Background Art The track width of a vehicle refers to the lateral distance between the centres of the outer opposing wheels on opposing sides of the vehicle. In general, the larger the wheel track width relative to the height of the vehicle centre of gravity above the ground, the better the vehicle stability and hence, the better the vehicle's off-road mobility. Thus a larger track width is desirable.

There is generally no point having a vehicle body that extends much, if at all beyond the wheel track (except possible to protect the tyres). Thus the distance between the outer faces of outer tyres on opposite sides of a vehicle often dictates the overall width of the vehicle, which is related to its track width. The smaller the track width, the more places a vehicle can pass through, for instance narrow lanes, or can pass into, for instance into a cargo container For most vehicles the opposing desires for off-road mobility and flexibility of use are not a problem. People tend to have either one type of vehicle or the other. However, that is not so easy with emergency or military vehicles. Sometimes it is necessary that the same vehicle is usable fast on rough ground and fast in narrow areas. Moreover, there is an increasing vision of fast response or rapid reaction teams that come in quickly to an area and can deploy immediately, particularly with a desire to fly vehicles in by aircraft, whether by aeroplane, helicopter or dirigible.

With some forms of transportation it is quite easy to change the maximum width of vehicle track that can be carried. For instance plates can be added to the bed of a lorry to

widen it. However, with aircraft in particular, that is not always possible, without designing and building a new aircraft. The internal width of the aircraft constrains the track width and therefore the vehicles that can be carried. Sometimes it may be possible to load a vehicle with a wider track width by first removing the wheels. However, that makes the loading and unloading operation more difficult, as the vehicle cannot be driven on and off. It also increases the time involved at both ends of the journey, as the wheels have to be removed and then put back on.

The usual solution for this problem has been to use smaller vehicles, which lack versatility. In recent years, there has been the development of narrower vehicles.

However, these are too narrowly built for off-road or rough road stability.

The suspension system of a vehicle connects the wheels to the chassis or body shell of the vehicle. The suspension system isolates the vehicle from irregularities from the road, thereby providing a more comfortable to vehicle passengers. The members of the suspension assembly are linked and connected in a certain manner such that their interaction with each other provides certain desired ride and handling characteristics during vehicle movement and articulation.

Systems for altering the height of the suspension in a car have been known for some time. In particular Citroen cars of France have been providing such systems for years. However, changing the height of the suspension tends only to be of use in changing the clearance above and below the body of the car.

United States Patent No. 6,036, 201, issued on 14 March 2000, to Pond et al., describes an adjustable vehicle suspension. Not only does this control the ground clearance, but it also provides some form of adjustability of the wheel track width. Two generally parallel control arms are angled downwards and connected at one end to a frame and at the other to a vehicle kingpin to provide a parallelogram linkage. A hydraulic actuator is pivotally attached to a mid-point on the lower control arm. Pulling the lower control arm upwards from an initial position opens the parallelogram up slightly, before collapsing it with the two control arms generally vertical and the wheel raised in a stowed position. Because the downward angle of the control arms at the initial position is less

than their upward angle at the stowed position, the wheel extends horizontally further out in the initial position than in the stowed position. Thus the wheel track width is reduced as the vehicle clearance is reduced. The document mentions that the system is useful within height-constrained vehicles and craft. However, the Figures within this document show that, if the vehicle is usable with the wheels in the stowed position, it would allow only very limited and slow use. The tops of the wheels are almost in contact with the vehicle body and there appears to be little or no room for turning. As such, what is shown would appear not to be usable in both extreme positions.

In conventional suspension systems, such as a double wishbone, Macpherson strut or trailing arm suspension, it is not possible to adjust the track width.

Summary of the Invention According to one aspect of the invention, there is provided a wheel track adjustment system. The wheel track adjustment system comprises an adjustment assembly comprising swing means and actuator means and a wheel assembly comprising a main wheel axis. A first end of the swing means is pivotally mounted to the wheel assembly. A first end of the actuator means is mounted relative to the swing means and to the wheel assembly such that the actuator means is operable to pivot the swing means and the wheel assembly away from a second end of the actuator means, in a first plane to a first position, and to pivot the swing means and the wheel assembly towards the actuator second end, in the first plane to a second position. The wheel track adjustment system is arranged such that at a third position, between the first and second positions, a straight line defined between the first and second ends of the swing means is orthogonal to the main wheel axis.

According to a second aspect of the invention, there is provided a vehicle comprising a plurality of such wheel track adjustment systems.

According to a further aspect of the invention, there is provided a vehicle. The vehicle comprises a vehicle body and at least two wheel track adjustment systems. Each wheel track adjustment system comprises a wheel assembly and an associated adjustment

assembly mounted on the wheel assembly. Each wheel assembly comprises a main wheel axis for mounting a wheel on which the vehicle is to travel. Each adjustment assembly comprises support means mounted on said vehicle body, swing means and actuator means.

A first end of the swing means is pivotally mounted to the wheel assembly with which the adjustment assembly is associated and a second end of the swing means is pivotally mounted to the support means. The actuator means is operable to pivot the swing means and associated wheel assembly away from the vehicle body to a first position, and to pivot the swing means and associated wheel assembly towards the vehicle body to a second position. The swing means pivots in a first plane of the wheel track adjustment system, which first plane, at a first loading of the vehicle, is substantially parallel to a second plane defined as containing a plurality of main wheel axes of the vehicle.

According to another aspect of the invention, there is provided a method of adjusting the wheel track of a vehicle comprising operating one or more wheel track adjustment systems of the first aspect or the at least two wheel track adjustment systems of the other aspects.

A preferred embodiment provides a wheel track adjustment system which moves a wheel towards and away from the side of a vehicle, thereby changing the wheel track width. Two parallel swing arms are pivotally mounted at one of their ends on a support bar at a fixed position relative to a vehicle body. At their other ends the swing arms are pivotally mounted to a wheel assembly. An actuator is pivotally mounted at one end at a fixed position relative to the vehicle body. At its other end the actuator is pivotally mounted to a mid-point along one of the swing arms. The actuator is operable to pivot the swing arms towards and away from the vehicle and in doing so moves the wheel assembly towards and away from the vehicle, thereby changing the wheel track width. The swing arms extend and pivot in a flat first plane. At a particular loading of the vehicle, this first plane is parallel to a second plane containing the wheel axes of the vehicle, which is generally horizontal.

Introduction to the Drawings

The invention may be more readily understood from the following description, by way of non-limitative examples, with reference to the accompanying drawings, in which:- Figure 1 is an isometric view of a wheel track adjustment system of a first exemplary embodiment in an extended position; Figure 2 is an isometric view of the wheel track adjustment system of Figure 1 in a retracted position; Figure 3 is a front view of the wheel track adjustment system of Figure 1 in the extended position; Figure 4 is a front view of the wheel track adjustment system of Figure 1 in the retracted position; Figure 5 is a top plan view of the wheel track adjustment system of Figure 1 in the extended position; Figure 6 is a top plan view of the wheel track adjustment system of Figure 1 in the retracted position; Figure 7 is an isometric view of a wheel track adjustment system of a second exemplary embodiment in an extended position; Figure 8 is an isometric view of the wheel track adjustment system of Figure 7 in a retracted position; and Figures 9A and 9B are top plan views of a vehicle outline, with wheels in an extended position and wheels in a retracted position, respectively.

Detailed Description

A more complete appreciation of the invention and many of the attendant advantages thereof may be readily obtained by reference to the following detailed description when considered with the accompanying drawings in which like reference characters indicate corresponding parts in the different views.

Figures 1 to 6 show various views of a wheel track adjustment system of a first embodiment. Figures 1, 3 and 5 are an isometric view, a front view and a top plan view, respectively, of the wheel track adjustment system in an extended position. Figures 2,4 and 6 are an isometric view, a front view and a top plan view, respectively, of the wheel track adjustment system in a retracted position. Assuming the vehicle is a front steering vehicle, the wheel track adjustment system in Figures 1 to 6 is for the front right of a vehicle. Equivalent views of the corresponding vehicle wheel track adjustment system for the front left of the vehicle would be mirror images. For a rear steering vehicle, this embodiment would be used at the rear left, with the rear right mirrored.

Figures 1 to 6 show a wheel track adjustment system 10, with a wheel assembly 12, an adjustment assembly 14 and a first vehicle mount 16. The first vehicle mount 16 is shown here as a small plate, but is part of or solidly attached to a vehicle, such as a car or truck. A damper 18, in the form of a compression spring bar, extends between the first vehicle mount 16 and the wheel assembly 12. A first end of the adjustment assembly 14 is attached to the wheel assembly 12. A second end of the adjustment assembly 14 is separately directly attached to the vehicle at a second vehicle mount 20, which is also part of or solidly attached to the vehicle. A drive shaft 22 runs from the drive train (not shown) of the vehicle to the wheel assembly 12. A tie rod 24 also runs from a steering control (not shown) of the vehicle to the wheel assembly 12.

The drive shaft 22 is telescopic, having an outer portion slidable over an inner portion, with a spline and keyway to transmit torque between them. The length of the tie rod 24 does not vary. Instead, the position of the inner end (not shown), that is the end of the tie rod 24 nearer the steering control can vary.

A pin 28 extends from the front face of first vehicle mount 16. A first end of the damper 18 is mounted on the pin 28 by way of a ball joint.

The wheel assembly 12 mounts the wheel 30 for the wheel to rotate about a wheel axis. In this embodiment the wheel assembly 12 includes the wheel 30 (although other embodiments may have the wheel absent) and a generally cylindrical wheel hub 32 on which the wheel 30 is mounted. The wheel hub 32 extends inwardly from the wheel 30.

The wheel hub 32 includes a brake (not shown), as well as a swivel connector (not shown) between the drive shaft 22 and the wheel 30. The brake requires brake fluid tubes or other control lines to it, but these are not shown. The wheel hub 32 incorporates a steering knuckle, including a knuckle lever 34. The outer end of the tie rod 24 is pivotally mounted to the knuckle lever 34. The steering knuckle portion of the wheel hub 32 is pivotally mounted to an end of an adjustment assembly mount 36, between two opposing knuckle holders 38A, 38B, which are spaced apart arms extending from the end of the adjustment assembly mount 36. The two opposing knuckle holders 38A, 38B overlap sides of the steering knuckle. The knuckle holders 38A, 38B and steering knuckle are arranged such that a straight line between the pivot points between the knuckle holders 38A, 38B and the steering knuckle passes through the rotation axis of the wheel hub 32.

In this embodiment, the pivot points are vertically above and below the rotation axis of the wheel hub 32.

The adjustment assembly mount 36 is made up of two opposing, upper and lower plates 40A, 40B, which are extensions of the knuckle holders 38A, 38B, connected by various side plates. The adjustment assembly mount 36 is hollow, with the drive shaft 22 running between the upper and lower plates 40A, 40B and the side plates to the wheel hub 32. The adjustment assembly mount 36 extends inwardly from the wheel hub 32. The second end of the adjustment assembly 14 is mounted on the adjustment assembly mount 36.

A damper mount 42 is fixed at the top of the adjustment assembly mount 36 and a second end of the damper 18 is mounted on the damper mount 42 by way of a ball joint.

The adjustment assembly 14 has a support means, where may be elongate, here exemplified by a torsion support bar 44 extending outwardly from the second vehicle mount 20, in a direction generally parallel to the rotation axis of the wheel 30, in the

relative orientations shown in Figures 1,3 and 5. The support bar 44 is fixedly mounted at one end on the second vehicle mount 20. A first swing arm 46 and a second swing arm 48 extend between a second end of the support bar 44 and the adjustment assembly mount 36, as part of a parallelogram linkage.

The swing arms 46,48 extend in a shared first plane, in this embodiment the first plane runs along the middle lines of the swing arms 46,48. The angle of the first plane (relative to a fixed plane containing the support bar 44) varies according to the loading in the vehicle to which the wheel track adjustment system 10 is attached. The heavier the loading, the lower the vehicle body is (or the higher the wheels 30 are relative to the body). Thus, according to the loading and the suspension, the first plane of a wheel track adjustment system 10 may angle upwards or downwards from the adjustment assembly mount 36 to the support bar 44. The maximum angle in this embodiment is usually no more than 45 degrees either side of the horizontal, otherwise the support bar 44 may take too much vertical force when the wheel goes over a bump. To allow for the vehicle going up or down hill when it goes over a bump, the maximum may be reduced to no more than 30 or even 15 degrees or less, either side of the horizontal. Between the extreme angles, there will be at least a first particular loading at which the first plane for one or more of the wheel track adjustment systems 10 will be the same as a second plane, which contains all the wheel axes. There will be at least a second particular loading at which the first plane for some or all the wheel track adjustment systems 10 will be the same. There will be also be at least a third particular loading at which the first plane for one or more of the wheel track adjustment systems 10 will be generally parallel to a third plane containing at least three of the contact points between the vehicle wheels and the ground, which is normally horizontal when the vehicle is on flat horizontal ground. Some of these loadings may be the same. A four-wheeled vehicle would have four such contact points.

The first and second swing arms 46,48 are mounted on the support bar 44 by way of first and second swing arm rings 50,52, respectively, at the first ends of the first and second swing arms 46,48. The swing arm rings 50, 52 are located within recesses in the first ends of the swing arms 46,48. The first and second swing arms 46,48 are themselves pivotally mounted on the first and second swing arm rings 50,52, respectively.

The first and second swing arm rings 50,52 are rotatably mounted at fixed positions along

the length of the support bar 44. Thus the first and second swing arms 46,48 are able to pivot and rotate relative to the support bar 44, in this embodiment each one rotating in a separate vertical plane when the support bar 44 is horizontal. The first and second swing arms 46,48 are pivotally mounted on the adjustment assembly mount 36, at the second ends of the first and second swing arms 46,48, but are otherwise fixed relative thereto.

The adjustment assembly mount 36 is located within recesses at the second ends of the swing arms 46,48, such that the swing arms 46,48 are separately attached to both the upper and lower plates 40A, 40B. The distance between the first ends of the first and second swing arms 46,48 is the same as the distance between the second ends of the first and second swing arms 46,48. The heights of the swing arms 46,48 are greater at their second ends than at their first ends, to accommodate the adjustment assembly mount 36.

The first and second swing arms 46,48 are of the same length and extend in parallel between the support bar 44 and the adjustment assembly mount 36. The first and second swing arms 46,48, the portion of the support bar 44 that extends between the first and second swing arms 46,48, and the portion of the adjustment assembly mount 36 that extends between the first and second swing arms 46,48 form a parallelogram linkage in the same first plane, and the swing arms 46,48 pivot relative to the adjustment assembly mount 36 in this same first plane. In the illustrated embodiment, the first plane also contains the wheel axis.

Actuator means, in this exemplary embodiment in the form of a linear actuator such as a hydraulic actuator 54 extend, between the support bar 44 and an attachment portion 56 on the first swing arm 46, around one third of the way along the first swing arm 46 from its first end to its second end. A first end of the actuator 54 is pivotally mounted on the first swing arm 46, but is otherwise fixed relative thereto. A second end of the actuator 54 is mounted on the support bar 44 by way of an actuator ring 58. The actuator ring 58 is rotatably mounted at a fixed position on the support bar 44. Thus the actuator 54 is able to pivot and rotate relative to the support bar 44.

The wheel track adjustment process of the wheel track adjustment system 10 is now described. This process is effected by the actuator 54, which is controlled by a

controller (not shown) and moves the wheel assembly 12 between the extended position as in Figures 1,3 and 5 and the retracted position as in Figures 2,4 and 6.

In Figures 1,3 and 5, the wheel assembly 12 is in the extended position, that is it is distanced further from the vehicle, more particularly from the first vehicle mount 16, than when it is in the retracted position. The first and second swing arms 46,48 are at an angle of about 60 degrees relative to the support bar 44, being angled outwards. The actuator 54 is in an extended position. The damper 18 is also angled outwards. The drive shaft 22 is telescoped out. From this position, the only adjustment to the wheel track width can be to narrow it, which means retracting the wheel assembly 12 towards the retracted position, as shown in Figures 2,4 and 6. However, the adjustment may not need to be all the way to the retracted position in all cases.

The actuator 54 is operable in provide a force in both directions. To enact retraction, the actuator 54 retracts. In this embodiment, the piston of the hydraulic actuator 54 is pushed (and/or pulled) into the cylinder of the hydraulic actuator 54. This action pulls the first swing arm 46 towards the actuator 54, and therefore towards the vehicle. Because the first end of the first swing arm 46 is fixed along the length of the support bar 44, the pulling of the attachment portion 56 of the first swing arm 46 pivots the first swing arm 46 inwards about the first end of the first swing arm 46. This tends to pull the second end of the first swing arm 46 inwards. Because the second end of the first swing arm 46 is mounted at a fixed point on the adjustment assembly mount 36, pulling the second end of the first swing arm 46 inwards pulls the adjustment assembly mount 36 towards the vehicle. However, the adjustment assembly mount 36 is kept parallel to the support bar 44 by the second swing arm 48. This is because the distance between the first ends of the first and second swing arms 46,48 is fixed, as is the distance between the second ends of the first and second swing arms 46,48. Those distances are also the same and the first and second swing arms 46,48 remain in parallel. Thus the wheel assembly 12 does not turn. Instead, since the adjustment assembly mount 36 is a component part of the wheel assembly 12, and the wheel assembly 12 is movable towards the vehicle, the wheel assembly 12 is pulled in to the vehicle. This also involves some movement of the wheel rotation axis. It moves in a parallel direction, without changing direction (unless there is a steering force from the tie rod 24), in a second plane, parallel to the first plane

containing the swing arms 46,48. During this motion the telescoping of the drive shaft 22 is reduced. Tolerances in the joint between the drive shaft 22 and the wheel 30 allow for the movement of the wheel in the direction parallel to the wheel rotation axis.

If the retraction process continues as far as it can, the wheel track adjustment system 10 ends up as it appears in Figures 2,4 and 6, at which point a straight line joining the first and second ends of the first swing arm 46 is substantially orthogonal to the main wheel axis, as is a straight line joining the first and second ends of the second swing arm 48. Since the first and second swing arms 46,48 are straight in this embodiment, the arms themselves are orthogonal to the main wheel axis. The main wheel axis here is the axis when the wheel is going straight, rather than being steered.

In Figures 2,4 and 6, the wheel assembly 12 is in the retracted position, that is it is distanced closer to the vehicle, more particularly to the first vehicle mount 16 ; than when it is in the extended position. The first and second swing arms 46,48 are at an angle of about 90 degrees relative to the support bar 44. The actuator 54 is in a retracted position.

The damper 18 is also angled outwards, but less so than in the extended position. The drive shaft 22 is not telescoped out. From this position, the only adjustment to the wheel track width can be to increase it, which means extending the wheel assembly 12 towards the extended position, as shown in Figures 1,3 and 5. However, the adjustment may not need to be all the way to the extended position in all cases.

The process of extension is the opposite of the retraction process. The actuator 54 pushes the attachment portion 56 of the first swing arm 46 away, thereby pivoting the first swing arm 46 away, which causes the second swing arm 46 to pivot away too, and pushing the wheel assembly 12 away. Again, the wheel rotation axis moves in a parallel direction, without changing direction, in the second plane, parallel to the first plane containing the swing arms 46,48.

In the extended or retracted positions or in between, the wheel 30 can be turned by the pushing or pulling of the tie rod 24, which pivots the wheel hub relative to the adjustment assembly mount 36.

The exemplary arrangement of the wheel track adjustment system 10 is for steering wheels. However, modifications can readily be made for non-steering wheels, for instance if the wheel hub were fixed to the adjustment assembly mount 36, rather than pivotable thereto.

Figures 7 and 8 are isometric views of a wheel track adjustment system 110 according to a second exemplary embodiment, for a non-steering wheel. Where the same reference numerals are used as in the first exemplary embodiment they refer to the same or similar components. This non-steering wheel system 110 of the second embodiment is mostly the same as that of the first embodiment and the relevant description of that first embodiment and its operation is applicable to the second embodiment.

The second embodiment differs in the arrangement of the wheel hub 132 and the adjustment assembly mount 136. The wheel hub 132 lacks the knuckle lever 34 and the tie rod 24. Instead a second pair of knuckle holders 134, in the vertical plane in the orientation as shown, are rigidly mounted onto the adjustment assembly mount 136 of the second embodiment and pivotally mounted onto the wheel hub 132. However, as the pivot mounting between the second pair of knuckle holders 134 and the wheel hub 132 is not in the same axis as the first pair of knuckle holders 38A, 38B and the wheel hub 132, the second pair of knuckle holders 134 prevents pivoting of the wheel hub 132 about the first pair of knuckle holders 38A, 38B.

The adjustment assembly mount 136 of the second embodiment has the opposing second knuckle holders 134 extending forwards, between the opposing upper and lower plates 40A, 40B, at the same level along the length of the adjustment assembly mount 136 as the first pair of knuckle holders 38A, 38B. The second pair of knuckle holders 134 is orthogonal to the first pair of knuckle holders 38A, 38B.

Extension and retraction of the actuator 54 in the second embodiment extends and retracts the wheel assembly 112 of the second embodiment in the same way as in the first exemplary embodiment. However, this second exemplary embodiment does not permit the wheel hub 132 to steer relative to the adjustment assembly mount 136.

Figure 9A is a top plan view of the outline of a vehicle 60, with four wheels 30 each with a wheel track adjustment system and all in the extended position. Figure 9B is a top plan view of the same vehicle outline, but with the four wheels 30 all in the retracted position. The front two wheel track adjustment systems 10 are steerable, as in the first exemplary embodiment. The rear two wheel track adjustment systems 110 are non- steerable, as in the second exemplary embodiment. The vehicle 60 is shown in outline only. The distance between the outsides of opposing wheels 30, which is the wheel track width, in the extended positions is WT1. The distance between the outsides of opposing wheels 30, the wheel track width, in the retracted positions is WT2. The difference between WT1 and WT2 is twice the distance through which each wheel extends from its retracted position to its extended position. With the embodiment illustrated in Figures 9A and 9B, extension and retraction of the wheel assemblies also results in a slight change in the wheelbase (distance between the wheels). However, if the four wheel track adjustment systems were all in the same direction, they would all move the same amount in the lengthwise direction of the vehicle and there would be no change in the wheelbase.

While Figures 9A and 9B show all four wheels being in the extended position and in the retracted position at the same time, they can be operated independently if desired (that is any one or more of them can be extended whilst the rest are retracted, or vice versa). While the maximum extension and retraction positions are the same in the Figures as shown, in a further alternative embodiment, the limits may be different between the front and rear wheels.

The suspension performance is substantially the same in both the extended and retracted positions. Moreover, the underneath vehicle clearance is substantially the same in both positions. The main change is in the wheel track width and thereby in the stability (as well as space needed).

The extension and retraction of the wheel assemblies (one for each wheel) normally takes place on the move, as the effects of friction, between the wheels and road, on the extension and retraction would then be negligible. However, with a sufficiently powerful actuator, extension and retraction can take place whilst the vehicle is stationary

When the wheel 30 bumps up and down, the damper 18 compresses or extends, as appropriate, whether the wheel assembly 12 is extended or retracted. Likewise the torsion bar 44 also provides some kind of damping. This makes the ride somewhat smoother. In alternative embodiments, the damper 18 may be removed, augmented or replaced.

Likewise the torsion in the torsion bar 44 may be removed, augmented or replaced. For instance, rather than having both a damper 18 and support bar 44 with continuously bias the wheel assembly 12 to a first height, one could have a purely damping function.

In the above embodiment the angle between the centre lines of the swing arms 46, 48 and the axis of the support bar 44 can vary, during retraction and extension from about 90 degrees to about 60 degrees. In other embodiments the angles at the extreme positions can be more extreme, for instance, at about 40 degrees at the fully extended position and/or for instance at 130 degrees or more at the fully retracted position. The extreme angles are limited by the construction, for instance the distance between the two swing arms 46,48 in the present embodiment (which limits how far out they can swing before they come into contact) and how far back the second swing arm 48 is from the wheel 30 (which limits how far in beyond the orthogonal the wheel assembly 12 can come before it comes into contact with the second swing arm 48. Extreme angles may also be limited by a desire to reduce movement of the wheel axis along the length of the vehicle. The swing arms 46,48 do not need to be straight or even the same, as long as they are sufficiently rigid and the same length between their two ends (that is between their points of contact between support bar 44 and the adjustment assembly mount 36). Thus, for example if at least the second swing arm 48 is curved away from the wheel assembly 12, it may be possible to retract the wheel assembly 12 further. Alternatively or additionally, if the first swing arm 46 is bowed out, away from the second swing arm 48, it may be possible to extend the wheel assembly 12 further. Another arrangement has the first and second swing arms in different planes so that, as they pivot, they cannot come onto contact with each other, for example with one above the support bar 44 and the adjustment assembly mount 36 and the other below the adjustment assembly mount 36.

The exemplary arrangement of the wheel track adjustment system 10 has a parallelogram arrangement between the support bar 44, the two swing arms 46,48 and the adjustment assembly mount 36. While a straight line between the two first ends of the

swing arms 46,48 should be parallel to a straight line between the two second ends of the swing arms 46,48, for there to be a parallelogram linkage, this does not mean that the support bar necessarily needs to be parallel to the adjustment assembly mount 36. They could be angled relative to each other. Alternatively, other mechanical structures (for instance with gear wheels or other non-slip contact surfaces) could be used during extension and retraction whilst maintaining the direction of the wheel rotation axis.

The first end of the actuator 54 is mounted on the first swing arm 46,146.

However, it could be mounted elsewhere, for instance on the second swing arm 48,148 or the adjustment assembly mount 36,136 or, in the second exemplary embodiment at least, on the wheel hub 132. The second end of the actuator 54 is mounted on the support bar 44. However, it could alternatively be mounted directly onto the vehicle. The mounting may include a ball-joint, so that the actuator 54 can pivot to allow for both vertical movement of the wheel assembly 12 and horizontal movement of the wheel assembly 12.

The mounting of the second end of the actuator 54 on the first swing arm 46 (or elsewhere) may be a ball joint, to allow for rotation of the swing arms 46,48 on the support bar 44. The actuator is shown as being in the same plane as the swing arms, which may be most efficient. However, in other embodiments, it may extend and push and pull in a different plane.

The actuator means is exemplified by a linear actuator, more particularly an hydraulic actuator. Other actuator means may be used, whether pneumatic or mechanical means such as cams, whether powered by motors or manually, and whether involving linear motion only or also rotation.

The wheel track adjustment system 10 is shown with a drive shaft 22 for the wheel 30, which passes through the first vehicle mount 16. This is for a driven wheel. For a non-driven wheel there would be no need for the external drive shaft 22. In a further alternative embodiment, an electric drive unit is used to power the wheel, the electric drive unit being disposed either within the wheel hub 32 or inboard.. As such there would also be no need for the external drive shaft 22 even for a driven wheel.

The maximum amount of extension and retraction mainly depends on the actuator 54 and the swing arms 46,48. These can readily be changed on a vehicle to vary the possible extension and retraction. Whilst the swing arms 46,48 have been shown as solid, they also may be telescopic. Pivoting of the wheel assembly 12 in such case can be prevented by a mechanism within the adjustment assembly 14 or between the first vehicle mount 16 and the wheel assembly 12.

The described embodiment and variations on it can be used to provide a vehicle with an adjustable wheel track width, such that it can be reduced for transportation in a narrow enclosure or narrow road and widened for improved stability, mobility, ride and handling. The described embodiment and variations on it allow constant ground clearance, whether extended or retracted. The described embodiment and variations on it use a suspension assembly that is compatible with either conventional drive from a central engine or localised drive units associated with individual wheels. The described embodiment and variations on it require a minimal amount of lateral intrusion into the vehicle compartment.