Note: Descriptions are shown in the official language in which they were submitted.
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Carving Toboc~gan
This invention relates to ice skates and toboggans, and
more particularly but not exclusively, to a class of
boards (also known as snowdecks) for use primarily on
snow. In this context, a snowdeck may be regarded as
a type of skateboard for use on snow, or as a binding-
less snowboard.
Conventional toboggans are well known but suffer from the
disadvantage that they cannot readily be steered. A
rider can produce some form of steering by, for example,
sticking out his foot to brake one side of the toboggan
but this form of steering falls far short of what is
possible using skis or a snowboard. Skis allow a skier
to steer but skis suffer from the disadvantage that it
is difficult for a beginner to use them effectively.
Snowboards also allow their riders to steer themselves
but, like skis, are difficult for a beginner to use
effectively. On the other hand, toboggans are very easy
to use but do not offer the turning ability of skis or
snowboards..
Skis and snowboards allow effective turns to be made as
they can be made to carve through the snow. By carve,
it is meant that the ski or snowboard is deformed by the
user so that the footprint in the snow of the ski or
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snowboard is formed into an arc. As the front portion
of the ski or snowboard travels over the snow, it forms
a groove in the snow and the rear portion of the ski or
snowboard subsequently travels through that groove. If
the footprint does not have the appropriate arcuate shape
for the turn being performed, or if the footprint has
some shape other than arcuate, then the rear portion will
not be able to travel through the groove. In this
situation the rear portion will modify the shape of the
groove, thereby increasing friction between the ski or
snowboard and the snow. In extreme cases, the rear
portion will barely follow the groove, and will instead
skid across the snow.
An important factor in the use of skis and snowboards is
dynamic stability. To initiate a turn at a given speed,
a rider momentarily unbalances himself so that he leans
over to one side. As he leans over, he also tilts and
flexes the ski or snowboard so that its footprint in the
snow is bent into an arc. The arc shape causes the rider
to follow a circular path and the centrifugal force
produced as a result of the circular path is balanced by
the lean of the rider. The rider is therefore
dynamically stable: even though he is leaning over to one
side, he does not fall over. He can continue to lean
over to one side indefinitely provided that he continues
to follow the appropriate circular path over the snow at
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the appropriate speed.
The need to instinctively bend the footprint of the ski
or snowboard into the appropriate shape, and to balance
the resultant dynamic forces without falling over, are
factors that make skiing and snowboarding difficult.
There is therefore a need for an apparatus that allows
carving turns to be readily made in snow.
Skateboarding has become a popular pastime and
apparatuses have been devised in an attempt to recreate
the skateboarding experience on snow and thus allow
skateboarding enthusiasts to enjoy their pastime as a
winter sport. Such devices do not emulate the turning
ability of a skateboard and there is therefore a need for
an apparatus which will allow effective turning on snow.
FR 2383679 discloses an apparatus, for use on snow,
having an underside which is curved both longitudinally
and transversely. Longitudinal guides mounted on the
underside of the apparatus are curved so that guides
nearer the longitudinal axis are less curved than guides
located further away from the longitudinal axis.
US D448,441 discloses a snow-sliding apparatus having a
flat underside and having straight longitudinal grooves.
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According to one aspect of the invention, there is
provided a vehicle for travelling over a carveable medium
such as snow, sand or ice, and having a longitudinal axis
about which the vehicle can roll relative to the surface
of the medium. The vehicle comprises a straight runner
means for travelling on the medium in a substantially
straight line when the vehicle is tilted at a first
predetermined roll angle relative to the medium and a
first curved runner convex toward the straight runner
means. The first curved runner comprises a substantially
circularly arcuate portion of a first radius for
travelling on the medium in a substantially circular path
by carving the medium when the vehicle is tilted at a
second predetermined roll angle relative to the medium.
Preferably, the straight runner means comprises a
straight runner, but alternatively the straight runner
means may comprise a pair of oppositely curved runners.
In a further alternative embodiment, the vehicle may
comprise a second curved runner arranged on the side of
the straight runner means opposite to the first curved
runner and convex toward the straight runner means. The
second curved runner may comprise a substantially
circularly arcuate portion of a second radius for
travelling on the medium in a substantially circular path
by carving the medium when the vehicle is at a third
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predetermined roll angle relative to the medium.
In a yet further preferred embodiment, the first and
second radii are equal and most preferably, the first and
5 second curved runners are symmetrical with respect to the
straight runner means.
The vehicle may comprise a plurality of curved runners
arranged on one side or both sides of the straight runner
means.
An advantage of such an vehicle is that by tilting or
rolling the vehicle, a rider can select an appropriate
carving surface to perform a turn of a desired radius.
Another advantage of the vehicle is that the angle of
tilt or roll required to select a carving surface
corresponds with the curvature of the selected carving
surface, so that a rider more easily achieves the dynamic
balancing required to execute good carving turns. The
correspondence between the angle of tilt and the
curvature is the same as the correspondence between the
angle of lean of a bicyclist and the curvature of the
path that the bicyclist follows. Many people are
familiar with riding a bicycle and thus the vehicle
allows such people to readily become proficient at
performing carving turns on snow.
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In one embodiment the vehicle has a form similar to that
of a skateboard. In other embodiments the apparatus may
be used as a toboggan or as ice skates.
Preferred embodiments of the present invention will now
be described by way of examples and with reference to the
following drawings, in which:
Figure 1 is a perspective view of a snowdeck according
to the present invention being ridden by a rider;
Figure 2 is a perspective view of the underside of the
snowdeck;
Figure 3 is a plan view of the underside of the snowdeck;
Figure 4 is an end elevation view of the snowdeck;
Figure 5 is a side elevation view of the snowdeck;
Figure 6 shows a cross-sectional view of the snowdeck in
a plane located towards one end of the snowdeck;
Figure 7 shows a cross-sectional view of the snowdeck at
a plane located at the centre of the snowdeck;
Figure 8 shows a partly perspective view, not to the
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correct proportions, which illustrates the geometry of
the carving surfaces of the snowdeck;
Figure 9a shows the rider and a cross-sectional view of
the snowdeck and also shows a plan view of the rider and
snowdeck together with the track made in the snow by the
snowdeck;
Figure 9b shows the rider and a cross-sectional view of
the snowdeck with the snowdeck tilted by a small angle,
and also shows the curved track made in the snow by the
snowdeck due to the small .tilt;
Figure 9c shows the rider and a cross-sectional view of
the snowdeck with the snowdeck tilted by a medium angle,
and also shows the curved track made in the snow by the
snowdeck due to the medium tilt;
Figure 9d shows the rider and a cross-sectional view of
the snowdeck with the snowdeck tilted by a large angle,
and also shows the curved track made in the snow by the
snowdeck due to the large tilt;
Figure 10a shows a snowdeck and rider following an 'S'-
shaped path comprising a left turn, a straight section
followed by a right turn;
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Figure lOb shows a detailed view of the track made in the
snow by a snowdeck following the path shown in Figure
10a;
Figure 11 shows a hull which may be attached to a
skateboard to form a snowdeck;
Figure 12a shows a perspective view of a carving toboggan
according to the present invention;
Figure 12b shows a perspective view of a rider standing
on the carving toboggan and secured to the carving
toboggan by foot straps; and
Figure 13 shows a perspective view of an ice skating boot
according to the present invention.
Figure 1 shows a snowdeck 1 being ridden down a slope by
a rider 3 over snow 5 and also shows the track 7 made in
the snow by the snowdeck 1. In this embodiment the
snowdeck 1 comprises a polyethylene hull 9 which engages
the snow. Mounted on top of the hull 9 is a plywood deck
11 which supports the rider 3. In this embodiment the
snowdeck 1 is 81.3 cm long (32 inches), 20.3 cm wide (8
inches) and has a height of 7 cm (24 inches) at the
centre of the snowdeck 1. In this embodiment four bolts
14 are used at each of two securing regions 13 to secure
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the deck 11 to the hull 9. In this embodiment the top
surface of the deck 11 is covered with foam rubber to
increase the grip and so reduce the risk of the rider 3
becoming dismounted. Also, in this embodiment, an
attachment point 2 is provided so that a tether 4 can be
used to secure the snowdeck 1 to the ankle (for example)
of the rider 3. The tether 4 may be used on public
pistes to prevent the snowdeck 1 from travelling down the
piste without the rider 3.
The rider 3 can steer the snowdeck 1 by leaning himself
and the snowdeck 1 over to one side; the greater the
lean, the sharper the turn. This is explained in more
detail in relation to Figures 9 and 10.
Figures 2, 3, 4 and 5 show a perspective view of the
underside of the snowdeck 1, a plan view of the
underside, an end elevation view of the snowdeck 1 and
a side elevation view, respectively. As can be seen, the
snowdeck 1 has a vertical plane of symmetry about which
the two sides of the snowdeck 1 are symmetric, and has
a longitudinal axis 15 in that plane. The snowdeck 1
also has a vertical plane of symmetry about which the two
ends of the snowdeck 1 are symmetric, and has a
transverse axis 17 in that plane.
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The snowdeck 1 has a straight central surface 19 which
bears the majority of the weight of the rider 3 when the
snowdeck 1 is being ridden in a straight line. Three
convex carving faces 21, 23, 25 are provided on each side
5 of the snowdeck 1 and face toward the centreline of the
snowdeck to allow the rider 3 to make carving turns in
the snow 5 by tilting the snowdeck 1 in order to select
one of the carving faces 21, 23, 25. The profile of the
straight surface 19 and of the carving faces 21, 23, 25
10 is described in more detail in relation to Figures 6 to
8.
The hull 9 has a canoe-like shape. As can be seen most
clearly from Figure 5 in conjunction with Figure 2, each
of the end regions 27 of the hull 9 is rounded off and
tapered upwards to form an angle of a relative to the
horizontal. In this embodiment a has a value of about
38°. More generally, a is preferably in the range 30° to
45°. The end regions 27 allow the hull 9 to slide over
relatively small irregularities in the snow 5, for
example furrows, without digging into such
irregularities. Another advantage provided by the end
regions 27 is that they allow a rider 3 who is
sufficiently skilled to perform "trick" manoeuvres on the
snowdeck 1 which are analogous to those which may be
performed on a skateboard. Such tricks typically involve
pushing down on one end of the deck 11 so that the other
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end of the deck 11 is raised upwards, or even so that the
entire snowdeck 1 is bounced up from the snow 5. If the
straight surface 19 and the carving faces 21, 23, 25
extended as far as the end regions 27 then it would be
more difficult to perform such manoeuvres as the hull 9
would tend to cut into the snow 5 rather than riding over
small irregularities in the surface of the snow 5.
An axis 37 is shown in Figure 3 lying transverse to the
hull 9 at the widest point of the hull 9 before the
profile of the hull 9 changes because of the curvature
of the end region 27. The longitudinal axis 15, the
transverse axis 17 and the axis 37 are shown in Figures
3 to 5 as lying just below the straight surface 19.
Each of the carving faces 21, 23, 25 is provided with a
respective running face 31, 33, 35 facing generally
downwards as seen in Figures 4 and 5. The running faces
31, 33, 35 are curved and meet the lower edges of their
respective carving faces 21, 23, 25 at substantially
right angles. The running faces may meet their
respective carving faces at other angles, but the angle
must not be so acute as to weaken the edge, nor so obtuse
as to reduce the carving effect of the edge. Angles from
75° to 105° are foreseen with angles between 85° and
95°
being preferred. The angle may vary along the length of
the snow deck. The running faces 31, 33, 35 are
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discussed in more detail in relation to Figures 6 to 8.
As can be seen most clearly from Figure 2 in conjunction
with Figure 3, on each side of the snowdeck 1 there are
three recess surfaces 41, 43, 45 which define, with
carving faces 21, 23, 25 longitudinal grooves (in the
hull 9). There are two recess surfaces 41, one on each
side of the straight central surface 19. Each recess
surface 41 connects one edge of the straight surface 19
to the upper edge of the respective carving face 21.
Similarly, each of the two recess surfaces 43 connects
the outer edge of a respective running face 31 to the
upper edge of the next outer carving face 23, and
similarly the two recess surfaces 45 connect the outer
edges of the running faces 33 to the upper edges of the
carving face 25. The sides of the hull 9 form side faces
47.
Figures 6 and 7 show the configuration of the carving
faces 21, 23, 25, the running faces 31, 33, 35 and the
recess faces 41, 43, 45 in more detail. Figure 6 shows
a cross-sectional view of the snowdeck 1 in the plane XX'
of Figure 3. The plane XX' is the widest part of the
hull 9 before the profile of the hull 9 changes because
of the upward curvature of the end region 27. Figure 7
shows a cross-sectional view of the snow deck 1 in the
plane YY' of Figure 3. The plane YY' is at the narrowest
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part of the hull 9 and includes the transverse axis 17.
As can be seen from Figure 6, the underside of the hull
9 at this section has a generally arcuate transverse
profile with a radius of rOX and centre OX on the
longitudinal plane of symmetry of the snowdeck 1. In
this embodiment rOx is 18.5cm. The axis 37 is tangential
to the circle 51X defined by the radius rOX at a point TX
beneath the centre of the straight surface 19. In the
plane XX', each of the two carving faces 21 lies along a
part of one of the two radii 61 that are offset from
vertical by an angle b. Similarly, each of the two
carving faces 23 lies on part of one of the two radii 63
that are offset from vertical by an angle c, and each of
the two carving faces 25 is a segment of one of the two
radii 65 that are offset from vertical by an angle d.
In this embodiment, the angles b, c and d are 11°, 18.4°
and 30°, respectively.
Measured along their respective radii 61, 63, 65, the
carving faces 21, 23, 25 have a "height" of 15mm at this
section of the hull 9.
The running faces 31, 33, 35 can be seen in Figure 6 to
lie tangentially to the circle 51X. In this embodiment,
each of the running faces 31, 33, 35 has a width of 4mm
(the lengths of the running faces 31, 33, 35 correspond
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to that of their respective carving faces 21, 23, 25
along the hull 9).
Although the carving faces 21, 23, 25 lie along the radii
61, 63 and 65, respectively, in the plane XX'the carving
faces 21, 23, 25 are also all part-cylindrical surfaces.
This can be seen from Figure 7 which shows that the
carving faces 21, 23, 25 bunch together as they approach
the plane YY' at the mid-length of the snow deck (at the
transverse axis 17). The lines 71, 73, 75 (in the plane
YY') correspond to the radii 61, 63, 65, in the plane XX'
respectively, in that the carving faces 21, 23, 25 lie
along parts of the lines 71, 73, 75. The lines 71, 73,
75 do not meet at a common point, but meet in pairs at
different heights above the deck 11.
Figure 7 also shows the respective radii r1, r2, r3 of
the cylinders of whose surfaces the carving faces 21, 23,
are parts. The axes of these cylinders lie in the
20 plane YY' and are inclined to the plane of symmetry of
the snowdeck by angles corresponding to angles b, c and
d, respectively. In this embodiment r1 is 4.7m, r2 is
1.9m and r3 is 0.7m. (Note that the radii r1, r2, r3 are
not shown in Figure 6 as that Figure is not in the plane
25 YY' of the cross-sectional view).
Figure 8 provides an alternative way of appreciating that
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the carving faces 21, 23, 25 are parts of respective
cylindrical surfaces. Note that in order to fit Figure
8 satisfactorily on a page, the proportions of Figure 8
are not to scale as the radius r3 is here shown as being
5 smaller than the radius rOX; r3 is actually 3.8 times
larger than rOX. Figure 8 shows two cylinders 81, of
radius r3, of which the carving faces 25 are parts and
also shows the carving faces 25 without the remainder of
the hull 9 or the deck 11.
As shown, the axes 83 of the two cylinders 81 are offset
from vertical by the angle d, and the axes 83 lie in the
same plane YY' as the cross-sectional view of Figure 7
(which contains the transverse axis 17). The two axes
83 intersect above the longitudinal axis 15 of the
snowdeck 1 at point I which is higher above the deck 11
than Ox ( and hence is also higher than 0" since Ox and O"
are the same height above the deck). The length, 1, of
the generators of each of the cylinders 81 is 15mm and
this is the height of the carving faces 25. As shown,
the lowermost edges of the carving faces 25 lie on the
circle 51X in the plane XX'.
Figure 7 also shows that the running faces 31, 33, and
especially the running face 35, protrude beyond the
circle 51Y. This can be understood by reference to
Figure 8 which shows that the radii 65 of circle 51X and
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the lines 75 which are extensions of the generators of
the cylindrical surface 25 in the plane YY' lie in
different planes, and that the radii 65 intersect at a
point OX which is higher above the deck 11 than the
intersection point Z of the lines 75. The circle 51Y has
the same radius, r0," as that of the circle 51X and meets
the transverse axis 17 tangentially at a point TY beneath
the centre of the straight surface 19. (TX and TY both
lie on the longitudinal axis 15, as shown by Figure 8).
Thus, in effect, OX and OY define part of a cylinder
which corresponds to the general cross sectional profile
of the hull 9 in a plane transverse to the longitudinal
axis 15. The end regions 27 are upwardly inclined from
the ends of this cylinder.
As can be seen from Figure 6, the hull 9 has a generally
arcuate profile in transverse section near the end
regions 27 but, as can be seen from Figure 7, has a
flatter transverse sectional profile near the middle of
the hull 9. Arranging for the profile of the hull 9 to
vary along the length of the hull 9 in this way provides
several advantages.
Firstly, a rider 3 will typically use the snowdeck 1 so
that his centre of gravity is located towards the centre
of the snowdeck 1 so that the central surface 19 of the
snowdeck 1 is parallel to the surface of the snow 5.
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With the centre of gravity of the rider 3 located towards
the rear of the snowdeck 1, the rearmost portion of the
hull 9 will bear the majority of the rider's weight and
be urged into the snow 5 more than the middle or front
portions, and this may assist the rider to move off from
rest.
Secondly, the relatively flat profile towards the middle
of the hull 9 minimises the extent to which the snowdeck
1 sinks into the snow 5 when stationary. This helps the
rider 3 to move off from a standing start as the snowdeck
1 will not tend to sink too far into the snow 5. Once
the snowdeck 1 is moving it will tend to plane over the
snow 5.
Figure 9a shows the rider 3 travelling along the Z axis
without tilting the snowdeck 1, so that it runs on the
straight surface 19 and travels along a straight line,
forming a straight track 90a in the snow 5. The
instantaneous footprint 19' of the straight surface 19
is also shown.
Figure 9b shows the rider 3 travelling along a curved
path, having tilted the snowdeck 1 at a small angle b so
that the carving face 21 engages the snow 5. This causes
the snowdeck 1 to travel along a curved path of radius
r1, thereby forming a gently curved track 90b in the snow
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5. As shown, the carving face 21 is now vertical and
does not bear any of the weight of the rider 3. The
weight of the rider 3 is borne by the horizontal running
face 31, together with the recess face 43. The
instantaneous footprint 21' of the carving face 21,
running face 31 and recess face 43 is also shown.
Similarly, Figure 9c shows the rider 3 travelling along
a more tightly "curved" path having tilted the snowdeck
1 at a medium angle c so that the carving face 23 engages
the snow 5 and causes the snowdeck 1 to travel along a
curved path of radius r2, thereby forming a moderately
curved track 90c in the snow 5. As shown, the carving
face 23 is now vertical and does not bear any of the
weight of the rider 3. The weight of the rider 3 is
borne by the now horizontal running face 33, together
with the recess face 45. The instantaneous footprint 23'
of the carving face 23, running face 33 and recess face
45 is also shown.
Finally, Figure 9d shows the rider 3 travelling along a
tightly curved path having tilted the snowdeck 1 at a
large angle d so that the carving face 25 engages the
snow and causes the snowdeck 1 to travel along a curved
path of radius r3, thereby forming a sharply curved track
90d in the snow 5. As shown, the carving face 25 is now
vertical and does not bear any of the weight of the rider
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3. The weight of the rider 3 is borne by the now
horizontal running face 35, together with the side face
47 of the hull 9. The instantaneous footprint 25' of the
carving face 25, running face 35 and side face 47 is also
shown.
The footprint 25' is shown to be thinner and shorter than
the footprint 19', as is apparent from Figure 3 which
shows the straight surface 19 to be longer and wider than
the carving face 25.
Figure 10a shows the rider 3 riding the snowdeck 1 along
an 'S' shaped path 100 comprising a left hand turn 101,
followed by a straight section 102 and finally a right
hand turn 103. The left hand turn becomes progressively
shallower as the rider 3 approaches the straight section
102. The right hand turn. 103 becomes progressively
sharper as the rider 3 leaves the straight section 102
behind. The track that the snowdeck 1 makes in the snow
5 while following the path 100 is shown in more detail
in Figure 10b.
The initial part of the left hand turn 101 is made with
the snowdeck tilted by a large angle d to the left so
that it forms a sharply curved track 90d in the snow.
As the rider 3 reduces the tilt of the snowdeck to a
medium angle c, his weight is progressively transferred
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from the carving face 25, running face 35 and side edge
47 to the carving face 23, running face 33 and recess
face 45. As his weight is transferred, there is a period
of time during which the carving face 25 and the carving
5 face 23 are both engaged in the snow 5 and during this
time tracks 90d and 90c, respectively, are formed
simultaneously, as shown in Figure 10b. Note that during
this time neither of the carving faces 25 or 23 is
vertical and thus neither face is truly "carving" the
10 snow, so the friction between the snowdeck 1 and the snow
5 is increased.
Once the tilt of the snowdeck 1 has been reduced to the
medium angle c, only the carving face 23 is vertical and
15 only a single track is left in the snow 5. As the rider
3 continues to reduce the tilt of the snowdeck 1, the
snowdeck 1 will gradually form a track 90b as well as
90c. With a further reduction of the tilt of the
snowdeck 1 to the small angle b, only a track 90b will
20 be formed. As the tilt angle is then reduced to an angle
smaller than b, further the straight surface 19 engages
the snow and when the snow deck is horizontal only a
straight track 90a is formed in the snow 5.
As the rider 3 tilts the snowdeck 1 progressively to the
right in order to make the right hand turn 103, the above
sequence of transfers is reversed with the carving edges
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on the right-hand side of the board being sequentially
engaged with the snow to make the tracks 90b, 90c and 90d
which are arcs of respective circles. These circles have
been shown more clearly in the right hand turn 103
portion of Figure 10b.
For simplicity, in the foregoing discussion for Figures
9 and 10 of the tracks made by the snowdeck 1, it was
assumed that no more than two carving faces 21, 23, 25
ever simultaneously engage the snow 5. In fact, the
number of carving faces that engage the snow depends on
several factors such as the weight of the rider 3, the
softness or powder quality of the snow 5 and also on the
surface area of the underside of the hull 9. A heavy
rider 3 will cause the hull 9 to sink lower into the snow
5, thus engaging more carving faces than a light rider
3. If the hull 9 is provided with a sufficiently large
surface area, for example by widening or lengthening the
running faces 31, 33, 35 or the straight surface 19, then
the weight of the rider 3 will be distributed over a
larger area, thus minimising the amount by which the hull
sinks 9 into the snow 5.
The way in which the angles of tilt, b, c, d, of the
various carving faces 21, 23, 25 of the snowdeck 1 are
made to correspond with their respective radii r1, r2,
r3 of curvature will now be discussed.
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The angle of tilt of the carving faces 21, 23, 25 and the
curvature of the carving faces 21, 23, 25 are chosen to
be related, at predetermined velocities, by equation ( 1 )
velocity2
tan ( tilt) _ ( 1)
radius. gravity. cos(slope)
where gravity is 9.8m/sz and where slope is the
inclination of the piste.
To design a set of carving faces for the snowdeck 1, it
is first necessary to have some idea of the velocity at
which turning will be performed. This can easily be
determined empirically by measuring the typical velocity
of the snowdeck 1. As the profile of the hull 9 affects
the typical velocity that a rider 3 will achieve, several
iterations of the design process may sometimes be
required. For the snowdeck 1, the carving faces 21, 23,
have been designed to work at 3 m/s, 2.5m/s and 2m/s,
respectively. In practise, each carving face will work
20 over a range of velocities.
An advantage of designing the inner carving faces to work
at higher speeds and greater radii of turn than the outer
carving faces is that the resultant snowdeck will, to
25 some extent, compensate for tilting errors of the rider
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3, thus making it even easier to use. If the rider 3
exceeds the velocity range for a particular carving edge
then the centrifugal force acting on the rider 3 will
tend to push the rider 3 so that he tilts the snowdeck
1 onto a more central carving face. On the other hand,
if the rider 3 is travelling too slowly for a particular
carving face then the centrifugal force acting on the
rider 3 will be insufficient to balance the weight of the
rider 3 as he leans over. In this case, the snow deck
1 will cause the lean of the rider 3 to be increased so
that he uses a less central carving edge, and thus
balancing the velocity, radius of turn and lean of the
rider 3.
Once the intended velocities have been chosen for the
carving faces, their tilt angles can be chosen. The tilt
angles should be chosen so that the carving faces are
sufficiently spaced around the hull in order that the
carving faces (together with their associated running
faces and recess faces ) do not interfere with each other.
For example, tilt angles of 2°, 4° and 6° would not
give
satisfactory results in most circumstances as the carving
edges would be crowded around a small region of the hull.
The maximum tilt angle depends on the width of the snow
deck 1 and on the height of the deck 11 above the
footprint of the hull 9. A wider, higher snowdeck will
allow the rider 3 to attain greater angles of tilt.
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For the snowdeck 1, the angles 11°, 18.4° and 30°
have
been selected for the carving faces 21, 23, 25
respectively. Equation (1) gives the radii 4.7m, 1.9m
and 0.7m, respectively. Most pistes are inclined at an
angle of about 15° which is sufficiently small that the
cos(slope) term can be ignored in most cases when
calculating the curvature of the carving faces.
The height of the carving faces 21, 23, 25 has been set
to 15mm in this embodiment of the snowdeck 1. This value
was chosen with regard to the transverse profile of the
recess faces 41, 43, 45 to ensure that the height of the
carving faces 21, 23, 25 provides sufficient lateral grip
on the snow 5, and to ensure that the transverse profile
of the hull 9 is such that the hull 9 does not sink too
deeply into the snow 5. If the hull were to sink
excessively into the snow then the entire underside of
the hull would be in contact with the snow 5, causing
friction to increase to excessive levels.
Figure 11 shows a hull 111 which may be attached to the
deck of a conventional skateboard to form a snowdeck.
The underside of the hull 111 has the same shape as the
hull 9 so that the hull 111 can also be used to produce
carving turns. Ribs and stiffeners 112 increase the
rigidity of the hull 111 and also allow the weight of a
rider 3 to be transferred from the skateboard ( not shown )
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to the hull 111.
The wheels of a skateboard are generally mounted on
mountings known as "trucks" and each of the two trucks
5 is mounted at one end of a skateboard deck. Each truck
is typically secured using four bolts which pass through
the skateboard deck and into the truck.
The hull 111 is provided with mounting holes 113 at one
10 end and with slots 114 at the other end so that the hull
111 can be readily attached to a conventional skateboard
deck. The mounting holes 113 are spaced so that they
conform to the standard pattern of mounting holes used
to secure a truck to a skateboard deck. However, the
15 lengths of skateboards are typically in the range 76cm
(30 inches) to 86cm (34 inches) and have their sets of
truck fixing holes spaced apart by different lengths.
It is desirable that the hull 111 should be attachable
to skateboard decks of different lengths in this range.
20 The slots 114 allow mounting bolts, for example self
tapping screws, to be inserted anywhere along the length
of the slots 114, thus enabling the hull 111 to be
secured to a skateboard having lengths in a predetermined
range. Skateboards of different lengths have different
25 distances between their sets of truck mounting holes and
so the slots 114 accommodate these different distances.
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The hull 111 is preferably formed from polyethylene which
may be injection moulded around a foam core or
rotationally moulded. An elastomeric mounting gasket
(not shown) is preferably used to seal the hull 111 to
the underside of the skateboard deck, in order to prevent
the ingress of snow.
The hull 111 may also be adapted to be fixed to either
the wheels or the axles of a skateboard in order to
convert the skateboard into a snowdeck. The hull will
in this alternative be provided with attachment portions
for fixing to the skateboard wheels or axles,. preferably
without the use of tools.
Figure 12a shows a rider riding on a carving toboggan
120. The rider 3 is shown sitting on a platform 121
which is attached to a plurality of runners 122. The
runners 122 are similar to the carving faces 21, 23, 25
and running edges 31, 33, 35 of the snowdeck 1 but
combine the functionality of a carving face, a running
face and a recess face. The runners 122 are attached to
the platform 121 by means of a space frame 123. In
contrast to the snowdeck l, the surface area and
displacement of the runners 122 is such that a hull is
not required to prevent the runners 122 from sinking
excessively into snow.
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The centre of gravity of the rider 3 is relatively low
because the rider 3 is sitting down on the platform 121.
This enables the rider 3 to use greater angles of tilt
than are possible on a snowdeck. For example, runners
122 may be provided for use at a tilt angle of 55° off
vertical. The carving toboggan 120 is longer than a
typical snowdeck and this, together with the fact that
the rider 3 is sitting down, allows the carving toboggan
120 to be used on steeper pistes and thus at higher
speeds than the snowdeck. The higher speeds and the
greater angles of tilt are reflected in the curvature of
the runners 122.
Figure 12b shows a carving toboggan 125 that may be used
by a rider 3 either sitting down or standing up. Foot
straps 126 are provided to secure the rider 3 to the
carving toboggan 125 when he is standing up.
Figure 13 shows an ice skating boot 130 which is provided
with a straight blade 131 for travelling in a straight
line and with carving blades 132 for performing turns.
Whereas the hull 9 of the snowdeck 1 was shaped to
minimise the extent to which the hull 9 sank into snow
5, ice is much harder than snow and therefore the blades
131, 132 will not sink appreciably into ice. The
correspondence between the curvature of the carving
blades 132 and their angle of tilt is similar to that
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described for embodiment 1 except that the speeds
achievable on ice are significantly faster which is
reflected in the radii of the carving blades 132.
FURTHER EMBODIMENTS
The hull 9 was described as having an arcuate transverse
profile near to the end regions 27 and consequently had
a flatter profile at the centre of the hull 9. In an
alternative embodiment, a hull may be designed to have
an arcuate transverse profile in the centre with the
result that it will have a more pronounced (i.e more
sharply curved than at the centre, and thus resembling
a canoe more than the hull 9 of the first embodiment)
transverse profile at the ends of the hull. This
embodiment may be preferred in some circumstances but in
general is not preferred as it will tend to dig into snow
(rather than planing on top of the snow), thus suffering
increased friction.
The hull 9 was earlier described as having a generally
arcuate profile towards the end regions 27, and a flatter
profile at the centre of the hull 9. In an alternative
embodiment the hull need not have an arcuate profile that
is part of a circle but may instead have a profile that
is curved in some other way, for example an elliptical
profile. Whatever shape is chosen, a relatively flat
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profile will tend to be more stable and suitable for
beginners whereas a relatively sharply curved profile
will offer greater performance to experienced riders.
The hull 9 had carving faces 21, 23, 25 which were
designed for use at different speeds. In an alternative
embodiment, a hull is provided with carving faces which
are designed for use at a common speed. Such a hull may
be preferred for use on "slalom" type pistes, where a
rider will typically wish to execute carving turns of
different radii at a relatively constant forward
velocity.
The hull 9 was earlier described as being symmetric about
the longitudinal axis 15. In an alternative embodiment,
a hull has carving edges on one side that are different
from those on the other side. The carving edges may be
designed for different angles of tilt, different speeds
or for both different angles of tilt and different
speeds. Such a hull could be produced in left and right
handed versions to suit the riding style of riders. By
analogy, snowboards can be ridden in a conventional right
handed way (known as "regular" in which the rider's left
shoulder leads down the slope) or in a left handed way
(known as "goofy").
The two ends of the hull 9 were described earlier as
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being symmetric about the transverse axis 17. In an
alternative embodiment, the tilt, and angle of curvature,
of the carving faces is different at the two opposite
ends of the hull. This embodiment could be used to
5 provide a snowdeck suitable for both beginners and more
advanced riders. Beginners would place their centre of
gravity over the "low speed" end of the board to use the
region of the carving faces having tilts and curvatures
more suitable for beginners. More advanced riders would
10 place their centre of gravity over the "high speed" end
of the hull to use the region of the carving faces having
tilts and curvatures more appropriate to advanced riders .
Another benefit of the embodiment is that it would allow
slalom riders (who will generally travel at a rapid and
15 relatively constant speed) to change the radius of a turn
(whilst travelling at a constant speed) by moving their
centre of gravity forwards or backwards relative to the
deck). In such an embodiment the set of carving faces
at each end of the hull have their own respective radii
20 and tilts. In the region of the centre of the hull, the
two sets of carving faces join up and undergo a smooth
transition between the radii and tilts used at the
opposite ends. Thus, in such an embodiment, the carving
edges are no longer parts of a single cylinder but are
25 a combination of parts of two different cylinders with
a transition region between the two different ends.
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The hull 9 described above had a single straight surface
19 and three carving edges 21, 23, 25 on each side of the
surface 19. In alternative embodiments a smaller or
greater number of carving edges may be used on each side
of the longitudinal axis 15. In an alternative
embodiment, a single carving edge is provided on each
side of the longitudinal axis 15. In yet further
embodiments, a "left hand turn only" hull is provided
which has a single straight surface and one (or more)
carving edges (located on the same side of the surface
19) for performing turns. These embodiments can make
carving right handed turns only when the direction of the
board is reversed by the rider executing a 180° rotation
of the board.
The hull 9 had a single straight surface 19 which was
relatively wide. In an alternative embodiment the
straight surface 19 may be replaced by two carving and
running faces, the two carving faces being straight and
parallel. Alternatively, the two carving faces may be
slightly curved, one for performing very gentle turns to
the left and the other for performing very gentle turns
to the right. In such an embodiment, when the hull is
travelling in a straight line these two central gently
carving faces will to some extent conflict with each
other which may increase the friction. However, the
provision of these two gently carving faces may allow for
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improved high speed control in some embodiments.
The hull 9 was described as having integrally formed
carving faces and running faces. In an alternative
embodiment the carving faces and running faces are
replaceable to allow for their renewal if they become
excessively worn or so that the material of the carving
faces arid running faces can be selected to give optimum
performance for the snow (for example whether the snow
is powdery or compacted). In some circumstances it may
also be desirable to be able to replace the recess faces,
for example to change the footprint of the hull and hence
the depth to which it sinks in snow. The carving,
running or recess faces could be replaced either by
securing a piece of material to the faces or by using
replaceable runners which would be attached to the hull
rather than being integrally formed with the hull. A
replaceable runner would typically comprise a carving
face, a running face and a recess face. The use of
replacement runners would also allow beginners to upgrade
the profile of the runners, and thereby modify the tilt
and curvature to some extent, as their skill level
increases. The use of replacement runners would also
allow a hull to be used on a highly abrasive medium such
as sand.
The running faces 31, 33, 35 were earlier described as
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joining the carving faces 21, 23, 25 at right angles.
In alternative embodiments this angle may be less than
or greater than 90°. In yet further embodiments, the
running faces may be dispensed with so that the recess
faces meet their respective carving faces at an acute
angle. Although this yet further embodiment simplifies
the profile of the carving faces and recess faces, the
edges where the carving faces and running faces join may
be excessively prone to breakage and so they may need to
be manufactured from a strong material such as a metal,
for example steel.
The recess faces 41, 43, 45 were shown in Figures 6 and
7 as forming a straight line between their respective
carving faces and running faces. In alternative
embodiments the recess faces may be curved in transverse
profile. This curvature may be advantageously used to
control the extent to which a hull sinks into snow.
Similarly, the carving faces and the running faces may
also be curved in the planes XX' and YY' visible in
Figures 6 and 7 although it is preferred that they are
straight. The carving faces, running faces and recess
faces may be combined into other shapes, for example into
a semi-circular shape in transverse profile. What is
important is that the runner, whatever shape is used, is
able to support the weight of the rider and is able to
exert a reaction force to oppose the centrifugal and body
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forces exerted on the rider.
The hull 9 was described as being formed from
polyethylene. Other materials such as polypropylene,
other plastics, woods or metals are also suitable
although a factor to be borne in mind when selecting a
plastic is that it must not be excessively brittle at low
temperatures . Nylon is not preferred as it tends to have
excessive friction on snow. The blades 131, 132 of the
ice skating boot 130 or those of the carving toboggan 120
may be conveniently formed from a metal, for example
stainless steel, or even wood.
When a pair of ice skating boots 130 are used as a pair,
the blades 131, 132 on each boot will typically be
identical so that the only differences between the left
and the right boots will be so that they fit a left foot
and a right foot, respectively. In an alternative
embodiment, the blades 131, 132 of a pair of ice skates
are shaped so that they are mirror images of each other.
This allows for improved turning ability. For example,
consider a situation where an ice skater is following a
circular path to the right. The skate on the right foot
will follow a circular path having a slightly smaller
radius than the circular path followed by the skate on
the left foot. Consequently, in this alternative
embodiment, the carving blades 132 on the right hand side
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of the right foot are provided with a slightly smaller
radius of curvature than the carving blades 132 on the
right hand side of the left boot.
5 Carving toboggans were shown in relation to Figures 12a
and 12b. In an alternative embodiment, the runners 122
of the carving toboggans are narrowed so that they become
blades, thus providing a carving bobsleigh for use on
bobsleigh tracks.
In another embodiment, a modified carving toboggan is
fitted for use as the front ski of a skidoo or
snowmobile, thereby improving the steerability of the
skidoo or snowmobile to which it is fitted. Such a
modified carving toboggan may be provided with mounting
fixtures so that it can be used to replace and thereby
upgrade the front skis of the skidoo or snowmobile.
"Inline" skates are well known for use on, for example,
grass or concrete and comprise several small wheels
mounted one behind the other and having parallel axes.
Whereas the previous embodiments were suitable for use
on media such as snow, sand and ice, in an alternative
embodiment inline wheels are used so that the alternative
embodiment can be made to turn on, for example, grass or
concrete by tilting it appropriately. In this
alternative embodiment the straight surface 19 is
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replaced by inline wheels and the carving edges 21, 23,
25 and their associated running edges 31, 33, 35 are
replaced by wheels which rather than being in line are
angled so that their axes are tangential to a circular
arc. As before, these circular arcs are tilted so that
the user of this alternative embodiment can make a turn
by tilting the embodiment so that the inline wheels are
lifted off the ground and the apparatus is instead
supported by a set of wheels arranged around an arc.
