Under the direction of the Association of American Railroads Vehicle/Track System Committee, a laboratory test qualification formula/specification for locomotive-based top-of-rail (TOR) friction modifier application system hardware has been developed. This document describes the development and demonstration process, including measurement of the vibration field environment and an initial test of one TOR component in a laboratory vibration and thermal test. Revenue service onboard locomotive vibration environment was measured continuously during two tests in late-2001 and early-2002. The first test measured responses in a train hauling auto parts while the second measured responses in a train hauling coal. Results of the first simulation suggest that many of the issues experienced from over the road field tests, such as clogging and variable output due to temperatures, were simulated and reproduced in the laboratory simulation.
The operating dynamic clearance envelope has historically been a sum of estimated dimensional tolerances, sometimes even called “black magic” [1]. These tolerances exist by design within the car and the track, as well as between the wheel flanges and the rail gage face. Field observations of operating clearance have augmented these estimates. Recently a review of such expectations was desired as related to wide and/or tall payloads, with particular respect to train speed and track roughness. This project reexamines the factors affecting car body envelopes, including track curvature and elevation, and car parameters such as length, center of gravity (CG), and side bearing type. A particular goal of this study was to gain a rough understanding of the behavior expected relative to wide loads in the speed range of 30–50 mph. Both static analyses and dynamic negotiation of typical revenue track have been predicted. The NUCARS® multibody simulation software has been used to examine the influence of operating speed and FRA track class on the dynamic envelope. A summary of results is presented along with a discussion of general guidelines and additional considerations.
Heavy-duty railcars carry greater than typical payloads by employing additional wheelsets to lessen wheel/rail contact stresses. Rather than the common 4-axle designs, these cars may have up to 16 axles supporting one deck. Traditionally, these car types have not performed as well as desired. As a response, designers have created depressed center body styles to lower the overall center-of-gravity (CG) height. Such designs lead to more complexity and expense. In this investigation, a heavy-duty 8-axle flatcar has been modeled, both with a flat carbody and a depressed body style. Simulations of harmonic roll perturbations were performed using various CG heights, track perturbation wavelengths and operating speeds. Results include comparisons of design versus performance trade-offs.
Traditionally, railroad track is installed so that rails that are welded together into strings longer than 400 feet experience no longitudinal thermal force at rail temperatures of 90 to 115 degrees °F. This rail temperature at which the thermal force is zero is commonly referred to as the rail’s neutral temperature. Rail at temperatures higher than the neutral temperature are in a state of compression, and in cooler temperatures are in tension. Except for the textbook case of a perfectly straight rail, these longitudinal forces must be reacted along the length of the rail via friction and the rail fasteners. A new device is designed to exploit changes in vibration of the rails within these fastenings and yield a non-destructive estimate of the installed neutral temperature. This paper will report on various on-track tests conducted at the Transportation Technology Center, Inc. (TTCI) in Pueblo, CO. This behavior was first noted empirically, without a background engineering mechanics outline. Similarly, this paper will follow the same evolution. After presentation of test data, engineering explanations will follow using theory and mechanical modeling.
At first glance, it seems appealing to suggest additional wheelsets under a given railcar type. From the track’s viewpoint, and in a simplistic analysis, trading a particular car’s four-axles for the use of six should allow half again more car weight. This paper will examine efforts to test this concept over the past century. Indeed, the railway marketplace has investigated the three-axle truck in both the freight and passenger car arenas multiple times over the past century. Except in heavy-duty flatcars, the record shows that each implementation has proven to be only temporary.
In general, three-axle freight trucks were developed for use with steam locomotive tenders in the early 20th century. These designs were then adapted to other car types over several decades, involving thousands of individual cars. Today, three-axle trucks are nearly extinct. This paper will address the history and status of three-axle freight trucks (or bogies) as used in North American railcar operations. Various past 20th-century applications will be discussed. International efforts will be reviewed as well. The very limited and remaining current usage of three-axle trucks is also discussed.
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