The Effect of Friction Modifiers on Wheel/Rail Isolation

Train detection, for signalling purposes, is often by means of track circuits. Signalling block occupancy is triggered by the wheelset of the train ‘shorting out’ the track circuit, i.e. the wheels and axle act as a shunt. Contamination on the track such as ballast dust, rust, oil, or leaves as well as substances designed to improve train operation such as friction modifiers or sand may cause the contact between the wheelsets and the track to be compromised, inhibiting train identification. In previous work a twin disc approach has been used to study the effect of sand (used to improve adhesion) and leaves on wheel/rail isolation. Friction modifiers are of significant current interest in wheel/rail research. Introducing a new material into the tread/top of rail interface can raise questions about the impact on signalling systems. Although no significant effects have been observed in practical operation on a range of railway systems, the intention in this work was to evaluate conductance between wheel and rail in a more controlled and systematic fashion using the previously established methodology. Using the twin disc technique, friction modifier, in the form of a solid stick, was applied using a spring loaded device to the rotating wheel disc to generate a visible film. Tests were run to measure contact impedance at typical loads and slips. Static tests were also carried out using discs pre-conditioned with a friction modifier film. The electrical circuit used was a modified simplified simulation of audio frequency track circuit. No significant difference was observed in the measured impedance for dry conditions with no friction modifier, versus tests where friction modifier was applied, regardless of percentage slip or input voltage. The analysis suggests that the introduction of friction modifier into the existing wheel/rail interfacial film does not result in increased impedance with all other factors being equal.

Rail Car Tracking Device Selection and Power Consumption

Since its introduction, consumer GPS has made the tracking of critical items in the transportation chain more popular. Shipment of items via rail car is one link in the chain that serves to benefit from GPS technology. This paper discusses a wireless communications system suitable for tracking rail cars. In particular, the power source selection and system testing are described. The system was limited to one device and one power source, a battery. Findings show that the lithium battery selected will power the device for one to three years, depending on transmission activity. Recommended areas of additional research include: battery recharging techniques, effects of connecting sensors to the device, and investigating other communications devices as they become available.

Root Cause Analysis of Passenger Side Door System

This paper presents a real-world application of Root Cause Analysis methods that were applied to analyze and resolve a side door problem that was occurring on a particular fleet of coach cars operated by Amtrak. The foundation of a Root Cause Analysis program is a disciplined engineering process designed to identify physical, human and latent roots of chronic or sporadic problems. This paper presents the engineering challenges encountered while conducting root cause analysis of a complex coach car side doors problem. The coach car side doors system exhibited undesirable characteristics when in service. Mechanical staff received multiple reports that during station stops all of the open side doors would unexpectedly close even though the train speed was at zero. During this unexpected side door closing sequence all of the obstacle detection systems were disabled presenting a potential hazard to the traveling public. The side doors Root Cause Analysis team found the Physical Root cause of failure to be located in the door system software code — a finding that was never suspected following years of trouble with the side doors. As a result of this finding, the door manufacturer corrected the software and issued revised software to be installed fleet-wide. The Human and Latent Root causes were addressed through the development of a standard operating procedure and training for conductors and crew on the proper operation of side doors. The Root Cause Analysis method proved to be a powerful and productive process for achieving a solution to a chronic passenger side door problem.

A Rail Mounted Ultrasonic Sensor for Contact Patch Measurement

Failure of a wheel/rail contact is usually by wear or fatigue and both of these depend on the size and location of the contact patch. One contact measuring approach that shows promise is by the use of ultrasonic reflection. If the wheel and rail surfaces make contact and are under high stress they are more likely to transmit an ultrasonic pulse. However, if there is no contact or the contact is under low stress then the wave is completely or partially reflected. By measuring the proportion of the wave reflected it is possible to deduce the extent of the contact area and also estimate the pressure distribution. In previous work [1] static specimens of wheel and rail were measured by scanning a transducer to build up a 2D map of the contact. Whilst this produced good results and agreed well with contact modeling, it is a time consuming process (typically takes 30 minutes for a scan) and could in no way be used for the measurement on-line. In this paper we describe a method that potentially could be used at line speeds and so provide wheel rail contact measurements in field trials. The 2D scan is achieved by using an array transducer that performs a simultaneous line scan. This coupled with the speed of travel of the contact patch over the sensor location can achieve a map of the contact. Specimens were cut from wheel and rail sections and loaded together hydraulically in a biaxial frame. An array transducer was mounted beneath the rail specimen. The array transducer consisted of 64 ultrasonic elements that may be pulsed independently, simultaneously, or with controlled phase difference. In this work all transducers were pulsed simultaneously at repetition rates of 20 kHz. The signals were reflected back from the contact to effectively produce a line scan. The transducer was physically moved, to simulate the translation of the contact patch and so generate a series of reflection profiles. Contacts under a range of normal and lateral loads have been measured and compared with some simple results using pre-inked paper. The paper concludes with a discussion of how this array measurement procedure might be implemented at full line sped and what accuracy could potentially be achieved.

Design of an Intelligent Remote Monitoring and Control of Bangladesh Railway Transport System Using Information and Communication Technologies (ICTs)

In Bangladesh, transport sectors are developing rapidly to meet the increasing demand for transporting passengers and freight inside and outside the country. But there is not such development in railway transport system. The Bangladesh Railway transport system is still using an old technology to monitor and control signalling, scheduling, operations etc. This paper describes various problems in the existing systems and also solutions have been provided considering the existing railway transport systems of Bangladesh. A new system has been developed to control and monitor the total railway transport system from remote locations. While designing the system, various sensors and actuators have been introduced and also Information and Communication Technologies (ICTs) have been applied in the field of railway transport. So a Machatronics aspect of system has been designed to ensure a collision free, safe and efficient operation and management of railway transport system. This system is not only for monitoring and controlling of railway transport but also ensures efficient asset management. As a result face-to-face accidents, cross-road accidents and accidents due to railway line displacements or breakage can be avoided and there will be no loss of assets and valuable human lives.

Effect of Bolt Strength and Loading Conditions on a 7/8” Bolt Within an End-of-Car Arrangement

A cause of failure within end-of-car (EOC) arrangements for cushioned cars with F-shank couplers is that of the yoke bolt failing in shear. This mode of EOC failure is of particular concern due to the concealed nature of the bolt not easily allowing for early detection of the onset of failure. To this end, a finite element analysis (FEA) was performed on a 7/8” bolt and F-bracket assembly to determine the stress state developed within the bolt in an effort to understand the potential cause or causes for the bolt failure. Several parameters, including bolt strength, bolt preload (initial torque), and external loading were varied to determine their effects on bolt performance. The subsequent results indicate that both inherent strength and initial preload have a significant effect on whether a bolt can effectively withstand the various external loading conditions encountered in the field. In addition, it is also apparent that some of the simulation loading scenarios analyzed contain the potential to initiate bolt shearing during operation. From these results, some failure mechanism theories are proposed to describe the type of failure encountered by each bolt grade, either ductile or brittle depending on the inherent material properties.

Forging and Heat Treating Process Upgrades for a Wrought Railroad Wheel Manufacturing Facility

This paper describes a major capital project that was recently completed at a North American wrought railroad wheel manufacturing facility. The overall goals and concept of the project are outlined. Upgrades and improvements to band saws, the 10,000 ton forging press, rolling mill, and associated hydraulic systems, are described with emphasis on improvements in process speed. Installation of new wheel handling robots, which replaced an additional number of older, less robust wheel handling robots, is reviewed. Further, a new in-line wheel heat treating process, which provides for rim quenching and tempering of the wheel shortly after the forging and rolling process is completed, is described in detail. The new computer-controlled heat treating process features a rotary heating furnace to austenitize the wheels, several rim spray stations for quenching, a slot-in-the roof tempering furnace, controlled cooling operations, and automated Brinell testing. Important equipment maintenance concerns that were addressed are also reviewed. Finite element analysis (FEA) results for the new wheel heat treating process are discussed, along with other process considerations.

Review of Current Maintenance Practices Used on Commuter and Passenger Rail Cars

Commuter and passenger railroads invest large amounts of capital to purchase and maintain their rolling stock. Funding for maintenance is largely derived from operating budgets with some funds coming from other sources. Realizing maintenance is vital to the safety and operations of their rolling stock, railroads use maintenance methodologies found in other industries along with government regulations and in-house practices to determine the best maintenance practice for their fleet. By using Condition Based Maintenance, Life Cycle Maintenance, and Reliability Centered Maintenance, railroads have increased reliability by isolating unreliable parts and performing corrective actions when needed. This increases scheduled maintenance and reduces unscheduled maintenance. However, unscheduled maintenance still impacts operations and reliability for railroads. Rolling stock repair costs due to unscheduled maintenance are not captured or analyzed so further improvement can be made in this area.

In-Situ Test Measurement Techniques Within Railway Track Structures

Recent changes in national transportation needs have placed increased burden on railroad infrastructure. To meet the increased demand for efficient freight transport, the railroad industry has increased traffic volume and maximized axle loadings. Increased axle loads have forced railroads to reevaluate existing infrastructure to ensure their ability to accommodate the additional traffic loads. It is imperative to design and maintain tracks such that they can withstand high volume and increasing axle loads over an extended service life, considering the track structure is the most significant capital expense for railroad companies. It has been desirable for years to develop non-intrusive procedures to directly measure pressures and stresses at various levels and interfaces in the railroad track structure in order to optimize track designs and improve subsequent track performance. Methods for measuring both pressures and deflections have been presented in recent research focusing on assessing the performance of trackbeds with increased track modulus, primarily through the addition of asphalt underlayment. These studies involve instrumenting HMA trackbeds with earth pressure cells and displacement transducers to measure pressure levels and distributions within the track structure and rail deflections under moving trains. Additional test methodologies have been developed to include pressure readings at interfaces like the rail/tieplate interface and the tieplate/tie interface using very thin pressure sensitive Tekscan sensors. The Tekscan Measurement System uses a piezoelectric film sensor composed of a matrix-based array of force sensitive cells, similar to mini strain gauges, to obtain accurate pressure distributions between two surfaces in the track. The procedure appears applicable for a wide variety of specific track related measurements to include: 1) analyzing pressure distribution patterns at the rail base/tie plate/tie interfaces to minimize wear and eliminate pressure points, 2) validating and optimizing horizontal curve geometric design criteria relative to superelevation, 3) assessing crossing diamond, other special trackwork, and bridge approach impact pressures, and 4) evaluating the advantages/disadvantages of various types of tie plates, fastenings, and tie compositions with the objective of equalizing pressure distributions over the interface areas. Results of testing are presented in detail for test installations on CSX Transportation heavy tonnage mainlines and at the Transportation Technology Center (Pueblo) low track modulus heavy tonnage test track.

Post Test Review of a Single Car Test of Multi-Level Passenger Equipment

In support of the Federal Railroad Administration’s (FRA) Railroad Equipment Safety Program, a full-scale dynamic single car impact test of multi-level passenger equipment was conducted on October 2, 2007. The purpose of the test was to evaluate the crashworthiness performance of a multi-level car. The car struck the test barrier at 36.6 miles per hour (mph). Instrumentation on the car measured the deformations of critical structural elements; the vertical, lateral and longitudinal accelerations of the car body and trucks; and the suspension displacements. The structure of a multi-level car is different from that of a single level car or bi-level car. The underframe for single level cars and bi-level cars are straight. In a multi-level car, the underframe is at one level for the mezzanines, and at a lower level at the midsection. A transition structure, or gooseneck, connects the levels. Two passenger train incidents in the last few years have shown that multi-level cars deform in different modes from single level cars under dynamic loading conditions. In two separate collisions in Placentia and Glendale, CA, the gooseneck crushed. During the test, the most damage occurred in the draft sill. The gooseneck was beginning to hinge. The truck connections at both the leading and rear truck failed. Test results show that the multi-level car had a higher average force than the single level car. The secondary impact velocity is higher for the conventional multi-level car than in the conventional single level car. The multi-level car crushed approximately 2 feet during the test, 3 feet less than the single level car crushed.