Snowmobile - Patent Review 5660245

What is claimed is:

1. A snowmobile comprised of a frame assembly including a pair of spaced-apart side portions suspended from a drive belt, an internal combustion engine disposed at the front of said frame assembly and supported with its output shaft extending generally transversely relative to said side portions, a belt drive shaft engaged with and driving said drive belt, an intermediate shaft driven by said engine output shaft by first transmission means and driving said drive belt shaft by second transmission means, said engine output shaft, said drive belt shaft, and said intermediate shaft being rotatably journalled about parallel transversely extending are, at least one of said transmission means being positioned substantially entirely within the lateral confines of said frame portions, a seat carried by said frame assembly in proximity to and to the rear of said internal combustion engine, and a pair of foot rests carried by said frame means on opposite sides thereof to accommodate the feet of a rider seated upon said seat, one of said foot rests being juxtaposed transversely outwardly of said one transmission means and transmission casing means carried and formed by the one frame side portion and containing the at least one transmission means.

2. A snowmobile as in claim 1, wherein the pair of spaced-apart side portions of the frame assembly comprise a pair of front frame side plates affixed to a generally inverted U-shaped rear frame portion carrying the seat and overlying the drive belt and further including at least one cross frame member extending between said front frame side plates and defining with said front frame side plates a cradle assembly receiving the engine.

3. A snowmobile as in claim 2, wherein one front frame side portion has an opening receiving and forming the transmission casing means.

4. A snowmobile as in claim 3, wherein the opening receives a first transmission case member containing the at least one transmission means and extending inwardly from the one frame side portion and a cover affixed to said transmission case member.

5. A snowmobile as in claim 4, wherein the transmission case cover is readily removable.

6. A snowmobile as in claim 5, wherein the at least one transmission means is disposed between the feet of a rider seated on the seat and with his feet on the foot rests.

7. A snowmobile as in claim 6, wherein the drive belt has a drive element thereon driven by the at least one transmission means and which is disposed at the same vertical height as the foot rests.

8. A snowmobile as in claim 7, wherein the at least one transmission means comprises the second transmission means.

9. A snowmobile as in claim 7, wherein the other transmission means is disposed forwardly of the rider's feet.

10. A snowmobile as in claim 9, wherein the one transmission comprises the second transmission means.

11. A snowmobile as in claim 1, further including a pair of dirigible front skis carried by the frame assembly and steering assembly carried by said frame assembly forwardly of said seat for operation by an operator seated upon said seat for steering said front skis, said steering means including a steering shaft rotatable about an axis that is upwardly inclined in a rearward direction and which passes over the engine.

12. A snowmobile as in claim 11, wherein the pair of spaced-apart side portions of the frame assembly comprise a pair of front frame side plates affixed to a generally inverted U-shaped rear frame portion carrying the seat and overlying the drive belt and further including at least one cross frame member extending between said front frame side plates and defining with said front frame side plates a cradle assembly receiving the engine.

13. A snowmobile as in claim 12, wherein one front frame side plate has an opening receiving the second transmission means.

14. A snowmobile as in claim 13, wherein the opening receives a first transmission case member containing the second transmission means and extending inwardly from the one front frame side plate and a cover affixed to said transmission case member.

15. A snowmobile as in claim 14, further including bearing means carried by the cross frame member for journaling the steering shaft.

16. A snowmobile as in claim 11, wherein the engine has at least one forwardly facing exhaust poet and an exhaust manifold for discharging exhaust gases from said exhaust port to the atmosphere comprising a first portion extending forwardly from the exhaust port, a second portion extending rearwardly and to one side of the engine, and a re-entrant portion interconnecting said first and said second portions of said exhaust manifold and defining a space forwardly of the engine and through which the steering shaft passes.

17. A snowmobile as in claim 16, wherein the engine is disposed in offset relationship toward one side of the frame assembly with the second transmission means being disposed on the other side of the frame assembly.

18. A snowmobile as in claim 17, wherein the exhaust gases are discharged from the exhaust manifold on the other side of the frame assembly.

19. A snowmobile as in claim 16, wherein the engine further has a rearwardly extending induction system including an air inlet device for drawing atmospheric air and a fuel tank carried by said frame means and having a generally L-shaped configuration in top plan view with a long leg extending along the rear of the air inlet device and toward the other side of the frame assembly and a short leg extending along said other side of said frame assembly from said long leg forwardly.

20. A snowmobile as in claim 19, wherein the fuel tank is disposed forwardly of the seat, and the fuel tank and induction system are disposed substantially above the drive belt.

21. A snowmobile as in claim 20, wherein the engine is water cooled and further including a heat exchanger disposed beneath the frame assembly and forwardly of the drive belt for dissipating heat from the coolant of the engine.

22. A snowmobile as in claim 21, wherein the heat exchanger has a first generally angularly inclined vertically extending portion, which terminates at a horizontally extending portion disposed beneath the frame assembly.

23. A frame assembly for a snowmobile comprised of a first member comprised of a pair of side portions and a top portion having a generally inverted U-shaped cross section adapted to overlie a drive belt, a pair of front side plates affixed to the forward ends of said side portions and extending forwardly therefrom for defining a cradle adapted to receive an internal combustion engine for powering the snowmobile and at least one cross member affixed to and spanning said front side plates.

24. A frame assembly for a snowmobile as in claim 23, wherein the side plates have a generally C-shaped configuration in side elevation and wherein the cross-member extends across at least one leg of each of the C-shaped configurations.

25. A frame assembly for a snowmobile as claim 24, further including a second cross-member extending transversely across the other open legs of the side plates.

26. A frame assembly for a snowmobile as claim 25, further including a sheet metal member affixed to the cross-members and extending between the side plates to form a lower surface of the cradle.

27. A frame assembly for a snowmobile as in claim 26, wherein the engine is supported on a pair of sub-frames affixed to the side plates adjacent the cross-meters.

28. A frame assembly for a snowmobile as in claim 23, further including transmission means for driving the drive belt from the engine mounted in the frame assembly.

29. A frame assembly for a snowmobile as in claim 28, wherein the transmission is contained within a transmission case affixed to the frame assembly.

30. A frame assembly for a snowmobile as in claim 29, wherein one front frame side plates has an opening receiving the transmission case.

31. A frame assembly for a snowmobile as in claim 30, wherein the opening receives a first transmission case member containing the transmission means and extending inwardly from the one front frame member and a cover affixed to said transmission case member.

32. A frame assembly for a snowmobile as in claim 23, further including suspension means for suspending a pair of dirigible front skis from the side plates and means for steering said front skis including a steering shaft journalled by the cross-member.

33. A frame assembly for a snowmobile as in claim 32, including a pair of cross-braces extending between the upper and lower ends of each of the side plates for providing structural reinforcing therefore.

34. A frame assembly for a snowmobile as in claim 32, wherein the side plates have a generally C-shaped configuration in side elevation and wherein the cross-member extends across at least one leg of each one of the C-shaped portions.

35. A frame assembly for a snowmobile as in claim 34, further including a second cross-member extending transversely across the other open legs of the side plates.

36. A frame assembly for a snowmobile as in claim 35, further including a pair of cross-braces extending between the legs of the respective side plates for offering further structural reinforcing.

37. A snowmobile comprised of frame means, a drive belt suspended by said frame means, an engine supported by said frame means, transmission means for driving said drive belt from said engine, a seat carried by said frame means behind said engine and above said drive belt, a pair of dirigible front skis carried by said frame means, and steering means carried by said frame means forwardly of said seat for operation by an operator seated upon said seat for steering of said front skis, said steering means including a steering shaft rotatable about an axis that is upwardly inclined in a rearward direction and that passes over said engine, said engine having at least one forwardly facing exhaust port and an exhaust manifold for discharging exhaust gases from said exhaust port to the atmosphere comprising a first portion extending forwardly from the exhaust port, a second portion extending rearwardly and to one side of the engine, and a re-entrant portion in connecting said first and said second portions of said exhaust minifold and defining a space forwardly of the engine and through which said steering shaft passes.

38. A snowmobile comprised of frame means as in claim 37, wherein the frame means includes a pair of generally C-shaped transversely spaced apart front side plates defining a cradle supporting the engine.

39. A snowmobile comprised of frame means as in claim 38, further including at least one cross member extending transversely across the side plates and providing reinforcing therefor at one of the legs thereof.

40. A snowmobile comprised of frame means as in claim 39, further including a second cross-member extending transversely across the other legs of the side plates.

41. A snowmobile comprised of frame means as in claim 40, further including a sheet metal member affixed to the cross-members and extending between the side plates to form a lower surface of the cradle.

42. A snowmobile comprised of frame means as in claim 41, wherein the engine is supported on a pair of sub-frames affixed to the side plates adjacent the cross-members.

43. A snowmobile comprised of frame means as in claim 37, wherein the engine is offset transversely to one side of the frame means.

44. A snowmobile comprised of frame means as in claim 37, wherein the engine further has a rearwardly extending induction system including an air inlet device for drawing atmospheric air and a fuel tank carried by said frame means and having a generally L-shaped configuration in top plan view with a long leg extending along the rear of the air inlet device and across the frame assembly and a short leg extending from said long leg forwardly.

45. A snowmobile comprised of frame means as in claim 44, wherein the fuel tank is disposed forwardly of the seat, and the fuel tank and induction system are disposed substantially above the drive belt.

46. A snowmobile comprised of frame means as in claim 45, wherein the engine is water cooled and further including a heat exchanger disposed beneath the frame assembly and forwardly of the drive belt for dissipating heat from the coolant of the engine.

47. A snowmobile comprised of frame means as in claim 46, wherein the heat exchanger has a first generally angularly inclined vertically extending portion, which terminates at a horizontally extending portion disposed beneath the frame assembly.

48. A snowmobile comprised of frame means, a drive belt suspended by said frame means, an engine supported by said frame means, transmission means driving said drive belt from said engine, a seat carried by said frame means behind said engine and above said drive belt, a pair of dirigible front skis carried by said frame means, said engine having exhaust port means on one side of said engine, an exhaust system for discharging exhaust gases from said exhaust port means to the atmosphere comprising a manifold having a first portion extending from said exhaust port means away from said one side of said engine, a second portion extending along one end of said engine and connected to said first portion by a re-entrant portion to define a generally U shape in top plan view, and steering means carried by said frame means forwardly of said seat for operation by an operator seated upon said seat for steering of said front skis, said steering means including a steering shaft rotatable about an axis that extends between said one side of said engine and said re-entrant portion.

49. A snowmobile comprised of frame means as in claim 48, wherein frame means comprises a pair of side plates having a generally C-shaped configuration in side elevation and wherein a cross-member extends across at least one leg of one of the C-shaped portions.

50. A snowmobile comprised of frame means as in claim 49, further including a second cross-member extending transversely across the other legs of the side plates.

51. A snowmobile comprised of frame means as in claim 50, further including a sheet metal member affixed to the cross-members and extending between the side plates to form a lower surface of the cradle.

52. A snowmobile comprised of frame means as in claim 51, wherein the engine is supported on a pair of sub-frames affixed to the side plates adjacent the cross-members.

53. A snowmobile comprised of frame means as in claim 48, wherein the engine further has a rearwardly extending induction system including an air inlet device for drawing atmospheric air and a fuel tank carried by said frame means and having a generally L-shaped configuration in top plan view with a long leg extending along the rear of the air inlet device and across and a short leg extending from said long leg forwardly.

54. A snowmobile comprised of frame means as in claim 53, wherein the fuel tank is disposed forwardly of the seat, and the fuel tank and induction system are disposed substantially above the drive belt.

55. A snowmobile comprised of frame means as in claim 54, wherein the engine is water cooled and further including a heat exchanger disposed beneath the frame assembly and forwardly of the drive belt for dissipating heat from the coolant of the engine.

56. A snowmobile comprised of frame means as in claim 55, wherein the heat exchanger has a first generally angularly inclined vertically extending portion, which terminates at a horizontally extending portion disposed beneath the frame assembly.

57. A snowmobile comprised of frame means, a drive belt suspended by said frame means, an engine supported by said frame means, transmission means driving said drive belt from said engine, a seat carried by said frame means behind said engine and above said drive belt, a pair of dirigible front skis carried by said frame means, and steering means carried by said frame means forwardly of said seat for operation by an operator seated upon said seat for steering of said front skis, said engine being formed with intake port means on one side thereof, an induction system affixed to said one side of said engine for delivering at least an air charge thereto and including an air inlet device for inducting atmospheric air, and a fuel tank carried by said frame means for supplying fuel to said engine for its operation, said fuel tank having a generally L-shaped configuration in top plan view comprised of a first long leg section extending along said one side of said engine contiguous to said air inlet device and a second short leg extending from one end of said first leg toward said one side of said engine and along and adjacent to one side of said induction system and said air inlet device.

Description Submit all comments and votes

BACKGROUND OF THE INVENTION

This invention relates to a snowmobile, and more particularly, to an improved drive and frame arrangement for a snowmobile.

Conventionally, snowmobiles have a frame assembly that supports, at the forward portion thereof, an internal combustion engine and a transmission that drives a drive belt positioned beneath the frame assembly and upon which the frame assembly is supported. A seat is carried by the frame assembly and generally overlies the drive belt. A pair of front skis are also carried by the frame assembly and are dirigibly supported for steering by a rider seated on the seat.

The drive belt generally is quite wide so as to improve stability and the transmission of power to the ground so as to propel the snowmobile. Of course, this means that the transmission for the drive belt must be disposed at a side of the drive belt and this driving transmission is driven from the engine in any of a variety of fashions. The rider, as is typical with this type of vehicle, is seated on the seat in straddle fashion and thus must have a place to position his legs. With the conventional types of drive constructions previously employed, the rider's legs must be splayed quite widely if they are to be disposed on opposite sides of the drive belt and the transmission that drives it. In order to avoid such uncomfortable seating positions, it has been the practice to move the seat rearwardly so that the rider's legs will be disposed behind the transmission driving the drive belt. This gives rise to not only a great length for the snowmobile, but also does not provide the desired balance or handling.

It is, therefore, a principal object of this invention to provide an improved snowmobile drive assembly that permits a more compact arrangement and affords comfortable seating.

It is a further object of this invention to provide a transmission assembly for a snowmobile that cab be positioned in a compact nature and permit the rider's feet to be placed outside of it without being unduly splayed.

It is a further object of this invention to provide an improved and compact drive assembly for a snowmobile.

Obviously, the frame assembly must support the engine and also accommodate the transmission. Conventionally, the frame assemblies include a pair of side members and the rider places his feet on footrests disposed outwardly of these side members. Because of the fact that the transmission assembly that drives the drive belt must be disposed at one side of the drive belt and outwardly therefor, it has heretofore been the practice to provide this transmission on the outside of the frame. This requires the rearward positioning of the rider and the other problems as aforenoted.

It is, therefore, a still further object of this invention to provide an improved frame assembly for a snowmobile that permits a compact assembly and permits a forwardly positioned rider.

It is a further object of this invention to provide an improved frame assembly for a snowmobile wherein the frame side members form, at least in part, the transmission case for the drive belt transmission.

As has been noted, the snowmobile typically employs a pair of front skis that are steered by a steering mechanism operated by the rider seated on the seat. This steering mechanism includes a steering column that is rotatably supported by the frame assembly and which generally is inclined upwardly and rearwardly from its forward connection to the steering skis. As a result of this disposition of the steering column, it has heretofore been the practice to position the engine either forwardly and/or above the steering column. This gives rise to added length to the snowmobile and also raises the center of gravity, which is not particularly desirable from a handling standpoint and from a stability standpoint.

It is, therefore, a still further object of this invention to provide an improved and compact steering arrangement for a snowmobile.

It is a further object of this invention to provide a steering arrangement for a snowmobile but permits the engine to be mounted low in the frame and thus maintain a low center of gravity.

The aforenoted types of steering constructions in which the steering column passes beneath and to the rear of the engine also causes the engine and a major portion of the transmission to be forwardly located. This tends to add to the weight on the front skis and reduce the amount of weight concentrated on the drive belt. As a result, traction can be decreased with this type of construction.

It is, therefore, a still further object of this invention to provide an improved engine and steering arrangement for a snowmobile that permits the engine to be located rearwardly and more over the drive belt than previous types of construction.

It has already been noted that the drive belt of a snowmobile is driven by a transmission from the engine. The drive belt transmission contains a drive belt drive shaft carrying a number of drive belt driving members that are engaged with the forward inner portion of the drive belt for driving it. This shaft obviously rotates about a transversely extending axis, and it has been the normal practice in snowmobiles to mount the engine so that its output shaft also rotates about a transversely extending axis. This means that with multiple cylinder engines that the exhaust manifold for the engine will also extend transversely. As a result, the exhaust system must reroute the exhaust gases from a transverse direction to a position wherein the exhaust gases can be discharged to the atmosphere and generally rearwardly of the engine. In other words, the exhaust system for the engine also extends the length of the engine assembly, either in a forward or rearward direction. This further compromises the location for the steering column.

It is, therefore, a still further object of this invention to provide an improved steering and engine arrangement for a snowmobile that permits a compact assembly.

It is a further object of this invention to provide an exhaust system and steering arrangement for a snowmobile wherein the steering column may pass between a portion of the exhaust system and the engine to occupy otherwise dead space and afford a compact arrangement.

Attendant to the transverse positioning of the engine in the snowmobile is also the requirement that the induction system extend either forwardly or rearwardly from the engine. This further complicates the layout of components of the snowmobile and can result in excess forward weight bias and added length for the snowmobile. As noted above, both of these features are relatively undesirable.

It is a still further object of this invention to provide an improved compact snowmobile arrangement that incorporates an induction system that can be interrelated to other components to afford a compact construction without unduly affecting the center of gravity.

It is a further object of this invention to provide an improved fuel tank and induction system layout for the driving power unit of a snowmobile.

SUMMARY OF THE INVENTION

A first feature of this invention is adapted to be embodied in a snowmobile that is comprised of a frame assembly that includes a pair of spaced-apart side portions that are suspended from a drive belt. An internal combustion engine is disposed at the front of the frame assembly and is supported with its output shaft extending generally transversely relative to the frame side portion. A belt drive shaft is engaged with and drives the drive belt. An intermediate shaft is driven by the engine output shaft by first transmission means, and second transmission means drive the belt drive shaft from the intermediate shaft. The engine output shaft, belt drive shaft, and intermediate shaft all rotate about parallel, transversely extending axes. At least one of the transmission means is positioned substantially entirely within the lateral confines of the frame side portion. A seat is carried by the frame means in proximity to and to the rear of the internal combustion engine. A pair of foot rests are carried by the frame means on opposite sides thereof and positioned to accommodate the feet of a rider seated upon the seat. At least one of the feet rests is spaced transversely outwardly of the one transmission means.

Another feature of the invention is adapted to be embodied in a frame assembly for a snowmobile that is comprised of a first section comprised of a pair of side portions and a top portion having a generally inverted U-shaped cross section adapted to overlie a drive belt. A pair of side members are affixed at the forward ends of the side portions and extend forwardly therefrom for defining a cradle adapted to receive an internal combustion engine for powering the snowmobile. At least one cross member is affixed to and spans the side members.

Still additional features of the invention are adapted to be embodied in a snowmobile that is comprised of frame means, a drive belt suspended by the frame means, and an engine supported by the frame means. Transmission means drive the drive belt from the engine. A seat is carried by the frame means behind the engine and above the drive belt. A pair of dirigible front skis is carried by the frame means.

In accordance with one of these additional features of the invention, steering means are carried by the frame means forwardly of the seat for operation by an operator seated upon the seat for steering of the front skis. The steering means includes a steering shaft that is rotatable about an axis that is upwardly inclined in a rearward direction and that passes over the engine.

In accordance with another of these additional features, the engine has exhaust port means on one side of the engine and an exhaust system is provided for discharging exhaust gases from the exhaust port means to the atmosphere. This exhaust system includes a manifold having a first portion extending away from the one side of the engine, a second portion extending along one end of the engine, and connected to the first portion by a re-entrant portion to define a generally U-shape in top plan view. Steering means are carried by the frame means forwardly of the seat for operation by an operator seated upon the seat for steering of the front skis. The steering means includes a steering shaft rotatable about an axis that extends between the one side of the engine and the re-entrant portion of the exhaust manifold.

In accordance with the final additional feature of the invention, the engine is formed with intake port means on one side thereof, and an induction system is affixed to this one side of the engine for delivering at least an air charge to the intake port means. This induction system includes an air inlet device for drawing atmospheric air. A fuel tank is carried by the frame means for supplying fuel to the engine for its operation. This fuel tank has a generally L-shaped configuration in top plan view and is comprised of a first long-leg section that extends along one side of the engine contiguous to the air inlet device and a second short leg extending from one end of the first long leg towards the one side of the engine and along and offset to one side of the induction system and the air inlet device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view of a snowmobile constructed in accordance with an embodiment of the invention, with the body assembly shown in phantom and with portions of the frame assembly shown in phantom so as to more clearly show the construction. In addition, certain portions are broken away.

FIG. 2 is a top plan view of the snowmobile with the same portions shown in phantom so as to more clearly show the relationship of the steering engine and transmission arrangement.

FIG. 3 is an enlarged front elevational view of the snowmobile with portions broken away and shown in section, illustrating the same components as shown in solid lines in the other figures.

FIG. 4 is an enlarged side elevational view of the forward portion of the snowmobile with additional portions shown in cross section and the transmission removed so as to more clearly show the arrangement for mounting the engine and body.

FIG. 5 is an enlarged cross-sectional view showing a portion of the transmission mechanism, which is also shown in FIG. 3.

FIG. 6 is an enlarged top plan perspective view of the frame assembly with a portion broken away.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION

A snowmobile constructed in accordance with an embodiment of the invention is shown in the drawings and is identified generally by the reference numeral 11. The snowmobile 11 is comprised of a number of main components, including a frame assembly, indicated generally by the reference numeral 12, and which is shown in part in phantom in some of the figures. The frame assembly 12 is suspended on a drive belt 13 by means of a carriage assembly 14. A seat 15 is supported on the frame assembly 12 over the drive belt 13 and carriage assembly 14 and is sized to accommodate a single rider seated in straddle fashion, as is typical in snowmobile practice, with the rider being shown in some of the figures and identified by the reference numeral 16.

An internal combustion engine, indicated generally by the reference numeral 17, is carried by the frame 12 forwardly of the seat 15 in a manner that will be described. The engine 17 drives an intermediate shaft 18 by means of a first transmission, indicated generally by the reference numeral 19, and which is of the variable ratio type and which also includes a centrifugal clutch. The intermediate shaft 18, in turn, drives the drive belt 13 by a second transmission 21, which will also be described later in more detail.

A pair of front skis 22 are supported by a suspension system at the front of the frame assembly 12 and are dirigible for steering of the snowmobile 11. A handlebar assembly 23 is supported forwardly of the rider's seat 15 for steering of the skis 22 in a manner that will be described.

A fiberglass reinforced resinous plastic body 24 is mounted on the frame assembly 12 and has a windshield 25 that is disposed forwardly of the handlebar 23 for protection of the rider 16.

The frame assembly 12 will be now described in more detail by particular reference to FIG. 6. The frame assembly 12 is made up of a fabrication of a number of pieces of aluminum for light weight, although it is to be understood that other materials may be employed or certain portions of the frame assembly may be formed from other materials. Also, the manner of fabrication that is described is only typical, and other methods may be employed for forming the individual components of the frame assembly 12 or its sub-components.

The frame assembly 12 is comprised of a rear portion, indicated generally by the reference numeral 26, and which has a generally inverted U shape with a flat section 27 that tapers generally downwardly in a rearward direction and a pair of side pieces 28. The lower ends of the side pieces 28 are formed with outwardly extending flanges 29 that have their rigidity improved by forming rolled portions 31 at the outer periphery thereof. It should be noted that the side portions 28 have a generally triangular configuration in side elevation, while the cross-sectional shape of the frame portion 26 has an inverted U shape, with the outward legs 29 extending outwardly from the lower ends thereof.

A pair of side plates 32 and 33, which may be formed as stampings, forgings, or the like and which have a generally C-shaped opening at the front end thereof, are affixed in a suitable manner to the front portion of the rear frame member 26. The side plates 32 and 33 may be formed with flanges 34 that overlie the upper surface 26 and lower flanges 35 that overlie the flanges 29 of the frame member 26 so as to add rigidity to the construction. These side members 32 and 33 may be fixed to the frame member 26 by riveting, welding, or the like.

A pair of rectangularly shaped cross members 36 and 37 are affixed between the side plates 32 and 33 and add to their rigidity. These cross members 36 and 37 may be formed as extrusions or the like, also from aluminum alloy. The frame assembly further includes a support plate 38 that extends from the front of the frame member 26 between the side plates 32 and 33 and forwardly to the cross member 37 so as to form a cradle-like configuration in which the engine 17 is mounted in a manner that will be described. The side plate 33 is also formed with a side opening 39 so as to form a case for the transmission 21, as will also be described.

Referring now primarily to FIGS. 1-4, the engine 17 is, in the illustrated embodiment of the two-cylinder in-line type, which operates on a two-stroke crankcase compression principle. As is typical with snowmobile practice, the engine 17 is mounted in the frame assembly 12 so that its crankshaft 41 rotates about a transversely extending axis. In accordance with a feature of the invention, the engine 17 is mounted within the frame assembly 12 so as to be offset to one side of the frame assembly 12, specifically toward the left-hand side in the illustrated embodiment. Although the invention is described in conjunction with a two-cylinder engine operating on a two-stroke crankcase compression principle, it will be obvious to those skilled in the art that certain facets of the invention may be employed with engines of other types. However, the offsetting of the engine 17 to one side of the frame assembly 12 permits the placement of the transmissions for driving the drive belt 13 in the manner to be described.

The engine 17 is also disposed so that its exhaust ports face forwardly, and these exhaust ports deliver the exhaust gases to an exhaust system, indicated generally by the reference numeral 42. This exhaust system includes a manifold 43 having a Y-shaped inlet end that extends to a forwardly extending collector portion 44. This forwardly extending collector portion is disposed axially forwardly of the frame assembly 12, for a purpose to be described, and then merges into a re-entrant or U-shaped section 45. The opposite end of the U-shaped section 45 is connected to an integral expansion chamber 46 that extends along one end of the engine on the right-hand side of the frame assembly 12. The exhaust gases are then introduced to a muffler 47 for silencing and discharge to the atmosphere. It should be noted that the muffler 47 is in essence placed at one side or end of the engine, considering its transverse disposition, and thus this permits a very compact assembly and maximum space utilization without interfering with the serviceability of the components.

An electrical generator, indicated generally by the reference numeral 48, is driven off of the right-hand side of the engine and is interposed between the engine 17 and a recoil starter 49. Again, this construction permits a compact assembly and yet full serviceability of the components.

The engine 17 is provided with an induction system that extends to the intake ports of the engine but rearwardly of the exhaust system 42. This induction system is indicated generally by the reference numeral 51 and includes an air inlet device 52 that draws atmospheric air from an area within the body 24 and forwardly of the legs of the r