Skateboard

When the front truck of a skateboard is offset laterally to the right from the rear truck, the rider can transfer his weight from the rear truck to the front truck when making a right turn and from the front truck to the rear truck when making a left turn. The truck whose weight is augmented turns through a larger angle than otherwise possible. At some point as the rider leans farther and farther into a right turn, the left rear wheel leaves the ground; the right front wheel leaves the ground when the rider leans strongly into a left turn. When either of these wheels leave the ground, the skateboard steers in a tricycle mode and is capable of extremely sharp turns. The board includes a front portion which is offset from the rear portion, and this offset encourages the rider to assume a more normal stance on the board.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention is in the field of sporting goods, and more 
particularly relates to a skateboard that is unusually maneuverable. 
2. The Prior Art 
An Information Disclosure Statement has been lodged in the file of this 
application. All of the references discussed in it are believed to be 
distinguishable from the present invention. 
The earliest skateboards were made by attaching the front part of a roller 
skate to the front portion of a board and attaching the rear part of a 
roller skate some distance away at the rear portion of the board. These 
relatively primative skateboards were difficult to turn and stopped 
abruptly when any of the wheels encountered a small rock. 
The next step in the evolution of the skateboard came with the introduction 
of independent trucks. The trucks include two wheels and an axle along 
with a base including resilient members, by which the axle is attached to 
the board. This board used relatively narrow trucks and was successful in 
emulating the feeling of a surfboard. However, because of the narrowness 
of the skateboard, the rider's toes and heels extended laterally beyond 
the edge of the skateboard, and this resulted in injuries to the rider. A 
wider board was needed. 
In response to this need for a wider board, boards as wide as 10 or 12 
inches then became popular. These wider boards permitted the rider to 
assume a more normal stance with one foot extended slightly in front of 
the other foot in the lateral direction on the skateboard. However, the 
wider trucks used with the wider boards prevented these boards from 
turning sharply. In order to make sharper turns with these boards, riders 
learned to apply weight to the portion of the board extending rearward of 
the rear truck, thereby causing the front wheels to leave the ground, 
while the rider pivoted on the rear wheels. These boards lacked the 
feeling of a surfboard, but were an improvement over earlier skateboards. 
SUMMARY OF THE INVENTION 
A major objective of the present invention is to provide a skateboard that 
has the feel of a surfboard. 
Another objective of the present invention is to provide a skateboard that 
permits the rider to have greater stability. 
Another objective of the present invention is to provide a skateboard 
capable of making relatively sharp turns. 
These objectives were achieved in accordance with the present invention by 
offsetting the front truck laterally with respect to the rear truck and by 
using trucks in which the separation between the wheels is approximately 6 
inches for a skateboard that is 31 inches long. 
Offsetting the front truck laterally with respect to the rear truck 
encourages the rider to use a more stable stance, which is more like the 
stance used on a surfboard. 
Although some improvement in turning had been expected from the use of the 
narrower trucks, the degree of improvement far exceeded expectations. It 
was found that during sharp turns, one of the four wheels would leave the 
ground and the board then steered like a tricycle in making the sharp 
turns. 
This effect has not been observed on boards lacking the offset trucks of 
the present invention, and thus the phenomenon appears to be inherent in 
the present invention. 
These and other advantages of the present invention will be discussed below 
in connection with the detailed description of a preferred embodiment in 
relation to the drawings. However, the drawings are for the purpose of 
illustration and explanation, and are not intended to limit the scope of 
the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIGS. 1, 2 and 3 relate to a common type of skateboard known in the prior 
art. That type of skateboard includes a board 12 to the underside of which 
are mounted the trucks 14, 16. As is well known in the art, these trucks 
include the two wheels, and their axles. The wheel and axle assembly is 
mounted to a base that is bolted to the board 12. The base includes 
resilient elements that absorb road shocks and also provide a restoring 
force that opposes directional changes of the axles. 
As shown in FIG. 2, when the skateboard is in the unloaded condition, the 
axles 18, 20 are directed laterally of the skateboard. When the skateboard 
is loaded and the rider distributes his weight more to one side of the 
board than to the other, the weighted side is pushed down as indicated in 
FIG. 3 and the opposite side comes up. This pivoting of the skateboard 
about a longitudinal axis causes the axles 18, 20 to rotate to the 
positions shown in FIG. 3. This is the configuration of the skateboard 
when the rider is executing a turn. If the turn is too sharp, the outside 
wheels 22, 24 lift off the ground, and typically the skateboard skids 
toward the outside of the turn on the remaining two wheels. When a 
skateboard is skidding, it is out of control. 
It is important to note that in the prior art skateboard of FIGS. 1-3, the 
trucks were mounted on the same longitudinal line, so that the rear wheels 
would follow in the tracks of the front wheels when the board is being 
ridden in a straight line. 
In contrast, in the present invention, as shown in FIGS. 4 and 5, the front 
truck is laterally offset with respect to the rear truck. 
Just as some people are right-handed and others are left-handed, it has 
been found that some people prefer to stand on a skateboard with their 
left foot leading in the direction of motion, while others prefer to face 
the opposite direction so that their right foot leads in the direction of 
motion. To accommodate these two ways of riding the skateboard, it is 
necessary to provide the left-foot-forward embodiment of FIG. 4 and its 
mirror image, the right-foot-forward embodiment of FIG. 5. 
As seen in FIG. 4, the skateboard includes a board 28 that has a front 
portion 34 and a rear portion 36. In the best mode of practicing the 
invention, the front portion 34 of the board is offset from the rear 
portion 36 of the board. This encourages the rider to place his feet on 
the board in such a way that the left foot shown by the phantom lines 30 
is slightly extended from the right foot shown by the phantom lines 32. 
The front truck 38 is mounted to the underside of the front portion 34 of 
the board 28. 
An imaginary plane 46, seen edge-on in FIG. 4, passes midway between the 
wheels of the front truck 38. In the best mode of practicing the 
invention, the rear truck 40 is mounted on the rear portion 36 of the 
board 28 in such a position that the plane 46 passes through the center of 
the right rear wheel 50. If the distances between the centers of the front 
wheels 42, 48 is 2d, then in the best mode, the offset should be d. 
In other embodiments, other amounts of offset can be used. 
As best seen in FIG. 5, the front axle 37 retains the right front wheel 42 
and the left front wheel 48 in coaxial alignment, so that the axis 29 of 
the right front wheel 42 coincides with the axis 31 of the left front 
wheel 48. Similarly, the rear axle 39 retains the right rear wheel 50 and 
the left rear wheel 44 in coaxial alignment, so that the axis 33 of the 
right rear wheel 50 coincides with the axis 35 of the left rear wheel 44. 
The front axle 37 is mounted to the board 28 by the front base 41 and the 
rear axle 39 is mounted to the board by the rear base 43. The front base 
41 permits limited resiliently-opposed pivotal motion of the front axle 37 
with respect to the board about the axis 45 which extends downwardly to 
the front. Similarly, the rear base 43 permits limited resiliently-opposed 
pivotal motion of the rear axle 39 with respect to the board about the 
axis 47 which extends downwardly to the rear. This type of mounting of the 
axles 37, 39 to the board is well-known and accounts for the steering 
effect shown in FIG. 3. 
Offsetting the front truck laterally with respect to the rear truck causes 
the vertical force applied to the trucks to vary depending on whether the 
rider is making a right turn or a left turn. This is best seen with 
reference to the diagram of FIG. 6. 
In FIG. 6 the board 28 is assumed to be supported by the front truck at the 
location 60 and by the rear truck at the location 62. The location 62 is 
offset laterally from the location 60 by the distance d. 
Assume the rider is making a right turn and therefore is leaning to the 
right and shifting his weight to the balls of his feet rather than 
supporting himself equally on the balls of his feet and his heels. It is 
assumed that the balls of his feet are located at the positions 64, 66, 
each of which is offset from its corresponding truck by the distance a. It 
is also assumed that the rider is distributing his weight equally between 
his left foot and his right foot. 
The force vectors at the lower portion of FIG. 6 show the equal forces 
F.sub.1 and F.sub.2 exerted by the rider's feet on the board. These forces 
must be countered by the upward reaction of the trucks, as indicated by 
the vectors R.sub.1 and R.sub.2. Since F.sub.1 and F.sub.2 are assumed to 
be equal and are shifted to the right from R.sub.1 and R.sub.2, it is 
necessary for R.sub.2 to be greater than R.sub.1 if the torques applied to 
the board are to be balanced. This is borne out by analysis, from which it 
can be shown that: 
for a right turn, 
##EQU1## 
and for a left turn, 
##EQU2## 
for F equals F.sub.1 equals F.sub.2. 
These equations show that when the rider divides the weight on his left 
foot equally between his heel and the front part of the foot so that the 
center of pressure is on a longitudinal line passing through the point 60 
and so that the center of pressure of his right foot is located on a 
longitudinal line through the point 62, a equals 0, and equal amounts of 
force are applied to the front and rear trucks. 
As the rider leans more toward to the right, a starts to increase, and a 
shift in the forces applied to the trucks becomes evident. The downward 
force on the front truck increases, and the downward force on the rear 
truck decreases. When a equals half the offset distance d, all of the 
force is on the front truck and the rear truck is unloaded. 
Likewise, for a left turn, the rider shifts his weight to his heels, and 
the result is that the rear truck becomes more heavily loaded, while the 
front truck is more lightly loaded. 
The reality of this phenomenon has been verified experimentally. As the 
rider in making a right turn leans farther and farther to the right, an 
ever-increasing fraction of the weight is borne by the front truck 38. A 
point is reached when there is so little weight on the rear truck that the 
left rear wheel 44 leaves the ground, and the skateboard runs on the 
wheels 42, 48, and 50. Under these conditions, the skateboard is steering 
like a tricycle and consequently is capable of very sharp turns. In the 
extreme situation where all of the weight is borne by the front truck 38, 
both rear wheels leave the ground and the front axle is at an extreme 
angle with respect to the direction of motion, producing an extremely 
sharp turn. Even when the skateboard is operating in the tricycle mode, 
the rear wheel 50 may be so lightly loaded that it skids laterally, again 
promoting a very sharp turn. 
As the above equations indicate, in a left turn, the rider's weight is 
transferred to the rear truck 40, and the front truck 38 is only lightly 
loaded. Further leftward leaning by the rider causes the right front wheel 
42 to leave the ground. 
Clearly, similar considerations apply to the right-foot-forward skateboard 
shown in the embodiment of FIG. 5. 
The above equations are based on the assumption that the rider divides his 
weight equally between his left foot and his right foot. However, it is 
believed that because the left foot is placed ahead of the right foot in 
FIG. 4, that as the rider leans to the right, he will tend to put more of 
his weight on his left foot. This further increases the effect analyzed 
above, by applying even more force to the front truck as the rider makes a 
right turn and by applying even more force to the rear truck as the rider 
executes a left turn. This additional effect is a result of the shape of 
the board 28, which encourages the rider to stand with his left foot 
slightly forward of his right foot, as shown in FIG. 4. 
Thus, there has been described a skateboard that is capable of making very 
sharp turns without having to be "kicked". The result is a skateboard that 
more nearly simulates the feeling of a surfboard. In accordance with the 
invention, offsetting the front truck laterally from the rear truck 
results in the rider's weight being transferred from the front truck to 
the rear truck as the rider executes turns. This results in the ability to 
make very sharp turns. 
The foregoing detailed description is illustrative of an embodiment of the 
invention, and it is to be understood that additional embodiments thereof 
will be obvious to those skilled in the art. The embodiment described 
herein together with those additional embodiments are considered to be 
within the scope of the invention.