CA2569506A1 - Snowmobile - Google Patents

Abstract

The invention refers to a snowmobile comprising a pair of glide means.
According to the inventioin, a track width of said pair of glide means is variable.

Description

bmk SNOWMOBILE

The invention refers to a snowmobile comprising a pair of glide means.

Snowmobiles with a pair of glide means are known. Some of these snowmobiles have a wide track width and are, thus, favorable in some situations such as when driving on hard surfaces such as a snowmobile track, but awkward in other situations.

Other snowmobiles have a somewhat narrower track, which is better in deep-snow conditions and when traversing hills, but then less stable in other situations.

What is also known is single track snow vehicles. These vehicles employ one cen-trally placed steering ski ahead of an endless drive belt. Examples are published in US
6,234,263, US 5,947,220, US 5,904,217, US 5,586,614 and US 5,474,146.
US 6,467,787 shows a steering mechanism for a snowmobile_with a pair of glide means. The steering mechanism enables the driver to more easily displace his or her body sideways as well as steering the vehicle from this position.

The different needs of the driving conditions really call for different snowmobiles, which means that today either the vehicle will be good for one purpose, but not so good for the other, or vice versa. Alternatively, it is configured as a compromise.

In some situations, it might further be necessary or at least advantageous to tilt the snowmobile. However, with the type of snowmobiles with two skis, even when the track width is in what is now called a narrow configuration, typically down to 900 mm, the snow-mobile is not easily tiltable. This is due to the positions of the axes around which the snow-mobile must be tilted. These axes each extend from one ski to the edge of the drive belt on each side of the snowmobile. If for instance the vehicle is making a right turn, it must be tilted by rotating it around the right hand side tilt axis. This involves elevating the snowmo-bile up. The effort (tilting moment) necessary to do this depends on the weight of the snow-mobile, the longitudinal position of the center of gravity, the width of both the drive belt and the front track between the skis as well as the resilience of the ground surface.
Typically a snow mobile has a center of gravity quite forward, where the tilt axes lay well apart, meaning that a considerable effort is usually needed to tilt the vehicle.

This means that, unlike such as when operating a motorcycle, the driver (and pas-senger) have to move their bodies sideways to achieve some tilting of the vehicle. To achieve real tilting, the driver frequently has to stand with both his feet on the footboard on one side of the snowmobile. This is physically rather demanding. Furthermore, it is common for both driver and passenger to have to move the upper parts of their bodies sideways in order to negotiate change of directions during all conditions.
The common type of snowmobiles with two steering skis spaced in a wide track and a central endless drive belt has the disadvantage of the skis not compacting the snow be-fore it is engaged by the drive belt, something which would have been beneficial in deep-snow conditions.
The known single track snowmobiles always have to be controlled by the driver against falling (tipping over). In some driving conditions it is - as discussed - beneficial to be able to easily tilt the vehicle. In other conditions however, such as when driving slowly and at standstill, and when driving on hard or icy tracks, the snowmobile should be stabilized against falling, and not have the freedom to tilt. If not - such as with single track snowmo-biles - there are the following drawbacks:

The strain on a driver and on a potential passenger will be large.
Furthermore, the luggage payload will be severely limited, as a heavily loaded snowmobile will be difficult to hold. An indication of this is found in US 6,234,263, which describes a single track vehicle to be of "type recreational".

The steering mechanism described in US 6,467,787 allows the driver to more easily shift his or her body sideways and then more easily control the steering from this position. It is clear that this will improve the control of the vehicle when it is subjected to a side force.
However, the mechanism will still not easily enable true tilting of the snowmobile.

In short: The above-detailed known snowmobiles are limited by drawbacks in those situations where a narrow track width and preferably tiltability would have improved the control of the snowmobile. The proposed single track snowmobiles have the opposite prob-lem.

In view of the above, it is an object of the present invention to provide a snowmobile comprising a pair of glide means, which snowmobile is enhanced with view to controllability.
According to the invention, the above object is achieved by a snowmobile compris-ing a pair of glide means, characterized in that a track width of said pair of glide means is variable.

Thereby, the track width can be adjusted according to the current situation.
For ex-ample, the track width can be narrow when riding fast or when riding in deep snow. Such a narrow track width particularly enhances tiltability of the snowmobile, what is advantageous.
On the other hand, the track width can be adjusted to be wide, particularly when riding at a low velocity or during standstill, stabilizing the snowmobile.

Preferably, the track width is variable during riding. In other words, the snowmobile is made to react to changing riding conditions quite flexible.
Said glide means are preferably front skis.
What is provided according to a preferred embodiment of the invention is a glide means orientation defining rod being coupled, on the one hand, to said glide means and, on the other hand, pivotably coupled to a chassis, wherein a coupling of said glide means ori-entation defining rod to said chassis is positioned to ensure that a glide means orientation defined by said glide means orientation defining rod is essentially independent of said track width.

Thereby, what is achieved is that an adjustment of the track width is possible during riding, without influence on the orientation of the glide means, further facilitating the control of the snowmobile.

The above expression "essentially independent" means independent as far as pos-sible with view to usual tolerances and imperfections.

Furthermore, "essentially independent" allows for - which is frequently done in wheet suspensions - a nominal position of the pivot point slightly away from the neutral in order to achieve a certain effect such as always steering slightly in or out when all geometrical toler-ances are coming into effect.

The glide means orientation defining rod is preferably a steering rod. In other words, said glide means or front skis, respectively, serve for steering the snowmobile.

Preferably, the glide means are coupled to a chassis by means of pendulum arms mounted to said chassis pivotably about axes transverse to a glide means main plane.
Thus, the variation of the track width is performed by moving said pendulum arms around said axes, i.e. like scissors. This is a quite simple construction.

According to a preferred embodiment of the invention, what is provided is cardan joints or spherical joints for coupling said pendulum arms to said chassis.
Particularly when using cardan joints, what is achieved is that momenta around the longitudinal axis of the pendulum arms are absorbed, what is important particulaHy during cornering of the snow-5 mobile. In the case of spherical joints, said momenta have to be absorbed by other means.
More preferably, one of the pivot axes of a cardan joint for coupling said pendulum arm to said chassis is inclined relative to a pivoting axis of a joint for coupling an extendable track width adjusting means to said chassis.
Preferably, said pendulum arm and said glide means orientation defining rod are parallel parts of a parallelogram or trapezoid mechanism. What is achieved by this feature is that the glide means orientation is essentially independent of the track width.

According to a further preferred embodiment of the invention, the glide means are biased to a wide track configuration. In other words, the narrow track configuration is only realized in case that a driver performs a respective control of the snowmobile, e.g. by pressing a button or by actuating a lever. Releasing the button or lever, respectively, imme-diately results in the snowmobile being adjusted to the wide track configuration because of the bias. Thereby, a high level of security is achieved. .

Preferably, the snowmobile has a drive means, wherein the track of at least one of said glide means at least partially overlaps with the track of said drive means, in at least one track width configuration. Thereby, the glide means serves for compacting the snow before the snow is engaged by the drive means, resulting in a more efficient driving of the snow-mobile.

To this end, what is preferred is that said one glide means track overlaps with said drive means track by at least 25 % of the glide means track in a narrowest track width con-figuration.

According to a most preferred embodiment of the invention, the snowmobile com-prises a suspension assembly for connecting said glide means to a chassis, said suspen-sion assembly being adapted to allow said glide means to move transverse to their main planes, but in opposite directions, in order to tilt said chassis.

The above-described tiltability of the snowmobile very much enhances the controlla-bility and steerability of the snowmobile.

Preferably, said suspension assembly comprises a glide means orientation defining rod being, on the one hand, coupled to a glide means and, on the other hand, pivotably coupled to said chassis, wherein a coupling of said glide means orientation defining rod to said chassis is positioned to ensure that a glide means orientation defined by said glide means orientation defining rod is essentially independent of said glide means movement transverse to the glide means main plane.

In other words, a tilting movement does not influence the orientation of the glide means and, thus, needs not to be compensated by respective steering movements.
In other words, what is provided is "zero bump steer".

Said glide means orientation defining rod is preferably a steering rod. In other words, the snowmobile is preferably steerable by respectively controlling the position of said glide means, which might be front skis.

Said suspension assembly preferably comprises a pendulum arm for coupling a glide means to said chassis. This is a very simple solution for attaching said glide means to the chassis.
What is even more preferred is that said coupling of said glide means orientation defining rod to said chassis is positioned approximately on a rotating pivot through a joint for coupling said pendulum arm to said chassis. Thereby, said coupling of said glide means orientation defining rod to said chassis is positioned in a"neutral area".
What is meant by "approximately" is that the position might vary with view to usual tolerances and imperfec-tions. Furthermore, the exact optimum position depends on various circumstances and on the overall geometry of the glide means suspension.

According to a preferred embodiment of the invention, a line through a joint for cou-pling said pendulum arm to said chassis and through a joint for coupling said glide means orientation defining rod to said chassis is inclined relative to a horizontal line perpendicular to a lengthwise direction of the snowmobile. Thereby, glide means movements in the verti-cal direction change the angle of the main plane of said glide means, what is to some extent useful, particularly when the track is adjusted to be wide. The same applies to a depend-ency of said main plane angle from the track widths.

Preferably, said line through said joint for coupling said pendulum arm to said chas-sis and through said joint for coupling said glide means orientation defining rod to said chassis goes through a joint for coupling an extendable track width adjusting means to said chassis.

More preferred, an inclination angle as seen from above is 4 to 30 degrees and an inclination angle as seen from the front of the snowmobile is 0 to 5 degrees.

Preferably, a force acting against said movement of said glide means is variable. In other words, a force acting against tilting of the snowmobile is variable.
This is particularly advantageous with view to the fact that a tilting should be more easily performed when rid-ing at high speed, whereas it should be not so easily be performed particularly during standstill. During standstill, a tilting might be completely prevented.

According to a preferred embodiment of the invention, the force acting against said movement of said glide means and, thereby, against tilting is dependent on the track width.
Particularly, easy tilting should be possible in a narrow track configuration, whereas a tilting should not be so easy in a wide track configuration.

To achieve this, preferably an angular position of a means applying said force rela-tive to said suspension is dependent on the track width. This is a mechanically quite simple solution.

According to a preferred embodiment of the invention, a height of a front part of the snowmobile is dependent on the track width. Thereby, further advantages are achieved with view to the controllability of the snowmobile.

Preferably, said glide means are coupled to a suspension assembly by joint means, said joint means allowing said glide means to pivot around axes parallel to the main plane of said glide means, but not around an axis transverse to said main plane.
These features result in an improved stability of the snowmobile during riding on uneven and bumpy sur-faces.
In order to further enhance stability, preferably said glide means is biased around an axis parallel to its lengthwise direction into a position parallel to a main plane of the snow-mobile. In other words, said glide means is always urged to return in a position parallel to the main plane of the snowmobile and, thereby, into a position parallel to a horizontal plane when standing on horizontal ground, to further stabilize the snowmobile.

A very simple solution according to the invention includes that a biasing force results from torsion.

As is to be taken from the above explanations, the invention provides preferably for a front ski suspension with a track which is varied according to the conditions during riding.
Furthermore, the track may be extremely narrow when it is in the narrow configuration. This greatly enhances tilting at will by the driver. Furthermore, the skis - when in a very narrow track - will compact the snow before it is engaged by a driving belt.
Conversely, the track may be very wide when it is in the wide track configuration.
This enhances stability against falling (tipping over).

The several purposes of the invention are thus to allow a new type of snowmobile to be driven according to the needs of the conditions. This will make the operation of the snowmobile easier as well as reduce the strain on the driver - as well as on a potential pas-senger. This would improve the safety of the operation of the snowmobile.
Furthermore, it is the purpose of some embodiments of the invention to increase the traction of the drive belt in deep-snow conditions. This will improve the operation and increase the usefulness of the snowmobile. Another purpose of some embodiments of the invention is to enable a snow-mobile in a cost-efficient manner. This is done by providing a simple and effective mecha-nism to achieve the purpose.
The above purposes are preferably achieved by providing a suspension mechanism which varies the track of two front skis. The mechanism is suspended on springs and dampers which are effective in the narrow and wide track configurations as well as in all intermediate positions in between.
The ratio between tilting angle and vertical (referring to the snowmobile) movement of the skis, thus suspension springs, thus resistance against tilting, preferably varies with the track. This means that when the skis are in the narrow track positions, tilting is achieved by one ski going up and the other one going down (referring to the snowmobile). The skis are preferably steerable in all track configurations, and the steered direction is not noticea-bly influenced by the track width itself. This means that a change of track during speed does not influence the direction into which the snowmobile is steered.

Cost effectiveness of the invention is preferably achieved by providing a mechanism which may readily be adapted to current snowmobiles. Furthermore, the mechanism itself preferably consists of a minimum of parts, and standard mechanical elements such as bearings, joints and tubes are used to a large extent.

Cost effectiveness of the invention may preferably also be achieved by utilizing a pressurized oil lubrication system to be found on some snowmobile engines to actuate the variation of the track.

International patent application PCTIIB 02/05833, filed by the applicant of the pres-ent application on December 20, 2002, refers to a wheeled vehicle, which vehicle is quite similar in construction of a suspension assembly of the wheels as compared to the suspen-sion assembly of the glide means or skis, respectively, of the present invention, so that ref-erence is made here to all the disclosure of PCT/iB 02/05833.

The following is a detailed description of preferred embodiments of the invention, referring to the drawings, in which figure 1a is a schematic perspective view of a preferred 5 embodiment of a snowmobile according to the invention, figure 1 b is a front view of said mobile at standstill, 10 figure 1c is the same view as figure 1b, but in a tilted condition, figure 2 is a schematic view of the front ski suspension assembly, figure 3 is a view of the right hand side of the assembly according to figure 2, as seen from above, figure 4 is a schematic front view meant for explaining the movements when tilting, figure 5 is a perspective view showing details of attach-ing a front ski to a front ski suspension assem-bly, figure 6 is 2 front views meant for explaining the effects of track width adjustment, and figure 7 is the same view as figure 3, but of another em-bodiment.

Figure 1 a shows a perspective view of a snowmobile according to a preferred em-bodiment of the invention, with a centrally placed drive belt A and two steered front skis 5,5 configured in a narrow track. The snowmobile is tiltable, as shown in the front view accord-ing to figure 1c. Figure 1b shows the snowmobile with a wide track configuration, when it is not easily tiltable, and safe against falling (tipping over).

Figure 2 shows details of a sprung and damped steerable suspension assembly with a variable track.
The skis 5 are pivotally attached to steering pivots 3 which can be swivelled in bearing supports in housings in pendulum arms 1. Steering arms 4 are rigidly fixed to the steering pivots, and are actuated through steering rods 6. Said steering rods 6 are con-nected to steering swivel 8. Pendulum arms I are fixed to a sub-frame 2 through cardan joints 7. Supported on said sub-frame 2 on spherical joints, extendable elements 9 control pendulum arms 1 through joints 15 (figure 3). If said extendable elements 9 are attached to pendulum arms 1 by precise and stiff revolution joints, spherical joints 11 may alternatively be used to attach said pendulum arms 1 to sub-frame 2, instead of cardan joints 7, cf. the lower right part of figure 2. Suspension spring and damper units 13 control the vertical (seen in the direction of the snowmobile) movements of pendulum arms 1 by being attached to said pendulum arms 1 as well as to the chassis (not shown) of the snowmobile by spherical joints.
Figure 3 shows a top view of the details of the right hand side of the mechanism in both the narrow and wide track positions. The dotted lines indicate the ski, pendulum arm and steering linkage in the outer (wide track) position.

Pivot axis 14 goes through joints 7 (or 11, depending on which type is used) and spherical joints 15 of said extendable elements 9. Joints 16 between steering swivel 8 and steering rods 6 are spherical or of the cardan type, and the joint center is placed to ap-proximately intersect axis 14 when the steering mechanism is in the straight ahead position.
It is understood that when in this position, any vertical movements of the skis 5, thus of pendulum arms 1, are not influencing the steered straight ahead direction of skis 5. To use a common expression used in the field of wheeled vehicle suspensions, the mechanism has "zero bump steerA. This applies to all track configurations of the mechanism.

Said extendable elements 9 control the track. When they are governed to be short, the mechanism has a narrow track. When they are governed to be long, the track is wide.

It is understood that said extendable elements 9 may be actuators controlled by electricity or cylinder and piston assemblies controlled by fluid or compressed air. It is fur-thermore understood that said elements may contain springs which act against the ele-ments being compressed, in other words tend to keep them extended.

Pendulum arms 1 and steering rods 6, together with steering arms 4 and the dis-tance between joints 7 (or 11) and 16 configures or nearly configures a parallelogram mechanism. Alternatively, a trapezoid mechanism can be used. It can be shown that the mechanism can be deployed with a practical geometry which provides parallel skis 5 in both the narrow and wide track configurations, as well as parallelism or near parallelism in the positions in between.
The preferred use of the mechanism is to either drive the snowmobile with a wide or narrow track, the positions in between being transitional, effected in as little as one second or a little more. It is therefore understood that a slight out of parallelism in this phase will have but a minor, temporary and hardly noticeable influence on the steered direction.
The bending moments which are built up in the mechanism due to side forces on skis 5 are taken up as torsion in pendulum arms 1 and are transmitted to sub-frame 2 through cardan joints 7. Cardan joints 7 themselves allow angular movements around their two principal axes alone or in combination, so that pendulum arms are free to swivel in all directions but not rotate. Alternatively fixing pendulum arms 1 to sub-frame 2 through ball joints 11 and supporting them against rotation by means of precise and sturdy pin joints to extendable elements 9 will alternatively provide the same load-carrying effect.

A typical drive belt width today is 380 mm, and skis 5 typically have a width of 180 mm. With these skis, it is possible to have a narrow track of 200 mm between the center planes of the skis. It is now realized that this lines up well with drive belt A both for tilting as well as for the skis compressing deep and loose snow before it is engaged by drive belt A.

Figure 4 shows how the vertical ski movements induced by ti(ting vary according to the width of the track between skis 5. This clearly shows the usefulness of varying the track according to the need of the situation:

When in a narrow track configuration, the snowmobile may be tilted against the sus-pension springs, with one ski being forced up and the other down. The vertical movements needed for this are small, so that tilting is facilitated. Again, here "vertical movements" are understood to be in the vertical direction of the snowmobile when standing on horizontal ground. The vertical movements is this track position are denounced al and a2 in figure 4, and it is clear that they are so small that they are well within the normal vertical suspension movements of the mechanism. In figure 4, 19 denounces a ground plane which the vertical movements refer to.

Should the snow furthermore be so deep and loose that it does not provide ample resistance onto the skis, the body of the snowmobile will float somewhat on the snow. Now a combination of vertical ski movements and simply tilting the vehicle is the case. Both modes are greatly facilitated by having the narrow track configuration. It is here noted that tilting against the force of a sprung suspension means tilting against a resisting moment.
This resistance is useful for helping leveling the snowmobile back to an upright position af-ter tilting.

Conversely, the great vertical movements needed for tilting in the wide track position of the skis effectively secure the snowmobile against tilting, in other words stabiiize the snowmobile so it cannot easily tip over. Here, b1 and b2 denounce the vertical movements in this position. It can be shown that these movements by far exceed the limits of the movements of a suspension, and thus cannot take place. In other words, the snowmobile must be lifted up to be tilted.

It is understood that the natural or regular track configuration of the snowmobile is the wide track. The snowmobile is parked in the wide track configuration, and ridden in the wide track condition, similar to conventional snowmobiles, until the driver decides that he or she wants to drive in the narrow track condition. The respective change over may then be achieved by the driver actuating and holding a button or lever on the steering handlebar.
The transition from the wide track to the narrow track takes a second or so.
The snowmobile now stays with the narrow track for as long as the button or lever, respectively, is held, and will immediately go back to the wide track condition, when the button or lever, respectively, is released. This mode of operation is a parallel to the frequently used method of controlling accelerators of snowmobiles, thus will intuitively fit well together with this.

Namely, if something unforeseen happens when riding with a narrow track, such as for example the driver or a passenger falling off the machine, both the accelerator and the track controlling button or lever will then be released. The engine speed will get down, the drive transmission will be disengaged and the track will go to the wide position, enabling the snowmobile to come to rest in an upright position.

Figure 5 shows a useful enhancement of the ski attachment. Here, reference nu-meral 20 refers to a wedged-shaped yoke which is fixed to a torsion spring 24, which latter is pivotally attached to the ski body by two bearing blocks 22. In effect we here have a joint with cardan-like action. Torsion spring 24 is rotatably fixed to ski 5 by means of an anchor block 23. The effect of this is that the orientation of ski 5 may to some extent be allowed to adapt to the situation, such as when driving on a surface which is not very resilient, never-theless tilting is still called for.

This may come in combination with using a drive belt A which is adapted for more easily allowing tilting such as for example through having more resilient edges. The angular freedom of the attachment may be limited by - for example - limiting surfaces 21 which stop further rotation when they hit ski 5. These stops may be cushioned by layers of rubber. The figure shows one preferred embodiment. However, it is clear that there are many altemative solutions such as placing the torsion spring by a pin and having rubber springs attached to the wedge block and so on.

Figure 6 shows yet another useful improvement of the suspension: It is beneficial to have soft suspension springs when the skis are in the narrow track to facilitate the tilting movements of the skis. Conversely, it is beneficial to have somewhat stiffer suspension springs in the wide track position to secure the vehicle against tilting/leaning out of the curve.
As shown on the left hand side half-figures, this can be solved by positioning spring and damper units 13 so that they have a lower effective ratio between own movements and the vertical (seen in the direction of the vehicle) movements of skis 5 when they are in the narrow track. When the skis are in the wide track, said ratio is higher. The effects of this are soft suspension springs in the narrow track position, and harder suspension springs in the wide track position.

In other words, the angular position of spring and damper units 13 relative to the suspension assembly and, thus, relative to skis 5 is dependent on the track width.

Another effect of this spring and suspension geometry is that the front part of the 5 snowmobile will sit nearer to the ground in the narrow track configuration, but is raised in the wide track configuration.

The needs of the different driving conditions may however in some cases be oppo-site: A large clearance to the ground may be wanted in deep-snow conditions where the 10 narrow track is most likely to be used, whereas a low center of gravity is wanted in the wide track positions where stability against leaning out of curves are wanted. The right hand side half-figures of figure 6 show how this can be solved by lengthening and shortening the sus-pension spring and damper units according to the needs. This may for example be done through hydraulic means, as indicated by flexible tubes 25.
If said extendable elements 9 shown in Figures 2 and 3 are of a hydraulic type, said suspension units may conveniently be coupled to the same control system.

Figure 7 shows a ski suspension and steering mechanism with the pendulum arms pivoting around axes 26 which are at an angle a(13.5 ) to a horizontal line perpendicular to the lengthwise direction of the skis (or of the snowmobile). It is understood that - seen in a front view of the snowmobile - a similar deviation of the axes compared to a horizontal di-rection may also be applied. Now it is understood that the ski movements in the vertical direction of the snowmobile change the angle of the main plane of the skis -as seen in a front view of the snowmobile - due to the pivoting action around axis 26. It can be shown that this effect may to some extent be useful, particularly in the wide track position of the skis. Now it is furthermore understood that if the fixing of the pendulum arm to the chassis of the snowmobile is by means of a cardan joint, the orientation of the axes of said joint may differ from axis 26. It is clear that this will then determine the angular orientation of the main plane of the skis - as seen in a front view of the vehicle - during vertical ski movements -independent of the orientation of axis 26. This again enables the ski suspension to be kine-matically optimized for all track widths and vertical movement combinations.

Claims (27)

1. A snowmobile comprising a pair of glide means, characterized in that a track width of said pair of glide means is variable.

2. The snowmobile according to claim 1, characterized in that said track width is vari-able during riding.

3. The snowmobile according to claim 1 or 2, characterized in that said glide means are front skis.

4. The snowmobile according to any preceding claim, characterized by a glide means orientation defining rod being coupled, on the one hand, to said glide means and, on the other hand, pivotably coupled to a chassis, wherein a coupling of said glide means orientation defining rod to said chassis is positioned to ensure that a glide means orientation defined by said glide means orientation defining rod is essentially independent of said track width.

5. The snowmobile according to claim 4, characterized in that said glide means orien-tation defining rod is a steering rod.

6. The snowmobile according to any preceding claim, characterized in that said glide means are coupled to a chassis by means of pendulum arms mounted to said chas-sis pivotably about axes transverse to a glide means main plane.

7. The snowmobile according to claim 6, characterized by cardan joints or spherical joints for coupling said pendulum arms to said chassis.

8. The snowmobile according to claim 7, characterized in that one of the pivot axes of a cardan joint for coupling said pendulum arm to said chassis is inclined relative to a pivoting axis of a joint for coupling an extendable track width adjusting means to said chassis.

9. The snowmobile according to any of claims 6 to 8, characterized in that said pendu-lum arm and said glide means orientation defining rod are parallel parts of a paral-lelogram or trapezoid mechanism.

10. The snowmobile according to any preceding claim, characterized in that said glide means are biased to a wide track configuration.

11. The snowmobile according to any preceding claim, characterized by a drive means, wherein the track of at least one of said glide means at least partially overlaps with the track of said drive means, in at least one track width configuration.

12. The snowmobile according to claim 11, characterized in that said one glide means track overlaps with said drive means track by at least 25 % of the glide means track in a narrowest track width configuration.

13. The snowmobile according to any preceding claim, characterized by a suspension assembly for connecting said glide means to a chassis, said suspension assembly being adapted to allow said glide means to move transverse to their main planes, but in opposite directions, in order to tilt said chassis.

14. The snowmobile according to claim 13, characterized in that said suspension as-sembly comprises a glide means orientation defining rod being, on the one hand, coupled to a glide means and, on the other hand, pivotably coupled to said chassis, wherein a coupling of said glide means orientation defining rod to said chassis is po-sitioned to ensure that a glide means orientation defined by said glide means orien-tation defining rod is essentially independent of said glide means movement trans-verse to the glide means main plane.

15. The snowmobile according to claim 14, characterized in that said glide means ori-entation defining rod is a steering rod.

16. The snowmobile according to any of claims 11 to 15, characterized in that said sus-pension assembly comprises a pendulum arm for coupling a glide means to said chassis.

17. The snowmobile according to claim 16, characterized in that said coupling of said glide means orientation defining rod to said chassis is positioned approximately on a rotating pivot through a joint for coupling said pendulum arm to said chassis.

18. The snowmobile according to claim 16 or 17, characterized in that a line through a joint for coupling said pendulum arm to said chassis and through a joint for coupling said glide means orientation defining rod to said chassis is inclined relative to a hori-zontal line perpendicular to a lengthwise direction of the snowmobile.

19. The snowmobile according to claim 18, characterized in that said line through said joint for coupling said pendulum arm to said chassis and through said joint for cou-pling said glide means orientation defining rod to said chassis goes through a joint for coupling an extendable track width adjusting means to said chassis.

20. The snowmobile according to claim 18 or 19, characterized in that an inclination an-gle as seen from above is 4 to 30 degrees and an inclination angle as seen from the front of the snowmobile is 0 to 5 degrees.

21. The snowmobile according to any of claims 13 to 20, characterized in that a force acting against said movement of said glide means is variable.

22. The snowmobile according to claim 21, characterized in that said force is dependent on the track width.

23. The snowmobile according to claim 21 or 22, characterized in that an angular posi-tion of a means applying said force relative to said suspension is dependent on the track width.

24. The snowmobile according to any preceding claim, characterized in that a height of a front part of the snowmobile is dependent on the track width.

25. The snowmobile according to any preceding claim, characterized in that said glide means are coupled to a suspension assembly by a joint means, said joint means al-lowing said glide means to pivot around axes parallel to the main plane of said glide means, but not around an axis transverse to said main plane.

26. The snowmobile according to claim 25, characterized in that said glide means is biased around an axis parallel to its lengthwise direction into a position parallel to a main plane of said snowmobile.

27. The snowmobile according to claim 26, characterized in that a biasing force results from torsion.