Passenger transport today moves significantly faster than ever before, often operating on separate tracks especially designed for high-speed trains. Accordingly, high-speed rolling bearings are very important components in the bogies of trains today. Maximum train speeds currently reach 380 km/h (236 mph) in the latest high-speed applications—80% higher than in the earlier days of high-speed traffic.
There are different bearing types in use other than journal bearings for transmissions used in railway vehicles, and the lubrication system is completely different from that used in axle boxes. While grease lubrication is used in axle box bearings and most traction motor bearings, transmission bearings are oil-lubricated. The lubricant for the bearings usually is the same as for the gearing, as this facilitates the design of the transmission housing. The fact that lubricants that are superior for the gear tooth system are not necessarily ideal for the lubrication of the rolling contact of the transmission bearings is another issue—far beyond the scope of this paper. The number of reduction stages inside a transmission can vary; for railway bogies there are both single-stage and double-stage transmissions. Figure 12 shows an example with four cylindrical roller bearings and a hollow output shaft.
2021-09-01