AU2019264587A1 - Method and apparatus for extricating a trapped vehicle - Google Patents

Abstract

Apparatus and a method of extricating a motor vehicle from a bogged down state are provided wherein a moving anchor point associated with the vehicle is employed, the anchor point in an embodiment being a leader track section that is placed before a non-driven wheel in the direction of intended advance and a windable track section is placed intermediate the non driven wheel and in advance of the driven wheel. After connecting the two sections, causing the driven wheel to rotate causes the driven wheel to wind up the windable track around it, pulling the leader track against the non-driven wheel. Continuing the winding causes the non driven wheel to advance along the leader track while holding it down to provide an anchor point that moves relative to the vehicle.

Description

Method and apparatus for extricating a trapped vehicle

Field of invention [01] This invention relates to apparatus for and a method of extricating a motor vehicle from a bogged down state. In such a state the driven wheels of the vehicle lack traction, resulting in the vehicle remaining stationary with wheels spinning when throttle is applied, although in gear.

Background to the invention [02] A number of methods and devices are known for use in recovering a trapped vehicle from a bogged down state in soft ground, sand, mud, snow slush and the like.

[03] These range from the use of tow ropes to another vehicle to traction improving implements such a planks of wood, or rigid plastic ramps, for example, for temporary placement beneath a trapped drive wheel. These require some degree of digging before the ramp can be placed for traction to result. The ramps are sizeable, usually being lashed to the outside of the vehicle to conserve stowage space inside. This makes them a targe for thieves.

[04] Other methods involve anchoring the vehicle to an immovable anchor structure and using a winch to haul the trapped vehicle on to safer ground. An example of such a system is disclosed in International Patent Publication WO2014/176642, which describes a vehicle recovery system in which a flexible harness assembly is attached to a driven wheel of a bogged vehicle and to an external anchor point. A drawback of such a system is the need for an external anchor point. Often, none is available.

[05] When other methods fail, a driver is left to dig away the soft slush bogging down the vehicle, until solid enough substrate is reached.

Objects of the invention [06] It is an object of this invention to address the shortcomings of the prior art and, in doing so, to provide apparatus effective for assisting in extricating a bogged down vehicle, preferably without need for digging.

2019264587 13 Nov 2019 [07] Another object of the invention is to provide for extrication of a vehicle without need of an external anchor point.

[08] The vehicle may be any motorised vehicle having a driven wheel and a nondriven wheel arranged generally in line in normal direction of travel of the vehicle, whether forwards or in reverse. The vehicle may be a motor car, utility vehicle, truck or bus, but is not to be considered as limited to these generic forms.

[09] In this specification the terms “unbogging” and “bogging” are used in places to refer to the removal, recovery or extrication of a vehicle from soft residue in which it has become trapped and has lost traction and from which it cannot emerge without external intervention of some kind.

[010] The preceding discussion of the background to the invention is intended to facilitate an understanding of the present invention. However, it should be appreciated that the discussion is not an acknowledgement or admission that any of the material referred to was part of the common general knowledge in Australia or elsewhere as at the priority date of the present application.

[011] Further, and unless the context clearly requires otherwise, throughout the description and the claims, the words ‘comprise’, ‘comprising’, and the like are to be construed in the inclusive sense of “including, but not being limited to” - as opposed to an exclusive or exhaustive sense meaning “including this and nothing else”.

Summary of invention [012] According to a first aspect of the invention there is provided vehicle extrication apparatus comprising first and second elongate sections, means for securing the second section to a driven wheel of a bogged vehicle, wherein the first section is adapted for defining an anchor point associated with the vehicle and wherein the second section is adapted for being wound up in winch-like manner by the driven wheel, whereby rotation of the driven wheel hauls the vehicle toward the anchor point.

[013] In a preferred form of the invention, the anchor point is defined by the first section being trapped by the weight of the vehicle. The anchor point is preferably defined by the weight of the vehicle through a non-driven wheel.

[014] In a preferred form of the invention, the anchor point will move with the vehicle. The anchor point will move as the vehicle begins moving as a result of using the invention.

2019264587 13 Nov 2019 [015] In a preferred embodiment, the second section comprises a ladder-like subassembly of at least two side cords and perpendicularly disposed cross pieces extending between and connecting to the side cords.

[016] In a further preferred form of the invention, the first section comprises a ladder like subassembly having at least two side cords and perpendicularly disposed cross pieces extending between and connecting to the side cords.

[017] The cross pieces correspond generally to the width of a vehicle tyre.

[018] In a further preferred form of the invention, at least one of the sections has side cords with extensions free of interconnecting cross pieces. The extensions are preferably of sufficient length to bypass the non-driven wheel and be fastenable to the other section.

[019] Preferably, a gap free of cross pieces is defined between the sections when fastened, the gap being bounded by an end-most cross piece of each section and the extensions.

[020] In a preferred embodiment, the extensions extend from the first section to be fastenable to the second section at a location intermediate the driven and non-driven wheels. The cords may be fastenable by any suitable means, including knots such as a slip knot, or by shackles, carabiners and similar devices.

[021] According to a second aspect of the invention, there is provided a method of extricating a trapped vehicle having a driven wheel and a non-driven wheel, the method comprising steps of:

a. Arranging a rollable traction-assisting track between the driven wheel and the nondriven wheel,

b. Anchoring the vehicle to the windable track, using weight of the vehicle exerted through the non-driven wheel for defining an anchor point that will move with the vehicle,

c. Fastening the windble track to the driven wheel; and

d. Causing rotation of the driven wheel to advance it along the windable track, towards the non-driven wheel, whereby the driven wheel rolls up around it at least a portion of the windable track, thereby hauling the vehicle towards the anchor point.

2019264587 13 Nov 2019 [022] In a preferred form of the invention, the anchoring means comprises a second, leader track operatively positionable in advance of the non-driven wheel.

[023] In a further preferred form of the invention, the method includes the step of fastening the windable track to the leader track end to end, to define between them a gap with the non-driven wheel located therein.

[024] Preferably, the method includes causing the driven wheel to rotate and begin winding the windable track around it, thereby tensioning the windable track and drawing the leader track against the non-driven wheel.

[025] The method preferably includes the step of causing further rotation of the driven wheel so that the non-driven wheel advances along the leader track, holding down the leader track with its weight, thereby creating an anchor point that advances along the leader track with movement of the non-driven wheel.

[026] According to a third aspect of the invention there is provided a kit for use in extricating a bogged vehicle, the kit comprising first and second interconnectable track sections and means for operatively connecting them, wherein the first section is adapted for being held down by the weight of the vehicle concerned and wherein the second section is adapted for securing to a driven wheel of said vehicle and for being rolled up around the driven wheel in winching-like manner by rotation of the driven wheel, whereby the vehicle is hauled toward the first section, releasing it from bogged condition.

[027] In a preferred form of the invention, the second section includes tractionassisting means effective to assist the driven wheel to gain traction when caused to rotate.

[028] The second section preferably comprises a ladder-like subassembly of at least two generally parallel side cords and cross pieces disposable in use for extending generally orthogonally between and joining the side cords.

[029] The side cords preferably comprise means for fixedly locating the cross pieces in spaced relationship from each other along the cords. The means for fixedly locating the cross pieces along the cords may comprise a series of knots formed in the cord at intervals along the cord length.

[030] Preferably, the cross pieces have looped ends about which the knots are formed. The cross pieces preferably comprise chain, each knot being knotted around an end link of the chain.

2019264587 13 Nov 2019 [031] In an embodiment, the kit includes means for securing the second section to the driven wheel of the bogged vehicle. The securing means may comprise a length of cord for passing between spokes of a wheelrim of the bogged driven wheel.

[032] In a further aspect of the invention, a method of extricating a trapped vehicle having a driven wheel and a non-driven wheel, comprises steps of:

e. Locating an anchor against and in advance of a non-driven wheel, in direction of intended travel;

f. Connecting the anchor to a windable track operatively windable around a driven wheel of the vehicle arrear of the non-driven wheel in intended direction of travel; and

g. Causing rotation of the driven wheel to begin winding the track around it, urging the non-driven wheel against the anchor.

[033] The anchor is preferably adapted to be held down by weight of the vehicle exerted through the non-driven wheel.

[034] Further preferably, the anchor comprises a leader track adapted for the nondriven wheel to travel upon it while the driven wheel winds up the windable track.

[035] In a preferred form of the invention, the method comprises further rotating the driven wheel for winding the windable track and causing the non-driven wheel to advance along the leader track.

Brief description of drawings [036] In order that the invention may be readily understood, and put into practical effect, reference will now be made to the accompanying figures. Thus:

Figure 1 shows in kit form a preferred embodiment of the apparatus of this invention.

Figure 2, is a close-up view of one of the connecting chains in the embodiment of Figure 1.

Figure 3 is a schematic diagram of the apparatus of Figure 1 applied in use to a rear wheel drive vehicle.

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Figure 4 is a callout of the rear, driven wheel of the vehicle of Figure 3 with the apparatus of the invention attached.

Figure 5 is a front-on schematic view of the driven wheel of the vehicle with a section of the apparatus attached for winding up.

Detailed description of an embodiment of the invention [037] The following description and drawings are illustrative and are not to be construed as limiting. Numerous specific details are described to provide a thorough understanding of the presently disclosed embodiments. However, in certain instances, well-known or conventional details are not described in order to avoid obscuring the description.

[038] Reference in this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the disclosure. Use of the phrase “in one embodiment” at various places in the specification are not necessarily referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Moreover, various features are described which may be exhibited by one embodiment and not by another. Similarly, various requirements herein described may apply to one embodiment but not to another.

[039] Referring to Figure 1, in a preferred embodiment of this invention, the vehicle extricating apparatus is generally denoted by the number 10 and shown in schematic view. It has a first section 12, a second section 14 and a piece 16. The principal components are shown separated for ease of explanation in this figure, but form an integrated whole when joined for use in the field.

[040] In this embodiment, each section is made up of a webbing-like structure having a form resembling a rope ladder, in that each section has a pair of flexible rope lengths 18, laid generally in parallel and connected by a series of spaced connecting chains 20. The rope in this embodiment is high tensile strength braided nylon. The rope may be of other materials of similar and sufficient strength for hauling a vehicle from a bogged, stationary condition. For example, an alternative rope may be a stainless steel cable. Neither of these examples should be construed as limiting of the scope of the invention and the claims appended. The materials used may differ depending on the mass of the vehicle with which the apparatus is intended to be used. In other words, the apparatus for intended

2019264587 13 Nov 2019 use with a “compact” category motor car will quite likely differ in materials from apparatus intended to be used with a 3 ton truck, for example.

[041] As shown in Figure 2, in a close-up view of one of the connecting chains, the rope lengths 18 contain knotted loops 22 that secure the end links 24 of the chain and ensure that the individual chains retain their secured positions along the rope, so that they remain spaced from each other along the rope lengths 18, as would rungs of a ladder. Spacing is generally regular, but small variances are tolerable. The sections are intended for arrangement on the ground in advance of at least two of the wheels of the bogged down vehicle, as will be described below. When so arranged, they define a traction assistance zone in the intended path of the driven wheel. It will be appreciated that the arrangement of the cross-elements 20 for connecting to the rope lengths 18 may be varied in other embodiments. For example, the cross elements may be arranged in a diagonal criss-cross pattern. In another embodiment, there may be additional elongate longitudinal elements arranged between rope lengths 18. The preferred embodiment depicted in the drawings should therefore not be construed as limiting of the principle of the present invention.

[042] Reverting to Figure 1, the rope lengths of first section 12 have free leading length portions 26 that are not connected by transverse chains. These portions define ends that are free for fastening to respective eyes 28 at one end of the rope lengths of second section 14. Fastening is achieved by forming a slip-knot, but may be by any other suitable convenient method. The effect of the fastening is to form the rope lengths of first and second sections 12, 14 into a pair of continuous lengths. The overall assembly resembles a rope ladder with a few rungs missing mid-section, that is between extension portions 26.

[043] At the far end 30 of second section 14, a first of the rope lengths 18 is slightly longer than the other, to define an extension piece 32 that has a free end 34 for fastening to terminal loop 34 in the shorter length of rope 18b. Use of the free end for fastening the second section to the drive wheel is described below.

[044] Rope extension piece 32 is of sufficient length to be passed through and behind the bogged drive wheel to fasten the second section to the wheel. Supplementary rope section 16 having a looped end 38 may be used for extending piece 32 if necessary for particularly large wheels or wide tyres. Piece 16 may be provided in different lengths to suit different wheel sizes.

2019264587 13 Nov 2019 [045] The use of the apparatus will be described with the assistance of the drawings of Figures 3 to 5.

[046] In Figure 3, the apparatus of Figure 1 is shown in use in relation to a vehicle 40, the body of which is shown in general form in ghost outline by means of dashed lines. The body is depicted in this manner because the body of the vehicle has no bearing on the use of the invention, other than contributing to the weight of the vehicle that bears on the non-driven wheel. The vehicle in this embodiment is a rear wheel drive vehicle. However, the invention may be as suitably used for front wheel drive and four wheel drive vehicles. It is not suitable, however, for vehicles having a permanent all-wheel drive configuration. This is because it requires that when the invention is in use, only one wheel in the direction of intended travel is receiving driving power and one wheel before it is not receiving driving power. Therefore, when used with a four-wheel drive vehicle, four-wheel drive will need to be disengaged, so that only one pair of the wheels receives driving power. The non-driven pair will provide a moveable anchor point. The anchor point will move with the vehicle as it is caused to advance in the direction of arrow D, which is overlaid on the roof of vehicle 40, for purposes of illustration.

[047] The vehicle schematically depicted in Figure 3 is shown with its right hand side wheels visible. The driven wheel is the right side rear wheel 44, which has become bogged in soft sand, so that when the accelerator is depressed by the driver, the wheel, lacking traction, spins in the direction of arrows 48. The front wheel 46 is not driven and therefore is static. It is intended to extricate the vehicle from its bogged condition by causing it to move forward in the direction of arrow D.

[048] To recover the vehicle from its bogged condition, the following procedure is followed with the vehicle engine switched off and the parking brake applied, but with the vehicle in gear to arrest any unexpected movement. The first section 12 of the inventive device is arranged with the cross pieces 20 laid out in advance of the intended direction of travel of non-driven front wheel 46 and with extension pieces 26 passing on either side thereof to the rear. The first section therefore establishes a leader track onto which the vehicle is intended to advance when the bogged wheel regains traction.

[049] The second section 14 of the apparatus is arranged on the ground in advance of the rear, driven wheel 44, extending toward front wheel 46 so that it lies between the wheels in their line of intended travel. The rope length 18 having extended section 32 is placed on the inner side of wheel 44 so that extension 32 is drawn through the wheel to

2019264587 13 Nov 2019 be fastened to the outer rope length 18 at eye loop 36, securing the second section to the wheel.

[050] With the second section 14 laid out and arranged in the intended path of travel of wheel 44, the first and second sections are fastened together using slip knots, the extension pieces 26 from first section 12 being passed through loops 28 in second section

14. This forms a gap between sections 12 and 14 that is bounded by the side extension 26 and the last of the cross pieces 20 of each section, respectively adjacent extensions 26 and loops 28. This gap is occupied by the non-driven wheel 46 in Figure 3.

[051] Once the two sections have been connected, the user is required to pull first section 12 away in advance of the vehicle and lay it out in line with the intended path of travel of the wheels. The vehicle is now ready for extrication.

[052] In this embodiment, the first section is for use as providing the anchor point for the second section when connected. The first section is configured for being drawn toward, against and then partially beneath the non-driven wheel of the bogged vehicle. The second section, when fastened to the bogged driven wheel, is configured to be wound around this wheel when caused to rotate.

[053] The driver places the vehicle in neutral or park (for automatic gearboxes), starts the engine and selects low gear (or reverse in the case of a front wheel drive vehicle). When the driven wheel is driven to rotate by the driver of the vehicle gently pressing the accelerator, it begins to wind up the second section around it in the manner of a winch. Because of the connection to the first section, the ropes 18 and extension pieces 26 are placed under tension. The weight of the vehicle that bears upon non-driven wheel 46, applies downward force in the direction of arrow P into the surface on which the wheel is resting. This holds back the leading portion of first section 12 that is in advance of the non-driven wheel, preventing it being wound back too, thereby defining anchoring means against which rear, driven wheel 44 is able to haul the vehicle forward and out of the mire in which it is trapped. At first, the crosspiece 20 of section 12 that is closest to extensions 26 is the first to be brought to bear against the non-driven wheel and define the first anchor point.

[054] As tension increases, the rear wheel begins to wind the second section in and around it, as shown in Figures 4 and 5, while the first section remains trapped between the tyre 54 of the front wheel and the ground by the weight of the vehicle on the front axle. As winding force is maintained, the front, non-driven wheel begins to roll, advancing tyre

2019264587 13 Nov 2019 along the leader track defined by the first section, propelled by the rear wheel recovering traction on the path defined by the second, now-tensioned section. Thus, in Figure 4, the ropes 18 of second section 14 are depicted being wound around tyre 54.

[055] When the drive wheels are free of the soft ground or other traction-reducing condition, the driver brings the vehicle to a stop, securing it against rolling with brake on, and separates the first and second sections, by removing by releasing the slip knots in connecting extension sections 26 of ropes 18. Depending on terrain conditions, there are two options for managing the driven wheel, about which the second section will have become at least partially wound. A first option is to release the slip knot which fastens extension piece 32 to eye 36, withdraw piece 32 from the wheel and draw the second section to the side and off the driven wheel. It may be necessary to drive the vehicle slightly forward or backward until the driven wheel is free and clear of the second section before the section can safely be recovered by the driver or an assistant.

[056] A second option for recovery is for circumstances where there is a real risk of becoming bogged down again. Here the risk of bogging can be reduced by using the additional trailing end tie piece 16 to fasten the opposite end of the section, at which eyes 28 are located, to the wheel. The chain cross-pieces provide friction for additional traction until the vehicle has progressed beyond the risky section of terrain.

[057] It will be appreciated that in this second mode of use, the second section functions in the manner of an impromptu form of snow chain.

[058] In particularly deep sand and mud, the process explained above may need to be repeated until firm ground is reached.

[059] It will be appreciated that the invention can be utilised for recovery of wheeled heavy vehicles such as trucks, buses, tractors and the like and can be made to order using larger capacity materials of the same type used in the version described above in relation to lighter vehicles. For example, rope and chain capacities will be adjusted according to requirements, as would be known in the art.

[060] An advantage of the invention lies in its being of practical value to drivers in areas which require driving on narrow country roads, where road shoulders may become soft and unstable in wet conditions, or where it is necessary to drive partially off the shoulder to allow a vehicle travelling in the opposite direction to pass.

2019264587 13 Nov 2019 [061] A further advantage is that the need for a stable external anchor point is dispensed with, the vehicle establishing a rolling anchor point that moves with the position of the non-driven wheels. In the case of a winch, a longer pulling distance is required and the length of the vehicle wheel base. In addition, there is the risk of injury from whiplash resulting from winch cable or connector failure.

[062] A further advantage arises from the use of highly malleable materials and components for the manufacture of the apparatus of the invention. The use of highly malleable and flexible nylon ropes and chains in the preferred embodiment, rather than rigid rods as transverse ties, enables the packed volume of the apparatus to be minimised for stowage and transportation.

[063] In an alternative embodiment, the first or anchor section, placed in advance of the non-driven wheel need not be a rope ladder-like assembly of the kind already described: It may be in the form of a rigid ladder-like assembly, or may have a continuous surface, such as a sheet. The sheet need not be flexible, but could be of a substantially rigid nature, such as an elongate ramp or plank. The sheet preferably would have a moulded friction and traction-enhancing surface to inhibit its being pulled out from beneath the non-driven wheels once it has become trapped against or under them.

[064] As used herein any reference to “one embodiment” or “an embodiment” means that a particular element, feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment.

[065] In addition, use of the “a” or “an” are employed to describe elements and components of the embodiments herein. This is done merely for convenience and to give a general sense of the invention. This description should be read to include one, or at least one, and the singular also includes the plural, unless it is obvious that it is meant otherwise.

[066] These embodiments merely illustrate particular examples of the method, kit and apparatus of the invention providing means for the extrication of a motor vehicle from a bogged condition. With the insight gained from this disclosure, the person skilled in the art is well placed to discern further embodiments by means of which to put the claimed invention into practice.

Claims (24)

1. Vehicle extraction apparatus comprising first and second elongate temporarily disposable track sections, means for securing the second section to a driven wheel of a bogged vehicle, wherein the first section is adapted for defining an anchor point associated with the vehicle and wherein the second section is adapted for being wound up in winch-like manner by the driven wheel, whereby rotation of the driven wheel hauls the vehicle towards the anchor point.

2. Apparatus according to claim 1 wherein the anchor point is defined by the first section being trapped by the weight of the vehicle.

3. Apparatus according to claim 2 wherein the anchor point is defined by the weight of the vehicle through a non-driven wheel.

4. Apparatus according to claim 3 wherein the anchor point will move with the vehicle.

5. Apparatus according to any one of the preceding claims, wherein the second section comprises a ladder-like subassembly of at least two side cords and perpendicularly disposed cross pieces extending between and connecting to the side cords.

6. Apparatus of claim 5 comprising means for fixedly locating the cross pieces in spaced relationship from each other along the side cords.

7. Apparatus according to any one of the preceding claims, wherein at least one of the sections has side cords with extensions free of interconnecting cross pieces, the extensions being of sufficient length to bypass the non-driven wheel and be fastenable to the other section.

8. The apparatus of claim 7 wherein a gap free of cross pieces is defined between the sections when fastened, the gap being bounded by an end-most cross piece of each section and the extensions.

9. A method of extricating a trapped vehicle having a driven wheel and a non-driven wheel, the method comprising steps of:

a. Arranging a windable traction-assisting track between the driven wheel and the nondriven wheel,

2019264587 13 Nov 2019

b. Anchoring the vehicle to the windable track, using weight of the vehicle exerted through the non-driven wheel for defining an anchor point that will move with the vehicle,

c. Fastening the windable track to the driven wheel; and

d. Causing rotation of the driven wheel to advance it along the windable track, towards the non-driven wheel, whereby the driven wheel rolls up around it at least a portion of the windable track, thereby hauling the vehicle towards the anchor point.

10. A method according to claim 9 wherein the anchor point comprises a leader track operatively positionable in advance of the non-driven wheel.

11. A method according to claim 10 including the step of fastening the windable track to the leader track end to end, to define between them a gap with the non-driven wheel located therein.

12. The method of claim 11 wherein causing the driven wheel to rotate and begin winding the windable track around it, tensions the windable track, drawing the leader track against the non-driven wheel.

13. The method of claim 12 causing further rotation of the driven wheel so that the nondriven wheel advances along the leader track, holding down the leader track with its weight, thereby creating an anchor point that advances along the leader track with movement of the non-driven wheel.

14. A kit for use in extricating a bogged vehicle, the kit comprising first and second interconnectable track sections and means for operatively connecting them, wherein the first section is adapted for being held down by the weight of the vehicle concerned and wherein the second section is adapted for securing to a driven wheel of said vehicle and for being rolled up around the driven wheel in winching-like manner by rotation of the driven wheel, whereby the vehicle may be hauled toward the first section, thereby to release it from bogged condition.

15. A kit according to claim 14 wherein the second section includes traction-assisting means effective to assist the driven wheel to gain traction when caused to rotate.

16. A kit according to claim 15 wherein the second section comprises a ladder-like subassembly of at least two generally parallel side cords and cross pieces disposable in use for extending generally orthogonally between and joining the side cords.

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17. The kit of claim 16 wherein the side cords comprise means for fixedly locating the cross pieces in spaced relationship from each other along the cords.

18. The kit of claim 17 wherein the fixed locating means comprises a series of knots formed along the cords at intervals.

19. The kit of claim 18 wherein the cross pieces have looped ends about which the knots are formed.

20. The kit of claim 19, wherein the cross pieces comprise chain, each knot being knotted around an end link of the chain.

21. A method of extricating a trapped vehicle having a driven wheel and a non-driven wheel, the method comprising steps of:

a. Locating an anchor against and in advance of a non-driven wheel, in direction of intended travel;

b. Connecting the anchor to a windable track operatively windable around a driven wheel of the vehicle arrear of the non-driven wheel in intended direction of travel; and

c. Causing rotation of the driven wheel to begin winding the track around it, urging the non-driven wheel against the anchor.

22. The method of claim 21 wherein the anchor is adapted to be held down by weight of the vehicle exerted through the non-driven wheel.

23. The method of claim 22 wherein the anchor comprises a leader track adapted for the non-driven wheel to travel upon it while the driven wheel winds up the windable track.

24. The method of claim 23 comprising further rotating the driven wheel for winding the windable track and causing the non-driven wheel to advance along the leader track.