Abstract: An assembly includes a steering shaft and a primary drive system eccentrically coupled to the steering shaft and configured to transfer a torque applied to the steering shaft to a vehicle steering system. The assembly also includes a secondary drive system coupled to the steering shaft and configured to transfer the torque applied to the steering shaft if the primary drive system is inactive and substantially unable to transfer the torque.

Abstract: The invention provides a steering hub system driven by a ball joint universal rotary motor, including a hub body and a connection mechanism. The hub body is connected to a vehicle suspension via the connection mechanism. The hub body includes a ball joint universal rotary motor inside; the ball joint universal rotary motor includes a rotatable spherical shell-shaped rotor body having an opening, a spherical stator body disposed within the rotor body and connected to the connection mechanism, a first coil assembly and a second coil assembly both wound on the spherical stator body; when the first coil assembly is energized, the spherical shell-shaped rotor body rotates with respect to a first axis of the spherical stator body, and when the second coil assembly is energized, the spherical shell-shaped rotor body rotates with respect to a second axis of the spherical stator body, the first axis is not identical to the second axis.

Abstract: A method for estimating steering assistance provided by a power steering system of a vehicle may include correlating an internal torque applied by an adaptive steering system of the vehicle with an external torque applied to a steering assembly of the vehicle. The method may also include estimating the steering assistance based on the correlation.

Abstract: A system and a method of controlling a power steering system of a vehicle are provided. A control system includes a control module operable to determine a rack force of the vehicle based on at least one of a motor velocity, a driver torque and a motor torque, determine a plurality of modeled rack forces based on a roadwheel angle and a vehicle speed, compare the rack force to the plurality of modeled rack forces to generate a friction level included in a control signal, and send the control signal to the power steering system.

Abstract: The invention relates to a heavy goods vehicle in which the steering system (12) comprises, in addition to a normal steering mode steering device (26) that transfers steering power purely mechanically by means of connecting rods (34) from axle to axle, a crab steering mode steering device (28) that also transfers steering power purely mechanically by means of connecting rods (46) from axle to axle. The individual wheel assemblies (14, 16, 18, 20, 22, 24) can be connected by means of coupling devices (56) either to the normal steering mode steering device (26) or to the crab steering mode steering device (28).

Abstract: A resisting force change mechanism includes a first portion and a second portion configured to change a resisting force against relative displacement. The first portion is supported on any one of a first side member, a second side member, a first cross member, and a second cross member of a link mechanism where at least a portion thereof is superposed on one member at all times. The first portion is aligned with the one member and a steering shaft at the front. The second portion is supported on any other one of the body frame, the first side member, the second side member, the first cross member, and the second cross member that is displaced relative to the one member on which the first portion is supported. The second portion is located at a position where at least a portion thereof is superposed on the other member at all times.

Abstract: A motor vehicle assembly that includes a strengthening member having a twelve-cornered cross section along at least a portion of the strengthening member, and an automotive component having a four-cornered cross section along at least a portion of the automotive component. The cross section of one of the strengthening member and the automotive component transitions between twelve corners and four corners to facilitate a connection between the strengthening member and the automotive component.

Abstract: A first hydraulic damper includes one end portion attached to a first attachment position of a vehicle body. A second hydraulic damper includes one end portion coupled to the other end portion of the first hydraulic damper via a linking member, and the other end portion attached to a second attachment position of the vehicle body. Each of the first and second hydraulic dampers includes a hydraulic cylinder, a piston, a piston rod, a free piston, a compression coil spring, first and second working oil passages to cause first and second oil chambers to communicate with each other, and working oil passage throttles. The first hydraulic damper, second hydraulic damper, and the linking member are coupled in the longitudinal direction. One of the hydraulic cylinder and piston rod is attached to the vehicle body, and the other is coupled to the linking rod.

Abstract: A cowl structure of the vehicle is provided. The cowl structure of the vehicle includes a cowl top panel that extends in a width direction of the vehicle and coupled to a dash panel that divides an engine and passenger compartment, and a cowl lower panel that extends in the width direction of the vehicle, is coupled to the dash panel to divide the engine and passenger compartment, and is disposed at a lower side than the cowl top panel in the vertical direction of the vehicle. Further, a cowl upper supporting member has an upper portion coupled to the cowl top panel and a coupling component of the cowl top panel and the dash panel and a lower portion coupled to the cowl lower panel. A cowl lower supporting member is coupled to the cowl lower panel and the dash panel.

Abstract: A closure panel including an outer shell for closing an opening defined by a vehicle body and an inner reinforcement. The outer shell and inner reinforcement are formed as a plurality of additive layers. The inner reinforcement includes an integral thickened edge formed around the periphery of the outer shell, an integral latch buttress provided on a first side of the inner reinforcement and a pair of integral hinge buttresses provided on a second side of the inner reinforcement. Internally threaded protrusions may be formed as additive deposits on the integral buttresses.

Abstract: A support structure in a framework construction is provided. The support structure includes a first and a second rod of an axle support of a motor vehicle, a positioning element, and a first and a second fiber winding. The positioning element fixes an alignment of the first rod relative to an alignment of the second rod. A first support section of the positioning element is drawn by the first fiber winding in the direction of a support section of the first rod, and a second support section of the positioning element is drawn by the second fiber winding in the direction of a support section of the second rod in order to hold the first and second rods in the fixed alignment relative to each other by a frictional connection.

Abstract: This invention relates to an apparatus, system and method for adjustable support of an extension of a vehicle cargo bed. The apparatus provides a range of horizontal, vertical, diagonal and angular adjustment of a vehicle cargo bed extension deck so as to accommodate a wide variety of differently designed and dimensioned vehicles and provides other features promoting reliability and safety while minimizing unwanted vibration during use.

Abstract: A rear spoiler device for a vehicle at least includes an air-guiding element (25) for lengthening the contour, in particular of a side surface (3) of the vehicle (1), in a travel position, and a displacement device for displacing the air-guiding element (25) between the travel position and a home position. A front end (54) of the air-guiding element (25) is provided for bearing against the side surface (3) of the vehicle (1) in the travel position. At least one sealing element (61) for sealingly bearing against the side surface (3) is provided on the front end (54) of the air-guiding element (25), and the displacement device is provided for pressing the sealing element (61) against the side surface (3) in the travel position.

Abstract: An aerodynamically effective attachment part or spoiler extension is disclosed. The spoiler extension includes a guide arrangement having a first guide element formed between the spoiler extension and a base body of the spoiler arrangement. Transfer of the spoiler extension is guided from a release position, in which the spoiler extension is detachable from the base body, along at transfer direction into a locking position, in which the spoiler extension is secured on the base body. The spoiler extension includes a securing element able to secure the spoiler extension automatically on the base body of the spoiler arrangement in the locking position.

Abstract: An automotive chassis which has an H-shaped base mounted to a vehicle. An electric motor having a rotatable axis is mounted to a metal floor situated in a square, box-shaped center in the H-shaped base. A metal disk is coupled to the axis of the electric motor, and rotation of the axis of the electric motor causes rotation of the metal disk, creating a centrifugal force that stabilizes the vehicle.

Abstract: An automobile spare tire anti-theft device is disclosed. In an embodiment, the device includes a cap and retainer assembly. The cap can be configured to cover a portion of the yoke and the cable coupling extending from the underside of the yoke, including for example an extension and spring assembly. The cap can be secured in place by engaging the cap retainer positioned on the opposite side of the hub of the rim. Example features of example embodiments of the cap and retainer are disclosed herein.

Abstract: A mobile robot 1 having a plurality of kinds of moving forms includes a body unit 11 having a front face and a back face, four limb units 12 having a plurality of limb-side drive shafts, and front end tools 13 provided on a front end side of the limb units 12. A base end side of the limb unit 12 is connected to the body unit 11. The four limb units 12 are the same units. The body unit 11 and the four limb units 12 are movable by switching a front face side and a back face side so that a moving operation of the front face side and a moving operation of the back face side are symmetrical across the center of a thickness direction of the body unit 11.

Abstract: A modular electric vehicle system, allowing for the assembly of many different vehicle configurations using a plurality of interchangeable vehicle assembly modules, including at least two powered vehicle assembly modules in an assembled vehicle each of which has self-contained drive and power systems and controls which can be connected together by a central network bus on the vehicle. At least one of the powered vehicle assembly modules will be a steering module, with the necessary additional controls and components to steer the axle thereon and in turn steer the assembled vehicle. The connection of the network bus and the modules would be done in an interchangeable way so that different modules could be interchangeably placed in the assembled vehicle. Various steering systems, control methodologies and vehicle attachments are also disclosed.

Abstract: The solar power system for auxiliary-powered brakes and power system for a tractor-trailer is a supplemental electrical system adapted for use with the trailer of a tractor-trailer. The solar power system for auxiliary-powered brakes and power system for a tractor-trailer is designed to: 1) assist in the acceleration of the trailer; 2) use braking energy to generate and store electricity; 3) supplement the stored energy with a renewable source; and, 4) distribute excess energy to the trailer electrical system. In one potential embodiment of the disclosure, the solar power system for auxiliary-powered brakes and power system for a tractor-trailer provides for tapping into the stored electrical energy for external use. The solar power system for auxiliary-powered brakes and power system for a tractor-trailer comprises a plurality of photovoltaic cells, one or more axle assist devices, an electricity storage device, and a distribution system.

Abstract: A multipurpose stand includes a first supporting unit, a second supporting unit and a vertical member. the first supporting unit includes the main body and the roller, the second supporting unit includes the first broad member, the second broad member and the third broad member, The vertical member comprises the first vertical section, the second vertical section and the enlarged end, wherein the second supporting unit is formed by cutting a plate material into the first broad member and the second broad member. The member connected with the third broad member is connected with the connecting member through a single point of the second supporting unit and the first supporting unit, and a vertical member is set between the first broad members of the second supporting unit.

Abstract: A seat attachment device is provided that uses a single bolt to secure the seat rails to the seat attachment device and the seat attachment device to a post.

Abstract: Attachment and detachment work of a detachable part is facilitated, while achieving secure attachment thereof, in a part attachment structure of straddle type vehicle including the detachable part attached to a body frame. A seat supporting member includes a base portion spanning paired right and left seat frames, and paired right and left extension portions, which are displaceable in the lateral direction, and extend in the longitudinal direction along the paired right and left seat frames, respectively, from the base portion; the base portion is fixed by being fastened to a body frame; each of the paired right and left extension portions includes an upper locking portion, both lateral locking portions, and a lower locking portion; and the lock on the seat frames is engaged or released by only moving the extension portions in two directions.

Abstract: A stabilizing arrangement for a tilting running gear of a non-rail-borne vehicle is disclosed. The stabilizing arrangement includes a balance beam configured to have each end coupled to a respective suspension side of a multi-track running gear axle of the tilting running gear. A pivot bearing is connected to a frame or body of the vehicle and defines a stationary axis of rotation. The pivot bearing rotatably supports the balance beam about the stationary axis of rotation. At least one stabilizing element is connected to the balance beam and is supported with respect to a frame or body of the vehicle. The at least one stabilizing element is configured to provide a reaction force to counteract a tilting moment of the vehicle. A non-rail-borne vehicle comprising the stabilizing arrangement also is disclosed.

Abstract: An axle adapter assembly, configured for enabling conversion of an axle installed on a vehicle to fit different center bore sizes of wheel hubs, including: an axle configured for coupling dropouts of fork legs of a lower fork; adapters configured for being inserted within the dropouts; the adapters configured for engaging an outer surface of the axle and retaining the axle upon engagement; and axle pinch shims configured for being inserted into slits of the dropouts and the adapters, wherein upon the insertion, the adapters are aligned with the dropouts, such that shoulders of the adapters retain edges of a wheel hub of the wheel hubs.

Abstract: An object is to provide a front fork including a stroke sensor as well as a damping force variable device, and allowing structure of the front fork to be simplified. A front fork of an embodiment includes a pair of a first leg and a second leg. The first leg includes a stroke sensor section that detects a stroke amount of the front fork as a distance between extension and compression of the front fork. The second leg includes a damping force variable device that controls a flow of a working fluid contained in the second leg to enable a damping force to be varied.

Abstract: A rear wheel suspension system pivotably attached to a bicycle. The suspension system has an upper link attached to a main frame at a first pivot point, and a rear stay member attached to the upper link at a second pivot point. A lower link is attached to the main frame at a third pivot point, and is pivotably attached to the rear stay member at a fourth pivot point. A shock absorber is pivotably connected to the upper link and to the main frame. An instantaneous center of rotation (ICR) is defined where an upper axis extending through the first and second pivots intersects a lower axis extending through the third and fourth pivots. The ICR displaces along a trajectory from behind the bottom bracket, through an inflection point at which the upper axis and the lower axis are parallel, to in front of the bottom bracket, as the shock absorber compresses.

Abstract: An electric bike is described and includes an air speed sensor to sense air speed at the bike, an electric motor to impart motive force to the bike, and a controller operatively connected to the motor, the controller to control the electric motor using the air speed sensed by the air speed sensor. The controller includes a set electric-motor parameter for the output power of the motor. The electric-motor parameter can be bike speed. The controller can also use ground inclination to determine the power to be output by the motor to assist in powering the bike. The controller can use ground inclination to determine the power to be output by the motor to charge a battery in the bike. The controller can set the power of motor assist to be greater in a greater headwind than in a lighter headwind. The controller uses rider weight and rider height as parameters for controlling the motor.

Abstract: A bicycle derailleur comprises a base member adapted to be mounted to a bicycle, a movable member movably coupled to the base member, and a chain guide coupled to the movable member. The chain guide is coupled for rotation around a rotational axis (X), and a biasing element biases the chain guide in a selected rotational direction. A resistance applying unit applies a resistance to rotational movement of the chain guide in a direction opposite the selected rotational direction, and an adjusting unit adjusts an amount of resistance applied by the resistance applying unit.

Abstract: An extendable hull system movable between a mono-hull to a multi-hull configuration is provided so as to take advantage of both types of hull designs depending on the boating conditions. The extendable hull system provides a center hull portion and two side hull portions, each with separate planing surfaces in an expanded multi-hull configuration, and providing a shared planing surface in the contracted mono-hull configuration. The extendable hull system provides a pivotably connected railing system along a periphery of the side hull portions for moving to a deployed configuration providing additional walking surface. The extendable hull system provides a retractable awning movable between positions for covering the mono-hull and the multi-hull configuration.

Abstract: A boat includes a hull, a deck, an engine disposed between the hull and the deck, and a jet propulsion unit including a jet nozzle configured to jet water therefrom. The jet nozzle includes a hole to which a water passage is connected and is configured to supply pressurized water from the jet nozzle to a water intake opening located in an interior of the hull. The water intake opening is connected to an interior water passage disposed in the interior of the hull and between the hull and the deck. The interior water passage is connected to a deck hose used to wash the boat.

Abstract: A method for cycling autonomous underwater vehicles (AUVs) that record seismic signals during a marine seismic survey. The method includes deploying plural current AUVs on the ocean bottom; recording the seismic signals during the marine seismic survey with plural current AUVs; releasing from an underwater base a new AUV to replace a corresponding current AUV from the plural current AUVs; recovering the current AUV; and continuing to record the seismic signals with the new AUV.

Abstract: The invention relates to a water sport device having a sitting or standing surface (2) for a person practicing water sports, a jet drive (8) and a pivotable nozzle (13), wherein a fin (23) is disposed at the nozzle (13) and is arranged in a fixed position relative to said nozzle.

Abstract: An outboard-motor vibration-isolating cooler system apparatus providing a retrofit substitute for the midsection and the lower unit of a standard outboard motor, having a substitute closed-loop cooling system with an exterior heat exchanger, a substitute oil reservoir, a substitute exhaust system, and a substitute propulsion system with an isolating power-take-off shaft, allowing an existing standard outboard-motor powerhead to be used in conditions not conducive to standard open-loop water cooling, such as shallow-water, muddy-water, obstructed-water, seawater, or corrosive-water conditions.

Abstract: A high altitude balloon, including a method and machine for manufacture, uses a perimeter border strip to couple two circular balloon panels with a lap or butt seal. Simultaneous sealing of two perimeter seals, one between the border strip and each of two balloon panels, is provided by supporting stacked balloon panels on a rotatable support and sealing around the full perimeter of the two interposed balloon panels and the border strip. The method and machine for manufacture allow for the mass production of high altitude balloons and minimize necessary material handling. The perimeter border strip can be dispensed and guided relative to the perimeter of the balloon panels for positioning before sealing together, as a bonding device is rotated relative to the balloon envelope.

Abstract: A balloon system includes a balloon having a balloon membrane extending between an upper apex and a lower apex opening. The lower apex opening extends through the balloon membrane at a balloon lip. A ballonet is within the balloon. The ballonet is coupled with the balloon membrane at the lower apex opening. The ballonet includes a lower ballonet panel having a lower perimeter edge and a ballonet orifice extending through the lower ballonet panel at a ballonet lip and an upper ballonet panel having an upper perimeter edge. The upper and lower ballonet panels are coupled along the respective upper and lower perimeter edges. A lower apex fitting couples the ballonet with the balloon at the balloon lip of the lower apex opening.

Abstract: An aircraft skin panel includes a laminated composite layer and a ground plane coupled to the composite layer, wherein the ground plane is an electrically conductive elastic thermoplastic.

Abstract: A ball-lock type fastening device for connecting a work piece to a structure is disclosed. The fastening device includes a number of features designed to improve the reliability, repeatability and strength of the locking mechanism compared to traditional ball-lock fasteners. The features include the shape of the locking balls, the shape of the retention housing which engages the locking balls, and mechanisms for controlling deployment and retraction of the locking balls.

Abstract: Aircraft, wing-to-body fairing assemblies, and air exchange systems are provided. An aircraft includes a fuselage, a wing secured to the fuselage, an outer skin panel, and an air exchange system. The outer skin panel is secured to the wing and/or the fuselage and at least partially defines a cavity. The air exchange system is secured to the outer skin panel and exchanges air between the cavity and an external environment. The air exchange system includes an air inlet, a diffuser, and a silencer. The air inlet is disposed in the outer skin panel and accommodates an air flow between the cavity and the external environment. The diffuser is attached to the air inlet and has a varying cross sectional area to change the speed of the air flow. The silencer is attached to the diffuser and communicates the air flow between the diffuser and the cavity and reduces noise.

Abstract: A method and control system for an aircraft engine comprising a gas turbine driving a fan propeller with a mechanical gear-train and a dedicated pitch change mechanism for the fan propeller includes a fuel flow signal input; a pitch change mechanism signal input; a controlled plant for relating a pitch change mechanism pitch angle (BetaP) and a fuel flow (Wf) to at least two controlled outputs and a set of constraints. A decoupling control decoupling the controlled plant and/or the constraints into two separate single-input single-output (SISO) control loops for the first and second controlled outputs and a decoupling control decoupling the constraints from the decoupled controlled outputs and the constraints from one another provide gas turbine and fan propeller coordinate control while coordinately controlling constraints and outputs. A feedforward control can compensate the load change effect on engine speed and fan propeller rotor speed control.

Abstract: A vehicle, such as an airplane sets a limit for a control variable used to deflect a control surface. The limit is set as a function of an unfavorable flight condition/target angle of attack and a rate of change of angle of attack so that a pilot control variable command is prevented from exceeding the limit to prevent the vehicle from reaching an unfavorable flight condition and/or exceeding a desired angle of attack limit.

Abstract: A spoiler assembly is provided that is engageable to a UAV that defines a body, an outer surface and an inner surface. The spoiler assembly comprises a spoiler, translatably connected to the UAV inner surface adjacent a first portion of the spoiler aperture. The spoiler defines an upper surface and an outer surface, the upper surface being substantially the same size and shape as the spoiler aperture. A spoiler shroud is connected to the UAV inner surface and extends within the UAV body about at least a portion of the spoiler aperture. A spoiler activating mechanism is secured to the UAV inner surface and connected the spoiler lower surface. The mechanism is operative to translate the spoiler between a first position wherein the spoiler upper surface is substantially flush with the UAV outer surface, and second a position, wherein the spoiler upper surface is disposed substantially within the UAV body.

Abstract: An aircraft landing gear longitudinal force control system for an aircraft having landing gears with braking and/or driving wheel(s). The system includes an error-based force controller having feedback for minimising any error between the demanded force and the actual force achieved by the force control system. The feedback may be derived from force sensors on the landing gear for direct measurement of the landing gear longitudinal force. The force control system may include an aircraft level landing gear total force controller and/or a landing gear level force controller for each actuated landing gear.

Abstract: The embodiments of the present invention disclose a method and a device for driving a rotor. The method comprises: receiving a flight control command; obtaining current rotational states of first motors corresponding to first actuators and the current rotational states of second motors corresponding to second actuators; determining required first rotational states of the first motors according to the flight control command and the current rotational states of the first motors; determining required second rotational states of the second motors according to the flight control command and the current rotational states of the second motors; controlling the first motor to rotate in a corresponding first rotational state so as to drive first blade clamping bodies to twist relative to a lower rotor hub; controlling the second motor to rotate in a corresponding second rotational state so as to drive second blade clamping bodies to twist relative to an upper rotor hub.

Abstract: A safe, quiet, easy to control, efficient, and compact aircraft configuration is enabled through the combination of multiple vertical lift rotors, tandem wings, and forward thrust propellers. The vertical lift rotors, in combination with a front and rear wing, permits a balancing of the center of lift with the center of gravity for both vertical and horizontal flight. This wing and multiple rotor system has the ability to tolerate a relatively large variation of the payload weight for hover, transition, or cruise flight while also providing vertical thrust redundancy. The propulsion system uses multiple lift rotors and forward thrust propellers of a small enough size to be shielded from potential blade strike and provide increased perceived and real safety to the passengers. Using multiple independent rotors provides redundancy and the elimination of single point failure modes that can make the vehicle non-operable in flight.

Abstract: A rotorcraft (1) having: a lift rotor (5); a wing (10) extending from a first end (11) carrying a first propulsive propeller (21) to a second end (12) carrying a second propeller (22); landing gear (30); and a tail (40). The rotorcraft (1) is provided with two fuselages (51, 52) secured to said wing (10) between said first and second propulsive propellers (21, 22) in such a manner as to present an inter-fuselage space (60) having no propeller between said fuselages (51, 52), each fuselage (51, 52) including at least one undercarriage of said landing gear (30).

Abstract: The invention provides a fluid propulsion augmentation arrangement and method, capable of also generating control moments (23), providing increased thrust (45) at reduced speed, reduced drag at increased speed, under conditions in which traditional approach cannot provide sufficient performance. It consists of a wing (10) located in a propulsion system (11) fluid intake region (13), having a slanted trailing edge (16) coinciding with a fraction of the propulsion intake (17), pivotally connected (14), allowing position adjustments. At reduced speed, the wing (10) and the propulsion system intake (17) are placed adjacently, the intake low pressure determines wing (10) fluid-dynamic force (44) generation. Increasing speed, wing (10) position varies, following fluid stream (15) convergence change, maintaining an angle of attack for increased L/D, ensuring increased performance, and also varying control moments (23).

Abstract: A device includes a propulsion unit configured to move the device and a steering unit configured to control the direction of the device. The device also includes a power unit configured to provide power to the propulsion unit and a charging unit configured to use an electric field to provide electrical power to the power unit. The device further includes a first magnetic sensor configured to determine a vector of one or more magnetic fields and a processor communicatively coupled to the propulsion unit, the steering unit, the power unit, and the magnetic sensor. The processor is configured to receive, from the magnetic sensor, a time-varying signal indicative of a magnetic field and determine, based on the time-varying signal, that the magnetic field is associated with an electrical power transmission line. The processor is further configured to cause the steering unit to direct the device toward the electrical power transmission line.

Abstract: An external load mass rope for attachment to a cargo hook device of a rotorcraft that comprises at least one first cargo hook and at least one second cargo hook, the external load mass rope comprising at least one first rope leg and at least one second rope leg, wherein the at least one first rope leg is adapted for attachment to the at least one first cargo hook and the at least one second rope leg is adapted for attachment to the at least one second cargo hook, characterized in that at least one of the first and second rope legs comprises an associated length adjustment unit that is adapted to shorten or lengthen the at least one of the first and second rope legs in operation on the basis of associated operating parameters.

Abstract: An elevator system includes a shaft extending between at least two decks of a vehicle. A base of the shaft is mounted to a deck structure of at least two decks by a coupling mechanism that accommodates flexing of the deck structure to enable the deck structure to flex independently of the base of the shaft. The elevator system further includes a cab within the shaft. The cab is movable between the at least two decks. The elevator system also includes a pneumatic system in selective communication with an interior of the shaft.

Abstract: An aircraft armrest may incorporate a rail roller linkage. The roller linkage may include an armrest plate, a rail attached to an aircraft seat assembly, a top roller link, and a bottom roller link. The top roller link may have a threaded upper adjustment cylinder, a pivot joint, and a pair of grooved rollers diagonally disposed on either side of the pivot. The bottom roller link may have an unthreaded lower adjustment cylinder, a pivot joint, and a pair of grooved rollers diagonally disposed on either side of the pivot. The grooved rollers may mesh with the rail. The roller linkage may include a roller adjustment screw, having a threaded portion, and extending through both of the adjustment cylinders. A compression spring may bias the roller link around the rail and may be disposed between the top roller link and the bottom roller link and surrounding the roller adjustment screw.