NZ731138A - A moveable irrigator - Google Patents

Abstract

A moveable irrigator (1) having a wheeled support structure and a plurality of deflectors (10) of such a size, distribution and orientation as to apply a stabilising downforce on an upwind side or a stabilising upforce on a downwind side to the support structure when exposed to the force of incident wind. The invention reduces the risk of an unanchored mobile irrigator toppling over when subjected to forces caused by incident winds.

Description

A MOVEABLE IRRIGATOR FIELD OF THE INVENTION The invention relates to moveable irrigators. More particularly but not exclusively, the invention relates to a moveable irrigator including a plurality of deflectors configured to apply a ising force to the irrigator when exposed to the force of incident wind.

BACKGROUND TO THE INVENTION tors are used in agriculture to apply water and/or nts to land. In sprinkler-type irrigators water is piped to a location within the field and distributed through overhead highpressure outlets.

Moveable/wheeled tors often include te pipes supported on wheeled towers with sprinklers positioned along the pipes. These sorts of irrigators travel along a field to irrigate across the surface area of the field. These may be center-pivot, or linearly moving irrigators.

A problem with such irrigators is that they are susceptible to being tipped over in strong winds. This may damage or completely y the irrigator, resulting in a loss of time, money and productivity.

Mechanical anchors are used to secure irrigators against wind. However, irrigators are action when they are anchored to the ground. Further, it is not always possible to anticipate when there will be strong winds. It can be time consuming and enient to install such anchors every time there is strong wind, and later remove them when the wind is over.

Other solutions have been suggested employing on-board weights. However this can increase the weight of the irrigator to such an extent as to cause structural damage to the irrigator in wind events. It might also cause the irrigator to sink into and become stuck in soft ground or make wheel ruts deeper over time which costs productivity.

Extending the irrigator’s wheel base to lower its center of gravity may minimise the chance of an irrigator g over in strong wind. However, this has the disadvantage that the extended wheel base may prevent the irrigator from being positioned close to fences, highcrops or other ground obstacles.

It is an object of the invention to provide an improved irrigator or to at least provide the public with a useful choice.

Reference to any prior art in this specification does not constitute an ion that such prior art forms part of the common general knowledge.

SUMMARY OF THE INVENTION In a first aspect the invention provides a moveable irrigator having a d support structure and a ity of deflectors of such a size, distribution and orientation as to apply a stabilising downforce on an upwind side or a stabilising upforce on a downwind side to the support structure when exposed to the force of incident wind.

Deflectors may be provided on an upwind and/or downwind side.

Preferably one or more of the deflectors are wings.

Preferably one or more of the deflectors e a flat surface.

Preferably one or more of the deflectors are configured to pivot to a on in which they provide a diminished upforce.

Preferably one or more of the deflectors include a cambered surface.

Preferably one or more of the deflectors include leading edge slats.

Preferably one or more of the tors include two opposing inflections at opposing ends of the deflectors.

Preferably one or more of the deflectors pivot about a vertical axis.

Preferably one or more of the deflectors include a tail vane.

Preferably one or more of the deflectors are outwardly displaced from the longitudinal axis of the tor Preferably one or more of the tors are displaced beyond one or both sides of the support structure.

Preferably the deflectors are symmetrically arranged on both sides of the support structure.

Preferably one or more of the deflectors are arranged at or near the wheels of the irrigator.

Preferably the one or more deflectors are ally elevated relative to the support structure.

Preferably the irrigator is a centre-pivot irrigator.

Alternatively the irrigator is a linearly moving irrigator.

Preferably the deflector has anhedral.

In r ment, the invention provides a deflector for a moveable irrigator having a wheeled support structure wherein the deflector is of such a size, shape and orientation as to apply force to the support structure when exposed to the force of incident wind.

BRIEF PTION OF THE DRAWINGS The invention will now be described by way of example only, with reference to the accompanying drawings, in which: Figure 1 Shows a ctive view of a moveable irrigator according to an embodiment of the invention.

Figure 1b Shows a top view of the irrigator of Figure 2.

Figure 2 Shows a cross section of a deflector in the form of a wing.

Figure 3 Shows a side view of a support structure of an irrigator according to an embodiment of the invention.

Figure 4 Shows a side view of a support structure of an irrigator according to another ment of the ion.

Figure 5 Shows a side view of a support structure of an irrigator according to another embodiment of the invention.

Figure 6 Shows a side view of a support structure of an irrigator according to another embodiment of the invention.

Figure 7 Shows a side view of a support structure of an irrigator according to another embodiment of the invention.

Figure 8a Shows a side view of a support structure of an irrigator according to another ment of the invention.

Figure 8b Shows a top view of the embodiment shown in Figure 8a.

Figure 9a Shows a side view of a support structure of an irrigator according to another ment of the invention.

Figure 9b Shows a top view of the embodiment shown in Figure 9a.

Figure 10a Shows a side view of a support structure of an irrigator according to another embodiment of the invention.

Figure 10b Shows a top view of the wing shown in Figure 10a.

Figure 10c Shows a side view of the wing shown in Figure 10a.

Figure 11a Shows a side view of a support structure of an irrigator according to another embodiment of the invention.

Figure 11b Shows a top view of the wing shown in Figure 11a.

Figure 11c Shows a side view of the wing shown in Figure 11a.

Figure 12 Shows a side view of a support ure of an irrigator according to another embodiment of the invention.

Figure 13a Shows a top view of a support structure of an irrigator according to another embodiment of the invention.

Figure 13b Shows a top view of the wing shown in Figure 13a.

Figure 13c Shows a side view of the vane shown in Figure 13b.

Figure 14a Shows a top view of a support structure of an irrigator according to r embodiment of the invention.

Figure 14b Shows a top view of the wing shown in Figure 14a.

Figure 14c Shows a side view of the wing shown in Figure 14b.

Figure 14d Shows a deflector in the form of a delta shaped wing.

Figure 15 Shows a side view of a support structure of an irrigator according to an embodiment of the present invention.

Figure 16 Shows a side view of a support structure of an irrigator according to another embodiment of the present invention.

DETAILED DESCRIPTION Figure 1a shows a perspective view of a le irrigator ing to an embodiment of the invention. The irrigator 1 includes a pipe 2 ted by a wheeled support ure and surrounded by a network of trusses 6 and bracing 5. In this embodiment, the wheeled support ure includes a hub 3 and numerous towers 4. The towers include wheels 8 connected to stays 7 which support the pipe. The irrigator 1 also includes a number of deflectors 10 supported on supports 9. The deflectors will be described in detail below.

The irrigator 1 in the shown embodiment is a center-pivot irrigator, which rotates about the hub 3, such that it waters a ar area with a radius equal to the length of the irrigator 1.

Although this invention is described with reference to a center pivot irrigator the invention is not limited in this respect. For example, the invention may also be applied to laterally moving irrigators (also known as , side roll or wheel line irrigators) or any other suitable type of tor. Irrigators may be of any suitable length, and include any suitable number or uration of support structures. The invention is particularly applicable to wheeled/moveable irrigators, as in use, these are ed to move across a field and are not secured to the ground.

Deflectors The deflectors 10 are ured to be of such a size, distribution and orientation as to apply downward force to the irrigator’s support structure when exposed to the force of incident wind. Thus the deflectors 10 act to reduce drag-induced tipping moment which may cause irrigators to fall over. Preferably, the deflectors 10 are wings angled to apply a downforce to the support structure when exposed to the force of incident wind. A wing is surface configure to generate aerodynamic force when appropriately presented to moving air, in this case, wind. “Deflector” includes a wing as well as surfaces that may not provide lift. The term “deflector” es wings and other elements that may apply stabilising force to an tor when exposed to incident wind.

Terminology For the avoidance of doubt, where in this specification the following terms are used they have the following meaning.

Downforce: downward force ted by a wing when it is disposed at a negative angle of attack to the wind in the ntal plane.

Upforce: upward force generated by a wing when it is disposed at a positive angle of attack to wind in the ntal plane.

Drag: refers to aerodynamic forces acting on objects in a wind stream and in the direction of that wind. The drag force on wings and their supporting structure is the “price” that is paid for the downforces/upforces generated by these wings.

Chord: The chord of a wing is the line through the wing from the leading edge to the trailing edge. Figure 2 shows a wing with leading edge 13, trailing edge 14 and chord 12.

Camber: The asymmetry between the top and the bottom es of a wing.

Tipping moment: the tipping moment (which can be measured in newton-metres) ted by wind striking the superstructure of an irrigator.

Angle of attack: the angle between a line drawn through the leading edge 13 and trailing edge 14 of a wing section and the wind direction in the chordwise sense. Figure 2 shows an exemplary wing disposed at angle of attack α.

Lift coefficient: A measure of wing lift (upforce or downforce) per unit area Aspect ratio: The span of the wing squared divided by its area.

Wing angle of attack Preferably, the wings 10 are angled to e a downforce on the upwind side the irrigator 1, and upforce on the downwind side of the tor 1.

The efficiency of a wing can be measured by its lift/drag ratio. The lift/drag ratio of a wing is most strongly a function of the wing’s angle of attack. Lower angles of attack generally result in greater wing ency, however this also es a lower lift coefficient.

Particularly strong winds may have substantial vertical velocity components at times. In these circumstances, a wing with a low angle of attack (by nce to the horizontal) may experience a momentary angle of attack reversal and generate upforce when required to provide a downforce and vice versa.

Therefore, it may be desirable that wings of the present invention have an angle of attack towards the upper end of their useful angle-of-attack range. Preferably, the deflectors of the present invention will have angles of attack of between 15 to 20 s, however the invention is not limited in this respect.

As will be discussed later in the specification, other wing features such as leading edge slats, camber and multiple planes may be used to enable the higher lift coefficients associated with higher angles of attack while retaining acceptable lift/drag ratios.

Aspect ratio Preferably, the wings 10 will have an optimised size/aspect ratio such as to prevent the irrigator 1 from falling over in strong winds. Generally, the higher the aspect ratio of a wing, the greater lift it provides relative to the drag for the same angle of attack.

The size of the wings/optimum aspect ratio will depend on the type of wing, and other exigencies (for example n, the type of tor, proximity to fences etc). For example, higher-aspect ratios may be advantageous for fixed wings, whereas lower aspect ratios may be advantageous for laterally ling wings.

Larger and more crudely shaped wings may be cheaper and easier to manufacture. A suitable wing aspect ratio for a standard center-pivot or linear irrigator may be approximately 3. ably, the tors/wings will have a chord-to-thickness ratio of between 2-15%.

Thicker wings may result in increased drag.

Configuration of wings around irrigator Referring back to Figures 1a - 1b, the deflectors are ed on either side of the irrigator 1.

Preferably, the wings 10 are arranged generally symmetrically around the irrigator, however in other embodiments the wings may be asymmetrically arranged around the irrigator.

Where an irrigator has a constant orientation to a known prevailing strong wind, such as with a linear tor, then deflectors may be provided only on the upwind side. This approach may also be viable for a rotary irrigator if it is able to be positioned with a desired orientation to a strong prevailing wind prior to a high wind event.

The irrigator 1 shown in Figures 1a-1b includes pivoted joints 15 at the pipe’s connection to the towers 4. In many irrigators, the top pipe is braced mainly t bending loads in the vertical plane rather than torsionally. The effect of this is that each span of the irrigator 1 between two towers is essentially supported at only three points X. In these models of irrigator, preferably the wings 10 are arranged at or near the wheels of the irrigator, as shown in Figures 1a and 1b. If the wings 10 were to be placed elsewhere, the ility of the irrigator 1 would reduce their effectiveness.

However, it is envisaged that in different irrigator models/arrangements, other placements of the wings may be suitable.

Wing Distance from Irrigator Preferably, the wings 10 are outwardly displaced from the longitudinal axis of the irrigator 1.

Generally, the r the wings 10 are displaced from the irrigator’s center line, the greater the ance to g they will provide relative to the extra tipping moment that the wing’s drag adds to the tipping moment. If the wings 10 are of a suitable size and shape they can generally provide sufficient moment from uplift and downlift to usefully counteract some or even all of the tipping moment that the wind forces apply to the irrigator 1.

Wings which are outwardly displaced may interfere with fences or other les. Even when there is a local space constraint requiring wings to stay within the wheelbase outer dimensions, the wings will still be able to provide some useful tipping tion.

In a preferred embodiment, the wings extend over a metre past the wheel, however, the ion is not limited in this way.

Height The optimal height for the wings depends on a number of factors, including the type and height of the irrigator, the crop, the terrain, local wind conditions etc.

If the wings are too high then their drag (as distinct from the upforce and downforce they generate) will unnecessarily add to the total wind induced tipping moment.

If the wings are too close to the ground, they will be in the ‘boundary effect zone’ where wind speed is significantly diminished compared to that which is impacting the main structure at any moment. Wings close the ground may also interfere with crops and fences.

In one embodiment of the ion, the wings 10 are at approximately 2.5 m above the ground. At this height, the wings are likely to be sufficiently clear of boundary layer speed diminution to be useful for stabilisation while still benefiting from the smoothing nce of ground effect (in which gusty winds are less likely to have vertical velocity ents) and being clear of most fences and crops.

The deflectors/wings may be made of any suitable material. Examples include but are not limited to steel, aluminium, fibre reinforced cs, wood, composite board, plywood, or any ations of these.

The deflectors may have any form suitable for applying downforce to the irrigator’s support structure. Figures 3-6 show irrigators with tors of various forms configured to apply downforce to the irrigator’s support structure.

Figures 3a and 3b show an embodiment of an irrigator according to the present invention in which the deflectors have a flat form. The deflectors of this embodiment are of rectangular shape and are disposed at an approximately 30 degree angle to the ground. The wings 10 provide downforce on the upwind side and an upforce, which also acts to counteract tipping moment, on the downwind side.

Figure 4 shows an embodiment of an tor according to the present invention in which the deflectors have a cambered form. This cambered surface increases the upforce on the upwind side and decreases the upforce on the downwind side, compared to the embodiment shown in Figures 3a and 3b. This provides a small net increase in the total downforce, which encourages the wheels to remain in contact with the ground at all times.

This, in conjunction with generating aerodynamic forces that counter all or at least a useful proportion of the total wind induced tipping moment decreases the likelihood that the irrigator will fall over due to windy conditions.

Figure 5 shows an embodiment of an irrigator in which the deflectors include leading edge slats 20. The leading edge slats 20 provide extra downforce and a diminished upforce.

Figure 6 shows an embodiment of an irrigator in which the deflectors include two opposing inflections at the g and trailing edges of the deflector (i.e. a z-shaped surface). This provides extra downforce, and extra upforce.

The deflectors may also be in the form of a delta shaped wing as shown in Figure 14d. Delta shaped wings may be advantageous due to their high lift cients at high angles of attack due to vortex lift.

Deflectors may be provided with any other suitable surface shapes configured to apply rce to the irrigator’s support structure, and the invention is not limited in this respect.

Multiplane wings In Figures 3-6, the deflectors include a single wing form, however multi-plane (multi-layer) deflectors may also be included.

Figure 7 shows an irrigator in which the deflectors include three-substantially planar forms/planes. Any suitable number of forms may be stacked, however up to four planes is preferable. ably, the distance n the planes is between 20%-100% of the chord of the wings Multi-plane deflectors may include flat, cambered or z-shaped wing forms. The multiple planes may or may not be staggered. Preferably, they are staggered such that the top wing is t to the irrigator center line, and the bottom wing is furthest from the center line.

Sweep-back In embodiments in which the deflectors are wings, preferably the wings 10 are swept back.

Figures 8-9 show irrigators including swept-back wings ctors). The apex of each swept back wing is preferably directed away from the irrigator.

Figures 8a and Figure 8b show the swept-back wings which are chevron, whereas Figures 9a and 9b show swept back wings which are curved. As will be discussed later, swept-back wings may be useful to counter longitudinal-wind.

Swept-back multi-plane deflectors are also ged.

Complex angles of attack Figures 10 and 11 show deflectors with complex angles of attack. s 10a-c show two flat wings that may be arranged so that their leading edges are in the horizontal plane while chordwise they present an angle of attack to the wind.

Figures 11a and 11b show two curved wings that may be arranged so that their leading edges and trailing edges are in the horizontal plane while chordwise they present an angle of attack to the wind.

Swept-back wings with complex angles of attack may provide improved tipping ance for winds which ch the longitudinal direction, as their upwind sides at least partly mask their downwind sides.

Additional ments are envisaged of a similar concept with cambered wings, wings with leading edge slates and multi-planes and/or swept-back wings. In addition, the angle of attack may vary spanwise in complex ways.

The leading edge and the trailing edges do not necessarily need to be in the horizontal plane.

Fixed wings Fixed wings as shown in Figures 3-11 provide not only a downforce on the upwind side, but they also generate an upforce (which also acts to ract tipping ) on the downwind side.

It is also possible to provide a wing set as to apply downforce on the upwind side and an equal upforce on the downwind side to exactly counter wind drag induce tipping moment.

Movement The wings 10 shown in Figures 3-11 have been fixed/stationary. r embodiments are also possible in which the deflectors and/or wings are moveable.

Figure 12 shows an embodiment of the ion in which the deflectors are hinged at the ends of the support. The deflectors in Figure 12 pivot as indicated by arrow A relative to a horizontal axis B1.

When the wing is exposed to a downward-force the wing is locked down into the on shown in Figure 12. However, when the wing is exposed to an upward force, the wings pivot up to the position shown in B1, which prevents the wings from providing an upforce, or at least diminishes any upforce.

The ve locked-position and pivoting positions shown are exemplary – wings with different degrees of pivoting resulting in different angles of attack are also possible.

In the shown embodiment the hinged wings have a flat surface, however in other embodiments these may be cambered, slatted and/or multi-plane.

Figure 13a shows a top view of another ment of an tor. The irrigator 1 includes a deflector configured to pivot on a vertical axis. The wings 10 each include a pivot 22 and a tail vane 21, which points the wings 10 to be traverse to the ion of the wind. This allows the wings 10 (in particular, upwind wing 10a) to have considerable leverage in resisting windinduced tipping of the irrigator 1. Thus the swivelling wings provide the same downforce anti tipping movement for all wind directions.

Figure 13b shows a top view of a wing as shown in Figure 13a, including the vane. Figure 13c shows a side view of the vane of figure 13b. This is only one example of a suitable vane – other suitable vane shapes and/or configurations are also possible.

Figure 14a shows a top view of another embodiment of an irrigator including a back wing which is self-pointing without a tail vane. These wings do not require a tail vane because the swept-back shape of the wings 10 naturally act as a vane and directs them to a position traverse to the ion of the wing.

For laterally swivelling wings as shown in Figures 13(a-c)-14(a-c), a lower aspect ratio of the wing 10 will be advantageous as this allows more area to be fitted into the same available space.

A tor could also pivot about the centre line of the irrigator so that one deflector could stabalise both sides of the irrigator. This would require a strong pivot supporting a deflector 3 or 4 meters from the pivot point and could in fact act to tip the irrigator if the pivot jammed.

Dealing with longitudinal winds As previously mentioned, wings subjected to longitudinal wind flow with some random vertical velocity components may generate an uplift that will undesirably increase the wind induced g moment on the irrigator 1.

Figure 15 shows a side view of the support structure of an tor according to an embodiment of the invention, including a fixed wing. The arrows D show a longitudinal gust of wind, which may cause the wing 10 to create an rable upforce as indicated by the arrows E.

In wings which are fixed and not moveable, a higher aspect ratio may be useful as it decreases the efficiency of the wings 10 when the flow is longitudinal. Thus, when the wind direction is longitudinal to the irrigator 1 their angle of attack is zero, to provide neither uplift nor downlift, however this may still contribute to tipping moments when winds have significant vertical velocity components. Therefore a high aspect ratio may desirable, because the functional aspect ratio is the inverse of their aspect ratio when the flow is chordwise. A wing with such an aspect ratio will generate little if any lift forces and is therefore less likely to exacerbate tipping when wind direction is longitudinal (unlike ar or rectangular wings).

Shapes with x angles of attack and shrouding effects, as shown in Figures 10 (a-c) and Figures 11 (a-c), may help mitigate against longitudinal winds.

Figure 16 shows a side view of the t structure of an irrigator according to another embodiment of the invention, including a fixed wing with negative dihedral (anhedral), to mitigate the effect of udinal wind. From whichever direction the longitudinal wind is coming from, when it strikes the wing 10 with spanwise anhedral, the net effect is a rce rather than an upforce because the upwind tip shrouds the downwind tip to an extent. Flow will be cleaner and at higher velocity over the negative angle of attack upwind side of the span causing the rd force on this upwind side to be greater than the upwind force generated by the more turbulent and slower flow on the ve angle of attack ‘wake’ or nd side of the wing.

The other reason why anhedral may be beneficial in this circumstance is that deflections in the main wing support ure can be contrived so as to amplify the excess of downforce relative to upforce caused by the ‘wake’ effect above so as to se the negative angle of attack (which tes downforce) of the more upwind side of each wing and to se the angle of attack (which generates uplift) of the downwind side of each wing. The torsional rigidity of each wing’s mounting structure can be designed so as to exploit this particular effect (and/or it can be pivoted in such a way as to accomplish this) - with suitable damping and weight distribution to prevent destructive aerodynamic flutter of course.

Additional anti-wind measures The basis of this invention is to use aerodynamic forces to counteract or at least mitigate the tipping moment generated by winds striking the tructure of an irrigator, an advantageous aspect of this approach being that such aerodynamic forces increase with increasing wind speed by a similar factor to the increasing tipping moment.

Using anchoring (by screws- which could be electric or hydraulic and automatically actuated- , stakes or weights) to prevent tipping in high winds may remain a necessary fall- back option during extreme conditions, but has the disadvantage that while anchored, the irrigator cannot be used – and that to be ive anchoring must be applied in anticipation of and overlapping actual wind events so is particularly time and cost inefficient in this respect.

Using rd weights (like by water filling the tires for example) to mitigate tipping has the antages of making the irrigator more likely to become stuck in soft ground and can increase loads sufficiently to cause ural failure in wind and load conditions that would otherwise be just within allowable limits- and in the case where irrigators do tip, generally seems to worsen the consequent damage. Adding weight also makes wheel ruts deeper and damages crops more. ions to an irrigator’s wheel base so as to increase resistance to g is a sensible step and will no doubt be a part of the long term solution but is unpopular because it requires special manufacture that is not asked for or supported by purchasers in lower wind places – and also reduces the area adjacent to , tree lines, roads and buildings which can be irrigated. Wheel base extenders (such as mobile crane type lever arms) have the same problem as anchoring.

A weighting system that may be used, includes water tanks mounted near or at each wheel set that can be volitionally or automatically filled so as to weight the irrigator when high wind speeds occur or are anticipated. The irrigator’s progress is likely to be halted whenever these tanks were filled.

As interactions and destructive snaking across nt spans increases the stresses at some location above what could be expected from average wind loadings alone, it is possible to reduce this effect with extra stays where le.. Specifically, a set of stays from each wheel beam up to the main bracing rods on the free end of each span could damp out a useful amount of this twisting and tramping without overstressing the rods and bracing frames themselves. These stays could match the stays from the wheel beam that secure the structure on the fixed side of each tower but would need to have a sliding damped section with sufficient movement to accept the changes in length required to accommodate uneven ground and small deviations from straightness in the top pipes. The damping effect required for effective stabilisation without itself causing over stressing in the main rigging wires may be in the order of 100kg.

Advantages There is thus provided an improved irrigator including deflectors/wings which act to reduce drag-induced tipping moment which may cause an irrigator to fall over. This decreases the likelihood that the irrigator will fall over in strong wings, reducing or preventing lost time, money and productivity.

The irrigator includes anti-tipping resistance at all times, and therefore it is not ary to anticipate strong winds or act quickly if such strong winds begin. There is no need to repeatedly install mechanical anchors every time there is strong wind, and remove them when the wind is over.

The wings are ured to effectively resist drag-induced tipping moment without weighing-down the irrigators in such a way that may cause structural damage to the irrigator or cause it to sink into and become stuck in soft ground or to create ssarily deep wheel ruts.

The wings are at a height that does not impede high-crops, fences or other ground les, thus allowing the irrigator to be placed near such items.

The proposed wings are relatively easy and inexpensive to produce.

While the present ion has been illustrated by the description of the embodiments thereof, and while the embodiments have been described in detail, it is not the ion of the Applicant to restrict or in any way limit the scope of the appended claims to such detail.

Further, the above embodiments may be implemented individually, or may be combined where compatible. Additional advantages and modifications, including combinations of the above embodiments, will readily appear to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details, representative apparatus and methods, and illustrative examples shown and bed. Accordingly, departures may be made from such s without departure from the spirit or scope of the Applicant’s general inventive concept.

Claims (1)

CLAIMS 1. A moveable irrigator having a wheeled support structure and a ity of deflectors of such a size, distribution and orientation as to apply a stabilising downforce on an 5 upwind side or a stabilising upforce on a downwind side to the support structure when exposed to the force of incident wind. 2. The irrigator of claim 1 n , the stabilising force is a downforce on the upwind side. 3. The irrigator of claim 1 or claim 2 wherein downwind, the ising force is an upforce on the downwind side. 4. The irrigator of any one of the ing claims wherein one or more of the 15 deflectors are wings. 5. The irrigator of any one of the preceding claims wherein one or more of the deflectors include a flat surface. 20 6. The irrigator of any one of the preceding claims wherein one or more of the deflectors are pivotable to a position in which they provide a diminished upforce. 7. The irrigator of any one of the preceding claims wherein one or more of the deflectors include a cambered e. 8. The irrigator of any one of the preceding claims wherein one or more of the deflectors include leading edge slats. 9. The irrigator of any one of the preceding claims wherein one or more of the deflectors include two opposing tions at g and trailing edges of the tors. 5 10. The irrigator of any one of the preceding claims where one or more of the tors have a swept back wing form. 11. The irrigator of any one of the preceding claims where one or more of the deflectors have a delta wing form. 12. The irrigator of claim 10 or claim 11 wherein the apex of the one or more deflectors are directed away from the irrigator. 13. The irrigator of any one of the preceding claims wherein one or more of the 15 deflectors pivot about a vertical axis. 14. The irrigator of claim 13 wherein one or more of the deflectors include a tail vane positioned to orient the deflector with respect to incident wind. 20 15. The irrigator of any one of the preceding claims wherein one or more of the deflectors are outwardly displaced from the longitudinal axis of the irrigator 16. The irrigator of claim 15 wherein one or more of the deflectors are displaced beyond one side of the support structure. 17. The tor of claim 15 or claim 16 wherein one or more pairs of deflectors are provided on opposite sides of the support structure. 18. The irrigator of claim 17 wherein a pair of deflectors is provided in an anhedral arrangement. 19. The irrigator of any one of the preceding claims wherein one or more of the 5 deflectors are located at or near the wheels of the irrigator. 20. The irrigator of any one of the preceding claims wherein all deflectors are positioned at or near the wheels of the irrigator. 10 21. The irrigator of any one of the ing claims wherein one or more deflectors are provided above wheels of the support structure. 22. The irrigator of claim 15 or claim 16 wherein the one or more deflectors are provided on one side of the support structure. 23. The irrigator of any one of the preceding claims wherein each deflector consists of a plurality of stacked wings. 24. The irrigator of any one of the preceding claims wherein the tor is a centre-pivot 20 irrigator. 25. The irrigator of any one of the preceding claims wherein the irrigator is a linearly moving irrigator. 25 26. An irrigator as d in claim 1 ntially as herein bed with reference to any one of the embodiments shown in the accompanying drawings. 9 1%

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