Performance-Based Track Geometry, Phase 1 (2012)

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21 Table 5. Instrumentation Description Location Description 1 Lateral, Longitudinal, Vertical Accelerometers under operator’s seat on floor. Gyrometer under operator’s seat. 2 Lateral, Longitudinal, Vertical Accelerometers on cabin floor over bogie. 3 Lateral, Longitudinal, Vertical Accelerometers on cabin floor in center of A-car. 4 Lateral Accelerometer between A-Car and C-car. 5 Lateral Accelerometer between C-Car and B-car. 6 Lateral, Longitudinal, Vertical Accelerometers under operator’s seat on floor. Gyrometer under operator’s seat. 4.0 VEHICLE CHARACTERIZATION DATA ANALYSIS The data collected during vehicle characterization testing was used to make the NUCARS model a more accurate representation of the DART SLRV. 4.1 Carbody Resonance Test During the carbody resonance test, accelerations were measured at locations described in Figure 4 and Table 4. These accelerations were analyzed to determine the frequency content and type of resonance excited. Figure 19 shows an example of raw acceleration data taken during the carbody resonance test. The data was processed to determine which rigid body motion was excited.

22 Figure 19. Raw Acceleration Data from Carbody Resonance Test A cc el er at io n D at a (G s)

23 Figure 20 shows the result. A fast Fourier transform (FFT) calculation was done to determine the frequency of the lower center roll mode. The frequency is approximately 0.5 Hz. Figure 21 shows the FFT for this particular data. All three sections of the vehicle carbodies were in phase. Figure 20. Lower Center Roll Rigid Body Vibration Mode Figure 21. Lower Center Roll Vibration Mode Frequency

24 Each of the rigid body modes excited during the test were analyzed and their frequencies determined. Table 6 describes all the observable rigid body modes and the respective frequencies. This information was used to update the NUCARS model. Table 6. Rigid Body Vibration Modes and Measured Frequencies Rigid Body Mode Frequency (Hz) NUCARS Model Frequency (Hz) Lower roll 0.50 0.50 Upper roll 2.00 2.02 Bounce 1.25 1.26 Pitch (all bodies in phase) 1.28 Pitch (u-shape) 1.50 1.50 Yaw (all bodies in phase) 1.42 Yaw (zigzag) 1.75 1.80 Yaw (u-shape) 1.57 This information was used in eigenvalue analysis to determine the values of air suspension characteristics, carbody moments of inertia, and carbody center of gravity. The measured resonance frequencies were compared to the calculated values of the NUCARS model. Adjustments were made to the model’s suspension stiffness, center of gravity, and carbody inertias, and the resonance frequencies were recalculated. The model parameters were adjusted until the calculated values matched the measured values of the SLRV. 4.2 Bogie Resonance Test The bogie resonance test was performed to characterize the stiffness and damping of the bogie frame and traction motor mounts. An instrumented hammer was used to impact the bogie and excite modes of vibration. Accelerometers were used to measure the response. Both a trailer and a motor truck were characterized. The motor truck was characterized in longitudinal, lateral, and vertical directions. The traction motor is mounted to the truck at three points. Figure 22 shows the motor mount locations. The axle motor mount acts like a rigid connection. The pin mount and side frame mount effective stiffness and damping were characterized.

25 Figure 22. Traction Motor Mount Locations Figure 23 shows the hammer input and output for the vertical directions of the traction motor mounts. The output from the pin and side frame mount were averaged to determine if a bounce mode existed and its frequency. The output from the pin and side frame mount were also subtracted to determine if a pitch mode existed and the frequency of that mode. Figure 24 shows the reduced data and frequency analysis. Axle Motor Mount Pin Motor Mount Side Frame Motor Mount

26 Figure 23. Hammer Input and Resulting Output — Vertical Direction Time (seconds) (6) Bolster Mount (Gs) (5) Axle Mount (Gs) (3) Single Pin Mount (Gs) (2) Hammer Input (lb)

27 Figure 24. Time Domain Data and Frequency Content from Hammer Test Frequency (Hz) Time (seconds) (8) Subtract SF from Pin (Gs) (7) Average of SF & Pin (Gs)

28 The bounce frequency of the motor mounts is approximately 12 Hz. The effective stiffness of the motor mounts can be calculated by the following equation: Where: K is stiffness is the natural frequency m is the mass of system The effective stiffness for the motor mount is approximately 27,685 lb/in. The longitudinal and lateral directions were analyzed with the same procedure as the vertical for both the motor and the trailer. The effective damping can be calculated from the decay of the vibration. The equation used is the following: tAey α−= Where: A is a constant α = c/2m (c is damping and m is mass) t is period of decay Figure 25 shows the decay of the vertical motor mount accelerations. The damping is 84 lb-sec/in. Table 7 summarizes the results.

29 Figure 25. Decay Plot of Vertical Motor Mount Accelerations Table 7. Bogie Resonance Test Summary Frequency (Hz) Effective Stiffness (lb/in) Effective Damping (lb-sec/in) Motor Mounts Vertical 12 27,685 84 Motor Mounts Lateral 10 12,677 70 Motor Truck Side Frame Vertical 9 11,937 40 Motor Truck Side Frame Lateral 14 26,101 39 Trailer Truck Side Frame Vertical 9 19,730 47 Trailer Truck Side Frame Lateral 10 24,358 35 4.3 Longitudinal Stiffness Test The longitudinal stiffness test was performed to determine the primary and secondary effective stiffness in the longitudinal direction. The DART maintenance facility was equipped with car frame straightening equipment. This equipment provided a reaction point for the load. Displacement measurements were taken across both the primary and secondary suspension systems. Force-displacement slopes were calculated for the different runs. The calculated stiffness values for all runs were averaged to determine the effective stiffness of the primary suspension system. Figure 26 shows the displacement and load measured during y = 0.0846e-4.929x R² = 0.9085 -0.025 -0.020 -0.015 -0.010 -0.005 0.000 0.005 0.010 0.015 0.020 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 A cc el er at io n (G s) Time (s)

30 the test. Figure 27 shows the force-displacement output and the calculated slope. The load was divided in half to account for the two chevrons in the system. Figure 28 shows the chevrons. Table 8 shows the values determined from the test in comparison to the manufacturer specified values. Figure 26. Longitudinal Displacement and Load Measurements Figure 27. Force-Displacement Diagram and Calculated Slope 0.000 0.010 0.020 0.030 0.040 0 20 40 60 80 D is pl ac em en t (in ) Time (sec) 0 2000 4000 6000 8000 10000 0 20 40 60 80 Lo ad (l b) Time (sec) y = 154640x + 2522.3 R² = 0.9886 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 0.000 0.005 0.010 0.015 0.020 0.025 0.030 0.035 0.040 Lo ad (l b) Displacement (in)

31 Figure 28. Primary Suspension System – Chevrons Table 8. Longitudinal Primary Suspension Stiffness Suspension Component Manufacturer Value Average Measured Value Difference Motor Primary Chevron 142,700 lb/in* 171,140 lb/in 19.9% Trailer Primary Chevron 91,400 lb/in* 87,180 lb/in 4.6% *Manufacturer’s information was not available. Specifications of similar chevrons were used for preliminary model. 4.4 Lateral Stiffness Test The lateral stiffness test was performed to determine the effective lateral stiffness for the primary and secondary lateral suspension systems. The frame straightening equipment was also used for this test. Force-displacement slopes were calculated for the different runs. The calculated stiffness values for all runs were averaged to determine the effective stiffness of the primary suspension system. Figure 29 shows the displacement and load measured during the test. Figure 30 shows the force-displacement output and the calculated slope. The load was divided in half to account for the two chevrons in the system. Table 9 shows the primary suspension stiffness values determined from the test in comparison to the manufacturer’s specified values. The secondary suspension stiffness was validated during the carbody resonance test and eigenvalue analysis.

32 Figure 29. Lateral Displacement and Load Measurements Figure 30. Force-Displacement Diagram and Calculated Slope Table 9. Lateral Primary Suspension Stiffness Suspension Component Manufacturer Value Measured Value Difference Motor 17,700 lb/in* 41,200 lb/in 132.0% Trailer 20,500 lb/in* 22,700 lb/in 10.7% *Manufacturer’s information was not available. A specification of a similar chevron was used for preliminary model. 4.5 Vertical Stiffness Test The vertical stiffness test was performed to determine the effective vertical stiffness for the primary and secondary lateral suspension systems. Load cells were placed under each wheel of a motor truck. The carbody was then slowly lifted off of the truck. The displacements of the suspension systems were measured. The calculated stiffness values for all runs were averaged to determine the effective stiffness of the primary suspension system. Figure 31 shows a typical primary suspension displacement and load measured 0 0.01 0.02 0.03 0.04 -30 20 70 120 D is pl ac em en t (in ) Time (s) 0 500 1000 1500 2000 -30 20 70 120 Lo ad (l b) Time (s) y = 23558x - 10.507 R² = 0.9902 0 100 200 300 400 500 600 700 800 900 0 0.01 0.02 0.03 0.04 Lo ad /2 (l b) Displacement (in)

33 during the test. Figure 32 shows the corresponding force-displacement output and the calculated slope. The load was divided in half to account for the two chevrons in the system. Table 10 shows the primary suspension stiffness values determined from the test in comparison to the manufacturer’s specified values. Figure 31. Vertical Displacement and Load Measurements Figure 32. Force-Displacement Diagram and Calculated Slope Table 10. Vertical Primary Suspension Stiffness Suspension Component Manufacturer Value Measured Value Difference Motor 7,428 lb/in 10,500 lb/in 41.35% Trailer 6,292 lb/in 7,400 lb/in 17.60% 0.00 0.05 0.10 0.15 0.20 0.25 0 100 200 300 400 D is pl ac em en t (in ) Time (s) 0 2000 4000 6000 8000 0 100 200 300 400 Lo ad (l b) Time (s) y = -17634x + 4787.6 R² = 0.8627 0 500 1000 1500 2000 2500 3000 3500 4000 0.00 0.05 0.10 0.15 0.20 Lo ad /2 (l b) Displacement (in)