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6 3.0 VEHICLE CHARACTERIZATION AND ON-TRACK TESTS All testing was performed on DART property located in Dallas, Texas. DARTâs operating conditions provided a variety of track structures and a wide range of operating speeds. The following is a summary of the variety of conditions that were tested on the DART system: ⢠Tunnel 3.5 miles in length with direct fixation track ⢠Ballasted track with concrete ties ⢠Direct fixation track ⢠Embedded track ⢠Curvature range from 2 degrees (2,800 feet radius) to 20 degrees (300 feet radius) ⢠Overhead catenary system ⢠Operating speed 25 to 60 mph ⢠Rail profile 115 pound/yard rail Figure 1 shows a map of the DART rail system. The testing took place on the entire Red Line from Westmoreland Station to Parker Road Station (7 oâclock to 1 oâclock on the graphic). Figure 1. DART Rail System Map
7 DARTâs Super Light Rail Vehicle (SLRV) was used for testing. The SLRV is a three-section vehicle that can accommodate up to 150 seated and standing passengers. The vehicle is manufactured by Kinkisharyo. Figure 2 shows a picture and a schematic of the SLRV. Table 3 summarizes some of the design specifications of the vehicle. Figure 2. DARTâs SLRV Table 3. SLRV Design Specifications DART Super Light Rail Vehicle Weight AWO Empty 140,500 pounds AW1 Full seated load 100 passengers 155,900 pounds AW2 Full seated and standing load 150 passengers 163,900 pounds Length Width Height 123 feet 106 inches Lockdown Height 156.0 inches Operating Height 13 feet 6 inches to 22 feet 6 inches Primary Suspension System Chevron Secondary Suspension System Airbag Wheel Profile DART-HP02
8 3.1 Vehicle Characterization Tests TTCI has often found that actual vehicle characteristics as assembled can vary considerably from the published design and measured individual components. In order to ensure an accurate NUCARS model of the DART SLRV, tests were conducted to measure suspension characteristics and carbody inertial and resonance characteristics. Testing included the following: ⢠Characterization of the elastic elements of the primary and secondary suspension ⢠Determination of the center of gravity of the railcar ⢠Determination of the resonance frequencies of rigid body degrees of freedom of the railcar Results of the characterization tests were used to update and verify the preliminary NUCARS model. 3.1.1 Carbody Resonance Tests Carbody resonance testing was conducted to determine the rigid body modes of vibration of the SLRV. Figure 3 shows an example of the rigid body modes that were excited during the test. The SLRV was instrumented with accelerometers. Figure 4 shows the locations of the instrumentation and Table 4 describes the type of accelerometer used in the test. The rigid body modes of vibration were each excited by hand by two TTCI engineers with assistance from two transit authority employees. Figure 5 shows how the car can be excited by hand.
9 Bounce (All bodies in phase) Upper and Lower Center Roll (All Bodies in Phase) U-Shaped Pitch (A and B bodies out-of-phase) Zig-Zag Yaw (A and B bodies in phase) Figure 3. Illustration of Measured Rigid Body Vibration Modes A-Carbody C-Carbody B-Carbody
10 Figure 4. Location of Carbody Resonance Test Instrumentation (plan view) Table 4. Carbody Resonance Instrumentation Description Location No. Description 1 Vertical Accelerometer 2 Vertical and Lateral Accelerometer 3 Lateral (top) Accelerometer 4 Lateral Accelerometer 5 Vertical Accelerometer 6 Vertical Accelerometer 7 Vertical and Lateral Accelerometer 8 Lateral Accelerometer 9 Lateral (top) Accelerometer 10 Vertical Accelerometer 11 Vertical Accelerometer 12 Vertical and Lateral Accelerometer 13 Lateral (top) Accelerometer 14 Lateral Accelerometer 15 Vertical Accelerometer
11 Figure 5. Using a Crowbar to Excite Carbody Yaw Vibration Mode 3.1.2 Bogie Resonance Bogie and primary suspension resonance tests were performed using a load cell hammer and accelerometers placed on the bogie frame. The bogie frame is impacted by the load cell hammer. The accelerometers measure the response of the bogie frame and traction motor mounts. The test was performed on both a motor and trailer truck. The trucks tested were rolled out from under a carbody. Figure 6 shows this type of test. Figure 7 illustrates where the accelerometers were located for this test. The accelerometers were positioned to take longitudinal, lateral, and vertical measurements. Bogie suspension characteristics were estimated from the results of these resonance tests. Crowbar used to excite yaw vibration mode.
12 Figure 6. Hammer Test and SLRV Motor Truck Figure 7. Accelerometer Locations for Motor Truck (top) Accelerometer Locations for Trailer Truck (bottom)
13 3.1.3 Suspension Stiffness In the suspension stiffness test, the longitudinal, lateral, and vertical stiffnesses of the primary and secondary suspension were measured. A force was applied across the suspension. The force was measured with a load cell and displacements were measured with dial indicators on magnetic bases. DART had equipment that is used to straighten carbodies. This equipment was used for the lateral and longitudinal pull tests. It was anchored into the floor and provided a fixed point to pull against the suspension. Figure 8 shows the equipment setup for the longitudinal pull test. A similar reaction frame installation was used for the lateral suspension stiffness tests. Figure 8. Setup of Longitudinal Pull Test
14 The vertical suspension was measured utilizing the lifts at DART. Load cells were placed under the wheels of the truck being measured. Figure 9 shows the load cells in place. The lift was used to raise the carbody off of the suspension in order to measure the stiffness of the suspension system. Figure 10 shows a photograph of the SLRV on the lift. Figure 9. Wheel Load Cells Figure 10. SLRV on Vertical Lift Load cells located under wheels
15 3.2 Track Inspection and Track Geometry Measurements A track inspection was done on the DART Red Line. Miniprofâ¢5 Figures 11 and 12 show examples of Miniprof profiles taken in a curve and on tangent track. Figure 13 shows some of the track geometry issues documented during inspection. Overall, the track was in good condition. There were several areas where rail corrugations, sun kinks, and ballast migration were evident. At the time of the inspection, the weather was very hot (110°F), and sun kinks were developing and being corrected on a regular basis. profiles where taken at locations where problems were known to have occurred. Representative rail profiles were also taken in curves, curve transitions, and tangent track. Track issues and locations were documented to be compared with ride quality data. Figure 11a. Curve Rail Profiles High Rail 5 Miniprof is a portable piece of equipment by Greenwood Engineering that measures wheels, rails, and brake discs
16 Figure 11b. Curve Rail Profiles Low Rail Figure 12. Tangent Rail Profiles MiniProf for Windows Version 2.4.63 Page 1 of 1 Date: Thursday, April 07, 2011 Time: 2:42:37 PM Copyright(c) 1997-2005, Greenwood Engineering -30 -20 -10 0 10 20 30 40 50 -55 -50 -45 -40 -35 -30 -25 -20 -15 -10 -5 0 5 10 15 20 08022010-0081.ban 02/08/2010 210-0152 Line = Direction = Position = Rail = W1 = 4.618 mm W2 = 5.443 mm W3 = 5.984 mm Gauge = 1434.269 mm
17 Figure 13. Track Geometry Issues Track geometry measurements were taken by Holland August 13 and 14, 2010, on DART Red Line in both directions. Measurements were taken with Hollandâs TrackSTAR® system (Figure 14). It is a heavy, high rail track testing unit that provides track measurement of geometry, rail wear, and track gauge strength using a noncontact inertial and laser optical measurement system. The truck weighs approximately 55,000 pounds, and testing speeds range from 10 to 35 mph. No measurements were taken in the DART tunnel (between Pearl and Cityplace) because of a size restriction in the tunnel. Data from a previous track geometry run was used for the tunnel. The tunnel has direct fixation track; and therefore, it was assumed that track geometry changes in the time since the previous run was negligible. Sun Kink
18 Figure 14. Hollandâs TrackSTAR Vehicle The data provided by Holland was in space curve format. Mid-chord offset data (MCO), while useful for track maintenance purposes, can filter out important information needed for input to simulation models and PBTG analyses.6 Figure 15 shows an example of how a signal amplitude may be reduced using MCO data. Certain wavelengths are completely filtered out and cannot be reconstructed. Space curve data is the best option to investigate the correlation between track geometry and ride quality. Figure 16 shows the information that is needed to describe the track geometry. Figure 15. MCO Measurement Issue 6 Cohen, A. and W.A. Hutchens. 1970. âMethods for the reconstruction of rail geometry from mid-chord offset data.â ASME, 70-Tran-24.
19 Figure 16. Required Track Geometry Information 3.3 Ride Quality Test A ride quality test was conducted on DARTâs Red Line. The test conditions were similar to typical revenue service operations. Tri-axial accelerometers were placed on the floor under the operatorâs seat, on the floor over the bogie, and on the center of the vehicle. The accelerometers measured the vehicleâs response to operating conditions and inputs from the track structure. A gyrometer was also placed on the floor under the operatorâs seat. The gyrometer was used to measure carbody rotation to correlate the effect of curves and curve transitions on ride quality. This information will be used to correlate ride quality issues with track geometry. Figure 17 shows an example of the instrumentation and data acquisition system. Figure 18 is a schematic of the instrumentation location. Table 5 is a description of the accelerometers at each location.
20 Figure 17. Ride Quality Instrumentation Figure 18. Location of Ride Quality Instrumentation (plan view)
