Realizing the lack of a modern narrow-gauge bogie INVENT Engineering Office Ltd. tendered and won a tender, with the tender no. GINOP-2.1.7-15-2016-00424 to design, develop and to produce the prototype of a narrow-gauge motorized bogie.
What could be the criteria to a modern (universal) narrow-gauge bogie?
- The main criteria for a bogie is its “off-road skill”, to be able to adapt to railway tracks with bad condition. It has to guarantee the proper safety of running whether it is a good or a bad conditioned railway track.
- Another criteria, that connects to the previous one is the design to avoid further damage of the railway track, the two-staged spring assembly.
- Low mass, and within the minimum unsprung mass.
- Low maintenance requirement.
- High passenger comfort even in bad railway tracks.
- Environmentally friendly design, low sound pollution, closed lubricant spaces with improved sealing.
- Make sure that the most parts of the motorized bogie can be used for a running bogie. (universal)
Main dimensions and parts of the Universal Motorised Bogie
- Gauge: 760 mm
- Wheel diameter: 600 mm
- Wheel-base (Axle distance): 1700 mm
- Axle-load: 5-6 t
- Nominal speed: 20-60 km/h
The bogie frame is a “H” shaped box-girder consists of welded steel sheets creating the rigid frame of the bogie. The axle bearing houses, the primary and the secondary springs, the side-bearers, the draw-gear and the brake set connects to the bogie frame. Thus the bogie frame conveys the longitudinal-, the horizontal- and perpendicular forces between the wheel-set and the body-frame.
The wheel-set is produced in a traditional way. It is a press-fitted separate tyre. The axle is guided with spherical roller bearings, which can withstand the dynamic effects of the bad conditioned railway tracks. They have long service life and they does not need frequent maintenance. The bearing houses connect to the bogie frame via silent blocks. This design ensures the good “off-road skill” that means the wheel will not lose the contact with the track even when there is a major defect in the track. Thus the design improves the safety of running.
The axle-drive, mounted on to the axle conveys the traction power from the electric traction engine through a cardan shaft, to the axle. Running in electric break mode the traction power flow is reversed. The mass of the drive is reduced to minimal to ensure the minimum unsprung mass. The modern, double sealing system minimize the lubricant leakage opportunity, preventing the contact between the lubricant and the environment. The geometric design of the axle-drive gears keeps the sound pollution of the drive on a low level.
The primary springs are spiral, steel springs mounted between the bogie frame and the axle bearing houses. Designing the springs allows the regulation of the rotation of the axle bearing houses ie the “off-road skill”.
The weight of the body of the coach is conveyed to the bogie frame by two rubber-steel sheet spring. This secondary spring ensures that the bogie can rotate compared to the body frame in a curved track and after the curve has ended it ensures that the bogie returns its original position. The benefit of this design compared to the traditional side-bearer is this solution does not need lubricant nor maintenance. Beside it is environmentally friendly it has quite good vibe and noise absorption, that highly improve the passenger comfort.
The draw-gear conveys the longitudinal forces (traction force, breaking force) between the bogie and the body frame. The draw-gear is “Z” shaped, which consist of a bogie-bolster, perpendicular to the working direction, and two draw-bar parallel with the working direction. The draw-gear is rigid in longitudinal way, however it ensures the rotation of the bogie and a slight horizontal movement of it. The benefit of the “Z” shaped design is this design does not convey minor track defects from the bogie to the body frame, thus it improves the passenger comfort. Further advantage of the “Z” shaped design is this allows a smooth transition to the body frame from a straight track to a curved track, improving the passenger comfort even further.
The brake set is traditional, it has got brake-block and brake-rigging. The wheels are braked one side, from the center of the bogie. Thanks to the braking mode of the electric drive the block-brake will be used practically only as fixing brake. Using this method the block-brake lifespan will be multiplied compared to the traditional block-brake braking method.