Using Parametric Simulation to Optimize Suspension Design

A project to design and implement suspension improvements to Amtrak’s F-40 Non-Powered Control Unit (NPCU) cars is described. The cars, built from former F-40 locomotives, had a history of poor ride quality. Rail Sciences Inc. (RSI) inspected one of the cab cars and measured its ride quality. Peter Klauser modeled the vehicle in NUCARS™ and validated the model against the test data. The vehicle response was primarily in pitch and bounce modes. To optimize the suspension, Klauser simulated vehicle response for a range of four suspension parameters: primary stiffness and damping, and secondary stiffness and damping. Nearly 2600 suspension combinations were considered. Simulation file setup and data analysis were performed automatically using parameter analysis software interacting with NUCARS™. The result was a five-dimensional response contour for each output variable, such as the engineer’s seat vertical and lateral accelerations, and car body acceleration. The most cost effective stiffness and damping parameters were selected from the response contour and translated into component specifications. RSI then provided Amtrak with new axle box springs and dampers, and re-tested the vehicle. The test result closely followed the predicted results from the simulation. Engineer’s seat vertical and cab lateral accelerations improved by 42% and 32% respectively for the worst-case conditions in the test territory.

Locomotive Cab Occupant Protection

The effectiveness of fitting a locomotive cab with a passive inflatable restraint system utilizing inflatable structures, and interior padding to protect the operator has been evaluated for the in-line collision scenario. It is a challenge to design a system that increases protection for the locomotive operator within the cab during accidents, while allowing that operator to react to a specific situation by choosing either to leave or remain in the seat or cab. Numerous strategies have been proposed to increase locomotive cab occupant protection; however, most of these proposals have either required an active response from the cab occupants, e.g., getting into a refuge, or inhibited the potential for fleeing the cab, e.g., seatbelts. In this study, the occupant protection of a typical locomotive cab interior with a vertical console-stand style control is compared with the occupant protection of an interior modified with the addition of two tube-shaped inflatable structures for secondary impact injury mitigation. The crashworthiness performances of these two interior arrangements are compared for in-line train-to-train collision scenarios that approximate a locomotive-led train collision with another locomotive or cab car-led train. The analysis uses, as a basis, accident data and information on the crashworthiness performance of the locomotive interior in a train-to-train collision between a standing locomotive-led consist and a moving cab car-led consist conducted on January 31, 2002 at the Transportation Technology Center in Pueblo, Colorado. An analysis model is developed and validated using the full-scale train-to-train test locomotive interior/occupant experiment. The interior/occupant model then serves as a means of interpolating to different crash pulses, and with the alternative protection method using inflatable tube-like structures and interior padding. A range of locomotive operator sizes is investigated, as well as a range of selected initial seating positions for the locomotive operator.

Performance of a Track Geometry Car-Based Real-Time Dynamics Simulator Using Multiple Vehicle Types

A real-time dynamic simulation system designed to identify sections of track geometry that are likely to cause unsafe rail vehicle response is discussed. Known as TrackSafe, this system operates onboard a track geometry vehicle where the geometry measurements are passed as inputs to the dynamic model of one or more rail vehicle types. In order to comprehensively analyze the effect of the existing geometry on rail vehicle behavior, the system is capable of simultaneously simulating the response of several vehicle models, each over a range of traveling speeds. The resulting response predictions for each modeled vehicle and each simulated traveling speed are used to assess the track geometry condition and to identify locations leading to potentially unsafe response. This paper presents the latest work in the development of TrackSafe, specifically, the development and testing of eight new vehicle models is presented. The new car types modeled include a box car, flat car, and both a long and short tank car. Each can be simulated in a fully loaded or empty condition. Accuracy of the models is discussed in detail.

The Development of a Wayside Detection System for the Identification of Hunting Rail Car Trucks

A hunting truck detector was developed to identify that small portion of the rail car population that exhibits hunting behavior under normal operating speeds. An algorithm called Hunting Index (HI) was developed to produce a reliable descriptor of hunting behavior without the benefit (and expense) of a fully instrumented measuring zone. A correlation study was performed to relate very low values of the Hunting Index with ride quality to help screen rail cars for their usefulness as carriers of ride sensitive cargo.

Locomotive Crashworthiness Testing at the Transportation Technology Center

Transportation Technology Center, Inc. (TTCI), a wholly owned subsidiary of the Association of American Railroads (AAR), has conducted three full-scale locomotive crashworthiness tests on behalf of the Federal Railroad Administration (FRA) at the FRA’s Transportation Technology Center (TTC), Pueblo Colorado. This paper describes the second and third Phase I tests. The previous test involved a locomotive striking a standing string of hopper cars. The second full-scale locomotive impact test was performed September 10, 2002. The test involved one SD-45 locomotive, modified to meet AAR Specification S-580, and three trailing loaded hopper cars impacting a stationary log truck at a grade crossing at 50.4 mph. A third full-scale impact test, conducted December 18, 2002, involved a locomotive impacting a highway truck loaded with two steel coils on a grade crossing at approximately 58 mph. The rearmost steel coil was aligned with the right side collision post of the locomotive. An anthropomorphic test device (ATD, or test dummy) was placed seated on the floor in the nose of the locomotive, facing rearward with its back against the interior door.

Pilot for a National Detector Database to Enhance Safety and Promote Preventive Maintenance

The Federal Railroad Administration has embarked on a pilot project to demonstrate the feasibility of using and linking defect detector systems for rail vehicles across North America. The goal of this project is to develop a national database that will enable the railroad industry to engage in predictive maintenance. These detectors measure equipment performance parameters such as the forces between the wheel and rails. The Integrated Railway Remote Information Service or InteRRIS™, an Internet-based system designed and developed by Transportation Technology Center, Inc. (TTCI), was used to aggregate, interrogate, and store data from field-deployed detector systems. TTCI is a wholly owned subsidiary of the Association of American Railroads (AAR). A key task of this program was the determination and implementation of appropriate access to a National Rail Corridor Vehicle Performance Database (VPD). The VPD can draw performance-based data from InteRRIS™ for the FRA and the railroads responsible for the safe operation of cars and locomotives as needed to enable effective performance-based safety monitoring. The VPD has been populated with data from a number of Truck Performance Detectors (TPD) and Wheel Impact Load Detectors (WILD™) in order to capture representative and geographically diverse traffic from freight, mixed freight/commuter/passenger lines, and hazardous materials lines. Both the AAR and FRA have a mutual interest in promoting the implementation of performance-based maintenance. It is hoped that this detector network and associated national database reduces the need for visual inspections on cars and locomotives, thereby focusing more efforts on preventive action and making repairs. This could greatly enhance the efficiency with which railroads make critical repairs in a timely manner. Such tools, with detector data in a central database, should they prove feasible, could eventually lead to the development of performance-based inspection standards.

Design of an Emergency Egress System for Locomotive Cabs

Improving the survivability of a locomotive crew in the event of an accident has been a concern of the Federal Railroad Administration in the past decade. Locomotive crashes can injure the crew as well as deform the locomotive cab. Exiting from a deformed cab can be difficult, particularly for injured crewmembers. Egress becomes an even greater challenge if the locomotive is toppled. From an initial list of emergency egress concepts, the following three were chosen for further development: 1) hand/footholds to aid climbing inside a toppled locomotive, 2) roof-mounted escape hatch, and 3) externally removable windshield. As the potential users of the egress system, train crews and emergency rescue workers were interviewed to provide feedback on the design concepts. Focus groups with locomotive engineers and conductors provided information about train crew perceptions of the three concepts. Interviews with rescue personnel provided a perspective on the concerns of emergency rescue operations. Based on the user feedback, the roof-mounted escape hatch with hand/footholds was selected as the preferred concept. Construction of a system mockup facilitated evaluation of this concept. The utility of the overall concept was evaluated using untrained personnel in the full-scale mockup of a toppled road locomotive cab. A preliminary examination of the cost implications of incorporating the hatch system into new locomotives indicated that the initial engineering costs, rather than the recurring manufacturing costs, are the issue. As such, the overall cost for implementing the hatch is likely to be low.

The Kinematic Basis for an Improved Friction Wedge Model

One of the reasons the three-piece truck is the dominant design in the North American freight rail industry is the efficiency of the friction wedge damping system. Even with the proliferation of the system there is a limited understanding of the mechanics of its operation and an absence of mathematical models capable of accurately simulating systems employing friction wedges. This paper presents the kinematic basis for an improved two-dimensional friction wedge model that is capable of more accurately simulating the system.

Qualification and Acceptance Testing of a High-Speed Passenger Locomotive Using Instrumented Wheelsets

New Jersey Transit’s (NJT) ALP-46 locomotives have been successfully introduced into revenue service. On April 7, 2003, NJT received Federal Railroad Administration (FRA) approval to operate at 100 mph on Amtrak’s Northeast Corridor. Bombardier Transportation (Holding) USA, Inc. supplied these all-electric locomotives after proving the safety and performance of their product by passing an aggressive test specification prescribed by the FRA. The FRA specifications call for strict dynamic performance and compliance with wheel/rail interaction forces. Transportation Technology Center, Inc. (TTCI), a wholly owned subsidiary of the Association of American Railroads (AAR), designed and constructed two instrumented wheelsets (IWS) for use on NJT’s ALP-46 Locomotive Project. This Cardan drive locomotive required an innovative wheelset design because the right and left wheel plate shapes were not the same. To complete this unique system, TTCI incorporated a new amplifier system that digitized all the signals and transmits them via a single fiber optic cable to the data collection and analysis computer. This system eliminated the need for traditional slip rings normally used to transmit signals from rotating equipment. The vehicle qualification tests were conducted on Bombardier’s ALP-4601 locomotive in Amtrak’s Northeast Corridor (NEC) from Newark, New Jersey, to Philadelphia, Pennsylvania. The maximum speed achieved was 110 mph and the maximum cant deficiency (CD) was 6 inches. The FRA criteria for the vehicle qualification test were pre-programmed into TTCI’s real-time data analysis system to produce exception reports every 3 minutes during the actual testing. All data and any exception reports are referenced to a milepost via Global Positioning System (GPS) signals that are incorporated as part of the data collection.

2002-2003 Report of Survey Committee: Progress in Passenger Rail Vehicles, Components and Systems

This annual ASME committee report covers selected worldwide developments in passenger rail vehicles, components and systems. The information contained herein was obtained from responses to survey letters sent to the manufacturers of passenger rail vehicles and components, and from review of trade and technical publications.