US20160200378A1

US20160200378A1 - Track system for traction of an off-road vehicle such as a snowmobile or an all-terrain vehicle (atv)

Info

Publication number: US20160200378A1
Application number: US15/074,819
Authority: US
Inventors: Jules Dandurand; Denis Courtemanche; Pascal Labbé; Linda Poulin
Original assignee: Camso Inc
Current assignee: Camso Inc
Priority date: 2011-11-29
Filing date: 2016-03-18
Publication date: 2016-07-14
Also published as: US20210078655A1; CA2797535C; CA3093117A1; US20130134772A1; US20130134773A1; CA2797535A1

Abstract

A track system for traction of an off-road vehicle such as a snowmobile or an all-terrain vehicle (ATV). The track system comprises a track-engaging assembly and a track disposed around the track-engaging assembly. The track system may be configured to have a reduced noise profile so as to generate less noise, enhanced track rigidity characteristics to improve its traction and floatation, and/or other features improving use and performance of the off-road vehicle.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application of and claims priority to U.S. patent application Ser. No. 13/689,128, filed on Nov. 29, 2012, which claims the benefit under 35 USC 119(e) of U.S. Provisional Patent Application 61/564,630, filed on Nov. 29, 2011 and hereby incorporated by reference herein.

FIELD OF THE INVENTION

The invention relates generally to off-road vehicles such as snowmobiles and all-terrain vehicles (ATV) and, more particularly, to track systems for traction of snowmobiles, ATVs and other off-road vehicles.

BACKGROUND

Snowmobiles allow efficient travel on snowy and in some cases icy grounds. A snowmobile comprises a track system which engages the ground to provide traction. The track system comprises a track-engaging assembly and an endless track that moves around the track-engaging assembly and engages the ground to generate traction. The endless track typically comprises an elastomeric body in which are embedded certain reinforcements, such as transversal stiffening rods providing transversal rigidity to the track, longitudinal cables providing tensional strength, and/or fabric layers. The track-engaging assembly comprises wheels and in some cases slide rails around which the endless track is driven.
Various considerations are important when it comes to a snowmobile's use and performance.
For example, a snowmobile generates noise, including noise generated by its track system. Various factors may contribute to the noise generated by the snowmobile's track system. For instance, in some cases: impacts between roller and/or other wheels of the track-engaging assembly and the transversal stiffening rods of the endless track; impacts between the slide rails and the transversal stiffening rods of the endless track; impacts between the slide rails and slide members (e.g., “clips”) of the endless track, if any; impacts between the ground and traction projections of a ground-engaging outer side of the endless track; and contact between the endless track and drive wheels of the track-engaging assembly may contribute to the noise generated by the snowmobile's track system.
As another example, traction and floatation provided by a snowmobile's track system depend on rigidity of the track system's endless track. While longitudinal flexibility of the track is desirable in order to efficiently drive the track around the track-engaging assembly, transversal rigidity of the track is desirable in order to have a proper ground-contacting area for traction and floatation.
Similar considerations may be important for all-terrain vehicles (ATVs) equipped with track systems having endless tracks providing traction to the ATVs on the ground (e.g., an ATV equipped with two front track systems in place of two front wheels and two rear track systems in place of two rear wheels) and/or for other types of off-road vehicles.
While certain developments have been made to improve performance of track systems of snowmobiles, ATVs and other off-road vehicles, there remains a need for improvements in such track systems.

SUMMARY OF THE INVENTION

In accordance with an aspect of the invention, there is provided a track for traction of an off-road vehicle. The track is mountable around a track-engaging assembly of the off-road vehicle. The track-engaging assembly comprises a drive wheel for driving the track. The track is elastomeric to be flexible around the track-engaging assembly. The track comprises an inner surface for facing the track-engaging assembly, a ground-engaging outer surface for engaging the ground, and a plurality of traction projections projecting from the ground-engaging outer surface. The track also comprises a plurality of stiffening rods extending transversally to a longitudinal direction of the track. Each stiffening rod of the plurality of stiffening rods has a cross-section perpendicular to a longitudinal axis of the stiffening rod. The cross-section of the stiffening rod is elongate.
In accordance with another aspect of the invention, there is provided a track for traction of an off-road vehicle. The track is mountable around a track-engaging assembly of the off-road vehicle. The track-engaging assembly comprises a drive wheel for driving the track. The track is elastomeric to be flexible around the track-engaging assembly. The track comprises an inner surface for facing the track-engaging assembly, a ground-engaging outer surface for engaging the ground, and a plurality of traction projections projecting from the ground-engaging outer surface. The track also comprises a plurality of stiffening rods extending transversally to a longitudinal direction of the track. Each stiffening rod of the plurality of stiffening rods has a cross-section perpendicular to a longitudinal axis of the stiffening rod. The cross-section of the stiffening rod has an aspect ratio of at least 4.
In accordance with another aspect of the invention, there is provided a track for traction of an off-road vehicle. The track is mountable around a track-engaging assembly of the off-road vehicle. The track-engaging assembly comprises a drive wheel for driving the track. The track is elastomeric to be flexible around the track-engaging assembly. The track comprises an inner surface for facing the track-engaging assembly, a ground-engaging outer surface for engaging the ground, and a plurality of traction projections projecting from the ground-engaging outer surface. The track also comprises a plurality of stiffening rods extending transversally to a longitudinal direction of the track. Each stiffening rod of the plurality of stiffening rods has a cross-section perpendicular to a longitudinal axis of the stiffening rod. A ratio of (i) a thickness of the cross-section of the stiffening rod in a thickness direction of the track over (ii) a thickness of a carcass of the track from the inner surface to the ground-engaging outer surface in the thickness direction of the track is less than 0.7.
In accordance with another aspect of the invention, there is provided a track for traction of an off-road vehicle. The track is mountable around a track-engaging assembly of the off-road vehicle. The track-engaging assembly comprises a drive wheel for driving the track. The track is elastomeric to be flexible around the track-engaging assembly. The track comprises an inner surface for facing the track-engaging assembly, a ground-engaging outer surface for engaging the ground, and a plurality of traction projections projecting from the ground-engaging outer surface. The track also comprises a plurality of stiffening rods extending transversally to a longitudinal direction of the track. Each stiffening rod of the plurality of stiffening rods has a cross-section perpendicular to a longitudinal axis of the stiffening rod. A thickness of the cross-section of the stiffening rod in a thickness direction of the track is less than 3.5 mm.
In accordance with another aspect of the invention, there is provided a track for traction of an off-road vehicle. The track is mountable around a track-engaging assembly of the off-road vehicle. The track-engaging assembly comprises a drive wheel for driving the track. The track is elastomeric to be flexible around the track-engaging assembly. The track comprises an inner surface for facing the track-engaging assembly, a ground-engaging outer surface for engaging the ground, and a plurality of traction projections projecting from the ground-engaging outer surface. The track is free of reinforcing fabric between the inner surface and the ground-engaging outer surface along at least part of a length of the track.
In accordance with another aspect of the invention, there is provided a track for traction of an off-road vehicle. The track is mountable around a track-engaging assembly of the off-road vehicle. The track-engaging assembly comprises a drive wheel for driving the track. The track is elastomeric to be flexible around the track-engaging assembly. The track comprises an inner surface for facing the track-engaging assembly, a ground-engaging outer surface for engaging the ground, and a plurality of traction projections projecting from the ground-engaging outer surface. The track is free of reinforcing fabric.
In accordance with another aspect of the invention, there is provided a track for traction of an off-road vehicle. The track is mountable around a track-engaging assembly of the off-road vehicle. The track-engaging assembly comprises a drive wheel for driving the track. The track is elastomeric to be flexible around the track-engaging assembly. The track comprises an inner surface for facing the track-engaging assembly, a ground-engaging outer surface for engaging the ground, and a plurality of traction projections projecting from the ground-engaging outer surface. A thickness of the track from the inner surface to the ground-engaging outer surface is no more than 0.25 inches. The track is free of reinforcing fabric between the inner surface and the ground-engaging outer surface along at least part of a length of the track.
In accordance with another aspect of the invention, there is provided a track for traction of an off-road vehicle. The track is mountable around a track-engaging assembly of the off-road vehicle. The track-engaging assembly comprises a drive wheel for driving the track. The track is elastomeric to be flexible around the track-engaging assembly. The track comprises an inner surface for facing the track-engaging assembly, a ground-engaging outer surface for engaging the ground, and a plurality of traction projections projecting from the ground-engaging outer surface. The track also comprises a plurality of stiffening rods extending transversally to a longitudinal direction of the track. Each stiffening rod of the plurality of stiffening rods comprises a cavity.
In accordance with another aspect of the invention, there is provided a track for traction of an off-road vehicle. The track is mountable around a track-engaging assembly of the off-road vehicle. The track-engaging assembly comprises a drive wheel for driving the track and an idler wheel for contacting the track. The track is elastomeric to be flexible around the track-engaging assembly. The track comprises an inner surface for facing the track-engaging assembly, a ground-engaging outer surface for engaging the ground, and a plurality of traction projections projecting from the ground-engaging outer surface. The inner surface comprises an idler wheel path for the idler wheel. The track also comprises a plurality of stiffening rods extending transversally to a longitudinal direction of the track. Each stiffening rod of the plurality of stiffening rods comprises a recess aligned with the idler wheel path.
In accordance with another aspect of the invention, there is provided a track for traction of an off-road vehicle. The track is mountable around a track-engaging assembly of the off-road vehicle. The track-engaging assembly comprises a drive wheel for driving the track. The track is elastomeric to be flexible around the track-engaging assembly. The track comprises an inner surface for facing the track-engaging assembly, a ground-engaging outer surface for engaging the ground, and a plurality of traction projections projecting from the ground-engaging outer surface. The track also comprises a plurality of stiffening rods extending transversally to a longitudinal direction of the track. Each stiffening rod of the plurality of stiffening rods is shaped such that a thickness of elastomeric material between (i) the inner surface and (ii) a surface of the stiffening rod facing the inner surface varies in the longitudinal direction of the track.
In accordance with another aspect of the invention, there is provided a track for traction of an off-road vehicle. The track is mountable around a track-engaging assembly of the off-road vehicle. The track-engaging assembly comprises a drive wheel for driving the track. The track is elastomeric to be flexible around the track-engaging assembly. The track comprises an inner surface for facing the track-engaging assembly, a ground-engaging outer surface for engaging the ground, and a plurality of traction projections projecting from the ground-engaging outer surface. The track also comprises a plurality of stiffening rods extending transversally to a longitudinal direction of the track. Each stiffening rod of the plurality of stiffening rods is dimensioned such that the stiffening rod does not extend beneath laterally-outmost track-contacting devices of the track-engaging assembly.
In accordance with another aspect of the invention, there is provided a track for traction of an off-road vehicle. The track is mountable around a track-engaging assembly of the off-road vehicle. The track-engaging assembly comprises a drive wheel for driving the track. The track is elastomeric to be flexible around the track-engaging assembly. The track comprises an inner surface for facing the track-engaging assembly, a ground-engaging outer surface for engaging the ground, and a plurality of traction projections projecting from the ground-engaging outer surface. The track also comprises a plurality of stiffening rods extending transversally to a longitudinal direction of the track. A first one of the stiffening rods and a second one of the stiffening rods being stacked in a thickness direction of the track.
In accordance with another aspect of the invention, there is provided a track for traction of an off-road vehicle. The track is mountable around a track-engaging assembly of the off-road vehicle. The track-engaging assembly comprises a drive wheel for driving the track. The track is elastomeric to be flexible around the track-engaging assembly. The track comprises an inner surface for facing the track-engaging assembly, a ground-engaging outer surface for engaging the ground, and a plurality of traction projections projecting from the ground-engaging outer surface. The track also comprises a plurality of stiffening rods extending transversally to a longitudinal direction of the track. A given one of the stiffening rods is located between adjacent ones of the traction projections in the longitudinal direction of the track.
In accordance with another aspect of the invention, there is provided a track for traction of an off-road vehicle. The track is mountable around a track-engaging assembly of the off-road vehicle. The track-engaging assembly comprises a drive wheel for driving the track. The track is elastomeric to be flexible around the track-engaging assembly. The track comprises an inner surface for facing the track-engaging assembly, a ground-engaging outer surface for engaging the ground, and a plurality of traction projections projecting from the ground-engaging outer surface. The track also comprises a plurality of stiffening rods extending transversally to a longitudinal direction of the track. A first one of the stiffening rods is different from a second one of the stiffening rods that succeeds the first one of the stiffening rods in the longitudinal direction of the track.
In accordance with another aspect of the invention, there is provided a track for traction of an off-road vehicle. The track is mountable around a track-engaging assembly of the off-road vehicle. The track-engaging assembly comprises a drive wheel for driving the track. The track is elastomeric to be flexible around the track-engaging assembly. The track comprises an inner surface for facing the track-engaging assembly, a ground-engaging outer surface for engaging the ground, and a plurality of traction projections projecting from the ground-engaging outer surface. The track also comprises a plurality of stiffening rods extending transversally to a longitudinal direction of the track. The plurality of stiffening rods includes an elastomeric fiber-reinforced rod.
In accordance with another aspect of the invention, there is provided a track for traction of an off-road vehicle. The track is mountable around a track-engaging assembly of the off-road vehicle. The track-engaging assembly comprises a drive wheel for driving the track. The track is elastomeric to be flexible around the track-engaging assembly. The track comprises an inner side for facing the track-engaging assembly and a ground-engaging outer side for engaging the ground. The ground-engaging outer side comprises a ground-engaging outer surface and a plurality of traction projections projecting from the ground-engaging outer surface. Elastomeric material of the ground-engaging outer side is different from elastomeric material between the inner side and the ground-engaging outer side such that at least one of: a hardness of the elastomeric material of the ground-engaging outer side is lower than a hardness of the elastomeric material between the inner side and the ground-engaging outer side; and a modulus of elasticity of the elastomeric material of the ground-engaging outer side is lower than a modulus of elasticity of the elastomeric material between the inner side and the ground-engaging outer side.
In accordance with another aspect of the invention, there is provided a track for traction of an off-road vehicle. The track is mountable around a track-engaging assembly of the off-road vehicle. The track-engaging assembly comprises a drive wheel for driving the track and an idler wheel for contacting the track. The track is elastomeric to be flexible around the track-engaging assembly. The track comprises an inner surface for facing the track-engaging assembly, a ground-engaging outer surface for engaging the ground, and a plurality of traction projections projecting from the ground-engaging outer surface. The inner surface comprises an idler wheel path for the idler wheel. A shock absorbency of the track at a widthwise position of the idler wheel path is greater than a shock absorbency of the track at a widthwise position outside the idler wheel path.
In accordance with another aspect of the invention, there is provided a track for traction of an off-road vehicle. The track is mountable around a track-engaging assembly of the off-road vehicle. The track-engaging assembly comprises a drive wheel for driving the track and an idler wheel for contacting the track. The track is elastomeric to be flexible around the track-engaging assembly. The track comprises an inner surface for facing the track-engaging assembly, a ground-engaging outer surface for engaging the ground, and a plurality of traction projections projecting from the ground-engaging outer surface. Elastomeric material at a widthwise position of the idler wheel path is different from elastomeric material at a widthwise position outside the idler wheel path such that at least one of: a hardness of the elastomeric material at the widthwise position of the idler wheel path is lower than a hardness of the elastomeric material at the widthwise position outside the idler wheel path; and a modulus of elasticity of the elastomeric material at the widthwise position of the idler wheel path is lower than a modulus of elasticity of the elastomeric material at the widthwise position outside the idler wheel path.
In accordance with another aspect of the invention, there is provided a track for traction of an off-road vehicle. The track is mountable around a track-engaging assembly of the off-road vehicle. The track-engaging assembly comprises a drive wheel for driving the track. The track is elastomeric to be flexible around the track-engaging assembly. The track comprises an inner surface for facing the track-engaging assembly, a ground-engaging outer surface for engaging the ground, and a plurality of traction projections projecting from the ground-engaging outer surface. The track also comprises a layer of stiffening cables extending transversally to a longitudinal direction of the track.
In accordance with another aspect of the invention, there is provided a track for traction of an off-road vehicle. The track is mountable around a track-engaging assembly of the off-road vehicle. The track-engaging assembly comprises a drive wheel for driving the track. The track is elastomeric to be flexible around the track-engaging assembly. The track comprises an inner surface for facing the track-engaging assembly, a ground-engaging outer surface for engaging the ground, and a plurality of traction projections projecting from the ground-engaging outer surface. The track also comprises a plurality of stiffening rods extending transversally to a longitudinal direction of the track. The track further comprises a layer of stiffening cables extending transversally to the longitudinal direction of the track.
In accordance with another aspect of the invention, there is provided a track for traction of an off-road vehicle. The track is mountable around a track-engaging assembly of the off-road vehicle. The track-engaging assembly comprises a drive wheel for driving the track and an idler wheel for contacting the track. The track is elastomeric to be flexible around the track-engaging assembly. The track comprises an inner surface for facing the track-engaging assembly, a ground-engaging outer surface for engaging the ground, and a plurality of traction projections projecting from the ground-engaging outer surface. The ground-engaging outer surface defines an idler wheel path projection that is located between adjacent ones of the traction projections in a longitudinal direction of the track and that is aligned with the idler wheel path in a widthwise direction of the track.
In accordance with another aspect of the invention, there is provided a track for traction of an off-road vehicle. The track is mountable around a track-engaging assembly of the off-road vehicle. The track-engaging assembly comprises a drive wheel for driving the track. The track is elastomeric to be flexible around the track-engaging assembly. The track comprises an inner surface for facing the track-engaging assembly, a ground-engaging outer surface for engaging the ground, and a plurality of traction projections projecting from the ground-engaging outer surface. At least one of the inner surface and the ground-engaging outer surface comprises a plurality of longitudinal rigidifiers for imparting longitudinal rigidity to the track.
In accordance with another aspect of the invention, there is provided a track for traction of an off-road vehicle. The track is mountable around a track-engaging assembly of the off-road vehicle. The track-engaging assembly comprises a drive wheel for driving the track and an idler wheel for contacting the track. The track is elastomeric to be flexible around the track-engaging assembly. The track comprises an inner surface for facing the track-engaging assembly, a ground-engaging outer surface for engaging the ground, and a plurality of traction projections projecting from the ground-engaging outer surface. The inner surface comprises an idler wheel path for the idler wheel. The idler wheel path is uneven in a longitudinal direction of the track.
In accordance with another aspect of the invention, there is provided a track for traction of an off-road vehicle. The track is mountable around a track-engaging assembly of the off-road vehicle. The track-engaging assembly comprises a drive wheel for driving the track. The track is elastomeric to be flexible around the track-engaging assembly. The track comprises an inner surface for facing the track-engaging assembly, a ground-engaging outer surface for engaging the ground, and a plurality of traction projections projecting from the ground-engaging outer surface. The track is at least mainly made of fiber-reinforced elastomeric material.
In accordance with another aspect of the invention, there is provided a track for traction of an off-road vehicle. The track is mountable around a track-engaging assembly of the off-road vehicle. The track-engaging assembly comprises a drive wheel for driving the track and an idler wheel for contacting the track. The track is elastomeric to be flexible around the track-engaging assembly. The track comprises an inner surface for facing the track-engaging assembly, a ground-engaging outer surface for engaging the ground, and a plurality of traction projections projecting from the ground-engaging outer surface. Cellular elastomeric material is located at a widthwise position of the idler wheel path.
In accordance with another aspect of the invention, there is provided a track-engaging assembly for a track system providing traction of an off-road vehicle. The track-engaging assembly is configured to engage a track disposed around the track-engaging assembly. The track is elastomeric to be flexible around the track-engaging assembly. The track comprises: an inner surface for facing the track-engaging assembly, the inner surface comprising an idler wheel path; a ground-engaging outer surface for engaging the ground; and a plurality of traction projections projecting from the ground-engaging outer surface. The track-engaging assembly comprises a drive wheel for driving the track and a plurality of idler wheels for contacting the track. The plurality of idler wheels includes a set of idler wheels spaced apart in a longitudinal direction of the track system and disposed to roll on the idler wheel path of the track. The set of idler wheels is arranged such that a longitudinal spacing of any two successive idler wheels of the set of idler wheels is less than half of a length of the track system.
In accordance with another aspect of the invention, there is provided a track-engaging assembly for a track system providing traction of an off-road vehicle. The track-engaging assembly is configured to engage a track disposed around the track-engaging assembly. The track is elastomeric to be flexible around the track-engaging assembly. The track comprises: an inner surface for facing the track-engaging assembly, the inner surface comprising an idler wheel path; a ground-engaging outer surface for engaging the ground; and a plurality of traction projections projecting from the ground-engaging outer surface. The track-engaging assembly comprises a drive wheel for driving the track and a plurality of idler wheels for contacting the track. The plurality of idler wheels includes at least four idler wheels spaced apart in a longitudinal direction of the track and disposed to roll on the idler wheel path of the track.
In accordance with another aspect of the invention, there is provided a track-engaging assembly for a track system providing traction of an off-road vehicle. The track-engaging assembly is configured to engage a track disposed around the track-engaging assembly. The track is elastomeric to be flexible around the track-engaging assembly. The track comprises an inner surface for facing the track-engaging assembly, a ground-engaging outer surface for engaging the ground, and a plurality of traction projections projecting from the ground-engaging outer surface. The track-engaging assembly comprises a drive wheel for driving the track and a plurality of side rails spaced apart in a widthwise direction of the track system to slide against a bottom run of the track. The plurality of side rails is arranged such that a widthwise spacing of any two adjacent slide rails of the plurality of side rails is less than half of a width of the track system.
In accordance with another aspect of the invention, there is provided a track-engaging assembly for a track system providing traction of an off-road vehicle. The track-engaging assembly is configured to engage a track disposed around the track-engaging assembly. The track is elastomeric to be flexible around the track-engaging assembly. The track comprises an inner surface for facing the track-engaging assembly, a ground-engaging outer surface for engaging the ground, and a plurality of traction projections projecting from the ground-engaging outer surface. The track-engaging assembly comprises a drive wheel for driving the track and a plurality of side rails spaced apart in a widthwise direction of the track system to slide against a bottom run of the track. The plurality of side rails includes at least three slide rails.
In accordance with another aspect of the invention, there is provided a track-engaging assembly for a track system providing traction of an off-road vehicle. The track-engaging assembly is configured to engage a track disposed around the track-engaging assembly. The track is elastomeric to be flexible around the track-engaging assembly. The track comprises an inner surface for facing the track-engaging assembly, a ground-engaging outer surface for engaging the ground, and a plurality of traction projections projecting from the ground-engaging outer surface. The track-engaging assembly comprises a drive wheel for driving the track and an idler wheel for contacting a bottom run of the track. The track-engaging assembly also comprises a track tensioner for maintaining a tension of the track.
In accordance with another aspect of the invention, there is provided a track-engaging assembly for a track system providing traction of an off-road vehicle. The track-engaging assembly is configured to engage a track disposed around the track-engaging assembly. The track is elastomeric to be flexible around the track-engaging assembly. The track comprises an inner surface for facing the track-engaging assembly, a ground-engaging outer surface for engaging the ground, and a plurality of traction projections projecting from the ground-engaging outer surface. The track-engaging assembly comprises a drive wheel for driving the track and an idler wheel for contacting a bottom run of the track. The track-engaging assembly also comprises a track tensioner for maintaining a tension of the track. The track tensioner comprises a resilient device for contacting a segment of a top run of the track.
These and other aspects of the invention will now become apparent to those of ordinary skill in the art upon review of the following description of embodiments of the invention in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

A detailed description of embodiments of the invention is provided below, by way of example only, with reference to the accompanying drawings, in which:

FIG. 1 shows an example of a snowmobile comprising a track system in accordance with an embodiment of the invention;

FIG. 2 shows a perspective view of components of the track system;

FIG. 3 shows a perspective view of part of a track of the track system;

FIGS. 4 to 7A respectively show an elevation view, a plan view of an inner side, a longitudinal cross-sectional view, and a widthwise cross-sectional view of part of the track;

FIGS. 7B to 7D shows a widthwise cross-sectional view of part of the track according to other embodiments of the invention;

FIGS. 8 and 9 respectively show the track with and without a slide member;

FIGS. 10 to 21 show different shapes of transversal stiffening rods of the track in accordance with various embodiments of the invention;

FIGS. 22A to 25 show different arrangements of transversal stiffening rods of the track in accordance with various embodiments of the invention;

FIG. 26 shows a reinforced elastomeric transversal stiffening rod in accordance with an embodiment of the invention;

FIGS. 27 to 31 show zones of the track with different properties in accordance with various embodiments of the invention;

FIGS. 32A to 32D show various embodiments of the track comprising a layer of transversal stiffening cables in accordance with various embodiments of the invention;

FIGS. 33A and 33B show idler wheel path projections on a ground-engaging outer side of the track in accordance with an embodiment of the invention;

FIGS. 34A and 34B show idler wheel path projections on a ground-engaging outer side of the track in accordance with another embodiment of the invention;

FIG. 35 shows longitudinally uneven idler wheel paths on an inner side of the track in accordance with an embodiment of the invention;

FIGS. 36 and 37 show different lengths of transversal stiffening rods of the track in accordance with various embodiments of the invention;

FIGS. 38 and 39 show longitudinal rigidifiers on an inner surface of a carcass of the track in accordance with an embodiment of the invention;

FIGS. 40 and 41 show different configurations of a suspension unit of the track system in accordance with various embodiments of the invention;

FIGS. 42 and 43 show different examples of implementation of a track tensioner of the track system in accordance with various embodiments of the invention;

FIG. 44 shows an example of implementation in which the track is at least mainly made of fiber-reinforced elastomeric material in accordance with an embodiment of the invention;

FIGS. 45A and 45B show an example of an all-terrain vehicle (ATV) comprising track systems in accordance with an embodiment of the invention; and

FIGS. 46A and 46B show the ATV equipped with ground-engaging wheels instead of the track systems.

It is to be expressly understood that the description and drawings are only for the purpose of illustrating certain embodiments of the invention and are an aid for understanding. They are not intended to be a definition of the limits of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

FIG. 1 shows an example of a snowmobile 10 in accordance with an embodiment of the invention. The snowmobile 10 is designed for travelling on snow and in some cases ice. In this embodiment, the snowmobile 10 comprises a frame 11, a powertrain 12, a track system 14, a ski assembly 17, a seat 18, and a user interface 20, which enables a user to control the snowmobile 10.
The powertrain 12 is configured for generating motive power and transmitting motive power to the track system 14 to propel the snowmobile 10 on the ground. To that end, the powertrain 12 comprises a prime mover 15, which is a source of motive power that comprises one or more motors (e.g., an internal combustion engine, an electric motor, etc.). For example, in this embodiment, the prime mover 15 comprises an internal combustion engine. In other embodiments, the prime mover 15 may comprise another type of motor (e.g., an electric motor) or a combination of different types of motor (e.g., an internal combustion engine and an electric motor). The prime mover 15 is in a driving relationship with the track system 14 That is, the powertrain 12 transmits motive power from the primer mover 15 to the track system 14 in order to drive (i.e., impart motion to) the track system 14.
The ski assembly 17 is turnable to allow steering of the snowmobile 10. In this embodiment, the ski assembly 17 comprises a pair of skis 191, 192 connected to the frame 11 via a front suspension unit.
The seat 18 accommodates the user of the snowmobile 10. In this case, the seat 18 is a straddle seat and the snowmobile 10 is usable by a single person such that the seat 18 accommodates only that person driving the snowmobile 10. In other cases, the seat 18 may be another type of seat, and/or the snowmobile 10 may be usable by two individuals, namely one person driving the snowmobile 10 and a passenger, such that the seat 18 may accommodate both of these individuals (e.g., behind one another) or the snowmobile 10 may comprise an additional seat for the passenger.
The user interface 20 allows the user to interact with the snowmobile 10 to control the snowmobile 10. More particularly, the user interface 20 comprises an accelerator, a brake control, and a steering device that are operated by the user to control motion of the snowmobile 10 on the ground. In this case, the steering device comprises handlebars, although it may comprise a steering wheel or other type of steering element in other cases. The user interface 20 also comprises an instrument panel (e.g., a dashboard) which provides indicators (e.g., a speedometer indicator, a tachometer indicator, etc.) to convey information to the user.
The track system 14 engages the ground to generate traction of the snowmobile 10. In this embodiment, the track system 14 comprises a track-engaging assembly 24 and a track 21 disposed around the track-engaging assembly 24. More particularly, in this embodiment, with additional reference to FIG. 2, the track-engaging assembly 24 comprises a plurality of wheels, including a plurality of drive wheels 22 ₁, 22 ₂and a plurality of idler wheels, which includes rear idler wheels 26 ₁-26 ₄, lower roller wheels 28 ₁-28 ₆, and upper roller wheels 30 ₁, 30 ₂. The track-engaging assembly 24 also comprises a plurality of slide rails 33 ₁, 33 ₂. Various components of the track-engaging assembly 24, including the idler wheels 26 ₁-26 ₄, 28 ₁-28 ₆, 30 ₁, 30 ₂and the slide rails 33 ₁, 33 ₂are supported by a suspension unit 16. The track system 14 has a longitudinal direction and a first longitudinal end and a second longitudinal end that define a length of the track system 14. The track system 14 has a widthwise direction and a width that is defined by a width of the track 21. The track system 14 has a height direction that is normal to its longitudinal direction and its widthwise direction.
The track 21 engages the ground to provide traction to the snowmobile 10. A length of the track 21 allows the track 21 to be mounted around the track-engaging assembly 24. In view of its closed configuration without ends that allows it to be disposed and moved around the track-engaging assembly 24, the track 21 can be referred to as an “endless” track. With additional reference to FIGS. 3 to 7A, the endless track 21 comprises an inner side 25 and a ground-engaging outer side 27. The inner side 25 faces the wheels 22 ₁, 22 ₂, 26 ₁-26 ₄, 28 ₁-28 ₆, 30 ₁, 30 ₂and the slide rails 33 ₁, 33 ₂. The ground-engaging outer side 27 engages the ground. A top run 65 of the endless track 21 extends between the longitudinal ends of the track system 14 and over the wheels 22 ₁, 22 ₂, 26 ₁-26 ₄, 28 ₁-28 ₆, 30 ₁, 30 ₂, and a bottom run 66 of the endless track 21 extends between the longitudinal ends of the track system 14 and under the wheels 22 ₁, 22 ₂, 26 ₁-26 ₄, 28 ₁-28 ₆, 30 ₁, 30 ₂and the slide rails 33 ₁, 33 ₂. The endless track 21 has a longitudinal axis which defines a longitudinal direction of the track 21 (i.e., a direction generally parallel to its longitudinal axis) and transversal directions of the track (i.e., directions transverse to its longitudinal axis), including a widthwise direction of the track (i.e., a lateral direction generally perpendicular to its longitudinal axis). The endless track 21 has a thickness direction normal to its longitudinal and widthwise directions.
The track 21 is elastomeric, i.e., comprises elastomeric material, to be flexible around the track-engaging assembly 24. The elastomeric material of the track 21 can include any polymeric material with suitable elasticity. In this embodiment, the elastomeric material of the track 21 includes rubber. Various rubber compounds may be used and, in some cases, different rubber compounds may be present in different areas of the track 21. In other embodiments, the elastomeric material of the track 21 may include another elastomer in addition to or instead of rubber (e.g., polyurethane elastomer).
More particularly, the track 21 comprises an endless body 35 underlying its inner side 25 and ground-engaging outer side 27. In view of its underlying nature, the body 36 will be referred to as a “carcass”. The carcass 35 is elastomeric in that it comprises elastomeric material 38 which allows the carcass 35 to elastically change in shape and thus the endless track 21 to flex as it is in motion around the track-engaging assembly 24. The elastomeric material 38 can be any polymeric material with suitable elasticity. In this embodiment, the elastomeric material 38 includes rubber. Various rubber compounds may be used and, in some cases, different rubber compounds may be present in different areas of the carcass 35. In other embodiments, the elastomeric material 38 may include another elastomer in addition to or instead of rubber (e.g., polyurethane elastomer).
In this embodiment, the carcass 35 comprises a plurality of reinforcements embedded in its elastomeric material 38. These reinforcements can take on various forms.
For example, in this embodiment, the carcass 35 comprises a plurality of transversal stiffening rods 36 ₁-36 _Nthat extend transversally to the longitudinal direction of the endless track 21 to provide transversal rigidity to the track 21. More particularly, in this embodiment, the transversal stiffening rods 36 ₁-36 _Nextend in the widthwise direction of the track 21. Each of the transversal stiffening rods 36 ₁-36 _Nmay have various shapes and be made of any suitably rigid material (e.g., metal, polymer or composite material).
As another example, in this embodiment, the carcass 35 comprises a plurality of reinforcing cables 37 ₁-37 _Mthat are adjacent to one another and extend generally in the longitudinal direction of the endless track 21 to enhance strength in tension of the track 21 along its longitudinal direction. In this case, each of the reinforcing cables 37 ₁-37 _Mis a cord including a plurality of strands (e.g., textile fibers or metallic wires). In other cases, each of the reinforcing cables 37 ₁-37 _Mmay be another type of cable and may be made of any material suitably flexible longitudinally (e.g., fibers or wires of metal, plastic or composite material).
As yet another example, in this embodiment, the carcass 35 comprises a layer of reinforcing fabric 43. The reinforcing fabric 43 comprises thin pliable material made usually by weaving, felting, knitting, interlacing, or otherwise crossing natural or synthetic elongated fabric elements, such as fibers, filaments, strands and/or others, such that some elongated fabric elements extend transversally to the longitudinal direction of the track 21 to have a reinforcing effect in a transversal direction of the track 21. For instance, the reinforcing fabric 43 may comprise a ply of reinforcing woven fibers (e.g., nylon fibers or other synthetic fibers). For example, the reinforcing fabric 43 may protect the transversal stiffening rods 36 ₁-36 _N, improve cohesion of the track 21, and counter its elongation.
The carcass 35 may be molded into shape in a molding process during which the rubber 38 is cured. For example, in this embodiment, a mold may be used to consolidate layers of rubber providing the rubber 38 of the carcass 35, the reinforcing cables 37 ₁-37 _Mand the layer of reinforcing fabric 43.
In this embodiment, the endless track 21 is a one-piece “jointless” track such that the carcass 35 is a one-piece jointless carcass. In other embodiments, the endless track 21 may be a “jointed” track (i.e., having at least one joint connecting adjacent parts of the track 21) such that the carcass 35 is a jointed carcass (i.e., which has adjacent parts connected by the at least one joint). For example, in some embodiments, the endless track 21 may comprise a plurality of track sections interconnected to one another at a plurality of joints, in which case each of these track sections includes a respective part of the carcass 35. In other embodiments, the endless track 21 may be a one-piece track that can be closed like a belt with connectors at both of its longitudinal ends to form a joint.
The ground-engaging outer side 27 of the track 21 comprises a ground-engaging outer surface 31 of the carcass 35 and a plurality of traction projections 58 ₁-58 _Tthat project outwardly from the ground-engaging outer surface 31 to enhance traction on the ground. The traction projections 58 ₁-58 _T, which can be referred to as “traction lugs” or “traction profiles”, may have any suitable shape (e.g., curved shapes, shapes with straight parts and curved parts, etc.).
In this embodiment, each of the traction projection 58 ₁-58 _Tis an elastomeric traction projection in that it comprises elastomeric material 41. The elastomeric material 41 can be any polymeric material with suitable elasticity. More particularly, in this embodiment, the elastomeric material 41 includes rubber. Various rubber compounds may be used and, in some cases, different rubber compounds may be present in different areas of each of the traction projections 58 ₁-58 _T. In other embodiments, the elastomeric material 41 may include another elastomer in addition to or instead of rubber (e.g., polyurethane elastomer).
The traction projections 58 ₁-58 _Tmay be provided on the ground-engaging outer side 27 in various ways. For example, in this embodiment, the traction projections 58 ₁-58 _Tare provided on the ground-engaging outer side 27 by being molded with the carcass 35.
The inner side 25 of the track 21 comprises an inner surface 32 of the carcass 35 and a plurality of inner projections 34 ₁-34 _Dthat project inwardly from the inner surface 32 and are positioned to contact at least some of the wheels 22 ₁, 22 ₂, 26 ₁-26 ₄, 28 ₁-28 ₆, 30 ₁, 30 ₂and/or some of the slide rails 33 ₁, 33 ₂to do at least one of driving (i.e., imparting motion to) the track 21 and guiding the track 21. Since each of them is used to do at least one of driving the track 21 and guiding the track 21, the inner projections 34 ₁-34 _Dcan be referred to as “drive/guide projections” or “drive/guide lugs”. In some cases, a drive/guide lug 34 _imay interact with a given one of the drive wheels 22 ₁, 22 ₂to drive the track 21, in which case the drive/guide lug 34 _iis a drive lug. In other cases, a drive/guide lug 34 _imay interact with a given one of the idler wheels 26 ₁-26 ₄, 28 ₁-28 ₂, 30 ₁, 30 ₂and/or a given one of the slide rails 33 ₁, 33 ₂to guide the track 21 to maintain proper track alignment and prevent de-tracking without being used to drive the track 21, in which case the drive/guide lug 34 _iis a guide lug. In yet other cases, a drive/guide lug 34 _imay both (i) interact with a given one of the drive wheels 22 ₁, 22 ₃to drive the track 21 and (ii) interact with a given one of the idler wheels 26 ₁-26 ₄, 28 ₁-28 ₆, 30 ₁, 30 ₂and/or a given one of the slide rails 33 ₁, 33 ₂to guide the track 21, in which case the drive/guide lug 34 _iis both a drive lug and a guide lug.
In this embodiment, each of the drive/guide lugs 34 ₁-34 _Dis an elastomeric drive/guide lug in that it comprises elastomeric material 42. The elastomeric material 42 can be any polymeric material with suitable elasticity. More particularly, in this embodiment, the elastomeric material 42 includes rubber. Various rubber compounds may be used and, in some cases, different rubber compounds may be present in different areas of each of the drive/guide lugs 34 ₁-34 _D. In other embodiments, the elastomeric material 42 may include another elastomer in addition to or instead of rubber (e.g., polyurethane elastomer).
The drive/guide lugs 34 ₁-34 _Dmay be provided on the inner side 25 in various ways. For example, in this embodiment, the drive/guide lugs 34 ₁-34 _Dare provided on the inner side 25 by being molded with the carcass 35.
The carcass 35 has a thickness T_cwhich is relatively small. The thickness T_cof the carcass 35 is measured from the inner surface 32 to the ground-engaging outer surface 31 of the carcass 35 between longitudinally-adjacent ones of the traction projections 58 ₁-58 _T. For example, in some embodiments, the thickness T_cof the carcass 35 may be no more than 0.25 inches, in some cases no more than 0.24 inches, in some cases no more than 0.23 inches, in some cases no more than 0.22 inches, in some cases no more than 0.21 inches, in some cases no more than 0.20 inches, and in some cases even less (e.g., 0.18 or 0.17 inches). The thickness T_cof the carcass 35 may have any other suitable value in other embodiments.
The endless track 21 may be constructed and/or manufactured in various other ways in other embodiments.
For example, FIG. 7B shows an embodiment in which the track 21 is free of reinforcing fabric between the inner surface 32 and the ground-engaging outer surface 31 of the carcass 35 along at least part of the length of the track 21. That is, there is no layer of reinforcing fabric in the carcass 35 along at least part of the length of the track 21. In this embodiment, the track 21 is free of reinforcing fabric between the inner surface 32 and the ground-engaging outer surface 31 along at least a majority of the length of the track 21. More particularly, in this example of implementation, the track 21 is free of reinforcing fabric between the inner surface 32 and the ground-engaging outer surface 31 along an entirety of the length of the track 21. There is thus no layer of reinforcing fabric in the carcass 35 of the track 21 in this example of implementation. Specifically, in this case, the track 21 is free of reinforcing fabric, i.e., there is no layer of reinforcing fabric in the track 21.
This lack of reinforcing fabric layer may reduce a weight of the track 21. The lack of reinforcing fabric layer may also reduce a power consumption to drive the track 21. That is, when operated at a given speed, the track 21 may consume less power than if it had a reinforcing fabric layer (e.g., the layer of reinforcing fabric 43) embedded in the carcass 35 and extending along at least a majority (e.g., an entirety) of the length of the track 21 but was otherwise identical. For instance, in some examples of implementation, the track 21 may consume less power when operated at a speed above 40 miles per hour, in some cases above 60 miles per hour, and in some cases above 80 miles per hour.
More particularly, in this embodiment, the carcass 35 comprises the reinforcing cables 37 ₁-37 _Mand the transversal stiffening rods 36 ₁-36 _Nembedded in its rubber 38 but is free of any reinforcing fabric layer (i.e., the layer of reinforcing fabric 43 discussed above is omitted). In this case, the reinforcing cables 37 ₁-37 _Mare located between the transversal stiffening rods 36 ₁-36 _Nand the inner surface 32 of the carcass 35 in the thickness direction of the track 21. In other cases, as shown in FIG. 7C, the reinforcing cables 37 ₁-37 _Mmay be located between the transversal stiffening rods 36 ₁-36 _Nand the outer surface 31 of the carcass 35 in the thickness direction of the track 21. In such cases, the reinforcing cables 37 ₁-37 _Mmay act to protect the transversal stiffening rods 36 ₁-36 _N.
The track 21 free of any reinforcing fabric layer may be configured in various other ways in other embodiments. For example, in some embodiments, the track 21 may also be free of transversal stiffening rods, as shown in FIG. 7D.
In other embodiments, the track 21 may be free of reinforcing fabric between the inner surface 32 and the ground-engaging outer surface 31 of the carcass 35 along part of the length of the track 21 but still include some reinforcing fabric (e.g., between the inner surface 32 and the ground-engaging surface 31 along one or more segments of the length of the track 21, or within one or more of the drive/guide lugs 34 ₁-34 _Dand/or one or more of the traction projections 58 ₁-58 _T).
Elastomeric material of a given portion of the endless track 21, including the elastomeric material 38 of the carcass 35, the elastomeric material 41 of one of the traction projection 58 ₁-58 _T, and the elastomeric material 42 of one of the drive/guide lugs 34 ₁-34 _D, has various material properties, including a hardness (e.g., durometers in a Shore A hardness scale) and a modulus of elasticity, which can have any suitable value.
If the elastomeric material of the given portion of the track 21 is constituted of a single elastomer, the hardness of the elastomeric material of the given portion of the track 21 is the hardness of this single elastomer. Alternatively, if the elastomeric material of the given portion of the track 21 is constituted of two or more different elastomers, the hardness of the elastomeric material of the given portion of the track 21 is taken as an average hardness, which is obtained by multiplying a proportion of each elastomer in the elastomeric material of the given portion of the track 21 by that elastomer's hardness and then summing the results. That is, if the elastomeric material of the given portion of the track 21 is constituted of N elastomers, the average hardness is
$A_{avg} = \sum_{i = 1}^{N} P_{i} A_{i}$
where A_iis the hardness of elastomer “i” and P_iis the proportion (%) of elastomer “i” in the elastomeric material of the given portion of the track 21. In situations where this calculated value is not an integer and the hardness scale is only in integers, this calculated value rounded to the nearest integer gives the average hardness. An elastomer's hardness can be obtained from a standard ASTM D-2240 test (or equivalent test).
Similarly, if the elastomeric material of the given portion of the track 21 is constituted of a single elastomer, the modulus of elasticity of the elastomeric material of the given portion of the track 21 is the modulus of elasticity of this single elastomer. Alternatively, if the elastomeric material of the given portion of the track 21 is constituted of two or more different elastomers, the modulus of elasticity of the elastomeric material of the given portion of the track 21 is taken as an average modulus of elasticity, which is obtained by multiplying a proportion (%) of each elastomer in the elastomeric material of the given portion of the track 21 by that elastomer's modulus of elasticity and then summing the results. That is, if the elastomeric material of the given portion of the track 21 is constituted of N elastomers, the average modulus of elasticity is
$λ_{avg} = \sum_{i = 1}^{N} P_{i} λ_{i}$
where λ_iis the modulus of elasticity of elastomer “i” and P_iis the proportion (%) of elastomer “i” in the elastomeric material of the given portion of the track 21. For instance, in an embodiment in which the elastomeric material of the given portion of the track 21 is constituted of two types of rubbers, say rubber “A” having a modulus of elasticity of 1.9 MPa and being present in a proportion of 15% and rubber “B” having a modulus of elasticity of 6.3 MPa and being present in a proportion of 85%, the average modulus of elasticity of the elastomeric material of the given portion of the track 21 is 5.64 MPa. An elastomer's modulus of elasticity can be obtained from a standard ASTM D-412-A test (or equivalent test) based on a measurement at 100% elongation of the elastomer.
Each of the drive wheels 22 ₁, 22 ₂is rotatable on an axle of the snowmobile 10 for driving the endless track 21. That is, power generated by the prime mover 15 and delivered over the powertrain 12 of the snowmobile 10 rotates the axle, which rotates the drive wheels 22 ₁, 22 ₂, which impart motion of the track 21. In this embodiment, each drive wheel 22 _icomprises a drive sprocket engaging some of the drive/guide lugs 34 ₁-34 _Dof the inner side 25 of the track 21 in order to drive the track 21. In other embodiments, the drive wheel 22 _imay be configured in various other ways. For example, in embodiments where the track 21 comprises drive holes, the drive wheel 22 _imay have teeth that enter these holes in order to drive the track 21. As yet another example, in some embodiments, the drive wheel 22 _imay frictionally engage the inner side 25 of the track 21 in order to frictionally drive the track 21. The drive wheels 22 ₁, 22 ₂may be arranged in other configurations and/or the track system 14 may comprise more or less drive wheels (e.g., a single drive wheel, more than two drive wheels, etc.) in other embodiments.
The idler wheels 26 ₁-26 ₄, 28 ₁-28 ₆, 30 ₁, 30 ₂are not driven by power supplied by the prime mover 15, but are rather used to do at least one of guiding the track 21 as it is driven by the drive wheels 22 ₁, 22 ₂, tensioning the track 21, and supporting part of the weight of the snowmobile 10 on the ground via the track 21. More particularly, in this embodiment, the rear idler wheels 26 ₁-26 ₄are trailing idler wheels that maintain the track 21 in tension, guide the track 21 as it wraps around them, and can help to support part of the weight of the snowmobile 10 on the ground via the track 21. The lower roller wheels 28 ₁-28 ₆roll on the inner side 25 of the track 21 along the bottom run 66 of the track 21 to apply the bottom run 66 on the ground. The upper roller wheels 30 ₁, 30 ₂roll on the inner side 25 of the track 21 along the top run 65 of the track 21 to support and guide the top run 65 as the track 21 moves. The idler wheels 26 ₁-26 ₄, 28 ₁-28 ₆, 30 ₁, 30 ₂may be arranged in other configurations and/or the track assembly 14 may comprise more or less idler wheels in other embodiments.
The idler wheels 26 ₁-26 ₄, 28 ₁-28 ₆, 30 ₁, 30 ₂move on respective ones of a plurality of idler wheel paths 50 ₁-50 ₄of the inner surface 32 of the carcass 35 of the endless track 21. Each of the idler wheel paths 50 ₁-50 ₄extends adjacent to respective ones of the drive/guide lugs 34 ₁-34 _Dto allow these lugs to guide motion of the track 21 around the track-engaging assembly 24. As the roller wheels 28 ₁-28 ₆, 30 ₁, 30 ₂roll on respective ones of the idler wheel paths 50 ₁-50 ₄, these paths can be referred to as “rolling paths”.
The slide rails 33 ₁, 33 ₂slide on the inner side 25 of the endless track 21 along the bottom run 66 of the track 21 to apply the bottom run 66 onto the ground. In this embodiment, the slide rails 33 ₁, 33 ₂are curved upwardly in a front region of the track system 14 to guide the track 21 towards the drive wheels 22 ₁, 22 ₂. In some cases, as shown in FIG. 8, the endless track 21 may comprise slide members 39 ₁-39 _Sthat slide against the slide rails 33 ₁, 33 ₂to reduce friction. The slide members 39 ₁-39 _S, which can sometimes be referred to as “clips”, may be mounted via holes 40 ₁-40 _Harranged in two rows extending longitudinally and spaced apart laterally of the track 21. In other cases, as shown in FIG. 9, the endless track 21 may be free of such slide members. The slide rails 33 ₁, 33 ₂may be arranged in other configurations and/or the track assembly 14 may comprise more or less slide rails in other embodiments.
Various considerations may be important when it comes to use and performance of the snowmobile 10.
For example, in use, the snowmobile 10 generates noise, including noise generated by the track system 14. Various factors may contribute to the noise generated by the track system 14. For example, in some cases: impacts between the idler wheels 26 ₁-26 ₄, 28 ₁-28 ₆, 30 ₁, 30 ₂and the transversal stiffening rods 36 ₁-36 _Nof the endless track 21; impacts between the slide rails 33 ₁, 33 ₂and the transversal stiffening rods 36 ₁-36 _Nof the track 21; impacts between the slide rails 33 ₁, 33 ₂and the clips 39 ₁-39 _Sof the track 21, if any; impacts between the traction projections 58 ₁-58 _Tof the track 21 and the ground; and contact between the track 21 and the drive wheels 22 ₁, 22 ₂may be contributors to the noise generated by the track system 14.
As another example, traction and floatation provided by the track system 14 depend on rigidity of the endless track 21. While longitudinal flexibility of the track 21 is desirable in order to efficiently drive the track around the track-engaging assembly 24, transversal rigidity of the track 21 is desirable in order to have a proper ground-contacting area for traction and floatation.
The snowmobile 10, including the track system 14, may therefore be configured to have a reduced noise profile so as to generate less noise, enhanced track rigidity characteristics to improve its traction and floatation, and/or other features improving use and performance of the snowmobile 10. This may be achieved in various ways in various embodiments, examples of which will now be discussed.

1. Shape of Transversal Stiffening Rod

In some embodiments, the transversal stiffening rods 36 ₁-36 _Nof the endless track 21 may be shaped in order to reduce noise generation and/or for other purposes (e.g., weight reduction, controlled transversal rigidity, etc.). Various shapes of the transversal stiffening rods 36 ₁-36 _Ncan be implemented in various embodiments, examples of which are discussed below.

1.1 Transversal Stiffening Rods Shaped to Increase Thickness of Elastomeric Material

In some embodiments, the transversal stiffening rods 36 ₁-36 _Nmay be shaped so as to increase a thickness of elastomeric material of the endless track 21 at locations of the rods 36 ₁-36 _N. That is, the transversal stiffening rods 36 ₁-36 _Nmay be shaped such that a thickness of elastomeric material where they are located is greater than that which would exist if they were replaced with conventional transversal stiffening rods having a generally semicircular or half-moon-shaped cross-section, such as those shown in FIG. 6, but the track 21 was otherwise identical and had the same transversal rigidity. The greater thickness of elastomeric material can provide enhanced shock absorption, and therefore reduce noise generation, when the idler wheels 26 ₁-26 ₄, 28 ₁-28 ₆, 30 ₁, 30 ₂and the slide rails 33 ₁, 33 ₂cross the transversal stiffening rods 36 ₁-36 _N. Also, in some cases, the transversal stiffening rods 36 ₁-36 _Nmay have a smaller cross-section than conventional rods and this may make them less rigid and thus less noisy when crossed by the idler wheels 26 ₁-26 ₄, 28 ₁-28 ₆, 30 ₁, 30 ₂and the slide rails 33 ₁, 33 ₂.
Various shapes of the transversal stiffening rods 36 ₁-36 _Ncan be implemented to increase the thickness of elastomeric material in various embodiments, examples of which are discussed below.
1.1.1 Rod Cross-Section being Elongate (i.e., Having a High Aspect Ratio)
In some embodiments, as shown in FIGS. 10 and 11, a transversal stiffening rod 36 _xmay have a cross-section which is elongate, i.e., has a high aspect ratio C_L/C_S. The cross-section of the transversal stiffening rod 36 _xis taken perpendicularly to a longitudinal axis 86 of the rod 36 _xand is elongate since a longest dimension C_Lof the cross-section is significantly greater than a smallest dimension C_Sof the cross-section. In this example, the longest dimension C_Lof the cross-section of the transversal stiffening rod 36 _xis in the longitudinal direction of the endless track 21 and the smallest dimension C_Sof the cross-section of the transversal stiffening rod 36 _xis in the thickness direction of the endless track 21. The cross-section of the transversal stiffening rod 36 _xis thus elongated in the longitudinal direction of the track 21.
The aspect ratio C_L/C_Sof the cross-section of the transversal stiffening rod 36 _x, which is a ratio of the longest dimension C_Lof the cross-section to the smallest dimension C_Sof the cross-section, can have any suitable value in various embodiments. For example, in some embodiments, the aspect ratio C_L/C_Smay be at least 4, in some cases at least 5, in some cases at least 6, in some cases at least 7, in some cases at least 8, in some cases at least 10, and in some cases even more (e.g., 12, 15 or more).
In this embodiment, the cross-section of the transversal stiffening rod 36 _xis substantially flat. That is, the cross-section of the rod 36 _xhas major surfaces generally parallel to one another and distinctly larger than its minor surfaces.
More particularly, in this embodiment, the cross-section of the transversal stiffening rod 36 _xis oblong. More specifically, in this embodiment, the cross-section of the transversal stiffening rod 36 _xhas a generally oblong rectangular shape. A width W_Rof the cross-section of the transversal stiffening rod 36 _xis in the longitudinal direction of the endless track 21, and corresponds to the longest dimension C_Lof the cross-section. A thickness T_Rof the cross-section of the transversal stiffening rod 36 _xis in the thickness direction of the endless track 21, and corresponds to the smallest dimension C_Sof the cross-section. In this example, the aspect ratio W_R/T_Ris about 8. In view of the generally oblong rectangular shape and thinness of its cross-section, in this example, the transversal stiffening rod 36 _xis plate-like and similar to a ruler and can be referred to as a “plate-like” or “ruler” rod.
Also, in this embodiment, the cross-section of the transversal stiffening rod 36 _xis constant (i.e., does not substantially change) along at least a majority of a length of the rod 36 _x. More particularly, in this example, the cross-section of the transversal stiffening rod 36 _xis constant along an entirety of the length of the rod 36 _x. In other embodiments, the cross-section of the transversal stiffening rod 36 _xmay vary along the longitudinal axis 86 of the rod 36 _xsuch that it is different (e.g., larger, smaller, and/or differently shaped) at respective locations along the longitudinal axis 86 of the rod 36 _x.
The cross-section of each of the transversal stiffening rods 36 ₁-36 _Nmay have various other shapes such that it is elongate, i.e., its aspect ratio C_L/C_Sis high, in other embodiments. For example, in other embodiments, the cross-section of a transversal stiffening rod 36 _xmay be oblong but not rectangular (e.g., it may be oblong with bent, curved or pointy lateral edges).

1.1.2 Thin Rod

In some embodiments, as shown in FIGS. 12 and 13, a transversal stiffening rod 36 _xmay be “thin”, i.e., the thickness T_Rof the cross-section of the transversal stiffening rod 36 _xin the thickness direction of the endless track 21 may be small. In some cases, this can happen with the cross-section of the transversal stiffening rod 36 _xbeing elongate, i.e., having a high aspect ratio C_L/C_S, as discussed above in section 1.1.1. In other cases, this can happen without the cross-section of the transversal stiffening rod 36 _xbeing elongate, i.e., having a high aspect ratio C_L/C_S.
The thickness T_Rcan have any suitable value. For example, in some embodiments, the thickness T_Rmay be less than 3.5 mm, in some cases no more than 3 mm, in some cases no more than 2.5 mm, in some cases no more than 2 mm, and in some cases even less (e.g., 1.5 mm or less).
The thickness T_Rof the cross-section of the transversal stiffening rod 36 _xcan also be expressed relative to the thickness T_Cof the carcass 35. For example, in some embodiments, a ratio T_R/T_Cof the thickness T_Rof the cross-section of the transversal stiffening rod 36 _xto the thickness T_Cof the carcass 35 may be less than 0.7, in some cases no more than 0.6, in some cases no more than 0.5, in some cases no more than 0.4, and in some cases even less (e.g., 0.2 or less).
In this embodiment, the cross-section of the transversal stiffening rod 36 _xis generally semicircular or half-moon-shaped. The thickness T_Rthus generally corresponds to a radius of the cross-section of the transversal stiffening rod 36 _x. Hence, in this embodiment, the transversal stiffening rod 36 _xis thin but its cross-section does not have a high aspect ratio C_L/C_Sas discussed above in section 1.1.1.
The cross-section of each of the transversal stiffening rods 36 ₁-36 _Nmay have various other shapes such that its thickness T_Ris small in other embodiments.
For example, in other embodiments, the cross-section of a transversal stiffening rod 36 _xmay be generally circular, square, oblong rectangular, etc.

1.1.3 Rod Defining an Internal Space

In some embodiments, as shown in FIGS. 14 and 15, a transversal stiffening rod 36 _xmay form a cavity (i.e., an internal space) 44 which, in this example, receives elastomeric material 46. In this embodiment, the cavity 44 is open toward the inner side 25 of the endless track 21 in order to increase a thickness of elastomeric material between the transversal stiffening rod 36 _xand the inner side 25 of the track 21. The elastomeric material 46, which is a portion of the elastomeric material 38 of the carcass 35, is thus located between the transversal stiffening rod 36 _xand the inner surface 32 of the carcass 35.
More particularly, in this embodiment, the transversal stiffening rod 36 _xforms the cavity 44 by having a cross-section that is curved. In this example, the cross-section of the transversal stiffening rod 36 _xis generally arc-shaped. In addition to the increase in the thickness of elastomeric material, this shape may make the transversal stiffening rod 36 _xmore rigid (e.g., compared to a plate-like rod as discussed above in section 1.1.1).
The cross-section of the transversal stiffening rod 36 _xmay have various other shapes which define the cavity 44 in other embodiments. For instance, in some embodiments, the cross-section of the transversal stiffening rod 36 _xmay have other curvatures, may have straight segments, or may have a combination of straight segments and curved segments to define the cavity 44.
FIGS. 16 and 17 show another embodiment in which the cavity 44 is closed around the cross-section of the transversal stiffening rod 36 _x. Basically, the transversal stiffening rod 36 _xis hollow and has the elastomeric material 46 in its hollow interior. In this embodiment, the cross-section of the transversal stiffening rod 36 _xhas a generally semicircular outer wall and the cavity 44 is also generally semicircular. The cross-section of the transversal stiffening rod 36 _xand the cavity 44 may have various other shapes in other embodiments.
The transversal stiffening rod 36 _xwith the cavity 44 may be made using various processes. For example, in some embodiments, the transversal stiffening rod 36 _xmay be extruded using an extrusion process or pultruded using a pultrusion process. The elastomeric material 46 may be provided in the cavity 46 by having some of the elastomeric material 38 of the carcass 35 migrate in the cavity 46 during molding of the track 21 (e.g., in cases where the cavity 44 is open as in FIGS. 14 and 15), or by placing a piece of elastomeric material in the cavity 44 of before molding of the track 21 (e.g., in cases where the cavity 44 is closed as in FIGS. 16 and 17).
As a variant to having elastomeric material 46 in the cavity 44 of a transversal stiffening rod 36 _x, in some embodiments, the cavity 44 may be empty or may contain material (e.g., a fluid) other than elastomeric material. In some cases, this may involve the cavity 44 being closed not only around the cross-section of the transversal stiffening rod 36 _xbut also at both longitudinal ends of the transversal stiffening rod 36 _x.

1.1.4 Rod Including a Recess at Idler Wheel Path

In some embodiments, as shown in FIG. 18, a transversal stiffening rod 36 _xmay comprise a plurality of recesses 51 ₁-51 ₄aligned with respective ones of the idler wheel paths 50 ₁-50 ₄. That is, the recesses 51 ₁-51 ₄are located in the widthwise direction of the endless track 21 where the idler wheel paths 50 ₁-50 ₄are located, i.e., each of these recesses overlaps a respective one of the idler wheel paths 50 ₁-50 ₄in the widthwise direction of the track 21. Each recess 51 _iis defined by an inner surface of the transversal stiffening rod 36 _xthat recedes towards the ground-engaging outer side 27 of the endless track 21. This results in the thickness of elastomeric material between the transversal stiffening rod 36 _xand the idler wheel path 50 _ibeing greater than the thickness of elastomeric material between the transversal stiffening rod 36 _xand a portion of the inner surface 32 of the carcass 35 outside of the idler wheel paths 50 ₁-50 ₄.
The recess 51 _ihas a depth D_rthat may have any suitable value in various embodiments. For example, in some embodiments, the depth D_rmay be at least 0.03 inches, in some cases at least 0.045 inches, in some cases at least 0.06 inches, and in some cases even more (e.g., up to 0.125 inches).
The depth D_rof the recess 51 _ican also be expressed relative to the thickness T_Rof the transversal stiffening rod 36 _x. For example, in some embodiments, a ratio D_r/T_Rof the depth D_rof the recess 51 _ito the thickness T_Rof the transversal stiffening rod 36 _xmay be at least 0.1, in some cases at least 0.15, in some cases at least 0.2, and in some cases even more (e.g., up to 0.8).
In this embodiment, the recess 51 _iis defined by a dimensional reduction of the cross-section of the transversal stiffening rod 36 _x. In cases where the transversal stiffening rod 36 _xis molded, the recess 51 ₁may be molded during molding of the transversal stiffening rod 36 _xor may be cut or otherwise formed after molding of the transversal stiffening rod 36 _x.
FIG. 19 shows another embodiment in which the recess 51 _iis defined by a deflection of the transversal stiffening rod 36 _x. More particularly, in this embodiment, the transversal stiffening rod 36 _xis curved towards the ground-engaging outer side 27 of the track 21 to define the recess 51 ₁. The transversal stiffening rod 36 _xmay be deflected in various other manners in other embodiments to define the recess 51 _i(e.g., have a V-shaped bent). In cases where the transversal stiffening rod 36 _xis molded, the deflection of the transversal stiffening rod 36 _xwhich defines the recess 51 _imay be created during molding of the transversal stiffening rod 36 _x.

1.1.5 Thickness of Elastomeric Material Between Rod Inner Surface and Carcass Inner Surface Varying Longitudinally

In some embodiments, as shown in FIGS. 20A and 21, a transversal stiffening rod 36 _xmay be shaped such that a thickness of elastomeric material T_IRbetween an inner surface 52 of the transversal stiffening rod 36 _x(i.e., a surface of the transversal stiffening rod 36 _xfacing the inner side 25 of the track 21) and the inner surface 32 of the carcass 35 varies in the longitudinal direction of the track 21.
In this case, the thickness of elastomeric material T_IRdecreases in the longitudinal direction of the track 21 along a direction of motion of the roller wheels 28 ₁-28 ₆, 30 ₁, 30 ₂when the snowmobile 10 travels forward. This may help to reduce an intensity of a shock when a given one of the roller wheels 28 ₁-28 ₆, 30 ₁, 30 ₂arrives at the transversal stiffening rod 36 _x. Basically, a transition of the roller wheel between a relatively soft region of the track 21 before the transversal stiffening rod 36 _xand a relatively hard region of the track at the transversal stiffening rod 36 _xis made progressively.
A variation ΔT_IRof the thickness of elastomeric material T_IRacross a dimension L_Rof the cross-section of the transversal stiffening rod 36 _xin the longitudinal direction of the track 21 may have any suitable value in various embodiments. The variation ΔT_IRcan be calculated ΔT_IR=(T_IR-max−T_IR-min)/T_IR-min×100%, where T_IR-maxand T_IR-minare respectively the maximum and minimum values of the thickness of elastomeric material T_IRacross the dimension L_Rof the cross-section of the transversal stiffening rod 36 _x. For example, in some embodiments, the variation ΔT_IRmay be at least 10%, in some cases at least 30%, in some cases at least 50%, and in some cases even more (e.g., up to 100%).
In this embodiment, the cross-section of the transversal stiffening rod 36 _xhas a wedge-like shape such that the thickness of elastomeric material T_IRprogressively decreases across its dimension L_R.
FIG. 20B shows another embodiment in which the inner surface 52 of a transversal stiffening rod 36 _xis uneven such that the thickness of elastomeric material T_IRbetween the inner surface 52 of the transversal stiffening rod 36 _xand the inner surface 32 of the carcass 35 varies in the longitudinal direction of the track 21. In this embodiment, the inner surface 52 of the transversal stiffening rod 36 _xis curved. More particularly, in this example, the cross-section of the transversal stiffening rod 36 _xis generally semicircular or half-moon-shaped with the inner surface 52 being arched.
The cross-section of the transversal stiffening rod 36 _xmay have various other shapes to create the variation ΔT_IRof the thickness of elastomeric material T_IRin other embodiments.

1.2 Short Rods

In some embodiments, as shown in FIG. 36, a transversal stiffening rod 36 _xmay be a “short” rod that does not extend across all the width of the endless track 21 such that it does not extend beneath laterally-outmost track-contacting devices of the track-engaging assembly 24, i.e., laterally-outmost ones of the idler wheels 26 ₁-26 ₄, 28 ₁-28 ₆, 30 ₁, 30 ₂(i.e., those idler wheels which are closest to lateral edges of the track 21) and/or the slide rails 33 ₁, 33 ₂. This may avoid impacts that would otherwise occur between the transversal stiffening rod 36 _xand these wheels and/or slide rails and may therefore reduce noise generation.
A ratio of the length of the transversal stiffening rod 36 _xto the width of the track 21 may have any suitable value. For example, in some embodiments, the ratio of the length of the transversal stiffening rod 36 _xto the width of the track 21 may be no more than 90%, in some cases no more than 85%, in some cases no more than 80%, and in some cases even less (e.g., no more than 50%).
In this embodiment, the transversal stiffening rod 36 _xextends beneath the slide rails 33 ₁, 33 ₂but does not extend beneath the idler wheels 26 ₁, 26 ₄, 28 ₁, 28 ₂, 28 ₄, 28 ₅which are laterally outmost (only the idler wheels 28 ₁, 28 ₄are shown here). In other embodiments, the transversal stiffening rod 36 _xmay be shorter. For instance, FIG. 37 shows an embodiment in which the transversal stiffening rod 36 _xdoes not extend beneath the slide rails 33 ₁, 33 ₂or the idler wheels 26 ₁, 26 ₄, 28 ₁, 28 ₂, 28 ₄, 28 ₅which are laterally outmost.

2. Distribution of Transversal Stiffening Rods

In some embodiments, a distribution of the transversal stiffening rods 36 ₁-36 _Nwithin the endless track 21 may help to reduce noise generation and/or provide other benefits (e.g., controlled transversal rigidity, etc.). Various distributions of the transversal stiffening rods 36 ₁-36 _Ncan be implemented in various embodiments, examples of which are discussed below.

2.1 Rods Stacked in Thickness Direction of Track

In some embodiments, as shown in FIG. 22A, two or more of the transversal stiffening rods 36 ₁-36 _Nmay be stacked in the thickness direction of the endless track 21 with deformable material 53 in between. That is, two or more of the transversal stiffening rods 36 ₁-36 _Nmay be spaced apart in the track's thickness direction with deformable material 53 in between them. This provides enhanced transversal rigidity but also, by virtue of the deformable material 53, shock absorption, which may help to reduce noise generation.
In this embodiment, a first transversal stiffening rod 36 _iand a second transversal stiffening rod 36 _jare spaced apart in the thickness direction of the track 21 and the deformable material 53 between them comprises elastomeric material. In this example of implementation, the elastomeric material 53 is rubber. The elastomeric material 53 may be another elastomer in other examples of implementation.
In some cases, the rubber 53 between the transversal stiffening rods 36 _i, 36 _jmay have the same elasticity and/or the same hardness as other elastomeric material of the endless track 21 (e.g., a portion of the elastomeric material 38 of the carcass 35 above the transversal stiffening rod 36 _jor a portion of the elastomeric material 41 of the traction projection 58 _ibelow the transversal stiffening rod 36 _i).
In other cases, the rubber 53 between the transversal stiffening rods 36 _i, 36 _jmay be more elastic, i.e., have a lower modulus of elasticity, and/or less hard, i.e., a lower hardness, than other elastomeric material of the endless track 21 (e.g., a portion of the elastomeric material 38 of the carcass 35 above the transversal stiffening rod 36 _jor a portion of the elastomeric material 41 of the traction projection 58 _ibelow the transversal stiffening rod 36 _i). This may help in terms of shock absorption. For example, in some embodiments, a ratio of the modulus of elasticity of the rubber 53 between the transversal stiffening rods 36 _i, 36 _jand the modulus of elasticity of a portion of the elastomeric material 38 of the carcass 35 above the transversal stiffening rod 36 _jor a portion of the elastomeric material 41 of the traction projection 58 _ibelow the transversal stiffening rod 36 _imay be no more than 0.9, in some cases no more than 0.8, in some cases no more than 0.7, and in some cases even less (e.g., no more than 0.5); and/or a ratio of the hardness of the rubber 53 between the transversal stiffening rods 36 _i, 36 _jand the hardness of a portion of the elastomeric material 38 of the carcass 35 above the transversal stiffening rod 36 _jor a portion of the elastomeric material 41 of the traction projection 58 _ibelow the transversal stiffening rod 36 _imay be no more than 0.9, in some cases no more than 0.8, in some cases no more than 0.7, and in some cases even less (e.g., no more than 0.5).
In other cases, the rubber 53 between the transversal stiffening rods 36 _i, 36 _jmay be more rigid, i.e., have a higher modulus of elasticity, and/or harder, i.e., a higher hardness, than other elastomeric material of the endless track 21 (e.g., a portion of the elastomeric material 38 of the carcass 35 above the transversal stiffening rod 36 _jor a portion of the elastomeric material 41 of the traction projection 58 _ibelow the transversal stiffening rod 36 _i). This may help in terms of transverse rigidity. For example, in some embodiments, a ratio of the modulus of elasticity of the rubber 53 between the transversal stiffening rods 36 _i, 36 _jand the modulus of elasticity of a portion of the elastomeric material 38 of the carcass 35 above the transversal stiffening rod 36 _jor a portion of the elastomeric material 41 of the traction projection 58 _ibelow the transversal stiffening rod 36 _imay be at least 1.1, in some cases at least 1.2, in some cases at least 1.3, and in some cases even more (e.g., at least 1.5); and/or a ratio of the hardness of the rubber 53 between the transversal stiffening rods 36 _i, 36 _jand the hardness of a portion of the elastomeric material 38 of the carcass 35 above the transversal stiffening rod 36 _jor a portion of the elastomeric material 41 of the traction projection 58 _ibelow the transversal stiffening rod 36 _imay be at least 1.1, in some cases at least 1.2, in some cases at least 1.3, and in some cases even more (e.g., at least 1.5).
A spacing S_RTof the transversal stiffening rods 36 _i, 36 _jin the thickness direction of the track 21 may have any suitable value. In this case, the spacing S_RTcorresponds to a thickness of the rubber 53. For example, in some embodiments, the spacing S_RTmay be at least 0.030 inches, in some cases at least 0.060 inches, in some cases at least 0.125 inches, and in some cases even more.
The spacing S_RTof the transversal stiffening rods 36 _i, 36 _jin the thickness direction of the track 21 can also be expressed relative to the thickness T_Cof the carcass 35. For example, in some embodiments, a ratio S_RT/T_Cof the spacing S_RTof the transversal stiffening rods 36 _i, 36 _jto the thickness T_Cof the carcass 35 may be at least 0.15, in some cases at least 0.30, in some cases at least 0.60, and in some cases even more.
The deformable material 53 can be positioned between the transversal stiffening rods 36 _i, 36 _jduring manufacturing of the endless track 21 in various ways. For example, in embodiments in which the endless track 21 is molded in a mold by placing different layers of material in the mold, the deformable material 53 may be positioned over the transversal stiffening rod 36 _iin the mold before placing the transversal stiffening rod 36 _jin the mold, or vice versa.
In this embodiment, each of the transversal stiffening rods 36 _i, 36 _jhas a cross-section with a high aspect ratio and a generally rectangular shape, i.e., it is a plate-like or “ruler” rod, as discussed above in section 1.1.1. The transversal stiffening rods 36 _i, 36 _jmay have any other suitable shapes in other embodiments. Also, in some embodiments, the transversal stiffening rods 36 _i, 36 _jmay have a common shape, while in other embodiments, they may have different shapes.
Although in this embodiment the deformable material 53 between the transversal stiffening rods 36 _i, 36 _jcomprises elastomeric material, in other embodiments, the deformable material 53 may comprise any other deformable substance. For example, in some embodiments, the deformable material 53 may comprise a gel, a fluid (e.g., a pouch or other container containing a liquid or gas), or another substance that can deform under load.
Also, in some embodiments, one or more of the reinforcing cables 37 ₁-37 _Mand/or a layer of reinforcing fabric 43 of the track 21 may extend between the transversal stiffening rods 36 _i, 36 _jstacked over one another. For example, FIG. 22B shows an embodiment in which a reinforcing cable 37 _iextends between the transversal stiffening rods 36 _i, 36 _j, while FIG. 22C shows an embodiment in which a layer of reinforcing fabric 43 extends between the transversal stiffening rods 36 _i, 36 _j.
While in this embodiment there are two transversal stiffening rods 36 _i, 36 _jstacked over one another, in other embodiments, there may be three or more of the transversal stiffening rods 36 ₁-36 _Nthat are stacked in the thickness direction of the track 21 with deformable material 53 between adjacent ones of these three or more transversal stiffening rods.

2.2 Rods Located Between Longitudinally-Adjacent Traction Projections

In some embodiments, as shown in FIG. 23A, in addition to given ones of the transversal stiffening rods 36 ₁-36 _Nbeing aligned with respective ones of the traction projections 58 ₁-58 _Tin the longitudinal direction of the track 21 (i.e., being located, in the longitudinal direction of the track 21, where respective ones of the traction projections 58 ₁-58 _Tare located such that a stiffening rod overlaps a traction projection in the longitudinal direction of the track 21), other ones of the transversal stiffening rods 36 ₁-36 _Nmay be located, in the longitudinal direction of the track 21, between adjacent ones of the traction projections 58 ₁-58 _T. This may provide enhanced transversal rigidity while not being detrimental in terms of noise generation. For example, in some cases, the idler wheels 28 ₁-28 ₆, 30 ₁, 30 ₂spending more time on relatively rigid parts of the track 21 as they move along respective ones of the rolling paths 50 ₁-50 ₄of the inner surface 32 of the carcass 35 may help to reduce noise generation. In other cases, the transversal stiffening rods 36 ₁-36 _Nmay be shaped such that noise generated is not greater than if there were rods only where the traction projections 58 ₁-58 _Tare located.
More particularly, in this embodiment, a transversal stiffening rod 36 _xis located longitudinally between a first traction projection 58 _iand a second traction projection 58 _jthat are adjacent to one another in the longitudinal direction of the track 21. The transversal stiffening rod 36 _xis also located longitudinally between a first transversal stiffening rod 36 _iand a second transversal stiffening rod 36 _jwhich are respectively located, in the longitudinal direction of the track 21, where the traction projections 58 _i, 58 _jare located. A distance P_Tbetween the traction projections 58 _i, 58 _jalong the longitudinal direction of the track 21 is referred to as a “pitch”. In view of its longitudinal position, the transversal stiffening rod 36 _xmay be referred to as an “inter-traction-projection” rod or an “interpitch” rod.
In this example, the transversal stiffening rod 36 _xis located midway between the traction projections 58 _i, 58 _j. In other examples, the transversal stiffening rod 36 _xmay be located closer to a given one of the traction projections 58 _i, 58 _jthan the other.
In this embodiment, each of the transversal stiffening rods 36 _x, 36 _i, 36 _jhas a cross-section with a high aspect ratio and a generally rectangular shape, i.e., it is a plate-like or “ruler” rod, as discussed above in section 1.1.1. The longitudinal extent of each of the transversal stiffening rods 36 _x, 36 _i, 36 _jresults in the roller wheels 28 ₁-28 ₆, 30 ₁, 30 ₂spending even more time on relatively rigid parts of the track 21 as they move along respective ones of the rolling paths 50 ₁-50 ₄of the inner surface 32 of the carcass 35. Also, the thinness of the transversal stiffening rod 36 _xallows it to be entirely embedded in the carcass 35 between the traction projections 58 _i, 58 _j.
Each of the transversal stiffening rods 36 _x, 36 _i, 36 _jmay have any other suitable shape in other embodiments. Also, different ones of the transversal stiffening rods 36 _x, 36 _i, 36 _jmay have different shapes in other embodiments. For example, in some embodiments, the transversal stiffening rods 36 _i, 36 _jmay have a common shape while the transversal stiffening rod 36 _xmay have a different shape. For instance, FIG. 23B shows an embodiment in which the transversal stiffening rods 36 _i, 36 _jare thicker and thus more rigid than the transversal stiffening rod 36 _xsince there is more rubber where they are located.
Although in this embodiment there is a single inter-traction-projection rod 36 _xbetween the adjacent traction projections 58 _i, 58 _j, in other embodiments, there may be two or more inter-traction-projection rods between the traction projections 58 _i, 58 _j. For instance, FIG. 24 shows an embodiment in which there are two inter-traction- projection rods 36 _x1, 36 _x2between the traction projections 58 _i, 58 _j.
2.3 Longitudinally-Adjacent Rods have at Least One Different Characteristic
In some embodiments, as shown in FIG. 25, longitudinally-adjacent ones of the transversal stiffening rods 36 ₁-36 _Nmay be different from one another, i.e., may have at least one characteristic, such as shape or material, that is different. This may help to reduce noise generation by creating a sound spectrum which is different from that which would result if all the transversal stiffening rods 36 ₁-36 _Nwere identical.
In this embodiment, a first transversal stiffening rod 36 _iand a second transversal stiffening rod 36 _jwhich are adjacent to one another in the longitudinal direction of the endless track 21 have different shapes. In this example, the transversal stiffening rod 36 _ihas a generally rectangular cross-section (as discussed above in section 1.1.1), while the transversal stiffening rod 36 _jhas a generally semicircular cross-section. The transversal stiffening rods 36 _i, 36 _jmay have any other suitable shapes that are different from one another in other examples (e.g., the transversal stiffening rods 36 _i, 36 _jand the transversal stiffening rod 36 _xdiscussed in connection with FIG. 23B).
Also, in this embodiment, the transversal stiffening rods 36 _i, 36 _jcomprise different materials. For example, in this case, the transversal stiffening rod 36 _imay be made of material which is more rigid than material from which is made the transversal stiffening rod 36 _j, given its smaller cross-sectional size.
While in this embodiment the transversal stiffening rods 36 _i, 36 _jdiffer both in shape and material, in other embodiments, the transversal stiffening rods 36 _i, 36 _jmay differ only in shape or only in material.
Also, although in this embodiment, only two adjacent transversal stiffening rods 36 _i, 36 _jhave been considered, in some embodiments, three or more of the stiffening rods 36 ₁-36 _Nwhich succeed one another in the longitudinal direction of the track 21 may be different from one another (e.g., have three or more different shapes and/or comprise three of more different materials).

3. Material of Transversal Stiffening Rod

In some embodiments, a transversal stiffening rod 36 _xmay be made of material which may help to reduce noise generation and/or provide other benefits (e.g., controlled transversal rigidity, etc.). For example, in some embodiments, the material of the transversal stiffening rod 36 _xmay be selected so as to provide transversal rigidity yet reduce the difference in thickness-wise hardness or rigidity between a region of the endless track 21 where the transversal stiffening rod 36 _xis located and adjacent regions of the endless track 21 where there are no transversal stiffening rods. This may help to reduce an intensity of a shock when a given one of the roller wheels 28 ₁-28 ₆, 30 ₁, 30 ₂arrives at the transversal stiffening rod 36 _x.

3.1 Reinforced Elastomeric Rod

In some embodiments, as shown in FIG. 26, a transversal stiffening rod 36 _xmay be an elastomeric fiber-reinforced rod which comprises an elongated elastomeric body 55 in which are embedded fibers 56 ₁-56 _F. The fibers 56 ₁-56 _Fgenerally extend transversally to the longitudinal direction of the track 21 to provide transversal rigidity to the transversal stiffening rod 36 _x.
The elongated elastomeric body 55 is elastomeric in that it comprises elastomeric material 57. The elastomeric material 57 can be any polymeric material with suitable elasticity. More particularly, in this embodiment, the elastomeric material 57 includes rubber. Various rubber compounds may be used and, in some cases, different rubber compounds may be present in different areas of each of the elongated elastomeric body 55. In other embodiments, the elastomeric material 57 may include another elastomer in addition to or instead of rubber (e.g., polyurethane elastomer).
In some cases, the rubber 57 of the transversal stiffening rod 36 _xmay be more rigid and/or harder than the elastomeric material 38 or 41 of the track 21 in contiguous regions of the track 21 where there is no transversal stiffening rod. For example, in some embodiments, the rubber 57 of the transversal stiffening rod 36 _xmay be less elastic, i.e., have a higher modulus of elasticity, and/or harder, i.e., have a higher hardness, than the elastomeric material 38 or 41 of the track 21 in contiguous regions of the track 21 where is there is no transversal stiffening rod.
In other cases, the rubber 57 of the transversal stiffening rod 36 _xmay be less rigid and/or less hard than the elastomeric material 38 or 41 of the track 21 in contiguous regions of the track 21 where there is no transversal stiffening rod. For example, in some embodiments, the rubber 57 of the transversal stiffening rod 36 _xmay be more elastic, i.e., have a lower modulus of elasticity, and/or less hard, i.e., have a lower hardness, than the elastomeric material 38 or 41 of the track 21 in contiguous regions of the track 21 where is there is no transversal stiffening rod.
For example, in some embodiments, a ratio of the modulus of elasticity of the rubber 57 of the transversal stiffening rod 36 _xto the modulus of elasticity of the elastomeric material 38 or 41 of the track 21 in contiguous regions of the track 21 where is there is no transversal stiffening rod may be at least 0.75, in some cases at least 1, and in some cases at least 1.1, and in some cases even more. Alternatively or additionally, in some embodiments, a ratio of the hardness of the rubber 57 of the transversal stiffening rod 36 _xto the hardness of the elastomeric material 38 or 41 of the track 21 in contiguous regions of the track 21 where is there is no transversal stiffening rod may be at least 0.75, in some cases at least 1, in some cases at least 1.1, and in some cases even more.
For instance, in some embodiments, the hardness of the rubber 57 of the transversal stiffening rod 36 _xmay at least 60 durometers A, in some cases at least 80 durometers A, in some cases at least 90 durometers A, and in some cases even more. The hardness of the rubber 57 of the transversal stiffening rod 36 _xmay have any other suitable value in other embodiments.
The fibers 56 ₁-56 _Fmay be implemented in various manners. In this embodiment, each of the fibers 56 ₁-56 _Fextends along at least a majority of a length of the transversal stiffening rod 36 _x. More particularly, in this case, each of the fibers 56 ₁-56 _Fextends along all of the length of the transversal stiffening rod 36 _x. In other embodiments, each of the fibers 56 ₁-56 _Fmay be shorter. For example, in other embodiments, the fibers 56 ₁-56 _Fmay be “chopped” or otherwise cut fibers which are few millimeters or centimeters long and are distributed throughout the transversal stiffening rod 36 _x.
In this embodiment, the fibers 56 ₁-56 _Fare polymeric fibers. More specifically, in this example, the fibers 56 ₁-56 _Fare aramid fibers. Various other types of polymeric fibers may be used in other examples (e.g., polyvinyl alcohol (PVA) fibers). Also, in other embodiments, the fibers 56 ₁-56 _Fmay be any other suitable type of fibers (e.g., metallic fibers, carbon fibers, glass fibers, etc.).
The transversal stiffening rod 36 _xmay be manufactured using various techniques. For example, in some embodiments, the transversal stiffening rod 36 _xmay be manufactured using an extrusion process or a pultrusion process in which the fibers 56 ₁-56 _Fare incorporated during extrusion or pultrusion of the elongated elastomeric body 55 of the rod. In other embodiments, the elongated elastomeric body 55 of the rod may be molded with the fibers 56 ₁-56 _Finside a mold. For instance, two or more strips or other suitably-sized pieces of rubber reinforced with the fibers 56 ₁-56 _Fhaving a width generally corresponding to that of the transversal stiffening rod 36 _xmay be cut from calendared fiber-reinforced rubber and layered on top of one another such that, during molding, they form the transversal stiffening rod 36 _x.

3.2 Rod Made of Composite Material

In some embodiments, a transversal stiffening rod 36 _xmay be made of composite material. For instance, in some embodiments, a transversal stiffening rod 36 _xmay be made of a carbon fiber reinforced plastic material.
4. Zones with Different Elastomeric Material Properties
In some embodiments, elastomeric material of certain zones of the endless track 21 may have different hardness and/or different elasticity in order to reduce noise generation and/or provide other benefits (e.g., controlled rigidity). Various zones with different hardness and/or elasticity can be implemented in various embodiments, examples of which are discussed below.
4.1 Hardness and/or Modulus of Elasticity of Elastomeric Material of Ground-Engaging Outer Side is Lower than Hardness and/or Modulus of Elasticity of Elastomeric Material of Carcass
In some embodiments, as shown in FIG. 27, the hardness and/or the modulus of elasticity of elastomeric material of the ground-engaging outer side 27 of the endless track 21 may be lower than the hardness and/or the modulus of elasticity of the elastomeric material 38 of the carcass 35 of the track 21. This may help to reduce noise generated.
More particularly, in this embodiment, the hardness and/or the modulus of elasticity of the rubber 41 of a traction projection 58 _xis lower than the hardness and/or the modulus of elasticity of the rubber 38 of the carcass 35. For example, in some embodiments, a ratio of the hardness of the rubber 41 of the traction projection 58 _xto the hardness of the rubber 38 of the carcass 35 may be no more than 0.9, in some cases no more than 0.8, and in some cases no more than 0.7. The hardness of the rubber 41 of the traction projection 58 _xmay have any other suitable value in other embodiments.
In embodiments where the rubber 38 of the carcass 35 is constituted of a single rubber compound, the hardness of the rubber 38 is that of the single rubber compound. In embodiments where the rubber 38 of the carcass 35 is constituted of two or more rubber compounds, the hardness of the rubber 38 is the average hardness determined based on the hardness of each of these constituent rubber compounds and their proportions (as discussed previously).
In some cases, in embodiments where the rubber 38 of the carcass 35 is constituted of two or more rubber compounds, the hardness of the rubber 41 of the traction projection 58 _xmay be lower than the hardness of an outer layer of the rubber 38 of the carcass 35 which forms the ground-engaging outer surface 31 of the carcass 35.
As another example, in some embodiments, a ratio of the modulus of elasticity of the rubber 41 of the traction projection 58 _xto the modulus of elasticity of the rubber 38 of the carcass 35 may be no more than 0.9, in some cases no more than 0.8, and in some cases no more than 0.7. The modulus of elasticity of the rubber 41 of the traction projection 58 _xmay have any other suitable value in other embodiments.
In embodiments where the rubber 38 of the carcass 35 is constituted of a single rubber compound, the modulus of elasticity of the rubber 38 is that of the single rubber compound. In embodiments where the rubber 38 of the carcass 35 is constituted of two or more rubber compounds, the modulus of elasticity of the rubber 38 is the average modulus of elasticity determined based on the modulus of elasticity of each of these constituent rubber compounds and their proportions (as discussed previously).
In some cases, in embodiments where the rubber 38 of the carcass 35 is constituted of two or more rubber compounds, the modulus of elasticity of the rubber 41 of the traction projection 58 _xmay be lower than the modulus of elasticity of the outer layer of the rubber 38 of the carcass 35 which forms the ground-engaging outer surface 31 of the carcass 35.
4.2 Hardness and/or Modulus of Elasticity of Elastomeric Material at Widthwise Position of Idler Wheel Path is Lower than Hardness and/or Modulus of Elasticity of Elastomeric Material at Widthwise Position Outside of Idler Wheel Path
In some embodiments, as shown in FIG. 28, elastomeric material 59 of the endless track 21 at a widthwise position of an idler wheel path 50 _imay be less hard and/or more elastic than elastomeric material 60 of the endless track 21 at a widthwise position outside every idler wheel path. This forms a “shock absorption zone” that provides shock absorption, and thus reduces noise generation, when a given one of the idler wheels 26 ₁-26 ₄, 28 ₁-28 ₆, 30 ₁, 30 ₂which runs on the idler wheel path 50 _icrosses the transversal stiffening rods 36 ₁-36 _N. This is an example of an embodiment in which a shock absorbency (i.e., a capacity to absorb shocks) of the track 21 at the widthwise position of the idler wheel path 50 _iis greater than a shock absorbency of the track 21 at a widthwise position outside the idler wheel path 50 _i.
More particularly, in this embodiment, the elastomeric material 59 and the elastomeric material 60 are adjacent portions of the rubber 38 of the carcass 35. In this example, the rubber 59 extends outwardly in the thickness direction of the track 21 from the inner surface 32 of the carcass 35. The elastomeric material 59 may have any suitable thickness. For instance, in some cases, the thickness of the rubber 59 may correspond to at least 10% of the thickness T_Cof the carcass 35, in some cases at least 20% of the thickness T_Cof the carcass 35, in some cases at least 30% of the thickness T_Cof the carcass 35, in some cases at least 40% of the thickness T_Cof the carcass, and in some cases even more. In some cases, the rubber 59 may extend from the inner surface 32 to the ground-engaging outer surface 31 of the carcass 35, i.e., the thickness of the rubber 59 may correspond to the thickness T_Cof the carcass 35.
As an example, in some embodiments, a ratio of the hardness of the rubber 59 at the widthwise position of the idler wheel path 50 _ito the hardness of the rubber 60 at a widthwise position outside of every idler wheel path may be no more than 0.9, in some cases no more than 0.8, in some cases no more than 0.7, and in some cases even less (e.g., no more than 0.5).
For instance, in some embodiments, the hardness of the rubber 59 at the widthwise position of the rolling path 50 _imay no more than 80 durometers A, in some cases no more than 70 durometers A, in some cases no more than 60 durometers A, and in some cases even less. The hardness of the rubber 59 may have any other suitable value in other embodiments.
In embodiments where the rubber 59 or 60 of the carcass 35 is constituted of a single rubber compound, the hardness of the rubber 59 or 60 is that of the single rubber compound. In embodiments where the rubber 59 or 60 of the carcass 35 is constituted of two or more rubber compounds, the hardness of the rubber 59 or 60 is the average hardness determined based on the hardness of each of these rubber compounds and their proportions (as discussed previously).
As another example, in some embodiments, a ratio of the modulus of elasticity of the rubber 59 at the widthwise position of the rolling path 50 _ito the modulus of elasticity of the rubber 60 outside of every rolling path may be no more than 0.9, in some cases no more than 0.8, in some cases no more than 0.7, and in some cases even less (e.g., no more than 0.5).
In embodiments where the rubber 59 or 60 of the carcass 35 is constituted of a single rubber compound, the modulus of elasticity of the rubber 59 or 60 is that of the single rubber compound. In embodiments where the rubber 59 or 60 of the carcass 35 is constituted of two or more rubber compounds, the modulus of elasticity of the rubber 59 or 60 is the average modulus of elasticity determined based on the modulus of elasticity of each of these rubber compounds and their proportions (as discussed previously).
While in embodiments considered above the rubber 59 forming an absorption zone extends outwardly from the inner surface 32 of the carcass 35, in other embodiments, the rubber 59 may extend inwardly from the ground-engaging outer surface 31 of the carcass 32 without reaching the inner surface 32 of the carcass 35, as shown in FIG. 29, or may be embedded in the carcass 35 without reaching either of its inner surface 32 and ground-engaging outer surface 31, as shown in FIG. 30.
FIG. 31 shows another embodiment in which elastomeric material 61 of the endless track 21 at a widthwise position of an idler wheel path 50 _iis less hard and/or more elastic than elastomeric material 62 of the endless track 21 at a widthwise position outside every idler wheel path. In this embodiment, the elastomeric material 61 and the elastomeric material 62 are adjacent portions of the rubber 41 of a traction projection 58 _x. In some embodiments, the hardness and/or the modulus of elasticity of each of the rubber 61 and the rubber 62 may be selected as discussed above in respect of the rubber 59 or 60 of the carcass 35.
In embodiments considered above, the rubber 59 and the rubber 60 of the carcass 35, and the rubber 61 and the rubber 62 of the traction projection 58 _x, may be provided during manufacturing of the endless track 21 by placing pieces of rubber (e.g., cut sheets or blocks of rubber) corresponding to these rubber portions in a mold such that, after molding, they form these rubber portions of track 21.

5. Transversal Stiffening Cables

In some embodiments, as shown in FIG. 32A, the endless track 21 may comprise a layer of transversal stiffening cables 63 ₁-63 _Twhich are generally parallel to one another and extend transversally to the longitudinal direction of the track 21 to provide transverse rigidity. More particularly, in this embodiment, the transversal stiffening cables 63 ₁-63 _Textend in the widthwise direction of the track 21.
The transversal stiffening cables 63 ₁-63 _Tmay be any suitable type of cable. For example, in some embodiments, each of the transversal stiffening cables 63 ₁-63 _Tmay be a cord including a plurality of strands (e.g., textile fibers or metallic wires). In other embodiments, each of the transversal stiffening cables 63 ₁-63 _Tmay include a single strand and/or may be made of any other suitable material (e.g., metal, plastic or composite material).
The layer of transversal stiffening cables 63 ₁-63 _Tcan be implemented in various ways. For example, in this embodiment, the layer of transversal stiffening cables 63 ₁-63 _Tis a layer of tire cord fabric in which the transversal stiffening cords 63 ₁-63 _Tare interlaced with longitudinal strands 68 ₁-68 _Sthat run generally along the longitudinal direction of the track 21. In other embodiments, the transversal stiffening cables 63 ₁-63 _Tmay not be interlaced with any other fabric members but may rather be unconnected other than by the rubber of the track 21.
In some embodiments, as shown in FIG. 32B, the track 21 may be free of transversal stiffening rods but have sufficient transversal rigidity because of the transversal stiffening cables 63 ₁-63 _T.
In other embodiments, as shown in FIG. 32C, the track 21 may include the transversal stiffening rods 36 ₁-36 _Nalong with the transversal stiffening cables 63 ₁-63 _T. In some examples of implementation, the transversal stiffening rods 36 ₁-36 _Nmay be smaller than conventional rods since the transversal stiffening cables 63 ₁-63 _Tassist in providing transversal rigidity. For instance, in this case, each of the transversal stiffening rods 36 ₁-36 _Nhas a cross-section with a high aspect ratio and a generally rectangular shape, i.e., it is a plate-like or “ruler” rod, as discussed above in section 1.1.1. The transversal stiffening rods 36 ₁-36 _Nmay have any other suitable shapes in other embodiments. Also, in this example, the layer of transversal stiffening cables 63 ₁-63 _Tis located between the transversal stiffening rods 36 ₁-36 _Nand the ground-engaging outer side 27 of the track 21. In other examples, the layer of transversal stiffening cables 63 ₁-63 _Tmay be located between the transversal stiffening rods 36 ₁-36 _Nand the inner side 25 of the track 21.
In this case, the transversal stiffening rods 36 ₁-36 _Nare distributed in the track 21 such that there is one transversal stiffening rod 36 _ibeneath every traction projection 58 _iof the track 21. In other words, a longitudinal spacing or pitch of the transversal stiffening rods 36 ₁-36 _Nmay correspond to a longitudinal spacing or pitch of the traction projection 58 ₁-58 _T.
In other cases, as shown in FIG. 32D, the transversal stiffening rods 36 ₁-36 _Nmay be distributed in the track 21 such that there is no transversal stiffening rod 36 _ibeneath at least some of the traction projection 58 ₁-58 _Tof the track 21. In such cases, the longitudinal spacing or pitch of the transversal stiffening rods 36 ₁-36 _Nis greater than the longitudinal spacing or pitch of the traction projection 58 ₁-58 _T. For instance, in this embodiment, there is one transversal stiffening rod 36 _iat every two of the traction projections 58 ₁-58 _T. The longitudinal spacing or pitch of the transversal stiffening rods 36 ₁-36 _Nmay be even greater in other examples (e.g., one transversal stiffening rod 36 _iat every three or four of the traction projection 58 ₁-58 _T).

6. Carcass Periphery

In some embodiments, a periphery of the carcass 35, including its inner surface 32 and its ground-engaging outer surface 31, may be configured to reduce noise generation and/or provide other benefits (e.g., controlled rigidity). This can be achieved in various ways in various embodiments, examples of which will be discussed.

6.1 Idler Wheel Path Projections on Carcass Outer Surface Between Adjacent Traction Projections

In some embodiments, as shown in FIGS. 33A and 33B, the ground-engaging outer surface 31 of the carcass 35 may define a plurality of idler wheel path projections 64 ₁-64 _Pwhich are located between adjacent ones of the traction projections 58 ₁-58 _Tin the longitudinal direction of the track and which are aligned with respective ones of the idler wheel paths 50 ₁-50 ₄in the widthwise direction of the track 21 (i.e., overlap with respective ones of the idler wheel paths 50 ₁-50 ₄in the widthwise direction of the track 21). The idler wheel path projections 64 ₁-64 _Pmay help to reduce noise generation when they are crossed over by respective ones of the idler wheels 26 ₁-26 ₄, 28 ₁-28 ₆, 30 ₁, 30 ₂.
For example, when a lower roller wheel 28 _ion a rolling path 50 _iarrives where an idler wheel rolling path projection 64 _xis located, the idler wheel rolling path projection 64 _xcontacts the ground and counters a tendency of the carcass 35 to deflect downwardly under loading of the lower roller wheel 28 _i.
In this embodiment, each idler wheel rolling path projection 64 _xis uneven along the longitudinal direction of the track 21. More particularly, in this case, the idler wheel rolling path projection 64 _xis curved along the longitudinal direction of the track 21 so that its thickness varies longitudinally.
The idler wheel path projections 64 ₁-64 _Pmay be configured in various other ways in other embodiments. For example, in some embodiments, as shown in FIGS. 34A and 34B, each of the idler wheel path projections 64 ₁-64 _Pmay be generally flat along the longitudinal direction of the track 21 and may occupy all of a longitudinal extent between adjacent ones of the traction projection 58 ₁-58 _Tsuch that the idler wheel path projections 64 ₁-64 _Pform “continuous” raised longitudinal bands 69 ₁-69 ₄on the ground-engaging outer side 27 of the track 21.
6.2 Longitudinal Rigidifiers on Carcass Inner Surface and/or Outer Surface
In some embodiments, as shown in FIGS. 38 and 39, the inner surface 32 and/or the ground-engaging outer surface 31 of the carcass 35 of the endless track 21 may comprise a plurality of longitudinal rigidifiers 70 ₁-70 _Rfor imparting longitudinal rigidity to the track 21. Each of the longitudinal rigidifiers 70 ₁-70 _Ris an elastomeric formation, such as a projection or recess, formed in the rubber of the carcass 35 that increases the longitudinal rigidity of the track 21 compared to if the track 21 lacked the longitudinal rigidifiers 70 ₁-70 _Rbut was otherwise identical. The increased longitudinal rigidity of the track 21 may help to reduce deflection of the track 21 when the idler wheels roll on the bottom run of the track 21.
In this embodiment, the longitudinal rigidifiers 70 ₁-70 _Rare longitudinally-rigidifying projections formed in the inner surface 32 of the track 32. More particularly, in this example of implementation, the longitudinally-rigidifying projections 70 ₁-70 _Rare shaped as raised strips that are generally parallel to the longitudinal direction of the track 21. The longitudinally-rigidifying projections 70 ₁-70 _Rmay have various other shapes (e.g., narrower ridges or ribs) and/or may have various other orientations (e.g., oblique) relative to the longitudinal direction of the track 21 in other examples of implementation. In other embodiments, instead of being projections, the longitudinal rigidifiers 70 ₁-70 _Rmay be longitudinally-rigidifying recesses (e.g., grooves that are generally parallel to the longitudinal direction of the track 21). In yet other embodiments, the longitudinal rigidifiers 70 ₁-70 _Rmay include both longitudinally-rigidifying projections and longitudinally-rigidifying recesses.
The longitudinal rigidifiers 70 ₁-70 _Rmay be arranged in various ways. For example, in this embodiment, the longitudinal rigidifiers 70 ₂, 70 ₄are located where the idler wheel paths 50 ₂, 50 ₃are located while the longitudinal rigidifiers 70 ₁, 70 ₃, 70 ₅are located outside of the idler wheel paths 50 ₁-50 ₄.
Although in this embodiment the longitudinal rigidifiers 70 ₁-70 _Rare located on the inner surface 32 of the carcass 35, in other embodiments, similar longitudinal rigidifiers may be located on the ground-engaging outer surface 31 of the track 21 in addition to or instead of the longitudinal rigidifiers 70 ₁-70 _Ron the inner surface 32.

6.3 Longitudinally Uneven Idler Wheel Path

In some embodiments, as shown in FIG. 35, an idler wheel path 50 _ion the inner surface 32 of the carcass 35 may be uneven in the longitudinal direction of the endless track 21. For example, in this embodiment, the idler wheel path 50 _iincludes a series of idler wheel path formations 67 ₁-67 _Fdistributed in the longitudinal direction of the track 21. The formations 67 ₁-67 _Fconstitute a deformable shock-absorbing zone in the idler wheel path 50 _isuch that, when idler wheels contact some of these formations 67 ₁-67 _F, the formations 67 ₁-67 _Fcan deform to absorb the shock and thus reduce noise generation. In this case, the formations 67 ₁-67 _Finclude recesses. In other cases, the formations 67 ₁-67 _Fmay include projections or a combination of recesses and projections. This is an example of an embodiment in which a shock absorbency (i.e., a capacity to absorb shocks) of the track 21 at the widthwise position of the idler wheel path 50 _iis greater than a shock absorbency of the track 21 at a widthwise position outside the idler wheel path 50 _i.
A longitudinal spacing of adjacent ones of the idler wheel path formations 67 ₁-67 _Fmay be selected so as to allow proper deformability for shock absorbance yet avoid creating unwanted vibrational effects as some of the idler wheels 26 ₁-26 ₄, 28 ₁-28 ₆, 30 ₁, 30 ₂roll over these formations 67 ₁-67 _F. For example, in some embodiments, the longitudinal spacing of adjacent ones of the idler wheel path formations 67 ₁-67 _Fmay be no more than 5 mm, in some cases no more than 4, and in some cases no more than 3 mm. The longitudinal spacing of adjacent ones of the idler wheel path formations 67 ₁-67 _Fmay have any other suitable value in other embodiments.

7. Track Elastomeric Material

In some embodiments, elastomeric material of the track 21 may have certain characteristic which may help to reduce noise generation and/or provide other benefits (e.g., controlled rigidity).

7.1 Fiber-Reinforced Elastomeric Material

In some embodiments, as shown in FIG. 44, the track 21 may be at least mainly (i.e., entirely or mainly) made of fiber-reinforced elastomeric material which comprises an elastomeric matrix 87 in which are embedded fibers 89 ₁-89 _F. In other words, at least a bulk of the track 21 may be made of the fiber-reinforced elastomeric material. In this embodiment, the fibers 89 ₁-89 _Fgenerally extend transversally to the longitudinal direction of the track 21. This can provide transversal rigidity to the track 21.
In this embodiment, at least part of (i) the carcass 35, (ii) a traction projection 58 _x, and (iii) a drive/guide lug 34 _xof the track 21 are made of the fiber-reinforced elastomeric material. More particularly, in this embodiment, at least a majority of (i) the carcass 35, (ii) a traction projection 58 _x, and (iii) a drive/guide lug 34 _xof the track 21 are made of the fiber-reinforced elastomeric material. In this example, the track 21 is entirely made of the fiber-reinforced elastomeric material except for any reinforcement, such as the transversal stiffening rods 36 ₁-36 _N, the reinforcing cables 37 ₁-37 _M, or the reinforcing fabric 43, which may be embedded in the fiber-reinforced elastomeric material.
The elastomeric matrix 87 may include any suitable elastomer. In some cases, the elastomeric matrix 87 may include a single elastomer (e.g., rubber). In other cases, the elastomeric matrix 87 may include two or more constituent elastomers (e.g., two or more different rubber compounds, one or more rubber compounds along with one or more other types of elastomer, etc.).
In this embodiment, each of the fibers 89 ₁-89 _Fis a “short” fiber. For example, in some embodiments, each of the fibers 89 ₁-89 _Fmay have a length of no more than 10% of the width of the track 21, in some cases no more than 5% of the width of the track 21, in some cases no more than 3% of the width of the track 21, and in some cases even less (e.g., no more than 2% of the width of the track 21). For instance, in some embodiments, the length of each of the fibers 89 ₁-89 _Fmay be no more than 30 mm, in some cases no more than 20 mm, in some cases no more than 10 mm, and in some cases even less (e.g., no more than 5 mm). In this example of implementation, the fibers 89 ₁-89 _Fare “chopped” or otherwise cut fibers.
In other embodiments, each of the fibers 89 ₁-89 _Fmay be a “long” fiber that extends along at least a majority of the width of the track 21. For instance, in some cases, each of the fibers 89 ₁-89 _Fmay extends along all of the width of the track.
The fibers 89 ₁-89 _Fmay be made of any suitable material. In this embodiment, the fibers 89 ₁-89 _Fare polymeric fibers. More specifically, in this example, the fibers 89 ₁-89 _Fare aramid fibers (e.g., Kevlar fibers). Various other types of polymeric fibers may be used in other examples (e.g., polyvinyl alcohol (PVA) fibers). Also, in other embodiments, the fibers 89 ₁-89 _Fmay be any other suitable type of fibers (e.g., metallic fibers, carbon fibers, glass fibers, etc.).
In some embodiments, as it may provide transversal rigidity and/or other reinforcing effects, the fiber-reinforced elastomeric material of the track 21 may allow fewer or modified reinforcements to be embedded in it. For example, in this embodiment, the transversal stiffening rods 36 ₁-36 _Nhave a high aspect ratio (e.g., are plate-like or “ruler” rods) and the track 21 is free of reinforcing fabric, as discussed previously.
The track 21 and its fiber-reinforced elastomeric material may be produced using various techniques. For example, in some embodiments, sheets of fiber-reinforced elastomeric material, which include respective portions of the elastomeric matrix 87 and respective ones of the fibers 89 ₁-89 _F, may be produced by calendaring, extrusion, pultrusion or any other process in which those fibers are incorporated into that portion of the elastomeric matrix 87. These sheets may then be placed into a mold for molding the track 21 such that the respective portions of the elastomeric matrix 87 and the respective ones of the fibers 89 ₁-89 _Fof these sheets are combined into the track 21. Various other manufacturing processes may be used in other embodiments.

7.2 Slipper Elastomeric Material

In some embodiments, at least part of the elastomeric material of the track 21, including the elastomeric material 38 of the carcass 35, may include “slipper” rubber 66. The slipper rubber 66 forms at least part of the inner surface 32 of the carcass 35 on which the slide rails 33 ₁, 33 ₂slide. The slipper rubber 66 exhibits a migration of lubricant (e.g., oil) contained within itself to the inner surface 32 of the carcass 35 in use. This helps to reduce friction between the slide rails 33 ₁, 33 ₂and the track 21. As a result, this reduced friction may allow a reduction in number of the slide clips 39 ₁-39 _Son the track 21 or the track 21 to be free of slide clips altogether. By reducing or eliminating contact between the slide rails 33 ₁, 33 ₂and slide clips, noise generation is reduced. Any suitable type of slipper rubber which exhibits oil migration to its surface may be used.

7.3 Cellular Elastomeric Material

In some embodiments, at least part of the elastomeric material of the track 21, such as the elastomeric material 38 of the carcass 35, may include cellular elastomeric material 71 (e.g., cellular rubber) at a widthwise position of an idler wheel path 50 _i. The cellular elastomeric material 71 is elastomeric material which contains cells (e.g., bubbles) created by introducing a gas (e.g., air) or a gas-producing agent (e.g., sodium bicarbonate) during manufacturing of the cellular elastomeric material 71. The cells of the cellular elastomeric material 71 may include closed cells and/or open cells. The cellular elastomeric material 71 creates a deformable shock-absorbing zone in the idler wheel path 50 _isuch that, when idler wheels roll over the cellular elastomeric material 71, the cellular elastomeric material 71 can deform more than if it was non-cellular (i.e., the same elastomeric compound but without cells) to absorb the shock and thus reduce noise generation. Any suitable type of cellular elastomeric material which provides shock-absorption may be used. This is an example of an embodiment in which a shock absorbency (i.e., a capacity to absorb shocks) of the track 21 at the widthwise position of the idler wheel path 50 _iis greater than a shock absorbency of the track 21 at a widthwise position outside the idler wheel path 50 _i.

8. Track-Engaging Assembly

In some embodiments, the track-engaging assembly 24, including the wheels 22 ₁, 22 ₂, 26 ₁-26 ₄, 28 ₁-28 ₆, 30 ₁, 30 ₂and the slide rails 33 ₁, 33 ₂, may be configured to reduce noise generation and/or provide other benefits (e.g., enhanced load distribution). Examples of how this may be achieved are discussed below.

8.1 Suspension Providing Increased Support

In some embodiments, the suspension unit 16 of the track-engaging assembly 24 may provide increased support. This can be achieved in various ways.

8.1.1 Additional Idler Wheels

In some embodiments, as shown in FIG. 40, a number of idler wheels of the track-engaging assembly 24 that engage the bottom run 66 of the endless track 21 may be increased. For instance, in some embodiments, the track-engaging assembly 24 may comprise a set of idler wheels spaced apart in the longitudinal direction of the track system 14 and substantially aligned with one another to roll on a given idler wheel path 50 _ion the bottom run 66 of the track 21 such that a longitudinal spacing V_wof any two successive idler wheels of the set of idler wheels on the idler wheel path 50 _iis less than half of the length of the track system 14, in some cases no more than 40% of the length of the track system 14, in some cases no more than 30% of the length of the track system 14, in some cases no more than 20% of the length of the track system 14, and in some cases even less (e.g., no more than 10% of the length of the track system 14).
For example, in this embodiment, the track-engaging assembly 24 comprises at least four idler wheels spaced apart in the longitudinal direction of the track 21 and substantially aligned with one another so as to roll on a given idler wheel path 50 _ion the bottom run 66 of the track 21. In this case, there are six idler wheels rolling on the given idler wheel path 50 _i. In other cases, there may be four, five, or more than six idler wheels rolling on the given idler wheel path 50 _i.
More particularly, in this embodiment, the track-engaging assembly 24 comprises a set of six idler wheels 26 ₁, 28A₁-28A₅rolling on the leftmost idler wheel path 50 ₁and a set of six idler wheels 26 ₄, 28A₆-28A₁₀rolling on the rightmost idler wheel path 50 ₄. Also, in this embodiment, the track-engaging assembly 24 comprises idler wheels 26 ₂, 26 ₃, 28B₁-28B₄which are located between the idler wheels 26 ₁, 28A₁-28A₅and the idler wheels 26 ₄, 28A₆-28A₁₀in the widthwise direction of the track 21 and roll on the idler wheel paths 50 ₂, 50 ₃. Various other wheel configurations are possible in other embodiments.
In this example of implementation, the idler wheels 26 ₁-26 ₄, 28A₁-28A₁₂, 28B₁-28B₄are mounted to elongated wheel-supporting members 33A₁, 33A₂of the track-engaging assembly 24. In this case, the elongated wheel-supporting members 33A₁, 33A₂are not designed primarily to slide on the track 21 like the slide rails 33 ₁, 33 ₂discussed above but are rather designed primarily for supporting the idler wheels 26 ₁-26 ₄, 28A₁-28A₁₂, 28B₁-28B₂. In other cases, the elongated wheel-supporting members 33A₁, 33A₂may slide on the track 21 like the slide rails 33 ₁, 33 ₂discussed above and thus may also constitute slide rails.

8.1.2 Additional Slide Rails

In some embodiments, as shown in FIG. 41, a number of slide rails of the track-engaging assembly 24 that slide along the bottom run 66 of the endless track 21 may be increased. For instance, in some embodiments, the track-engaging assembly 24 may comprises a plurality of side rails spaced apart in the widthwise direction of the track system 14 such that a widthwise spacing V_rof any two adjacent slide rails is less than half of the width of the track system 14, in some cases no more than 40% of the width of the track system 14, in some cases no more than 30% of the width of the track system 14, in some cases no more than 20% of the width of the track system 14, and in some cases even less (e.g., no more than 10% of the width of the track system 14).
For example, in this embodiment, the track-engaging assembly 24 comprises at least three slide rails spaced apart in the widthwise direction of the track 21. In this case, there are four slide rails. In other cases, there may be three, five, or more than five slide rails.
More particularly, in this embodiment, the track-engaging assembly 24 comprises four slide rails 33A₁-33A₄which are evenly distributed in the widthwise direction of the track 21. In this case, the slide rails 33A₁-33A₄are substantially identical in size and shape. Also, in this case, the idler wheels 26 ₁-26 ₄, 28 ₁-28 ₆are mounted to respective ones of the slide rails 33A₁-33A₄. Various other slide rail configurations are possible in other embodiments (e.g., the slide rails 33A₁-33A₄may not be evenly distributed in the widthwise direction of the track 21; two or more of the slide rails 33A₁-33A₄may differ in size and/or shape; one or more of the slide rails 33A₁-33A₄may not have any idler wheel mounted thereto).

8.2 Extremely Low-Friction Slide Rails

In some embodiments, the slide rails 33 ₁, 33 ₂may include very low friction material to minimize as much as possible their friction with the endless track 21.
In some cases, the slide rails 33 ₁, 33 ₂may have a friction of coefficient with the endless track 21 that is low enough to allow the track 21 to be free of slide members (i.e., “clips”) such as the slide members 39 ₁-39 _Sdiscussed previously without detrimentally affecting performance of the track system 14.

8.3 Track Tensioner

In some embodiments, as shown in FIG. 42, the track-engaging assembly 24 may comprise a track tensioner 72 for maintaining tension of the endless track 21. This may counter a tendency of the track 21 to stretch due to centrifugal forces when it is driven at high speeds. In this embodiment, the track tensioner 72 is connected between a structural support 74 of the track-engaging assembly 24 and the rear idler wheels 26 ₁-26 ₄to urge the rear idler wheels 26 ₁-26 ₄in a direction to maintain the tension of the track 21.
The track tensioner 72 comprises a resilient device 73 configured to change from a first configuration to a second configuration in response to a load and return to the first configuration in response to removal of the load. More particularly, in this embodiment, the track tensioner 72 is a fluidic tensioning system, e.g., a hydraulic or pneumatic tensioning system, and the resilient device 73 is a piston-cylinder actuator connected to a fluid reservoir (not shown). In this example of implementation, the actuator 73 is a hydraulic piston-cylinder actuator.
In this embodiment, the piston-cylinder actuator 73 is connected to the structural support 74 and to an idler wheel carrier 75 which carries an axle of the rear idler wheels 26 ₁-26 ₄and which can move in slots 76 ₁, 76 ₂defined by the slide rails 33 ₁, 33 ₂. The tensioning actuator 73 can apply the tension in the track 21 by extending or retracting to move the idler wheel carrier 75 in the slots 76 ₁, 76 ₂and thus move rear idler wheels 26 ₁-26 ₄further or closer to the drive wheels 22 ₁, 22 ₂.
The track tensioner 72 may be configured in various other ways in other embodiments.
For example, in some embodiments, the resilient device 73 may comprise a spring such as a coil spring (e.g., a metallic or polymeric coil spring), an elastomeric spring or a leaf spring, or any other device that changes in configuration under load and recovers its initial configuration when the load is removed.
As another example, in other embodiments, the track tensioner 72 may be located elsewhere and/or act on a different part of the track 21. For instance, FIG. 43 shows an embodiment in which the track tensioner 72 comprises a first resilient device 91 ₁contacting a first segment 92 ₁of the top run 65 of the track 21 which extends between the rear idler wheels 26 ₁-26 ₄and the upper roller wheels 30 ₁, 30 ₂and a second resilient device 91 ₂contacting a second segment 92 ₂of the top run 65 of the track 21 which extends between the upper roller wheels 30 ₁, 30 ₂and the drive wheels 22 ₁, 22 ₂. In this embodiment, each resilient device 91 comprises a roller wheel 95 and a spring 93 that is connected between the roller wheel 95 and a structural support 94 of the track-engaging assembly 24 in order to urge the roller wheel 95 against the track 21 to tension the track 21. This can help to counter a tendency of the segments 92 ₁, 92 ₂of the top run 65 of the track 21 to deform since they would otherwise be unsupported.
Instead of or in addition to using a track tensioner 72, in some embodiments, the endless track 21 may comprise a substantially inextensible material that can substantially prevent the track 21 from stretching in a range of speeds at which it is expected to be driven. For example, in some embodiments, the reinforcing cables 37 ₁-37 _Mof the track 21 may comprise Kevlar™ cables.
Although embodiments described above have been presented individually, any feature of any embodiment described above may be used in combination with any feature of any other embodiment described above.
While embodiments described above relate to a snowmobile, in other embodiments, any feature of any embodiment described above may be used in another type of off-road vehicle.
For example, in some embodiments, as shown in FIGS. 45A and 45B, any feature of any embodiment described above may be used in an all-terrain vehicle (ATV) 110 comprising a set of track systems 114 ₁-114 ₄providing traction to the ATV on the ground. The ATV 10 comprises a prime mover 112 in a driving relationship with the track systems 114 ₁-114 ₄via the ATV's powertrain, a seat 118, and a user interface 120, which enable a user of the ATV 110 to ride the ATV 110 on the ground. In this case, the seat 118 is a straddle seat and the ATV 110 is usable by a single person such that the seat 118 accommodates only that person driving the ATV 110. In other cases, the seat 118 may be another type of seat, and/or the ATV 110 may be usable by two individuals, namely one person driving the ATV 110 and a passenger, such that the seat 118 may accommodate both of these individuals (e.g., behind one another or side-by-side) or the ATV 110 may comprise an additional seat for the passenger. For example, in other embodiments, the ATV 110 may be a side-by-side ATV, sometimes referred to as a “utility terrain vehicle” or “UTV”. The user interface 120 comprises a steering device operated by the user to control motion of the ATV 110 on the ground. In this case, the steering device comprises handlebars. In other cases, the steering device may comprise a steering wheel or other type of steering element. Each of the front track systems 114 ₁, 114 ₂is pivotable about a steering axis of the ATV 110 in response to input of the user at the handlebars in order to steer the ATV 110 on the ground.
In this embodiment, with additional reference to FIGS. 46A and 46B, each track system 114 _iis mounted in place of a ground-engaging wheel 113 _ithat may otherwise be mounted to the ATV 110 to propel the ATV 110 on the ground. That is, the ATV 110 may be propelled on the ground by four ground-engaging wheels 113 ₁-113 ₄with tires instead of the track systems 114 ₁-114 ₄. Basically, in this embodiment, the track systems 114 ₁-114 ₄may be used to convert the ATV 110 from a wheeled vehicle into a tracked vehicle, thereby enhancing its traction and floatation on the ground.
Any feature described herein with respect to the track system 14 of the snowmobile 10 may be applied to a track system 114 _iof the ATV 110.
The snowmobile 10 and the ATV 110 considered above are examples of tracked recreational vehicles. While they can be used for recreational purposes, such tracked recreational vehicles may also be used for utility purposes in some cases.
Certain additional elements that may be needed for operation of certain embodiments have not been described or illustrated as they are assumed to be within the purview of those of ordinary skill in the art. Moreover, certain embodiments may be free of, may lack and/or may function without any element that is not specifically disclosed herein.
Although various embodiments and examples have been presented, this was for the purpose of describing, but not limiting, the invention. Various modifications and enhancements will become apparent to those of ordinary skill in the art and are within the scope of the invention, which is defined by the appended claims.

Claims

1.-22. (canceled)

23. A track for traction of a vehicle, the track being mountable around a track-engaging assembly that comprises a drive wheel for driving the track and an idler wheel for contacting the track, the track comprising elastomeric material to be flexible around the track-engaging assembly, the track comprising:

an inner surface for facing the track-engaging assembly, the inner surface comprising an idler wheel path for the idler wheel;

a ground-engaging outer surface for engaging the ground;

a plurality of traction projections projecting from the ground-engaging outer surface; and

a plurality of stiffening rods extending transversally to a longitudinal direction of the track, each stiffening rod having a dimension in a thickness direction of the track that is less where the stiffening rod overlaps the idler wheel path in a widthwise direction of the track than where the stiffening rod does not overlap the idler wheel path in the widthwise direction of the track.

24. The track of claim 23, wherein the idler wheel is a roller wheel and the idler wheel path is a rolling path for the roller wheel to roll on a bottom run of the track.

25. The track of claim 23, wherein the idler wheel is a first idler wheel, the idler wheel path is a first idler wheel path, the track-engaging assembly comprises a second idler wheel spaced from the first idler wheel in a widthwise direction of the track-engaging assembly, the inner surface comprises a second idler wheel path for the second idler wheel, the second idler wheel path is spaced from the first idler wheel in the widthwise direction of the track, and the dimension of the stiffening rod in the thickness direction of the track is less where the stiffening rod overlaps the second idler wheel path in the widthwise direction of the track than where the stiffening rod does not overlap the second idler wheel path in the widthwise direction of the track.

26. The track of claim 23, wherein a ratio of (i) a difference between the dimension of the stiffening rod in the thickness direction of the track where the stiffening rod does not overlap the idler wheel path in the widthwise direction of the track and the dimension of the stiffening rod in the thickness direction of the track where the stiffening rod overlaps the idler wheel path in the widthwise direction of the track over (ii) the dimension of the stiffening rod in the thickness direction of the track where the stiffening rod does not overlap the idler wheel path in the widthwise direction of the track is at least 0.1.

27. The track of claim 23, wherein a ratio of (i) a difference between the dimension of the stiffening rod in the thickness direction of the track where the stiffening rod does not overlap the idler wheel path in the widthwise direction of the track and the dimension of the stiffening rod in the thickness direction of the track where the stiffening rod overlaps the idler wheel path in the widthwise direction of the track over (ii) the dimension of the stiffening rod in the thickness direction of the track where the stiffening rod does not overlap the idler wheel path in the widthwise direction of the track is at least 0.15.

28. The track of claim 23, wherein a ratio of (i) a difference between the dimension of the stiffening rod in the thickness direction of the track where the stiffening rod does not overlap the idler wheel path in the widthwise direction of the track and the dimension of the stiffening rod in the thickness direction of the track where the stiffening rod overlaps the idler wheel path in the widthwise direction of the track over (ii) the dimension of the stiffening rod in the thickness direction of the track where the stiffening rod does not overlap the idler wheel path in the widthwise direction of the track is at least 0.2.

29. The track of claim 23, wherein a difference between the dimension of the stiffening rod in the thickness direction of the track where the stiffening rod does not overlap the idler wheel path in the widthwise direction of the track and the dimension of the stiffening rod in the thickness direction of the track where the stiffening rod overlaps the idler wheel path in the widthwise direction of the track is at least 0.03 inches.

30. The track of claim 23, wherein a difference between the dimension of the stiffening rod in the thickness direction of the track where the stiffening rod does not overlap the idler wheel path in the widthwise direction of the track and the dimension of the stiffening rod in the thickness direction of the track where the stiffening rod overlaps the idler wheel path in the widthwise direction of the track is at least 0.045 inches.

31. The track of claim 23, wherein a difference between the dimension of the stiffening rod in the thickness direction of the track where the stiffening rod does not overlap the idler wheel path in the widthwise direction of the track and the dimension of the stiffening rod in the thickness direction of the track where the stiffening rod overlaps the idler wheel path in the widthwise direction of the track is at least 0.06 inches.

32. The track of claim 23, wherein the stiffening rod comprises a surface facing the inner surface and receding towards the ground-engaging outer surface where the stiffening rod overlaps the idler wheel path in the widthwise direction of the track.

33. The track of claim 25, wherein the stiffening rod comprises a surface facing the inner surface and receding towards the ground-engaging outer surface where the stiffening rod overlaps the first idler wheel path in the widthwise direction of the track and where the stiffening rod overlaps the second idler wheel path in the widthwise direction of the track.

34. The track of claim 23, wherein the stiffening rod comprises a recess overlapping the idler wheel path in the widthwise direction of the track.

35. The track of claim 34, wherein a depth of the recess is at least 0.03 inches.

36. The track of claim 34, wherein a depth of the recess is at least 0.045 inches.

37. The track of claim 34, wherein a depth of the recess is at least 0.06 inches.

38. The track of claim 34, wherein a ratio of a depth of the recess over the dimension of the stiffening rod in the thickness direction of the track where the stiffening rod does not overlap the idler wheel path in the widthwise direction of the track is at least 0.1.

39. The track of claim 34, wherein a ratio of a depth of the recess over the dimension of the stiffening rod in the thickness direction of the track where the stiffening rod does not overlap the idler wheel path in the widthwise direction of the track is at least 0.15.

40. The track of claim 34, wherein a ratio of a depth of the recess over the dimension of the stiffening rod in the thickness direction of the track where the stiffening rod does not overlap the idler wheel path in the widthwise direction of the track is at least 0.2.

41. The track of claim 23, wherein a longitudinal end portion of the stiffening rod overlaps the idler wheel path in the widthwise direction of the track.

42. The track of claim 25, wherein a first longitudinal end portion of the stiffening rod overlaps the first idler wheel path in the widthwise direction of the track and a second longitudinal end portion of the stiffening rod overlaps the second idler wheel path in the widthwise direction of the track.

43. The track of claim 23, comprising a plurality of reinforcing cables extending generally in the longitudinal direction of the track.

44. The track of claim 43, wherein the reinforcing cables are located between the stiffening rods and the inner surface in the thickness direction of the track.

45. The track of claim 43, wherein the reinforcing cables are located between the stiffening rods and the ground-engaging outer surface in the thickness direction of the track.

46. The track of claim 23, comprising a plurality of drive/guide projections projecting from the inner surface.

47. The track of claim 46, wherein the drive/guide projections are configured for engaging the drive wheel to drive the track.

48. The track of claim 23, wherein a thickness of the track from the inner surface to the ground-engaging outer surface is no more than 0.25 inches.

49. The track of claim 23, wherein the vehicle is a snowmobile and the track is a snowmobile track.

50. A track for traction of a vehicle, the track being mountable around a track-engaging assembly that comprises a drive wheel for driving the track and an idler wheel for contacting the track, the track comprising elastomeric material to be flexible around the track-engaging assembly, the track comprising:

an inner surface for facing the track-engaging assembly;

a ground-engaging outer surface for engaging the ground;

a plurality of stiffening rods extending transversally to a longitudinal direction of the track, each stiffening rod being shaped such that a thickness of the elastomeric material between the inner surface and a surface of the stiffening rod facing the inner surface varies in a widthwise direction of the track.

51. The track of claim 50, wherein: the inner surface comprises an idler wheel path for the idler wheel; and the thickness of the elastomeric material between the inner surface and the surface of the stiffening rod facing the inner surface is greater where the stiffening rod overlaps the idler wheel path in the widthwise direction of the track than where the stiffening rod does not overlap the idler wheel path in the widthwise direction of the track.

52. The track of claim 51, wherein the idler wheel is a roller wheel and the idler wheel path is a rolling path for the roller wheel to roll on a bottom run of the track.

53. The track of claim 51, wherein the idler wheel is a first idler wheel, the idler wheel path is a first idler wheel path, the track-engaging assembly comprises a second idler wheel spaced from the first idler wheel in a widthwise direction of the track-engaging assembly, the inner surface comprises a second idler wheel path for the second idler wheel, the second idler wheel path is spaced from the first idler wheel in the widthwise direction of the track, and the thickness of the elastomeric material between the inner surface and the surface of the stiffening rod facing the inner surface is greater where the stiffening rod overlaps the second idler wheel path in the widthwise direction of the track than where the stiffening rod does not overlap the second idler wheel path in the widthwise direction of the track.

54. The track of claim 51, wherein a ratio of (i) a difference between the thickness of the elastomeric material between the inner surface and the surface of the stiffening rod facing the inner surface where the stiffening rod overlaps the idler wheel path in the widthwise direction of the track and the thickness of the elastomeric material between the inner surface and the surface of the stiffening rod facing the inner surface where the stiffening rod does not overlap the idler wheel path in the widthwise direction of the track over (ii) a dimension of the stiffening rod in a thickness direction of the track where the stiffening rod does not overlap the idler wheel path in the widthwise direction of the track is at least 0.1.

55. The track of claim 51, wherein a ratio of (i) a difference between the thickness of the elastomeric material between the inner surface and the surface of the stiffening rod facing the inner surface where the stiffening rod overlaps the idler wheel path in the widthwise direction of the track and the thickness of the elastomeric material between the inner surface and the surface of the stiffening rod facing the inner surface where the stiffening rod does not overlap the idler wheel path in the widthwise direction of the track over (ii) a dimension of the stiffening rod in a thickness direction of the track where the stiffening rod does not overlap the idler wheel path in the widthwise direction of the track is at least 0.15.

56. The track of claim 51, wherein a ratio of (i) a difference between the thickness of the elastomeric material between the inner surface and the surface of the stiffening rod facing the inner surface where the stiffening rod overlaps the idler wheel path in the widthwise direction of the track and the thickness of the elastomeric material between the inner surface and the surface of the stiffening rod facing the inner surface where the stiffening rod does not overlap the idler wheel path in the widthwise direction of the track over (ii) a dimension of the stiffening rod in a thickness direction of the track where the stiffening rod does not overlap the idler wheel path in the widthwise direction of the track is at least 0.2.

57. The track of claim 51, wherein a difference between the thickness of the elastomeric material between the inner surface and the surface of the stiffening rod facing the inner surface where the stiffening rod overlaps the idler wheel path in the widthwise direction of the track and the thickness of the elastomeric material between the inner surface and the surface of the stiffening rod facing the inner surface where the stiffening rod does not overlap the idler wheel path in the widthwise direction of the track is at least 0.03 inches.

58. The track of claim 51, wherein a difference between the thickness of the elastomeric material between the inner surface and the surface of the stiffening rod facing the inner surface where the stiffening rod overlaps the idler wheel path in the widthwise direction of the track and the thickness of the elastomeric material between the inner surface and the surface of the stiffening rod facing the inner surface where the stiffening rod does not overlap the idler wheel path in the widthwise direction of the track is at least 0.045 inches.

59. The track of claim 51, wherein a difference between the thickness of the elastomeric material between the inner surface and the surface of the stiffening rod facing the inner surface where the stiffening rod overlaps the idler wheel path in the widthwise direction of the track and the thickness of the elastomeric material between the inner surface and the surface of the stiffening rod facing the inner surface where the stiffening rod does not overlap the idler wheel path in the widthwise direction of the track is at least 0.06 inches.

60. The track of claim 50, wherein the surface of the stiffening rod facing the inner surface comprises a recess.

61. The track of claim 60, wherein a depth of the recess is at least 0.03 inches.

62. The track of claim 60, wherein a depth of the recess is at least 0.045 inches.

63. The track of claim 60, wherein a depth of the recess is at least 0.06 inches.

64. The track of claim 60, wherein a ratio of a depth of the recess over a thickness of the stiffening rod in the thickness direction of the track is at least 0.1.

65. The track of claim 60, wherein a ratio of a depth of the recess over a thickness of the stiffening rod in the thickness direction of the track is at least 0.15.

66. The track of claim 60, wherein a ratio of a depth of the recess over a thickness of the stiffening rod in the thickness direction of the track is at least 0.2.

67. The track of claim 51, wherein a longitudinal end portion of the stiffening rod overlaps the idler wheel path in the widthwise direction of the track.

68. The track of claim 53, wherein a first longitudinal end portion of the stiffening rod overlaps the first idler wheel path in the widthwise direction of the track and a second longitudinal end portion of the stiffening rod overlaps the second idler wheel path in the widthwise direction of the track.

69. The track of claim 50, comprising a plurality of reinforcing cables extending generally in the longitudinal direction of the track.

70. The track of claim 69, wherein the reinforcing cables are located between the stiffening rods and the inner surface in a thickness direction of the track.

71. The track of claim 69, wherein the reinforcing cables are located between the stiffening rods and the ground-engaging outer surface in a thickness direction of the track.

72. The track of claim 50, comprising a plurality of drive/guide projections projecting from the inner surface.

73. The track of claim 72, wherein the drive/guide projections are configured for engaging the drive wheel to drive the track.

74. The track of claim 50, wherein a thickness of the track from the inner surface to the ground-engaging outer surface is no more than 0.25 inches.

75. The track of claim 50, wherein the vehicle is a snowmobile and the track is a snowmobile track.

76. A track for traction of a vehicle, the track being mountable around a track-engaging assembly that comprises a drive wheel for driving the track and an idler wheel for contacting the track, the track comprising elastomeric material to be flexible around the track-engaging assembly, the track comprising:

a ground-engaging outer surface for engaging the ground; and

a plurality of traction projections projecting from the ground-engaging outer surface;

wherein a shock absorbency of the track is greater where the idler wheel path is located in a widthwise direction of the track than where the idler wheel path is not located in the widthwise direction of the track.