeit countered by a less upright leg stance, but for urban use this is not a paramount consideration. Still less so for an electric assist version.

In contrast with a conventional cycle riding stance, with trunk leaning (even hunched) forward over a front wheel and steering input control, in a cycle of the invention a rider's shoulders, arms and hands no longer have to bear a proportion of rider lean-forward weight transfer, for a more relaxed, precise, light steering hold and feel, whilst preserving positive intuitive and reassuring command and control in steering and balance

For additional propulsive force, there is no need to stand upon the pedals and swing the body and/or cycle frame from side to side, through a wide lateral arc, in an extreme or exaggerated manner, in order to propel the cycle forward with greater urge or when encountering a steep incline. Such side ways frame movement tends to introduce a turning moment and couple which undermines directional stability and lateral balance. Similarly, in a cycle of the invention very low speed stability is preserved, which is not upset by sudden pedal thrust for acceleration, such as when starting from stationary; which is again advantageous for an urban cycle usage regime.

In extreme cycle activities such as 'enduro' downhill trail racing, a rider might not use the seat, but allow the frame to bounce back and forth and from side to side with only the handle bars and pedals as points or rider contact. Whilst primarily intended for relatively 'tame' urban use, the cycle proposed has some features which could be relevant, such as keeping the rider centre of gravity more central to the frame, without risk of tipping a rider forward over the handlebars, as those bars are brought back to the rider, absent a pronounced rider lean forward and so forward weight transfer. Even a minimal seat back and seat arms could provide another contact point even for an elevated rider to help discipline and confined frame movement. With upright seating and backrest, a rider upper trunk is more upright and rearwardly supported than in a traditional cycle configuration, with some beneficial easing of spinal compression and bending load, in favour of a straighter down the spine rider disposition, or more natural a slight inward lower spine curvature; with lower back braced and supported by a backrest. A rider sat upright can more readily look around by turning the head, neck, shoulders and trunk and is more likely to do so, and is more traffic aware. The rider stance is more ergonomic for the propulsion, steering and awareness task challenge.

A seated rider arms are outstretched forward and apart to a rearwardly presented steering input control, such as an elongate handlebar or yoke, with hands resting upon opposite outboard ends of the steering. With less 'loaded' arms and hands, there is better or less obstructed blood flow to the rider's hands; back and neck are also more relaxed. The overall riding position, stance and steering feel is familiar and reassuringly comfortable, as a rider can sit back and relax more while riding and being freer to look around, without making inadvertent steering input. The steering is thus effectively 'liberated' and freed from wobble tendency when loaded with rider forward weight shift along with steering turn forces. This allows steadier, straighter steering and directional control. A rider can stabilise the steering from an upright supported stance, rather than risk contributing to de-stabilisation through leaning over the steering.

Overall cycle geometry is preserved, consistent with established factors, such as so-called 'trail', for a steerable front wheel. Trail can be defined as a horizontal distance, measured at the ground contact, between a notional intersection of the steering output, or wheel pivot, axis with the ground and a vertical extension of the front wheel axis position. The slope or rake angle of the steering output axis determines the so-called castor angle of the steering. Commonly, a forward cant of the front forks brings the front wheel axis forward of the forks and also the steering output axis and in turn impacts upon the trail. A forward out-turned fork bottom end is used form similar purpose.

A front fork axis carrying a steerable front wheel is canted rearward from bottom to top by a certain rake angle and in a conventional cycle the steering input control or handle bar is mounted upon that same axis, or somewhat forward of it, by using an extension bracket. The steering input and output axes are thus offset coincident or parallel; that is with the same rake angle. For a rider, this makes steering inputs more related to steering output or steerable front wheel turn. A rider can look ahead without having to look down for directional change.

In the present invention the steering input axis is also canted rearward by the same, or a closely similar angle, for an overall parallel or close to parallel, but rearwardly displaced, offset by a significant amount to bring the steering input control in closer reach of a rearward seated rider. Again the input and output axes have the same rake angle, but are no longer coincident as in a conventional cycle. This does not preclude modest forward extension offset tubes to steering top tube handlebar mounting brackets.

The steering output or wheel pivot axis can be kept consistent with established conventional parameters and range bounds. Similarly, for a parallel, rearward displaced offset of steering input axis from the output axis, the input axis can be kept consistent with convention, but set markedly further back toward a rider. This can be expressed as a horizontal offset or displacement distance at the ground contact level or through an articulation point of a lower coupling joint in an articulated steering drive transmission. Figure 1 B reflects a geometric construction evoking this.

The steering input displacement or offset can be expressed by a combination of a (rearward) horizontal displacement and a (downward) vertical displacement. This in turn determines an articulation angle or inclination of a drive shaft between opposite end couplings in a steering transmission.

There is thus some leeway in steering input control position vertically and horizontally, subject to retaining frame support for the steering. This could feature an upper sleeve or spaced ball or roller bearing for a steering input axis and a lower (sleeve or spaced ball or roller ball) bearing for a steering output axis. In one construction of the invention, an articulation joint is located just inboard of the outer bearing pair at each end of the steering shaft. An adjustable forward cycle frame can be contrived for steering input adjustment while providing support.

Triangulation of a frame, in particular closed loop triangulation in a diamond shape has become a default configuration of an economical open sided stiff structure, derived from the original 1885/6 Starley safety bicycle format , albeit which did not feature a seat down tube to a pedal crank. With a top tube omitted, the top of the front frame has no top bracing to the top of the rear frame, so there is a vulnerability to bend and flex fore and aft about the bottom junction of the front and rear frames at the pedal crank axis and also to twist laterally under ground running and rider power transfer through a rear drive train. Thus shock loads from the front wheel, which is the first to encounter road undulations are transmitted as vibrations to the front frame, which tends to bend about the bottom bracket crank axis, and can engender a low frequency resonance. The converse applies to loads originating at the rear wheel, such as in extreme off-road trails, albeit less so with paved road use. The front down tube also takes the braking loads. To counter this, the Applicants envisage a deep, wide cross-section front and rear down tube with a flared continuous progressive transition between front stem carrying front forks, a front (diagonal) down tube around the front wheel down to the pedal crank axis and a rear (diagonal) saddle down tube around a rear wheel up to a saddle mounting stem or slide. With such generous sectional profiles and corner transitions, the necessary open format frame stiffness can be achieved in thin-walled hydro-formed aluminium alloy tube or carbon fibre reinforced hollow section.

The open format frame can emulate most, if not all, key established geometry features of a conventional diamond frame, except where departure is intended, such as in reach-back steering and forward crank axis disposition. The pedal crank axis is at a conventional height of a lower frame junction apex, but well forward of a seat longitudinal position. The pedal crank axis and pedal throw are arranged to keep the rider knee joint conveniently disposed in relation to, but not necessarily over, as in a conventional cycle, a pedal spindle and for effective leg to pedal power transfer in rotation about the pedal crank axis through a rear chain drive train.

The seat height approximates to the steering input control or handlebar height. Front head angle and rear seat angle are both of the order of 72 degrees, so front and rear frame tubes are similar to a conventional cycle. Frame considerations, in particular the front and rear frame tubes, include vertical compliance for road shock isolation. Drive transmission considerations include energy expended into forward propulsion.

For frame materials, generally aluminium is of low density and lends itself to hydro-form shaping; whereas steel is cheap and easy to work reasonable ride quality less easily shaped heavier for same shape; carbon fibre can be uncompromisingly stiff with issues on longevity in service. Overall, there is a strength, stiffness, weight compromise.

As reflected in web link <https://www.youtube.com/watch?v=Pot6W8eQcv4>, key frame geometry factors and measurement include:

fork offset or rake; the perpendicular distance from steering axis to centre of front wheel;

head angle;

· castor angle;

trail (reflects wheel diameter) is a function of steering axis angle, fork offset or rake and wheel size; trail, or effective trail, can vary as the cycle leans;

bottom bracket height (lower for stability);

steering input height and seat height impact upon front to rear weight distribution;

· the distance from seat pillar to handlebar mount impact upon steering reach issue when seated; an optional ancillary handle bar extension stem length to optimise reach;

seat tube and mounting stem angle (circa 72-74 degrees) to keep rider rearward of pedals;

but a seat slide upon a ramp of a rear upper frame extension is used with the invention;

in a conventional frame a vertical line through a rider's knee should intersect a pedal axis;

· but in a frame of the invention, the pedal crank axis is well forward of convention;

with an open frame, there is no top tube, as in conventional diamond closed frame format;

a front down tube joins the base of a steering tube or stem;

pedal axis to front wheel distance must preserve wheel clearance, particularly with wheel turned; handle bars are generally same height as the saddle;

· front wheel size dictates down tube height and pedal clearance at the outreach of crank arm length;

So-called wheel 'flop' is a steering behaviour in which a cycle tends to turn more than expected, due to the steerable front wheel flopping over when the handlebars are turned. This in turn lowers the front end of the cycle and gravity tends to cause the handlebar rotation to continue with increasing velocity, without further rider input on the handlebars. Increasing the trail and/or decreasing the head angle will increase the flop factor. As the cycle tips over laterally its c. of g. shifts and this in turn reflects steering response.

Cycle progress can be disturbed by small undulations, perturbations or upsets from road conditions, which can manifest in un-commanded directional change, with attendant weave, wobble, yaw and roll, even risk of capsize, which a rider learns to make continual small adjustment of the steering input to counter and correct.

Lightly damped oscillatory modes, such as low frequency weave at higher speeds and high frequency wobble at lower speeds, are more readily recognised and promptly countered with a parallel axis steering input control of the present invention.

Trail dictates stability and the tendency to run straight, as it creates a torque about the steering axis (which is set at a rake angle to the vertical; the less rake the quicker the rate of turn) tending to return it to straight. The greater the trail, the greater the 'front end grip' or stability and resistance to turn.

A front suspension (not used in the following example, but which might be adopted) allows the bike to dive under braking, with a change in rake. Conversely, with a rear suspension and rearward weight transfer. A rider can change the overall bike geometry according to rider stance on the bike. The position of the rider head weight can impact upon the c. of g. With a rider more likely to be seated as the steering input control is brought rearward toward a seated rider, the c.of g. is stabilised over the frame and between the wheels, making use of a compliant rear suspension cushion action, with less likelihood of longitudinal or fore and aft movement and risk of upset. There is also less risk of disturbance of the front wheel and steering.

There now follows a description of some particular embodiments of the invention, by way of example only, with reference to the accompanying diagrammatic and schematic drawings, in which:

Figure 1 A shows a side elevation of a (bi)cycle front wheel steering drive configuration, with a steering input axis displaced rearwardly from a steering output axis;

Figure 1 B shows a version of Figure 1 A with a changed more rearward and lower steering position; and additional annotation to reflect the offset within the steering input control and the relationship between the steering input axis and ground contact point a steerable front wheel whose mounting forks have a lower modest cranked end to provide 'trail';

Figure 2 shows a development of Figures 1 A and 1 B along with an overall frame and other cycle elements, including rear seat with back rest, rear wheel and trailing arm rear suspension;

Figure 3 shows an implementation of the subject remote steering for a more traditional, part-closed, tubular cross-braced frame construction, with a forward-mounted articulated steering drive shaft with end coupling joints of the invention; in this case exposed ahead of the front frame, although they might be housed in an enlarged over-sized frame upright;

Referring to the drawings, a (bi)cycle 30 with an open format frame 31 is configured with reach back steering input control 17, in this case configured as a handlebar or yoke, toward a rear seated rider.

The frame 31 has some of the principal elements and well established geometry of a classic diagonal braced frame. Straight and true running by frame alignment is necessary.

The frame 31 is of continuous cranked angular (in practice curved) form conjoins mutually splayed front and rear lower frame elements 33, 34 carrying respective front and rear wheels 21 , 41 and conjoined at a lower pedal crank axle 35, set well forward of a seat 40 carried upon a seat slide ramp 42.

A forward upper end of lower front frame 33 carries a rearwardly inclined upper frame or front stem 32, whose upper end presents a steering input control 25, of handlebars or yoke, supported at an upper end in a bearing carrier 26. of spaced ball or roller bearing sets.

A steering (drive transfer) shaft 11 is located in the frame 32 and has upper and lower drive universal joint or constant velocity joint couplings 12, 14 at opposite ends.

The rear frame member 34, which extends rearwardly and upwardly from that into a seat support slide ramp 42 to carry and adjustable rear seat with backrest.

The frame 31 follows some aspects the general frame format of the Applicants' previous GB1400832.0, but differs from a conventional closed diamond frame.

A steering input axis 17 is parallel to a front fork front wheel mounting and so steering output axis 19, respectively depicted at an angle 15, 20 to the vertical.

In this particular example, the steering is fixed in orientation and disposition, but adjustable steering support could be contrived, such as with a re-configured front frame (not shown).

The steering set up shown is to preserve a traditional steering input axis modest rearward inclination, cant or lean, (circa 72 degrees to the vertical) consistent with established cycle geometry practice and principles, but to transpose that steering input axis markedly rearward to towards a rider seat.

The steering input control, such as elongate handlebars or yoke, features an inherent modest forward mounting offset, as with conventional handlebar mounting stems with upper end forward extension tube, as referenced 26 in Figure 1 B.

The forward extension stem brings the handlebar or yoke outer end grips somewhat forward of the steering input tube, so reduces the net rearward displacement of that tube from the steering output axis.

Although not shown, consideration could be given, say by empirical trial, to the effect of a rearward, rather than forward, extension stem.

As the steering is input control is kept high with the rearward displacement, it does not impede a rider's knees or legs.

The steering drive transmission or transfer shaft is inclined rearwardly of a rider's thighs, but at a modest inclination to the vertical and about a lower joint position kept relatively high above a steerable front wheel.

The lower coupling joint 14 would be a convenient point about which to articulate the steering drive transfer shaft 11 to elevate or lower the steering input height.

Similarly, the upper joint 12 would be a convenient point about which to adjust the steering input axis 17, consistent with consistency between the input and output axes 17, 19 within certain bounds.

The individual joint articulation angle is that between the axes on each side of the joint and is kept modest to optimise joint performance, in particular of uniform angular acceleration between those axes.

For any given transfer shaft 11 orientation, the vertical displacement DV and horizontal displacement DH of the upper joint and steering input control are inter-related by the steering drive shaft length or span as a radius of rotation about either end joint. A fixed span shaft would suffice for most purposes, but an adjustable span, such as a telescopic shaft could be employed for greater range of adjustment.

The steering input control lies in a plane orthogonal to the steering input axis and so in turn to the steering output axis and thus the plane of the steerable front wheel.

From a rider's perspective viewed from above, the angular movement of the steering input control 25 is more readily apparent and intuitively related visually to the angular movement of the steerable front wheel 21 , so the overall perception of the steering action and feel is familiar and more readily fathomed and coped with.

The cycle 30 is therefore more immediately controllable and relaxing to ride and steer, given the rider is more fully supported and braced from the rear than in a conventional cycle.

Under braking, there is no rider weight transfer over the steering input control 25, so the cycle steering is not affected or de-stabilised under braking. A rider can brace backward against the steering input control 25, without imparting any steering input and so inadvertent directional change. Overall, a rider is positively located between the steering input control and the rear seat. This bolsters rider comfort and confidence; as does the ability to reach the ground with the riders feet without interference with the pedals, which are set well forward of the seat. The rider is free to look around without impacting upon steering or lateral balance.

Although a two wheel cycle or bicycle is a prime example, as steering feel, handling and lateral balance are crucial to stability, tricycle versions with twin spaced rear wheels, with the same front wheel steering can also benefit from the intuitive steering and handling feel.

The handle bar stem mounting 24 incorporates a modest forward offset 13, of the input axis 17. An extrapolation of the steering input axis 17 ti to the ground is rearward by a distance 43 of the front wheel ground contact point. A modest forward offset can be incorporated at the lower end of the front forks to bring the front wheel axle slightly forward, to create a trail or castor action.

Internalisation of the steering shaft and couplings is more readily achievable with a hollow deep cross- section frame, which also affords a stiff structure for an open frame format. Nevertheless, a visual design and utilitarian feature could be made of exposing the steering shaft and couplings, such alongside and juxtaposed with a regular tubular frame configured in the open, pedal forward configuration, as with Figure 3.

The Applicants believe that a steering drive transmission of a series of interconnected rigid drive shafts with intervening rotary couplings with minimal slack contributes to a satisfactory steering action and perceived feel, along with a parallel input and output steering drive axis. The couplings themselves are a factor in even rotational action or effect and their disposition in pairs can also cancel out any uneven drive in an individual coupling. A more elaborate constant velocity coupling can also contribute, albeit at greater expense than, say, a simpler universal or Hook joint.

Component List

11 steering shaft

12 coupling input stem offset

coupling

input axis angle

(upper) bearing

steering input axis

(lower) bearing

steering output axis

output axis angle

steerable front wheel

wheel radius

front wheel axis

front stem / steering tube

steering input control (handlebars / yoke) stem offset

front fork

vertical displacement

horizontal displacement

cycle

open format frame

seat

rear (drive) wheel

seat slide ramp

ground offset

Claims

Claims 1 .

A cycle (30) of semi-recumbent configuration

with rearward offset steering input control (25)

reaching back to and operable by a seated rider leaning upon a rear backrest

without forward lean over or weight transfer upon the steering input control or a steerable front wheel (21 ), a steering input axis (17) parallel to a steerable front wheel pivot axis (23)

to preserve a traditional intuitive cycle steering and handling feel,

an articulated steering drive of a plurality of steering shafts

intercoupled by intervening rotary joints,

between parallel front wheel pivot and steering input control axes.

2.

A cycle of Claim 1 ,

with a tandem succession of steering drive shafts and intervening rotary couplings,

such as universal or constant velocity joints (12, 14)

juxtaposed alongside or within

a hollow front frame (32) or a frame recess closable by demountable cover plate.

3.

A cycle of either preceding claim,

with a pedal crank axis (35) set well forward of a rearward seat position (42).

4.

A cycle of any preceding claim, of curvilinear open frame format,

with a flared transition between front stem, front down frame and rear seat frame.

5.

A cycle of any preceding claim, with a hollow deep cross-section frame of hydro-formed aluminium.

6.

A cycle of any preceding claim, with a hollow carbon fibre-reinforced hollow frame of synthetic plastics.

7.

A cycle of any preceding claim, with an electric motor assist, and a battery stored within a hollow frame.