Abstract: The invention relates to a forest machine, comprising a chassis having sides, a swing bogie mounted on bearings to the chassis, comprising a swing frame, second sides and at least two wheels, a swing bearing attaching the chassis to mount the swing bogie, a power transmission arranged through the swing bearing in connection with the chassis, a support formed by two pairs between the chassis and the swing frame, each pair having a protrusion as a support surface and a rail as a counter surface to transmit lateral forces between the chassis and the swing frame during contact between the two surfaces, wherein each pair is located at a distance from the swing bearing on separate side of the swing bearing, and in each pair, one of the protrusions and the rail is attached to the side of the chassis and other to the second side of the swing frame.

Abstract: Disclosed embodiments include track mounts configured to secure a track assembly to a frame of a power machine, and power machines including the same. The track mounts include a mounting flange which secures to a side of the power machine frame. The track mounts also include a connecting structure extending between the mounting flange and a tack frame of the track assembly.

Abstract: An ATV is shown having a steering system comprised of a power steering unit having drive and driven pitman arms coupled to a drag link. The drive pitman arm is laterally offset from a vehicle centerline and is driven by the power steering unit. An alternate power steering system includes a pack and pinion subassembly coupled to a power steering motor, which then couples to steering arms of the ATV.

Abstract: A working machine with a crawler includes a lower traveling body having a pair of crawlers, an upper turning body, an extension beam installed rotatably to be parallel in a longitudinal direction of the crawler, a fitting portion opened in a side frame of the crawler, a fixing pin fixing the extension beam to the side frame, a fixing pin insertion hole, a fixing pin fitting hole, and a reinforcement rib, in which the extension beam extends to be inserted into the fitting portion, and the reinforcement rib is provided at a center portion of an opening of the fitting portion, and the fixing pin fitting hole is disposed at a position which is deviated from an imaginary center line extending along a longitudinal direction of the fitting portion from the center portion and does not interfere with the reinforcement rib.

Abstract: The drilling rig includes a first substructure and a second substructure. The second substructure is positioned generally parallel to and spaced apart from the first substructure and generally the same height as the first substructure. The drilling rig further includes a drill floor coupled to the first and second substructures, where the drill floor positioned substantially at the top of the first and second substructures.

Abstract: A tractor includes a frame including an axle, the axle including an axle shaft and a beam member. A cab is mounted to the frame, the cab including controls for controlling the tractor. A ground-engaging mechanism coupled to the axle, the second ground-engaging mechanism including a track assembly. The track assembly includes an undercarriage assembly, a carrier housing, a ring gear, and a track, where the carrier housing includes a pivot arm for pivoting coupling to the undercarriage assembly. The ring gear defines an outer diameter, and the axle shaft and beam member are adjustably coupled to the carrier housing at a location inside the outer diameter.

Abstract: The use of self-powered, autonomous vehicles in agricultural and other domestic applications is provided. The vehicles include a self-propelled drive system, tracks or wheels operatively connected to the drive system, a power supply operatively connected to the drive system, an attachment mechanism for attaching equipment to the vehicle, and an intelligent control operatively connected to the drive system, power supply, and attachment mechanism. The vehicle is configured to connect to the equipment to perform agricultural operations based upon the equipment. Multiple vehicles can be used in a field at the same time. Furthermore, the invention includes the ability to move one or more of the autonomous vehicles from field to field, home to field, or from generally any first location to a second location.

Abstract: A track hitching structure is for a wheeled crane and the wheeled crane, and includes a vehicle frame and a connecting cross beam. The first end of the connecting cross beam is connected with a track. The second end of the connecting cross beam is connected with the vehicle frame. The second end of the connecting cross beam is higher than the first end of the connecting cross beam. The vehicle frame is connected with the track by the connecting cross beam with one high end and one low end, so the long-distance force transfer from the track to the race of the vehicle frame can be handled, then the shortcomings of tedious structure, large size, large weight and the like of the connecting device caused by a horizontal connecting cross beam are avoided, and the reliability and the working performance of the entire crane are improved.

Abstract: A variable tread width system is disclosed for a track work vehicle. The track work vehicle has a differential gear case and at least one axle shaft. The variable tread width system includes a drive wheel removably coupled to the axle shaft to receive a torque to drive the track. The drive wheel is movable relative to the axle shaft between a first orientation and a second orientation. The system also includes a saddle assembly coupled to the differential gear case. The saddle assembly includes at least one rail movable relative to the differential gear case, and the saddle assembly is movable independently of the drive wheel. The drive wheel cooperates with the saddle assembly to define a plurality of tread widths for the track work vehicle.

Abstract: The invention provides a trenching apparatus and a method of using a trenching apparatus. The trenching apparatus (100) may include a main body portion (10), trench cutting equipment (50) depending from the main body portion, at least two ground contacting units (16) arranged on opposed sides of the main body portion and on which the main body portion is supported, each of the ground contacting units being connected to the main body portion by a respective independently operable suspension assembly (20), the respective suspension assemblies being configured to compensate for unevenness of the ground thereby to maintain the trench cutting equipment in a desired angular orientation with respect to the vertical.

Abstract: An electric device is provided. The device includes an electric machine having a rotatable first shaft extending from an end of the machine. The device also includes a gearbox operably connected to the electric machine. The gearbox includes a first gear rotatably supported in the gearbox and a first gear connectable to the first shaft. The first gear is adapted to mesh with the second gear. The electric machine and the gearbox are adapted to drive a pump.

Abstract: A mobile crane includes a main body and extendable axles, which are selectively re-positioned relative to the main body through strategically positioned apertures. The axles may be automatically locked to the main body in a desired one of the multiple positions without operator intervention. The axles one or more tapered ends for connecting to side frames, which may support crawler tracks. The tapered ends of the axles extend through openings located in the frames such that they are removably connected to an outside or exterior portion of the frames relative to the main body.

Abstract: A working machine having a chassis, a first track assembly including a first track mounted for movement around a first track support, the first track assembly being mounted to the chassis by at least a first beam, the first beam being moveable relative to the chassis to vary the distance between the chassis and the first track assembly, a second track assembly including a second track mounted for movement around a second track support, the second track support defining a second inner face, the working machine having an extended position and a retracted position such that the first track assembly is spaced further from the second track assembly when in the extended position than when in the retracted position, wherein when the working machine is in the retracted position a first portion of the first beam is positioned outboard of the second inner face.

Abstract: A mobile crane includes a main body and extendable axles, which are selectively re-positioned relative to the main body through strategically positioned apertures. The axles may be automatically locked to the main body in a desired one of the multiple positions without operator intervention. The axles one or more tapered ends for connecting to side frames, which may support crawler tracks. The tapered ends of the axles extend through openings located in the frames such that they are removably connected to an outside or exterior portion of the frames relative to the main body.

Abstract: A tractor has hydraulically driven wheels at a cab end and castor wheels at an engine end. Each driven wheels is driven by a hydraulic motor with a continuous adjustment of the motor displacement, with the motor being driven by a pump also having continuous displacement. The motor displacement is controlled by an electronic controller in response to stroking of the speed control lever to manage the displacement to provide required drive torques at different points in the stroke. There is provided an automatic steering system having a guidance controller arranged to receive GPS position information which controls the steering by differentially adjusting the displacement of the motors so that the automatic steering is independent of the manual steering which controls the pumps.

Abstract: A mobile crane includes a main body and extendable axles, which are selectively re-positioned relative to the main body through strategically positioned apertures. The axles may be automatically locked to the main body in a desired one of the multiple positions without operator intervention. The axles one or more tapered ends for connecting to side frames, which may support crawler tracks. The tapered ends of the axles extend through openings located in the frames such that they are removably connected to an outside or exterior portion of the frames relative to the main body.

Abstract: The present invention relates to a telescopic crawler chassis and engineering machinery having the telescopic crawler chassis, comprising a left crawler frame, a right crawler frame and a base, further comprising at least one hollow left sliding beam and at least one right sliding beam. One end of the hollow left sliding beam is fixedly connected with the left crawler frame, and one end of the right sliding beam is fixedly connected with the right crawler frame. At least one hollow sliding seat is arranged on the base, one end of the hollow left sliding beam is movably inserted into an hollow sliding seat from the left end of the hollow sliding seat, and one end of the right sliding beam is movably inserted into an hollow sliding seat and also into the hollow part of the hollow left sliding beam from the right end of the hollow sliding seat. The change or conversion of the state of the engineering machinery can be more convenient, and the whole machine walks and operates more stably, safely and reliably.

Abstract: The object of the invention is to reduce the amount of investment required for the usage-optimized configuration and installation of large cranes. This object is achieved by a large mobile crane having an undercarriage, a drive unit (16), a revolving superstructure (18), one or more control stations (17), at least two jibs (3), at least one counter-jib (4), at least two lifting arrangements (22) and counterweights arranged separately or on the basic structure, characterized in that the load-bearing parts of the crane (3, 4, 20) and the mobility-specific parts (5, 6, 7) are of modular design and can be supplemented by exchangeable and/or supplementary parts, wherein the structural units (modules) used essentially correspond, or are similar, to existing standard-crane components, and an increase in load-bearing capacity can be achieved by arranging a number of these in the large crane.

Abstract: A construction vehicle includes first and second track assemblies. The track assemblies each include an inner portion, and outer portion and a middle portion between the inner portion and the outer portion. An adjustment mechanism is pivotably coupled to the middle portions of the first and second track assemblies. The adjustment mechanism extends and retracts along a width axis to adjust a distance between the first and second track assemblies. The width of the first and second track assemblies can determine an overall width of the construction vehicle.

Abstract: A working machine having a chassis, a first track assembly including a first track mounted for movement around a first track support, the first track assembly being mounted to the chassis by at least a first beam, the first beam being moveable relative to the chassis to vary the distance between the chassis and the first track assembly, a second track assembly including a second track mounted for movement around a second track support, the second track support defining a second inner face, the working machine having an extended position and a retracted position such that the first track assembly is spaced further from the second track assembly when in the extended position than when in the retracted position, wherein when the working machine is in the retracted position a first portion of the first beam is positioned outboard of the second inner face.

Abstract: A modular mobile robot with a chassis including a power source housed therein. Right and left hand track modules are each removeably coupled to the robot chassis. Each track module includes a side plate, at least one drive wheel rotatable with respect to the side plate, a motor for driving the drive wheel, at least one idler rotatable with respect to the side plate, and a track extending around the drive wheel, the side plate, and the idler. A turret assembly with its own turret drive subsystem is removeably coupled to the robot chassis via a quick release mechanism.

Abstract: In order to achieve a solution which assists a farmer in working land in a way which reduces the risk of soil compaction of the land there is, among others, a method of determining a work trajectory to be followed by an agricultural work vehicle. The method includes accessing a soil carry capacity map of an area of land to be worked by the agricultural work vehicle, receiving load data of the agricultural work vehicle so as to determine the agricultural work vehicle load and determining the work trajectory to be followed by the agricultural work vehicle. The work trajectory is determined by correlating the soil carry capacity map and the load data of the agricultural work vehicle, so as to optimize that the area to be worked with low carry capacity is worked with low agricultural work vehicle load.

Abstract: A tracked vehicle, particularly a piste grooming vehicle, comprising a chassis frame and at least one sprocket for a track is characterized in that the sprocket has limited movement between a working position—in which the sprocket protrudes beyond the chassis frame—and a transit position in which the sprocket is located at least partially, preferably totally, within the width of the chassis frame.

Abstract: A windrower having an adjustable axle to vary a width of steerable caster-mounted rear wheels operably connected by right and left steering cylinders mounted to right and left reaction arms pivoted to respective rods coupled to steering arms fixed to respective spindles mounted within a cylindrical receptacle at outer ends of the adjustable axle. One embodiment each reaction arm has a bracket coupled to a fixed portion of the rear axle when telescopic end sections of the axle are in a narrow width position, and selectively mounted to outer ends of the telescopic end sections of the axle when in a wide width position. A second embodiment has the reaction arms mounted to spindle receptacles at outer ends of the axle sections to provide the reaction arms with an infinite number of angular positions about the spindle receptacles for different tread widths of the steered rear wheels.

Abstract: A modular mobile robot with a chassis including a power source housed therein. Right and left hand track modules are each removeably coupled to the robot chassis. Each track module includes a side plate, at least one drive wheel rotatable with respect to the side plate, a motor for driving the drive wheel, at least one idler rotatable with respect to the side plate, and a track extending around the drive wheel, the side plate, and the idler. A turret assembly with its own turret drive subsystem is removeably coupled to the robot chassis via a quick release mechanism.

Abstract: A mobile lift crane includes a carbody and at least four crawlers attached to the carbody, each crawler having a crawler frame attached to the carbody by a trunnion having an axis. The crawler frame is attached to the carbody so as to be able to pivot with respect to the carbody about the axis of the trunnion. The crane also includes a rotating bed rotatably connected to the carbody such that the rotating bed can swing with respect to the crawlers and a boom pivotally mounted on a front portion of the rotating bed. A linear actuator is connected between the crawler frame and the carbody and extends through the trunnion. The linear actuator is part of a self attachment mechanism. The trunnion includes a tubular member with a longitudinal axis, a first end configured for connection to the crane carbody and a second end configured for connection to the crawler frame. At least one of the ends is configured to allow rotational movement of the crawler frame relative to the carbody about the longitudinal axis.

Abstract: In a crawler vehicle, at the time of crane operation at a place where a grounding space of crawlers is limited, a land leveling preparation is suppressed as little as possible so as to improve efficiency of the operation. The crawler vehicle is provided with left and right crawler frames on the both left and right sides of a track frame. The crawler frames can be moved between an expansion position for maximizing a distance between centers of the crawlers and a contraction position for minimizing the distance. Further, the crawler vehicle can position the crawler frames to the track frame at an intermediate position in the middle of the expansion position and the contraction position.

Abstract: A track driven vehicle has an undercarriage transmission assembly that has a central transmission housing forming a one piece all welded housing. The central transmission housing has upright side wall portions with multiple layers of plates or walls in a sandwich construction on which drive motors are mounted. The drive motors are on the interior of the transmission housing, with track driven sprocket assemblies on the exterior of the side walls. Track mounting pods or frames are welded to the exterior of the side walls of the transmission housing.

Abstract: A remote-controlled dynamoelectric machine inspection vehicle that can fit and travel within a narrow air gap between a stator and rotor of a dynamoelectric machine. The inspection vehicle has an effectuator that can remotely activate a hammer driven by a high pressure pneumatic three-stage miniature piston that propels the hammer against a stator slot wedge creating an impact force that causes the wedge to vibrate. The vibrations are sensed to determine the tightness of the wedge.

Abstract: A pipelayer frame for a track-type machine having an engine compartment, a first track frame, and a second track frame is disclosed. The frame has a center frame removably attachable within the engine compartment, a first side frame removably attachable to the first track frame and to the center frame, and a second side frame removably attachable to the second track frame and to the center frame. The frame also has a spacer assembly removably attachable to the first side frame. The frame further has an adjustable assembly located between the second side frame and the center frame, the adjustable assembly being configured to adjust a distance between the second side frame and the center frame.

Abstract: A conversion kit for converting a pipelayer frame of a first width to a different width is disclosed. The conversion kit has a spacer, removably attachable to a first side of the pipelayer frame, and a first plurality of replacement brackets for removably attaching the first side to a first track frame. The first plurality of replacement brackets have a different length than a first plurality of existing brackets that the first plurality of replacement brackets replace. The kit also has a second plurality of replacement brackets for removably attaching a second side of the pipelayer frame to a second track frame. The second plurality of replacement brackets have a different length than a second plurality of existing brackets that the second plurality of replacement brackets replace.

Abstract: A construction vehicle includes first and second track assemblies. The track assemblies each include an inner portion, and outer portion and a middle portion between the inner portion and the outer portion. An adjustment mechanism is pivotably coupled to the middle portions of the first and second track assemblies. The adjustment mechanism extends and retracts along a width axis to adjust a distance between the first and second track assemblies. The width of the first and second track assemblies can determine an overall width of the construction vehicle.

Abstract: A pontoon crawler track assembly intended to be used as a crawler-track-driven undercarriage in a working machine. The assembly includes a mounting frame and pontoon members. The mounting frame includes a coupler to couple the pontoon crawler track assembly with the working machine and a fastener for attachment of box-structured, hollow pontoon members at the sides of the mounting frame. Each pontoon member includes a crawler track arrangement, which is arranged moveable by way of an internal power transmission arrangement. The breadth of the pontoon crawler track assembly is adjustable. Actuators adjust a breadth of the assembly in a way that a working machine equipped with the pontoon crawler track assembly may be brought, by changing the distance between its pontoon members with the actuators, operating by auxiliary power, first into a narrowed position particularly and on the other hand into a broadened position.

Abstract: A self-propelled wheelchair with independently driven wheels and dual support frames connected in an articulating relationship. A front frame supports a seat and a rearward extended pivot connector. A pair of front wheels and left and right front drive units are connected to the front frame. A rear frame includes a forwardly extended pivot joint, a rear support platform having a power source thereon, and a pair of rear wheels and left and right rear drive units connected thereto. An articulating junction is formed by the front frame pivot connector attached to the rear frame pivot joint and providing articulation between the front frame and rear frame. A manually operable control unit includes computer circuitry in connection with each wheel drive unit, wherein manipulation of the control unit actuates each drive unit for control of rotational speed and direction of rotation for each wheel.

Abstract: A crawler-tracked vehicle with a variable track width can be used as a construction vehicle and/or as a vehicle for agricultural purposes. The vehicle includes an undervehicle with a vehicle frame, on which is provided on each of the two sides a chassis with a chassis carrier respectively for carrying at least one driving wheel and one deflecting wheel and supporting wheels for the guidance of crawler tracks. At least one of the two chassis carriers (10, 11) can be fastened releasably to the vehicle frame (7) at a different distance transversely to the undervehicle (6) with carrying elements (24, 25) arranged laterally at the front and rear and with receiving and supporting elements (26, 27) and with holding and releasing elements (28).

Abstract: The invention relates to a self-propelled robot which is used to handle explosive charges and which is of the type that is remote controlled by means of a control console. The inventive robot can be used to handle explosive devices and charges as well as perform special, dangerous operations. According to the invention, the self-propelled robot (1) comprises movement means which are defined by two lateral caterpillar running gears (2) having adjustable running sides, with an adjustable-length scraper (3) being disposed at the rear thereof. The invention also comprises an articulated arm (4) having a first segment (7) which takes the form of a fork that is actuated by a pair of cylinders (6) and which terminates in a clamp (5).

Abstract: An adjustable ski track width mechanism allows adjusting the ski track between a narrow ski track width and a wide ski track width. The adjustable ski track width mechanism includes a steering mechanism that provides correct steering geometry and corresponding steering characteristics regardless of the narrow ski track width or the wide ski track width. The adjustable ski track width mechanism can be adjusted by the operator or automatically depending on operator preference or terrain conditions.

Abstract: A remote controlled inspection vehicle provides interchangeable modules, permitting the vehicle to be easily configured to perform a wide variety of tasks. The vehicle includes at least one frame module having a pair of drive modules on either side. Each drive module includes a continuous track surrounding a permanent magnet, and is dimensioned and configured to pivot around its longitudinal axis. The frame modules are dimensioned and configured to be hingedly secured to other frame modules, end effectors including various sensors for performing inspections, and tail units to assist in placing the vehicle in the desired environment.

Abstract: The invention relates to a crawler running gear, particularly for a construction machine. A mid-section and two crawler supports with in each case a crawler chain are provided. The crawler supports are located along a longitudinal direction on both longitudinal sides of the mid-section and in each case detachably fixed to at least two crossbeams. The crossbeams are displaceably mounted in a transverse direction on the mid-section. For simplifying installation, the crossbeams have on their end directed towards the crawler support an at least zonally conically tapering mounting journal and on the crawler supports are provided mounting holes, which are constructed so as to correspond to the mounting journals of the crossbeams.

Abstract: A remote-controlled vehicle and method for performing a plurality of tasks in a location generally inaccessible to humans are provided. The vehicle may include a propulsion frame, and a platform attached to the frame or integral therewith for supporting an interchangeable accessory selected from a set of distinct interchangeable accessories. Each distinct interchangeable accessory may be configured to perform a distinct operational task. The platform includes at least one mechanical power takeoff, and each accessory includes at least one mechanical power receptor configured to interface with the mechanical power takeoff for coupling mechanical energy to the accessory. The platform constitutes a universal platform for the set of distinct interchangeable accessories.

Abstract: A crawler running gear, particularly for a construction machine, having a central section and two crawler supports with in each case one crawler track. The crawler supports are arranged along a longitudinal direction on both longitudinal sides of the central section and are fixed to cross members, which are in each case displaceably mounted in a displacement direction on the central section by means of at least one guide. For the purpose of a stable connection at least one clamping element is provided with which a cross member can be braced at right angles to the displacement direction relative to its guide.

Abstract: A remote controlled inspection vehicle provides interchangeable modules, permitting the vehicle to be easily configured to perform a wide variety of tasks. The vehicle includes at least one frame module having a pair of drive modules on either side. Each drive module includes a continuous track surrounding a permanent magnet, and is dimensioned and configured to pivot around its longitudinal axis. The frame modules are dimensioned and configured to be hingedly secured to other frame modules, end effectors including various sensors for performing inspections, and tail units to assist in placing the vehicle in the desired environment.

Abstract: A front lifting equipment for an agricultural crawler tractor with considerable offset (D) of the front art relatively to an intermediate girder (1) whereto are fixed the track-layer assemblies (Cg), an axle (4) being provided at the rear. The equipment includes a reinforcing member arranged on each side of the tractor, fixed to the intermediate girder and to the rear axle, and formed by a flank (18g) substantially parallel to the tractor median vertical plane, and whereof the height is arranged to ensure satisfactory mechanical resistance in spite of a reduced thickness such that adjusting the narrow gauge track of the tractor is not hindered. A link (L) between the front part (19g) of the reinforcing flank and a fixing point located towards the tractor front is provided for picking up effort.

Abstract: A crawler or tracked vehicle has a running gear with separately operable tracks, and a vehicle body pivotably connected to the running gear about a substantially horizontal pivot axis that allows the running gear to pivot relative to the vehicle body. The two tracks can pivot independently of each other and independently of the vehicle body. At least one spring arrangement preferably including a spring and a shock absorber is arranged on each side of the body, and is respectively connected between the running gear and the vehicle body. The spring may be vertically or horizontally oriented.

Abstract: A system for adjusting the width of a tracked vehicle is described including a rear suspension having a differential that drives two spur gears with rotational axes located above the differential and adapted to slidingly support two drive axles.

Abstract: A tracked suspension for a tractor or other work vehicle is disclosed having an endless belt, a belt tensioner, a drive wheel, and a plurality of idler wheels mounted to a suspension frame or idler carriage, the assembly being arranged such that the belt tension provided by the tensioner is absorbed within the frame and is not transmitted to the axle extending from the tractor that drives the tracked suspension. The tracked suspension can be adjusted by loosening or removing mounting bolts that fix the suspension to beams extending from the vehicle, sliding the suspension toward or away from the vehicle, and tightening the bolts. By absorbing the belt tensioning forces within the tracked suspension itself, rather than transmitting the belt tensioning forces to the axle, the suspension can be more easily adjusted without requiring the removal and replacement of the drive axle.

Abstract: A tracked suspension for a tractor or other work vehicle is disclosed having an endless belt, a belt tensioner, a drive wheel, and a plurality of idler wheels mounted to a suspension frame or idler carriage, the assembly being arranged such that the belt tension provided by the tensioner is absorbed within the frame and is not transmitted to the axle extending from the tractor that drives the tracked suspension. The tracked suspension can be adjusted by loosening or removing mounting bolts that fix the suspension to beams extending from the vehicle, sliding the suspension toward or away from the vehicle, and tightening the bolts. By absorbing the belt tensioning forces within the tracked suspension itself, rather than transmitting the belt tensioning forces to the axle, the suspension can be more easily adjusted without requiring the removal and replacement of the drive axle.

Abstract: Existing track laying work machines fail to provide adequate suspension for reducing shock loads transmitted to machine components and the operator. The present suspension system provides suspension members interposed the main frame of the work machine and an elongated beam supported by first and second track roller frames. Cushioning members separate the roller frame from the elongated beam and drive wheel hub, to provide further isolation from shock and torsional movement of the roller frame.

Abstract: A track suspension is disclosed including a track, a drive wheel engaged with the track, a wheel support, a drive wheel shaft rotationally engaged with the wheel and a drive wheel shaft support. The wheel support is adjustably securable to the drive wheel shaft support in a plurality of laterally disposed positions and the wheel is slidingly positionable with respect to the length of the drive wheel shaft in correspondence with the adjusted position of the wheel support. Also disclosed is a tracked vehicle including a frame, at least one track suspension including a track, a drive wheel engaged with the track, a wheel support, a drive wheel shaft and a drive wheel shaft support. The wheel support is adjustably securable to the drive wheel shaft support in a plurality of laterally disposed positions and the wheel is slidingly positionable with respect to the length of the drive wheel shaft in correspondence with the adjusted position of the wheel support.