Patent Publication Number: US-11383127-B1

Title: Mechanism to provide intuitive motion for bicycle trainers

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority from provisional application 62/804,094 filed on Feb. 11, 2019 and from provisional application 62/832,909 filed on Apr. 12, 2019. 
    
    
     BACKGROUND 
     Stationary trainers or stationary bicycles are often used when outdoor cycling is impeded, such as with poor weather or traffic condition, or when a controlled environment for certain focused and uninterrupted exercises on a bicycle are desired. 
     Stationary trainers often operate by fixing an ordinary bicycle to a device, called a trainer. A trainer can include a resistance mechanism and a flywheel, the combination of which will hereafter be referred to as a resistance device. 
     In one variety of trainers, referred to as wheel-on trainers, a bicycle is held by the trainer at the rear wheel axle. The rear wheel tire is in contact with and drives the resistance device. 
     In another variety of trainer, referred to as direct-drive trainers, a bicycle&#39;s rear wheel is removed and the bicycle is mounted to the trainer at the rear wheel mounts. The resistance device of a direct-drive trainer is driven directly by the bicycle&#39;s chain rather than the tire. 
     Stationary bicycles are stationary cycling exercise machines that are intended for indoor use. A stationary bicycle can include a resistance device similar to a stationary trainer. A stationary bicycle can include a seat, handlebars, pedals and other components. A stationary bicycle is a complete exercise machine, whereas a stationary trainer is intended to have a bicycle mounted to it. 
     Alternatively, a stationary trainer or stationary bicycle can be provided with an adaptive resistance device. Adaptive stationary trainers are often called smart trainers. Adaptive stationary bicycles may be called smart bikes. Such smart trainers and smart bikes can adjust the environment of the ride, such as the resistance level of a resistance device in order to simulate hills, drafting, and other aspects of outdoor riding. 
     For example, a smart trainer or bike can be connected to applications that can provide a visual riding simulation experience. Such simulation applications can include a video of desired scenic route, which can be synchronized with a dynamically variable resistance to create a virtual reality type of experience. In one example, a cyclist using such a smart trainer or bike may want to stand up and sprint, climb, or perform other cycling ergonomics that are more dynamic than steady state riding on a stationary trainer. Typical stationary trainers mount the bicycle into a static position where the stationary trainer sits on the floor and does not allow any rocking motion, like those types of motions in outdoor cycling. Similarly, smart bikes are typically heavy rigid machines that do now allow dynamic motion. 
     In addition to the dynamic motions that an outdoor cyclist uses in sprinting or hill climbing, an outdoor cyclist on an outdoor bicycle makes lateral motions during the pedal stroke that induce a slight rocking of the bicycle. These lateral motions can reduce seat discomfort. The lateral motions can also provide leverage to aid with power output to the pedals. Rigid stationary trainers, such as wheel-on and direct-drive trainers, and stationary bicycles restrict this lateral motion as such motion may cause the stationary trainer to lose control of the bicycle. 
     On a bicycle fixed to a stationary trainer, or on a rigid stationary bicycle, power to the pedals is predominately from a cyclist&#39;s legs. A cyclist cannot induce or restrict lateral motion of the bicycle beyond that provided by the stationary trainer. In outdoor cycling, a cyclist can use core and upper body strength, to an extent, to balance and provide leverage for the pedal stroke. When using a stationary trainer these muscles are not required and as such, a cyclist can get an incomplete workout compared to outdoor riding. This reduction of muscle use can reduce the quality of a workout especially when compared to outdoor cycling. Many cyclists use stationary trainers or stationary bikes to prepare for outdoor riding. A rigid stationary trainer or stationary bike thus provides incomplete preparation by not including all muscle groups used in outdoor riding. 
     In outdoor cycling, a cyclist can keep a steady center of mass in the lateral direction using balance and counter-balance actions. In a standing position, such as during a sprint or hard climbing effort, a cyclist&#39;s mass is primarily supported at the pedals. When in a standing position, a cyclist can move the bicycle somewhat freely while keeping his or her mass relatively stable. The pedals rotate around the assembly of axle and bearings known as the bottom bracket of a bicycle. A cyclist can sway a bicycle laterally with a center of rotation roughly near the bottom bracket. 
     The ground plane can be defined as the surface in contact with the bottom of the tire. The top of the bicycle can be considered the portion of the bicycle near the handlebars. The tire track is the path that the tires make along the ground plane as the bicycle moves along the ground plane. In one example, when the top of the bicycle sways to the right, the bottom of the tires may move in the opposite direction, which in this case is to the left. In this way, the tire track will swerve from side to side as the cyclist sways the bicycle. In this example, the top of the bicycle and the bottom of the tires are moving in opposite directions laterally. The center of rotation is above the ground plane. The tire track can oscillate laterally around a generally straight line of forward motion. If the bottom bracket is the approximate center of the lateral rotation described in this example, the bicycle&#39;s bottom bracket will not be moving laterally to an extent noticeable by the cyclist. This allows the cyclist to keep their mass laterally stable with the bottom bracket while rocking the bicycle to increase power. 
     One method of providing lateral movement to a stationary trainer is to provide a pivot directly under a rocker plate that is supporting a bicycle and a stationary trainer. Energy rebounding components, such as foam blocks, partially inflated balls, or inner tubes are used below each side of rocker plate to provide centering forces to keep the bicycle in an upright neutral position to allow a cyclist to move the bicycle laterally. 
     However, this arrangement does not provide a natural-feel rocking motion. In such an arrangement, the bottom bracket can be approximately 300 mm above the lateral rotation axis. Because the cyclist must move their center of mass laterally along with a mechanical, pre-set rocking motion, it can be difficult to synchronize the motion of rocking the bicycle during standing efforts. Opposing forces applied to the pedals and handlebars may not have the same effect on the rocking motion because the pivot point has been moved from the bottom bracket to below the bottom surface of the tires. The resulting motion can be awkward and does not integrate into the motion of applying force to the pedals. The awkwardness is especially noticeable when a cyclist is standing out of the saddle. 
     Additionally, the cyclical power of the pedaling force typically causes the bicycle to surge or pulse fore and aft relative to the cyclist during riding. Because the pedals move in a circular motion, the force applied to the pedals can have a horizontal component as well as a vertical component. The horizontal component will tend to push the bicycle forward or rearward relative to the cyclist. Additionally, the circular motion of the pedals results in a fluctuating power output from the cyclist. The result of the horizontal forces and fluctuating power output is that in outdoor riding a bicycle can tend to move fore and aft relative to the cyclist. To mimic this relative motion on a stationary trainer or stationary bicycle fixed in place, a cyclist must surge their own mass fore and aft. This does not result in a realistic riding feel and can be less efficient for the cyclist. Alternatively, the cyclist can remain fixed in the fore-aft direction relative to the bicycle. This can result in unnatural pedaling dynamics and increased discomfort on the seat. 
     Embodiments of a dynamic trainer that can simulate a rocking motion with or without fore-aft motion similar to an on-road experience are provided herein. Embodiments disclosed herein are capable of accommodating and supplementing wheel-on trainers, direct-drive trainers, and stationary bicycles but can also be integrated with other trainers not discussed herein. Additionally, embodiments disclosed herein can be integrated into a structure of a wheel-on or direct-drive trainer, if desired. Other features and advantages of the invention will be apparent from the following description of the embodiments thereof, and from the claims. 
     SUMMARY 
     As used herein, the term “cyclist” or “rider” can indicate a user on a stationary trainer, a wheel-on trainer, direct-drive trainer, a stationary bicycle, etc. 
     In embodiments provided herein, a dynamic device, such as a dynamic trainer, and method of using a dynamic device to provide natural lateral and/or for-aft movement is described. By providing such a dynamic device, embodiments described herein can allow a cyclist to move dynamically in ways similar to riding on a moving bicycle, such as outdoors or in a velodrome, rather than on a stationary trainer. Embodiments described herein can provide a mechanism which can support a stationary trainer and can have a center of rotation near a bicycle&#39;s bottom bracket to provide a more accurate feel and function. Other embodiments can be produced with a center of rotation at any point above the surface which would contact the bottom of the bicycle tires. 
     In embodiments provided herein, a dynamic device can be provided along with a stationary device to allow a cyclist to be in a standing position, such as during a sprint or climbing effort, and the dynamic device can allow a cyclist to be able to rock a bicycle without requiring lateral motion of the cyclist&#39;s center of mass to pivot from the bottom of the bicycle. Pedal forces can also cause the bicycle to move fore and aft slightly during riding. Opposing up and down forces on the handlebars and pedals can also have a familiar effect on bicycle dynamics when provided with an example dynamic device compared to a moving bicycle. Example dynamic devices can also allow for a rocking action to be intuitive to a cyclist and easy to synchronize with pedaling motions. 
     In one embodiment, a dynamic device can be provided with a movable closed chain linkage, such as a four-bar mechanism or linkage, with a floating link that hangs from two or more side links. 
     An example embodiment is a four-bar linkage mechanism to provide a rocking and fore-aft motion for a stationary trainer. An example four-bar linkage mechanism can be defined by: a grounding base including two grounding pivots; a floating link with two pivots; a supporting member connected to the floating link which can support a bicycle and trainer; and two side links each connected to the grounding pivots in the base at one end and to the pivots on the floating link at the other end. In a nominal rest position the grounding pivots can be above the floating link pivots. 
     The base can include stanchions which provide support for grounding pivots elevated above the bottom surface of the base. The stanchions can be features integrated into the base or separate components attached to the base. 
     Additionally, two or more four-bar mechanisms can be used to provide stability perpendicular to a plane of a mechanism, wherein floating links of the two or more four-bar mechanisms can be connected and can move together. Multiple four-bar mechanisms can have common side links to improve synchronicity and stability between the four-bar mechanisms. 
     The structural components of the dynamic trainer including the support member, base, stanchions, floating links, and side links can be made of any stiff material that can provide support for a stationary trainer, as well as a cyclist thereon. For example, the frame can be made of wood, metal, plastic, or a composite such as carbon fiber. It has been found that a frame of wood provides durability and dampens noise from the trainer more than metal, for example. Various components of the dynamic trainer can be made of different materials, depending on the design considerations of the particular components. 
     In one, a supporting member can be allowed to swing laterally on a four-bar mechanism&#39;s floating link(s) of the four-bar mechanism(s), and a stationary trainer can be mounted onto the support member, which will be discussed further below. 
     The floating link can be attached to a plate or other member that supports the bicycle and stationary trainer. The floating link can be made in the shape of protrusions from the support member with squared, rounded, or other shaped areas to connect the dynamic device to the support member and thus the bicycle and stationary trainer. Each floating link can contain two features two provide a pivoting interface to the side link pivot interfaces. 
     Components of the four-bar mechanism are comprised of pivot features which can be used to connect the components pivotally. These features can be holes, studs, shafts, rods, or other attachment features that provide a means of pivotally connecting components. As used herein, the term “pivot” can indicate any such feature that can provide a means of pivotally connecting two or more components. 
     The side links can be provided with grounding pivots above the floating link pivot interfaces such that gravity can pull the floating link to a neutral center position relative to the dynamic device. The geometry of the four-bar mechanism can be designed such that the center line of the side links projects to an intersection near the bottom bracket. In one embodiment, a distance between grounding pivots can be less than the distance between floating link pivots. This geometry can provide a virtual center of rotation above the grounding pivots. By providing the side links in this location, a virtual center of motion of the dynamic device can be provided. Additionally, a variety of link lengths can be designed to have a different feel and range of motion. 
     Additionally, in one embodiment, a four-bar linkage can be symmetrical around a vertical plane perpendicular to a plane of action. Specifically, side links can be of equal length and grounding pivots can be at an equal vertical elevation to the side links. 
     By providing one or more of the geometries described herein, the dynamic device can be naturally stable at a center position without requiring opposing spring forces to hold it in the lateral neutral center position. 
     In embodiments herein, two or more four-bar mechanisms can be used to provide dynamic movement, as well as, stability in a fore-aft direction in addition to a lateral direction. The floating links of these four-bar mechanisms can be connected such that the floating links move together as a single unit. In another embodiment, grounding links can be provided and can be fixed together, either via structure in the device, or by resting on a common surface, where the grounding links would be in addition to the floating links, which will further discussed below with the Figures. 
     Additionally, in embodiments herein, side links on either side of the four-bar mechanisms can be connected as extended side links. In this way, the extended side links can be common to two or more four-bar mechanisms. 
     Additionally, a dynamic trainer according to the embodiments described herein can be integrated into a stationary exercise bicycle. In such embodiments, the support member can be integrated into the structure of the stationary bicycle. 
     In another group of embodiments which will be explained further below, linear bearings can provide a means of fore-aft motion on a plurality of linear shafts or rods at the side link assembly pivots. The linear bearings can travel fore and aft on the linear rods as well as rotate on the linear rods. 
     In the embodiments with linear bearings described herein, mechanical energy absorbing elements can be included in the dynamic trainer to provide a means of returning the dynamic trainer away from the limits of fore-aft travel. These energy absorbing elements can be metal springs, elastic cords, or other components that are capable of absorbing and returning kinetic energy. The energy absorbing elements can be between any component of the dynamic trainer that is capable of moving in the fore-aft direction and a component that is stationary in the fore-aft direction. 
     In one embodiment, linear bearings can be included in the lower side link pivots of the side link assemblies. One or more linear rods can be connected at the floating link pivots. The upper side link pivots in this embodiment can be pivotally connected to the grounding pivots of the base or stanchions. The linear rods can move in the fore-aft direction through the linear bearings in the side link assemblies. In this way, the linear rods, floating links, and support member can move together in the fore-aft direction. 
     In another embodiment, linear bearings can be included in the upper side link pivots of the side link assemblies. One or more linear rods can be connected at the grounding pivots in the base or stanchions. The lower side link pivots in this embodiment can be pivotally connected to the floating link pivots. The linear bearings in the side link assemblies can move along the linear rods in the fore-aft direction. In this way, the side link assemblies, floating links, and support member can move together in the fore-aft direction. 
     In another embodiment, linear rods can be fixed to side links at the upper side link pivots so that the side link assembly includes one or more linear rods. The lower side link pivots in this embodiment can be pivotally connected to the floating link pivots. Linear bearings can be included in the grounding pivots in the base or stanchion. The linear rods within the side link assemblies can move in the fore-aft direction through the linear bearings. In this way, the side links, linear rods, floating links, and support member can move together in the fore-aft direction. 
     In another embodiment, linear rods can be fixed to side links at the lower side link pivots so that the side link assembly includes one or more linear rods. The upper side link pivots in this embodiment can be pivotally connected to the grounding pivots. Linear bearings can be included in the floating link pivots. The linear bearings can move in the fore-aft direction along the linear rods of the side link assemblies. In this way, the floating links, and support member can move together in the fore-aft direction. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated and constitute a part of this specification, illustrate example embodiments. In the drawings, 
         FIG. 1  is an illustration of an embodiment of a bicycle and a dynamic trainer; 
         FIG. 2  is an illustration of an embodiment of a stationary bicycle integrated with a dynamic trainer; 
         FIG. 3  is an illustration of an example dynamic trainer; 
         FIG. 4  is an illustration of an example dynamic trainer; 
         FIG. 5  is a mechanism diagram of a rear view of an example dynamic trainer with the dynamic trainer at the center position; 
         FIG. 6  is a mechanism diagram of a rear view of an example dynamic trainer with mechanism rotated from the center position; 
         FIG. 7  is a side view of an example dynamic trainer; 
         FIG. 8  is a detailed view of an example side link assembly of a dynamic trainer; 
         FIG. 9  is a detailed view of an example spring assembly of a dynamic trainer; 
         FIG. 10  is a top view of an example dynamic trainer; 
         FIG. 11  is a detailed sectional view of an example dynamic trainer; 
         FIG. 12  is an illustration of an example dynamic trainer; 
         FIG. 13  is a detailed view of an example side link assembly of a dynamic trainer; 
         FIG. 14  is an illustration of an example dynamic trainer; 
         FIG. 15  is an illustration of an example dynamic trainer; 
         FIG. 16  is a detailed view of an example side link assembly of a dynamic trainer; and 
         FIG. 17  is an illustration of an example dynamic trainer. 
     
    
    
     DETAILED DESCRIPTION 
     In one example, as illustrated in  FIG. 1 , an embodiment of dynamic trainer  100  is shown with a bicycle  102  and a stationary trainer  104  ready for use in conjunction with dynamic trainer  100 . A typical bicycle  102  will include pedals  108  which rotate around the axle and bearings known as the bottom bracket  106 . Dynamic trainer  100  can be directed to focus on bottom bracket  106  as a neutral position instant center  138 . It is noted that positions other than bottom bracket  106  as the neutral position instant center  138  may be used. For example, the neutral position instant center  138  may be adjusted as needed for different stationary trainers  104  or bicycles  102 . 
     A grounding base  112  can be configured and constructed to provide a stable interface to a substantially flat surface such as a floor. 
     A support member  110  can be sized as needed to fit a variety of different shaped or sized stationary trainers  104 . Support member  110  can provide structural support for bicycle  102  and stationary trainer  104  to attach to dynamic trainer  100 . Support member  110  can be the component of dynamic trainer  100  that connects floating links  120  to stationary trainer  104  and bicycle  102 . Floating links  120  can be the members of the four-bar mechanism that determine the position and angle of stationary trainer  104  and bicycle  102  as the four-bar mechanism moves through its range of motion. Various mechanical means of attachment and methods can be used to fix stationary trainer  104  to dynamic trainer  100  via support member  110  including U-bolts, zip-ties, straps, etc. (not shown) as determined by one skilled in the art. 
     In one example embodiment, a cyclist can attach their bicycle  102  to support member  110  using stationary trainer  104 . Next the cyclist could start a visual simulation program with a data connection to stationary trainer  104 , and the cyclist can get on the bicycle, and start pedaling. When an opportunity for a hill occurs in the visual simulation, then stationary trainer  104  can be engaged by the visual simulation program to allow for increased effort by the cyclist. The cyclist can then utilize the dynamic motion provided by dynamic trainer  100  to experience a more realistic hill climbing effort. 
     In an example illustrated in  FIG. 2 , an embodiment of a dynamic trainer  100  is shown integrated with a stationary bicycle  116 . Support member  110  is integrated into the structure of stationary bicycle  116  so that stationary bicycle  116  can move according to the actions of dynamic trainer  100 . Similar to the embodiment of  FIG. 1 , base  112  can be configured and constructed to provide a stable interface to a substantially flat surface. Various configuration embodiments of dynamic trainer  100  can be integrated into stationary bicycle  116 . 
     The example four-bar mechanism shown in  FIG. 2  is comprised of base  112 , floating links  120 , and side link assemblies  114   a . The four-bar plane of motion is substantially perpendicular to the axis of the four-bar mechanism pivots defined by grounding pivots  126  and floating link pivots  128 . 
     An example dynamic trainer  100  can include support member  110 , floating links  120 , side link assemblies  114   a , and base  112 . Support member  110  can be sized and configured as needed to fit a variety of different shaped or sized stationary bicycles  116 . Support member  110  provides structural support for the remainder of stationary bicycle  116 . 
     In the example dynamic trainer  100  shown in  FIG. 3 , floating links  120  can be part of support member  110  and can allow for connection to side link assemblies  114   a  to support member  110 . Floating links  120  can be provided as moment arms for side link assemblies  114   a  to provide motion to support member  110 . 
     Base  112  can be used for providing stability to dynamic trainer  100  by providing support against the ground as a base for movement of floating links  120  and/or support member  110 . Stanchions  118  can be connected to or integrated into base  112 . Stanchions  118  can provide stationary points, or grounding pivots  126 , that side link assemblies  114   a  can rotate around. 
     Base  112  can include two or more stanchions  118  with grounding pivots  126  to provide a connection between stanchions  118  and side link assemblies  114   a . Stanchions  118  can provide support between support member  110  and base  112  via side link assemblies  114   a . Stanchions can also have different sizes, shapes, and orientations, and can provide support in other directions as desired. Floating link pivots  128  in floating links  120  can provide a means for connecting support member  110  to side link assemblies  114   a.    
     Side link assemblies  114   a  can be used for allowing movement of support member  110  via floating links  120 . Side link assemblies  114   a  can define the range of motion that floating links  120  move through by defining a circular path that certain points, or floating link pivots  128 , on the floating link  120  move through. 
     For example, support member  110  can be fixed to two floating links  120 , wherein support member  110  can force floating links  120  to move together. Each of side link assemblies  114   a  can be connected to floating link  120  at floating link pivots  128 , and to support base  112  at grounding pivots  126 . Side link assemblies  114   a , along with floating link  120  and base  112  can also be oriented in other directions to provide range of motion in these directions as well, if desired. 
     In  FIG. 4 , an example dynamic trainer  100  is illustrated with support member  110  to be attached to base  112  via floating links  120 , side link assemblies  114   a , and stanchions  118 . In the embodiment shown in  FIG. 4 , linear rods  130  are connected at floating link pivots  128 . Support member  110  is then free to move in the fore-aft direction via side link assemblies  114   a  moving along linear rods  130 . 
     For example, support member  110  can be fixed to two floating links  120 , wherein support member  110  can force floating links  120  to move together. Each of side link assemblies  114   a  can be connected to a floating link  120  at one end, and to base  112  at the other end. 
     Additionally, these rotational connections can allow freedom of motion along their pivotal axis as well as the rotation around the said pivotal axis. In the example shown, side link assemblies  114   a  are able to move fore and aft along as well as rotate around linear rods  130 . Spring assemblies  134  can be used to return support member  110  toward a neutral fore-aft position during dynamic fore-aft motion. Linear rods  130  can be retained as needed. Side link assemblies  114   a , along with floating link  120  and base  112  can also be oriented in other directions to provide range of motion in these directions as well, if desired. 
     Base  112  can include two or more stanchions  118  and grounding pivots  126  to provide a connection between stanchions  118  and side link assemblies  114   a . Stanchions  118  can provide diagonal support between support member  110  and base  112 . Stanchions  118  can also have different sizes, shapes, and orientations, and can provide support in other directions as desired. 
     Support member  110  can also have floating link pivots  128  in floating links  120  to provide a means for connecting support member  110  to side link assemblies  114   a.    
       FIG. 5  shows a rear view of an embodiment dynamic trainer  100  in a centered and neutral position for use as a starting point (when attached to stationary trainer  104  and bicycle  102  (as shown in  FIG. 1 , but not shown in  FIG. 5 )). In this position, neutral position instant center  138  is identified by the intersection of the projections of the centerline of the alignment of side link assemblies  114   a . The disposition of side link assemblies  114   a  can be substantially symmetrically connected to support member  110  and base  112 . 
     Each stanchion  118  can contain two or more grounding pivots  126 . In the embodiments shown in  FIGS. 5 and 6 , two grounding pivots  126  can be provided substantially equidistant from the ground plane defined by the bottom of base  112 , although other geometries can be used. Side link pivots  122   a  can be connected to grounding pivots  126  so that side link assemblies  114   a  rotate around the axis of grounding pivots  126 . 
     In the embodiment shown, the top surface of support member  110  is below grounding pivots  126 . In other embodiments not shown, the top surface of support member  110  can be above grounding pivots  126 . 
     Each floating link  120  can include two floating link pivots  128 . Side link pivots  122   b  can be connected to floating link pivots  128  so that floating links  120  and side link assemblies  114   a  rotate relative to each other around the axis of floating link pivot  128 . 
     The pull of gravity in the negative z-direction applied to support member  110  in the center plane of the mechanism can be utilized to position support member  110  into neutral position instant center  138  as illustrated in  FIGS. 1 and 5 . This attribute can make dynamic trainer  100  inherently stable during non-use and during seated riding with small lateral forces applied. 
     With the four-bar mechanism in the neutral position as shown in  FIG. 5 , the projected intersection of the centerlines of side link assemblies  114   a  is the neutral position instant center  138 . With the distance between floating link pivots  128  larger than the distance between grounding pivots  126 , the neutral position instant center  138  will be located above grounding pivots  126 . Additionally, the floating links  120  and support member  110  can be configured so that the neutral position instant center  138  is above the top surface of support member  110 . 
     The four-bar mechanism shown in  FIG. 5  includes a point known as the coupler point  136 . Coupler point  136  is a position fixed relative to floating link  120  and floating link pivots  128 . In the embodiment shown, coupler point  136  is defined as being coincident with the neutral position instant center  138 . In one embodiment, coupler point can  136  also be substantially coincident with the center of bottom bracket  106  (shown in  FIG. 1 , but not shown in  FIG. 5 ). 
     As illustrated in  FIG. 6 , as side link assemblies  114   a  rotate around grounding pivots  126 , floating links  120  and support member  110  tilts and coupler point  136  moves slightly. In the embodiment shown, side link assemblies  114   a  of dynamic trainer  100  can be equal in length, width, and height to provide symmetrical behavior. A shift in a cyclist&#39;s center of mass away from the mechanism center plane, or a torque applied by the cyclist around an axis perpendicular to the mechanism plane of action, can cause coupler point  136  to rotate away from neutral position instant center  138 . The motion of coupler point  136  can be very small, such as between 1-25 mm. 
       FIG. 7  is a side view illustrating the components of dynamic trainer  100  that enable support member  110  to move fore and aft with rider pedaling force input. Side link assemblies  114   a  can include linear bearings  132  to allow side link assemblies  114   a  to move along linear rods  130 . Kinetic energy absorbing components can be included in dynamic trainer  100  to return support member  110 , floating links  120 , and side link assemblies  114   a  from the ends of the fore-aft travel range and toward the center of the fore-aft travel range of dynamic trainer  100 . In the embodiment shown in  FIG. 7 , the energy absorbing components are spring assemblies  134  at the ends of linear rod  130 . Base  112  and stanchions  118 , through side link assemblies  114   a , can provide grounding for the force applied by spring assemblies  134  to react against. 
       FIG. 8  is a detailed view of an example side link assembly  114   a . In this embodiment, rotation of side link assembly  114   a  around pivotal connections made at side link pivot  122   a  can be enabled by two pivot bearings  142 . Pivot bearings  142  can be pressed into the side links  140   a , machined into side links  140   a , or provided by a different connector as needed. 
     Additionally, in this embodiment, rotation of side link assembly  114   a  at pivotal connections between at side link pivot  122   b  can be enabled by linear bearing  132 . Linear bearing  132  can also allow motion along the axis of linear bearing  132 . Linear bearings  132  can be ball bearings, self-lubricating polymer bearings, or other bearings that allow axial and rotational motion. Linear bearings  132  can be pressed into the side links  140   a , machined into side links  140   a , or provided by a different connector as needed. Retainer ring  144  can be used to keep linear bearings  132  from sliding into side link pivot  122   b . Other embodiments can have various types of connectors, bearings, or bearing arrangements and may include washers and/or spacers as needed. 
       FIG. 9  is a detailed view of an example spring assembly  134 . Spring bushings  148  can be designed to have a press-fit interface into the inner diameter of spring  146  so that spring bushings  148  can move with the ends of spring  146 . 
       FIG. 7 ,  FIG. 8 , and  FIG. 9  together illustrate an embodiment for allowing and managing fore-aft motion in dynamic trainer  100 . During dynamic fore-aft motion, floating link  120 , with support member  110  attached, can be returned away from its fore-aft range of motion and toward its center neutral fore-aft position by the reaction force provided by springs  146 . Spring assemblies  134  can be placed at each end of each linear rod  130  to balance out these reaction forces. Spring bushings  148  can be used to provide a smooth interface to linear rod  130 , linear bearing  132 , and floating link  120 . Retainer ring  144  can prevent the reaction force of spring  146  from pushing linear bearing  132  out of side link  140   a.    
       FIG. 10  is a top view of an embodiment of dynamic trainer  100  with another method of returning support member  110  with floating links  120  away from the ends of the fore-aft range of motion. In the embodiment shown, elastic cords  150  are used to move the dynamic trainer  100  away from the limits of fore-aft motion. 
       FIG. 11  is a section view that shows the detail of elastic cords  150  from the embodiment of  FIG. 10 . Elastic cords  150  are shown which can be connected between base  112  and support member  110 . Elastic cords  150  can also be metal coil extension springs. Such elastic cords  150  will pull support member  110  toward the center of the range of fore-aft motion as they reach an equilibrium between the plurality of elastic cords  150 . In this way, many embodiments can be used to provide an interface between the stationary portions of dynamic trainer  100  and the portions of dynamic trainer moving in the fore-aft direction in order to return the moving portions of dynamic trainer  100  toward the center of the fore-aft range of motion after fore-aft force inputs from the rider. 
       FIG. 12  illustrates another example embodiment of dynamic trainer  100 . In this embodiment, the two side link assemblies  114   a  (shown in  FIG. 4  but not in  FIG. 12 ) on either side of dynamic trainer  100  such as in  FIG. 4  can be merged into extended side link assemblies  114   b . Alternatively, an extended side link assembly  114   b  could be applied to the embodiments of  FIG. 3 ,  FIG. 14 , or other embodiments. Side link assemblies  114   b  can pivot on and move along linear rods  130  so that support member  110  can move laterally and fore and aft as in other embodiments of dynamic trainer  100 . 
       FIG. 13  is a detailed view of an example side link assembly  114   b . Extended side link  140   b  can be made to provide side link pivots  122   a  and  122   b  at each end or through the full length of side link  140   b . Side link  140   b  can be made of extruded aluminum, extruded plastic, carbon fiber, or other suitable materials. Linear bearings  132  can be retained in either end of side link pivot  122   b  with retainer rings  144 . In alternate embodiments, a full length bearing sleeve can be used instead of separate linear bearings  132 . Pivot bearings  142  can be pressed into either end of side link pivot  122   a . Note that in other configuration embodiments, the extended side link assembly may be placed inverted compared to the placement in  FIG. 12 . 
       FIG. 14  illustrates an example configuration embodiment of dynamic trainer  100 . In the embodiment shown, the linear rods  130  are fixed to stanchions  118 . Side link assemblies  114   a  such as detailed in  FIG. 8  can be assembled into dynamic trainer  100  so that linear rods  130  pass through linear bearings  132  in side link assemblies  114   a.    
       FIG. 15  and  FIG. 16  illustrate an example configuration embodiment of dynamic trainer  100 . In the embodiment shown in  FIG. 15 , linear rods  130  can be fixed to side links  140   c  and linear bearings  132  can be fixed into grounding pivots  126 . In this embodiment, side links  140   c  along with linear rod  130  are joined together as components of side link assembly  114   c . Linear bearings  132  are fixed into the grounding pivots  126  of stanchions  118 . Support member  110  with floating links  120  and side link assemblies  114   c  move together through linear bearings  132  in the fore-aft direction. 
       FIG. 16  details the composition of side link assemblies  114   c  for this embodiment. A plurality of pivot bearings  142  can be pressed into the side link pivots  122   a  of side links  140   c . Other types of bearings and assembly methods can be used to allow rotation of side link assemblies  114   c  at side link pivots  122   a . As indicated in  FIG. 15 , linear rod  130  can be fixed to side link pivots  122   b.    
       FIG. 17  illustrates an example configuration embodiment of dynamic trainer  100 . Side link assemblies  114   c  shown in  FIG. 16  can be utilized in an inverted way from  FIG. 15 . In the embodiment shown, linear rods  130  can be fixed to side links  140   c  in side link pivots  122   b  and linear bearings  132  can be fixed into floating link pivots  128 . In this embodiment, side links  140   c  along with linear rod  130  are together as components of side link assembly  114   c . Side links  140   c  can remain stationary in the fore-aft direction with stanchions  118  and base  112 . Support member  110  with floating links  120  move along linear rods  130  in the fore-aft direction. 
     While the invention has been described in detail with reference to preferred embodiments thereof, it will be apparent to those skilled in the art that variations and modifications can be made, and equivalents employed without departing from the scope of the appended claims. 
     The embodiments discussed herein provide a means enabling cyclist on a stationary trainer or stationary bicycle to move the bicycle dynamically in ways similar to riding a bicycle outdoors. 
     The four-bar mechanism of the embodiments can provide a means for lateral rotation of the bicycle. The four-bar mechanism can provide a rotation center near the bottom bracket so that the cyclist will not be required to move his or her mass laterally significantly. The four-bar mechanism with thereby enable the cyclist experience a more realistic lateral rotation motion than prior-art rocker plates provide. Additionally, the four-bar mechanism provides an inherent lateral stability that prior-art rocker plates do not. 
     For some embodiments, the linear bearings and linear rods integrated into the four-bar mechanism provide a fore-aft movement in reaction to variations in the pedal forces. This action further enable the cyclist to experience a realistic riding motion.