Abstract: In one aspect, a track structure usable by a wheeled vehicle for hauling a payload up an inclined enclosed passageway comprises a hollow rigid center rail member configured to act as both a center rail for the wheeled vehicle and as a ventilation duct. Opposite lateral faces of the hollow center rail member have respective wheel contact surfaces grippable by an opposed pair of inwardly-biased drive wheels of the wheeled vehicle. Rail support structure depends from the hollow center rail member. An elevated pair of rails is attached to the rail support structure, the rails being on opposite sides of and substantially parallel to the hollow center rail member. Each rail is supported by the rail support structure so as to provide an upper, lower, and lateral surface suitable for rolling engagement by a weight-bearing wheel, undermount wheel, and guide wheel, respectively, of the wheeled vehicle.

Abstract: An assembly that may be used in a transportation system is disclosed that in one or more embodiments includes at least one or more of the following: a braking system, which at least partially functions with an air bearing, a linear induction motor (‘LIM’) that has tilting abilities, and an inflated air bearing that is positioned with respect to a rail such that a portion of the rail is inside the air bearing. Regarding the latter, in one or more embodiments the inflated air bearing has a semi-enclosed cavity shape and the rail is cross-sectionally curved such that a portion of the cross-sectionally curved is positioned partially inside the semi-enclosed cavity. In one or more embodiments, the assembly is included as part of a monorail system.

Abstract: A propulsion system is composed of vehicles with four wheels having one of the axles connected to a pylon attached to the propulsion plate. The vehicles move over rails of elevated guideways supported by pillars. The top of the elevated guideways has longitudinal slots for allowing passage of pylons of propulsion plates. The elevated guideway is dual and has two power propulsion units for propulsion operation in a push and/or pull mode, one for each elevated guideway. The power propulsion units are installed inside the machine rooms under the pavement of the sob passenger stations supported on pillars. The power propulsion units are connected to the elevated guideways by means of connection ducts. Secondary propulsion ducts are disposed in parallel with the propulsion duct and integrated with its respective flow direction valve which allows that the air flow generated by the power propulsion unit is discharged in the propulsion duct in two distinct positions.

Abstract: A system, apparatus, and method for constructing or providing a ride surface for an amusement attraction, such as an inflatable surfing attraction. The ride surface may be formed via the connection of a plurality of ride surface portions or segments. The ride surface may be connected via fastening elements that are disposed at an elevation different from that of the top or other surface that is to be used by riders during operation. Cut-outs and/or extrusions within one or more of the ride surface portions or segments may aid in preventing disruptive forces from fluid or water during operation from acting to separate the ride surface portions of segments making up the ride surface. Additional fastening mechanisms may be employed in addition to such fastening elements to further aid in increasing durability.

Abstract: Method for controlling a dynamic linear motor. Method includes defining a path over which a rotor is to travel, placing stator segments at least along portions of the path where the rotor may be one of accelerated and decelerated and supplying a variable amplitude and frequency of voltage to power the stator segments in a synchronized manner so that, as the rotor approaches stator segments, the stator segments are powered and, as the rotor departs stator segments, the stator segments are depowered.

Abstract: The present invention relates to a fender, bogie, train, track and methods. The fender according to the invention comprises: a support surface provided on the underside during use; an inner pressure chamber provided in or on the support surface; a feed arranged in the pressure chamber for feeding a fluid; a first rim present round the inner pressure chamber, wherein at least a part of the rim is flexible; and a second rim arranged round the first rim such that a pressure chamber is created between two adjacent rims.

Abstract: A transportation system is disclosed that includes a monorail (or other vehicle) along a column-supported rail wherein a linear induction motor's (‘LIM’) connection to an assembly, to which the monorail/vehicle is attached, enables the LIM to essentially assist an air bearing, positioned between the rail and assembly, such that less air pressure is required. In some embodiments, a control system assists in adjusting the air pressure supplied—e.g., based on LIM data and/or weight (of vehicle and/or cargo). Further disclosed is a compliant air bearing that minimizes air loss during vertical and lateral curves, including embodiments where the air bearing is positioned relative to the rail such that a plenum area is smaller than a semi-enclosed cavity area. Additionally disclosed is a brake system that includes a brake pad attached to the air bearing that is engageable without the need to adjust the air bearing's air pressure.

Abstract: A structure having at least one flexible material structured and arranged to withstand a tensile load, at least one support structure configured to support the flexible material and structured and arranged to withstand a compressive load, and at least one enclosed volume at least partially defined by the at least one flexible material, the at least one enclosed volume being configured to be maintained as a low-pressure environment.

Abstract: A cargo management system is provided comprising an air cushion cargo shuttle, an air blower configured to blow air beneath the air cushion cargo shuttle, and an inductive charging receiver on the cargo shuttle. In various embodiments, an energy storage module may be electrically coupled to the inductive charging receiver. A wireless charging station may inductively couple with the inductive charging receiver. The inductive charging receiver may include a first resonant coil, and the wireless charging station may include a second resonant coil. The wireless charging station may switch on in response to the air cushion cargo shuttle entering a desired range. A floor panel may rest beneath the air cushion cargo shuttle with the wireless charging station beneath the floor panel. The floor panel may comprise at least one of a composite material or a metallic material.

Abstract: A high-speed transportation system, the system including at least one transportation tube having at least one track, at least one capsule configured for travel through the at least one tube between stations, a propulsion system for the at least one capsule; and a levitation system for levitating the capsule in the tube.

Abstract: The invention relates to compositions and methods for inducing a protective immune response against a poxvirus in a human neonate or infant of less than 6 months of age. The invention encompasses administering a single high dose of an MVA to a human neonate or infant of less than 6 months of age, wherein the administration induces protective T- and B-cell responses against a poxvirus in the human neonate or infant.

Abstract: A transportation system is disclosed that includes a monorail (or other vehicle) along a column-supported rail and a movable weight system that repositions and/or accelerates a movable weight with respect to the movable weight's rail to counterbalance a moment associated with the weight and/or a centrifugal force of the monorail relative to the column, where some embodiments also mitigate resonance. Also disclosed is a linear induction motor (LIM) system that enables the LIM to tilt and thereby remain close to the rail, which mitigates potential thrust losses and/or air losses. Further disclosed is an air bearing system where the air bearing has a compliance and a resilience that minimizes air loss between the rail and the bearing. Additionally disclosed is a rotatable wedge system that essentially expands and/or contracts automatically to maintain an adjacency between two rail portions, where some embodiments also mitigate resonance.

Abstract: A dynamic linear motor is controlled by determining a relative proximity of a moving rotor of the linear motor to a fixed stator segment of the linear motor using a current location of the moving rotor. A current driving characteristic of the linear motor at the current location of the moving rotor is determined. Settings for the fixed stator segment when the moving rotor reaches the fixed stator segment are identified based on the current driving characteristic. The fixed stator segment is driven based on the settings when the moving rotor reaches the fixed stator segment.

Abstract: The present disclosure includes cargo loading systems and components including cargo systems utilizing one or more air cushions to elevate one or more cargo shuttles. Air is delivered to the air cushions by compact centrifugal air blowers. Such compact centrifugal air blowers are designed to provide sufficient power to inflate air cushions, while having a sufficiently short profile.

Abstract: The present disclosure includes cargo loading systems and components including cargo systems utilizing one or more air cushions to elevate one or more cargo shuttles. The air cushions are formed by one or more air curtains, which include pressure compensating seals. The seals allow the air curtains to contact and seal against a floor panel, reducing leakage from the air cushion.

Abstract: An air cushion cargo shuttle for loading and unloading cargo on an airplane is described. The air cushion cargo shuttle includes a first inner air curtain defining a first volume of pressurized air. The air cushion cargo shuttle also includes a noise barrier curtain enclosing the first inner air curtain. The noise barrier curtain is adapted to trap air leaking from the first inner air curtain.

Abstract: A cargo management system is provided including an air cushion cargo shuttle, an air blower configured to blow air beneath the air cushion cargo shuttle, and a first wireless communication device on the air cushion cargo shuttle. A cargo shuttle may also include a wireless communication device on the cargo shuttle, and a power drive unit on the cargo shuttle.

Abstract: Among the problems in achieving high yields of sown crops in agricultural production are the timely sowing thereof, maintaining moisture in the soil and environmental friendliness. In the disclosed method for increasing crop yields, including in naturally handicapped areas, the method optimizes sowing times, carrying out the sowing in wet soil which is in a saturated and/or muddy state, during or immediately following rain or directly following the thawing of a snow cover. A sowing assembly travels at a rate of between 1 and 60 km/hour, and the load-bearing portion for the sowing assembly is a utility vehicle operating with a pressure on the soil of 0.4 kgf/cm2 or lower, and as low as zero, e.g., a “Bars UTES 271” having elastic tire-covers or an air cushion. The seeds are buried directly under the layer of over-wet soil and the burial depth is between 0.2 and 15 cm.

Abstract: A system with at least one sliding surface element (1), preferably as run-in track systems for ski jump system/ski jumps, wherein the height and/or the course of the sliding surface elements (14) has to be adjusted to any profile by spacer elements (30).

Abstract: A capsule for an evacuated tube transport system, the capsule comprising a capsule body for carrying passengers within an evacuated tube; a first door disposed in a first end of the body; and a first coupling mechanism and a first sealing mechanism arranged respectively to couple the capsule to another capsule at the end of the body while the capsules are moving and to establish a seal around the door and a corresponding door in the other capsule to enable passengers to move from one capsule to another through the doors without exposing the passengers to the pressure of the evacuated tube.

Abstract: A transportation apparatus configured to travel on rails and having an induced freezing rail system includes: a transportation vehicle having a support unit configured to support a frame from the rails; and a freezing rail system comprising freezing rails positioned on a ground surface corresponding to the support unit of the transportation vehicle, the freezing rails having a refrigerant and cooling devices.

Abstract: The present disclosure is directed to a system, method and apparatus for imparting a traversing motion and a rotation motion to a decoy. The system includes a first track portion, a second track portion securable to the first track portion and a sled for traversing along the tracks. A decoy is mounted on a pole rotatably secured to the sled. Two cables that are manually retractable by winding apparatus are each connected to a laterally extending arm of the pole so that the decoy is rotated to face the direction of traversal along the track. Retracting the first cable rotates the decoy in a first direction and to moves the sled in a first direction along the track section. Retracting the second cable rotates the decoy in an opposing direction and to moves the sled in the opposing direction along the track.

Abstract: The present invention has been developed to improve the way a payload support platform, such as a mole, is driven between one site and another, particularly when the second site is the interior of a Lift which interfaces with a Pallet Handling System (PHS) of a ship. In a first aspect the invention proposes that the driving means which drives the payload support platform along a rail (10) is also used to move that rail (10) relative to the payload support platform and a support rail (22) so that the position of the rail can be changed during the movement of the payload support platform between one site and another. The payload support platform is lockable to the support rail (22), such that the force which drives the payload support platform along the rail (10) changes to driving the rail (10) relative to the support rail (22).

Abstract: A vehicle track including a soft porous material and a vehicle which rides on the track by skiing cm the soft porous material. The vehicle has a large ski surface that rides on the soft porous material, supporting the weight of the vehicle at high speeds. Air within the soft porous material supplies most of the lift needed to support the train, Qniy a small amount of the support is provided by the structure of the porous material itself when the vehicle is in motion. As a result, the friction between the soft porous material and the ski surface may also be exceedingly small. To increase the amount of lift provided by the soft porous material it can be contained within a channel having impermeable sides and bottom. If the ski surface is substantially the same width as the channel, the impermeable sides prevent the air from escaping on either side of die ski surface. Accordingly, the trapped air contributes to greatly enhanced lift force.

Abstract: An electrically powered vehicle transportation system utilizes a guideway with parallel enclosed rails. Each enclosed rail has an electrical bus bar for supplying power to vehicles on the guideway. The guideway will accommodate dual-mode vehicles that are capable of usage on conventional streets as well as on the guideway. The guideway also accommodates conventional vehicles and ferries that operate only on the guideway. The dual-mode vehicle has a body with axles that are extensible. The axles move from a retracted position, with the wheels recessed within the wheel wells, to an extended position. In the extended position, the wheels locate within the enclosed rails. Conventional vehicles and freight are carried on ferries that move along the guideways.

Abstract: An electrically powered vehicle transportation system utilizes a guideway with parallel enclosed rails. Each enclosed rail has an electrical bus bar for supplying power to vehicles on the guideway. The guideway will accommodate dual-mode vehicles that are capable of usage on conventional streets as well as on the guideway. The guideway also accommodates conventional vehicles and ferries that operate only on the guideway. The dual-mode vehicle has a body with axles that are extensible. The axles move from a retracted position, with the wheels recessed within the wheel wells, to an extended position. In the extended position, the wheels locate within the enclosed rails. Conventional vehicles and freight are carried on ferries that move along the guideways.

Abstract: A container for sliding on structural track elements forming part of a system for the conveyance of flat objects comprises:

Abstract: This invention concerns a processing machine, particularly for panel-shaped workpieces of wood or wood materials, which consists of: one or more processing stations which essentially lie in the same plane; at least one working unit which can travel over the work stations in three axes perpendicular to one another, and, a number of bearing rails upon which the displaceable carriage units are arranged in the plane of the work stations. The bearing rails have electrical and pneumatic supply interfaces for the carriage units and the supply interfaces are arranged linearly along the longitudinal direction of the bearing rail.

Abstract: A support for aiding a person, robot or material-moving member in a gravity free environment. The support comprises a platform having slots therein with releasable securing means disposed on either side thereof which cooperate with a wheeled member disposed in the slot having a shoe connected thereto with cooperating means engaging the releasable securing means to permit the person, robot or the like wearing the shoes to traverse the support in a safe, regulated manner.

Abstract: A guide system for a reciprocating grate system having a grate surface, alternating rows of stationary and movable grate blocks, a movable carriage, a fixed undergrate structure, and a driving force device. The guide system includes guide units which guide the movable carriage and the movable rows of grate blocks with respect to the fixed undergrate structure and the stationary rows of grate blocks during reciprocating stroke cycles of the driving force device. Each guide unit includes a fixed guide member and a movable guide member. The fixed guide member is attached to the fixed undergrate structure and has an upper non-linear contour with wear plates, each having a wear surface. Each movable guide member is attached to the movable carriage and has a lower non-linear contour with wear plates, each having a wear surface. When the movable carriage is in an installed position, the wear surfaces are in slidable contact with each other.

Abstract: A new carriage system for a ram feeder has been designed and is provided. As in the prior art, the carriage system has a drive cart to which is attached a driving force member at one end thereof and a ram member on the other and opposing end thereof. The drive cart is supported by and travels upon a carriage table. The carriage system of the present invention replaces the prior art wheel and flat rail arrangement under the drive cart. The wheels together with the associated problems have been eliminated. In the present invention, the carriage system has a guide member attached to the carriage table and a travel member attached to the underside of the drive cart. The guide member is longitudinally oriented on the carriage table in the direction of drive cart travel and has at least one upper wear portion. The guide member guides the drive cart and the attached ram member during a reciprocating stoke cycle of the driving force member. The travel member has at least one lower wear portion.

Abstract: A linear motion rolling contact guide unit includes a rail elongated in shape, a slider slidably mounted on the rail and a plurality of rolling members interposed between the rail and the slider. The rail has a top surface, a pair of side surfaces and a bottom surface, and a guide groove is formed in each of the side surfaces with a tapered relief trench formed at the bottom of the guide groove. A side recess is also formed in each of the side surfaces. The slider is provided with an end seal having a first seal lip at each of front and rear ends and also with a bottom seal having a second seal lip. The first seal lip is in sliding contact with the top surface and also with the guide groove and the tapered relief trench and the second seal lip is in sliding contact with the side recess of the rail.

Abstract: A pulling system for pulling or moving a large object, such as pulling components of an offshore oil/gas production platform onto an adjacent barge that is subsequently transported to the installation site. This pulling system incorporates a single elongated rod that is connected between the object to be moved and a puller unit that pulls the object along a track. During operation, the puller unit causes a gripping unit to grip the rod so that the puller unit can move the object. Afterwards, the gripping unit releases its engagement of the rod, repositions itself with respect to the rod, and regrips the rod so that movement of the object may again be initiated by the puller unit.

Abstract: A sleighroad is disclosed including a wheelless transportation system with a locomotive including motorized horsehoofing thrusters for propelling a plurality of carriages equipped with ball thrust bearings for running on steel rails instead of using conventional carriage wheels and wherein the carriages include side-mounted roller thrust bearings operatively connected to side guard railings to keep the carriages on track.

Abstract: An apparatus for a handling assembly comprises at least one carrier member and at least one slide unit displaceably arranged on the carrier member. The slide unit is in operative connection via a cable drag member electrically/pneumatically or electrically/hydraulically with an energy and a signal source. The carrier member is a one-piece cellular structure and has an integrated guideway which, has an inclined position within the carrier member, so that a space-saving arrangement of the cable drag member, substantially protected against external action, is obtained. The slide unit comprises a driving unit, which is arranged in a U-shaped head guided with the lateral legs on the carrier member and is operatively connected with a rack arranged on the carrier member, for linear movement. Protective members are provided laterally on the carrier member. The slide unit together with the carrier member forms a closed system protected against external action or intervention.

Abstract: An amusement ride down a ramp containing two air suspension flumes and a return conveyor belt system. The ramp is in a climate controlled transparent housing. There is ducting in the ramp for air conditioning, compressed air, and other possible fluid needs along the ramp and at its top portion. The upper half of the housing may be transparent. The cars have a transparent canopy and enclose room enough for three passengers. The ramp has modular sections supported by stanchions the height of which are hydraulically adjustable by automatic sensing devices; possibly using laser light or other types of electrical sensing apparatuses.

Abstract: A device in the storage system having movable units placed one beside the other and provided with shelves, the units being movable sidewise on tracks in order to form a passage between two units movable in opposite directions, the passage allowing access to the units, and a handling device movable into said passage for loading or unloading of articles into and out of the units. The tracks carrying the movable units are composed of interspaced sections placed on the floor which are provided with upwardedly directed support wheels or rollers, and that in the interspaces uninterrupted rails extend therein upon which said handling devices are movable.

Abstract: A transportation system is disclosed in which passenger carrying coaches are guided along paths defined by a trackway. The trackway has bottom, top and side tracks which limit movement of the coaches orthogonally to the trackway. The coaches proceed, for the most part, without touching the tracks, being supported by stub wings, mounted on pylons carried by the coaches. Motive power is supplied by a jet engine and primary control of a coach is by airfoil type control surfaces. Auxiliary control is supplied by nozzles which expel pressurized gas to provide corrective reactive forces. The position of a coach along the trackway is derived from location sensors carried by the coach, while the spacing of the coach from the trackway is derived from proximity sensors. The sensor signals are fed to central processing unit which compares this information with benchmark information contained in memory. The location information is used to command the motive power jet and flaps on the stub wings.

Abstract: An industrial robot has a head movable in first and second orthogonal directions within a working area to manipulate a workpiece. The industrial robot comprises a stationary base extending along the first direction, an intermediary base slidably disposed on the stationary base to move along the first direction, and a slider slidably disposed on the intermediary base and to move along the second direction. The slider has a supporting portion which extends towards the working area and which supports the head thereon so that the supporting portion positions the head within the working area remotely from the stationary base and the intermediary base.

Abstract: A semiconductor substrate transport system includes a semiconductor substrate holder for holding semiconductor substrates to be transported, a linear pulse motor for driving and reciprocating the semiconductor substrate holder, a pulse oscillator connected to the linear pulse motor, an arrangement for holding a clearance of the linear pulse motor, and guide for guiding the reciprocating motion of the linear pulse motor. The semiconductor substrate holder, the linear pulse motor, the clearance holding arrangement and the guide are installed in a chamber which is brought into a vacuum atmosphere, whereby the appearance of dust during the transport of the semiconductor substrates can be suppressed, and the available percentage and throughput of the semiconductor substrates processed or to be processed by a semiconductor production apparatus can be enhanced.

Abstract: An air assisted sliding device has a pallet supported on a base. The pallet has a recess provided on the periphery of its bottom surface in which a flexible tubular sealing member is mounted. The sealing member has a memory normally contracting it so as to be flat. An air passage communicates with the interior of the flexible sealing member so that compressed air can be fed to it. A groove is evenly provided on the bottom surface of the pallet within the bounds of the recess and a separate air passage for feeding compressed air or vacuum air is communicated with the groove so that the pallet may be provided with an air film of compressed air or may be stopped and a vacuum applied to attract the pallet to the base at a predetermined position on the base. A timing belt drive or an electromagnetic motor is used.

Abstract: Improvements to the various components of hydrostatic bearing levitation systems, systems wherein fluid pressure between a load and the rails of a track system supports and guides the load, are described. The rail has a plurality of lengthwise extending ports and nozzles communicating from the innermost ports through the curved upper wall to the interface area between the rail and the load. The nozzles are arranged in longitudinally aligned groups and in a pair of parallel rows with the groups of one row being longitudinally staggered with respect to the groups of the other row. The nozzles can be inexpensively produced by boring an oversize hole through the upper wall and fixing a cannula, such as a hypodermic needle, in the bore. The cannula's internal diameter is the desired nozzle diameter. The load support member has a compliant outer cover, a central core, and a filler material wound tightly on the core.

Abstract: This invention is a combination consisting of a mechanism for supporting varying loads by use of compressed air in motion and transported by a set of traction wheels acting equal and opposite to the compressed air force while transporting the load. The unique features of this invention incorporate the capability of transporting varying loads at various speeds with a considerable reduction of horsepower requirements. In accomplishing this transportation of loads there is created an Air Motive Clamp upon the guiding support member (track or beam) which instantaneously and continuously guides the transported loads automatically by a closed loop servo system thereby simplifying operational control, reducing the external supporting weights required and provides substantial economic savings including:(1) Due to the compressed air support of loads there is a substantial reduction in friction as compared with present day bearing load support.

Abstract: A pleasure vehicle which is to be used on a trough-shaped downhill track, includes a vehicle body and a leg support, extending frontwardly therefrom. A plurality of support elements support the vehicle on the downhill track for movement down the track. A plurality of brake shoes are mounted on the vehicle body, for simultaneous displacement by a single actuating lever into and out of braking positions, so that the support elements of the vehicle body are lifted off the downhill track, while the support elements of the leg support continue to guide the vehicle on the downhill track.

Abstract: A sledding system having a track installed on a ski slope in the summer has U-shaped track sections with a flat bottom and substantially upright sides which serve to retain a driver controlled sled sliding on the track. Braking is provided by extendable side brakes which engage the upright sides.

Abstract: An electrically powered vehicle achieves maximum structural strength with minimum weight by utilizing a combined body and chassis formed entirely of plastic material, molded and bonded into an integral composite structure which includes a central, hollow longitudinal beam, top, bottom, and side panels of the vehicle body portion, and a power unit supporting chamber at the forward end closing the forward end of the beam and tying it to the side panels. The beam holds the batteries, and the chamber contains all of the components of the power unit including the controlling device. The structure is thus as rigid and light as possible, in addition to eliminating any possibility of any unwanted grounding or electrical paths. The only metal in the vehicle is that of the additional components such as road wheels, suspension members, steering, and power unit and the fasteners and brackets used to retain them in mounted position.

Abstract: A slide and sled combination designed for use on the side of a mountain in conjunction with the operation of ski lift, consists of a monorail extending the length of a mountain from the upper end near the top of a ski lift along a path containing curves, banked curves, and straight segments to the bottom of the mountain near the base of the ski lift. The monorail consists of, in cross-section, a tubular segment supported on a web. Sleds comprising shells are supported on and secured to the monorail by two sets of four wheels which engage the tubular segment. Each set of wheels are supported on bulkheads connected to the shell. A braking system controllable by an operator sitting in the shell includes brakes actuated by a lever that are adapted to engage the tubular segment at diametrically opposite points. Stabilizing wheels are provided on at least one of the bulkheads and are adapted to engage the web.

Abstract: A fluid propelled ground effect vehicle lifted by pressurized fluid directed upwardly through openings in a support floor. The vehicle body is propelled across the support floor by exiting pressurized fluid trapped in a receiving chamber underneath the vehicle body and discharged through an outlet in the chamber. The vehicle body is steered by controlling the direction of exit of the pressurized fluid as it leaves the receiving chamber.

Abstract: The body of a magnetically levitated vehicle is carried by a support structure wherein chassis components support the body through first springs and wherein the magnets are secured to the chassis components by second springs. Each of the first and second springs comprise respective bellows filled with fluid. The pressure or volume of the fluid in the second spring bellows is adjustable in response to the fluid pressure or volume in the first spring bellows. For this purpose the second spring bellows communicate operatively with the respective adjacent first spring bellows, preferably through adjustable valves.

Abstract: An artificial cross-country skiing practice set comprises a track formed of interfitted rail sections placed end-to-end to form parallel rolling bands receiving roller-ski members in normal skiing relationship. At least one roller of each ski member has an adjustable brake simulating resistance to advancement as when skiing on snow.