GB2456077A

GB2456077A - User propelled wheelchair with combined propulsion and steering controls

Info

Publication number: GB2456077A
Application number: GB0903996A
Authority: GB
Inventors: Tim Morgan
Original assignee: Individual
Current assignee: Individual
Priority date: 2007-05-25
Filing date: 2007-05-25
Publication date: 2009-07-08
Anticipated expiration: 2027-05-25
Also published as: GB2456077B; GB2449496B; GB2449496A; GB0903996D0; GB0710054D0

Abstract

A wheelchair comprises wheels 1 driven by a propulsion system comprising reciprocating levers 5. The lever may include a freewheel element and may be connected to the wheel 1 by means of a chain 3 and sprockets 4. The wheel may be suspended using a swing arm 6 supported by a spring element 7. The swing arm 6 and propulsion lever 5 may pivot about a common axis, ensuring that propulsion is unaffected by the suspension. Directional control is provided by a steering mechanism comprising a single pivoting lever 13 controlled by the user's hand and connected to a pivotable steering wheel. The steering lever may be connected to the steering wheel by means of cables.

Description

1 2456077 All Terrain Wheelchair This invention relates to a device that enables users to travel over rough terrain whilst seated and whereby movement of the vehicle is effected by the power of the arms.

Normally people with fully functioning limbs can travel over rough ground using bicycles or tricycles designed for the purpose and where the power is provided by the legs. There are a number of people who for various reasons do not have the ability of using their legs for driving such vehicles. These people will typically use a wheelchair and drive it by using their arms, normally by rotating wheels positioned either side of their body when seated. These wheelchairs are satisfactory when the terrain is smooth and the incline of the path is not steep. As the terrain becomes rough and the inclines varied so it : becomes both difficult and hazardous to move the vehicle whilst seated. S...

Standard wheelchairs have good practicality on smooth surfaces, but have * poor off-road performance and limit the terrain which can be tackled. People *: who use these wheelchairs are restricted from moving over rough ground, so *eS * they cannot freely travel around many gardens and parks or natural fields and : .. walks which the able bodied people take for granted. It is a purpose of this 5*S invention to provide such people the facility of moving into spaces that are currently impossible for them to visit.

Certain four wheeled downhill racing wheelchairs have good off-road performance and allow the user to tackle a high level of rough terrain, but lack the practicality of a standard wheelchair for everyday use.

Typically a standard wheelchair is driven by the user repeatedly grasping each wheel rim by each hand, moving the hands forwards using the muscles in the arms, then releasing the rim and moving the hands back to again grasp the rim and repeat the cycle.

It is very difficult for a user to move a standard wheel chair over an uneven or soft surface because the force required to rotate a wheel directly whose axis carries the load of a person's weight becomes too great for a person's arm. In addition, if it was required to move the vehicle over an obstacle or up a steep incline, not only does the user have to use great force to rotate the wheel to propel it forwards, but the user must, between forward strokes, prevent the vehicle from moving backwards. In order to steer the vehicle a different force is applied to one wheel relative to the other wheel. Such an operation clearly limits the force available to drive the vehicle forward which may again restrict the user to less challenging terrain. In addition, since the wheels and axes must be conveniently located to enable the user to effectively apply force to the wheels to drive the vehicle forwards, then the relative position of the centre of gravity of the user to the point of contact of the wheels on the ground is not optimised to maximise stability of the vehicle.

It is the purpose of this invention to overcome these shortcomings by providing a propulsion means so that the user can deliver sufficient force to the wheels to drive over obstacles and over soft ground; that there is braking means provided to prevent the vehicle from rolling backwards down inclines *. and control the speed of descent forwards; that there is a steering means : provided to steer the vehicle without reducing the power available to drive the * vehicle forward and that there is a configuration means provided to position the user relative to the supporting wheels so as to improve stability on inclined surfaces. Any one or all of these means can be included in the vehicle to improve the ability to travel over rough terrain.

The steering means is preferably provided by a ground engaging wheel or wheels the direction of which can be controlled by means of a manually operated lever and cable arrangement so adjusting the direction of travel of the vehicle. The steering wheel or wheels may be mounted to the frame via a means of cushioning. The propulsion means is provide by a manually held lever and ratchet mechanism which operates a drive mechanism to turn the wheels and propel the vehicle forwards or backwards. A cushioning means may be provided such that the axis of the driving wheels may be displaced relative to the attachment means. A braking means is preferably provided by manually squeezing a lever which operates a cable and brake mechanism very like that used on conventional bicycles. The resultant design provides a means for the user to steer, drive and brake the vehicle using only the hands and arms without losing grip.

The cushioning means suspending the steering and propulsion should preferably be damped suspension struts such as an air or coil spring shock absorber, but could also be achieved via other means such as a torsion spring or rubber blocks.

The cushioning means may be adjustable so that the degree of cushioning and damping may be modified to suit different users.

The steering means is preferably provided by operating cables which twist the steering wheel left or right due to an input from the user. It may also be provided by use of hydraulic or pneumatic mechanisms. S.,.

:r' The propulsion means is preferably provided by a ratchet free-wheel, but *. could also be provided by use of a one way clutch. The free-wheel can also : be modified to alter the direction in which the device may travel.

The drive mechanism to translate the operation of the lever to the rotation of the drive wheels is preferably provided by a chain and sprocket. However, it could also be provided by a belt and pulley arrangement or shaft drive.

The propulsion means may be adjustable so that different speeds of travel may be achieved by varying the mechanical advantage of the system. This may be achieved by introducing a means of changing the gear ratio between the lever and the drive wheel or alternatively by varying the length of the propulsion lever.

In order to achieve satisfactory stability and a better abihty to overcome obstacles the vehicle is preferably arranged so that the larger diameter drive wheels are at the front and the steering wheel or wheels at the rear. The device may also be arranged with the larger diameter wheels at the rear and the steering wheel or wheels in the front.

The braking means is preferably provided by a disc brake mounted at the hub of the ground contacting wheel and a hand operated lever mounted on the propulsion lever. However, the braking means may also be provided by a rim brake or drum brake.

It is preferred that the steering means, arrangement of larger diameter drive wheels at the front, propulsion means and suspension system are all used in conjunction as each system in isolation does not work effectively if fitted to a standard wheelchair. It may also be possible to install the steering means without the propulsion means or cushioning means, or in the less preferable arrangement with the larger diameter wheels at the rear. The installation of any of the aforementioned subsystems in isolation is possible but not S... preferred for optimum performance. *5**

*. The invention will now be described solely by way of example with reference : to the accompanying drawings in which: Figure 1 shows the overall preferred layout of the device with larger diameter drive wheels at the front and steering wheel at the rear Figure 2 shows the overall layout of the device in isometric view with the front wheels hidden for clarity Figure 3 shows a Direct Steering mechanism Figure 4 shows a Direct Steering mechanism with an alternative method of actuation Figure 5 shows a Direct Steering mechanism with cushioning means Figure 6 shows a Direct Steering mechanism with an alternative cushioning means Figure 7 shows a Direct Steering mechanism with another alternative cushioning means Figure 8 shows a lever operated Propulsion system packaged with a means of cushioning Figure 9 shows a lever operated Propulsion system with an alternative drive system Figure 10 shows a lever operated Propulsion system with another alternative drive system * S. S S...

Figure 11 shows a freewheef device used in a lever operated Propulsion : system S..

S

: Figure 12 shows a lever operated Propulsion system in detail .5.

Figure 13 shows a lever operated Propulsion system packaged with disc brake In Figure 1, the wheelchair features front wheels number I which are of larger diameter than the rear steering wheel number 2. The front wheels number 1 are driven via a propulsion mechanism consisting of a chain 3 and sprockets 4 and a propulsion lever 5 including a freewheel element allowing the device to travel without causing the propulsion lever to rotate. The propulsion system is supported by a swing arm member 6 which is freely hinged at its upper end and carries the ground contacting wheel and axis at its lower end. The swing arm 6 and propulsion lever 5 both pivot about the same point such that the propulsion system is unaffected by vertical displacement of the ground contacting wheel. A sprung suspension strut 7 is connected between member 6 and the main frame 8 thus allowing vertical displacement of the ground contacting wheel. A member 9 is free to rotate at its upper end and supports the rear steering wheel at its lower end. A sprung suspension strut 10 is :::: connected between 9 and 8 allowing vertical displacement of the rear wheel in order to cushion impacts from an uneven road surface. The rear steering wheel 2 is connected to member 9 by a steering fork II which is constrained :r horizontally by member 9, but is free to rotate about a vertical axis thus *. allowing the wheel 2 to steer the device left or right according to the input of * * the user. The user operates the steering from the steering lever 12 which is located at the upper end of the propulsion lever 5.

The arrangement described in Figures 1 and 2 allows the device to be propelled over uneven ground, up and down steep slopes and allows the user to control the direction in which the device travels effectively. The systems of propulsion and steering should be used in conjunction in order to facilitate effective operation of the device as the user activates the steering and propulsion from the same point; hand grip 13. It is possible to implement these two subsystems in isolation; however this would result in poor usability and performance. For example, the direct steering is necessary with the wheel arrangement described in order to avoid dynamic instability when cornering.

Figure 2 shows the right and left Propulsion levers 5 which allow drive to be applied independently to the right and left wheels. The steering lever 12 may be fitted to either the right or left propulsion lever depending on the preference of the user. The left and right brakes may also be operated independently of each other to allow effective manoeuvrability.

In Figure 3, a Direct Steering system consists of a pivoting lever 12 which is mounted on the end of propulsion lever 5 where it is hinged freely. This allows the User to pivot the lever 12 left or right to steer whilst still being able to apply force to the propulsion lever. Lever 12 pulls cables A and B which are threaded through hollow flexible tubes such as cable outer housings and attached at their lower end to the steering pivot 18. Member 18 is mounted on the steering fork 11 so that axial rotation of the steering pivot is translated to axial rotation of the fork and in turn the ground contacting steering wheel 2 which is fixed to the fork 11. In order to steer left for instance, the User pivots the steering lever left with their hand which pulls cable B that in turn causes * . * ::..* steering pivot 18 to rotate, thus causing the steering wheel 2 to rotate axially.

In order to steer right, the User pivots the steering lever right with their hand *.:r which pulls cable A that in turn causes steering pivot 18 to rotate, thus . causing the steering wheel 2 to rotate axially. The degree of steering force * required may be adjusted by fixing the steering cable at different positions m. along the members 12 and 18 in order to vary the mechanical advantage of the lever. This system facilitates effective control of the direction in which the device may travel.

Figure 4 shows an alternative embodiment where hydraulic or pneumatic pistons 19 are activated by the steering pivot 12, which via displacement of hydraulic fluid or air, activate identical pistons 19 that apply force to the steering pivot 18 thus causing axial rotation of the ground contacting steering wheel to facilitate steering.

Figure 5 shows the packaging of the Direct Steering with a means of cushioning provided by an air sprung damper unit which benefits effective steering by keeping the steering wheel 2 in contact with the ground over uneven terrain by allowing vertical displacement of the wheel to cushion impacts from an uneven ground surface. Preferably the air shock absorber should be adjustable for different users by varying the air pressure in the piston and adjusting the damping rate using conventional valves and adjuster dials.

Figure 6 shows an alternative embodiment where a coil spring damper unit is used. Preferably the shock absorber unit should be adjustable for different users by conventional adjustment means such as a screw thread end stop and damping rate adjustment dial.

Figure 7 shows another alternative method of cushioning where a torsion spring element is mounted between the main frame 8 and the swing arm 9 at the hinge point of the two members thus allowing vertical displacement of the ground contacting steering wheel. * * *

::..: In Figure 8, a lever Propulsion system consists of a propulsion lever 5 which has a free wheel element at its lower end. The user applies force to the lever S... . *..: at the hand grip 13 using their hand which causes the upper sprocket 4 to * rotate and in turn translate rotary motion to the lower sprocket 4 by a chain 3.

* The lower sprocket 4 is mounted to the front wheel hub 16 which results in rotation of the ground contacting wheel in order to propel the device forwards from a force inputted at the propulsion lever by the user. A chain tensioner 23 such as a stationary block of material or a roller wheel, ensures the chain is tensioned correctly to prevent it from becoming derailed from the sprockets.

The device is able to move forwards without causing the propulsion lever to move relative to the chain and sprockets due to the operational characteristics of the freewheel. The direction in which the freewheel engages may be altered by turning the adjuster wheel 15 thus allowing the device to travel in forwards or reverse modes. In order to facilitate effective propulsion over uneven terrain, the propulsion system is packaged with a means of cushioning which allows vertical displacement of the wheel without compromising the performance of the propulsion mechanism as the suspension arm 6 and drive sprocket 4 both pivot and rotate about the same axis independently. The means of Cushioning is preferably provided by an air sprung damper unit, however the alternative means of cushioning depicted in Figures 6 and 7 may also be applied.

Figure 9 shows an alternative embodiment where drive is transmitted to the ground contacting wheel from the propulsion lever by a belt and pulley system which could be a timing belt or conventional belt and tensioned via a roller device.

Figure 10 shows another alternative embodiment where drive is transmitted from the propulsion lever to a bevel gear which contacts another bevel gear fitted to the end of a rotary shaft which transmits drive to the ground contacting wheel via an identical bevel gear arrangement at its lower end.

This arrangement is not preferred as it cause to device to travel in the opposite direction to which the user applies force to the propulsion lever. * *

Figure 11 shows the freewheel element in more detail, where drive is **IS engaged by pushing the propulsion lever 5 in the direction of desired motion, thus causing the pawls 35 to engage with the ratchet 34 as the pawls are * * forced outwards by springs 36. The freewheel 24 is therefore caused to rotate and as the sprocket 4 is mounted to the freewheel 24 engagement of the ratchet and pawls transmits drive to the sprocket and consequently the ground contacting wheel via the chain drive. On occasions when the chain and sprocket are rotating at a greater speed than the ratchet 34, the pawis are able to pivot downwards by compressing the springs 36, thus allowing the device to move forwards without causing the propulsion lever to rotate. The direction in which the freewheel operates may be altered by rotating the switch 15 which repositions the pawls so that they engage the ratchet when it is rotated in the opposite direction. This function may be achieved using conventional socket wrenches. The freewheel facility may also be achieved by a one way clutch but is not preferred as the ratchet system allows the device to travel either forwards or reverse.

Figure 12 represents the propulsion system in cross section, showing that the swing arm 6 and upper drive sprocket rotate around the same pivot shaft 31.

This allows vertical displacement of the ground contacting wheel whilst drive is still able to be transmitted effectively to the ground contacting wheel throughout the motion of the suspension. During motion of the device, the drive chain rotates continuously and the freewheel 24 allows the propulsion lever 5 to remain stationary or apply force when required.

In Figure 13, the propulsion and suspension system is packaged with a means of deceleration mounted to the front wheel hub 16 in order to provide the user with an effective means of controlling the devices speed when descending and ascending slopes. The brake is activated by the user pulling a lever mounted to the propulsion lever such that it is easily accessible from the hand grip where the user applies force to the propulsion lever. The brake may be a conventional disc brake actuated via hydraulic pistons or via cables :. operating a cam in order to push pads onto the surface of the disc rotor 38.

*::. The disc brake calliper 39 is mounted to the swing arm 6 such that braking performance is unaffected by vertical displacement of the ground contacting s.

wheel.

S * ** ** S S..

Claims

1. A vehicle for conveying one person, comprising three or more ground contacting wheels, a propulsion mechanism used to translate reciprocating movement of the User's arms to the ground contacting wheels and a steering system comprising actuation means to translate movement of the User's arms to adjust the alignment of one or more of the ground contacting wheels in order to control the direction of the device, wherein a propulsion mechanism is supported by a means of cushioning such that vertical displacement of the ground contacting wheel is allowed without interrupting the drive supplied to said wheel due to the arrangement such that a propulsion lever pivots about the same axis as a swing arm element which supports the ground contacting wheel.

2. A vehicle as claimed in Claim I wherein the propulsion system consists of a pivoting lever free to rotate about an axis, attached to which is a sprocket and chain arrangement connected to the ground contacting wheels such that motion of the vehicle is achieved when a force from the User is applied to the propulsion lever.

3. A vehicle as claimed in Claim 2 where an element such as a block or jockey wheel acts on the chain to maintain the required tension and prevent the chain becoming derailed.

4. A vehicle as claimed in Claim 2, in which a belt and pulley arrangement transmits rotation of the propulsion lever to the ground contacting wheel.

5. A vehicle as claimed in Claim 4 where an element such as a block or roller wheel acts on the belt to maintain the required tension and prevent the belt slipping when drive force is applied to the propulsion system.

6. A vehicle as claimed in Claim 2, in which a bevel gear and shaft drive system transmits rotation of the propulsion lever to the ground contacting wheel.

7. A vehicle as claimed in Claim 2, wherein the degree of mechanical advantage provided by a propulsion system may be varied by adjusting the gear ratio between the prolusion lever and the ground contacting wheel.

8. A vehicle as claimed in Claim 2 where in the degree of mechanical advantage provided by a propulsion system may be varied by adjusting the length of the propulsion lever.

9. A vehicle as claimed in all previous claims wherein a freewheeling element acts between the propulsion lever and chain and sprocket such that the ground contacting wheel may rotate without forcing said propulsion lever to rotate.

10.A vehicle as in Claim 9 where the freewheeling element may be provided by a ratchet and pawl mechanism such that the pawl is biased onto the ratchet by a spring such that drive will be engaged when the propulsion lever rotates in one direction but allowing free rotation when the propulsion lever is rotated in the opposite direction.

11. A vehicle as in Claim 10 where the direction in which the freewheel element acts in order to allow free rotation of the propulsion lever, may be altered by repositioning the pawls, thus allowing the direction in which drive is engaged when a propulsion lever is rotated to be reversed.

12. A vehicle as in Claim 9 wherein the freewheeling element is provided by a one way clutch unit or units such that drive is engaged when the propulsion lever is rotated in one direction and free rotation is allowed when the propulsion lever is rotated in the opposite direction.

13. A vehicle as claimed in all previous claims wherein a ground contacting wheel on each side of the device is supplied with a propulsion system, thus allowing drive to be applied to each wheel independently or simultaneously if required.

14.A vehicle according to any one of the previous Claims such that a means of cushioning is provided by an air sprung damper unit acting between a swing arm member and a supporting member.

15.A vehicle according to Claim 14 such that a means of cushioning is provided by an air sprung damper unit such that the degree of cushioning may be adjusted to suit different Users via altering the air pressure and damper rate in the damper unit using conventional valves and adjuster dials.

16. A vehicle according to any one of the previous Claims such that a means of cushioning is provided by a coil sprung damper unit acting between a swing arm member and a supporting member.

17. A vehicle according to Claim 16 such that the means of cushioning is adjustable by conventional means such as a screw thread and end stop used to vary the preload on the spring.

18. A vehicle according to any one of the previous Claims such that a means of cushioning is provided by a torsion spring acting between a swing arm member and a supporting member.

19. A vehicle according to Claim 18 such that the means of cushioning is adjustable by conventional means such as a screw thread and end stop used rotate the torsion spring in order to vary its tension and set the preload for different Users.

20. A vehicle according to any one of the previous claims wherein a ground contacting wheel on each side of the vehicle is provided with a means of deceleration such as a disc brake mounted on a swing arm member such that braking performance is unaffected by lateral displacement of the wheel.

21.A vehicle according to Claim 20 wherein each brake supplied with a means of actuation mounted on a propulsion lever accessible from the position at which force is applied by the User's hands to effect propulsion, such that braking forces can be applied to the corresponding wheel independently of the other wheel.

22. A vehicle according to Claims 20 and 21 wherein a means of deceleration is provided by a drum brake.

23. A vehicle according to Claims 20 and 21 wherein a means of deceleration is provided by a rim brake.

24.A vehicle according to Claims 20 and 21 wherein a means of brake actuation is provided by a hand operated brake lever.

25. A vehicle according to any one of the previous claims wherein two opposing front ground contacting wheels of larger diameter than one or more rear ground engaging wheels such that the User may propel the vehicle by applying force to propulsion levers which effect rotation of the front wheels.

26. A vehicle according to any one of the previous claims wherein two opposing rear ground contacting wheels of larger diameter than one or more front ground engaging wheels such that the User may propel the vehicle by applying force to propulsion levers which effect rotation of the rear wheels.

27.A vehicle as claimed in Claim 25 wherein the rear wheel or wheels is a steering wheel.

28.A vehicle as claimed in Claim 26 wherein the front wheel or wheels is a steering wheel.

29. A vehicle as claimed in Claims 27 and 28 wherein a steering wheel provides directional control by means of cables linked to a single pivoting steering lever such that the User may effect steering input directly by pivoting said steering lever left or right using their hand, to a steering member attached to the steering wheel, resulting in corresponding left or right motion of the steering wheel.

30. A vehicle as claimed in Claim 29 wherein a pivoting steering lever is mounted on a propulsion lever such that steering input may be affected from the same point at which propulsion force is applied and braking actuation means are mounted thus requiring no hand repositioning when the User operates either the steering, brakes or propulsion systems.

31. A vehicle as claimed in Claim 29 wherein a steering wheel is supported by a fork arrangement, which is free to pivot about an axis perpendicular to the axis of rotation of the steering wheel via a bearing or similar means of low friction rotation.

32.A vehicle as claimed in Claim 31 wherein a steering member is mounted at its centre to the steering fork such that axial rotation of the fork translates to rotation of the steering member.

33. A vehicle as claimed in Claim 32 wherein cables mount to each end of a steering member such that pulling either cable affects axial rotation of the steering member, which consequently affects axial rotation of the steering fork and steering wheel thus resulting in a steering effect.

34. A vehicle as claimed in Claim 33 wherein cables are threaded through hollow flexible tubes such as conventional cable outer housings, which run from the steering member at the steering wheel to the pivoting steering lever on the propulsion lever.

35. A vehicle as claimed in Claim 29 wherein cables are attached to a supporting member mounted to the pivoting steering lever such axial pivoting of the lever left or right pulls the corresponding cable, thus effecting axial rotation of the steering wheel.

36. A vehicle as claimed in Claim 29 wherein cable tension may be adjusted via standard screw thread barrel adjusters acting on the cable housing.

37. A vehicle as claimed in Claim 29 wherein steering actuation is provided by hydraulic hoses and pistons mounted at the pivoting steering lever and steering member attached to the steering wheel to effect steering motion.

38. A vehicle as claimed in Claim 29 wherein steering actuation is provided by pneumatic hoses and pistons mounted at the pivoting steering lever and steering member attached to the steering wheel to effect steering motion.

39. A vehicle as claimed in Claim 29 wherein steering characteristics may be adjusted by varying the position of the clamping point of the cable on the steering member and pivoting steering lever in order to adjust the mechanical advantage of the system to different Users strength.

40. A vehicle according to any one of the previous claims wherein a steering system is supported by a means of cushioning such as an air sprung damper unit acting between a swing arm member and a supporting member in order to maintain contact between the ground and the steering wheel or wheels by allowing vertical displacement of the steering wheel when travelling over uneven ground.

41. A vehicle as claimed in Claims 31 and 40 wherein a swing arm member is able to rotate freely about an axis at one end whilst supporting a steering wheel in a manner that enables free rotation of the steering fork via a bearing arrangement such as conventional roller bearings or plain bearings.

42. A vehicle as claimed in Claim 40 wherein a means of cushioning is provided by an air sprung damper unit such that the degree of cushioning may be adjusted to suit different Users via altering the air pressure and damper rate in the damper unit using conventional valves and adjuster dials.

43. A vehicle as claimed in Claims 40 and 41 wherein a means of cushioning is provided by a coil sprung damper unit acting between a swing arm member and a supporting member.

44. A vehicle according to Claim 43 wherein the means of cushioning is adjustable by conventional means such as a screw thread and end stop used to vary the preload on the spring.

45. A vehicle according to Claims 40 and 41 wherein a means of cushioning is provided by a torsion spring acting between a swing arm member and a supporting member.

46. A vehicle according to Claim 45 wherein the means of cushioning is adjustable by conventional means such as a screw thread and end stop used rotate the torsion spring in order to vary its tension and set the preload for different Users.

47. A vehicle as claimed in C'aim 40 wherein the sprung damper unit may be decoupled from one ore more of its mounting points using a conventional quick release shaft and lever in order to facilitate folding of the swing arm and rear wheel assembly for transport purposes

48. A vehicle according to any one of the previous claims wherein a means of cushioning may be adjusted by altering the mounting position of the damper unit on the swing arm member and the supporting member.

49. A vehicle according to any one of the previous claims wherein a supporting member consists of a frame which supports the opposing swing arms mounted to which are the larger diameter ground contacting wheels and propulsion system and also supports the swing arm mounted to which is the steering wheel or wheels in addition to supporting a User seat

50. A vehicle as claimed in Claim 49 wherein a support member which consists of a frame, has attached a supporting member and footplate in order to support the Users feet.

51.A vehicle as claimed in Claim 50 wherein a footptate supports one or more wheels which may prevent the vehicle becoming unstable by contacting the ground should the vehicle be operated on an incline of sufficient angle to cause the vehicle to tip forwards onto said wheels.

52. A wheeled vehicle as herein described with reference to and as shown in any combination of the accompanying drawings.

53. A Propulsion system as herein described with reference to and as shown in any combination of the accompanying drawings.

54. A Steering system as herein described with reference to and as shown in any combination of the accompanying drawings.