Interface - The Journal of Wheel/Rail Interaction

RAIL PROFILE OPTIMIZATION

Profile Optimization in the Urban Rail Context(continued)

The left part of Figure 3 shows the results of a measurement run on metro line U1. The conicity is shown as a function of the gauge in a scatter diagram. The conicity is within the specified range, except for a small section. The illustration indicates that tight gauge leads to higher conicity. Unfavorable profile pairings and stresses may exacerbate these adverse effects.

Wiener Linien varied the rail profiles to improve contact geometry. By distributing the contact patch locations, the railway was able to keep the equivalent conicity within a favorable range and improve rolling radius difference for better curve negotiation. Modifying the rail head radii provided a slightly wider gauge where desired to improve rolling radius difference.

As a result of regular measurement and automated rail-profile analysis, which includes wear, head radii and equivalent conicity (see Figure 3), rail conditions can be evaluated, grinding programs can be planned, and the remaining life of rail in each track segment can be estimated.

Wheel Measurement
Just as measurement of rail conditions represents an essential aspect of managing wear, measurement of wheel conditions provides the ability to monitor wheel tread and flange wear, and the damage mechanisms that affect rail and wheel service lives. And just as the use of mechanical gauges to check rails in track have given way to automated, laser technology, the mechanical gauges and templates used to check wheel geometry in the shops have been replaced by automated, precision measuring devices.

The wheel flanges on the leading wheelset of the "pushed drawbar wheels" at portal 1 have by far the highest wear rate of the whole vehicle. Compared to the wear of the wheel flanges of the leading wheels of conventional tram railcars, the average wear is approximately 40% higher. This dramatic wheel wear shown through MiniProf measurements during long-term tests of ultra-low-floor (ULF) vehicles with self-steering independently rotating wheels (built into articulation portals), led to mandatory periodic inspection of wheels on all vehicles every 10,000 kilometers. This, in turn, led Wiener Linien to purchase automated wheel profile measuring equipment that collects wear data in an integrated database that is used to plan maintenance requirements on the system.

Figure 4 shows the change in the entire profile shape of individual wheels. Since trams have doors on the right hand side only, the door-side portal (right) is pointing upward and the window-side portal (left) is pointing downward with reference to the original profile. The left side of Figure 4 shows the evolution of the tape circle diameter of all individual wheels (P1 fs = portal 1 left side, P1 ts = portal 1 right side; down to portal 6) as groups of curves at the times of individual measurement. Ranging from an almost unworn state (with a diameter of 680 mm and a kilometric performance of 832 km) to conditions after almost 40,000 km of service, wheels on the first and last portal are clearly subject to greater wear. The wheels at the first portal required re-profiling after approximately 28,000 km. Owing to the unfavorable profile shape, it was necessary to remove almost 30 mm to reestablish the original profile. The different rates of wear of the individual wheels (diameter plotted above kilometric performance) can be seen on the right side of Figure 4.

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