Patent Publication Number: US-2017361203-A1

Title: Deck for ride-on devices

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. provisional application Ser. No. 62/090,757 filed Dec. 11, 2014, the disclosure of which is hereby incorporated in its entirety by reference herein. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to decks for ride-on devices, for example, skateboards. 
     BACKGROUND 
     There are numerous ride-on devices in the marketplace. Ride-on devices take many forms and may be used for exercise, entertainment or both. They may have a non-descript, mostly functional aesthetic form, like a skateboard or scooter, or they may be made to look like a vehicle, an animal or, a fictional character as with many preschool toys. 
     Conventional skateboards are generally supported by two-wheeled truck assemblies attached to the undersides of the boards. Such skateboards have long been popular, but are limited in the sense that the rider could realistically accelerate on a level or uphill surface only by removing one of his or her feet from the board and pushing off the ground. Typically, such skateboards were also limited in the degree of steering that was possible, as where the turning radius reached a certain angle, the wheels would touch the board. 
     There is a desire and need in the marketplace for ride-on products that can be propelled in a way that is more novel than simply pushing off, and that may provide sharper turns if desired. Caster boards were subsequently developed to address the limitations of skate boards. U.S. Pat. No. 7,195,259, the disclosure of which is hereby incorporated in its entirety by reference herein, provides certain examples of caster boards. Caster boards typically have comprised one or two boards, with at least one swivel caster wheel assembly in front and at least one in the rear of the caster board. The rider twists his or her body to the left and to the right to accelerate the caster board or to turn it within a relatively small turning radius. This is accomplished by having the wheels rotate around the wheel axis when the board is twisted in either direction, where the wheel axis is mounted at an acute angle with respect to the bottom, front and back of the caster board. 
     SUMMARY 
     In at least one embodiment, a ride-on device is provided. The ride-on device comprises a deck having a top surface and a bottom surface and at least two wheels attached to the bottom surface of the deck. The deck includes a bulk flexible material having a first stiffness and at least two resilient members extending in a fore-aft direction and having a second stiffness that is greater than the first stiffness. 
     In one embodiment, the bulk flexible material includes a thermoplastic polymer and the at least two resilient members are formed from a fiber composite. In another embodiment, the first stiffness is from 75 to 700 ksi and the second stiffness is at least 10 GPa. In another embodiment, the at least two resilient members are formed integrally with the bulk flexible material. In another embodiment, the at least two resilient members are attached to the bulk flexible material. In another embodiment, a resilient member extends along an outer edge on a port side of the deck and a resilient member extends along an outer edge on a starboard side of the deck. 
     In at least one embodiment, a deck for a ride-on device is provided. The deck comprises a base including a top surface for supporting a rider and a bottom surface for attaching at least two wheel assemblies. The deck includes a bulk flexible material having a first stiffness and at least two resilient members extending in a fore-aft direction and having a second stiffness that is greater than the first stiffness. 
     In one embodiment, the bulk flexible material includes a thermoplastic polymer and the at least two resilient members are formed from a fiber composite. In another embodiment, the first stiffness is from 75 to 700 ksi and the second stiffness is at least 10 GPa. In another embodiment, the at least two resilient members are formed integrally with the bulk flexible material. In another embodiment, the at least two resilient members are attached to the bulk flexible material. In another embodiment, a resilient member extends along an outer edge on a port side of the deck and a resilient member extends along an outer edge on a starboard side of the deck. The at least two resilient members may be formed of fiberglass. In one embodiment, the second stiffness is from 10 to 75 GPa. In another embodiment, the at least two resilient members have a rectangular cross-section. The deck may also include at least one swivel caster attached to the bottom surface, the at least one swivel caster having two wheels mounted equidistantly off-set from an axis of rotation of the caster&#39;s swivel. 
     In at least one embodiment, a ride-on device is provided comprising a deck having a top surface and a bottom surface. The deck may include a bulk flexible material having a first stiffness and at least two resilient members extending in a fore-aft direction. The at least two fiber composite resilient members having a second stiffness that is greater than the first stiffness and a density of at most 6 g/cm 3 . 
     In one embodiment, the density of the at least two resilient members is at most 4 g/cm 3 . The at least two resilient members may be attached to the bulk flexible material at least at the fore and aft of the deck. In another embodiment, the at least two resilient members are formed integrally with the bulk flexible material. The at least two resilient members may form at least a portion of an outer surface of the deck. In one embodiment, the first stiffness is from 0.5 to 5 GPa, the second stiffness is from 10 to 75 GPa, the bulk flexible material includes a thermoplastic polymer, and the at least two resilient members are formed of fiberglass. 
     In at least one embodiment, a ride-on device is provided. The ride-on device may include a deck having a top surface and a bottom surface and at least one swivel caster attached to the bottom surface. The at least one swivel caster may have two wheels mounted equidistantly off-set from an axis of rotation of the caster&#39;s swivel. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top plan view of a ride-on device having two caster assemblies, according to an embodiment; 
         FIG. 2  is a top perspective view of a ride-on device having three caster assemblies, according to an embodiment; 
         FIG. 3  is a side perspective view of the ride-on device of  FIG. 1 ; 
         FIG. 4  is a side perspective view of the ride-on device of  FIG. 2 ; 
         FIG. 5  is a bottom perspective view of the ride-on device of  FIG. 1 ; 
         FIG. 6  is a bottom perspective view of the ride-on device of  FIG. 2 ; 
         FIG. 7  is a schematic cross-section of a deck having two resilient members, according to an embodiment; 
         FIG. 8  is a schematic cross-section of a deck having four resilient members, according to an embodiment; 
         FIG. 9  is a schematic cross-section of a deck having two resilient members, according to another embodiment; 
         FIG. 10  is a schematic cross-section of a deck having two integral resilient members, according to an embodiment; and 
         FIG. 11  is a schematic cross-section of a deck having two integral resilient members, according to another embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present disclosure. 
     The present disclosure relates to sporting goods, including board sports. Boards made to ride on for sport, hereafter called “board(s)” or “deck(s),” may be used to ride on snow, water, and land. The structure of these boards or decks have evolved somewhat over time, however, it has always been important to those skilled in the art to have a board that has the right tensile strength for support and elastic properties for performance. Thermoplastics have been used in some low performance boards due to their relatively low cost. They may be very economical to mold and can be formed into a variety of shapes. However, thermoplastics generally lack the rebound flexibility that is inherent in “higher quality” boards, such as wood or resin-reinforced fiber. To those skilled in the art, thermoplastic boards are said to have no “pop,” and are therefore undesirable. Accordingly, boards or decks are generally made of a single composite or a substrate with high rigidity and a slight but highly elastic flexibility. It may be layered (e.g., wood laminates) and/or thicker in some places, but generally it is made of one construction that is mostly consistent throughout it&#39;s make up. 
     On most boards, pushing an edge down will cause a turn. For example, if you push down on one side of a skateboard or longboard you cause the trucks to position the wheels so that the direction of their overall bias is a curve. One skilled in the art of riding skateboards and longboards can actually gain momentum by alternating edges and shifting their weight from one side to the other. This may be referred to as carving, and can be used to gain or slow momentum without the need to place one&#39;s foot on the ground. However, even to one skilled in the art, carving cannot be counted on as a main means of propulsion with a common one piece land board. Skateboards and longboards were designed to be pushed or ridden downhill with a rider on top. Therefore, they are made of generally rigid material so they can support a rider. The board material needs to be strong enough to support the weight of the rider across the long wheel base between the front and rear trucks (or casters). To make the board strong enough to support the rider over this expanse, fore to aft, the stiffness must be high enough that the board is virtually not flexible from port to starboard. 
     This issue has been addressed in the art through the use of a torsion bar and separating the board or deck into two pieces. Examples of ride-on devices including torsion bars and casters include U.S. Pat. No. 7,195,259 (described above) and U.S. Pat. No. 8,297,630, the disclosure of which is hereby incorporated in its entirety by reference herein. However, splitting the board or deck into two pieces may create an uneven riding platform, which those skilled in the art may find restrictive. Another approach has been a caster board that uses a one-piece thermoplastic deck. However, since only one substrate is used in its construction, the material must become very narrow (port to starboard) in its middle (fore to aft) to allow for twisting. This makes the board essentially equivalent with those having two separate decks, when one considers foot placement or when doing board slides on a rail, for example. Also, a twistable-midsection or torsion bar creates a weak point in the construction of these boards. 
     It would be beneficial if the standard board shape(s), such as the “popsicle stick” shape or other popular shapes (e.g., oval, ellipse, rounded rectangle, etc.), could have the rigidity to support a rider, fore to aft, and the flexibility to twist, port to starboard. Standard board shapes are generally consistently wide, such that they do not narrow near the middle (fore to aft) like boards with torsion bars or casters. Flexibility to twist (port to starboard) may increase maneuverability and the propulsion when carving. It also may be beneficial when carving a hill for purposes of slowing or controlling speed. 
     In addition, if the board were flexible, port to starboard, the ride may be able to control a single truck or caster independently (e.g., front or back) and may even be able catch opposite edges, which would create much more turning control. Moreover, when carving, the transition between one edge and another can be twisted into, which may give a smoother transition between one edge and the other. To facilitate this, the deck must be rigid enough to support a rider standing on top, yet be flexible enough (port to starboard) that it can catch opposite edges fore and aft. A smoother transition may result in less loss of inertial momentum and the ability of one set of wheels to bias itself against the other. This may allow the rider to work one set of wheels against the other, much like is done with inline or even quad skates. 
     With reference to  FIGS. 1 to 6 , a ride-on device  10  is provided including a board or deck  12  having sufficient stiffness and/or rigidity in the fore-aft direction and increased flexibility in the port-starboard direction. While the Figures show the ride-on device deck as a skateboard deck, it may be used as a board or deck for any ride-on device, such as a scooter, surfboard, snowboard, or others. As used herein, the term “skateboard” may include any type of skateboard, such as traditional skateboards, longboards, caster boards, or others. 
     The deck  12  may include a base  14  having a top side  16  and a bottom side  18 . The top side  16  may support the feet of a rider and the bottom side  18  may attach to a wheel assembly. As described above, skateboards may be supported in a plurality of ways, including using caster assemblies, truck assemblies, or a combination thereof. In one embodiment, the deck  12  may be supported by one or more caster assemblies  20 . Caster assemblies are known to those of the art, and will not be described in detail. In general, caster assemblies include one or more wheels supported by a wheel bracket. The wheel(s) may attach so as to rotate freely along its entire circumference. The wheel(s) may further rotate freely about a wheel axis, or they may be fixed such that they are aligned in a single direction (e.g. in the fore-aft direction). The wheel bracket may be rotatably connected to a caster shaft having a caster shaft axis, which may be angularly offset from the wheel axis. Additional description of caster assemblies is included in U.S. Pat. No. 7,195,259 and U.S. Pat. No. 8,297,630 (described above). As shown, for example, in  FIGS. 3 and 5 , the deck may include at least one swivel caster having two wheels mounted equidistantly off-set from an axis of rotation of the caster&#39;s swivel. 
     The caster assemblies  20  may include a single wheel (e.g.,  FIGS. 1, 3, and 5 ) or a double wheel (e.g.,  FIGS. 2, 4, and 6 ). In addition, the caster assemblies  20  may be rotatable or may be fixed. The deck  12  may have one or more caster assemblies  20  attached thereto, which may have any combination of one or two-wheeled caster assemblies. The caster assemblies  20  may be described as either fore (forward) or aft (rear) caster assemblies, depending on whether they are more near the fore (front)  22  or the aft (back)  24  of the deck  12 . There may be one or more fore caster assemblies  20  and one or more aft caster assemblies  20 , depending on the device design. In one embodiment, the deck  12  may have two caster assemblies  20 , one fore and one aft. These caster assemblies  20  may have two wheels (e.g., as shown in  FIGS. 1, 3, and 5 ) and may be fixed or rotatable (or a mixture thereof). In another embodiment, the deck  12  may have three caster assemblies  20 . In this embodiment, there may be two caster assemblies  20  on the aft  24  of the deck  12  and one caster assembly on the fore  22  of the deck  12 . However, this arrangement may be reversed (one assembly in the aft, two in the fore). These caster assemblies  20  may be single wheel assemblies and may be rotatable (e.g., as shown in  FIGS. 2, 4, and 6 ). 
     If the deck  12  has a single caster assembly  20  at one end, the caster assembly may be located along a center line or longitudinal axis  38  of the deck  12 . If the deck  12  has multiple caster assemblies  20  (e.g., two) at one end, the assemblies may be offset from the center line  38  (e.g., one on each side). Embodiments having two caster assemblies  20 , one fore assembly and one aft assembly, may be referred to as double edge decks, while embodiments having three caster assemblies, one fore and two aft (or vice versa), may be referred to as triple edge decks. While the ride-on devices  10  shown in the Figures include caster assemblies  20 , truck assemblies may also be used to attach wheels to the deck  12 . Truck assemblies are known in the art and will not be described. In addition, a combination of caster assemblies and truck assemblies may also be used, such as a truck assembly in the aft and a caster assembly in the fore, or vice versa. As described above, the caster assembly may have various configurations, such as single or double-wheel, fixed or rotatable, or others. 
     In at least one embodiment, the deck  12  has sufficient stiffness and/or rigidity in the fore-aft direction to support the weight of a ride, while also having increased flexibility in the port-starboard direction (e.g., to increase maneuverability and the propulsion). As described above, skateboard design generally must pick between a traditional deck shape (“popsicle stick,” oval, rounded rectangle, etc.), having high stiffness and very low flexibility, and a split-deck or narrow-neck design, having greater flexibility but lower stability and balance and a potentially weakened structure. 
     With reference to  FIGS. 1 to 6 , a deck  12  is provided that allows for a standard deck design (e.g., little or no narrowing at the middle), while increasing the flexibility in the port-starboard direction. In one embodiment, these improved properties are provided via a combination of a flexible bulk material  30  and a plurality of stiffening or resilient members  32 . The bulk material  30  may form or comprise a majority of the base  14  of the deck  12  (e.g., over 50, 75, or 90 wt %), providing it with flexibility in the port-starboard direction. The deck  12  may be formed of the bulk material  30  in certain areas or regions in order to provide the port-starboard flexibility. In one embodiment, a region  34  including the center line or longitudinal axis  38  of the deck  12  may be formed of the bulk material  30 . The region  34  may extend in the port and starboard directions from the center line  38  to form a strip along the length of the deck  12  that is formed from the bulk material  30 . By forming a central portion (port-starboard) of the deck  12  from the flexible bulk material  30 , the deck  12  may have increased flexibility in the port-starboard direction when, for example, a rider shifts their weight between their heel and forefoot. In another embodiment, substantially all of the base  14  is formed of the bulk material  30  (e.g., substantially the whole deck except the resilient members  32 ). 
     While the bulk material  30  provides flexibility, it may not have sufficient stiffness or resiliency to support the weight of a rider in the fore-aft direction. Accordingly, in at least one embodiment, a plurality of stiffening or resilient members  32  are provided to increase the fore-aft stiffness of the deck  12 . The stiffening members  32  may extend in the fore-aft direction and may be formed of a material having a higher stiffness than the bulk material  30 . In one embodiment, two stiffening members  32  are provided, one on each side of the center line  38  of the deck  12 . The stiffening members  32  may extend parallel to the center line  38  and may be equally spaced from the center line  38 . In one embodiment, the stiffening members  32  may extend along an outer edge  36  of each side (port/starboard) of the deck  12 . Locating the stiffening members  32  farther from the center line  38  may increase the flexibility of the deck  12  in the port-starboard direction. 
     The deck  12  may have an upward or concave portion at the fore and/or aft end, as is known to those of ordinary skill in the art. In one embodiment, the resilient members  32  may extend substantially the entire distance from the fore to the aft end of the deck  12  between the concave portions (if present). The resilient members  32  may extend into the concave portions in some embodiments, however, that is not required. The resilient members  32  may have any suitable transverse cross-sectional shape, such as rectangular, square, circular, or others. The resilient members  32  may also be hollow to reduce weight. While  FIGS. 1 to 6  show a deck  12  having two resilient members  32 , there may be more (e.g., 2, 4, 6, etc). In one embodiment, there are an even number of resilient members  32 , with an equal number of resilient members  32  on each side of the center line  38 . The resilient members  32  may be in pairs that are equally spaced from the center line  38 . As shown in, for example,  FIGS. 5 and 6 , the resilient members  32  may be exposed (e.g., able to be seen without removing or altering any portion of the deck  12 . Stated another way, the resilient members  32  may form at least a portion of an outer surface of the deck  12 . 
     In at least one embodiment, the resilient members  32  may be formed from a different material than the flexible bulk material  30 . The bulk material  30  may be a polymer, such as a thermoplastic or a thermoset polymer. Non-limiting examples of thermoplastics that may be suitable for the bulk material  30  include polyolefins (e.g., polyethylene and polypropylene), poly(methyl methacrylate) (PMMA), polyesters, polyurethanes, polycarbonates, acrylonitrile butadiene styrene (ABS), polyamides (e.g., nylon), polystyrene (PS), polyvinyl chloride (PVC), fluoropolymers (e.g., polytetrafluoroethylene (PTFE)), or others. The resilient members  32  may be formed of a stiff, elastic, and/or resilient material. In one embodiment, the resilient members  32  may be formed from a fiber composite (e.g., fibers in a matrix, usually a resin). Any suitable fiber composite having high stiffness and resiliency may be used. Non-limiting examples of types of fiber composites may include fiberglass, carbon fiber, aramid fiber (e.g., Kevlar), boron fiber, ceramic fiber, or other fiber composites. The fibers may be short fibers, long fibers, or continuous fibers. In addition to, or instead of, fiber composites, other stiff materials may be used in the resilient members  32 , such as metals (e.g., steel, aluminum, titanium, etc.) or high-stiffness polymers. 
     The flexible bulk material  30  and the resilient members  32  may be formed of relatively light materials in order to keep the weight of the deck  12  low. In one embodiment, the bulk material  30  may be formed of a material having a specific gravity or density of at most 5 g/cm 3 . For example, the bulk material  30  may be formed of a material having a density of at most 2, 3, or 4 g/cm 3 . In one embodiment, the resilient members  32  may be formed of a material having a specific gravity or density of at most 6 g/cm 3 . For example, the resilient members  32  may be formed of a material having a density of at most 3, 4, or 5 g/cm 3 . In another embodiment, the bulk material  30  and the resilient members  32  may both be formed of materials having a density of at most 3, 4, or 5 g/cm 3 . 
     In embodiments where the bulk material  30  is different than the material used in the resilient members  32 , the resilient members  32  may be attached, connected, or incorporated into the deck  12  in numerous ways. In one embodiment, the resilient members  32  may be incorporated into the deck  12  during the molding process of the deck  12 , such that it is integrally formed with the deck  12  and the bulk material  30 . The deck  12  may be formed using any suitable process, such as injection molding, compression molding, or others. Accordingly, if the deck  12  is formed my injection molding, for example, then the resilient members  32  may also be formed during the injection molding process. Injection molding techniques for forming multiple-material components are known in the art and will not be discussed in detail. Examples of multiple-material injection techniques may include insert or over-molding, co-injection molding, sandwich molding, bi-injection molding, or interval molding. 
     In other embodiments, the resilient members  32  may be formed separately from the rest of the deck  12  and attached in an additional process. For example, the resilient members  32  may be formed using any suitable process, such as injection molding, compression molding, extrusion, casting, machining, etc., and then attached the bottom side  18  of the deck  12 . The attachment may be performed using any suitable method. Non-limiting examples of attachment method may include fasteners (e.g., nails, screws, bolts, rivets), adhesives (e.g., glue), welding (e.g., using heat or ultrasound), or others. The resilient members  32  may be attached or connected to the deck  12  along their entire length or in certain discrete regions. For example, the resilient members  32  may be connected to the deck  12  (e.g., the bulk flexible material  30 ) at least at the fore and aft ends of the deck. The resilient members  32  may also be connected to the deck  12  at other regions, such as the middle of the deck  12 . 
     In another embodiment, the resilient members  32  may be formed of the same material as the bulk material  30 . In this embodiment, rigidity in the fore-aft direction may be provided by the shape of the resilient members  32 , rather than a more stiff material. The shape of the resilient members  32  may be similar to those described above, such as rectangular, square, etc., or it may have a cross-section designed to maximize the moment of inertia, such an I-beam or a T-beam. If the bulk material  30  and the resilient members  32  are formed from the same material, then a material having an intermediate stiffness may be chosen such that there is sufficient stiffness in the fore-aft direction and flexibility in the port-starboard direction. 
     With reference to  FIGS. 7 to 11 , several exemplary embodiments of deck  12  with resilient members  32  are shown. These Figures may be cross-sections along line X-X in  FIG. 6  (or a similar line in  FIG. 5 ). In the embodiment shown in  FIG. 7 , there are two resilient members  32 , one on each side of the center line  38  (shown as a plane extending out of the page in  FIGS. 7-11 ) and each located at an outer edge  36  of each side (port/starboard) of the deck  12 . In the embodiment shown in  FIG. 8 , there are four resilient members  32 , two on each side of the center line  38 . One of the resilient members  32  on each side is located on an outer edge  36  and the other is spaced inward towards the center line  38 . The resilient members  32  may be evenly/symmetrically spaced from the center line  38 . Since there are more resilient members  32  in this embodiment, each member may be smaller (e.g., shorter, thinner, or both). In the embodiment shown in  FIG. 9 , there are two resilient members  32 , one on each side of the center line  38  and each spaced inward from the outer edge  36  of each side (port/starboard) of the deck  12 . While placing the resilient members  32  on the outermost edge may provide the highest port-starboard flexibility, the resilient members  32  may be spaced inward from the edge  36  if less flexibility is desired or for other design considerations. The embodiments shown in  FIGS. 7 to 9  and described above show a deck  12  with resilient members  32  attached thereto (e.g., formed separately). However, the same resilient member configurations may also be generated using a multiple-material molding process (such as those described above). 
     In the embodiment shown in  FIG. 10 , there are two resilient members  32 , one on each side of the center line  38  and each located at an outer edge  36  of each side (port/starboard) of the deck  12 , similar to  FIG. 7 . However, the embodiment shown in  FIG. 10  shows resilient members  32  that are integrally formed with the bulk material  30  of the deck  12 . As described above, other configurations of the resilient members  32  may be generated using a multiple-material molding process (e.g., more than two resilient members, spaced from the edge, etc.). Similarly, in the embodiment shown in  FIG. 11 , there are also two resilient members  32 , one on each side of the center line  38  and each located at an outer edge  36  of each side (port/starboard) of the deck  12 . However, the embodiment shown in  FIG. 11  shows resilient members  32  that are formed from the same material as the bulk material  30 . The resilient members  32  are therefore integrally formed with the deck  12 . Other configurations of the resilient members  32  may also be formed in the same manner. As described above, the shape of the resilient members may have a high moment of inertia (e.g., I-beam or T-beam) if they are formed from the bulk material  30 . The embodiments shown in  FIGS. 7 to 11  and their corresponding descriptions are merely examples. The attachment methods, shapes, and configurations described in this disclosure can be mixed and matched or combined in any combination. 
     As described above, in at least one embodiment, the resilient members  32  may be formed of a material that is different from and less flexible than the flexible bulk material  30 . Modulus of elasticity, or Young&#39;s Modulus, may be one measure of the relative stiffness or flexibility of a material. The flexible bulk material  30  may have a Young&#39;s Modulus (E) of 75 to 700 ksi (about 0.5 to 5 GPa), or any sub-range therein. For example, the flexible bulk material may have a Young&#39;s Modulus of 85 to 500 ksi, 90 to 400 ksi, 100 to 400 ksi, 200 to 400 ksi, 200 to 500 ksi, 100 to 300 ksi, or others. The resilient members  32  may be formed of a material having a higher Young&#39;s Modulus, such as over 5 GPa (about 725 ksi). For example, the resilient members  32  may be formed of a material having a Young&#39;s Modulus of at least 10, 15, 25, 50, 75, 100, 150, or 200 GPa. Stated another way, the resilient members  32  may be formed of a material having a Young&#39;s Modulus of 5 to 300 GPa, or any sub-range therein, such as 10 to 250 GPa, 10 to 200 GPa, 10 to 175 GPa, 10 to 150 GPa, 10 to 100 GPa, 10 to 75 GPa, 10 to 50 GPa, 50 to 200 GPa, 50 to 150 GPa, 75 to 200 GPa, 75 to 175 GPa, 100 to 200 GPa, 125 to 175 GPa, or others. 
     Separate from the longitudinal resilient members  32 , additional ribs  40  may be included on the bottom side  18  of the deck  12 . The ribs  40 , which are shown in  FIGS. 5 and 6  may add additional stiffness or rigidity in local areas, such as near or around the caster assemblies and/or truck assemblies, at the nose (fore) and/or tail (aft) end of the deck (e.g., upwardly curved portions), or near the middle (fore to aft) of the board. Stiffening ribs  40  near or around the caster assemblies (or truck assemblies) may increase the stiffness and facilitate a more solid connection between the assemblies and the deck  12 . Similarly, stiffening ribs  40  as the nose or tail may increase the stiffness of those portions that require more stiffness during use (e.g., stepping on nose or tail to “pop” the board up into the hand). Ribs  40  located near the fore-aft middle of the deck  12  may assist in creating a pivot or flex point around which the port-starboard rotation or flexing takes place. For example, if a rider presses down on the forefoot with one foot and the hell with the other foot, the ribs  40  may localize the flexing of the board to each half of the deck. 
     As described above, the disclosed deck  12  having a flexible bulk material  30  and stiffening members  32  may provide a ride-on device with increased port-starboard flexibility, while maintaining fore-aft stiffness and support for the rider. The disclosed deck  12  may allow a rider to twist his or her body to the left and to the right to accelerate the ride-on device or to turn it within a relatively small turning radius. Therefore, the functionality of a caster board may be incorporated into a ride-on device with the appearance and stability of a skateboard or longboard. In addition, the deck  12  may allow a rider to catch two edges at the same time. 
     Decks having dual wheel casters and single wheel casters, or combinations thereof, are disclosed. In addition, caster assemblies may be combined with truck assemblies. The caster assemblies may be rotatable or fixed, and a deck may include all rotatable, all fixed, or a mixture of rotatable and fixed caster assemblies. Decks having two caster assemblies (one fore and one aft) may include dual wheels, which may make the ride-on device lean less than single-wheel casters. This may make the device ride similar to a standard flat skateboard, but with improved turning radius and ability to propel without pushing-off that comes with casters. Decks with three caster assemblies (two aft and one fore, or vice versa) may include single-wheel casters. This may provide greater lean compared to dual-wheel casters and ride more similar to a caster board, but with improved stability and a more standard look. 
     While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention.