Snowmobile

A snowmobile including a body a pair of rear wheels with tires a motor for driving the rear wheel, an axis connected to a handle originally for a front wheel, and skid member mounted on the axis. The skid member comprises a skid, extending in the longitudinal direction of the body, bent upward in its front part, support members protuberantly provided on the upper surface of the skid, and rotatably connected to the axis and at least one fin, protuberantly provided on the under surface of the skid, extending front to rear from a position beneath the above mentioned support member, located at the substantial center in its longitudinal direction of the skid, and the length of the fin is set in a range of 40 to 60% of the length of the skid.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a snowmobile having a skid and a pair of 
driving wheels. 
2. Prior Art 
To run on rough roads such as sandy, muddy, bump, or rocky roads, there has 
been favorably used a three wheeler so called three wheeled buggy that 
runs comparatively slow. And to run on a snow surface with such three 
wheelers, detachable skids fixed thereto have been proposed. 
Hitherto, such skids have been fixed on the tire of the front wheel or on 
the front fork for sustaining the front wheel. 
As for the skids fixed on the front fork, its under surface can not comply 
with the inclined snow surface. As a result, grip and maneuverability are 
decreased. Further, the skid sometimes strikes the ground under the snow, 
and the rider is placed in danger. 
On the other hand, as for the skids fixed on the tire of the front wheel, 
the under surface can comply with the inclined snow surface, but the 
relative portion between the front wheel and the skid is liable vary, and 
running stability becomes bad. 
SUMMARY OF THE INVENTION 
It is therefore, an object of the present invention to provide a snowmobile 
improved in capability to run safely on the snow wherein the skid can 
incline according to the inclination of snow surface without any change in 
the relative position between the skid and the body by mounting skid 
members rotatably on the front wheel axis of an all terrain three wheeler 
and providing a fin on the under surface of the skid. 
According to one aspect of the present invention, the snowmobile comprises 
a body, a pair of rear wheels with tires, provided on the rear portion of 
the body, a motor for driving the rear wheels mounted on the body, an axis 
originally for a front wheel, provided on the front portion of the body 
and connected to a handle; and skid members mounted on the axis. The skid 
members comprise a skid, extending in the longitudinal direction of the 
body, bent upward in the front part, support members, protuberantly 
provided on the upper surface of the skid and rotatably connected to the 
axis, and a fin, protuberantly provided on the under surface of the skid, 
extending from front rear under the position of the support members, 
located at its longitudinal center, the length of the fin being 40 to 60% 
of the length of the skid. 
Preferably, the skid members comprise one fin extending along the center 
line of the skid or two fins each extending along each edge of the skid.

DETAILED DESCRIPTION OF THE INVENTION 
An embodiment of the present invention will now be described, by way of 
example only, referring to the drawings. 
In FIG. 1, the snowmobile 1 is based on a conventional buggy type All 
Terrain three wheeler, and is characterized in that skid member 11 is 
rotatably mounted on the front wheel axis 7, instead of a front wheel. 
The body 3 is provided on its middle portion with a motor M, such as 
gasoline engine, and also provided on its rear portion with a rear wheel 
axis 16 connected to the motor M through a transmission mechanism of 
well-known construction. 
The rear wheels 2, 2 are attached to both ends of the rear wheel axis 16, 
respectively. A block pattern tire T for the All Terrain Vehicle, with 
blocks on the tread surface, is mounted on each rear wheel 2. 
Further, the body 3 is provided on its front portion with a a front fork 
19. 
The front fork 19 is composed of a pair of pipes with a built-in suspension 
mechanism of well-known construction, and provided on its upper end with a 
handle 5. On the other hand, the lower end of each pipe is pressed to form 
a flattened part 21, and holes 20 (FIG. 2) are made therein, and the above 
mentioned wheel axis 7 passes goes through the holes 20 fastened by the 
hexagon head bolt, to support rotatably the skid member 11. 
In FIGS. 2 and 3, the skid member 11 comprises a skid 9, support member 10, 
a pair of fins 12, and further in this embodiment, a spring means 25 for 
biasing the front end of the skid 9 upward and a stopper 26 for limiting 
the inclination of the skid 9 by the spring means 25. 
The skid 9 extends in the longitudinal direction of the body 3, and is bent 
upward in the front part and rear part. There can be used for the skid 9 
any material having low friction against snow, for example, synthetic 
resin, or composite material such as resin coated metal, like aluminum, or 
fiber reinforced plastic, FRP. Especially, FRP is preferred for its high 
strength and low friction. In this embodiment, the length L2 (FIG. 4) of 
the front and rear bent parts 13 is 6% to 12% of the whole length L1 of 
the skid 9, and the bent height L3 of the bent part 13 is 6 to 12% of the 
length L1 of the skid 9. 
Each fin 12 projects downwardly from the under surface of the skid 9, and 
in this embodiment, extends along each edge of the skid 9, and the fins 12 
and the skid 9 are formed as a onepiece body. 
In the longitudinal direction of the body 3, each fin 12 extends from front 
to rear from beneath the position where the support members 10 are located 
at its substantial center. 
The length L4 of each fin 12 is 40% to 60% of the length L1 of the skid 9. 
When the length L4 is less than 40%, the stability in straight running 
becomes worse. On the contrary, when the length L4 is more than 60%, the 
stability becomes better, but maneuverability in cornering becomes bad. To 
make the stability in straight running and the maneuverability in 
cornering compatible with each other, the best range for the length L4 is 
40% to 60% of the length L1 of the skid 9. 
The support member 10 is protuberantly provided on the upper surface of the 
skid 9 and, in this example, includes an almost stand-shaped base 29 
protruding from the upper surface of the skid 9, a pair of support plates 
309A and 30B provided on the top surface of the base 29, facing each other 
in the widthwise direction of the skid 9, and a support pipe or pin 31 
bridging over the support plates 30A and 30B to connect them in one body. 
A center hole 31A passes through the support pin 31 and opened at the side 
faces of the support plates 30A and 30B, and the wheel axis 7 penetrates 
therethrough. The skid member 11 is attached rotatably by the axis 7 which 
penetrates though the holes 20 of the front fork 19 and the center hole 
31A of the support member 10. The reference W indicates a washer disposed 
therebetween. 
The distance of the center hole 31A form the under surface 27 of the skid 
9, which defines the height H1 of the skid member 11, is between the 
height H2 plus 25 mm and minus 25 mm, wherein the height H2 is a distance 
between the center of the front wheel and the ground S when the front 
wheel 8 is attached to the front fork 19 and subjected to a static load. 
Accordingly, the skid member 11 is rotatably attached to the axis 7 without 
throwing the body 3 off balance. 
Further, in this embodiment, the skid member 11 includes the spring means 
25 and the stopper 26. 
The spring means 25 is, in this example, a torsion coil spring 33 slipped 
on the support pin 31. The spring 33 is provided on its ends with hook 
portions 33A and 33B, and the hook portion 33A holds the rear of the front 
fork 19, and contrary the hook portion 33B holds the front of the support 
plate 30B, whereby the front end of the skid 9 is forced upward. 
The stopper 26 is, in this example, a bolt piece 36 fixed on a L-shaped 
joint part 35 with nuts adjustablly of its backward projection therefrom. 
The joint part 35 is provided in the front portion of the top of the 
support plate 30B, and bent at its front so that the bent piece 35A 
extends outward in the widthwise direction of the skid 9, and the bolt 
piece 36 pierces it from the front to the rear thereof. As shown in FIG. 
4, a confliction of the rear end 37 of the stopper 26 with the front of 
the front fork 19 limits the upward inclination of the skid 9. The end 
point of the inclination is adjustable by adjustment of the stopper 26, as 
mentioned above. 
FIGS. 5 and 6 show another embodiment of the present invention, wherein the 
skid member 9 comprises a pair of detachable fins 12, and further show 
another example of the spring means 25 for use in case the fender F is 
attached to a comparatively low position of the body 3. 
The skid member 11, in this embodiment, comprises the skid 9, the support 
member 10 and a pair of fins 12, which are formed separately. 
The support member 10 comprises a base plate 10B extending along the skid 
9. 
The fins 12 are connected at their upper edges by a connecting plate 38 
disposed between the skid 9 and the base plate 10B, and the fins 12 and 
the connecting plate 38 form a one-piece channel member 14. 
The base plate 10B, the connecting plate 38 and the skid 9 are fixed by 
bolts 15 passing through the holes 39A, 39B, 39C provided therein, 
respectively, whereby the fins 12 project downward beyond the under 
surface of the skid 9 and extend along each side of the skid 9. Obviously 
the fins 12 can be detached. 
Accordingly, by making the fins 12 detachable, it becomes easy to 
substitute new fins for a damaged one, and further it becomes possible to 
choose material combinations most suitable for each part under the snow 
condition, for example, FRP for the skid 9 and stainless steel, having 
strength and toughness, for the fins 12. 
The spring means 25 in this example can adjust its force biasing the skid 
9, and comprises the above mentioned torsion coil spring 33 and ring 
members 40A, 40B slipped loosely on the support pipe or pin 31. 
A ring member 40A is disposed between the support plate 30A and the spring 
33, and connected to one end of the spring 33 by the hook portion 33A. 
Further, on the outer side of an expanded part 41A formed on the periphery 
thereof, a hook pin 42 is provided to contact with the rear of the front 
fork 19, whereby one end of the spring 33 is caught on the front fork 19 
through the hook portion 33A, the ring member 41A and the hook pin 42. 
On the contrary, the ring member 40B is disposed between the support plate 
30B and the spring 33, and connected to the other end of the spring 33 by 
the hook portion 33B. A clamp 45 is provided in an expanded part 41B 
formed on the periphery of the ring member 40B. The clamp 45 has a handle 
43 at the upper end and can screw up and free the support pipe 31, whereby 
the other end of the spring 33 can be fixed to the support pipe 31 at 
almost any position therearound. 
Therefore, by rotating the handle 43 to release the support pipe 31, and 
turning down the handle 43 to wind up the spring 33, then rotating 
reversely the handle 43 to screw up the support pipe 31, the force biasing 
the skid 9, that is, forcing the front end thereof upward is increased. 
To make the clamp more secure, the support pipe 31 is preferably provided 
on its periphery with dents which the inner tip 45A of the clamp 45 gets 
into. 
FIG. 7 shows the skid member 11 of another embodiment of the present 
invention wherein the skid member 11 include one fin 12 extending along 
the center line of the skid 9, and the fin 12 and the skid 9 are formed in 
a one-piece body. 
The support member 10 comprises the base 29 and the support plates 30A and 
30B thereon, but in this embodiment each support plate is formed in two 
pieces including a lower piece 30A1, 30B1, fixed to the base 29 and an 
upper piece 30A2, 30B2 joined thereto by metal fittings 51. In the bottom 
of the upper piece 30A2, 30B2, and the top of the lower piece 30A1, 30B1, 
semicircular cuts 50 are provided to form holes 31A into which the axis 7 
is inserted, and the metal fittings 51 are fixed on the front and rear of 
the above mentioned pieces with screws. 
Accordingly, in this embodiment, the skid members 11 can be attached and 
detached without detaching the axis 7 from the front fork 19. 
FIGS. 8 to 10 show the fin 12 of the skid member 11 a further embodiment of 
the present invention, wherein the skid member 11 includes a detachable 
one fin 12 extending along the center line of the skid 9. As shown in FIG. 
9, the fin 12 is provided on its upper edge with a mounting plate 55 whose 
upper surface touches the under surface of the skid 9, and the mounting 
plate 55 is fixed with fixing pieces 56, such as bolts or the like. 
The mounting plate 55 can be fixed on the flat surface of the skid 9 as 
shown in FIG. 8, or in a groove 57 provided on the under surface of the 
skid 9, as shown in FIG. 10. In the later case, the drag will be 
decreased, and positioning of the fin 12 becomes easy. 
(WORKING EXAMPLES AND COMATIVE TEST) 
PREFERRED EMBODIMENTS 
Test examples by way of trial and comparison tests for maneuverability were 
made. 
In each example, the skid and the fin/fins were formed into a one-piece 
body, and in case one fin was provided, that fin extended along the center 
line of the skid. On the contrary, in case two fins were provided, those 
fins extended in parallel along the edges of the skid, respectively. 
The examples were evaluated as to their maneuverability in straight running 
and cornering with varying the ratio of the fin length (L4) to the skid 
length (L1) as shown in table 1, wherein the value indicates a mean value 
of the evaluations by three drivers in a feeling test method, and the 
larger the total value, the better the maneuverability, and further the 
average speed for test was 30 km/h. 
TABLE I 
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Ex. Fin L4/L1 Maneuverability 
No. number location (%) straight 
cornering 
total 
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Embodiments of the invention: 
1 2 edges 42 130 140 270 
2 2 edges 57 140 130 270 
3 1 center 42 140 150 290 
4 1 center 57 160 145 305 
Control examples: 
1 0 -- -- 100 100 200 
2 2 edges 65 150 105 255 
3 2 edges 32 110 120 230 
4 1 center 32 110 130 240 
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As apparent from Table 1, the embodiments of the present invention were 
better in maneuverability than the control examples. 
As mentioned above, in this invention, the snowmobile is based on the 
hitherto used three wheeler for all terrain, and the skid members are 
rotatably mounted on the body by the front wheel axis instead of the front 
wheel. Accordingly, the skid members are attached without looseness 
between the skid members and the axis 7, that is, the displacement between 
the body and the skid members. As the result, a running stability is 
improved, and the grip is also increased because the under surface of the 
skid can incline in accordance with the inclination of the snow surface. 
Besides, thrusting of the front end of skid into the snow can be avoided. 
Furthermore, the fin of a certain length projects into the snow. 
Accordingly, the maneuverability in straight running and that in cornering 
at high speed are improved at the same time. 
In addition, the spring means and the stopper prevent the front end of the 
skid from thrusting into the snow at the time of landing after jumping as 
seen in racing, and safety in high speed running is maintained.