CA2602995C

CA2602995C - Noiseless rubber tracks for tracked vehicles

Info

Publication number: CA2602995C
Application number: CA2602995A
Authority: CA
Inventors: Michel Paradis; Stephane Pilette
Original assignee: Camso Inc
Current assignee: Camso Inc
Priority date: 2006-09-22
Filing date: 2007-09-19
Publication date: 2016-01-19
Anticipated expiration: 2027-09-19
Also published as: CA2602995A1

Abstract

A rubber track for tracked vehicles, comprising a rubber belt with an inner surface and a ground-engaging surface, the ground-engaging surface comprising a series of traction lugs spaced apart in a longitudinal direction of the track at a first pitch, the inner surface provided with a series of drive lugs spaced apart in the longitudinal direction of the track at a second pitch, wherein the rubber belt comprises at most one reinforcing rod, embedded in a rubber material thereof and extending transversally substantially over an entire width of the track, at every two traction lugs

Description

TITLE OF THE INVENTION
Noiseless rubber tracks for tracked vehicles.
FIELD OF THE INVENTION
[0001] The present invention relates to tracked vehicles. More specifically, the present invention is concerned with noiseless rubber tracks for tracked vehicles.
BACKGROUND OF THE INVENTION

[0002] A track for a tracked vehicle typically comprises an endless drive belt trained around drive sprockets or wheels for driving the belt in an endless path.

[0003] As illustrated in Figure 1 (PRIOR ART), the belt 12 has an inner surface 14 and a ground-engaging surface 16, which, as it passes along a lower run of the belt 12, engages a surface (not shown) to be traversed.

[0004] The ground-engaging surface 16 comprises a series of projecting and transversally extending traction lugs 20. The traction lugs 20 are regularly spaced apart in the longitudinal direction of the track at a pitch P.

[0005]
Typically, the endless belt 12 is made of flexible rubber and reinforcing rods 24 are embedded in the rubber material of the body of the belt 12, at the same pitch spacing P, each of which extends transversally substantially over the entire width of the track. The thickness of the track is locally increased in the region of the embedded reinforcing rods, corresponding to the region of the traction lugs 20. Such reinforcing rods 24 provide transverse rigidity to the track.

[0006] The inner track surface 14 is typically provided with a series of drive lugs 18, which are spaced along the length of the inside surface of the belt 12 at the same pitch P, for engaging drive wheels (not shown) as is well known in the art.

[0007] Ongoing efforts are made in the field of tracked vehicles to try and reduce the overall noise level of this type of vehicles. The regularity of the pitch spacing of the various elements discussed hereinabove has been recognized as contributing to the overall noise level of tracked vehicles.

[0008]
Therefore, it has been contemplated achieving noise reduction through non-uniform spacing of the lugs forming the thread of the ground-engaging surface. It has also been suggested to ensure that the spacing of the external ground engaging lugs is at a different pitch from the spacing of the internal drive lugs (see for example US 5,709,440).

[0009] There is still a need in the art for noiseless rubber tracks.
SUMMARY OF THE INVENTION

[0010] More specifically, there is provided a rubber track for a tracked vehicle, comprising a rubber belt with an inner surface and a ground-engaging surface, the ground-engaging surface comprising a series of traction lugs spaced apart in a longitudinal direction of the track at a first pitch, the inner surface provided with a series of drive lugs spaced apart in the longitudinal direction of the track at a second pitch, wherein the rubber belt comprises at most one reinforcing rod, embedded in a rubber material thereof and extending transversally substantially over an entire width of the track, at every two traction lugs.

[0011] There is further provided a tracked vehicle provided with a rubber track comprising a rubber belt with an inner surface and a ground-engaging surface, the ground-engaging surface comprising a series of traction lugs regularly spaced apart in a longitudinal direction of the track at a first pitch, the inner surface provided with a series of drive lugs spaced apart in the longitudinal direction of the track at a second pitch, wherein the rubber belt comprises at most one reinforcing rod, embedded in a rubber material thereof and extending transversally substantially over an entire width of the track, at every two traction lugs.

[0012] According to a broad aspect, the invention provides an endless track for traction of a snowmobile or vehicle, the endless track comprising: an inner side for facing a set of wheels of the snowmobile or vehicle, the set of wheels comprising a drive wheel for imparting motion of the endless track; a ground-engaging outer side for engaging the ground, the ground-engaging outer side having traction projections spaced apart along a longitudinal direction of the endless track, each traction projection comprising elastomeric material that contacts the ground when the traction projection contacts the ground; and reinforcing rods embedded between the inner side and the ground-engaging outer side, the reinforcing rods being spaced apart along the longitudinal direction of the endless track and extending transversally to the longitudinal direction of the endless track to provide transverse rigidity to the endless track. Along the longitudinal direction of the endless track, a spacing of successive reinforcing rods is different from a spacing of successive traction projections such that, when the snowmobile or vehicle is operated at a given speed, less noise is generated than if the inner side was unchanged and the ground-engaging outer side was unchanged but the spacing of successive reinforcing rods was identical to the spacing of successive traction projections.

[0013] According to another broad aspect, the invention provides an endless track for traction of a snowmobile or vehicle, the snowmobile or vehicle comprising a track-engaging part for engaging the endless track, the track-engaging part of the snowmobile or vehicle comprising a set of wheels, the set of wheels comprising a drive wheel for imparting motion of the endless track around the track-engaging part of the snowmobile or vehicle, the endless track comprising: an inner side for facing the track-engaging part of the snowmobile or vehicle, the inner side having inner projections spaced apart along a longitudinal direction of the endless track, each inner projection comprising elastomeric material that contacts the track-engaging part of the snowmobile or vehicle when the inner projection contacts the track-engaging part of the snowmobile or vehicle; a ground-engaging outer side for engaging the ground, the ground-engaging outer side having traction projections spaced apart along the longitudinal direction of the endless track, each traction projection comprising elastomeric material that contacts the ground when the traction projection engages the ground; and reinforcing rods embedded between the inner side and the ground-engaging outer side and spaced apart along the longitudinal direction of the endless track, the reinforcing rods extending transversally to the longitudinal direction of the endless track to provide transverse rigidity to the endless track. Along the longitudinal direction of the endless track, a reinforcing rod is located where an inner projection is located. Moreover, a spacing of successive reinforcing rods is greater than a spacing of successive traction projections, and at least one inner projection and at least one traction projection are located between successive reinforcing rods.

[0014] According to another broad aspect, the invention provides an endless track for traction of a snowmobile or vehicle, the endless track comprising:
an inner side for engaging a plurality of wheels of the snowmobile or vehicle, the inner side comprising a plurality of wheel-contacting projections, each wheel-contacting projection comprising elastomeric material that contacts a given one of the wheels when the wheel-contacting projection contacts the given one of the wheels; a ground-engaging outer side for engaging the ground, the ground-engaging outer side comprising a plurality of traction projections spaced apart along a longitudinal direction of the endless track; and a plurality of reinforcing rods embedded in the endless track, the reinforcing rods being spaced apart along the longitudinal direction of the endless track and extending transversally to the longitudinal direction of the endless track to provide transverse rigidity to the endless track.
Along the longitudinal direction of the endless track, a given one of the reinforcing rods is located where a given one of the wheel-contacting projections is located.
Moreover, a spacing of successive ones of the reinforcing rods is greater than a spacing of successive ones of the traction projections, and at least one of the traction 5 projections and at least one of the wheel-contacting projections are located between successive ones of the reinforcing rods.

[0015] According to another broad aspect, the invention provides an endless track for traction of a snowmobile or vehicle, the endless track comprising:
an inner side for engaging a plurality of wheels of the snowmobile or vehicle, the wheels including a drive wheel for imparting motion to the endless track, the inner side comprising a wheel-engaging portion for engaging the drive wheel, the wheel-engaging portion comprising rubber material that contacts the drive wheel when the wheel-engaging portion engages the drive wheel; a ground-engaging outer side for engaging the ground, the ground-engaging outer side comprising a plurality of traction lugs projecting outwardly and spaced apart along a longitudinal direction of the endless track; and a plurality of reinforcing rods embedded in the endless track, the reinforcing rods being spaced apart along the longitudinal direction of the endless track and extending transversally to the longitudinal direction of the endless track to provide transverse rigidity to the endless track. Along the longitudinal direction of the endless track, a spacing of successive ones of the reinforcing rods is sufficiently different from a spacing of successive ones of the traction lugs such that, when the snowmobile or vehicle is operated at a speed of 50 miles per hour, a frequency spectrum of generated noise manifests a highest noise level that is at least 2 dB less than if the wheel-engaging portion was unchanged and the traction lugs were unchanged but the spacing of successive ones of the reinforcing rods was identical to the spacing of successive ones of the traction lugs.

[0016] According to another broad aspect, the invention provides a method for manufacturing an endless track for a snowmobile or vehicle with a reduced noise profile. The endless track comprises: an inner side for engaging a plurality of wheels =

of the snowmobile or vehicle, the wheels including a drive wheel for imparting motion to the endless track, the inner side comprising a wheel-engaging portion for engaging the drive wheel, the wheel-engaging portion comprising rubber material that contacts the drive wheel when the wheel-engaging portion engages the drive wheel; a ground-engaging outer side for engaging the ground, the ground-engaging outer side comprising a plurality of traction lugs projecting outwardly and spaced apart along a longitudinal direction of the endless track; and a plurality of reinforcing rods embedded in the endless track, the reinforcing rods being spaced apart along the longitudinal direction of the endless track and extending transversally to the longitudinal direction of the endless track to provide transverse rigidity to the endless track. The method comprises: designing the structure of the endless track, the designing including selecting the pitch of the reinforcing rods with relation to the pitch of the traction lugs such that, when the snowmobile or vehicle is operated at a speed of 50 miles per hour, the frequency spectrum of noise produced manifests a highest noise level that is at least 2 dB less than if the wheel-engaging portion was unchanged and the traction lugs were unchanged but the pitch of the reinforcing rods was the same as the pitch of the traction lugs; and manufacturing the endless track according to the designing.

[0017] According to another broad aspect, the invention provides a method for reducing a highest noise level in a frequency spectrum of noise produced when a snowmobile or vehicle is operated at a speed of 50 miles per hour. The snowmobile or vehicle comprises an endless track that comprises: an inner side for engaging a plurality of wheels of the snowmobile or vehicle, the wheels including a drive wheel for imparting motion to the endless track, the inner side comprising a wheel-engaging portion for engaging the drive wheel, the wheel-engaging portion comprising rubber material that contacts the drive wheel when the wheel-engaging portion engages the drive wheel; a ground-engaging outer side for engaging the ground, the ground-engaging outer side comprising a plurality of traction lugs projecting outwardly and spaced apart along a longitudinal direction of the endless track; and a plurality of reinforcing rods embedded in the endless track, the reinforcing rods being spaced apart along the longitudinal direction of the endless track and extending transversally to the longitudinal direction of the endless track to provide transverse rigidity to the endless track. The method comprises:
designing the structure of the endless track, the designing including selecting the pitch of the reinforcing rods such that the pitch of the reinforcing rods exceeds the pitch of the traction lugs by a degree sufficient to reduce the highest noise level by at least 2 dB
in comparison to that which would be produced if the wheel-engaging portion was unchanged and the traction lugs were unchanged but the pitch of the reinforcing rods was the same as the pitch of the traction lugs; manufacturing the endless track according to the designing; installing the endless track on a snowmobile or vehicle;
and driving the snowmobile or vehicle at a speed of 50 miles per hour.
[0017A] According to another broad aspect, the invention provides a track for traction of a vehicle. The track is movable around a plurality of wheels which comprises a drive wheel for imparting motion to the track. The track comprises elastomeric material to be flexible. The track comprises: an inner surface for facing the wheels; a ground-engaging outer surface for engaging the ground; a plurality of wheel-contacting projections projecting from the inner surface and spaced apart in a longitudinal direction of the track, each wheel-contacting projection comprising a portion of the elastomeric material that contacts a given one of the wheels when the wheel-contacting projection contacts the given one of the wheels; a plurality of traction projections projecting from the ground-engaging outer surface and spaced apart in the longitudinal direction of the track, each traction projection comprising a portion of the elastomeric material that contacts the ground when the traction projection engages the ground; and a reinforcing rod extending transversally to the longitudinal direction of the track, disposed within the elastomeric material, and registering with a given one of the wheel-contacting projections in the longitudinal direction of the track. The track is free of reinforcing rods extending transversally to the longitudinal direction of the track at locations of respective ones of the traction projections in the longitudinal direction of the track.

, [0017B] According to another broad aspect, the invention provides a track for traction of a vehicle. The track is movable around a plurality of wheels which comprises a drive wheel for imparting motion to the track. The track comprises elastomeric material to be flexible. The track comprises: an inner surface for facing the wheels; a ground-engaging outer surface for engaging the ground; a plurality of traction projections projecting from the ground-engaging outer surface and spaced apart in a longitudinal direction of the track; and a reinforcing rod extending transversally to the longitudinal direction of the track and disposed within the elastomeric material. The track is free of reinforcing rods extending transversally to the longitudinal direction of the track at locations of consecutive ones of the traction projections in the longitudinal direction of the track.
[0017C] According to another broad aspect, the invention provides a track for traction of a vehicle. The track is movable around a plurality of wheels which comprises a drive wheel for imparting motion to the track. The track comprises elastomeric material to be flexible. The track comprises: an inner surface for facing the wheels; a ground-engaging outer surface for engaging the ground; a plurality of wheel-contacting projections projecting from the inner surface and spaced apart in a longitudinal direction of the track; a plurality of traction projections projecting from the ground-engaging outer surface and spaced apart in the longitudinal direction of the track; and a reinforcing rod extending transversally to the longitudinal direction of the track and disposed within the elastomeric material. The track is free of reinforcing rods extending transversally to the longitudinal direction of the track at locations of consecutive ones of the wheel-contacting projections in the longitudinal direction of the track.

[0018] Other objects, advantages and features of the present invention will become more apparent upon reading of the following non-restrictive description of specific embodiments thereof, given by way of example only with reference to the accompanying drawings.

r BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In the appended drawings:

[0020] Figure 1 is a longitudinal sectional view of a portion of a track as known in the art, viewed in a direction of the track;

[0021] Figures 2A to 2C are sectional views of a portion of a track according to embodiments of the present invention; a) with a reinforcing rod at every two traction lugs; b) with no reinforcing rod; and c) with a reinforcing rod at every three traction lugs;

[0022] Figure 3 is a graph of results of tests, of sound levels (in dB) versus frequency (in Hz), conducted on a track of the prior art (diamonds); on a first track according to an embodiment of the present invention (squares), and on a second track according to an embodiment of the present invention (triangles);

=

[0023] Figure 4 is a graph of results of tests, of sound levels (in dB) versus speed (in mi/hr), conducted on a track of the prior art (squares); on a first track according to an embodiment of the present invention (diamonds), and on a second track according to an embodiment of the present invention (triangles); and

[0024] Figure 5 is a graph of results of tests, of power (in hp) versus speed (in mi/hr), conducted on a track of the prior art (squares); on a first track according to an embodiment of the present invention (diamonds), and on a second track according to an embodiment of the present invention (triangles).
DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0025] Turning to Figure 2A of the appended drawings, a track according to an embodiment of the present invention will now be described.

[0026] Reinforcing rods 24 are embedded in the rubber material of the body of the belt 12, at a pitch spacing 2P multiple of the pitch spacing P of the traction lugs 20, each of which extends transversally over substantially the entire width of the track on the ground-engaging surface 16.

[0027] Figure 3 shows the spectral analysis of the amplitude (in decibels) of the noise produced by a tracked vehicle operating at a speed of about 50 mi/hr, at different frequencies from 300 to 450 Hz. As may be seen, at 360 Hz, the noise generated when using a track as of the prior art, i.e. with reinforcing rods at every traction lug (diamonds in Figure 3 and squares in Figures 4 and 5), is of 101 dB, versus 99 dB (-2) when using a track according to an embodiment of the present invention with reinforcing rods only at every two traction lugs (squares in Figure 3 and diamonds in Figures 4 and 5), and 90 dB (-11) when using a track according to an embodiment of the present invention with reinforcing rods only at every three traction lugs (triangles in Figures 3-5). In the track with a reinforcing rod at every traction lug (Figure 1), the track with a reinforcing rod only at every two traction lugs (Figure 2A), and the track with a reinforcing rod only at every three traction lugs (Figure 20), the traction lugs 20 are unchanged and the wheel-engaging portion, which comprises the drive lugs 18, is unchanged.

[0028] A track with no reinforcing rods (Figure 2B) would see a noise reduction of up to 15 dB.

[0029] Moreover, resistance tests show that, contrary to a general thinking in the field, the rubber body, which, by construction, is flexible in its longitudinal direction, is sufficiently stiffened in the transverse direction by such reinforcing rods only present at every two (2) or three (3) traction lugs 20 for example.

[0030] In the case of no reinforcing rods, the chemical composition and the mechanical resistance of the rubber material reinforced with transverse fibers 50, for the endless belt 12 devoid of reinforcing rods, may be selected to ensure rigidity of the endless belt 12. Such rubber material, with a transverse rigidity much larger than its longitudinal rigidity, allows fabricating a belt with a transverse rigidity high enough for allowing traction of the vehicle, while having a smaller longitudinal rigidity allowing the belt to be driven around the sprocket wheel, thereby reducing resistance to forward movements. A transverse rigidity superior by about 5 to duros to that of rubber usually used in rod-reinforced belts (of a hardness of typically about 60 duros) may be a target.

[0031] If any, the reinforcing rods may be fiberglass reinforced, as known in the art.

[0032] The present tracks allow reducing the level of generated noise.
Moreover, since the number of reinforcement rods is reduced, the tracks are lighter in weight (for example by 1.45 kg based on a prior art track of 15.8 kg, based on a 15' large X 121" long track for example). People in the art will further appreciate that the production time of such tracks is shortened by up to 10%, which further contributes to the decrease of costs.

[0033] As can be seen from Figures 4 and 5, the reduction in noise is achieved by using tracks of the present invention in tracked vehicles of about 17 hp at a speed of about 70 mi/hr. At upper speeds, it is found that the tracks with a reduced number of reinforcing rods are subject to increased vibration.
5 [0034] Such tracks are of particular interest for snowmobiles intended for use in protected environments, such as national parks for example, which have stringent regulations such as speed limits around 40 mi/hr and low noise impact.
[0035] Although the present invention has been described hereinabove by way of specific embodiments thereof, it can be modified, without departing from the 10 nature and teachings of the subject invention as defined in the appended claims.

Claims

11

1. An endless track for traction of a snowmobile, the endless track comprising:
- an inner side for facing a set of wheels of the snowmobile, the set of wheels comprising a drive wheel for imparting motion of the endless track;
- a ground-engaging outer side for engaging the ground, the ground-engaging outer side having traction projections spaced apart along a longitudinal direction of the endless track, each traction projection comprising elastomeric material that contacts the ground when the traction projection contacts the ground;
and - reinforcing rods embedded between the inner side and the ground-engaging outer side, the reinforcing rods being spaced apart along the longitudinal direction of the endless track and extending transversally to the longitudinal direction of the endless track to provide transverse rigidity to the endless track, wherein, along the longitudinal direction of the endless track, a spacing of successive reinforcing rods is different from a spacing of successive traction projections such that, when the snowmobile is operated at a given speed, less noise is generated than if the inner side was unchanged and the ground-engaging outer side was unchanged but the spacing of successive reinforcing rods was identical to the spacing of successive traction projections.

2. An endless track as defined in claim 1, the given speed being between 40 miles per hour and 60 miles per hour.

3. An endless track as defined in claim 1, the given speed being 50 miles per hour.

4. An endless track as defined in claim 1, the given speed being 50 miles per hour, wherein, when the snowmobile is operated at the given speed, a frequency spectrum of generated noise manifests a highest noise level that is less than if the inner side was unchanged and the ground-engaging outer side was unchanged but the spacing of successive reinforcing rods was identical to the spacing of successive traction projections.

5. An endless track as defined in claim 4, the highest noise level being at least 2 dB less than if the inner side was unchanged and the ground-engaging outer side was unchanged but the spacing of successive reinforcing rods was identical to the spacing of successive traction projections.

6. An endless track as defined in claim 4, the highest noise level being more than 2 dB less than if the inner side was unchanged and the ground-engaging outer side was unchanged but the spacing of successive reinforcing rods was identical to the spacing of successive traction projections.

7. An endless track as defined in claim 4, the highest noise level being at a frequency between 300 Hz and 450 Hz.

8. An endless track as defined in any one of claims 1 to 7, the spacing of successive reinforcing rods being greater than the spacing of successive traction projections.

9. An endless track as defined in any one of claims 1 to 8, the spacing of successive reinforcing rods being at least twice the spacing of successive traction projections.

10. An endless track as defined in any one of claims 1 to 9, the spacing of successive reinforcing rods being no less than three times the spacing of successive traction projections.

11. An endless track as defined in any one of claims 1 to 8, the spacing of successive reinforcing rods being a multiple of the spacing of successive traction projections.

12. An endless track as defined in any one of claims 1 to 11, the inner side having wheel-contacting projections spaced apart along the longitudinal direction of the endless track, each wheel-contacting projection comprising elastomeric material that contacts a given one of the wheels when the wheel-contacting projection contacts the given one of the wheels.

13. An endless track as defined in claim 12, the wheel-contacting projections being drive projections, the given one of the wheels being the drive wheel.

14. An endless track as defined in claim 12, wherein, along the longitudinal direction of the endless track, the spacing of successive reinforcing rods is greater than a spacing of successive wheel-contacting projections.

15. An endless track as defined in claim 14, the spacing of successive reinforcing rods being at least twice the spacing of successive wheel-contacting projections.

16. An endless track as defined in claim 14 or 15, the spacing of successive reinforcing rods being no less than three times the spacing of successive wheel-contacting projections.

17. An endless track as defined in any one of claims 1 to 16, the elastomeric material of each traction projection comprising rubber.

18. A snowmobile comprising an endless track as defined in any one of claims 1 to 17.

19. An endless track for traction of a snowmobile, the snowmobile comprising a track-engaging part for engaging the endless track, the track-engaging part of the snowmobile comprising a set of wheels, the set of wheels comprising a drive wheel for imparting motion of the endless track around the track-engaging part of the snowmobile, the endless track comprising:
- an inner side for facing the track-engaging part of the snowmobile, the inner side having inner projections spaced apart along a longitudinal direction of the endless track, each inner projection comprising elastomeric material that contacts the track-engaging part of the snowmobile when the inner projection contacts the track-engaging part of the snowmobile;
- a ground-engaging outer side for engaging the ground, the ground-engaging outer side having traction projections spaced apart along the longitudinal direction of the endless track, each traction projection comprising elastomeric material that contacts the ground when the traction projection engages the ground;
and - reinforcing rods embedded between the inner side and the ground-engaging outer side and spaced apart along the longitudinal direction of the endless track, the reinforcing rods extending transversally to the longitudinal direction of the endless track to provide transverse rigidity to the endless track;
wherein, along the longitudinal direction of the endless track: a reinforcing rod is located where an inner projection is located; a spacing of successive reinforcing rods is greater than a spacing of successive traction projections; and at least one inner projection and at least one traction projection are located between successive reinforcing rods.

20. An endless track as defined in claim 19, wherein, when the snowmobile is operated at a given speed, less noise is generated than if the inner projections were unchanged and the traction projections were unchanged but the spacing of successive reinforcing rods was identical to the spacing of successive traction projections.

21. An endless track as defined in claim 20, the given speed being 50 miles per hour.

22. An endless track as defined in claim 19, wherein, when the snowmobile is operated at a speed of 50 miles per hour, a frequency spectrum of generated noise manifests a highest noise level that is less than if the inner projections were unchanged and the traction projections were unchanged but the spacing of successive reinforcing rods was identical to the spacing of successive traction projections.

23. An endless track as defined in claim 22, the highest noise level being at least 2 dB less than if the inner projections were unchanged and the traction projections were unchanged but the spacing of successive reinforcing rods was identical to the spacing of successive traction projections.

24. An endless track as defined in claim 23, the highest noise level being more than 2 dB less than if the inner projections were unchanged and the traction projections were unchanged but the spacing of successive reinforcing rods was identical to the spacing of successive traction projections.

25. An endless track as defined in any one of claims 22 to 24, the highest noise level being at a frequency between 300 Hz and 450 Hz.

26. An endless track as defined in any one of claims 19 to 25, the spacing of successive reinforcing rods being at least twice the spacing of successive traction projections.

27. An endless track as defined in any one of claims 19 to 26, the spacing of successive reinforcing rods being no less than three times the spacing of successive traction projections.

28. An endless track as defined in any one of claims 19 to 25, the spacing of successive reinforcing rods being a multiple of the spacing of successive traction projections.

29. An endless track as defined in any one of claims 19 to 28, the inner projections comprising wheel-contacting projections for engaging the set of wheels.

30. An endless track as defined in claim 29, the wheel-contacting projections comprising drive projections for engaging the drive wheel.

31. An endless track as defined in any one of claims 19 to 28, wherein, along the longitudinal direction of the endless track, the spacing of successive reinforcing rods is greater than a spacing of successive inner projections.

32. An endless track as defined in claim 31, the spacing of successive reinforcing rods being at least twice the spacing of successive inner projections.

33. An endless track as defined in any one of claims 19 to 32, the elastomeric material comprising rubber.

34. An endless track for traction of a snowmobile, the endless track comprising:
- an inner side for engaging a plurality of wheels of the snowmobile, the inner side comprising a plurality of wheel-contacting projections, each wheel-contacting projection comprising elastomeric material that contacts a given one of the wheels when the wheel-contacting projection contacts the given one of the wheels;
- a ground-engaging outer side for engaging the ground, the ground-engaging outer side comprising a plurality of traction projections spaced apart along a longitudinal direction of the endless track; and - a plurality of reinforcing rods embedded in the endless track, the reinforcing rods being spaced apart along the longitudinal direction of the endless track and extending transversally to the longitudinal direction of the endless track to provide transverse rigidity to the endless track, wherein, along the longitudinal direction of the endless track: a given one of the reinforcing rods is located where a given one of the wheel-contacting projections is located; a spacing of successive ones of the reinforcing rods is greater than a spacing of successive ones of the traction projections; and at least one of the traction projections and at least one of the wheel-contacting projections are located between successive ones of the reinforcing rods.

35. An endless track as defined in claim 34, the spacing of successive ones of the reinforcing rods being sufficiently greater than the spacing of successive ones of the traction projections such that, when the snowmobile is operated at a speed of 50 miles per hour, a frequency spectrum of generated noise manifests a highest noise level that is less than if the wheel-contacting projections were unchanged and the traction projections were unchanged but the spacing of successive ones of the reinforcing rods was identical to the spacing of successive ones of the traction projections.

36. An endless track as defined in claim 35, the highest noise level being at least 2 dB less than if the wheel-contacting projections were unchanged and the traction projections were unchanged but the spacing of successive ones of the reinforcing rods was identical to the spacing of successive ones of the traction projections.

37. An endless track as defined in claim 35, the highest noise level being more than 2 dB less than if the wheel-contacting projections were unchanged and the traction projections were unchanged but the spacing of successive ones of the reinforcing rods was identical to the spacing of successive ones of the traction projections.

38. An endless track as defined in any one of claims 35 to 37, the highest noise level being at a frequency between 300 Hz and 450 Hz.

39. An endless track as defined in any one of claims 34 to 38, wherein, along the longitudinal direction of the endless track, more than one of the traction projections are located between successive ones of the reinforcing rods and more than one of the wheel-contacting projections are located between successive ones of the reinforcing rods.

40. An endless track as defined in any one of claims 34 to 38, the spacing of successive ones of the reinforcing rods being at least twice the spacing of successive ones of the traction projections.

41. An endless track as defined in claim 40, the spacing of successive ones of the reinforcing rods being no less than three times the spacing of successive ones of the traction projections.

42. An endless track as defined in any one of claims 34 to 38, the spacing of successive ones of the reinforcing rods being a multiple of the spacing of successive ones of the traction projections.

43. An endless track as defined in any one of claims 34 to 38, the given one of the reinforcing rods being a first given one of the reinforcing rods, the given one of the wheel-contacting projections being a first given one of the wheel-contacting projections, wherein, along the longitudinal direction of the endless track, a second given one of the reinforcing rods is located where a second given one of the wheel-contacting projections is located.

44. An endless track as defined in any one of claims 34 to 42, the given one of the wheels being a drive wheel for imparting motion to the endless track, the wheel-contacting projections being drive projections spaced apart along the longitudinal direction of the endless track.

45. An endless track as defined in claim 44, wherein, along the longitudinal direction of the endless track, the spacing of successive ones of the reinforcing rods is greater than a spacing of successive ones of the drive projections.

46. An endless track as defined in claim 45, the spacing of successive ones of the reinforcing rods being at least twice the spacing of successive ones of the drive projections.

47. An endless track as defined in any one of claims 34 to 46, the elastomeric material comprising rubber.

48. A snowmobile comprising an endless track as defined in any one of claims 34 to 47.

49. An endless track for traction of a snowmobile, the endless track comprising:
- an inner side for engaging a plurality of wheels of the snowmobile, the wheels including a drive wheel for imparting motion to the endless track, the inner side comprising a wheel-engaging portion for engaging the drive wheel, the wheel-engaging portion comprising rubber material that contacts the drive wheel when the wheel-engaging portion engages the drive wheel;
- a ground-engaging outer side for engaging the ground, the ground-engaging outer side comprising a plurality of traction lugs projecting outwardly and spaced apart along a longitudinal direction of the endless track; and - a plurality of reinforcing rods embedded in the endless track, the reinforcing rods being spaced apart along the longitudinal direction of the endless track and extending transversally to the longitudinal direction of the endless track to provide transverse rigidity to the endless track, wherein, along the longitudinal direction of the endless track, a spacing of successive ones of the reinforcing rods is sufficiently different from a spacing of successive ones of the traction lugs such that, when the snowmobile is operated at a speed of 50 miles per hour, a frequency spectrum of generated noise manifests a highest noise level that is at least 2 dB less than if the wheel-engaging portion was unchanged and the traction lugs were unchanged but the spacing of successive ones of the reinforcing rods was identical to the spacing of successive ones of the traction lugs.

50. An endless track as defined in claim 49, the spacing of successive ones of the reinforcing rods being greater than the spacing of successive ones of the traction lugs.

51. An endless track as defined in claim 49 or 50, the spacing of successive ones of the reinforcing rods being at least twice the spacing of successive ones of the traction lugs.

52. An endless track as defined in any one of claims 49 to 51, the spacing of successive ones of the reinforcing rods being no less than three times the spacing of successive ones of the traction lugs.

53. An endless track as defined in claim 49 or 50, the spacing of successive ones of the reinforcing rods being a multiple of the spacing of successive ones of the traction lugs.

54. An endless track as defined in any one of claims 49 to 53, the highest noise level being at a frequency between 300 Hz and 450 Hz.

55. An endless track as defined in claim 54, the frequency of the highest noise level being between 330 Hz and 420 Hz.

56. An endless track as defined in claim 55, the frequency of the highest noise level being between 350 Hz and 400 Hz.

57. An endless track as defined in any one of claims 49 to 56, each of the reinforcing rods being aligned with a respective one of the traction lugs.

58. An endless track as defined in any one of claims 49 to 57, the wheel-engaging portion comprising a plurality of drive lugs projecting inwardly and spaced apart along the longitudinal direction of the endless track.

59. An endless track as defined in claim 58, wherein, along the longitudinal direction of the endless track, the spacing of successive ones of the reinforcing rods is greater than a spacing of successive ones of the drive lugs.

60. An endless track as defined in claim 59, the spacing of successive ones of the reinforcing rods being at least twice the spacing of successive ones of the drive lugs.

61. An endless track as defined in claim 58, each of the reinforcing rods being aligned with a respective one of the traction lugs and a respective one of the drive lugs.

62. An endless track as defined in claim 61, each of the traction lugs having a height that is substantially greater than a height of a given one of the drive lugs with which it is aligned.

63. An endless track as defined in any one of claims 49 to 62, the reinforcing rods being reinforced with fiberglass.

64. An endless track as defined in any one of claims 49 to 63, the highest noise level being more than 2 dB less than if the wheel-engaging portion was unchanged and the traction lugs were unchanged but the spacing of successive ones of the reinforcing rods was identical to the spacing of successive ones of the traction lugs.

65. A snowmobile comprising an endless track as defined in any one of claims 49 to 64.

66. A method for manufacturing an endless track for a snowmobile with a reduced noise profile, the endless track comprising: an inner side for engaging a plurality of wheels of the snowmobile, the wheels including a drive wheel for imparting motion to the endless track, the inner side comprising a wheel-engaging portion for engaging the drive wheel, the wheel-engaging portion comprising rubber material that contacts the drive wheel when the wheel-engaging portion engages the drive wheel; a ground-engaging outer side for engaging the ground, the ground-engaging outer side comprising a plurality of traction lugs projecting outwardly and spaced apart along a longitudinal direction of the endless track; and a plurality of reinforcing rods embedded in the endless track, the reinforcing rods being spaced apart along the longitudinal direction of the endless track and extending transversally to the longitudinal direction of the endless track to provide transverse rigidity to the endless track, the method comprising:
- designing the structure of the endless track, the designing including selecting the pitch of the reinforcing rods with relation to the pitch of the traction lugs such that, when the snowmobile is operated at a speed of 50 miles per hour, the frequency spectrum of noise produced manifests a highest noise level that is at least 2 dB less than if the wheel-engaging portion was unchanged and the traction lugs were unchanged but the pitch of the reinforcing rods was the same as the pitch of the traction lugs; and - manufacturing the endless track according to the designing.

67. A method as defined in claim 66, wherein the highest noise level is found in the frequency range between 300 Hz and 450 Hz.

68. A method as defined in claim 67, wherein the highest noise level is found in the frequency range between 330 Hz and 420 Hz.

69. A method as defined in any one of claims 66 to 68, wherein the selecting includes selecting the pitch of the reinforcing rods such that it is larger than the pitch of the traction lugs.

70. A method as defined in any one of claims 66 to 69, wherein the selecting includes selecting the pitch of the reinforcing rods such that it is at least twice the pitch of the traction lugs.

71. A method as defined in any one of claims 66 to 70, wherein the selecting includes selecting the pitch of the reinforcing rods such that it is no less than three times the pitch of the traction lugs.

72. A method as defined in any one of claims 66 to 69, wherein the selecting includes selecting the pitch of the reinforcing rods such that it is a multiple of the pitch of the traction lugs.

73. A method as defined in any one of claims 66 to 72, wherein the designing includes choosing the location of the reinforcing rods with respect to the traction lugs such that each reinforcing rod is aligned with a traction lug.

74. A method as defined in any one of claims 66 to 73, the wheel-engaging portion comprising a plurality of drive lugs projecting inwardly and spaced apart along the longitudinal direction of the endless track.

75. A method for reducing a highest noise level in a frequency spectrum of noise produced when a snowmobile is operated at a speed of 50 miles per hour, the snowmobile comprising an endless track that comprises: an inner side for engaging a plurality of wheels of the snowmobile, the wheels including a drive wheel for imparting motion to the endless track, the inner side comprising a wheel-engaging portion for engaging the drive wheel, the wheel-engaging portion comprising rubber material that contacts the drive wheel when the wheel-engaging portion engages the drive wheel; a ground-engaging outer side for engaging the ground, the ground-engaging outer side comprising a plurality of traction lugs projecting outwardly and spaced apart along a longitudinal direction of the endless track; and a plurality of reinforcing rods embedded in the endless track, the reinforcing rods being spaced apart along the longitudinal direction of the endless track and extending transversally to the longitudinal direction of the endless track to provide transverse rigidity to the endless track, the method comprising:
- designing the structure of the endless track, the designing including selecting the pitch of the reinforcing rods such that the pitch of the reinforcing rods exceeds the pitch of the traction lugs by a degree sufficient to reduce the highest noise level by at least 2 dB in comparison to that which would be produced if the wheel-engaging portion was unchanged and the traction lugs were unchanged but the pitch of the reinforcing rods was the same as the pitch of the traction lugs;
- manufacturing the endless track according to the designing;
installing the endless track on a snowmobile; and - driving the snowmobile at a speed of 50 miles per hour.

76. A method as defined in claim 75, the wheel-engaging portion comprising a plurality of drive lugs projecting inwardly and spaced apart along the longitudinal direction of the endless track.

77. An endless track for traction of a vehicle, the endless track comprising:
an inner side for facing a set of wheels of the vehicle, the set of wheels comprising a drive wheel for imparting motion of the endless track;

a ground-engaging outer side for engaging the ground, the ground-engaging outer side having traction projections spaced apart along a longitudinal direction of the endless track, each traction projection comprising elastomeric material that contacts the ground when the traction projection contacts the ground; and - reinforcing rods embedded between the inner side and the ground-engaging outer side, the reinforcing rods being spaced apart along the longitudinal direction of the endless track and extending transversally to the longitudinal direction of the endless track to provide transverse rigidity to the endless track, wherein, along the longitudinal direction of the endless track, a spacing of successive reinforcing rods is different from a spacing of successive traction projections such that, when the vehicle is operated at a given speed, less noise is generated than if the inner side was unchanged and the ground-engaging outer side was unchanged but the spacing of successive reinforcing rods was identical to the spacing of successive traction projections.

78. An endless track as defined in claim 77, the given speed being between miles per hour and 60 miles per hour.

79. An endless track as defined in claim 77, the given speed being 50 miles per hour.

80. An endless track as defined in claim 77, the given speed being 50 miles per hour, wherein, when the snowmobile is operated at the given speed, a frequency spectrum of generated noise manifests a highest noise level that is less than if the inner side was unchanged and the ground-engaging outer side was unchanged but the spacing of successive reinforcing rods was identical to the spacing of successive traction projections.

81. An endless track as defined in claim 80, the highest noise level being at least 2 dB less than if the inner side was unchanged and the ground-engaging outer side was unchanged but the spacing of successive reinforcing rods was identical to the spacing of successive traction projections.

82. An endless track as defined in claim 80, the highest noise level being more than 2 dB less than if the inner side was unchanged and the ground-engaging outer side was unchanged but the spacing of successive reinforcing rods was identical to the spacing of successive traction projections.

83. An endless track as defined in claim 80, the highest noise level being at a frequency between 300 Hz and 450 Hz.

84. An endless track as defined in any one of claims 77 to 83, the spacing of successive reinforcing rods being greater than the spacing of successive traction projections.

85. An endless track as defined in any one of claims 77 to 84, the spacing of successive reinforcing rods being at least twice the spacing of successive traction projections.

86. An endless track as defined in any one of claims 77 to 85, the spacing of successive reinforcing rods being no less than three times the spacing of successive traction projections.

87. An endless track as defined in any one of claims 77 to 84, the spacing of successive reinforcing rods being a multiple of the spacing of successive traction projections.

88. An endless track as defined in any one of claims 77 to 87, the inner side having wheel-contacting projections spaced apart along the longitudinal direction of the endless track, each wheel-contacting projection comprising elastomeric material that contacts a given one of the wheels when the wheel-contacting projection contacts the given one of the wheels.

89. An endless track as defined in claim 88, the wheel-contacting projections being drive projections, the given one of the wheels being the drive wheel.

90. An endless track as defined in claim 88, wherein, along the longitudinal direction of the endless track, the spacing of successive reinforcing rods is greater than a spacing of successive wheel-contacting projections.

91. An endless track as defined in claim 90, the spacing of successive reinforcing rods being at least twice the spacing of successive wheel-contacting projections.

92. An endless track as defined in claim 90 or 91, the spacing of successive reinforcing rods being no less than three times the spacing of successive wheel-contacting projections.

93. An endless track as defined in any one of claims 77 to 92, the elastomeric material of each traction projection comprising rubber.

94. An endless track as defined in any one of claims 77 to 93, wherein the vehicle is a snowmobile.

95. A snowmobile comprising an endless track as defined in any one of claims 77 to 93.

96. An endless track for traction of a vehicle, the vehicle comprising a track-engaging part for engaging the endless track, the track-engaging part of the vehicle comprising a set of wheels, the set of wheels comprising a drive wheel for imparting motion of the endless track around the track-engaging part of the vehicle, the endless track comprising:
- an inner side for facing the track-engaging part of the vehicle, the inner side having inner projections spaced apart along a longitudinal direction of the endless track, each inner projection comprising elastomeric material that contacts the track-engaging part of the vehicle when the inner projection contacts the track-engaging part of the vehicle;
- a ground-engaging outer side for engaging the ground, the ground-engaging outer side having traction projections spaced apart along the longitudinal direction of the endless track, each traction projection comprising elastomeric material that contacts the ground when the traction projection engages the ground;
and - reinforcing rods embedded between the inner side and the ground-engaging outer side and spaced apart along the longitudinal direction of the endless track, the reinforcing rods extending transversally to the longitudinal direction of the endless track to provide transverse rigidity to the endless track;
wherein, along the longitudinal direction of the endless track: a reinforcing rod is located where an inner projection is located; a spacing of successive reinforcing rods is greater than a spacing of successive traction projections; and at least one inner projection and at least one traction projection are located between successive reinforcing rods.

97. An endless track as defined in claim 96, wherein, when the vehicle is operated at a given speed, less noise is generated than if the inner projections were unchanged and the traction projections were unchanged but the spacing of successive reinforcing rods was identical to the spacing of successive traction projections.

98. An endless track as defined in claim 97, the given speed being 50 miles per hour.

99. An endless track as defined in claim 96, wherein, when the vehicle is operated at a speed of 50 miles per hour, a frequency spectrum of generated noise manifests a highest noise level that is less than if the inner projections were unchanged and the traction projections were unchanged but the spacing of successive reinforcing rods was identical to the spacing of successive traction projections.

100. An endless track as defined in claim 99, the highest noise level being at least 2 dB less than if the inner projections were unchanged and the traction projections were unchanged but the spacing of successive reinforcing rods was identical to the spacing of successive traction projections.

101. An endless track as defined in claim 100, the highest noise level being more than 2 dB less than if the inner projections were unchanged and the traction projections were unchanged but the spacing of successive reinforcing rods was identical to the spacing of successive traction projections.

102. An endless track as defined in any one of claims 99 to 101, the highest noise level being at a frequency between 300 Hz and 450 Hz.

103. An endless track as defined in any one of claims 96 to 102, the spacing of successive reinforcing rods being at least twice the spacing of successive traction projections.

104. An endless track as defined in any one of claims 96 to 103, the spacing of successive reinforcing rods being no less than three times the spacing of successive traction projections.

105. An endless track as defined in any one of claims 96 to 102, the spacing of successive reinforcing rods being a multiple of the spacing of successive traction projections.

106. An endless track as defined in any one of claims 96 to 105, the inner projections comprising wheel-contacting projections for engaging the set of wheels.

107. An endless track as defined in claim 106, the wheel-contacting projections comprising drive projections for engaging the drive wheel.

108. An endless track as defined in any one of claims 96 to 105, wherein, along the longitudinal direction of the endless track, the spacing of successive reinforcing rods is greater than a spacing of successive inner projections.

109. An endless track as defined in claim 108, the spacing of successive reinforcing rods being at least twice the spacing of successive inner projections.

110. An endless track as defined in any one of claims 96 to 109, the elastomeric material comprising rubber.

111. An endless track as defined in any one of claims 96 to 110, wherein the vehicle is a snowmobile.

112. An endless track for traction of a vehicle, the endless track comprising:
an inner side for engaging a plurality of wheels of the vehicle, the inner side comprising a plurality of wheel-contacting projections, each wheel-contacting projection comprising elastomeric material that contacts a given one of the wheels when the wheel-contacting projection contacts the given one of the wheels;
a ground-engaging outer side for engaging the ground, the ground-engaging outer side comprising a plurality of traction projections spaced apart along a longitudinal direction of the endless track; and a plurality of reinforcing rods embedded in the endless track, the reinforcing rods being spaced apart along the longitudinal direction of the endless track and extending transversally to the longitudinal direction of the endless track to provide transverse rigidity to the endless track, wherein, along the longitudinal direction of the endless track: a given one of the reinforcing rods is located where a given one of the wheel-contacting projections is located; a spacing of successive ones of the reinforcing rods is greater than a spacing of successive ones of the traction projections; and at least one of the traction projections and at least one of the wheel-contacting projections are located between successive ones of the reinforcing rods.

113. An endless track as defined in claim 112, the spacing of successive ones of the reinforcing rods being sufficiently greater than the spacing of successive ones of the traction projections such that, when the vehicle is operated at a speed of miles per hour, a frequency spectrum of generated noise manifests a highest noise level that is less than if the wheel-contacting projections were unchanged and the traction projections were unchanged but the spacing of successive ones of the reinforcing rods was identical to the spacing of successive ones of the traction projections.

114. An endless track as defined in claim 113, the highest noise level being at least 2 dB less than if the wheel-contacting projections were unchanged and the traction projections were unchanged but the spacing of successive ones of the reinforcing rods was identical to the spacing of successive ones of the traction projections.

115. An endless track as defined in claim 113, the highest noise level being more than 2 dB less than if the wheel-contacting projections were unchanged and the traction projections were unchanged but the spacing of successive ones of the reinforcing rods was identical to the spacing of successive ones of the traction projections.

116. An endless track as defined in any one of claims 113 to 115, the highest noise level being at a frequency between 300 Hz and 450 Hz.

117. An endless track as defined in any one of claims 112 to 116, wherein, along the longitudinal direction of the endless track, more than one of the traction projections are located between successive ones of the reinforcing rods and more than one of the wheel-contacting projections are located between successive ones of the reinforcing rods.

118. An endless track as defined in any one of claims 112 to 116, the spacing of successive ones of the reinforcing rods being at least twice the spacing of successive ones of the traction projections.

119. An endless track as defined in claim 118, the spacing of successive ones of the reinforcing rods being no less than three times the spacing of successive ones of the traction projections.

120. An endless track as defined in any one of claims 112 to 116, the spacing of successive ones of the reinforcing rods being a multiple of the spacing of successive ones of the traction projections.

121. An endless track as defined in any one of claims 112 to 116, the given one of the reinforcing rods being a first given one of the reinforcing rods, the given one of the wheel-contacting projections being a first given one of the wheel-contacting projections, wherein, along the longitudinal direction of the endless track, a second given one of the reinforcing rods is located where a second given one of the wheel-contacting projections is located.

122. An endless track as defined in any one of claims 112 to 120, the given one of the wheels being a drive wheel for imparting motion to the endless track, the wheel-contacting projections being drive projections spaced apart along the longitudinal direction of the endless track.

123. An endless track as defined in claim 122, wherein, along the longitudinal direction of the endless track, the spacing of successive ones of the reinforcing rods is greater than a spacing of successive ones of the drive projections.

124. An endless track as defined in claim 123, the spacing of successive ones of the reinforcing rods being at least twice the spacing of successive ones of the drive projections.

125. An endless track as defined in any one of claims 112 to 124, the elastomeric material comprising rubber.

126. An endless track as defined in any one of claims 112 to 125, wherein the vehicle is a snowmobile.

127. A snowmobile comprising an endless track as defined in any one of claims 112 to 125.

128. An endless track for traction of a vehicle, the endless track comprising:
- an inner side for engaging a plurality of wheels of the vehicle, the wheels including a drive wheel for imparting motion to the endless track, the inner side comprising a wheel-engaging portion for engaging the drive wheel, the wheel-engaging portion comprising rubber material that contacts the drive wheel when the wheel-engaging portion engages the drive wheel;
- a ground-engaging outer side for engaging the ground, the ground-engaging outer side comprising a plurality of traction lugs projecting outwardly and spaced apart along a longitudinal direction of the endless track; and - a plurality of reinforcing rods embedded in the endless track, the reinforcing rods being spaced apart along the longitudinal direction of the endless track and extending transversally to the longitudinal direction of the endless track to provide transverse rigidity to the endless track, wherein, along the longitudinal direction of the endless track, a spacing of successive ones of the reinforcing rods is sufficiently different from a spacing of successive ones of the traction lugs such that, when the vehicle is operated at a speed of 50 miles per hour, a frequency spectrum of generated noise manifests a highest noise level that is at least 2 dB less than if the wheel-engaging portion was unchanged and the traction lugs were unchanged but the spacing of successive ones of the reinforcing rods was identical to the spacing of successive ones of the traction lugs.

129. An endless track as defined in claim 128, the spacing of successive ones of the reinforcing rods being greater than the spacing of successive ones of the traction lugs.

130. An endless track as defined in claim 128 or 129, the spacing of successive ones of the reinforcing rods being at least twice the spacing of successive ones of the traction lugs.

131. An endless track as defined in any one of claims 128 to 130, the spacing of successive ones of the reinforcing rods being no less than three times the spacing of successive ones of the traction lugs.

132. An endless track as defined in claim 128 or 129, the spacing of successive ones of the reinforcing rods being a multiple of the spacing of successive ones of the traction lugs.

133. An endless track as defined in any one of claims 128 to 132, the highest noise level being at a frequency between 300 Hz and 450 Hz.

134. An endless track as defined in claim 133, the frequency of the highest noise level being between 330 Hz and 420 Hz.

135. An endless track as defined in claim 134, the frequency of the highest noise level being between 350 Hz and 400 Hz.

136. An endless track as defined in any one of claims 128 to 135, each of the reinforcing rods being aligned with a respective one of the traction lugs.

137. An endless track as defined in any one of claims 128 to 136, the wheel-engaging portion comprising a plurality of drive lugs projecting inwardly and spaced apart along the longitudinal direction of the endless track.

138. An endless track as defined in claim 137, wherein, along the longitudinal direction of the endless track, the spacing of successive ones of the reinforcing rods is greater than a spacing of successive ones of the drive lugs.

139. An endless track as defined in claim 138, the spacing of successive ones of the reinforcing rods being at least twice the spacing of successive ones of the drive lugs.

140. An endless track as defined in claim 137, each of the reinforcing rods being aligned with a respective one of the traction lugs and a respective one of the drive lugs.

141. An endless track as defined in claim 140, each of the traction lugs having a height that is substantially greater than a height of a given one of the drive lugs with which it is aligned.

142. An endless track as defined in any one of claims 128 to 141, the reinforcing rods being reinforced with fiberglass.

143. An endless track as defined in any one of claims 128 to 142, the highest noise level being more than 2 dB less than if the wheel-engaging portion was unchanged and the traction lugs were unchanged but the spacing of successive ones of the reinforcing rods was identical to the spacing of successive ones of the traction lugs.

144. An endless track as defined in any one of claims 128 to 143, wherein the vehicle is a snowmobile.

145. A snowmobile comprising an endless track as defined in any one of claims 128 to 143.

146. A method for manufacturing an endless track for a vehicle with a reduced noise profile, the endless track comprising: an inner side for engaging a plurality of wheels of the vehicle, the wheels including a drive wheel for imparting motion to the endless track, the inner side comprising a wheel-engaging portion for engaging the drive wheel, the wheel-engaging portion comprising rubber material that contacts the drive wheel when the wheel-engaging portion engages the drive wheel; a ground-engaging outer side for engaging the ground, the ground-engaging outer side comprising a plurality of traction lugs projecting outwardly and spaced apart along a longitudinal direction of the endless track; and a plurality of reinforcing rods embedded in the endless track, the reinforcing rods being spaced apart along the longitudinal direction of the endless track and extending transversally to the longitudinal direction of the endless track to provide transverse rigidity to the endless track, the method comprising:
- designing the structure of the endless track, the designing including selecting the pitch of the reinforcing rods with relation to the pitch of the traction lugs such that, when the vehicle is operated at a speed of 50 miles per hour, the frequency spectrum of noise produced manifests a highest noise level that is at least 2 dB less than if the wheel-engaging portion was unchanged and the traction lugs were unchanged but the pitch of the reinforcing rods was the same as the pitch of the traction lugs; and - manufacturing the endless track according to the designing.

147. A method as defined in claim 146, wherein the highest noise level is found in the frequency range between 300 Hz and 450 Hz.

148. A method as defined in claim 147, wherein the highest noise level is found in the frequency range between 330 Hz and 420 Hz.

149. A method as defined in any one of claims 146 to 148, wherein the selecting includes selecting the pitch of the reinforcing rods such that it is larger than the pitch of the traction lugs.

150. A method as defined in any one of claims 146 to 149, wherein the selecting includes selecting the pitch of the reinforcing rods such that it is at least twice the pitch of the traction lugs.

151. A method as defined in any one of claims 146 to 150, wherein the selecting includes selecting the pitch of the reinforcing rods such that it is no less than three times the pitch of the traction lugs.

152. A method as defined in any one of claims 146 to 149, wherein the selecting includes selecting the pitch of the reinforcing rods such that it is a multiple of the pitch of the traction lugs.

153. A method as defined in any one of claims 146 to 152, wherein the designing includes choosing the location of the reinforcing rods with respect to the traction lugs such that each reinforcing rod is aligned with a traction lug.

154. A method as defined in any one of claims 146 to 153, the wheel-engaging portion comprising a plurality of drive lugs projecting inwardly and spaced apart along the longitudinal direction of the endless track.

155. A method as defined in any one of claims 146 to 154, wherein the vehicle is a snowmobile.

156. A method for reducing a highest noise level in a frequency spectrum of noise produced when a vehicle is operated at a speed of 50 miles per hour, the vehicle comprising an endless track that comprises: an inner side for engaging a plurality of wheels of the vehicle, the wheels including a drive wheel for imparting motion to the endless track, the inner side comprising a wheel-engaging portion for engaging the drive wheel, the wheel-engaging portion comprising rubber material that contacts the drive wheel when the wheel-engaging portion engages the drive wheel; a ground-engaging outer side for engaging the ground, the ground-engaging outer side comprising a plurality of traction lugs projecting outwardly and spaced apart along a longitudinal direction of the endless track; and a plurality of reinforcing rods embedded in the endless track, the reinforcing rods being spaced apart along the longitudinal direction of the endless track and extending transversally to the longitudinal direction of the endless track to provide transverse rigidity to the endless track, the method comprising:
- designing the structure of the endless track, the designing including selecting the pitch of the reinforcing rods such that the pitch of the reinforcing rods exceeds the pitch of the traction lugs by a degree sufficient to reduce the highest noise level by at least 2 dB in comparison to that which would be produced if the wheel-engaging portion was unchanged and the traction lugs were unchanged but the pitch of the reinforcing rods was the same as the pitch of the traction lugs;
- manufacturing the endless track according to the designing;

- installing the endless track on a vehicle; and - driving the vehicle at a speed of 50 miles per hour.

157. A method as defined in claim 156, the wheel-engaging portion comprising a plurality of drive lugs projecting inwardly and spaced apart along the longitudinal direction of the endless track.

158. A method as defined in any one of claims 156 or 157, wherein the vehicle is a snowmobile.

159. A track for traction of a vehicle, the track being movable around a plurality of wheels which comprises a drive wheel for imparting motion to the track, the track comprising elastomeric material to be flexible, the track comprising:
- an inner surface for facing the wheels;
- a ground-engaging outer surface for engaging the ground;
- a plurality of wheel-contacting projections projecting from the inner surface and spaced apart in a longitudinal direction of the track, each wheel-contacting projection comprising a portion of the elastomeric material that contacts a given one of the wheels when the wheel-contacting projection contacts the given one of the wheels;
- a plurality of traction projections projecting from the ground-engaging outer surface and spaced apart in the longitudinal direction of the track, each traction projection comprising a portion of the elastomeric material that contacts the ground when the traction projection engages the ground; and - a reinforcing rod extending transversally to the longitudinal direction of the track, disposed within the elastomeric material, and registering with a given one of the wheel-contacting projections in the longitudinal direction of the track;
wherein the track is free of reinforcing rods extending transversally to the longitudinal direction of the track at locations of respective ones of the traction projections in the longitudinal direction of the track.

160. A track as defined in claim 159, wherein the wheel-contacting projections are drive projections and the given one of the wheels is the drive wheel.

161. A track as defined in any one of claims 159 and 160, wherein the reinforcing rod registers with a given one of the traction projections in the longitudinal direction of the track.

162. A track as defined in any one of claims 159 to 161, wherein the respective ones of the traction projections are consecutive ones of the traction projections.

163. A track as defined in any one of claims 159 to 162, wherein: the reinforcing rod is a first reinforcing rod; the given one of the wheel-contacting projections is a first given one of the wheel-contacting projections; and the track comprises a second reinforcing rod extending transversally to the longitudinal direction of the track, disposed within the elastomeric material, and registering with a second given one of the wheel-contacting projections in the longitudinal direction of the track.

164. A track as defined in claim 163, wherein at least one of the respective ones of the traction projections is located between the first given one of the wheel-contacting projections and the second given one of the wheel-contacting projections in the longitudinal direction of the track.

165. A track as defined in claim 163, wherein at least two of the respective ones of the traction projections are located between the first given one of the wheel-contacting projections and the second given one of the wheel-contacting projections in the longitudinal direction of the track.

166. A track as defined in any one of claims 159 to 165, wherein a height of each of the traction projections is greater than a height of each of the wheel-contacting projections.

167. A track as defined in any one of claims 159 to 166, wherein, when the vehicle is operated at a certain speed, less noise is generated than if the track had reinforcing rods extending transversally to the longitudinal direction of the track at the locations of the respective ones of the traction projections in the longitudinal direction of the track.

168. A track as defined in claim 167, wherein the certain speed is 50 miles per hour.

169. A track as defined in any one of claims 159 to 166, wherein, when the vehicle is operated at a speed of 50 miles per hour, a frequency spectrum of generated noise manifests a highest noise level that is less than if the track had reinforcing rods extending transversally to the longitudinal direction of the track at the locations of the respective ones of the traction projections in the longitudinal direction of the track.

170. A track as defined in any one of claims 159 to 169, wherein the vehicle is a snowmobile and the track is a snowmobile track.

171. A track system for traction of a vehicle, the track system comprising a plurality of wheels and a track as defined in any one of claims 159 to 169.

172. A track system as defined in claim 171, wherein the vehicle is a snowmobile and the track system is a snowmobile track system.

173. A vehicle comprising a track as defined in any one of claims 159 to 169.

174. A vehicle comprising a track system as defined in claim 171.

175. A vehicle as defined in any one of claims 173 and 174, wherein the vehicle is a snowmobile.

176. A track for traction of a vehicle, the track being movable around a plurality of wheels which comprises a drive wheel for imparting motion to the track, the track comprising elastomeric material to be flexible, the track comprising:
- an inner surface for facing the wheels;
- a ground-engaging outer surface for engaging the ground;
- a plurality of traction projections projecting from the ground-engaging outer surface and spaced apart in a longitudinal direction of the track; and - a reinforcing rod extending transversally to the longitudinal direction of the track and disposed within the elastomeric material;
wherein the track is free of reinforcing rods extending transversally to the longitudinal direction of the track at locations of consecutive ones of the traction projections in the longitudinal direction of the track.

177. A track as defined in claim 176, comprising a plurality of wheel-contacting projections projecting from the inner surface and spaced apart in the longitudinal direction of the track.

178. A track as defined in claim 177, wherein the wheel-contacting projections are drive projections for engaging the drive wheel.

179. A track as defined in any one of claims 176 to 178, wherein the reinforcing rod registers with a given one of the traction projections in the longitudinal direction of the track.

180. A track as defined claim 179, wherein: the reinforcing rod is a first reinforcing rod; the given one of the traction projections is a first given one of the traction projections; and the track comprises a second reinforcing rod extending transversally to the longitudinal direction of the track, disposed within the elastomeric material, and registering with a second given one of the traction projections in the longitudinal direction of the track.

181. A track as defined in any one of claims 177 and 178, wherein the reinforcing rod registers with a given one of the wheel-contacting projections in the longitudinal direction of the track.

182. A track as defined claim 181, wherein: the reinforcing rod is a first reinforcing rod; the given one of the wheel-contacting projections is a first given one of the wheel-contacting projections; and the track comprises a second reinforcing rod extending transversally to the longitudinal direction of the track, disposed within the elastomeric material, and registering with a second given one of the wheel-contacting projections in the longitudinal direction of the track.

183. A track as defined in claim 181, wherein the reinforcing rod registers with a given one of the traction projections in the longitudinal direction of the track.

184. A track as defined claim 183, wherein: the reinforcing rod is a first reinforcing rod; the given one of the wheel-contacting projections is a first given one of the wheel-contacting projections; the given one of the traction projections is a first given one of the traction projections; and the track comprises a second reinforcing rod extending transversally to the longitudinal direction of the track, disposed within the elastomeric material, and registering with a second given one of the wheel-contacting projections and a second given one of the traction projections in the longitudinal direction of the track.

185. A track as defined in any one of claims 177 to 184, wherein a height of each of the traction projections is greater than a height of each of the wheel-contacting projections.

186. A track as defined in any one of claims 176 to 185, wherein, when the vehicle is operated at a certain speed, less noise is generated than if the track had reinforcing rods extending transversally to the longitudinal direction of the track at the locations of the consecutive ones of the traction projections in the longitudinal direction of the track.

187. A track as defined in claim 186, wherein the certain speed is 50 miles per hour.

188. A track as defined in any one of claims 176 to 185, wherein, when the vehicle is operated at a speed of 50 miles per hour, a frequency spectrum of generated noise manifests a highest noise level that is less than if the track had reinforcing rods extending transversally to the longitudinal direction of the track at the locations of the consecutive ones of the traction projections in the longitudinal direction of the track.

189. A track as defined in any one of claims 176 to 188, wherein the vehicle is a snowmobile and the track is a snowmobile track.

190. A track system for traction of a vehicle, the track system comprising a plurality of wheels and a track as defined in any one of claims 176 to 188.

191. A track system as defined in claim 190, wherein the vehicle is a snowmobile and the track system is a snowmobile track system.

192. A vehicle comprising a track as defined in any one of claims 176 to 188.

193. A vehicle comprising a track system as defined in claim 190.

194. A vehicle as defined in any one of claims 192 and 193, wherein the vehicle is a snowmobile.

195. A track for traction of a vehicle, the track being movable around a plurality of wheels which comprises a drive wheel for imparting motion to the track, the track comprising elastomeric material to be flexible, the track comprising:

- an inner surface for facing the wheels;
- a ground-engaging outer surface for engaging the ground;
- a plurality of wheel-contacting projections projecting from the inner surface and spaced apart in a longitudinal direction of the track;
- a plurality of traction projections projecting from the ground-engaging outer surface and spaced apart in the longitudinal direction of the track; and - a reinforcing rod extending transversally to the longitudinal direction of the track and disposed within the elastomeric material;
wherein the track is free of reinforcing rods extending transversally to the longitudinal direction of the track at locations of consecutive ones of the wheel-contacting projections in the longitudinal direction of the track.

196. A track as defined in claim 195, wherein the wheel-contacting projections are drive projections for engaging the drive wheel.

197. A track as defined in any one of claims 195 and 196, wherein the reinforcing rod registers with a given one of the traction projections in the longitudinal direction of the track.

198. A track as defined claim 197, wherein: the reinforcing rod is a first reinforcing rod; the given one of the traction projections is a first given one of the traction projections; and the track comprises a second reinforcing rod extending transversally to the longitudinal direction of the track, disposed within the elastomeric material, and registering with a second given one of the traction projections in the longitudinal direction of the track.

199. A track as defined in any one of claims 195 and 196, wherein the reinforcing rod registers with a given one of the wheel-contacting projections in the longitudinal direction of the track.

200. A track as defined claim 199, wherein: the reinforcing rod is a first reinforcing rod; the given one of the wheel-contacting projections is a first given one of the wheel-contacting projections; and the track comprises a second reinforcing rod extending transversally to the longitudinal direction of the track, disposed within the elastomeric material, and registering with a second given one of the wheel-contacting projections in the longitudinal direction of the track.

201. A track as defined in claim 199, wherein the reinforcing rod registers with a given one of the traction projections in the longitudinal direction of the track.

202. A track as defined claim 201, wherein: the reinforcing rod is a first reinforcing rod; the given one of the wheel-contacting projections is a first given one of the wheel-contacting projections; the given one of the traction projections is a first given one of the traction projections; and the track comprises a second reinforcing rod extending transversally to the longitudinal direction of the track, disposed within the elastomeric material, and registering with a second given one of the wheel-contacting projections and a second given one of the traction projections in the longitudinal direction of the track.

203. A track as defined in any one of claims 195 to 202, wherein a height of each of the traction projections is greater than a height of each of the wheel-contacting projections.

204. A track as defined in any one of claims 195 to 203, wherein, when the vehicle is operated at a certain speed, less noise is generated than if the track had reinforcing rods extending transversally to the longitudinal direction of the track at the locations of the consecutive ones of the wheel-contacting projections in the longitudinal direction of the track.

205. A track as defined in claim 204, wherein the certain speed is 50 miles per hour.

206. A track as defined in any one of claims 195 to 203, wherein, when the vehicle is operated at a speed of 50 miles per hour, a frequency spectrum of generated noise manifests a highest noise level that is less than if the track had reinforcing rods extending transversally to the longitudinal direction of the track at the locations of the consecutive ones of the wheel-contacting projections in the longitudinal direction of the track.

207. A track as defined in any one of claims 195 to 206, wherein the vehicle is a snowmobile and the track is a snowmobile track.

208. A track system for traction of a vehicle, the track system comprising a plurality of wheels and a track as defined in any one of claims 195 to 206.

209. A track system as defined in claim 208, wherein the vehicle is a snowmobile and the track system is a snowmobile track system.

210. A vehicle comprising a track as defined in any one of claims 195 to 206.

211. A vehicle comprising a track system as defined in claim 208.

212. A vehicle as defined in any one of claims 210 and 211, wherein the vehicle is a snowmobile.