This study derives explicit analytical expressions for comparing contact patch dimensions and Kalker’s coefficients for a wheel moving on a roller and compares the results with a tangent track arrangement. The expressions suggest that full size roller rig will underpredict Kalker’s traction coefficients (creepage forces per unit creepage) by a factor that depends on the roller radius. Studying rail-wheel contact mechanics and dynamics in the field conditions can prove to be challenging due to the difficulties in adequately controlling the test conditions that can significantly affect the results, such as track irregularities, rail surface condition, etc. Roller rigs can prove to be a useful tool for such studies. One, however, must be careful when interpreting roller rig test results because of the differences in wheel-rail contact mechanics and dynamics between the track and the roller. The findings of this study, which are consistent with other studies’ conclusions, will allow researchers to relate results with field testing.

The interest for developing hybrid electric locomotives consisting of diesel engine, regenerative braking and battery storage is growing due to increased demand and cost of diesel oil, uncertainty in the steady supply of oil, and increased standards for reduced emissions. Electrical energy is lost from electric locomotives in the form of heat during dynamic braking. Routing this energy using a regenerative braking system into battery stacks can improve the overall efficiency as it can be used later to provide traction force during acceleration. Objective of this study is to perform a feasibility analysis of modes of regenerating the energy developed in the braking and storing the energy in an electric battery storage system for use in railroad locomotive applications. Various road locomotive duty cycles, charge and discharge rates, and environmental conditions have been considered as this is expected to substantially influence the optimal performance and safety of the battery as well as the potential fuel savings that could be realized using a hybrid design. A computational algorithm is developed to determine the amount of energy that can be obtained from regenerative breaking during the run of locomotive and can be stored back into the stack of battery, which can be coupled with diesel engine to save additional consumption of fuel. A combined electrochemical and thermal simulation analysis of several battery configurations using multiphysics simulation code has also been performed in order to understand the thermal management and cooling requirements of the batteries subject to the charging and discharging requirements of a locomotive engine. Such an analysis assists in addressing the key issue of operating the battery at an maximum efficiency level while dissipating any excessive heat generated during the operation, and maintaining the battery at a desired temperature range using a cooling scheme.

All railway vehicles running on a track have to overcome a resistance to motion. The resistance to motion is due to mechanical and electrical losses, as well as to aerodynamic drag. In order to evaluate this resistance, two different experimental methodologies can be used. The first one consists on a conventional method which takes into account the energy stored in rotating masses and the equivalent curving and grade resistance. The application of this method is based on a coasting test procedure done on a straight track without slope. The second methodology consists on the experimental acquisition of electrical signals in the traction power line and strain measurements at the traction links of the bogie-truck, with different speeds. The electrical signals allow obtaining the efficiencies of the equipments in the traction power line. Once the different efficiencies of the equipments in the traction power line are known, the power transmitted to each wheel can be determined and consequently the resistance to motion is calculated. This paper summarizes an experimental procedure based on both methodologies. The designed instrumentation uses voltage and current probes for the recording of electrical signals in the traction line, piezorresistive accelerometers in order to obtain the uncompensated and the longitudinal accelerations of the train, extensometric gauges in full bridge configuration for the acquisition of stresses at the traction links, and a gyroscope for the detection of curves along the track. Several tests have been done by means of the described methods in light rail vehicles. Also, the vehicles have been tested in order to evaluate the influence of the air conditioning and air intakes, the circulation in curves and the cooling of traction equipments in the resistance to motion. Through these experimental methods, a useful tool for the prediction and analysis of the resistance to motion is provided. Additionally, the results obtained by means of these methodologies permit to calculate the influence of different running conditions in the resistance to motion.

For mass transit rail systems employing a 3 rd rail to provide the electric traction power, the 3 rd rail support bracket must have the capability to withstand the dynamically applied service loads while also providing the necessary electric arc resistance. To meet the arc resistance requirement, fiberglass brackets have been steadily replacing metallic type brackets in fire retardation critical locations; therefore it was necessary to validate their structural performance when used in general service. To this end, a general stress analysis was performed on a representative support bracket to investigate potential stress profiles experienced under various static loading conditions. Historically, metallic brackets have not been susceptible to fatigue failures in service. In order to determine fatigue life characteristics of fiberglass brackets, service strains were collected and analyzed to compare the behavior of the fiberglass and metallic brackets and evaluate whether the service life of the new material is sufficient. Furthermore, the fatigue life of a support bracket is highly dependent on the operational conditions. Thus, a service fatigue life analysis was performed to determine the bracket’s response to the variation of operating environment parameters such as the 3 rd rail material and track location. From the analyses performed, it was concluded that the current design was not sufficient in replacing the metallic brackets. A possible redesign was then analyzed and it can be shown that a fiberglass material is suitable for the service application if the proper bracket design is incorporated.

Conventional stepped power transmission systems exhibit abundant energy dissipation, complicated handling and costly maintenance. On the other hand, continuously-variable power transmissions (CVTs), which are recently considered to be used in the industry, despite their high capabilities, face a number of drawbacks including limited torque transmission capacity, high-precision manufacturing and installation requirements, low cost effectiveness and relatively modest power transmission efficiencies. Therefore, innovative power transmission systems that intend to resolve or lessen one or more of these disadvantages are critical in power transmission from pinion to wheel in electric traction motors of both diesel and electric locomotives; especially when active and advanced control of traction effort and adhesion is of high importance and are going to be welcomed by rail industries. In this research, an innovative quasi-continuous power transmission (QCPT) system is introduced. In this system, a fully-automatic gear box including six pairs of engaging gears is considered where only one pair of gears is engaged in any operating moment. The main components of the QCPT are the input and output shafts each having six engaging gears, speed regulating sensor, electrical module and intelligent pins. The governing parameter in this design is output shaft rotating speed or output torque of the system. When high output torque is needed, the system automatically transfers power to lower gears, and in the need of high output speed, higher gears are assigned. The proposed system is simple and cost-effective, while having high reliability and efficiency.