The present invention relates to a retractable deflector, particularly to a retractable deflector for reducing drag.

BACKGROUND TO THE INVENTION

Moving vehicles experience drag as they pass through air or water, with drag increasing significantly as velocity increases. A vehicle such as an articulated truck, for example, will experience large drag when moving, particularly at any speed in excess of urban speeds (typically 20-30 mph), partly from its tractor and partly from its trailer. This results from its aerodynamically poor shape, which can be typically flattish fronted or has a front which can be aerodynamically improved. This serves as a purposeful compromise to increase cargo volume, due to regulatory restrictions on truck dimensions. As drag acts against a vehicle, additional fuel must be used to maintain a given speed, whether the vehicle travels by land, sea or air. Increased fuel consumption is both expensive and environmentally unfriendly, increasing operating costs and pollution. It is well known to fit devices to vehicles to produce an aerodynamic effect, for example, increasing the ground pressure of a vehicle at high speeds, or reducing drag. Rear spoilers may be fitted to more sports oriented cars to increase the grip of the rear wheels, minimising the likelihood of oversteer. In vehicles for carrying goods such as trucks, devices can be fitted above the cab to reduce the drag created by a large flat- fronted trailer behind the tractor. Some trailers have a tapered upper surface to reduce drag, whilst others have rear tails, low side flaps or undercarriage devices for similar reasons.

However, even using devices such as those mentioned above, drag remains a significant factor, resulting in unnecessarily high fuel consumption. Additionally, a truck cab moving with or without a trailer will still experience large drag, especially when fitted with a nose that has significant room for aerodynamic improvement. Some new vehicles may be designed with some aerodynamic considerations towards shape in order to conserve fuel, but many older vehicles with poor aerodynamic profiles remain in use across the globe.

It is an object of the present invention to reduce or substantially obviate the aforementioned problems.

STATEMENT OF INVENTION

According to the present invention, there is provided a retractable deflector for mounting to a front of a vehicle comprising at least first and second support members, and a fabric cover securely extending between the first and second support members, the first and second support members being movable between a stowed position, in which the cover is disposed in a collapsed state between the support members, and a deployed position, in which the cover is stretched between the first and second support members and forms a three-dimensional deflector.

The fabric cover may be resilient, enabling it to be stretched and extended in size in a deployed position and to retract to a reduced size in the stowed position. The fabric cover may extend over the first and second support members, as well as between them.

When in the collapsed state, the cover may lie flat between the support members, for example, against or proximate to the front of the vehicle.

When in the deployed position, the cover may be held taut over and/or between the support members.

Components of the retractable deflector may be made from any material, or combination of materials, including (but not limited to): textiles, metals, alloys, plastics, polymers, advanced composites, wood, or cardboard. For example, the fabric cover may be made from metals or plastics. The deflector may be resilient. Attachment means may be provided to attach the retractable deflector to at least one of the following portions of the vehicle: a front surface, a top surface, a side surface, a bottom surface. Alternatively, the deflector may be integral to at least one of the aforementioned portions of the vehicle, being incorporated into an engine compartment at the front of the vehicle, for example.

Providing attachment means for the deflector allows it to be retrospectively fitted to any one of a variety of pre-existing vehicles with a poor aerodynamic shape, such as a flat-fronted vehicle. It can also be incorporated into vehicle designs for future production to improve its base aerodynamic profile. Airflow can be optimised over multiple surfaces of the vehicle, whether it is mounted to the front or sides of a vehicle, atop it, or to its undercarriage, or a combination of these. Alternatively, the deflector may be fully integrated, i.e. built into the vehicle. This prevents the deflector from being stolen, and air intakes, for example, can be designed to duct into areas outside the deflector to avoid issues with engine cooling and air supply. It can also be customised to the shape of the vehicle, potentially optimising aerodynamic efficiency to a greater extent than a standard mounted deflector.

Each support member may include or be a mechanised strut.

This allows the deflector to deploy even when the vehicle is already moving, as the mechanised struts can forcibly extend the support members and fabric cover against the force exerted by the oncoming air. The mechanised struts hence support remote and automatic activation of the deflector, so that a driver need not manually deploy the deflector prior to starting a j ourney .

At least one bridge may be provided between the first and second support members, each bridge substantially preventing the collapse of the fabric cover between the support members when the deflector is deployed and in use.

At high speeds, the fabric cover is liable to deform to some extent between the first and second support members when the deflector is deployed, as the pressure of the onrushing air will be able to partially distort its shape due to the elasticity of the fabric. As such, the aerodynamic efficiency of the deflector may reduce, increasing drag on the vehicle. By providing one or more bridges beneath the fabric cover between the support members, distortion or total collapse of the fabric (i.e. material failure) is substantially mitigated, maintaining the deflector substantially in its designed shape at speeds in excess of urban speeds when deployed, at motorway speeds for example.

The fabric cover may be further secured to one or more additional support members. The deflector may include at least one side fabric cover secured to at least one of the support members. Each side fabric cover may be stretched taut between multiple support members, or multiple portions of the same support member.

The addition of additional support members and/or side fabric covers enables the deflector to be modulated into a more complex aerodynamic shape, further reducing drag by increasing the efficiency with which the deflector displaces air around the vehicle. Using additional support members also means that the fabric cover remains largely effective even if detached from one support member due to a minor collision, for example, rather than failing completely if only two supports were present.

Each side fabric cover may have one or more reinforcements that substantially prevent its collapse when the deflector is deployed and in use.

This maintains improved airflow around the sides of the vehicle for similar reasons to the main fabric cover described above.

The or each fabric cover may be breathable, allowing some air to pass through it. At least one fabric cover may be a mesh.

Having a breathable fabric allows air to reach the vehicle's engine for combustion, mitigating engine stalls due to oxygen starvation of the engine, given that the deflector may be mounted to the grille where air intakes are commonly located. It also permits air cooling of the engine to prevent over-heating. For example, a mesh has small apertures in its body suitable for allowing the ingress of air at ambient speeds, when the vehicle is stationary and the deflector is in its retracted (or stand-by) position, or alternatively ingress of a portion of oncoming air when the vehicle is in motion. When deployed, the mesh is stretched and its apertures may increase in size, ensuring the ingress of air is not substantially impeded relative to its retracted position. A breathable fabric or mesh is also typically lightweight and will retain minimal moisture if wetted, ensuring that the fabric does not deform permanently if used at high speeds in wet conditions.

The deflector may be remotely operable using one or more manual controls, allowing deployment and retraction of the deflector. The deflector may operate automatically based on vehicle velocity, deploying above a first threshold value and retracting below a second threshold value. Preferably, vehicle velocity may be determined by a sensor unit connected to the deflector, where the sensor unit may include at least one of the following: an anemometer, a speedometer, an odometer, or another similar device.

Manual control of the deflector allows it to be deployed and retracted at will, to decrease drag or protect the deflector from damage, for example. Automatic operation of the deflector can also be advantageous, as drag is reduced at higher speeds without requiring user intervention due to its automatic deployment, hence forgetfulness is mitigated. Automatic retraction is also useful, as the fabric is stretched taut when the deflector is deployed, and much easier to damage, even at low speeds. The sensor unit may include a delay timer to postpone automatic deflector operation. The delay timer may postpone deployment of the deflector until vehicle velocity has reached or exceeded the first threshold value for at least a first period of time. The delay timer may postpone retraction of the deflector until vehicle velocity has fallen below the second threshold value for at least a second period of time.

Advantageously, the delay timer prevents unnecessary transitions of the deflector between deployed and stowed states, where vehicle velocity is fluctuating around the threshold values, as the transition between states is not instantaneous. This prevents unnecessary increases in drag, and hence fuel consumption, during a journey at roughly constant speed similar to the threshold speeds, changing the deflector configuration only where a change in speed across the threshold is maintained more than momentarily. The deflector only deploys when the vehicle increases speed to reach or exceed the upper threshold speed. This is because drag reduction generally results in appreciable fuel savings at higher speeds, whereas the deflector can affect manoeuvrability at low speeds by increasing the turning circle required by the vehicle due to its increased length. Similarly, the deflector only retracts when the vehicle reduces speed to below the lower threshold speed, and remains below the threshold for an appreciable period of time. This prevents momentary reductions in speed, e.g. slowly braking to allow a vehicle to join from a slip road, from unnecessarily retracting the deflector, when the vehicle will attain its previous higher speed in short order.

Furthermore, there is generally less room between vehicles at low speeds or when stationary, in a traffic jam, for example. Therefore, retracting the deflector at low speeds ensures that it is not damaged due to vehicles being in close proximity, whilst at higher speeds it can be deployed without taking excess road space, as the distances between vehicles are larger, on average, when the vehicles are travelling at higher speeds.

Activation of the manual controls may be used to override the automatic operation of the deflector. This allows the deflector to be deployed at lower speeds than required for automatic deployment, as it will still reduce drag to a small extent. This also allows the deflector to be retracted at higher speeds than required for automatic retraction, if circumstances require it. For example, hail stones might damage the deflector when deployed on the motorway.

The deployed position of the deflector may be variable based on the shape of the vehicle.

This allows the deflector to be customised to the specific shape of the vehicle it is mounted to, deflecting airflow around the vehicle in the most effective manner, i.e. reducing drag to the greatest extent. This can be automatically calibrated by the deflector based on airflow measurements in situ, or the support members can be manually adjusted to deploy to a fixed extent. Alternatively, the deflector can allow electronic input of the make and/or model of the vehicle, automatically adjusting the extent to which it protrudes from the vehicle when mounted and deployed.

The deflector may have one or more lights. Preferably, the lights activate automatically when ambient light levels fall below a first threshold level, and deactivate automatically when ambient light levels rise above a second threshold level. The lights may be controllable by a manual activation switch.

The deflector may not necessarily be stowed when the deflector-mounted vehicle stops moving, if temporarily parking a truck at a service station, for example. As the deflector artificially lengthens the vehicle it is mounted to, it may be prone to damage, if another driver unknowingly reverses their vehicle into it, for example. Providing lights on the deflector increases its visibility to other people, minimising the likelihood of accidental damage being incurred in the manner described.

The lights automatically activate in dim conditions to ensure the deflector is always clearly visible, at dusk or at night, for example. This is facilitated by integrating a light sensor into the sensor unit, and setting the activation threshold to correspond to darker conditions, and the deactivation threshold to correspond to brighter conditions. Manual control of the lights is advantageous where automatic control is faulty, or not present.

The deflector may have one or more reflectors.

Having reflectors on the deflector will increase the likelihood of other drivers to noticing it in a similar manner to having lights, as explained above, minimising the chances of the deflector sustaining damage from other vehicles.

The deflector may be built into an engine compartment of a vehicle, being stored within the compartment when stowed and protruding from the compartment when deployed. In other words, the deflector may materialise from the engine compartment when transitioning from a stowed state to a deployed state. BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made by way of example only to the accompanying drawings, in which:

Figure 1 shows a perspective view of a first embodiment of a retractable deflector mounted to the front of a truck cab in a deployed configuration; Figure 2 shows a perspective view of the retractable deflector of Figure 1 mounted to the front of a truck cab in a stowed configuration;

Figure 3 shows a front view of the retractable deflector of Figure 1 mounted to the front of a truck cab in a stowed configuration;

Figure 4 shows a perspective view through the retractable deflector of Figure 1;

Figure 5 shows a side profile of the retractable deflector of Figure 1; Figure 6 shows a graph illustrating the variance in drag experienced at different speeds by a truck with and without the deflector of Figure 1, tested using a scale model one fifth of the full size of a standard truck;

Figure 7 shows a front view of a second embodiment of retractable deflector mounted to the front of a tractor unit in a stowed configuration; and

Figure 8 shows a perspective view of the retractable deflector of Figure 7 mounted to the front of a tractor unit in a deployed configuration. DESCRIPTION OF PREFERRED EMBODIMENT(S)

Referring firstly to Figures 1 to 3, a first embodiment of a retractable deflector is indicated generally at 10, mounted to the front of a truck cab which is indicated generally at 100. In Figure 1, the deflector 10 is shown in its deployed configuration, mounted beneath the windscreen and over the grille of the cab 100. Figure 2 shows the deflector 10 in a stowed position for comparison. The deflector has been retro-fitted to the existing cab 100, extending across the majority of the width of the cab 100 to optimise airflow around the sides of the truck cab 100. The deflector 10 does not obscure driver visibility, the headlights, the windscreen wipers, or the number plate.

The deflector 10 includes a first support member 12 and a second support member 14, with a fabric cover 16 stretched taut over the first and second support members 12, 14 like a shell. This makes the deflector lightweight as it is predominantly hollow inside. The support members 12, 14 are made from plastics, but may be of lightweight metal or alloy. The support members 12, 14 roughly follow the contours of the truck 100 at its front, with the members 12, 14 each having an approximately hyperbolic shape for the portion which can extend away from the truck 100, seen most clearly in Figures 3 and 5. The support members 12, 14 are external in this embodiment, but additional embodiments are envisaged in which they are disposed internally relative to the fabric cover 16, or incorporated within the fabric cover 16. Furthermore, the support members 12, 14 may be telescopic struts in other embodiments.

The fabric cover 16 is perforated with holes to permit air through the deflector, allowing air to supply the combustion engine of the truck 100, as well as providing air cooling where necessary. In other words, whether the deflector 10 is deployed or retracted (in a stand-by mode), it allows adequate air to reach the engine. Additionally, as can be clearly seen in Figures 1 and 2, the deflector 10 does not obscure the exterior front lights of the truck 100, nor does it obscure the driver's vision, whether or not deployed. The fabric cover 16 is also resilient, being elastically deformed during deployment of the first and second support members 12, 14, and allowed to relax to its smaller native non- stretched dimensions when the support members 12, 14 are retracted. The fabric cover 16 may be multi-layered to facilitate repeated transitions between deployed and stowed states without incurring substantial wear. It should be noted that the term 'fabric cover' is to be interpreted as referring to a thin and somewhat flexible skin, and may be composed of various materials including, but not limited to, textiles, plastics, polymers, metals, and advanced composites. For example, the fabric cover in this embodiment is an elasticated mesh with a polymeric outer coating, providing durability against wear in addition to conferring resilience. As seen in Figure 3, the fabric cover 16 extends from the top of the deflector to the bottom. The fabric cover 16 peaks at the front of the truck cab 100 in a rounded apex. This allows the support members 12, 14 to fold towards each other in the stowed state without overlapping. The 'blunt' rounded apex is preferable to a sharp leading edge, as sharp edges may disrupt airflow relative to rounded edges. Sharp edges may also create vortices, increasing local air turbulence and drag relative to rounded edges.

With the deflector deployed, oncoming air is displaced over and beneath the truck 100 to a greater extent than by the truck cab 100 alone (i.e. without the deflector 10 mounted at its front), as the deflector 10 re-directs airflow around the truck cab 100 to reduce air resistance. It will be appreciated that other embodiments of deflector may have a maximum depth of greater or less than the present deflector, in order to minimise the drag experienced by a given vehicle. In other words, the deflector 10 can be adjusted to optimise airflow over different vehicles of various dimensions. This can be effective for any vehicle irrespective of whether it travels by land, sea or air.

The deflector 10 further includes a first side cover of fabric 18, and a second side cover of fabric 20, disposed on either side of the fabric cover 16. This creates a central region which is wedge shaped, but also has angled sides, therefore effectively having four angled faces to displace air around all four sides (top, bottom, left and right) of the truck 100. The nose of the deflector is rounded and shorter in width than the width immediately adjacent the truck. The first side cover 18 is secured to the first support member 12. The second side cover 20 is secured to the second support member 14. These side covers 18, 20 are also stretched taut to improve airflow around the sides of the truck 100, streamlining its shape to enhance its aerodynamic profile and minimise drag further. When the deflector 10 is deployed, the angle of each side cover 18, 20 to the front of the truck 100 is substantially similar to ensure that the vehicle does not experience a significant and sustained difference in drag between its right- and left- hand sides, which would impair handling. In this embodiment, the angle of each side cover 18, 20 is approximately 45°, but it will be appreciated that various angles may be used depending on the vehicle in question. Referring also to Figures 4 and 5, the deflector 10 is presented independently of a vehicle. The first support member 12 is fixed to a first hinge pin 22. The first hinge pin 22 is mounted between a first upper hinge 22a and a first lower hinge 22b. Similarly, the second support member 14 is fixed to a second hinge pin 24. The second hinge pin 24 is mounted between a second upper hinge 24a and a second lower hinge 24b. The first hinge members 22a, 22b each have an internal motorised mechanism (not shown) which can rotate the first hinge pin 22 about its axis, moving the first support member 12 between deployed and stowed positions. The second hinge members 24a, 24b also have internal motorised mechanisms (not shown) for rotating the second hinge pin 12 and second support member 14 in the same manner. The mechanisms lock the support members 12, 14 in position when deployed, preventing air pressure from collapsing the deflector 10 to its flat stowed shape. The mechanisms also allow the deflector 10 to be deployed to various extents, i.e. having various maximum depths as measured from the rounded apex, as mentioned above, locking the deflector 10 in position in each case.

Through the fabric cover 16, three bridge members 26a, 26b, 26c are visible. The fabric cover 16 of the deflector 10 in Figure 4 is normally opaque, but has been made artificially translucent to highlight additional structures, such as the bridge members 26a, 26b, 26c. The translucence of the fabric cover 16 may vary inclusively between substantially transparent and opaque in other embodiments according to its material, and the frequency and distribution of any apertures through its surfaces.

These are strung taut between the first and second support members 12, 14 when the deflector 10 is deployed. Each bridge member 26, 26b, 26c is a cable that substantially supports the underside of the fabric cover 16 at or near its rounded apex. Each bridge member 26a, 26b, 26c is distributed symmetrically about the apex, maintaining the tautness of the fabric cover under the pressure of air when the vehicle is moving. When retracted, the bridge members 26a, 26b, 26c lose their tautness and allow the fabric cover 16 to shrink to its natural non-stretched dimensions, with the bridge members 26a, 26b, 26c also returning to smaller dimensions.

It will be appreciated that, in other embodiments, the bridge members may be disposed on the outer side (or both sides) of the fabric cover, or incorporated into the fabric cover itself. Similarly, there may be fewer or greater numbers of bridge members strung between support members, and these may support the fabric cover at different points to those shown in Figure 4. Furthermore, there may be bridge members strung between two points on the same support member, providing structural support to the or each side cover. The bridge members may also be thicker or thinner than depicted, and may vary in form from the cables described; for example, they may be telescopic struts, or they may be elasticated.

A stabilising panel 28 is visible most clearly in Figure 5. This fills the gap beneath the lower portion of the deflector which angles away from the hinge members, supporting it to avoid placing undue strain on the hinges. A panel is provided at both ends of the deflector and effectively forms a lower fairing. At the top of the deflector 10, a small flap 30 extends upwardly to condition airflow over the deflector 10, preventing the hinge member 22a from disrupting the flow. Another flap is also present on the other side of the deflector 10 for the same reason.

The support member 12, as seen in Figure 5, has an upper leading edge 12a and a lower leading edge 12b. The leading edges are asymmetric across a horizontal plane taken through the rounded apex 32. This deflects air upwards and downwards in proportionate amounts to maximise drag reduction, the asymmetry being based on the mounting position of the deflector 10 to the front of the truck 100. Alternate shapes of deflector may be used in which the leading edges have different asymmetry, or in which they are symmetric.

Figure 6 shows a graph comparing drag (in Newtons, N) as a function of the speed of air in a wind tunnel (in miles per hour, mph) for a 20% scale model of a truck. The uppermost curve shows how drag varies with speed when the flat-fronted scale model is placed in the wind tunnel without a deflector, whilst the lower curve indicates the drag for equivalent speeds with the deflector fitted to the front of the model. Polynomial curves (order 2) are fitted to the data, showing that drag is relatively proportional to speed for the scale model, as expected. Based on the experimental data, the deflector is directly responsible for a reduction in total drag of between 17% and 19%, which would correspond to an increase in fuel efficiency of over 11% (in terms of miles per gallon (mpg)) for equivalent results at full scale. Although the exact changes to drag reduction when scaled up to the size of a real truck may vary to a degree, it is clear from the data that drag is significantly reduced by the deflector.

In use, the deflector 10 is mounted to the front of a vehicle whilst it is stationary. When the vehicle is moving, the motorised mechanisms 22a, 22b, 24a, 24b can pivot the support members 12, 14 away from the vehicle to deploy the deflector 10. This stretches the fabric cover 16 taut, deflecting air around the vehicle to reduce drag. In addition, the detector automatically deploys at or above a threshold speed of, for example, 25 mph in this embodiment, although this may be altered to another value in other embodiments, such as 30 mph, for example. In this case, there is no delay prior to deployment commencing once the vehicle has reached or exceeded the exemplary speed of 25 mph (or another pre-set speed), although this may vary in other embodiments. Conversely, if the vehicle slows when the deflector is already deployed, the threshold speed at which the deflector is stowed is, for example, 20 mph, although this may vary in other embodiments. The velocity of the vehicle is measured by an anemometer (not shown) built into the deflector 10. Additionally, there is a delay of five seconds prior to commencing retraction, to ensure that the speed reduction is not transient, although this may also vary in other embodiments. An additional advantage of the deflector is that it acts as a relatively soft area, in case the vehicle collides with a person. This may reduce the severity of any injuries they sustain, and may prevent substantial damage being incurred to the vehicle as well. Referring now to Figures 7 and 8, a second embodiment of deflector is indicated generally at 200 mounted to a vehicle 110, in particular to the front of a tractor unit, in the stowed and operative positions respectively. The operative components causing movement of the deflector are similar to those of the first and other embodiments. The deflector 200 takes the same overall shape as the deflector 10 of the first embodiment, having two forward surfaces 202, 204 at an angle to one-another and joined centrally at a rounded apex 206, when in the operative position. The width of the apex 206 is narrower than the width of the surfaces 202, 204 in proximity to the vehicle 100. As in the first embodiment, the fabric of the surfaces 202, 204 is mounted to support members 212, 214 on either side. The support members 212, 214 are hingedly mounted to the front of the tractor unit, about an axis lying offset to the vertical by around 10 degrees. The position of the support members 212, 214 is designed to fit with the shape of the bodywork on the front of the tractor unit and hence the side members are further apart at the top than at the bottom.

Each of the side members 212, 214 in this embodiment includes a straight rear member 216, which is pivotally mounted to the bodywork of the front of the tractor 110 and lies substantially parallel to that portion of the bodywork. Above this a further rear member 218 continues, but is angled outwardly from the vehicle, for example, by around 10 degrees, or so. The further rear member is of shorter length, around a third of the length of the rear portion 216. The upper end of the further rear member is connected to the lower end of the rear member by a substantially "V" shaped front member 220, with a bull nose 222 at the apex of the "V". A support strut 224 extends laterally from the junction of the rear member 216 with the further rear member 218, across the side member 212, 214 to the upper side of the V-shaped front member 220, i.e. above the bull nose 222, when in use on the vehicle. In this embodiment, breathable fabric or a solid material, such as plastics or sheet metal extends between the supporting members of the side members 212, 214 to effectively form side panels. Although air can pass through fabric, it is envisaged that on some vehicles the airflow through the front grills of the vehicle may be too restricted when the vehicle is travelling at very low speeds, for example, in traffic jams, and when the deflector is in the stowed position with the fabric in close proximity to the air vents or intakes on the front of the vehicle. If the panels are solid, there is no airflow. For this reason, a pair of lateral cut outs 226, 228 are provided in the fabric or sheet covering , which are designed to overlie the vehicle air vents or air intakes when the deflector is stowed.

The cut-outs are reinforced with an outer frame having curved corners to reduce stress fractures and are covered in an open mesh to prevent ingress of foreign objects, particularly birds. The mesh has very little restrictive effect on airflow through the cut- outs and hence the vehicle cooling is substantially unaffected by the deflector. Typically the mesh may have repeated apertures of 100mm square in area or greater.

The fabric of the forward surfaces 202, 204 of the deflector between the side members 212, 214 is manufactured with seam lines, which facilitate predictable and repeatable folding of the fabric as the deflector moves from the operative to stowed positions. The fabric folds along the seams and is biased so that it does not fold under the lateral cut outs 226, 228. At the centre of the deflector, particularly near the bull nose front of the deflector, the fabric may be seamed so that it folds or collapses in the manner of a concertina.

The term "substantially flat" applying to the fabric when it is in the stowed position is intended to include within its scope fabric which is "collapsed, gathered, concertinaed, and/or folded on itself.

In both embodiments, the support members 12, 14 are constructed from a rigid material, such as plastic or metal. Further embodiments are also envisaged in which alternatively shaped support members are used, such as parabolic or more angular support members, for example. Yet more embodiments are contemplated in which the deflector is substantially springy, where it is forcibly compressed when stowed, and expands to its natural dimensions when allowed to deploy.

It will also be appreciated that, within the scope of the claims, other embodiments of deflector may be attached to the sides, top and/or base of a truck to minimise drag on a vehicle. The deflector may be integral to the structure of the vehicle being used, rather than appended after construction. For example, the deflector may be built into and deployable from the engine compartment. Furthermore, other alternate embodiments may include different mechanisms for deploying the deflector, such as the use of manually operated support members, or a motorised telescopic framework including first and second support members, for example. The user may be able to manually input the type of vehicle being used and type of journey envisaged, allowing the deflector to deploy based on a pre-determined optimal set of parameters. The user may also be able to input preferred threshold speeds and delay times to the deflector. In addition to the speed-sensing means discussed above, the speed at which the deflector and vehicle are moving may be determined by various other means. This includes but is not limited to direct or derived measurements based on variations in GPS location, or laser-based speed measurements (from lasers mounted to the deflector). The embodiments described above are provided by way of example only, and various changes and modifications will be apparent to persons skilled in the art without departing from the scope of the present invention as defined by the appended claims.