GB2300163A - Human powered four wheel vehicle with clutched chain drive, pivotable chassis, drum brakes, and optional remote steering - Google Patents

Abstract

Chassis 10 comprises front and rear sections 12, 14, each carrying two road wheels. The sections are connected so that they can pivot with respect to each other about a longitudinal axis. Suitably, elastomeric members connect the two chassis sections. The vehicle has a handle which may be connected to its steering mechanism, by which the vehicle can be led by a user on foot. Drum brakes are used, whose shoes and other components can float relative to a fixed backplate, so as to ensure that the shoes act equally on the drum. The chain drive has a clutch, preferably a dog clutch, to allow gears to be changed down while the vehicle is stationary. Numerals 34 represent leg guards for the rider. The vehicle is intended for carriage of goods, with interchangeable bodies which may be fitted to the chassis.

Description

LAND VEHICLE The present invention relates to a land vehicle intended to be propelled entirely or principally by human power.

At the present time, there is an increasing belief that reliance upon motor vehicles must be reduced, most particularly in urban areas where pollution from vehicles can become a health hazard. While public transport can provide an alternative to private vehicles in some cases, personal transport continues to be essential for some journeys.

Bicycles can be used where just a person or a person and a small amount of light luggage are to be transported. However, they are not generally suitable for carrying large or heavy loads. Bicycles can be equipped with trailers, but these are cumbersome, difficult to ride and prove awkward when the bicycle is to be left unattended since steps must be taken to prevent the bicycle from falling over and possibly upsetting the trailer.

There is a need, which this invention is aimed at fulfilling, for a human powered land vehicle which is practical and convenient in use and which can be used to carry a payload safely. Additionally, it is an aim of the present invention to provide improvements relating to various aspects of human powered vehicles.

In a first of its aspects, the invention provides a land vehicle comprising (a) a chassis frame having forward and rear frame components, each carrying a pair of road wheels, those of the forward frame component being rotatable for steering movement, the frame components being relatively movable in rotation about an axis approximately aligned with straight ahead movement of the vehicle; (b) a seat carried on the frame;; (c) steering means by which the road wheels of the forward frame component can be controlled by a user for steering movement using first handle means operable by a user riding the vehicle and second handle means operable by a user standing adjacent the vehicle, the second handle means having a first condition in which it is disconnected such that movement of it does not cause steering movement and a second condition in which it can be operated to cause steering movement; and (d) drive means by which a user can propel the vehicle through transmission of drive to the road wheels of the rear frame component, comprising a multi-speed derailleur chain drive, and clutch means by which the drive means can be disconnected from the road wheels such that the chain can be moved for operation of the derailleur mechanism when the vehicle is stationary.

The vehicle thus provided has been found to have practical value as a road vehicle.

Utility of the vehicle can be increased by provision of load carrying means, such as a box-like container, mounted on the chassis frame. More preferably, the load carrying means is arranged to be demountable and to be interchangeable with one of an alternative configuration suited to a load to be carried.

From a second aspect, the invention provides a chassis frame for a wheeled land vehicle comprising a forward frame component having means for carrying a pair of road wheels for rotation and steering movement, and a rear frame component having means for carrying a pair of road wheels for rotation, the forward and rear frame components being interconnected so as to permit limited twisting movement therebetween about an axis extending approximately in a direction of straight ahead movement of the vehicle.

This frame can be used in the construction of a vehicle to enhance significantly the performance of the vehicle on uneven surfaces as compared to a vehicle equipped with a rigid chassis, without the need to adopt a costly and heavy spring suspension system. It has been found, for example, that a vehicle so equipped can climb a kerb without undue difficulty.

Preferably, the chassis is further equipped with movement restricting means to resist or eliminate relative movement of the frame components along the longitudinal axis, at least in one direction.

The frame components are preferably interconnected at two or more locations spaced apart along the longitudinal axis. This arrangement inhibits relative movement of the frame components that could interfere with steering of the vehicle.

Interconnection between the frame components is preferably arranged to bias their relative positions towards a median position in which the respective axes interconnecting the pairs of wheels are parallel (that is, the relative positions that the frame components would adopt when equipped with wheels and when standing on a flat surface).

Interconnection may suitably be achieved through one or more metal and elastomer composite bushes.

The rear frame component preferably has mounting means on which can be carried load carrying means, such as a box-like or hopper-like container. The mounting means may be adapted to permit readily interchangeability of the load carrying means to allow the vehicle to be adapted to a particular load-carrying task.

As is well known, a derailleur mechanism can be used to provide a highly efficient change speed mechanism for a chain drive. However, a major shortcoming of such a mechanism is that it cannot effect a gear change unless the chain is being driven as by pedalling. This is a minor inconvenience in a normal bicycle where it is generally possible, if it is absolutely necessary to change gear, to lift the bicycle to allow the rear wheel to turn. However, in the case of a heavily-loaded vehicle this may not be practicable, and it may be virtually impossible to restart such a vehicle if it is inadvertently stopped in a high gear. It is a further aim of the present invention to overcome this disadvantage with minimal compromise to the efficiency of the derailleur mechanism.

In a third of its aspects, the invention provides a multi-speed chain drive comprising a chain, a multi-speed cluster of chain wheels and a derailleur mechanism whereby the chain can be caused to transmit drive to or can be caused to be driven from a selected one of the cluster of chain wheels, in which there is provided a clutch selectively operable to permit free movement of the chain without causing consequent movement of a device driven by the chain drive.

For normal operation, the clutch will connect drive to a device (such as the driven wheel or wheels of a vehicle). However, the clutch can disconnect drive so as to allow the chain and cluster to move freely so permitting gear changes to be made, even when the driven device itself is immobile.

The clutch is preferably a dog type clutch which is either fully engaged or fully disengaged with no intermediate slipping state.

In one particularly preferred embodiment, the clutch may comprise an elongate arm carrying drive connecting means at a first end portion and being fixed to a support at a second end portion, connection and disconnection of drive being effected by resilient deflection of the arm to cause movement of the drive connecting means into and out of engagement with driven means. Most preferably, drive is transmitted through the clutch when the arm is in an undeflected state, operating means being provided to deflect the arm when drive is to be disconnected. The operating means may comprise a cable operable by a user (for example, by means of a lever) to pull the arm to cause deflection of it.

The arm may comprise one or more blades of metal, or other resilient material such as a composite. There may be two spaced, parallel blades interconnected at their end portions. The blades may be shaped in a staggered or curved arrangement in their normal condition, deflection of them to at least partially straighten.

The drive connecting means may comprise a generally circular body having a plurality of recesses and the driven means having a corresponding plurality of projections for engagement therewith for transmission of drive. In such an arrangement, the body may be formed from a chainwheel and the projections may be shaped bolt heads projecting from a supporting body.

A problem which is encountered by many vehicles of the recumbent bicycle type is that they cannot be moved easily other than by a seated rider because the steering mechanism cannot be operated easily and there is no easily accessible part of the machine to take hold of with which to manoeuvre it. This is a very serious shortcoming for a heavily-loaded machine.

The present invention provides, from a fourth aspect, a steering mechanism for a vehicle comprising first handle means with which the vehicle can be steered normally by an operator and second handle means having a first condition in which it is not connected to the steering mechanism for steering movement and it does not interfere with normal operation of the vehicle and a second condition in which it is connected to the steering mechanism to effect steering movement and it is readily manipulable by an operator standing adjacent the vehicle.

Thus, by use of the second handle means, steering control can be effected to allow controlled movement of the vehicle by an operator who, for whatever reason, is not riding the vehicle. The second handle means can also be used to tow the vehicle.

The second handle means may comprise an elongate bar secured to the vehicle for pivoting movement at one of its ends. A clutch mechanism may be provided to couple the pivotal movement to the steering mechanism in the second condition and decouple it in the first condition.

Preferably, rotation of the bar about a vertical axis effects steering movement (in the second condition) and movement about a horizontal axis is free for the convenience of the user.

A brake operation device may be provided on the second handle means such that the user can apply the brakes of the vehicle while it is being manoeuvred thereby. The device is preferably disposed so as to be lockable in an applied condition without continuing intervention on the part of the user to serve as a parking brake for the vehicle.

In a fifth of its aspects, the invention provides a drum brake for a human powered vehicle comprising a drum for rotation with a wheel of the vehicle, a backplate secured to a frame of the vehicle, and carried on the backplate, a pair of shoes each supported at a first of their ends on a common stop and acted upon, at a second of their ends, by an expander operative to force them against the drum; wherein the backplate comprising a first component fixed with respect to the axis of rotation of the wheel, and a second component on which the stop and the expander are carried, arranged for limited movement with respect to the first component radially of the wheel.

By this arrangement, uneven brake application resulting from one of the shoes being more worn than the other is avoided, the second component moving on application of the brake to equalise the force applied to the shoes.

In a sixth of its aspects the invention provides a human powered vehicle incorporating any or all of the second to fifth aspects of the invention.

An embodiment of the invention will now be described in detail, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a side view of a chassis frame for a vehicle embodying the invention; Figure 2 is a plan view of the chassis frame of Figure 1; Figure 3 is an enlarged view of the forward part of a forward frame component of the chassis frame on which steering and transmission components have been assembled; Figure 4 is a sectional view of an assembly for mounting a second steering handle on the forward frame member; Figure 5 is a schematic diagram of a power transmission system of a vehicle embodying the invention; Figure 6 is an exploded diagram of a differential assembly for use in the power transmission system of Figure 5; Figure 7A is a plan view of the components of a clutch arm for use with the system of Figure 5;; Figure 7B is an enlarged section of an end portion of the assembled components of Figure 7A; and Figure 7C is a side view of the section of Figure 7B; and Figure 8 is an expanded view of a final drive assembly of the power transmission system.

It is to be understood that use of terms herein such as upward, lower, front, rear, and so forth are intended to refer to the orientation in which the described components would be found within a vehicle in normal use.

With reference to Figures 1 and 2, a chassis frame 10 comprises a forward frame component 12 and a rear frame component 14.

The forward frame component comprises first and second elongate box sections 16,18 of generally squaresection steel tube. The box sections 16,18 are secured together in an overlapping arrangement such that, in normal use, a lower surface of the first box section 16 is in contact with an upper surface of the second section 18, each section overlapping the other for about one third of its length.

A pair of arms 20 extend symmetrically and horizontally from the second box section 18 from approximately the mid-point of the overlap. Each arm 20 is formed as a box section similar to that from which the box sections 16,18 are made. The arms 20 extend to be co planar with the second box section 18 and are angled towards the front of the chassis frame at approximately 200. Each arm 20 has a respective triangulation member 22 from a location approximately three-quarters of its length from the box section 18 to the box section itself.

The triangulation members .22 meet the box section 18 forward of the arms 20 so as to extend therefrom rearwardly at an angle of approximately 100. The triangulation members 22 serve to resist longitudinal flexing movement of the arms 20.

At the end of each arm 20 remote from the box section 16, there is carried a bearing shell 24 which, in this embodiment, is formed from a bicycle headset. A stub axle 26 is carried by each bearing shell 24 for limited rotation about an axis being offset by a few degrees from normal to the plane of the box section 16 and the arm 20.

The offset is intended to provide desirable castor to the steered wheels. Each stub axle 26 carries a shaft 28 on which a road wheel can be carried.

Immediately rearwards of the first box section 16, a steel pin (not shown) projects upwardly from the second box section 16, while at the rear of the second box section there is a vertical steel cylindrical tubular part 30 welded to the second box section 18. The pin and the tubular part 30 function in connecting the forward frame component 12 to the rear frame component 14, as will be described below.

The second box section 18 further carries a bracket 31 which projects upwardly and on which a seat for an operator of the vehicle can be carried.

The first box section 16 carries a bearing 32 constituted by a bicycle bottom bracket shell. On this, is mounted a pedal crank and chain wheel assembly (see Figs 3 and 5) with which a user can propel the vehicle.

At the front of the first box section 16, there is carried a safety guard comprising a pair of arms 34 extending transversely and angled rearwardly to act to protect a user's legs in case of a frontal impact. Each arm 34 may additionally carry a light 36. Close to the front of the first box section 16 there is a bearing 37 for the second steering handle means, to be described below.

The rear frame component 14 comprises a longitudinal steel box section 40 at the rear of which are a pair of welded box section arms 42, similar to the arms 20 of the forward frame component 12. Similarly, the arms 42 have triangulation members 44. Each arm has a stub axle 46 secured to its outer end. However, these are fixed since steering movement is not required of the rear road wheels.

A steel bracket 48 is welded to the underside of the box section 40 between the arms 42 and the triangulation members 44. The bracket 48 is angled downwardly and forwardly from the box section 40. It carries a steel pin 50 remotely from the box section, at an angle of about 100 from perpendicular to the box section. A cylindrical steel tubular part 52 is secured to the forward end of the box section 40 at a similar angle.

The tubular parts 30,52 and pins 50 (including the front pin, not shown) co-operate to interconnect the forward and rear frame components 10,12. Within each tubular part 30,52 is secured a metal/rubber composite bush having inner and outer steel tubes (the outer of which is an interference fit in its tubular part 30, 52) bonded together by an annulus of rubber. The pin of each frame member 12,14 is inserted into the bush of the other and secured there (for example, by application of a nut to the pin). By this arrangement, the frame members 12,14 are permitted limited torsional relative movement but relative moment in any other directions is substantially prevented.It will also be appreciated that the box sections of the members will be angled with respect to one another in accordance with the angle of the tubular part 52 of the rear frame member 14 and by the spacing of the pin 50 from the box section 40 of the rear frame component 14 due to its being carried on the bracket 50.

This permits convenient disposition of the seat, the pedals, and the steering assembly.

A bolt (not shown) is located in the rearmost wall of the box section 16, extending rearwardly towards the tubular part 52 of the rear frame component. This bolt constitutes means to resist movement of the rear frame component forward with respect to the forward frame component as might otherwise occur due to compression of the rubber in the bushes.

With reference to Figure 3, the steering assembly includes first handle means comprising a handlebar 60 pivotally mounted on the first box section 16 of the forward frame component 14, the pivotal axis being just forwards of the arms 20. A shaft 64 extends through the box section 16, the handlebar 60 being secured to an upper portion of it and a plate 62 of rounded triangular shape being secured to a lower portion. The plate 62 extends rearwardly from the shaft 64, broadening rearwardly, and having a rear edge generally in alignment with the handlebar 60.

A respective track rod 66 extends between a rear corner position of the plate 62 and each of the stub axles 26, the track rod 66 being pivotally connected to each of them by a rose joint. At least one rose joint is adjustably connected to its track rod 66 to allow for adjustment of the effective length of the track rod and so the toe-in of the front road wheels.

It will be seen that pivotal movement of the handlebar 60 will cause pivotal movement of the plate 62 which will be transmitted by the track rods 66 to the stub axles 26 to cause steering movement thereof.

A second handle means being a steering handle 70 is connected by a connection assembly to the bearing 37 in the box section 16 of the forward frame member 14. In normal use of the vehicle, the steering handle 70 extends rearwardly, parallel to the box section, and is secured there by a plastic clip 72. In this condition, the steering handle 70 is disconnected from other parts of the steering mechanism which is then free to operate independently of it.

Turning now to Figure 4, there is shown the connection assembly. The assembly comprises a first component 72 which has a head 74 from which extends a length of tube 76. The head 74 has a slot into which is received a thin end portion 75 of the steering handle 70.

The head 74 has a transverse tapped hole 78 which aligns with a hole (not shown) in the end portion 70 when assembled. A bolt 80 is then inserted into the hole 78 to connect the handle 70 thereto in such a manner as to allow pivoting of the handle 70 about the axis of the bolt 80. The tube 76 has a longitudinal slot (not shown) running part way along its length so as to permit radial expansion thereof, as will be described below.

The assembly further comprises an expansion mechanism 82. The expansion mechanism 82 comprises a rod 84 which extends coaxially with the tube 76 and which is secured in threaded engagement with the head 74. Mounted on the rod is an expansion wedge 86. The expansion wedge is constituted by a block of metal of round section having an axial through bore through which the rod 84 passes. The wedge 86 has a frustoconical portion which engages with an end portion of the tube 76 and which is shaped and dimensioned such that when the wedge 80 is urged into the tube 76, radial expansion thereof occurs.

A helical spring 88 is disposed surrounding the rod 84 between the head portion 74 and the expansion wedge 86.

The spring 88 is arranged to be under compression so as to urge the wedge 86 from the end of the tube 76.

A camming mechanism is mounted on the rod 84 remote from the head portion 74. The camming mechanism comprises a body 90 and an operating lever 92. In operation, movement of the lever 92 causes the body 90 to be urged axially along the rod 84. The entire assembly is arranged such that at a first extreme of its travel, the camming mechanism is not in contact with the wedge 86 which is urged from the tube 76 by the spring 88, so allowing the tube 76 to radially contract. At the other extreme of its travel, the camming mechanism causes the wedge 86 to be urged into the tube 76, so causing expansion thereof.

The mounting assembly co-operates with a secondary steering arm 98 which comprises a steel plate 100 and a steel pivot tube 102 interconnected, as by welding, such that the axis of the tube 102 is normal to the plane of the plate 100. The connection assembly is disposed with its tube 76 extending through the tube 102 of the steering arm 98. The two tubes 76,102 are dimensioned such that when the tube 76 is in its normal, contracted state, it is free to rotate within the tube 102. However, when the tube 76 is expanded under the action of the wedge 86, it is forced against the tube 102 so as to be coupled thereto for rotational movement.

The steering arm is mounted for rotation within a bearing tube secured in the box section 16 of the forward frame component 14. Thus, it will be seen that when the camming mechanism is operated so as to allow the tube 76 to contract, the steering arm is free to rotate within the box section 16 independently of the handle 70.

However, when the camming mechanism is operated so as to expand the tube 76, the steering handle 70 becomes coupled thereto such that movement of it in a horizontal plane causes corresponding movement of the steering arm 98.

The steering arm 98 is connected to the steering arrangement described above in such a manner that steering movement of the wheels is accompanied by a corresponding movement of the steering arm 98. This is achieved as follows.

Mounted on the plate 100 of the steering arm 98 is a cylindrical steel spigot 104, which extends from the plate 100 with its axis generally parallel to that of the tube 102. A connecting rod 108 (see Figure 3) interconnects the spigot 104 with a similar spigot 110 mounted on the handlebar 60. The rod 108 is connected to the spigots 104,110 by rose joints. In this manner, motion of the steering arm 98 is transmitted to result in corresponding motion of the handlebar 60. Consequently, by operation of the camming mechanism, the steering handle 70 can be connected to the steering mechanism, so allowing the vehicle to be towed thereby while steering control is maintained.

To provide a user with additional control while the vehicle is being towed, a brake operation lever 112 is provided on the steering handle 70. The lever 112 is arranged such that manual operation thereof will apply brakes to the wheels of the vehicle. Additionally, a loop 114 of elastomeric material is provided which may be passed over an end of the lever 112 to maintain the brakes in an applied condition.

With reference now to Figure 5, there is shown schematically an arrangement for transmission of motive power within the vehicle.

The prime source of power is a user operating pedals 120. The pedals 120 are connected through a crankshaft 122 to a first chain wheel 124, the shaft 122 being borne in the bracket 32. A first endless chain 126 transmits drive between the first chain wheel 124 and a multi-speed cluster 128. The cluster 128 is carried on an intermediate shaft 130 which is supported on a pair of brackets 132, each fixed to an inner portion of a respective arm 20. A derailleur mechanism (not shown) is provided to allow selection of which wheel of the multispeed cluster 128 will be driven by the chain 126.

An intermediate chain wheel 134 is also secured to the shaft 130, on the opposite side of the box section 14 of the forward frame member. From the intermediate chain wheel 134, a second length of chain 136 extends rearwardly to one of a pair of final drive wheels 138. A second derailleur (not shown) permits movement of the second chain 136 between the final drive wheels 138.

A clutch mechanism 144 allows for a drive connection between the final drive wheels 138 and the differential 140 to be disconnected under control of a user of the vehicle.

The pedals, crank, multi-speed cluster, chain and derailleur mechanisms described above are well known to those familiar with bicycle technology. The differential assembly 140 and the clutch assembly 144 will, however, be described in greater detail.

The purpose of the differential assembly 140 is to permit the driven road wheels to rotate at different speeds, as is necessary when the vehicle is negotiating a curve. With reference to Figure 6, the differential assembly comprises first and second drive collars 160 each intended to receive an end portion of a respective driveshaft 142 to transmit drive thereto. Drive is transmitted to each of the drive collars 160 by a respective drive wheel 162, drive transmission being unidirectional so that each drive shaft can rotate in a forward moving direction - that is to say, the vehicle can freewheel with each driven wheel being driven by a separate over-running clutch constituted by the drive collar 160 and drive wheel 162.The drive wheels and drive collars 162,160 are incorporated into an assembly comprising a central spacer164 disposed between the two drive wheels 162 and a pair of outer blocks 166, each wheel being clamped between the central spacer 164 and a respective outer block 166.

The spacer 164 has eight equally spaced axial tabbed holes. Four bolts 168,168' pass through each of the outer blocks 166 and are secured in the tabbed holes. The bolts 168 securing a first of the outer blocks 166 are simple cap screws. The bolts 168' securing the other of the outer blocks 166 have enlarged heads 170, the heads being arranged to co-operate with formations within the clutch assembly 144 (to be described below) to transmit drive to the differential assembly 140.

It will be seen that where drive is being transmitted through the bolts 168' to the differential assembly 140, and the vehicle is travelling in a straight line, drive will be transmitted through both of the collars 160 to the drive shafts 142. If the user stops pedalling, then the differential assembly will cease to rotate, but the drive shafts 142 may continue to rotate due to the one-way drive between the drive wheels 162 and the drive collars 160. When the vehicle negotiates a bend, drive can be fed to the slower rotating inner wheel. The faster rotating outer wheel will not be driven, but its faster rotation is permitted, it is effectively freewheeling. Furthermore, if one wheel should lose traction (for example, through being stuck in mud or by being raised off the ground) drive can still be directed to the other wheel.

With reference to Figures 7A to 7C, the clutch assembly 144 comprises a clutch arm 180 formed from two elongate resilient metal blades 182, 184 of aluminium alloy. Each blade 182, 184 has parallel end portions interconnected by an angled portion. The blades 182, 184 are spaced by a respective aluminium spacer 186, 188 disposed between their end portions. At a first of the end portions (to be referred to as the mounting portion) the arm is secured to a side wall of the box section 14 of the rear frame component adjacent the second chain 136. From there, the arm 180 extends rearwardly, its other end portion (the drive end portion) being spaced from the frame due to the angle of the angled portion.

A cable (not shown) passes through the box section 14 and is secured to the arm 180 at its drive end portion. A control lever is provided on the handlebar 60 with which the user can tension the cable causing the arm 180 to be drawn towards the box section 14.

A circular aperture 190 extends through the drive end portion, extending through both blades 182, 184 and the spacer 188, having a diameter larger within the spacer than within the plates. A bearing 192 is retained in the aperture 190, within the spacer 188, trapped between the plates 182, 184. The drive shaft 142 which connects the differential assembly 140 to the road wheel on the opposite side of the box section 14 passes centrally through the aperture 190.

With reference to Fig 8, a final drive assembly 200 is supported by the clutch arm 180. The final drive assembly comprises a body 202 fitted closely within the bearing 192. A small portion of the body 202 projects therefrom away from the differential assembly 140 and has a locking ring 204 secured around its end portion to prevent movement of the body 202 towards the differential assembly 140. A greater part of the body 202 projects from the opposite side of the bearing. On this is supported a freewheel assembly 206 comprising a modified multi-speed cluster, the body having suitable external formations for co-operation therewith. The cluster is retained in place with a second locking ring 210. Within the body 202 is provided a bearing 208 to support the drive shaft 142 passing therethrough.

The freewheel assembly 206 comprises two final drive chainwheels 138 located adjacent the clutch arm. Next to these is a circular plate 212 to limit movement of the chain 136. Adjacent to that, is a third chainwheel 214.

The third chainwheel 214 does not carry the chain. Its purpose is to provide a driven means with which the drive connecting means of the clutch (constituted by the enlarged heads 170 of the bolts in the differential assembly 140) co-operate. The heads entering the recesses between adjacent teeth of the third chainwheel 214.

In operation, drive is normally transmitted to the differential assembly 140 from the final drive chainwheels 138, through the third chainwheel 214 and the bolt heads 170. When the cable is tensioned by the user, the clutch arm 180 is flexed away from the differential assembly, carrying the final drive assembly 200 with it.

The third chainwheel 214 moved such that the bolt heads 170 are withdrawn. Thereafter, the user may pedal freely and operate the derailleur mechanisms to select the required gear before releasing the cable to re-instate drive to the wheels.

Claims (24)

CLAIMS:

1. A land vehicle comprising: (a) a chassis frame having forward and rear frame components, each carrying a pair of road wheels, those of the forward frame component being rotatable for steering movement, the frame components being relatively movable in rotation about an axis approximately aligned with straight ahead movement of the vehicle; (b) a seat carried on the chassis frame; (c) steering means by which the road wheels of the forward frame component can be controlled by a user for steering movement using first handle means operable by a user riding the vehicle and second handle means operable by a user standing adjacent the vehicle, the second handle means having a first condition in which it is operatively disconnected such that movement of it does not cause steering movement and a second condition in which it can be operated to cause steering movement; and (d) drive means by which a user can propel the vehicle through transmission of drive to the road wheels of the rear frame component, comprising a multi-speed derailleur chain drive, and clutch means by which the drive means can be disconnected from the road wheels such that the chain can be moved for operation of the derailleur mechanism when the vehicle is stationary.

2. A vehicle according to claim 1 further comprising load carrying means mounted on the chassis frame.

3. A vehicle according to claim 2 in which the load carrying means is arranged to be demountable and to be interchangeable with one of an alternative configuration suited to a load to be carried.

4. A vehicle according to claim 2 or claim 3 in which, the load carrying means is a box-like container.

5. A vehicle substantially as described herein with reference to the accompanying drawings.

6. A chassis frame for a wheeled land vehicle comprising a forward frame component having means for carrying a pair of road wheels for rotation and steering movement, and a rear frame component having means for carrying a pair of road wheels for rotation, the forward and rear frame components being interconnected so as to permit limited twisting movement therebetween about an axis extending approximately in a direction of straight ahead movement of the vehicle.

7. A chassis according to claim 6 further comprising movement restricting means to resist or eliminate relative movement of the frame components along the longitudinal axis, at least in one direction.

8. A chassis according to claim 6 or claim 7 in which the frame components are interconnected at two or more locations spaced apart along the longitudinal axis.

9. A chassis according to any one of claims 6 to 8 in which interconnection between the frame components is arranged to bias their relative positions towards a median position in which the respective axes interconnecting the pairs of wheels are parallel.

10. A chassis according to any one of claims 6 to 9 in which interconnection between the frame components is achieved through one or more metal and elastomer composite bushes.

11. A chassis according to any one of claims 6 to 10 in which the rear frame component has mounting means on which can be carried load carrying means, such as a boxlike or hopper-like container.

12. A chassis according to claim 11 in which the mounting means is adapted to readily permit interchangeability of the load carrying means to allow the vehicle to be adapted to a particular load-carrying task.

13. A chassis for a road vehicle substantially as described herein with reference to the accompanying drawings.

14. A vehicle comprising a chassis according to any one of claims 6 to 13.

15. A steering mechanism for a vehicle comprising first handle means with which the vehicle can be steered normally by an operator and second handle means having a first condition in which it is not connected to the steering mechanism for steering movement and it does not interfere with normal operation of the vehicle and a second condition in which it is connected to the steering mechanism to effect steering movement and it is readily manipulable by an operator standing adjacent the vehicle to move and to steer the vehicle.

16. A steering mechanism according to claim 15 in which the second handle means comprises an elongate bar secured to the vehicle for pivoting movement at one of its ends.

17. A steering mechanism according to claim 15 or claim 16 in which a clutch mechanism is provided to couple the pivotal movement to the steering mechanism in the second condition and decouple it in the first condition.

18. A steering mechanism according to any one of claims 15 to 17 in which rotation of the second handle means about a vertical axis effects steering movement in the second condition and movement of it about a horizontal axis is free.

19. A steering mechanism according to any one of claims 15 to 18 further comprising a brake operation device on the second handle means with which the user can apply a brake of the vehicle while it is being manoeuvred by the steering mechanism.

20. A steering mechanism according to claim 19 in which the brake operation device is disposed so as to be lockable in an applied condition without continuing intervention on the part of the user to serve as a parking brake for the vehicle.

21. A steering mechanism for a vehicle substantially as herein described with reference to the accompanying drawings.

22. A vehicle comprising a steering mechanism according to any one of claims 15 to 21.

23. A drum brake for a human powered vehicle comprising a drum for rotation with a wheel of the vehicle; a backplate secured to a frame of the vehicle; and a pair of shoes carried on the backplate each shoe supported at a first of its end on a stop common to both shoes and each acted upon, at a second of its ends, by a common expander operative to force them against the drum; wherein the backplate comprising a first component fixed with respect to the axis of rotation of the wheel, and a second component on which the stop and the expander are carried, arranged for limited movement with respect to the first component radially of the wheel.

24. A drum brake for a human powered vehicle substantially as described herein with reference to the accompanying drawings.