Handbook of Railway Vehicle Dynamics

Field Testing and Instrumentation of Railway Vehicles 453
FIGURE 13.29 Wheel unloading test.
vehicle. The test is usually performed at 0.2 and 1 8 /sec rotation speeds and the torque required to
rotate the bogie is measured (Figure 13.30). Where yaw dampers are fitted, they may or may not be
disconnected during the test depending on the test requirements. If yaw dampers with positional
control (i.e., designed to blow-offataparticular bogie rotation angle) are included, the results from
the test will reflect both the velocity and displacement dependent nature of such an arrangement.
It follows that the vehicle modelmust be simulated in the same condition if comparable results are
to be achieved. The resulting X -factor is calculated as follows:
X ¼
Body to bogie yaw torque
Wheelbase x axleload
The limiting value is 0.1 except for freight vehicles , 8tonnes axle load.
The measured bogie rotation torques are particularly useful when confirming the behaviour of
avehicle model with friction sidebearers or airspring secondary suspensions. Typical examples
of results from such tests for various vehicles are shown inFigure 13.31.
FIGURE 13.30 Bogie rotation test.
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