Abstract:
A personal winter vehicle has a frame which includes a front portion and a rear portion. Preferably, the front and rear portions of the frame can flex with respect to each other. An operator-controlled motivator for generating torque, such as a pedal crank, is mounted on the frame. A drive assembly is attached to the rear portion of the frame and is mechanically coupled to and receives torque from the motivator. The drive assembly preferably includes a drive wheel rotatably attached to the rear portion of the frame and coupled to the motivator via mechanical coupling, and a track disposed around part of the circumference of the drive wheel. The drive assembly also may include a guide wheel rotatably attached to the frame and disposed in front of the drive wheel. The track is also disposed around the guide wheel. The front of the vehicle may include a ski which is turnable by operation of handlebars. Alternatively, there may be provided a front wheel also having a track. Brakes are provided, preferably caliper brakes which retard the rotation of the drive wheel and, if provided, the front wheel.

Description:
RELATED APPLICATIONS 
     This application is a continuation-in-part application of U.S. patent application Ser. No. 09/255,889 filed Feb. 20, 1999 now abandoned and incorporates by reference all of the teachings thereof. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention generally relates to personal winter vehicles, and more specifically to a cycle that may be operated in snow and ice. 
     2. Description of Related Art 
     People frequently recreate in cold climates and in snowy conditions. In several types of recreational activities that take place in snowy or icy conditions, the individual rides up a mountain on a mechanical conveyance and then, at the summit of the mountain, slides down the snowy slopes of the mountain. Such activities include skiing, snowboarding, telemarking, and the like. In these types of activities, flat or uphill portions of the mountain reduce one&#39;s rate of travel and generally one&#39;s enjoyment of the activity. If one stops on a flat or uphill portion of the mountain, building up the momentum to overcome gravity and friction and begin travelling again (and especially to remain travelling) can be an arduous task. Cross-country skis are designed to allow a person to travel on flat portions of land, however they are not ideal for downhill portions of land. Similarly, downhill skis are typically only useful for travelling downhill and are less than desirable for flat portions of land. 
     People also like to recreate on bicycles. Some individuals have combined typical cold weather activities such as skiing and conventional bicycling in developing a “snow bike.” Examples of snow bikes are found in U.S. Pat. No. 2,633,365 to Cwynar et al., U.S. Pat. No. 3,561,783 to Ellett, U.S. Pat. No. 4,027,891 to Frame, and U.S. Pat. No. 4,059,168 to House, the teachings of which are herein incorporated by reference. 
     The Ellett and Frame devices are essentially bicycle frames with the wheels replaced with short skis. Neither provides any ability for a user to use force to propel the vehicle. The Ellett and Frame devices are limited to use on downhill slopes. Three companies, Brenter, Ludwig, and Vertex, currently market snow bikes of this nature. The user is intended to wear short skis on his or her feet while operating the snow bike for stability. 
     The Cwynar device is described as a “ski scooter” and is intended to be used by a standing individual. The user keeps one foot on the running board and pushes off the ground with the other foot in a manner similar to propelling a conventional scooter. Instead of wheels, the Cwynar device includes runners, one in the front and two in the rear. The use of one&#39;s foot to propel a wheeled scooter on ordinary ground is difficult enough; however, additional problems arise when using such a device on snow or ice. For example, the coefficient of friction between a person&#39;s foot and snow/ice is substantially smaller than that between a person&#39;s foot and a paved road; one could easily slip when trying to propel the device. Also, on snow that is not uniformly packed down, a person may step into a patch of snow that is deeper and more loosely packed than the person expected, resulting in the person losing his balance and falling from the scooter. 
     The House device converts a standard bicycle frame by adding skis and a fan on the rear of the frame. The motor-driven fan is intended to create sufficient thrust to propel a person across a snowy field. Because the pedals of the bicycle frame are no longer attached to any resistance-providing structure, a user cannot obtain much exercise benefit from use of this device. 
     Another device that enables a person to propel a personal vehicle over snow/ice was described in U.S. Pat. No. 551,442 to Korff, the teachings of which are herein incorporated by reference. Korff modified a standard bicycle frame by replacing the front wheel with a guide runner and by adding a rear runner behind it. The rear wheel was left in place and stud plates were placed around the circumference thereof. A user would pedal the device thus causing the rear wheel to turn. Because the wheel was provided with studs for better traction, and because the runners exhibit reduced coefficient of friction, the device would be propelled across snow/ice. However, even with the studs on the wheel, such a device will slip on ice because only a small portion of the wheel tread is in contact with the ice at any given moment. Moreover, no braking mechanism is provided. 
     All of the above devices suffer from several deficiencies. The Ellett and Frame devices do not allow a user any ability to use force to propel the vehicle. The Cwynar device is difficult to operate and unreliable owing to the non-uniform nature of snow and ice. The House device does not afford an individual any significant exercise. Moreover, much like a conventional snowmobile, the fan required to propel an average weight person is likely to be enormous, heavy, loud, and impractical. Further, none of the above-mentioned devices allow the user to brake or reduce speed in any safe manner. The user must also, in each device listed above, use the respective devices in a single mode only; no provision is made for increasing the mechanical advantage a person has for an inclined surface and/or decreasing the mechanical advantage when riding on downhill slopes. The prior devices also fail to teach a device capable of switching between a motorized or motor-assisted mode of operation and a manual mode. Also, none of the devices mentioned above are suitable for extremely arduous or difficult maneuvering at high speeds, in what is commonly referred to as “extreme sporting” events. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the invention to provide a personal winter vehicle that allow a user the ability to use force to propel the vehicle. 
     It is another object of the invention to provide a personal winter vehicle that is easy to operate on snow, ice, and other terrain of varying consistencies. 
     It is another object of the invention to provide a personal winter vehicle that affords the user significant exercise. 
     It is another object of the invention to provide a personal winter vehicle that enables the user to brake or reduce speed in a safe manner. 
     It is another object of the invention to provide a personal winter vehicle that allows a user to vary the mechanical advantage depending on personal preference, degree of incline or decline, or the like. 
     The above and other objects are fulfilled by the invention, which is a personal winter vehicle or snow cycle. The inventive snow cycle includes a frame, having a front portion and a rear portion, and an operator-controlled motivator for generating torque mounted on the frame. The motivator may be a pedal crank and pedals, a motor or engine, or a combination of the two. The snow cycle includes a drive assembly, preferably attached to the rear portion of the frame; the drive assembly is mechanically coupled to and receives torque from the motivator. The drive assembly includes a drive wheel rotatably attached to the rear portion of the frame and coupled to the motivator via mechanical coupling. The drive assembly also preferably includes a guide wheel rotatably attached to the frame and disposed in front of the drive wheel. A track is disposed around at least part of the circumferential rims of the drive and guide wheels engages the drive wheel and the ground. Torque created by the motivator is transmitted to the drive wheel via the mechanical coupling which rotates the drive wheel and moves the track and thereby propels the vehicle. The guide wheel is preferably connected to the rear portion of the frame at a position above ground level. That is, in the normal position of the cycle, the guide wheel does not contact the ground or does not contact the ground at the same level as the rear drive wheel. This configuration raises the leading portion of the track off the ground to allow for better maneuverability in the snow and easier braking. 
     The mechanical coupling preferably includes a middle gear mechanically interposed between the motivator and the drive wheel. The middle gear is preferably attached to the frame above and rearwardly of the motivator. A first chain belt engages the motivator and the middle gear, and a second chain belt engages the middle gear and the drive wheel. By disposing the middle gear above and forwardly of the drive wheel, gear-shifting structure may be incorporated into the snow cycle. On a conventional bicycle, the gear derailer and sprocket set is disposed next to the rear wheel. However, that design would be impractical on a snow cycle because the derailer would have a tendency to drag in the snow. Thus, the gear derailer has to be placed much higher on the frame of the cycle. One solution would be to use a much larger wheel; however, a bigger wheel dramatically increases the weight of the cycle in the rear of the vehicle. By providing a middle gear between the motivator and the rear drive wheel in the inventive “inverted V” configuration disclosed herein the invention raises the gearing well away from the snow without adding significant amounts of weight to the vehicle. 
     A shock absorber is preferably connected between the front portion and the rear portion of the frame. The shock absorber is flexible and allows relative movement between the front portion and the rear portion of the frame. When the shock absorber flexes when an operator turns, or brakes, the front and rear portions of the frame flex slightly away from each other, thus causing the guide wheel of the drive assembly to move closer to the ground, thereby placing more of the track in contact with the ground at a given time. This allows for increased traction during braking and turning. 
     The inventive snow cycle also includes a braking system wholly absent in conventional personal vehicles intended to be used in snow and ice. A brake is attached to the rear portion of the frame and is selectively frictionally engageable with the drive wheel. A brake controller is disposed on the front portion of the frame and is connected to the brake for selectively engaging the brake with the drive wheel to slow rotation of the drive wheel. Moreover, the invention also contemplates a front braking system. The front support preferably includes a ski plate but may further preferably include a front wheel mounted on the front support and contacting the ground. A front brake is preferably attached to the front support and selectively frictionally engageable with the front wheel. A front brake controller is disposed on the front portion of the frame and connected to the front brake for selectively engaging the front brake with the front wheel to slow rotation of the front wheel. By providing both front and rear braking systems, the vehicle is more stable and easier to control and may be stopped over very short distances. Both front and rear brakes may be caliper brakes having hand grip controllers disposed on the steering mechanism and connected to their respective brakes via cables, for example. 
     As mentioned above, the drive assembly includes a track disposed around the guide wheel and the drive wheel. The track frictionally engages the wheels. One embodiment of the inventive track includes providing a first side of the track with a plurality of knobs and the rims of the guide and drive wheels with a plurality of bosses. The bosses engage the knobs in a synchronous manner; when the drive wheel rotates, the bosses push against the knobs to cause the track to move without slipping with respect to the drive wheel and the guide wheel. Alternatively, the wheels may be provided with recesses into which the knobs on the track fit for the same effect. In the preferred embodiment, however, the inner surface of the track (that which contacts the wheels) may be provided with substantially flat portions which frictionally engage the rims of the wheels. The wheels may be provided with circumferential channels and the inner surface of the track with a raised portion which fits inside the circumferential channels. Side walls of the channels help prevent the track from disengaging the wheels. 
     In another embodiment, the track is trapezoidal in cross-section, with the wider surface facing outwards and contacting the ground and the smaller surface facing inwards and sitting in a channel in the wheels. The side walls on the wheels in this embodiment are angled to accommodate the angled sides of the trapezoidally-sectioned track. 
     The track is preferably made of rubber with a core of a flat reinforcing member made of spring steel, nylon, cloth, or a combination thereof. The reinforcing member prevents the track from stretching and enables the track to retain its shape more readily. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a left side perspective view of a snow cycle according to the invention. 
     FIG. 2 is a right rear perspective view of the inventive snow cycle of FIG.  1 . 
     FIG. 3 is a schematic of the inventive snow cycle depicting flexure of the frame. 
     FIG. 4 is a perspective view of the drive wheel of the invention. 
     FIG. 5 is an exploded perspective views of the components of the drive wheel of the invention. 
     FIG. 6 is a top perspective view of the track of the invention. 
     FIG. 7A is a magnified view of an end of the track of FIG.  6 . 
     FIG. 7B is a longitudinal schematic view of the profile of the track of FIG.  7 A. 
     FIG. 7C is a sectional view of a different embodiment of the track of the invention. 
     FIG. 8A is an exploded perspective view of the front shock absorber according to the invention. 
     FIG. 8B is a side view of the front shock absorber of FIG.  8 A. 
     FIG. 8C is a side sectional view of the front shock absorber of FIGS. 8A-B. 
     FIG. 9 is a side schematic of a motor-assisted embodiment of the inventive snow cycle. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Description will now be given of the preferred embodiments with reference to exemplary FIGS. 1-9 attached hereto. Referring to FIGS. 1 and 2, the inventive snow cycle  5  includes a frame  8  having a front frame portion  10  and a rear frame portion  12 . Frame  8  may be constructed of tubular steel, aluminum, graphite, or any other lightweight suitable material. Front and rear frames  10  and  12  are connected together at several points in a way to allow for flexure of frame  8  and minor relative movement between front and rear frames  10  and  12 . The lowermost portion of front frame  10  is connected to the forwardmost portion of rear frame  12  at point  13  near the pedal crank. Seat  14  is attached to front frame  10 . A central shock absorber  16  is mechanically coupled between front frame  10  and rear frame  12 . Shock absorber  16  is hingedly or pivotally attached to front frame  10  by pin or rivet  17 , and it is hingedly or pivotally attached to rear frame  12  by pin or rivet  18 . 
     The forwardmost end of front frame  10  terminates is a tubular section  20 . Steering shaft  22  passes through tube section  20  and is adapted to freely rotate inside tube section  20 . Handlebars  24  are attached to the upper portion of steering shaft  22 , and a front ski  26  is attached to the lower portion of steering shaft  22 . Ski  26  is hingedly attached to the lower end of shaft  22  via mounting plate  28  and pin  30 . Mounting plate  28  is secured (e.g., bolted, welded, riveted, etc.) to ski  26  which is, in turn, hingedly secured to the outer cover  32  of the steering column by pin  30 . When a user turns handlebars  24 , front ski  26  turns with them, thereby enabling the user to steer the vehicle  5 . Ski  26  is allowed to pivot around pin  30  to accommodate variations in terrain. At least one handbrake  34  is provided on handlebars  24  to enable the user to slow the rate at which the vehicle is travelling. In one embodiment, brake  34  is a caliper brake connected to the drive system  50  via a cable, a hydraulic-assisted cable, or a fully hydraulic hose ( 34 A), all of which are known in the ordinary bicycle arts but not in the snow/ice vehicle arts. Squeezing handle  34  closes the caliper  34 B around disc  34 C of one of the wheels to retard the velocity of the wheel and thus slow the vehicle. Instead of a ski plate as shown, the front of the snow cycle may be supported by a wheel (not shown). If a wheel is provided for the front of the device, the handlebars would preferably be provided with a second caliper brake (not shown) which would be connected via a cable, etc. to calipers surrounding the front wheel in the manner of a conventional bicycle. A track similar to the one employed in the rear drive system may also be used as a front support. The handlebars would again be provided with a front brake for the front track. 
     As best illustrated in FIG. 2, drive system  50  preferably includes a pedal crank  52  having pedals  54 . A person places his feet on pedals  54  and applies force to the pedals in a conventional alternating manner. A central gearing  56 , which includes a number of differently-sized gears  58 , is connected to pedal crank  52  via chain belt  60 . A gear derailer (not shown) is provided which enables the user to shift chain belt  60  off of one gear  58  and onto another, in the manner of a conventional bicycle. Alternatively, a single gear could be provided in place of the set of gears  58  shown in FIG. 2, similar to a single-geared bicycle. In either case, a second chain belt  62  is connected from central gearing  56  to drive wheel  64 . Drive wheel  64  has a toothed plate  66  for receiving chain belt  62 . The drive wheel is attached to the rearwardmost portion of rear frame  12 . Preferably disposed in front of drive wheel  64  is a leading guide wheel  68  also mounted on rear frame  12 . Surrounding drive and guide wheels  64  and  68  is a track  70  having a tread side  72  which possesses ribs  74 . The specifics of drive and guide wheels  64  and  68  and track  70  will be discussed below. When a person pedals the snow cycle, pedal crank  52  is turned, chain  60  transmits the torque to central gearing  56  (which also turns), chain  62  transmits the torque to drive wheel  64 , and track  70  is rotated to thereby propel the vehicle. 
     The drive train  50  preferably takes on the “inverted V” shape as depicted in the figures, with the drive wheel  64  and pedal crank  52  being the end points of the “V” and the central gearing  56  being the vertex of the“V.” This configuration is particularly advantageous in the snow cycle. As described above, a conventional bicycle includes a gear derailer and sprocket set right next to the rear wheel. However, that design would limit the usefulness of a snow cycle. If the user were to drive through deep powdery snow, especially snow that is higher than the center of the drive wheel  64 , the derailer and gearing would drag in the snow. Having the derailer dragged through the snow would slow the cycle down measurably. Also, if any mud, snow, or ice got stuck in the gears, the chains could spontaneously disengage or the gearing could lock up and get stuck. Thus, the gear derailer has to be placed much higher on the frame of the cycle. One alternative solution would be to use a much larger wheel; however, a bigger wheel dramatically increases the weight of the cycle in the rear of the vehicle. Also, the wheel would have to be so much substantially larger than the preferred drive wheel that it would raise the height of the whole device and the center of gravity of the device. By providing a middle gear between the pedal crank  52  and the rear drive wheel  64  in the inventive “inverted V” configuration, the invention raises the gearing well away from the snow without adding significant amounts of weight to the vehicle and without raising the center of gravity or the height of the vehicle. 
     As shown in the figures, particularly FIG. 3, guide wheel  68  is smaller than drive wheel  64  and is preferably positioned off of ground level, as shown in FIG.  3 . The centers of drive wheel  66  and guide wheel  68  are preferably connected with a pair of struts  67 . Because of the relative positions and sizes of the two wheels, struts  67  are angled slightly downwards (see FIG. 3, for example) in a rear-to-forward direction with respect to the ground. By positioning guide wheel  68  off of the ground when the cycle is in it&#39;s resting state, track  70  is raised off of the ground and is angled upwards with respect to the ground in a rear-forward direction, as shown by angle α in FIG.  3 . Raising track  70  off of the ground causes a snowplow effect; when the vehicle is moving, snow and ice tend to build up slightly at the vertex of the angle where the track meets the ground. This snowplow effect assists the user in braking maneuvers. Raising the leading edge of track  70  up off the ground helps prevent the track from getting stuck on any outcroppings in the ground. It is also contemplated as being within the scope of the invention to configure guide wheel  68  as resting on the ground; that is, it is optional but not required to angle track  70  upwards. 
     As discussed above, front frame  10  and rear frame  12  are hingedly connected together in such a manner as to allow the frame  8  to flex and front and rear frames  10  and  12  to move slightly apart. This flexure causes guide wheel  68  to move lower to the ground, as shown in FIG.  3 . The more the frames flex, the lower the guide wheel moves, and the greater the amount of track  70  is in contact with the ground. When the user sits on seat  14 , his weight causes the frame to flex and thus causes the guide wheel to move lower towards the ground. Most other high stress activities on the cycle, e.g., braking, turning, accelerating, etc., cause the frames  10  and  12  to flex and guide wheel  68  to be lowered. The greater the amount of track  70  is in contact with the ground, the greater the amount of traction is afforded to the device, and the greater the amount of stability is provided. Hence, as a person rides the cycle  5  harder or more vigorously, the cycle compensates to increase stability and traction. 
     The track and wheel system can be off-the-shelf items, however a preferred design is described here. As shown in FIGS. 4-5, drive wheel  64  is made up of two wheel sections  61  and  63  which are connected together at connections  69 . The sections  61  and  63  are each provided with circumferential rims  61 A and  63 A, respectively. When sections  61  and  63  are connected together, rims  61 A and  63 A do not meet but rather form a channel  65  therebetween. Wheel section  61  includes an inwardly projecting circumferential flange  61 B, and wheel section  63  includes a similar flange  63 B which forms the floor or bottom surface of channel  65 . The respective vertical surfaces between flange  61 B and rim  61 A and flange  63 B and rim  63 A forms side walls  65 A. The purpose of channel  65 , flanges  61 B and  63 B, and side walls  65 A will be explained below. While the description given here is for the drive wheel  64 , it may also apply to guide wheel  68 . 
     The inventive track  70  is depicted in FIGS. 6-7C. The surface that contacts the ground is tread  72  which is preferably made of rubber. Tread  72  includes raised portions  74 ,  76  which grip snow and ice and provide for increased traction when the vehicle is operating. Raised portions  74 ,  76  can be formed integrally from the same rubber as tread  72 , or they may be added as separate pieces. As shown in FIG. 6, track  70  is not made as a circle or an oval but rather as a flat belt having ends  78 ,  80 . FIG. 7A depicts a close-up of one of the ends of the track and, along with FIG. 7B, illustrates the total structure of the track  70 . The “top” side of track  70  which contacts the ground includes tread  72  as discussed above. The reverse or “bottom” side  82  of track  70 —the side that faces wheels  64  and  68 —preferably includes a central raised section having protuberances  84  and flat side landings  86 . 
     The track is preferably made of rubber with a flat reinforcing member disposed within the rubber; the rubber is molded around the reinforcing member. The reinforcing member may be a sheet of spring steel, a band of nylon (either as a solid flat piece or in the form of a mesh), or a band/mesh of cloth. Preferably, the drive and guide wheels are made of nylon. When track  70  is disposed around the drive wheel  64  and the guide wheel  68 , protuberances  84  fit inside channel  65  of drive wheel  64 , and side landings  86  sit on top of circumferential rims  61 A and  63 A. Because track  70  is made of rubber and the wheels  64 ,  68  are made of nylon, there is excellent frictional engagement between the track and the wheels; the track will not slip or slide over the wheels. Track  70  frictionally engages the wheels in a number of locations: sides  84 A engage side walls  65 A of wheel  64 , the tops of protuberances  84  engage flange  63 B, and flat landings  86  engage circumferential rims  61 A and  63 A. The profile of the inventive track is shown in a head-on broken view in FIG.  7 B. 
     In another embodiment, the track may be formed as shown in section in FIG.  7 C. Track  70 ′ is trapezoidal in cross-section; the smaller width side  82 ′ fits inside channels  65  of the wheels, and the wider side  72 ′ forms the tread. The protuberances  74 ,  76  of the tread of FIG. 6 are intended to project from surface  72 ′ as well. To accommodate the angled side walls  84 A′ of track  70 ′, the side walls  65 A of wheels  64 ,  68  are also angled accordingly. Track  70 ′ is made of rubber  92  which is molded around a flat reinforcing member  94  (track  70  may also be formed in this fashion, i.e., with rubber molded around a reinforcing member). Reinforcing member  94  helps track  70 ′ retain its shape and prevents the track from stretching. 
     In an alternative embodiment, the bottom side  82  of the track  70  may include a plurality of knobs (similar to those shown as reference numeral  84 ) and the wheels  64 ,  68  are not provided with a central circumferential channel but rather a series of bosses (protuberances, not shown). The bosses engage the knobs in a synchronous manner like gear teeth. When the drive wheel rotates, the bosses push against the knobs to cause the track to move without slipping with respect to the drive wheel and the guide wheel. As another alternative, recesses in the circumferences of the wheels may be provided instead of projecting bosses; in that embodiment, the knobs of the track engage the recesses for the same effect. 
     The ends  78 ,  80  of track  70  are matingly engageable to form a loop when engaged. As shown in FIG. 7A, at each end of track  70  are provided flanges  88  which extend out from the ends of the track along the longitudinal axis of the track. Flanges  88  are preferably nestled within and surrounded by the rubber of the track. The flanges are preferably provided with through holes  89  through which a locking pin  90  may be fitted. When the ends  78 ,  80  of track  70  are mated together, their respective flanges  88  are interleaved and locking pin  90  is passed through all of the through holes  89  of the flanges, thereby locking the ends of the track together in mated engagement. By recessing the flanges so that they are at least partially surrounded by rubber, when the ends of the track are locked to form a closed loop, the surface that contacts the ground is of substantially seamless rubber with no gaps. 
     The front support of the snow cycle is provided with a shock absorber internal to outer cover  32  of FIG.  1 . FIGS. 8A-C depict the structure of the shock absorber  100  in accordance with the invention. As shown in all of these figures, the left side of the drawing is the end closest to the handlebars  22 , and the right side of the drawing is the end closest to the ski  26 . Main shaft  102  is disposed within inner plug  104  which, in turn, is disposed within casing  106 . Plug  104  is preferably welded to the bottom interior of casing  106 , as shown in FIG. 8C; numerals  109  reference the welds. Between the bottom of main shaft  102  and the interior of plug  104  is a spring  112  which provides the shock absorbing quality of the configuration. A brass bushing  108  is provided fixedly connected to plug  104  and disposed around main shaft  102 . Main shaft has a slot (not shown) into which key  110  is press fit, substantially radially through main shaft  102 . Bushing  108  also has a slot  109  which can accommodate key  110 . Slot  109  is dimensioned to allow key  110  to move freely back and forth along slot  110  but does not allow main shaft  102  to rotate longitudinally with respect to casing  106 . That is, because bushing  108  is fixedly secured to plug  104 , which is fixedly secured to casing  106 , main shaft  102  may only move in a reciprocating fashion along its axis within the range of movement allowed by key  110  within slot  109 . Screw cap  114  screws around the top of casing  106  and keeps all of the parts together. Casing  106  is locked into outer cover  32  by locking screws  36 . By providing this structure, shock absorber  100  may easily be removed from the cycle  5  if it needs to be replaced. 
     The above description has been for a snow cycle that is operated manually. However, the device may be motorized as well. As depicted schematically in FIG. 9, an engine  150  is represented in block form. Engine  150  is mechanically coupled to central gearing  56  and provides the torque needed to turn drive wheel  64 . For this motorized embodiment, pedals may optionally be deleted and replaced with foot pegs  152  upon which the user may rest his feet when operating the snow cycle. Alternatively, a hybrid version of the snow cycle that incorporates the pedal crank of FIGS. 1 and 2 as well as the engine of FIG. 9 is also contemplated. U.S. Pat. No. 5,941,332 to Dimick teaches a motorized bicycle which has both pedals and a motor. The motor may be used in tandem with the pedal crank for a motor-assist type of ride. A specific clutch mechanism allows the user to selectively engage and disengage the motor while pedalling. The teachings of this Dimick patent are fully incorporated by reference herein. 
     The invention is not limited to the above description but rather is defined by the claims appearing hereinbelow. Modifications to the above description that include that which is known in the art are well within the scope of the contemplated invention. For example, the device is described as a snow cycle, however it can be used on ice, mud, dirt, pavement, or any other surface. Also, the drive wheel has been described as being made of nylon, however any suitable material can be used which is light weight and provides a good coefficient of friction with the track. Similarly, the track has been described as being preferably made of rubber, however any material may be used. Also, as discussed above, the central gearing may be eliminated in an embodiment which has only one speed of operation. Further, the precise geometries of the front and rear frames may be modified from what is shown in the figures and still fall within the claims.