Abstract: A vehicle where respective inwardly inclined wheels (15) of a steerable wheelset run on respective inwardly sloping faces (54) of a guideway having centreline (39). The vehicle having sensing means for sensing lateral didsplacement of the wheelset relative to a longitudinal reference path. The sensing means signalling a control system including actuating means to steer the wheelset in response to sensed lateral displacement thereof.

Abstract: The invention relates to an axle guide consisting of a fibre-synthetic material composite for guiding an axle in the running gear of a rail vehicle, in particular a high-speed rail vehicle. Said guide has two end sections (11, 11′) for connecting the guide (1) both to the axle and to the chassis (2) of the running gear in a manner resistant to torsion and a central section (12) located therebetween, which has a longitudinal axis (13) aligned with the direction of travel (X) and across-section that is at least partially flat in the vertical direction (Z). The guide (1) has at least one integrated flexural joint (14) with a vertical flexural axis (15) and enables a rotational degree of freedom, which protects the wheel beating from damaging flexural stresses, to be achieved simply without the need for an additional joint component.

Abstract: An arrangement for self-steering, radial bogie, truck or vehicle frame for locomotives and other railroad vehicles, which includes steering beams for and located behind their respective leading and trailing wheelsets, and whose rotary motions are coupled by an inter-axle link to provide opposite transverse movement of the first and third wheelsets upon traversing curves.

Abstract: This invention relates to a method on a truck for railway vehicles to measure the curvature of a track and a method for configuring the steering orientation of an axle of a rail truck as a function of the curvature of the track, which axle is rotationally fastened to a truck frame. The curvature of the track is determined by dividing a yaw rate by a translation rate, and the wheels are oriented on the basis of a setpoint steering angle (&ggr;setpoint) which is calculated by multiplying the track curvature (&khgr;) by one-half the distance between the two axles of the truck.

Abstract: A truck for a railway vehicle has a truck frame with four individual wheels, which are mounted so that they can rotate around horizontal axles, and whereby one wheel pair is driven. To be able to negotiate tight curves with minimal wear, maximum safety and low construction costs, and to be able to achieve higher speeds on straight segments of track, the driven wheel pair can be steered radially with respect to the curve around a common vertical axis as a function of a setpoint determined by a sensor system, while the non-driven individual wheels are combined into a self-steering individual wheel module so that they can each pivot around their own vertical axes, and can be coupled together so that they are synchronized by means of a steering device.

Abstract: A device for transmitting the longitudinal forces of a bogie to the superstructure of a rail vehicle, in particular a motor vehicle with high tractive power. The device includes a transmission rod arranged in the longitudinal direction of the vehicle and comprising two rod parts (4), of which one rod part engages on a pivot point of the superstructure and the other rod part engages on a pivot point of the bogie frame. The two rod parts are connected at a joint which is capable of rotary motion about the transverse axis of the vehicle and is supported vertically relative to the bogie frame. The two rod parts and the joint capable of rotary motion are embodied in a buckle-resistant manner, the joint being connected to the bogie frame in a manner which allows force to be transmitted in both vertical directions.

Abstract: An apparatus for determining the rotation of a wheel truck on a rail vehicle and further for determining the relative direction of motion of said truck with respect to said rail vehicle and further for determining the rate at which the truck moves with respect to the rail vehicle is disclosed, which is a low power radar sensor disposed underneath the rail vehicle and directed toward the truck. In a Preferred embodiment, two sensors are shown which are disposed on opposite sides of the rail vehicle. The sensors are coupled with an onboard computing device and with other components of a train control system which can be used for precisely locating the train on closely spaced parallel tracks and further for updating and augmenting position information used by the train control system. The system including GPS receivers and wheel tachometers for providing alternate sources of information for position determination.

Abstract: A two-wheeled running gear for a track-guided vehicle comprising a running gear frame; a wheel carrier; first and second wheels coupled to opposite sides of the wheel carrier; first and second vertical pivot pins, the first vertical pivot pin coupled to the first side of the wheel carrier and movably connected to the first side of the running gear frame, the second vertical pivot pin coupled to the second side of the wheel carrier and movably connected to the second side of the running gear frame, the first and second wheels located between the first and second vertical pins; and means for controlling a movement of the first pivot pin relative to the running gear frame such that, during a curved track drive, the first pivot pin can be held substantially in place relative to the running gear frame while the second pivot pin can move relative to the running gear frame so that the line connecting the centers of the wheels is maintained substantially parallel to the radius of curvature of the track.

Abstract: A steerable truck apparatus for railroad cars for providing for the controlled and uniform yawing of the axles of the truck. The truck apparatus provides for a yawing response which is linear substantially throughout the range of movement of the axles. The truck is further configured with pivotably supported pedestals for equalized load distribution. An improved axle bearing construction accommodates pivoting of at least one of the axle ends. A damping apparatus provides stiffness in the steering response toward reducing hunting of the wheels during straight line travel.

Abstract: The bogie contains a bogie frame supported on two wheel sets with a coupling device via which the two wheel sets are coupled to one another so as to be steerable in opposite senses. The coupling device contains an additional adjustment device for the transmission of adjustment forces by which a steering movement in the same sense can be transmitted to each of the wheel sets independent of and superimposed on their oppositely directed settings. In this way an influence can be exerted on the shear movement between the wheel sets independently of the bending stiffness between the wheel sets and thus an ideal reaction of the bogie to the respectively arising free lateral acceleration can be achieved.

Abstract: A vehicle suspension system having a pair of hanger brackets. A first intermediate bracket dependent from a vehicle, a second intermediate bracket a pair of control arms, and a torque rod. One end of each control arm is pivotally mounted on a corresponding hanger bracket. Another end of each control arm, is pivotally attached to an axle seat. The torque arm is pivotally mounted between the first and second intermediate brackets. One end of a stabilizer bar is mounted to each control arm to increase the suspensions roll stability, and resistance to lateral deflection. In one embodiment, the stabilizer bar extends through a hole formed in each control arm, and in other embodiments, flanges extend outwardly from the stabilizer bar adjacent respective control arms for mounting the stabilizer bar to the control arms.

Abstract: A railway vehicle has a frame which is suspended on wheelsets each having a live axle. The ends of the axles are mounted in axleboxes. Couplings are provided which are attached to the vehicle frame and which couple an axlebox of one wheelset to an axlebox of another wheelset. The couplings are such as to constrain relative movements between the wheelsets in a lateral plane. In addition, each coupling includes a crank lever which operates to uncouple lateral movements of the frame from the movements of the wheelsets, thereby providing a shear stiffness to the vehicle and reducing vehicle hunting at speed. The crank levers are connected to the wheelboxes by links which are inclined with respect to a longitudinal axis of the frame, such that the links lie on axes which intersect at the longitudinal axis.

Abstract: A self steering railway bogie configured to run on a railway track having two opposed rails defining a track centerline therebetween. The bogie has a forward end and a rearward end and includes a pair of axle sets having a forward axle set and a rearward axle set disposed at the forward end and at the rearward end of the bogie, respectively. Each axle set has a pair of independently rotating wheels defining wheel axes, each wheel being disposed at a respective side of a corresponding axle set and further having a rail-engaging profile such that a wheel of each axle set moving away from the track centerline rises and a wheel of each axle set moving toward the track centerline falls.

Abstract: A vehicle suspension system having a pair of hanger brackets. A first intermediate bracket dependent from a vehicle, a second intermediate bracket a pair of control arms, and a torque rod. One end of each control arm is pivotally mounted on a corresponding hanger bracket. Another end of each control arm, is pivotally attached to an axle seat. The torque arm is pivotally mounted between the first and second intermediate brackets. One end of a stabilizer bar is mounted to each control arm to increase the suspensions roll stability, and resistance to lateral deflection. In one embodiment, the stabilizer bar extends through a hole formed in each control arm, and in other embodiments, flanges extend outwardly from the stabilizer bar adjacent respective control arms for mounting the stabilizer bar to the control arms.

Abstract: A steerable truck apparatus for railroad cars for providing for the controlled and uniform yawing of the axles of the truck. The truck apparatus provides for a yawing response which is linear substantially throughout the range of movement of the axles. The truck is further configured with pivotably supported pedestals for equalized load distribution. An improved axle bearing construction accommodates pivoting of the axle ends. A damping apparatus provides stiffness in the steering response toward reducing hunting of the wheels during straight line travel.

Abstract: The string of vehicles travelling on rails includes bodies (2, 3, 4) articulated together and wheel assemblies (8 to 11), wherein the orientation of the wheels can be adjusted to be tangent to the rails. To this end, an adjusting device includes sensors (40), which make is possible to measure the relative angles (.beta.1, .beta.2) between the longitudinal axes (31) of the bodies. A calculating unit (41) is designed for determining for each unitary vehicle (8 to 11) the variable angle (.alpha.1, .alpha.2, .alpha.3, .alpha.4) between a direction perpendicular to the axes (37) of the wheels and the longitudinal axis (31) of the body concerned, from the values of the relative angles (.beta.1, .beta.2) measured and, preferably, in combination with the angular speed of rotation of the bodies around their vertical axis, measured with gyroscopic sensors provided on the bodies. An adjusting member in the form of a jack then adjusts the orientation of the wheels according to the variable angles calculated.

Abstract: The rail vehicle has at least one truck (1) with two wheelset units (12, 12') which are hingedly connected to one another via a coupling arrangement. This truck (1) is formed as a frameless support arrangement and the vehicle body (17) is supported on spring elements (10) and has at least one guide device or at least one pendulum (11) between the truck (1) and the vehicle body (17). The design is greatly simplified by the omission of the complicated bogie frame and is thus light and compact. The radially adjustable wheelset units (12, 12') can moreover be arranged with a small spacing from one another. The frameless truck (1) is accordingly particularly well suited for rail vehicles on rail networks which have narrow turning radii.

Abstract: A brake control apparatus (8) for a rail car including a truck (14) traveling along a rail (16, 18) includes a truck hunting detection and abatement apparatus (10) for use as part of a brake controller (12). The brake controller (12) is configured for braking the rail car. The apparatus (10) includes a sensor (26) for measuring acceleration of the rail car in a direction transverse to the rail (16, 18), and a control device (24) of the brake controller (12). The control device (24) includes a microprocessor (30) and is responsive to the sensor (26) for comparing the measured acceleration of the rail car with a predetermined acceleration limit. The control device (24) is configured to apply the brakes when the measured acceleration exceeds the predetermined acceleration limit.

Abstract: A railway vehicle has a frame which is suspended on wheelsets (10) each having a live axle (11). The ends of the axles (11) are mounted in axleboxes (12). Couplings (17 to 21) are provided which are attached to the vehicle frame (13) and which couple an axlebox (12) of one wheelset to an axlebox (12) of another wheelset. The couplings are such as to constrain relative movements between the wheelsets (10) in a lateral plane. In addition, each coupling includes a crank lever (19) which operates to uncouple lateral movements of the frame (13) from the movements of the wheelsets (10), thereby providing shear stiffness to the vehicle and reducing vehicle hunting at speed.

Abstract: A vehicle movable along a pair of tracks includes a drive for pivoting the vehicle body with respect to the front and rear wheel assemblies about a pivotal axis parallel to the longitudinal axis of the vehicle body. The wheels include track-engaging surfaces formed with peripheral flanges on the opposite sides extending radially outwardly of the wheel for engaging the sides of the respective tracks. The wheels of each wheel assembly are of metal but all their track-engaging surfaces are covered by resilient material.

Abstract: A railway vehicle truck having side frames which are supported with respect to the journals of spaced apart wheelsets with the respective pair of wheelset axle ends supporting each side frame being constrained to move simultaneously in opposite directions toward and away from each other in response to truck steering impulses.

Abstract: A self-steering wheel truck for use with a railway locomotive or powered transit car in which tractive force is transferred from the axles to the frame through traction rods and steering beams connecting with the end axles. The steering beams are interconnected through upstanding shafts pivotally connected to transverse frame members, control arms and resilient curved diagonal alignment arms. The resilient curved alignment arms move the end axles to equal and opposite angulation under compression for a return to parallel operation upon release of self-steering forces.

Abstract: A railborne vehicle includes a truck frame having wrist blocks for articulatingly fastening wheelset guide rods. An intermediate partial frame is connected to the truck frame. The intermediate partial frame has bearings for fastening or bearing compensating levers.

Abstract: On truck frames having three wheelsets, the invention teaches that the middle wheelset is in contact on each side with the vehicle frame by means of actuators in the lateral direction. These actuators are used to adjust the middle wheelset when the train travels through curves toward the outside of the curve, as a function of the angle of rotation of the truck frame, which is determined by means of measurement elements.

Abstract: The present invention relates to a method of centering steerable axles of a bogie, wherein, on going into a curve in the track, at least one of the axles is steered towards the center of the curve, and wherein each wheel is positioned transversely relative to the track so that each of the wheels is at the same distance from its rail.

Abstract: A steering arm assembly for a railway truck has an undercut compound radius between the body portion and the longitudinal segment on of each side arm in order to decrease the stress intensity at this location, which resultantly provides increased flexural strength to the assembly while maintaining the clearance between the steering arm and truck components.

Abstract: A railroad car truck includes a pair of side frames and a bolster which is supported by springs on the side frame. There are diagonal cross braces attached to the side frames with each cross brace being attached to one side frame on one side of the bolster and being attached to the other side frame on the opposite side of the bolster. There are mounting brackets fixed to the side frame and there is an end block attached with elastomeric mounting elements to each mounting bracket. The end blocks mount the cross braces. Each end block has a profile such as not to materially interfere with the scan area of a hot box detector mounted adjacent one of the railroad track rails.

Abstract: A railborne vehicle has at least two wheelsets. A running gear includes compensating levers for coupling the at least two wheelsets and includes wheelset bearings/axle bearing housings. Guide rod configurations are disposed between the wheelset bearings/axle bearing housings and the compensating levers for radial adjustability. At least one damping element is disposed between one of the compensating levers and one of the guide rod configurations.

Abstract: A railborne vehicle has at least two wheelsets. A running gear includes compensating levers for radially adjusting the wheelsets, and at least one independently controlled control cylinder for influencing a rotary motion of at least one of the compensating levers.

Abstract: On undercarriages for railway vehicles with at least four wheelsets which are combined into trucks, the invention teaches that force-controlled or displacement-controlled actuators are located on the end wheelsets of the trucks. These actuators thereby act on the wheelset bearings, and in terms of their effect, they are connected in parallel, in the case of the force-controlled actuators, and in series, in the case of the displacement-controlled actuator with a wheelset restraint. This system makes possible a controlled rotation of the wheelset in relation to the truck frame.

Abstract: A railborne vehicle includes a truck with two sides and double-axle truck frames, wheelsets with wheels on each side of the truck, wheelset bearing/axle bearing housings for the two wheels of each side, and wheelset guide rods and compensating levers connecting the wheelset bearing/axle bearing housings of the two wheels of each side to one another. A radially adjustable running gear for the railborne vehicle includes a horizontally displaceable but vertically rigid wrist point longitudinally displaceably securing the wheelset guide rod to the truck frame. A connecting guide rod is connected between the wheelset guide rod and the compensating lever. Respective articulation points connect the connecting guide rod to the wheelset guide rod and the compensating lever.

Abstract: A running gear for rail vehicles includes a running gear frame having a central axis and pivot points secured to the running gear frame, a middle wheelset, two end wheelsets and pivot points facing the end wheelsets. Oblique guide rods are each pivotably connected between a respective one of the pivot points secured to the running gear frame and a respective one of the pivot points facing the end wheelsets. The pivot points facing the end wheelsets are disposed farther outward or farther away from the central axis than the pivot points secured to the running gear frame, for generating an a radial or virtually radial adjustment of the wheelset by a transverse motion of the wheelset. Levers transmit the transverse motion of the middle wheelset to the oblique guide rods.

Abstract: In a bogie for rail vehicles, in particular a driven bogie, with a bogie frame, two or more wheelset units which may comprise at least one drive unit and/or brake unit, connected with the bogie frame via a primary suspension, and a secondary suspension for connecting a vehicle body with the bogie frame, a rigid connecting link extends from at least one of the wheelset units for connecting the bogie to the vehicle body. The rigid connecting link is coupled to the wheelset unit at its inertial pole or center of mass.

Abstract: A steerable truck has a pair of wheelsets supporting a pair of laterally spaced side frames. Each wheelset is connected to the sideframe at one end by a pivotal connection and at the opposite end through a steering link to provide relative displacement between the wheelset and sideframe. The connections between the wheelsets and sideframes include upper and lower pivots. One of the pivots has a lower lateral stiffness than longitudinal stiffness to allow movement of the associated wheelset out of plane without inducing torsional loads in the sideframe.

Abstract: The driven running gear is intended for low-platform rail vehicles with at least two body parts which are articulated to each other. It is provided with two individual running gears (2, 2') fitted with steering means (15, 15', 16). The running gears are interconnected to pivot about their horizontal axis beneath the axial center of the wheels (8, 8') by a connecting member (3). The connecting member has at its ends transversely directed support arms (4, 4') for the support of a body part. On the latter there are fastened at least one motor (21, 21') and a brake (23, 23', 24, 24') which drive and brake the running gear (1) via telescopic universal shafts (25, 25') and bevel gearings (26, 26') arranged on the outside of the wheels on both individual running gears (2, 2').

Abstract: A running gear for rail vehicles includes a bogey, truck or vehicle frame. Three driven wheelsets are elastically supported in the frame. Longitudinal guide rods extend parallel to the longitudinal center of the vehicle for coupling rotary motions about vertical axes of the first and third wheelsets with a transverse motion of the second wheelset upon traversing curves. Each of the guide rods have first ends being pivotably secured to a bearing housing of a respective one of the first and third wheelsets and second ends pointing away from the respective bearing housing and toward the second wheelset. Bell cranks are supported on the outside of the frame and have two diagonally opposed pairs of arms pointing toward the longitudinal center of the vehicle and two diagonally opposed pairs of arms pointing toward the second wheelset. The second ends of the connecting rods are each pivotably secured to a respective one of the arms pointing toward the longitudinal center of the vehicle.

Abstract: In a railroad truck, a forced steering system is disclosed for achieving optimal or near optimal wheel set alignment on both straight and curved track sections. Over- and under-steer on curves is minimized and oscillations are minimized or eliminated for trucks transiting straight track sections. A rigid frame and a suspension arrangement, both of which may be used in cooperation with the forced steering system, are disclosed. The forced steering system directs a force, related to the relative orientation between the car body and the truck, to the wheel suspension system thereby altering the wheel set geometry in an optimal manner for both straight and curved track performance.

Abstract: A truck is braced by diagonal struts that are clamped to one another at their intersection. The clamp includes a pair of plates each having a channel to receive one of the struts. An elastomeric member is located between the struts and the plates to permit some flexibility in a vertical direction.

Abstract: A railway vehicle truck includes axles (12) with shrunk-on wheels and journalled in axle-boxes (20) connected to a rigid frame (2,4) through a horizontal primary connection comprising a link (18) coupled to the side member (2) of the frame by a resilient swivel joint (14). At least one of the four axle-boxes (20) is longitudinally slidable on a carriage (36) relative to the side member (2). The sliding motions are controlled by a linkage (22,24,26,30) having its input member (22) connected to the body of the vehicle, or by a damper (34) and an automatic return disposed in parallel relation to each other. The device improves on the operation of trucks taking a curve.

Abstract: A steering arm assembly for a railway truck has compound fillets between the cross-beam or body portion and each sidearm to provide increased flexural strength to the assembly while maintaining the clearance between the steering arm and truck components.

Abstract: A railway vehicle bogie has a pair of levers and twos pairs of links driven by the pair of levers so as to swivel axles. The front and rear axle boxes are spaced longitudinally of the bogie frame and are angularly displaceably mounted at the centers thereof to the bogie frame. The axle boxes carry a vehicle body thereon and support axles therein. First links are angularly displaceably connected to the front axle box while second links are angularly displaceably connected to the rear axle box. A pair of levers are spacedly disposed transversely of the bogie frame and angularly displaceably connected at their intermediate portions to the bogie frame. One of the levers is angularly and displaceably connected to the distal ends of one of the first links and one of the second links thereto while the other is angularly and displaceably connected to the distal ends of the other of the first links and the other of the second links thereto.

Abstract: A bogie for high speed rail vehicles includes an automatic control device for radially adjusting the wheel sets of the bogie. The automatic control device is mounted on the bogie frame along with a damper and a rotation locking device which connects the automatic control mechanism with the body of the vehicle. The automatic control device includes a pair of levers rotatably mounted on either side of the bogie frame. The levers are interconnected in a torsion proof rigid manner, for example, by a rigid pipe.

Abstract: A twin-axle rail-bogie which incorporates a steering mechanism for positively steering one or both of the axles of the rail-bogie in proportion to the rotation of the frame of a structure supported by this rail-bogie. Steering is achieved by slidably mounting one of the axle end supporting assemblies onto the chassis of the bogie so that this assembly is longitudinally slidable and thus causes the one axle having one of its ends connected thereto to pivot forwards or rearwards out of its normal transverse position relative to the transversally opposite supporting assembly which holds the other end of the one axle and then acts as a pivot. An operating arm attached to the frame near the one supporting assembly is used for moving via a linking mechanism the one supporting assembly in such a direction as to cause the one axle held by this supporting assembly to pivot in the same direction but at an angle smaller than and proportional to the frame with respect to the chassis of the bogie.

Abstract: A railway truck for a railway vehicle which has steerable axles has axle bearings supported by support pedestals. Each support pedestal is located longitudinally by a flexible bar element which aallows the pedestal sufficient vertical movement to accommodate varying load conditions and also allows rotation about a horizontal axis which is not coincident with the axle bearings but restrains horizontal movement fore and aft of the rotational axis. A steering assembly reacting to relative rotational movements between the truck and the vehicle permits pivoting of the support pedestals about the horizontal axis. The tipping of the pedestal moves the axle bearing in the fore and aft direction which effectively rotates the axle about a vertical axis so as to guide the axle of the railway truck into radial alignment with respect to a curved track. The structure has the effect of an "inverted" pendulum, that is a pendulum with negative restoring force.

Abstract: The present invention is based on the critically important feature of providing a left-right parallel arranged linear motor-based conveying system in which the upper surfaces of the guide rails do double duty as providing the rolling surfaces for the wheel pairs, and also as being secondary (reaction) conductor surfaces for the linear motors, and the linear motors are spaced closely above the upper surfaces of the guide rails by a predetermined clearance.

Abstract: A hinged bogey for rail vehicles, the bogey comprising two longitudinal members, two cross-members each fixed to one of the longitudinal members, and a hinge device enabling each longitudinal member to pitch about a central transverse axis. The hinge device comprises a shaft and four bearings, each cross-member including one of the bearings adjacent to the longitudinal member to which it is fixed, and one of the bearings at its opposite end. The bogey is applicable to any rail vehicle.

Abstract: A railway car bogie has a bearing (11,12) at the center of each of the front and rear axles (2) and a pair of struts (13, 14) arranged in a V connected at one end to each bearing to define an imaginary center of rotation at or adjacent the center of the bearing and at the other end to the bogie frame (5). By mounting the axle boxes (4) for lateral and longitudinal sliding movement relative to the axle springs (9, 10) around the imaginary center of rotation, a railway car (25) mounted on the bogie exhibits greater stability for high speed straight running and easier passage around tight curves.

Abstract: A chassis for an articulated vehicle comprises a pair of chassis portions pivotally connected to a central longitudinal beam. The beam is supported by inboard wheelsets and the chassis portions are supported by outboard wheelsets. Each portion is hinged intermediate its ends to permit elevation of one end relative the other. A body is supported on the wheelsets.

Abstract: A rail vehicle guide and support arrangement including a bogie having independent wheels, has a crossbeam fastened to a vehicle body, so as to be perpendicular to the vertical plane containing the longitudinal axis of the vehicle, in proximity to one end of the body. Two longitudinal members each equipped with at least two wheels are mounted on an articulation member carried by the crossbeam on each side of the vertical lane, and connected to each other by a brace which is mounted on a ball joint. Each longitudinal member is provided with an articulation and each is composed of a longitudinal frame member articulated to the crossbeam and extended by a directional arm which is articulated, about a substantially vertical pivot, to the longitudinal frame member and is equipped at its free end on a wheel. Each directional arm is connected to the brace by rods forming a deformable quadrilateral which ensures correct orientation of the wheels while traversing curves.

Abstract: The articulated device for the guidance and levitation of a rail vehicle is composed of a deformable support equipped with at least four independent wheels and comprising a horizontal crossmember and two longitudinal members pivotable and tiltable relative to the crossmember. The two longitudinal members, each equipped with at least two wheels and mounted longitudinally on articulated elements, carry the crossmember on either side of the longitudinal vertical plane of the vehicle, so as to be directionally pivotable in a horizontal plane and, on the other hand, tiltable in a vertical plane in order to make it possible for the wheels carried by the longitudinal members connected to one another by means of a link and ball-mounted to follow the curves of the track and pass over the inequalities of the latter. According to the invention, the crossmember, at its ends, carries pivots for the articulation of longitudinal members, having variable relative positions.