24Bogie parts with description Wheel Slide Protection System Lead to Axlebox. Where a Wheel Slide Protection (WSP) system is fitted, axleboxes are fitted with speed sensors. These are connected by means of a cable attached to the WSP box cover on the axle end.Motor Suspension Tube. Many motors are suspended between the transom and the axle. This motor is called "nose suspended" because it is hung between the suspension tube and a single mounting on the bogie transom called the nose.Brake disc. Each wheel is provided with a brake disc on each side and a brake pad actuated by the brake cylinder. Some bogies have two brake cylinders per wheel for heavy duty braking requirements.Bogie Transom. Transverse structural member of bogie frame (usually two off) which also supports the car body guidance parts and the traction motors.Bogie Frame. Steel plate or cast steel. Here is a modern design of welded steel box format where the structure is formed into hollow sections of the required shape.Shock Absorber. To reduce the effects of vibration occurring as a result of the wheel/rail interface.Brake Cylinder. When air is admitted into them, the internal piston moves links attached to the piston and causes the brake pads to press against the discs.Primary Suspension Coil. A steel coil spring, two of which are fitted to each axle box in this design. They carry the weight of the bogie frame and anything attached to it.Motor. Normally, each axle has its own motor. It drives the axle through the gearbox. Some designs, particularly on tramcars, use a motor to drive two axlesLifting Lug. Allows the bogie to be lifted by a crane without the need to tie chains or ropes around the frame.Secondary Suspension Air Bag. Rubber air suspension bags are the secondary suspension system. The air is supplied from the train's compressed air system.Gearbox. This contains the pinion and gearwheel which connects the drive from the armature to the axle.
41Bogie with steel primary and air bag secundary sospension The weight of the car body (well, half of it, since the other half is carried by the other bogie) rests on the air bag, which is mounted on the top of the bogie frame.Compressed air is fed into the air bag through a levelling valve attached to the underside of the car body. The valve is operated by a lever attached to one end of a link, whose other end is fixed to the bogie frame. Any vertical movement between the car body and the bogie is detected by the lever which adjusts the levelling valve accordingly.When the load on the car is changed at a station by passengers boarding and alighting, the weight of the body changes and the levelling valve adjusts the air pressure in the air bags to match.The effect is that the car body maintains almost a constant height from rail level, regardless of load. I say almost a constant height because the primary springs will depress to some degree with the additional load. If the car load is reduced, the levelling valve will allow excess air pressure to escape.This can sometimes be heard as an intermittent gentle hissing from under the cars at a terminus as all the passengers alights from a modern EMU.
42Air bag secundary sospension In this transverse view of a car with air suspension, the two air bags provided on a bogie can be seen.Inside each is a solid rubber suspension pack sufficiently strong to carry the suspension load, retained in case the air bag should burst or the air supply is lost.One other feature of air suspension systems is that they can only alter the air bag pressure when the train is stationary. Constant changes of vehicle height would cause excessive bouncing if the system operated while the train was running.The levelling valve is automatically locked out of use when the train is moving or when the doors are closed - depending on design.This type of arrangement often uses a bolsterless truck or bogie, as shown is the diagrams above. It is a very simple design where the bogie frame is fabricated, usually in welded box-sections, into the form of the letter H. The crossbar of the H is where the bolster would be.It is called the transom. Instead of beingsuspended on springs it is solid with the side pieces. The car body (secondary) suspension is through the air bags mounted on the ends of the "crossbar" of the H.This type of bogie is now popular on passenger rolling stock.
44Conventional and steering truck On very sharp curves, the wheel flanges (bordini) contact the rails at an angle, an not only do they wear each other but they also produce a lot of unpleasant noise and vibration.Conventional and steering truckFlexible in longitudinal directionIf the axles are allowed some freedom this wear and noise is reduced, but safety at speed is also reduced.Less wear on flanges and rails occurs at the expense of a more complicated suspension system, with more joints in the bogie mechanism
50Advantages based on experience State-of-the-art radial self-steering bogies are able to steer approx radially in curves of R= m.However, on many networks such curves are decisive for the accumulated wheel and rail wear.This is proved in practical trains services to reduce lateral forces, to heavily reduce wheel and rail wear and to increase lateral curving acceleration.With appropriate damping (especially hydraulic yaw damping) running stability is assured at various values of eq. conicity. At the highest speeds (250 km/h + 10 %) conicity should be limited to 0.3 à 0.4(UIC 518 requires 0.3).Testing and experience confirm theory and simulations.
51LimitationsHigh tractive forces may limit the radial steering capability, because radial self-steering is depending on a certain amount of friction (creep) forces. In high-adhesion locomotives radial self steering can not always be managed.In local/regional trains with adhesion utilization of % the radial performance will be appropriate in practice, because high adhesion is only applied occasionally at acceleration at low speed.
52Future outlookMarginal cost for track deterioration should be included in the track access charges on a number of European railway networks. This sharpens the need for ”track-friendly” bogies.Ongoing development seems to widen the application of self-steering bogies to higher speed (250 km/h and up). Many high-speed trains will be running on various track standards at various speeds, in particular tilting trains.Actively controlled radial steering–”Mechatronic bogies”-may be considered as an appropriate mean to achieve still higher performance and track-friendliness. Once active control is robust, fail-safe and affordable, such solutions may be very attractive.
54Prestazioni dei freni ad attrito Il freno è composto da un elemento mobile (tamburo o disco) calettato rigidamente alla ruota (o al cerchione o all’asse porta ruota) e da un elemento fisso solidale al telaio del veicolo.L’applicazione della forza normale P1 alla superficie di contatto fra i due elementi provoca il sorgere di una forza di attrito tangenziale Ft fra di loro.