Handbook of Railway Vehicle Dynamics

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454 Torque Before abogie rotation test is carried out, the bogie is normally moved slowly to it maximum rotation position to check clearances between all body and bogie mounted equipment. 3. Sway Test Bogie Rotation (a) Airspring/flexicoil suspension Torque (b) Friction sidebearers Bogie Rotation FIGURE 13.31 Typical bogie rotation test results for common suspension types. Bogie Rotation Such tests are normally carried out to generate the input data for the kinematic gauging process or to verify that the vehicle will remain within apredetermined static envelope. Their usefulness to the dynamics engineer is in enabling areasonable estimate of the parasitic stiffnesses (particularly in roll and lateral directions) to be made. Anumber of targets are fixed to the end of the vehicle at cantrail, waistrail, and solebar level. One side of the vehicle is raised in stages to approximately 108 of cant. Atheodolite placed some distance from the end of the vehicle is used to measure the displacement of the targets as the vehicle is raised. Additional measurements of vertical and lateral suspension movement may prove useful when comparing test and model results (Figure 13.32). FIGURE 13.32 Sway test. Source: Photo —courtesy of Serco Railtest Ltd. © 2006 by Taylor & Francis Group, LLC Handbook of Railway Vehicle Dynamics Torque (c) Air spring/flexicoil suspension +yaw dampers with positional control
Field Testing and Instrumentation of Railway Vehicles 455 Psd g*g/Hz (E-3) 2.00 1.80 1.60 1.40 1.20 1.00 0.80 0.60 0.40 0.20 4. Body Modes Tests Such tests are generally commissioned toprovide the dynamics engineer with confirmation of the fundamental vibration modes of various parts of the vehicle. They are useful for comparison with the eigenvalue analysis used at the model checking stage as they will include the effects of all the parasitic stiffnesses. Tests are usually performed by disconnecting the vehicle dampers and then applying asine sweep displacement signal in the direction of interest via an electric or hydraulic actuator. The response of the vehicle body is measured using both vertical and lateral accelerometers mounted at various positions along the length of the vehicle. These tests may also be used to confirm the first body bending mode. B. D YNAMIC T ESTS 0.00 0.00 5.00 10.00 15.00 20.00 25.00 30.00 35.00 40.00 45.00 50.00 FREQUENCY (Hz) FIGURE 13.33 PSD of body vertical acceleration, mainline diesel locomotive. Vehicle ride tests providethe means to validate the dynamic behaviour of amodel. The vehicle will typically beinstrumented with accelerometers at various positions on the body, bogie frame, and axle boxes, and this may be complemented with displacement transducers to measure primary and secondary suspension displacements. To be of maximum value for model validation purposes, the data should also include the vehicle speed and location and be accompanied by recent track recording coach data for the test route and measured wheel profiles from the vehicle at the time of the test. Raw acceleration data from ride tests is normally expressed interms of the power spectral density (p.s.d.) of the signal vs. its frequency range, asshown inthe example in Figure 13.33. The test data p.s.d. plots are likely toinclude peaks representing the rigid body modes, flexible modes, and rail length passing frequencies. They may also include peaks associated with the traction unit, originating from vibration of the engine or driveline.The results may be further sorted into speed banded p.s.d. to assist in identifying speed dependent effects such as excitation of various © 2006 by Taylor & Francis Group, LLC
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Handbook of Railway Vehicle Dynamics

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