Abstract:
A lawn mower has a dual-tubular frame for shock absorption. The dual-tubular frame has two parallel, longitudinally-extending tubular structures with curved portions allowing for flexion. A seat bracket interconnects the tubular structures. An engine is mounted to the tubular structures rearward of the seat bracket.

Description:
TECHNICAL FIELD 
     The present disclosure relates to vehicles, and in particular, to vehicles configured for lawn maintenance including mowing. 
     BACKGROUND 
     Grass is commonly maintained with lawn care machinery such as, for example, lawn mowers, lawn tractors, and/or the like. Walk-behind lawn mowers are often compact and inexpensive, and are usually configured with comparatively small engines of less than about 200 cubic centimeters (cc). At the other end of the spectrum, ride-on lawn tractors can be quite large, have engine sizes generally exceeding 400 cc, and can be configured with various functional accessories (e.g., trailers, tillers, and/or the like) in addition to grass cutting components. Riding lawn mowers often fall in the middle, providing the convenience of a riding vehicle as well as a typically larger cutting deck as compared to a walk-behind lawn mower. 
     However, prior riding lawn mowers have been unable to overcome various difficulties. For example, certain prior lawn mowers have required large, expensive engines in order to obtain sufficient operative power to carry a rider and/or to drive a desired size of cutting deck. Other riding lawn mowers have been expensive, having prices similar to prices of lawn tractors. Yet other riding lawn mowers have been undesirably large when boxed or otherwise configured for transportation and/or sale, limiting the types of vehicles that may be used to transport the lawn mower to a desired location (for example, from a retail store to the home of a purchaser). 
     SUMMARY 
     This disclosure relates to systems and methods for riding lawn mowers and components thereof. In an exemplary embodiment, a riding lawn mower comprises a cutting deck coupled to a cutting blade, and an internal combustion engine having a displacement of less than 225 cubic centimeters. The internal combustion engine is coupled to the cutting blade via a friction drive. 
     In another exemplary embodiment, a drivetrain for a riding lawn mower comprises a friction wheel, and an engine flywheel coupled to a deck drive. The engine flywheel is frictionally engageable with the friction wheel, and the flywheel comprises a neutral bearing centrally located thereon. The drivetrain further comprises a differential comprising at least one plastic gear. The differential is coupled to the friction wheel in order to transfer power to at least one drive wheel of the riding lawn mower. 
     The contents of this summary section are provided only as a simplified introduction to the disclosure, and are not intended to be used to limit the scope of the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       With reference to the following description, appended claims, and accompanying drawings: 
         FIG. 1A  illustrates an exemplary riding lawn mower in accordance with an exemplary embodiment; 
         FIG. 1B  illustrates a block diagram of components of an exemplary riding lawn mower in accordance with an exemplary embodiment; 
         FIG. 1C  illustrates configuration of an engine with respect to an exemplary riding lawn mower in accordance with an exemplary embodiment; 
         FIG. 2  illustrates an exemplary riding lawn mower frame in accordance with an exemplary embodiment; 
         FIG. 3A  illustrates a neutral bearing system for a friction drive in accordance with an exemplary embodiment; 
         FIG. 3B  illustrates a friction wheel for a friction drive accordance with an exemplary embodiment; 
         FIG. 4  illustrates a drivetrain for a riding lawn mower including a friction drive in accordance with an exemplary embodiment; 
         FIG. 5A  illustrates an exploded view of a differential for a riding lawn mower in accordance with an exemplary embodiment; 
         FIG. 5B  illustrates an assembled view of a differential for a riding lawn mower in accordance with an exemplary embodiment; 
         FIG. 6A  illustrates an exploded view of a dual pulley and brake system for a deck drive of a riding lawn mower in accordance with an exemplary embodiment; 
         FIG. 6B  illustrates an assembled view of a dual pulley and brake system for a deck drive of a riding lawn mower in accordance with an exemplary embodiment; 
         FIG. 7  illustrates a deflector for a riding lawn mower in accordance with an exemplary embodiment; 
         FIGS. 8A and 8B  illustrate a foot rest for a riding lawn mower in accordance with an exemplary embodiment; and 
         FIG. 9  illustrates a seat for a riding lawn mower in accordance with an exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     The following description is of various exemplary embodiments only, and is not intended to limit the scope, applicability or configuration of the present disclosure in any way. Rather, the following description is intended to provide a convenient illustration for implementing various embodiments including the best mode. As will become apparent, various changes may be made in the function and arrangement of the elements described in these embodiments, without departing from the scope of the appended claims. For example, the steps recited in any of the method or process descriptions may be executed in any order and are not necessarily limited to the order presented. Moreover, many of the manufacturing functions or steps may be outsourced to or performed by one or more third parties. Furthermore, any reference to singular includes plural embodiments, and any reference to more than one component or step may include a singular embodiment or step. Also, any reference to attached, fixed, connected or the like may include permanent, removable, temporary, partial, full and/or any other possible attachment option. As used herein, the terms “coupled,” “coupling,” or any other variation thereof, are intended to cover a physical connection, an electrical connection, a magnetic connection, an optical connection, a communicative connection, a functional connection, and/or any other connection. 
     For the sake of brevity, conventional techniques for mechanical system construction, management, operation, measurement, optimization, and/or control, as well as conventional techniques for mechanical power transfer, modulation, control, and/or use, may not be described in detail herein. Furthermore, the connecting lines shown in various figures contained herein are intended to represent exemplary functional relationships and/or physical couplings between various elements. It should be noted that many alternative or additional functional relationships or physical connections may be present in a practical light riding vehicle, for example a riding lawn mower. 
     Principles of the present disclosure reduce and/or eliminate problems with prior riding lawn mowers. For example, various riding lawn mowers configured in accordance with principles of the present disclosure are configured to utilize smaller and/or less expensive engines, for example engines having displacement of up to 224 cc. Other riding lawn mowers configured in accordance with principles of the present disclosure are configured to be smaller and/or lighter than certain prior riding lawn mowers in order to, for example, be able to fit in certain common passenger vehicles (e.g., minivan, sport utility vehicle, light truck, and/or the like) when boxed for retail sale. For example, an exemplary riding lawn mower configured in accordance with principles of the present disclosure is configured with a dry, unboxed weight of about 87 kilograms and a wheelbase of about 112 centimeters. Yet other riding lawn mowers configured in accordance with principles of the present disclosure are configured to be manufacturable at a reduced expense as compared to certain prior riding lawn mowers. 
     In various exemplary embodiments, a riding lawn mower is configured with a friction drive. As used herein, a “friction drive” generally refers to a powertrain where power is transferred from the engine to at least one other operational component of the powertrain via frictional engagement of two parts (for example, a flywheel and a friction wheel perpendicular to one another), rather than solely via a conventional drive shaft and gearset. 
     In various exemplary embodiments, with reference to  FIG. 1A , riding lawn mower  100  comprises a steerable powered vehicle configured with various components for mowing a lawn. For example, riding lawn mower  100  comprises frame  110  coupled to a cutting deck  184  having at least one corresponding cutting blade. Moreover, riding lawn mower  100  may be configured with any suitable components configured to allow an operator to mow grass, for example a deflector  180 , a footrest  182 , a seat  186 , and/or the like. 
     With reference now to  FIG. 1B , in various exemplary embodiments, riding lawn mower  100  further comprises engine  130  coupled to friction wheel  140 . Engine  130  is coupled to friction wheel  140  via a flywheel  134  and neutral bearing system  136 . Friction wheel  140  is coupled to differential  150 , for example, via one or more of driveshafts, pinions, chains, and/or the like, in order to transfer power to differential  150 . Differential  150  transfers operational power to ground drive  160  Flywheel  134  is also coupled to deck drive  170  via, for example, one or more of belts, pulleys, driveshafts, pinions, chains, and/or the like. 
     In various exemplary embodiments, engine  130  comprises an internal combustion engine, for example an internal combustion engine fueled by gasoline, diesel fuel, ethanol, and/or any other suitable fuel. Engine  130  may be configured with a displacement from about 175 cc to about 224 cc. Engine  130  may comprise an engine typically utilized for a walk-behind lawn mower. In one exemplary embodiment, engine  130  comprises a Briggs and Stratton model W14 engine having a displacement of about 190 cc. Moreover, engine  130  may comprise any engine configured to provide sufficient power to enable suitable operation of riding lawn mower  100  (e.g., partial or full operation of the ground drive and partial or full operation of the deck drive while supporting the weight of an operator). 
     In various exemplary embodiments, with momentary reference to  FIG. 1C , engine  130  may be configured with respect to the other components of riding lawn mower  100  so as to achieve a desired configuration of the center of gravity of engine  130 . For example, engine  130  may be coupled to riding lawn mower  100  such that the center of gravity of engine  130  is located “ahead” (e.g., closer to the front of riding lawn mower  100 ) of the rear axle of riding lawn mower  100 . Moreover, engine  130  may also be coupled to riding lawn mower  100  such that the center of gravity of engine  130  is located “behind” (e.g., closer to the rear of riding lawn mower  100 ) the front axle of riding lawn mower  100  and/or the center of gravity of riding lawn mower  100 . In this manner, engine  130  may be located so as to reduce and/or minimize mechanical components coupling engine  130  to ground drive  160  and/or deck drive  170 , for example by eliminating a belt coupling engine  130  to ground drive  160 . 
     With reference now to  FIGS. 1A and 2 , in various exemplary embodiments, riding lawn mower  100  is configured with a frame  110  (e.g., frame  210 ). In an exemplary embodiment, frame  210  is configured with a pair of tubular structures (a “dual-tubular” frame). Frame  210  is configured to provide structural support to riding lawn mower  100 . Frame  210  may comprise one or more of steel, aluminum, titanium, iron, and/or other suitable metals and/or alloys thereof. In an exemplary embodiment, frame  210  comprises HSLA 50 A-10 1102 hot rolled steel tubing having an outer diameter of between about 3.0 centimeters to about 3.5 centimeters. Moreover, frame  210  may further comprise various plates, brackets, flanges, fasteners, and/or the like, as suitable, in order to couple to and/or support other components of riding lawn mower  100 . 
     In an exemplary embodiment, frame  210  is configured with a dual-tubular design in order to provide flexion within frame  210 , responsive to riding lawn mower  100  passing over uneven ground. The spacing between tubes comprising frame  210  may be suitably varied, as desired, in order to obtain a desired rigidity and/or other mechanical characteristics of frame  210 . 
     In various exemplary embodiments, frame  210  is configured with one or more curved portions  210 A. In this manner, frame  210  may be configured to at least partially “flex” or bend in a suitable direction (e.g., in a vertical direction), responsive to an applied force. By varying the bend radius of curved portions  210 A, the dimensions of frame  210  (e.g., the outer diameter, the inner diameter, the wall thickness, etc.), placement of various coupling brackets  212 , and the like, frame  210  may be configured to flex in a desired manner. For example, frame  210  is configured to flex in a manner such that riding lawn mower  100  responds to an applied force as if riding lawn mower  100  were configured with a conventional shock absorber system (e.g., springs, struts, linkages, and/or the like). In this exemplary embodiment, frame  210  is configured to provide the equivalent of about 2 centimeters (2 cm) of suspension travel. In other exemplary embodiments, frame  210  is configured to provide the equivalent of between about 1 cm and about 10 cm of suspension travel. In this manner, riding lawn mower  100  may be configured with an improved level of comfort for an operator, for example by reducing shock transferred to the rider. Moreover, by providing a suspension-like function, frame  210  may reduce wear on and/or damage to other components of riding lawn mower  100 . 
     Frame  210  may be monolithic. Alternatively, frame  210  may comprise multiple components coupled together. Moreover, frame  210  may be cast, pressed, sintered, die-cut, machined, stamped, bonded, laminated, polished, smoothed, bent, rolled, molded, plated, coated, and/or otherwise shaped and/or formed via any suitable method and/or apparatus. 
     In various exemplary embodiments, with reference now to  FIGS. 1B and 3A , engine  130  is mounted to frame  210 . Engine  130  is coupled to friction wheel  140  via a flywheel  134  configured with a neutral bearing system  136  (e.g., neutral bearing system  336 ). In an exemplary embodiment, neutral bearing system  336  comprises a bearing  337  and a cover plate  338 . Cover plate  338  may be configured with a flange  339  extending at least partially into bearing  337  in order to couple thereto. 
     In an exemplary embodiment, flywheel  134  is coupled to engine  130  (for example, coupled to the crankshaft of engine  130 ) via a fastener disposed through a cavity generally located in the center of flywheel  134 . Bearing  337  may be disposed in the cavity. In an exemplary embodiment, an outer surface of bearing  337  is coupled to flywheel  134  (e.g., via frictional engagement). An inner surface of bearing  337  is coupled to cover plate  338  (e.g., via frictional engagement). In this manner, flywheel  134  may be coupled to engine  130  in order to facilitate operation of the friction drive, while maintaining a suitably continuous surface across which friction wheel  340  may traverse during operation of the friction drive. 
     In an exemplary embodiment, bearing  337  comprises a needle bearing. In another exemplary embodiment, bearing  337  comprises a roller bearing. In yet other exemplary embodiments, bearing  337  comprises a ball bearing. Moreover, bearing  337  may comprise any suitable components and/or mechanisms configured to allow cover plate  338  to remain fixed with respect to friction wheel  340  when cover plate  340  is engaged by friction ring  341 , while flywheel  134  is permitted to rotate. 
     In various exemplary embodiments, flywheel  134  comprises steel. In other exemplary embodiments, flywheel  134  comprises powdered metal. In these embodiments, flywheel  134  may be infused with copper or other suitable material in order to provide desirable frictional and/or structural characteristics of flywheel  134 . In an exemplary embodiment, flywheel  134  comprises a material having a hardness exceeding that of aluminum, for example a hardness in excess of 60 HRb on the Rockwell B scale. Moreover, flywheel  134  may comprise any suitable material configured to frictionally engage with friction wheel  340  in order to transfer force to other components of riding lawn mower  100 . Flywheel  134  may be configured to be suitable for use over a variety of operating RPM ranges of engine  130 , for example from about 0 RPM up to about 4000 RPM. 
     In various exemplary embodiments, with reference now to  FIGS. 3B and 4 , friction wheel  140  (e.g., friction wheel  340 ) is configured to frictionally engage with flywheel  134 . Friction wheel  340  comprises friction ring  341  coupled to wheel body  342 . Wheel body  342  is configured to provide structural support to friction wheel  340 . Moreover, wheel body  342  is configured to couple to other power transfer components (e.g., a driveshaft), in order to transfer force received via friction ring  341 . In an exemplary embodiment, wheel body  342  couples to a driveshaft via a suitably shaped cavity  343  in order to transfer rotational force. 
     Friction ring  341  may comprise any suitable material configured to frictionally engage flywheel  134 . In an exemplary embodiment, friction ring  341  comprises rubber. In another exemplary embodiment, friction ring  341  comprises a composite. Friction ring  341  may be removed from wheel body  342  and replaced with a new ring, as suitable, for example responsive to wear. 
     In various exemplary embodiments, riding lawn mower  100  is configured to reduce flat spotting on friction ring  341 . As used herein, “flat spotting” generally refers to wearing of a non-round area on friction ring  341  caused by flywheel  134  continuing to rotate when friction wheel  340  is frictionally coupled to flywheel  134  close to or at the center of flywheel  134 . In this position (“neutral”), friction wheel  340  does not transfer rotary motion from flywheel  134 , but simply suffers frictional wear at the exterior (e.g., on friction ring  341 ). The resulting wear and consequent “out of roundness” of friction ring  341  reduces the effectiveness of later frictional engagement between friction wheel  340  and flywheel  134 . For example, as the flat spot on friction ring  341  passes over flywheel  134 , slippage can occur, leading to undesirable lagging, surging, and/or otherwise uneven power delivery. 
     In order to reduce flat spotting, various prior approaches for friction drives have disengaged a friction wheel and a flywheel in the neutral position and/or positions close thereto. In contrast, in various exemplary embodiments, flywheel  134  and friction ring  341  remain in frictional engagement in the neutral position. Flat spotting of friction ring  341  is prevented because, at the neutral position, friction ring  341  is in contact with cover plate  338  which is rotatably supported by bearing  337 . Thus, cover plate  338  remains fixed with respect to friction ring  341 , while flywheel  134  continues to rotate, eliminating flat spotting of friction ring  341 . Instead of rotational wear on friction ring  341 , rotational movement of hearing  337  occurs. In this manner, prolonged life of friction ring  341  may be achieved. Moreover, riding lawn mower  100  may thus be configured with smoother, more reliable power transfer between engine  130  and other components of riding lawn mower  100 . 
     In an exemplary embodiment, when friction wheel  340  is displaced across flywheel  134  in a first direction out from the center of flywheel  134 , riding lawn mower  100  is operative in a “forward” direction. Conversely, when friction wheel  340  is displaced across flywheel  134  in a second direction (opposite the first direction) out from the center of flywheel  134 , riding lawn mower  100  is operative in a “reverse” direction. In various exemplary embodiments, the mechanical components configured to displace friction wheel  340  in the reverse direction simultaneously operate a “reverse” direction indicator, for example via a lever arm closing an electrical contact. In this manner, an operator may be notified of “reverse” operation each time riding lawn mower  100  enters operation in the reverse direction. 
     Once power is transferred from engine  130  to friction wheel  340 , it may then be delivered to other components of riding lawn mower  100 , for example to a differential  150 . With reference now to  FIGS. 1B, 5A, and 5B , in an exemplary embodiment, a differential  150  (e.g., differential  550 ) comprises a plurality of gears (e.g., one or more of ring gears, planet gears, side gears, and/or the like). One or more gears comprising differential  550  may comprise plastic or other suitable structural material, for example in order to reduce one or more of noise, weight, cost, and/or the like. 
     In an exemplary embodiment, differential  550  comprises at least one differential shaft  552 . Differential shaft  552  may comprise any suitable structural material configured to transfer torque, for example, steel, aluminum, titanium, iron, and/or the like. In an exemplary embodiment, differential shaft  552  comprises elevated temperature drawing (“ETD”)  150  steel. Differential shaft  552  may be monolithic. Differential shaft  552  may also comprise multiple portions. Moreover, portions of differential shaft  552  may coupled to one another in any suitable manner. In an exemplary embodiment, portions of differential shaft  552  are coupled to one another via a dowel pin. In this manner, the portions of differential shaft  552  may be aligned with respect to one another, as desired. 
     In an exemplary embodiment, differential  550  is coupled to the rear wheels of riding lawn mower  100 , for example via a drive gear associated with each rear wheel. The drive gear for each rear wheel may comprise any suitable material and/or be configured with any suitable diameter and/or tooth pattern, as desired. In an exemplary embodiment, the drive gear for each rear wheel comprises plastic. In other exemplary embodiments, the drive gear for each rear wheel comprises glass-filled nylon, for example nylon filled with from about 20% to about 40% glass. 
     Turning now to  FIGS. 1B, 6A and 6B , in various exemplary embodiments, riding lawn mower  100  is configured as a “single belt” system. Stated another way, riding lawn mower  100  is configured with one belt coupling engine  130  to deck drive  170 , but no other belts. In various prior riding lawn mowers and/or lawn tractors, a “dual belt” system is utilized, where one belt couples the engine and the deck drive, and another belt couples the engine and the ground drive. In contrast, a single-belt system in accordance with principles of the present disclosure allows for reduced complexity and reduced manufacturing expense. 
     In various exemplary embodiments, riding lawn mower  100  is configured as a “dual pulley” system. Stated another way, riding lawn mower  100  is configured with two pulleys for adjusting tension on a belt coupling engine  130  and deck drive  170 . In various prior riding lawn mowers and/or lawn tractors, a “single pulley” system is utilized. In contrast, a dual-pulley system in accordance with principles of the present disclosure allows for greater geometric advantage when varying the tension on an associated belt. 
     In an exemplary embodiment, a deck drive  170  (e.g., deck drive  600 ) comprises a belt  610  routed about pulleys  610  and  620 . Pulleys  610  and/or  620  may be spring-loaded or otherwise configured to impart a desired tension to belt  610 , for example responsive to operation of a clutch. Belt  610  transfers force to deck pulley  640  which is coupled to a cutting blade configured to cut grass. As the clutch is engaged, pulleys  620  and  630  move, taking up slack in belt  610  and thus gradually engaging belt  610  against pulleys  620 ,  630 , and  640  in order to turn a cutting blade coupled to pulley  640 . As the clutch is released, pulleys  620  and  630  move in an opposite direction, reducing tension in belt  610  and thus at least partially disengaging belt  610  from pulleys  620 ,  630 , and  640 . Thus, force is no longer delivered to the cutting blade, and the cutting blade eventually ceases rotation. 
     In various exemplary embodiments, pulleys  620  and  630  are configured with an extended height in order to allow for greater vertical displacement of pulley  640  and/or other components of deck drive  600 . In an exemplary embodiment, pulleys  620  and  630  are configured with a height at least twice the height of belt  610 , providing additional room for belt  610  to move with respect to pulleys  620  and  630 . In this manner, deck drive  600  can accommodate increased vertical displacement as compared to deck drives lacking pulleys with extended heights. 
     In order to reduce the likelihood of injury, it is desirable for a cutting blade to more rapidly come to a stop when a clutch is disengaged. Thus, in various exemplary embodiments, riding lawn mower  100  is configured with a linked clutch and brake system. Continuing with reference to  FIGS. 6A and 6B , one or more structural components  650  (e.g., brackets, linkages, couplers, and/or the like) are coupled to pulleys  620  and/or  630 . Structural components  650  may further be coupled to various braking components (e.g., components configured to impart a drag force to a cutting blade, a wheel, a pulley, and/or the like, such as a brake caliper, a brake disk, etc). In this manner, in these exemplary embodiments, disengagement of the clutch simultaneously activates braking components, bringing the cutting blade to a stop more rapidly. 
     With reference now to  FIG. 7 , in various exemplary embodiments, riding lawn mower  100  is configured with a deflector  700 . Deflector  700  is configured to at least partially guide, contain, and/or control material ejected from the cutting deck of riding lawn mower  100 . For example, deflector  700  may be configured with various suitable angles, lengths, curvatures, and/or the like, in order to achieve a desired pattern of grass clippings ejected from the cutting deck. 
     In an exemplary embodiment, deflector  700  is configured with a loop  720  configured to allow an operator to grasp it. In this manner, deflector  700  may be moved, raised, lowered, and/or otherwise adjusted, for example in order to vary the path of debris ejected from the cutting deck or to remove an obstruction, without an operator (or with minimal) needing to reach underneath deflector  700  to grasp it. In this manner, deflector loop  720  allows an operator to move deflector  700  without exposing the operator to the debris path beneath deflector  700 . 
     In an exemplary embodiment, deflector loop  720  is a loop. In other exemplary embodiments, deflector loop  720  may comprise a flange, a knob, a rod, a handle, and/or the like, or other suitable component configured to allow an operator to move deflector  700  without exposure to a debris path. 
     Turning now to  FIGS. 8A-8B , in various exemplary embodiments, riding lawn mower  100  is configured with a footrest  800 . Footrest  800  is coupled to frame  210 . Footrest  800  may comprise any suitable structural material, for example plastic, metal, composite, and/or the like. In an exemplary embodiment, footrest  800  comprises glass-filled polypropylene in an amount from about 15% glass to about 40% glass. In various exemplary embodiments, footrest  800  is configured with edges  800 A and  800 B cantilevered away from frame  210 . Edges  800 A and  800 B may be cantilevered any suitable distance (e.g., about 15 centimeters), while still remaining strong enough to support the weight of an operator of riding lawn mower  100 , for example an operator weighing about 100 kilograms. In various exemplary embodiments, footrest  800  is configured with inserts  810 . Inserts  810  may provide cushioning and/or grip for the feet of an operator, as desired. 
     With reference now to  FIG. 9 , in various exemplary embodiments, riding lawn mower  100  is configured with a scat  900 . Scat  900  is configured to accommodate an operator. In an exemplary embodiment, seat  900  comprises calcium filled polypropylene, for example from about 20% to about 30% calcium. In another exemplary embodiment, seat  900  comprises VistaMaxx™ brand polypropelyne based elastomers manufactured by ExxonMobil Chemical. 
     In various exemplary embodiments, seat  900  is configured with a gas chamber about the exterior of seat  900 . In this manner, seat  900  may be configured with suitable structural characteristics and/or manufacturing characteristics, for example ease of molding. Moreover, seat  900  may be configured with various padding components, for example snap-in padding components  910 A and  910 B. Scat  900  may be coupled to frame  210  and/or other portions of riding lawn mower  100 , as suitable. 
     In an exemplary embodiment, riding lawn mower  100  is configured with a foot-operated bypass. Stated generally, a “bypass” refers to components configured to disengage a ground drive without disengaging a deck drive, allowing riding lawn mower  100  to operate a deck drive while remaining stationary and/or moving only under the influence of gravity (for example, down a hill). In various prior lawn mowers, operation of the bypass required use of a hand, for example grasping the end of a lever and pulling. In contrast, riding lawn mower  100  is configured with a foot-operated bypass (for example, a bypass operated via a downward force applied by a foot), eliminating the need to bend over to operate the bypass. In an exemplary embodiment, operation of the foot-operated bypass of riding lawn mower  100  results in physical disengagement of flywheel  134  from friction wheel  140 , preventing transfer of power to differential  150  and thus preventing powered operation of ground drive  160 . 
     In an exemplary embodiment, riding lawn mower  100  is configured with a constant load clutch. Many previous riding lawn mowers have been configured with an “over center” clutch which rapidly engages the engine to components of the drivetrain. In contrast, in various exemplary embodiments, riding lawn mower  100  utilizes a constant load clutch wherein engine  130  and deck drive  170  are gradually engaged over a range of angular motion of a clutch lever arm. In various exemplary embodiments, the constant load clutch engages over a range of angular motion of the clutch lever arm from about 15 degrees to about 40 degrees. In an exemplary embodiment, the constant load clutch engages over a range of angular motion of the clutch lever arm of about 25 degrees. In this manner, load is placed on engine  130  in a gradual fashion, reducing the likelihood of engine  130  stalling. Thus, a smaller, less powerful, and/or less expensive engine  130  may be utilized in riding lawn mower  100  as compared to prior riding lawn mowers. 
     In various exemplary embodiments, with momentary reference again to  FIG. 1A , riding lawn mower  100  is configured with a self-centering cutting deck  184 . As used herein, “self-centering” generally refers to a cutting deck configured to return to a centered position with respect to the sides of lawn mower  100  after being displaced. For example, when an operator steps on cutting deck  184 , cutting deck  184  and/or components coupling cutting deck  184  to frame  210  are configured to flex, bend, slide, and/or otherwise move responsive to the applied force. Thus, cutting deck  184  may move sideways a certain distance. Once the applied force is removed, for example when an operator removes a foot, cutting deck  184  returns to a centered position. Self-centering may be achieved, for example, via suspending cutting deck  184  from frame  210  in a suitable manner, for example by utilizing angled metal bars having similar dimensions. Responsive to displacement of cutting deck  184 , the bars generate a force tending to move cutting deck  184  back to a centered position. Springs and other mechanical approaches may also be utilized, as suitable. 
     While the principles of this disclosure have been shown in various embodiments, many modifications of structure, arrangements, proportions, the elements, materials and components, used in practice, which are particularly adapted for a specific environment and operating requirements may be used without departing from the principles and scope of this disclosure. These and other changes or modifications are intended to be included within the scope of the present disclosure and may be expressed in the following claims. 
     The present disclosure has been described with reference to various embodiments. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the present disclosure. Accordingly, the specification is to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of the present disclosure. Likewise, benefits, other advantages, and solutions to problems have been described above with regard to various embodiments. However, benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential feature or element of any or all the claims. As used herein, the terms “comprises,” “comprising,” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. When language similar to “at least one of A, B, or C” or “at least one of A, B, and C” is used in the claims or specification, the phrase is intended to mean any of the following: (1) at least one of A; (2) at least one of B; (3) at least one of C; (4) at least one of A and at least one of B; (5) at least one of B and at least one of C; (6) at least one of A and at least one of C; or (7) at least one of A, at least one of B, and at least one of C.