SNOW BIKE

One embodiment of the improved snow bike described herein includes a frame. A track may be mounted at least partially rearward of the frame and a power source may be mounted above at least a substantial portion of the track. A centrifugal clutch may be mounted at least partially to the side of the power source and may extend laterally outward from the power source.

BACKGROUND

FIG.1depicts a snow bike10representative of snow bikes of the prior art. The snow bike10is provided with a frame12and a track assembly14attached rearward of the frame12and containing a track16. A fork18is attached to the front of the frame12, a ski20is attached to the bottom of the fork18, a seat24is attached at the top of the frame12, and an engine26is attached within the frame12and toward the front bottom of the frame12as is customary with modern motorcycles.

The depicted snow bike10utilizes a frame12taken from a motorcycle. The track assembly14is generally a kit provided by snow bike manufacturers and is mounted to the rear of the frame12in lieu of a swing arm and a rear tire (not shown.) The ski20is attached to the fork18in lieu of a front tire (not shown). Most snow bikes of the prior art are made using a standard motorcycle that is usually a high powered dirt bike, removing the wheels and swingarm and attaching the track assembly14and the ski20. The engine26is typically the stock engine from the motorcycle the snow bike10is made from.

The engine26drives a sprocket and chain as in a typical dirt bike. The chain is connected with a jack shaft, which typically contains a braking mechanism. Another chain extends from the jack shaft to a drive shaft and turns the drive shaft. The drive shaft has teeth that engage and turn the track. The snow bikes10of the prior art typically use a transmission28that is provided with the original motorcycle and is a standard transmission using a plurality of gears.

One problem with using the stock engine is that the engines from light weight motorcycles such as dirt bikes are limited in horse power and often have third of the power that a snowmobile might have. Turning a track through the snow is demanding on horse power, and many feel that current snow bikes lack speed and power compared to modern snowmobiles. Modifications can be made to the engines26, but current engine modifications are limited in the horsepower that is added and are generally considered to be of limited reliability.

SUMMARY

One embodiment of the improved snow bike described herein includes a frame. A track may be mounted at least partially rearward of the frame and a power source may be mounted above at least a substantial portion of the track. A centrifugal clutch may be mounted at least partially to the side of the power source and may extend laterally outward from the power source.

A clutch guard may protect the centrifugal clutch and may have a hardened outer wall at least partially surrounding a periphery of the centrifugal clutch. The clutch guard may have an open side directed toward the frame in order to provide simultaneous protection to a rider and cooling of the centrifugal clutch.

A stock fuel tank may be mounted forward of the seat, and a second fuel tank may be mounted below the stock fuel tank in the frame in a recess originally adapted to a power source. In certain embodiments, the stock fuel tank and the lower mounted fuel tank are in fluid communication with each other to provide continuous fuel to the power source. A jack shaft may be in rotational connection to the power source for turning a track and may be provided with a centrally located sprocket for receiving a chain extending to a drive shaft that drives the track. A brake component may be disposed at one end of the jack shaft, and a secondary drive clutch of a centrifugal clutch system may be disposed at a second end of the jack shaft.

The power source may be a snowmobile engine or an electric motor mounted above the track with an engine mounting plate, and the track may be carried by a track assembly. The engine mounting plate may connect the track assembly with stock mounting surfaces of the snowmobile engine without requiring modification of the mounting surfaces, including stock apertures on the engine for receiving mounting bolts.

A cooling system for cooling the power source may be provided and may include a radiator and a heat exchanger in fluid communication with the radiator. A water jacket on the power source may be in fluid communication with the radiator such that fluid is pumped from the heat exchanger to the radiator and then to the water jacket in order to cool the power source. The snowmobile engine may be in gaseous communication with an exhaust pipe that is mounted forward of the snowmobile engine and rearward of the fuel tank. In this embodiment, the carburetor or fuel injectors are mounted rearward of the engine.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In order to overcome some or all of the limitations of the prior art, embodiments of the snow bike200are shown inFIG.2. Depicted therein is a snow bike200having a frame212. The frame212may be any frame capable of carrying a seat224and other components of the snow bike200. In the depicted embodiment, the frame212is taken from an existing motorcycle. A radiator248is mounted to the front of the frame212. A track assembly214is mounted to the rear of the frame212in lieu of a swing arm and a rear tire (not shown.) A ski220is attached to a fork218in lieu of a front tire (not shown). While the snow bike200may all be made in a common production process, in the depicted embodiment, the snow bike200is made using a standard dirt bike motorcycle, removing the wheels and swingarm, and attaching the track assembly214and the ski220.

A fuel tank228is shown located in a standard position for a dirt bike and may be mounted to the frame212. In the depicted embodiment, a second tank230is also shown located below the fuel tank228within a location of the frame212that in prior art snow bikes normally contains an engine. The snow bike200may be provided with one or both of the fuel tanks228,230.

An engine226is mounted substantially outside of the frame212and to the rear of the frame. Of course, portions of the engine226may remain within the frame226. The engine226is shown mounted to the top of the track assembly214. The engine226is in the depicted embodiment a snowmobile engine with a centrifugal clutch310(shown inFIG.3). The engine226is one type of power source that may be used with embodiments herein. The engine226may be, for example, a single or multiple cylinder two or four stroke engine. In the depicted embodiment, the engine226is a Yamaha700SX snowmobile engine with a centrifugal clutch310.

The power source may also be an electric motor (not shown) and may utilize batteries that may be stored within the frame212in the location where the fuel tank228is shown.

The engine226is shown mounted centrally above the track assembly214and is shown with the intake232of the engine to the rear of the engine226and the exhaust234toward the front of the engine226. Of course, the engine226could be reversed in direction and could also be mounted sidewise with the intake232and exhaust234each located to one side of the snow bike200.

Also shown inFIG.2are a set of footpegs236located to the bottom of the frame. The footpegs236in the depicted embodiment are located below the seat and take the weight of the rider when the rider's feet are placed upon the footpegs236. A rider normally occupies a riding area by sitting on the seat224with the rider's legs extending downward to the footpegs236. The rider's legs typically remain in the riding area between the seat224and the foot pegs236. The engine226is, in the depicted embodiment, located substantially behind the area between the seat224and footpegs236where the riders legs will be located. In this manner, the engine226does not interfere with the riding area.

The engine226may be started manually or with a battery. In the depicted embodiment, a pull rope with a handle238is used to start the engine226. The pull rope and handle238are shown to the right side of the engine226, but could be located in other locations on the engine226.

Also shown inFIG.2are the suspension240, a front drive sprocket244, and a rear drive coaster246. In the depicted embodiment, the track assembly214is provided by a snow bike kit manufacturer. The track assembly214in the embodiment shown is a Timbersled Arro manufactured by Timbersled Products, Inc. of Sandpoint Idaho. The track assembly214is attached fixedly to the swingarm and shock mount (not shown) in a manner that is well known in the art. The track assembly214contains its own suspension240and does not utilize the suspension that comes stock on a motorcycle, though in some embodiments, one or more shocks are mounted between the swingarm assembly214and the frame212in a manner well known in the art. The ski220is also in this embodiment manufactured by Timbersled Products, Inc.

Referring now toFIG.3, shown therein is the centrifugal clutch310that is mounted to the left side of the engine226. The centrifugal clutch310is shown with a drive (or primary) clutch312and a driven (or secondary) clutch314. The drive clutch312is powered by the engine226and turns a belt316that turns the driven clutch314. The centrifugal clutch310protrudes outward from the engine226and is in one embodiment located entirely in an area that is behind the footpegs236and while partially under the seat224, generally to the rear of the seat224. Thus, while the centrifugal clutch310protrudes outward from the snow bike200, it does not substantially protrude into the riding area that is in use occupied by the leg of a rider.

The driven clutch314is connected with and turns a chain316(ofFIGS.4and5) and is shown located under a chain case318. The chain316drives the drive wheels242which engage with and turn the track216.

FIG.4is a partially exploded view showing the track assembly214with the engine226mounted at the top thereof. The track assembly214is shown disconnected from the frame12of the snow bike200in order to more clearly show the components of the engine226and the centrifugal clutch310. The engine226is shown with the intake232to the rear and the exhaust234to the front. The pull rope and handle238are shown to the right side of the engine226.

A motor mount plate410is shown disposed between the track assembly214and the engine226. The motor mount plate410is in one embodiment provided with holes, brackets, or other mechanisms to attach both to the track assembly214and the engine226. In one embodiment, the motor mount plate410is configured with mounting mechanisms610(shown inFIG.6) that bolt to the stock engine mounting points612of the engine226. Thus, a stock engine may be mounted directly to the snow bike200without requiring modifications to the engine226or the engine mounting points612.

Also shown inFIG.4is a jack shaft412, that typically contains a braking mechanism414. Another chain extends from the jack shaft412and extends to and turns a drive shaft448(ofFIG.5). The drive shaft448has a sprocket244with extending protrusions or “teeth” that engage and turn the track216.

FIG.5shows this arrangement in greater detail. The jack shaft412is mounted to the track assembly214and has an interior end with splines452that receive a braking component shown as a disk414of the braking system. In a central portion of the jack shaft412is shown a sprocket454that drives the chain316. To the exterior of the jack shaft412and shown on the left side of the track assembly214are splines450for receiving the driven clutch314(shown inFIG.4). The chain316drives a sprocket456of a drive shaft448which turns the drive sprocket244which turns the track216.

FIG.6is a zoomed in view ofFIG.4and shows the engine mounting points612connected with the mounting mechanisms610of the motor mount plate410. Also shown are bolts614passing through the track assembly214and the motor mount plate410, securing the motor mount plate410to the track assembly214. Of course, other mechanisms could be used to mount the power source to the track assembly, and the power source need not necessarily be mounted to the track assembly214, and could instead be mounted entirely or partially to the frame212.

FIG.7is the partially exploded view ofFIG.4also showing a clutch cover710.FIG.8shows the clutch cover710from the opposite side. In the depicted embodiment, the clutch cover710partially covers the clutch assembly310and protects the rider's leg from any debris that may projected from the clutch, such as, for example, in instances where the belt316wears and loses integrity.

The clutch cover710is shown provided with a hardened wall712circumnavigating both the drive clutch312and the driven clutch314. The hardened wall712may be made of any protective material, but in one embodiment is made of steel or aluminum. Carbon fiber is a further suitable material, given by way of example. A framework714may be provided in the external side of the clutch cover710and in the depicted embodiment supports a sheet716of breathable material that allows air to pass but prevents the passage of snow. The interior side718of the clutch cover710is left open in the depicted embodiment in order to allow greater passage of air in order to keep the centrifugal clutch310cool. In this manner, the centrifugal clutch310may be located at an exterior of the snow bike200and to the rear of the rider's leg, while simultaneously protecting the rider's leg and allowing cooling air to circulate around the centrifugal clutch310.

FIG.9shows a heat exchanger910mounted to an underside of a tunnel912of the track assembly214. The heat exchanger910is fluidly coupled with the radiator248and the water jacket916(also shown inFIGS.4,6,7, and8). The heat exchanger910is preferably located in a location such as the tunnel912in order for snow kicked up by the track216to be thrown onto the heat exchanger910thereby cooling the coolant being pumped through the heat exchanger910. In one embodiment, the heat exchanger910precools coolant that passes from the water jacket916of the engine226prior to passing through the radiator248. The order of cooling components could be reversed with the coolant flowing from the water jacket916to the radiator248and then to the heat exchanger910prior to returning to the water jacket916.

The snow bike200in certain embodiments overcomes a problem of the prior art of snow bikes needing more power by accommodating a higher horse power snowmobile engine226. The engine226may be driven by a centrifugal clutch310, allowing the rider to not have to shift and providing a smoother transfer of power between the power source and the track216. Locating the engine226(or other power source) behind the frame lightens the front end of the snow bike200and allows the track assembly in certain embodiments to carry the engine226, thus allowing a larger engine226to be used without interfering with a riding area of the rider.

The problem of the location of the centrifugal clutch316is solved by locating the engine behind the rider with the primary and secondary clutches312,314protruding outward. The clutch cover710simultaneously protects the rider's leg while allowing air to cool the centrifugal clutch316.