US20190351314A1

US20190351314A1 - Lean-steered mountain board and method of operation

Info

Publication number: US20190351314A1
Application number: US16/393,679
Authority: US
Inventors: Alan K Lewis
Original assignee: Individual
Current assignee: Individual
Priority date: 2018-03-30
Filing date: 2019-04-24
Publication date: 2019-11-21

Abstract

According to an embodiment, a wheeled vehicle is provided, which includes a frame supporting a rear wheel, a rider's deck, and a steering post lying parallel to a longitudinal axis of the vehicle. A front axle is coupled to the frame and configure to rotate about the steering post while remaining perpendicular to the longitudinal axis. Axle stubs are coupled to respective ends of the axle so as to be pivotable relative to the axle, and front wheels are rotatably coupled to the axle stubs. A steering mechanism is configured to permit a rider to steer the vehicle by leaning on the rider's deck.

Description

BACKGROUND

Field of the Invention

This invention relates to mechanisms and methods for steering leaning wheeled vehicles used primarily for personal transportation. The embodiment described below is in the class of three- and four-wheeled vehicles with mechanical assemblies that allow all of the wheels to lean into turns. In particular, the present invention relates to skateboards and their more focused downhill derivatives, mountain boards, whether unpowered or powered.

Related Art

Typical modern skateboards turn through the use of skateboard trucks. A skateboard truck consists of a solid axle built into a metal housing. The metal housing is mounted onto a base plate with a rigid pivot with an axle into a bearing and a flexible pivot supported by some form of compressible bushing. Each pivot axis is angled toward the wheel axle of the truck, forming roughly a triangular shape. The trucks are mounted to the skateboard such that the rigid pivot of the front axle is towards the front of the board and the rigid pivot of the rear axle is towards the back of the board. As the rider leans the skateboard, the inner bushings compress, and the trucks turn about their rigid pivots. The wheels on the side the rider is leaning towards are moved closer together and those on the other side move further apart. The result is that the inner and outer wheels now lie along concentric circular paths, rather than running parallel as they do in the neutral position. Therefore, by leaning the board to the right, the rider turns the board right, and vice-versa.

SUMMARY OF THE INVENTION

According to an embodiment, a vehicle is provided comprising a riding deck, one central rear wheel, and two front wheels. Through a mechanical assembly, the wheels and the deck lean into curves and turns. The herein described vehicle enables the rider to lean with the deck and the wheels to provide a simple and natural method of steering. A spring element provides a force to restore the deck to a neutral and level position following the completion of a turning maneuver, assisting the rider to maintain balance and control of the vehicle. A mechanical linkage leans the wheels as the deck leans into a turn, maintaining a relation between deck angle, wheel angle, and steering radius, enabling consistent, controllable lean steering.
According to an embodiment, the vehicle of the present invention combines the large pneumatic tires of a typical mountain board with a fairly simple steering linkage. This combination gives the vehicle the on and off-road capabilities of existing mountain boards while allowing for much smaller turning radii and better handling in general. The vehicle may be unpowered or may be powered, for example, by an electric motor driving the rear wheel or wheels.
These and other features and advantages of the present invention will be more fully appreciated from a reading of the following detailed description with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a mountain board, according to an embodiment.

FIG. 2 is a top plan view of the mountain board of FIG. 1

FIG. 3 is a bottom plan view of the mountain board of FIG. 1.

FIG. 4 is a side elevation view of the mountain board of FIG. 1.

FIG. 5 is a perspective view of a mountain board frame, according to an embodiment.

FIG. 6 is a perspective view of the mountain board of FIG. 1 in a turn configuration.

FIG. 7 is a perspective view of a front axle/steering assembly and a portion of a frame of a mountain board, according to an embodiment.

FIGS. 8 and 9 are respective front perspective views of the mountain board of FIG. 1 with selected elements omitted or cut away to more clearly show other selected details.

FIG. 10 is a side view of the front axle/steering assembly and frame of FIG. 7.

FIG. 11 is a front perspective view of a four-wheeled mountain board, according to an embodiment.

FIG.12 is a front elevation view of a portion of a mountain board that includes a steering return assembly, according to an embodiment.

DETAILED DESCRIPTION

In the description that follows, various elements are described as being coupled together. Generally, coupling elements such as nuts, bolts, screws, welds, adhesives, etc., are not described in detail, and in some cases are not shown in the drawings. Such elements are very well understood by persons of ordinary skill in the art. It will also be understood that in many cases, there are many alternative fasteners or fastening methods that can be used. Finally, it will be understood that in some cases, a single component can be made that incorporates the functions of multiple elements. Accordingly, except where a claim recites specific details of a faster, or explicitly defines one or more elements as being physically distinct from other elements, the claims are not limited to the specific arrangements and configurations disclosed herein.
In the drawings, some elements are designated with a reference number followed by a letter, e.g., “146 a, 146 b, 146 c.” In such cases, the letter designation is used where it may be useful in the corresponding description to to refer to or differentiate between specific ones of a number of otherwise similar or identical elements. Where the description omits the letter from a reference, and refers to such elements by number only, this can be understood as a general reference to the elements identified by that reference number, unless other distinguishing language is used.
As used herein, the term ground plane refers to a notional surface on which the disclosed mountain board operates, and is defined, where appropriate, as an X-Y plane PG (shown in FIGS. 4, 8, and 9) that contacts the bottom-most points of each of the wheels, assuming the board to be oriented as it would be during normal operation. The term is used primarily for clarity in describing and defining aspects of the various embodiments. Likewise, in the claims, the term is intended as a plane of reference, only.
FIG. 1 is a perspective view of a mountain board 100, according to an embodiment, FIG. 2 is a top plan view of the mountain board, FIG. 3 is a bottom plan view of the board, and FIG. 4 is a side elevation view. The board 100 includes a deck assembly 102, a rear wheel assembly 104, a front wheel assembly 106, and a brake assembly 108.
Referring to FIGS. 1-4, the deck assembly 102 includes a frame 110, a deck 112, and a fender 113. The Rear wheel assembly 104 includes a rear wheel 114 a rotatably mounted on an axle 116 extending between arms 118 of the frame 110. The rear wheel assembly 104 also includes a hub, bearings, fasteners, etc., such as are well known in the art. The front wheel assembly 106 includes a pair of wheels 114 b, together with respective hubs and bearings, each rotatably and steerably mounted to a front axle/steering assembly 120, as will be described in detail with reference to FIGS. 6-10, below. According to an embodiment, the front and rear wheels 114 are pneumatic.
The front axle/steering assembly 120 is coupled to the frame 110 and configured to rotate, relative to the frame, about a first axis A₁lying parallel to a Y-axis of the board 100. The brake assembly 108 includes a brake rotor 122 rigidly coupled to the rear wheel 114 a and configured to rotate therewith about the axle 116, a caliper 124 coupled to an arm 118 of the frame 110 and configured to selectably apply braking force to the rotor 122, and a braking control assembly 126. The braking control assembly 126 includes a brake control handset 128, a brake cable 130, and a handset tether 132. The brake cable 130 is coupled at a first end to the brake caliper 124 and at a second end to the handset 128. In the embodiment shown, the brake cable 132 passes through a portion of the frame 110 and emerges near the rear wheel 114 a and the brake rotor and caliper 122, 124. The braking control assembly 126 is configured such that when an operator applies a squeezing force to a brake control lever 134 of the handset 128, so as to change a relative angle of the brake control lever and a handle 135 of the handset, the brake cable 130 transmits a corresponding force to the brake caliper 124, which in turn applies a braking force to the brake rotor 122 that is proportionate to the squeezing force applied to the handset. The handset tether 132 is coupled at a first end to the handset 128 and at a second end to a tether link 133 that is coupled to the frame 110, and is joined along most of its length to the tether 132. The tether 132 is configured to protect the brake cable 130 from tension and other forces applied by the operator to the handset 128 during operation of the mountain board 100 that might otherwise damage the cable.
FIG. 5 is a perspective view of the frame 110, according to an embodiment. Referring to FIGS. 3 and 5, the frame 110 has a rear fork 136 coupled to a tubular frame rail 138 extending longitudinally from the fork, and a steering post 140 at the front end of the frame rail. Deck mounts 142 are welded or otherwise affixed to the frame rail 138, and are configured to receive the deck 108 coupled thereto via fasteners 144, which extend through holes in the deck and corresponding holes 146 a in the deck mounts. The rear fork 136 comprises a pair of arms 118 with respective wheel mounting tabs 148 having apertures 146 b configured to receive the axle 116 of the rear wheel 114 a. One of the wheel mounting tabs 148 a also includes caliper apertures 146 c sized and positioned to receive fasteners mounting the caliper 124 to the corresponding wheel mounting tab 148 a.
In the embodiment shown, a torsion plate 150 is coupled to the frame rail 138 close behind the steering post 140 extending forward over the steering post, and a steering linkage block 152 is coupled to the torsion plate. Gusset plates 154 are coupled to the frame rail 138 and the steering linkage block 152, providing additional strength and stiffness to the linkage block and the torsion plate 150. The torsion plate 150 includes a transverse aperture 156, while the linkage block 152 includes one or more longitudinal threaded apertures 158.
The brake cable 130 extends the length of the tubular frame rail 138, exiting at the rear end of the frame rail between the legs 118 of the rear fork 136, whence it is coupled to the brake caliper 124.
The frame 110 is formed to conform to a shape of the deck 112 and to support the front axle/steering assembly 120 in position, relative to the deck and rear wheel assembly 104. Accordingly, in the embodiment shown, while the steering post 140 and frame rail 138 each lie parallel to the Y axis, the steering post is offset, relative to most of the frame rail, with the front end of the frame rail transitioning through a series of bends to the axis A₁on which the steering post lies. Additionally, the rear fork 136 extends from the end of the frame rail 138 at a slight angle, relative to the Y axis, so that the axle 116, extending between the apertures 146 b of the wheel mounting tabs 148, intersects the axis A₁(see also FIG. 4). This arrangement positions the upper surface of the deck 112 at about the same height as the axles of the wheels 114, although in other embodiments, the deck can be higher or lower than shown. By positioning the upper surface of the deck 112 at or below the axis A₁, stability of the mountain board 100 is improved.
According to an embodiment, the frame rail 138 and steering post are formed together from a single piece of tubular material, while the fork 136 is formed from another piece of tubular material, and coupled—via, e.g., welding—to the rear end of the frame rail.
The front axle/steering assembly 120 and the operation of the mountain board are described hereafter, according to various embodiments, with reference to FIGS. 6-10. FIG. 6 is a perspective view of the mountain board 100 in a turn configuration. FIG. 7 is a perspective view of the front axle/steering assembly 120 and a portion of the frame 110, while FIGS. 8 and 9 are respective front perspective views of the mountain board 100 with selected elements omitted or cut away to more clearly show details of the front axle/steering assembly. In FIG. 8, the board 100 is shown with the front wheels centered, so as to travel along a straight line, while FIG. 9 shows the mountain board in a turn configuration. FIG. 10 is a side view of the front axle/steering assembly and frame, with the position of the front wheels 114 b shown in phantom lines.
The front axle/steering assembly 120 includes a front axle 160 rotatably coupled to the steering post 140 via a steering tube 162, which is fixed to the front axle. In the disclosed embodiment, the steering tube 162 is rotatably coupled to the steering post 140 of the frame 110 in a manner that is similar, in many respects, to the way in which the steerer tube and head tube of a bicycle headset are coupled, which permits rotation of the front bicycle forks of a bicycle without significant wobble or play. Accordingly, some of the same terms are used to simplify the description. Nevertheless, while the pivot structure is similar, the operation is quite distinct. Furthermore, the mechanism described is merely one example; other embodiments are also contemplated. As shown, in particular, in FIG. 10, a crown race 164 is positioned innermost on the steering post 140, after which are positioned, in order, an inner bearing race 166, an inner bearing (not visible), an inner race cup 168, the steering tube 162, an outer race cup 170, an outer bearing (not visible), a threaded bearing race 172, a head washer 174, and a head nut 176.
Spindle brackets 178 are coupled to opposite ends of the front axle 160, and spindles 180 are rotatably affixed to the spindle brackets via spindle bolts 182. The spindle bolts 182 define respective steering axes A₂, i.e., the axes around which the wheels are pivoted to steer the board 100. In the embodiment shown, the steering axes A₂, are angled forward relative to a Z-axis. which produces a positive angle. A caster angle of a vehicle suspension is determined by the angle or position of the steering axis relative to a vertical axis A₃extending through the rotational axis of the wheel. In a wheel suspension with a positive caster angle, the steering axis is angled or positioned, relative to the direction of travel, so that the steering axis intersects a ground plane on which the wheel travels ahead of the wheel. Conversely, with a negative caster angle, the steering axis intersects the ground plane behind the wheel. In the embodiment shown, the front axle/steering assembly 120 has a positive caster angle CA of about 37 degrees, relative to the vertical axis A₃. A high positive castor angle on the front wheels 114 b tends to bias the vehicle steering toward a centered position, with a higher caster angle producing a correspondingly higher return bias. According to an embodiment, a high caster angle CA provides a first mechanism that tends to urge or move the steering toward center.
Comparing FIGS. 9 and 10, it can be seen that the caster angle CA also controls the degree to which the wheels 114 b tilt into a turn. Tilting the wheels into a turn can improve contact between the wheels and the ground plane and help maintain traction against lateral forces on the wheels. A higher positive caster angle CA produces a correspondingly greater wheel tilt for a given steering angle, i.e., the angle of rotation of the spindle 180 about the steering axis A₂.
The caster angle CA can be selected according to a desired amount of steering return bias and/or according to a desired degree of wheel tilt for a given angle steering angle. According to respective embodiments, the front axle/steering assembly 120 has a positive caster angle CA of at least five degrees, at least fifteen degrees, and at least thirty degrees.
Referring in particular to FIGS. 7 and 8, a tie rod 184 is coupled at each end to a steering arm 186 of a respective one of the spindles 160. Each of the spindles also includes an axle stub 188 configured to rotatably receive one of the front wheels 114 b. A drag link 190 is coupled at a first end to the steering arm 186 of one of the spindles 180 a, and at the other end to the steering linkage block 152, via a threaded fastener 192 extending through a drag link end and into a threaded aperture 158 of the steering linkage block.
A steering return assembly 194 is coupled to the torsion plate 150 and the front axle 160, and is configured to apply a centering bias to the front axle/steering assembly 120 tending to return the front wheels 114 b to a centered condition. As shown, in particular, in FIGS. 8 and 9, the steering return assembly 194 includes a coupling rod 196 coupled at a first end to the torsion plate 150, and at a second end to a coupling link 198 that is pivotably coupled at one end to the coupling rod 196 and at the other end to the axle 160. The first end of the coupling rod 196 is threaded, and extends through the transverse aperture 156 of the torsion plate 150. Elastomeric bushings 200 are positioned on the first end of the coupling rod 196 on opposite sides of the torsion plate 150, with washers or pivot cups 202 against the outer faces of the bushings. Nuts 204 are threaded onto the first end of the coupling rod 196 against the washers 202 so as to apply a preloading bias to the bushings 200.
The hardness, or durometer, of the bushings 200 can be selected to provide a desired degree of performance and stability. As will be discussed later, in view of the operation of the front axle/steering assembly 120, bushings with a relatively higher durometer will provide higher stability, while softer bushings will provide better responsiveness. According to an embodiment, the bushings 200 have a durometer of between 65 a and 100 a (Shore A).
The tether link 133 is coupled to the back side of the steering linkage block 152 by a threaded fastener. The tether link 133 has an aperture in which an elastomeric grommet 210 is positioned. A lower end of the handset tether 132 is coupled to the tether link 133 via the aperture and grommet 210, as shown, for example, in FIG. 6.
The steering return assembly 194 provides a second mechanism that tends to move or hold the steering of the board 100 at a straight and centered position: while the front wheels 114 b are centered, as shown in FIG. 8, the torsion plate 150 is vertical and substantially parallel with the washers 202, and the bushings 200 apply a balanced bias against the torsion plate from either side. However, when the torsion plate 150 rotates relative to the axle 160, the coupling rod 196 is also pushed or pulled in the same direction. Meanwhile, the coupling link 198 keeps the coupling rod 196 parallel with the axle 160 and the washers 202 substantially perpendicular to the axle. As a result, the bushings 200 are each compressed on one edge by the angled torsion plate 150 between the vertical washers 202, as shown in particular in FIG. 9. This produces a strong bias urging the torsion plate 150 back to center and vertical. The strength of this bias can be modified by selection of the size, shape, and durometer of the bushings 200.
In operation, an operator steers the mountain board 100 by unbalancing a weight distribution on the deck 112 to tilt the deck. When the operator tilts the deck 112 to one side or the other, the deck rotates, relative to the steering assembly 120, about the steering post 140. This causes the torsion plate 150, which is fixed to the frame 110 just behind the steering post, to rotate, relative to the axle 160, carrying with it the steering linkage block 152, as shown in FIG. 9. The drag link 190, which is coupled to the steering linkage block 152, is pushed or pulled by the block in the direction of the tilt, pulling or pushing the steering arm 186 of the spindle 180 a, causing both spindles 180, which are linked together by the tie rod 184, to rotate about their respective spindle bolts 182. For example, in order to turn right, the operator applies more weight to the right side of the deck 112 than to the left side. In response, the deck 112 tilts to the right, and the spindles 180, together with the front wheels 114 b, turn to the right, as shown, for example, in FIGS. 6 and 9. Conversely, applying more weight to the left side of the deck 112 will cause the deck to tilt leftward as the front wheels turn to the left.
As noted above, when the operator tilts the deck 112, the front end of the deck rotates about the steering post 140, relative to the front axle/steering assembly 120 and the wheels 114 b. This permits the wheels 114 b to remain in full contact with the ground plane, although the front axle 160 does not remain parallel to the ground plane P_G. Because the spindle bolts 182 are angled forward, as described above, when the spindles 180 pivot about their respective steering axes A₂, the axle stub 188 of the spindle on the inside of the turn is tilted downward as it pivots, while the axle stub on the outside is tilted upward. This tilts the front wheels 114 b into the turn and causes the axle 160 to tilt slightly away from the turn, as best shown in FIG. 6. The rear wheel 114 a, meanwhile, tilts with the deck 112 into the turn. Thus, when the operator tilts the deck 112, the axis A₁does not remain parallel to the ground plane P_G, but tilts downward, and the deck rotates, relative to the ground plane, about an axis A₄that angles downward from the steering post 140 to a point at which the rear wheel 114 a contacts the ground plane (see FIG. 4). Therefore, when the operator stands near the front of the deck 112, the operator's weight is at about the same height as the pivot angle A₄, but as the operator moves toward the rear of the deck, the weight is positioned at an increasingly greater distance above the pivot angle. Accordingly, operation of the mountain board 100 is most stable with the operator's weight near the front of the board 100, and least stable with the weight near the rear. On the other hand, the board 100 is most responsive when the operator stands near the rear, being more sensitive and responsive to small changes of weight distribution. An operator with less experience may therefore tend to stand near the front, for stability and ease of control, while a more experienced operator may stand further back, for agility and responsiveness. An operator may also move forward or back on the deck 112 according to the terrain and vehicle speed.
According to an embodiment, the steering linkage block 152 includes a single threaded aperture 158, as shown, for example, in FIG. 10. According to another embodiment, the steering linkage block 152 includes two or more threaded apertures 158 in a vertical row, as shown, for example, in FIG. 9. Embodiments that include multiple threaded apertures 158 enable an operator to select between multiple levels of steering control. For example, an operator may choose to couple the drag link 190 to the steering linkage block 152 via an aperture 158 that is relatively close to the pivot axis of the steering post 140. This will result in smaller movement of the drag link for a given angle of the torsion plate 150, and consequently smoother, shallower turns, and greater stability of the board 100. This setting might be preferred for a novice rider, or for use at higher speeds. Alternatively, the operator might choose to couple the drag link 190 to the steering linkage block 152 via an aperture 158 that is a greater distance from the pivot axis of the steering post 140. This will result in larger movement of the drag link for a given angle of the torsion plate 150, and consequently sharper turns and less stability of the board 100. This setting might be preferred for use at slow speeds, or where agility is preferred, such as on mountain trails, etc. According to another embodiment, the same adjustments are made by coupling the opposite end of the drag link to the steering arm 186 of the spindle 180 a at a point closer or further from the spindle bolt 182.
In the embodiments described above, there are two linked mechanisms associated with steering the mountain board: the first is the mechanism for control of the steering pivot angle of the wheels, the second is the mechanism for control of the tilt of the deck. In the embodiments described above, these two mechanisms are coupled, because the steering linkage block 152 is rigidly coupled to the torsion plate 150. However, the inventor contemplates an embodiment in which these mechanisms are decoupled. For example, according to an embodiment, the torsion plate 150 remains directly coupled to the steering tube 162, enabling the operator to tilt the deck 112 by shifting weight, with the steering return assembly acting to return the deck to a level condition. Meanwhile, the the steering linkage block 152 is independently rotatable relative to the steering post 140, and is controlled, for example, by a tiller that the operator manipulates. This enables the operator to tilt the deck 112 to the left, for example, while turning to the right. Such independent control might be desirable where the operator wishes to be able to perform drift turns, or to control the relative degrees of tilt vs. turn.
FIG. 11 is a front perspective view of a four-wheeled mountain board 220, according to an embodiment. The board 220 is similar in most respects to the board 100 described above. However, the board 220 includes a a front axle/steering assembly 120, substantially as described, but also includes a a rear axle/steering assembly 222, which is similar to the front axle/steering assembly except that it is oriented in the opposite direction, and so steers the rear wheels in the direction opposite the front wheels. Though not shown, according to an embodiment, the board 220 is provided with a brake assembly similar to that described above, with brake rotors coupled so as to rotate with at least two of the wheels 114, and calipers fixed to the corresponding spindles 180.
FIG. 12 is a front elevation view of a portion of a mountain board 230 that includes a steering return assembly 232, according to an embodiment. The return assembly 232 includes a torsion block 234 supported by gusset plates 236. The torsion block 234 combines the functions of the torsion plate 150 and the steering linkage block 152 described above with respect to previous embodiments. The torsion block includes a threaded aperture 158 to which the drag link 190 is coupled. Additionally, steering return springs 238 are coupled to the torsion block 234 and extend toward the axle 160 on respective sides of the torsion block. Each of the steering return springs 238 includes an air spring 240—a sealed rubber cylinder filled with a gas, such as air, etc. The air springs 240 rest against the axle 160, such that rotation of the torsion block 234 relative to the axle 160 compresses one or the other of the air springs against the axle.
During use, when the deck 112 is tilted to one side, the angle between the torsion block 234 and the axle 160 changes, resulting in the compression of the air spring 240, on that side, against the axle 160. The compressed air spring 240 applies a return bias to the torsion block 234. According to another embodiment, solid elastomeric bushings or blocks are used in place of the air springs 240 to provide the spring bias.
The inventor has recognized a number of deficiencies of typical skateboard systems, particularly those that are adapted for use in rough terrain, mountain slopes, unimproved trails, etc. First, most skateboard trucks cannot provide a small turning radius, while use in trail and mountain operation often requires that an operator make very sharp turns. To a certain extent, skateboard trucks can be modified or manufactured to enable a smaller turning radius, but this is relative: available minimum turning radii range from around 15 feet down to around six feet, but even six feet is often too large. Consequently, the board has to be picked up to get around tight turns. Picking a board up presents physical challenges to the rider, and can be a nuisance, depending on the frequency at which the rider must do so. Additionally, reducing the turning radius of a mountain board that employs traditional trucks involves a loss of mechanical advantage that can increase the associated difficulty and danger of operating such a device.
For example, a typical skateboard and trucks setup might enable the skateboard truck axle to rotate 5 degrees and achieve a turning radius of 15 feet when the deck is tilted 10 degrees. Thus, on average, for every degree of tilt, a half degree of steering change is produced, and the operator has a mechanical strength advantage of 2:1. This is beneficial because it helps the operator resist unintended steering changes caused by road obstructions. For example, a wheel dropping into a depression in the road might resist forward movement of the wheel, resulting in a turning force applied to the axle pivot. The operator resists the force by applying an offsetting counter force in the opposite direction. Now, if the skateboard is modified, for example, to rotate the truck axle 12 degrees when the deck is rotated 10 degrees, in order to produce a 6-foot turning radius, every degree of tilt will produce 1.2 degrees of steering change, but the mechanical advantage will be reduced by more than half, to 0.83:1—or a mechanical “disadvantage” of 1:1.2. The same depression in the road will produce a turning force requiring an offsetting counterforce 2.4 time greater than the previous example. Thus, the skateboard becomes less stable and more difficult to control, particularly for a lighter operator, inasmuch as the maximum counter force available to the operator is a function of the operator's weight, rather than strength.
The problem described above only gets worse when the skateboard is modified for use in rough terrain. Such modifications typically include increasing the length of the axles by several inches, to provide a wider wheel track for stability on rough terrain, and permit larger wheels, for a smoother ride. However, an axle with a single pivot axis in the center of the axle, like typical skateboard axles, can act as a lever when it encounters an obstacle. An obstacle “pushes” against a wheel at one end of the axle, with the pivot acting as a fulcrum. The lever arm is thus half the total length of the axle. Increasing the length of the axle increases the length of the lever arm, further increasing the mechanical disadvantage, so that an operator, particularly a smaller, lighter operator, might find it extremely difficult to control the board on rough terrain.
These problems are further exacerbated when such a skateboard is used as intended: i.e., for downhill coasting on the slope of a mountain or hill, as compared with operation over a level, paved surface. In a “mountain” environment, the rough terrain may present the skateboard with a constant succession of obstacles that must be negotiated, and that can necessitate steering corrections, the skateboard may accelerate to higher-than-normal speeds, causing any obstacle to strike with proportionately greater force, and the operator may have less time to prepare and respond to each obstacle.
Embodiments of the present invention provide features that significantly improve stability and controllability, and that mitigate or eliminating problems like those described above. The steering mechanism is more easily adaptable to for a small turning radius, and the loss of mechanical advantage is limited because of the short axle stubs. Furthermore, the length of the main axle can be changed without affecting the mechanical advantage: in the embodiments disclosed above, most of the axle does not pivot when the board turns but is held perpendicular to the frame rail. The front wheels are mounted on spindles that pivot on respective steering axes A₂near the ends of the axle. Thus, the lever arms formed by the axle stubs are only slightly longer than the width of the wheels, and do not change, regardless of the length of the axle. This gives the operator a significant mechanical advantage over forces applied to the wheels, even with a tighter turning radius.
In tests of prototypes built by the inventor, operators invariably found embodiments of the present invention to be more stable, easier to operate, and less fatiguing than mountain boards with skateboard-style trucks. This was the case, regardless of the operator's level of experience in operating a traditional skateboard.
The abstract of the present disclosure is provided as a brief outline of some of the principles of the invention according to one embodiment, and is not intended as a complete or definitive description of any embodiment thereof, nor should it be relied upon to define terms used in the specification or claims. The abstract does not limit the scope of the claims.
Elements of the various embodiments described above can be combined to provide further embodiments. Additionally, aspects of the embodiments can be modified to employ concepts and features that are known in the art, to provide yet further embodiments.
These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.

Claims

1. A wheeled vehicle, comprising:

a frame that includes a steering post extending from a front end of the frame and lying parallel to a longitudinal axis of the vehicle;

a deck coupled to the frame, positioned and configured to support a rider standing thereon;

a front axle coupled to the frame and configure to rotate about an axis defined by the steering post while remaining perpendicular to the longitudinal axis; and

first and second axle stubs coupled to respective ends of the axle and configured to be pivotable about respective first and second steering axes, relative to the axle.

2. The vehicle of claim 1, wherein the first and second axle stubs are parts of respective first and second spindles, each pivotably coupled to a respective end of the axle, the vehicle further comprising a tie rod coupled at a first end to the first spindle and at a second end to the second spindle, and configured to constrain the first and second spindles to pivot about the respective pivot axes substantially in unison.

3. The vehicle, of claim 2, comprising:

a steering linkage block fixed to the frame and configured to pivot therewith relative to the front axle; and

a drag link coupled at one end to the steering linkage block and at an opposite end to a steering arm of the first spindle, configured to cause the first spindle to pivot according to an angle of the frame relative to the axle.

4. The vehicle, of claim 2, comprising:

first and second front wheels rotatably coupled to respective ones of the first and second axle stubs; and

a rear wheel rotatably coupled to a rear end of the frame.

5. The vehicle of claim 2, wherein the first and second steering axes are tilted relative to the frame such that the first and second spindles each have a positive caster angle.

6. The vehicle, of claim 1, wherein the first and second spindles each have a positive caster angle of more than 30 degree.

7. The vehicle, of claim 1, wherein the frame includes a fork at the rear end of the frame, configured to receive a rear wheel rotatably coupled to the fork via an axle extending between arms of the fork.

8. The vehicle, of claim 7, comprising:

a rear wheel rotatably coupled to the fork via an axle extending between first and second arms of the fork; and

a braking assembly, including:

a brake rotor coupled to the rear wheel and configured to rotate therewith,

a brake caliper coupled to the first arm of the fork and positioned and configured to apply a braking force to the rotor,

a brake control handset, and

a brake cable coupled at a first end to the brake control handset and at a second to the brake caliper, and configured to transmit squeezing force from the brake control handset to the brake caliper.

9. The vehicle, of claim 1, comprising a steering return assembly configured to bias the first and second axle stubs toward a centered steering position.

10. The vehicle of claim 9 wherein the steering return assembly includes a torsion plate fixed to the frame and configured to pivot therewith relative to the front axle; and

Elastomeric bushings positioned on opposite sides of the torsion plate and arranged such that when the frame rotates, relative to the axle, away from a centered position, the torsion plate applies an angled compressive force to the bushings, which resist the compressive force, thereby applying a centering bias to the torsion plate.

11. The vehicle of claim 10, wherein:

the steering return assembly comprises:

a coupling link having a first end coupled to the axle; and

a linking rod having a first end coupled to a second end of the coupling link, extending through a transverse aperture in the torsion plate and upon which the elastomeric bushings are positioned.

12. A steering assembly for a wheeled vehicle, comprising:

an axle, including first and second spindle brackets affixed to the respective ends of the axle;

a steering tube fixed to the axle and crossing the axle at a center thereof, a central axis of the steering tube defining a horizontal axis of the steering assembly;

first and second spindles pivotably coupled to respective ones of the first and second spindle brackets, and configured to pivot about respective steering axes, the steering axes having a caster angle of greater than five degrees, relative to a vertical axis normal to the horizontal axis; and

a tie rod extending between the first and second spindles and configured to constrain them to pivot about the respective first and second steering axes in unison.

13. The steering assembly of claim 12, wherein the caster angle is at least 15 degrees.

14. The steering assembly of claim 12, wherein the caster angle is at least 30 degrees.

15. The steering assembly of claim 12, comprising a steering return assembly configured to bias the steering assembly toward a centered steering position.