Conventional freight railroad cars in North America and other parts of the world typically include a car body and two spaced apart trucks. The car body or car body under frame typically includes two spaced apart center plates that respectively rest on and are rotatably or swivelly received by bolster bowls of the two trucks. The trucks rollingly support the car body along railroad tracks or rails. Each truck typically has a three piece truck configuration that includes two spaced apart parallel side frames and a bolster. The side frames extend in the same direction as the tracks or rails, and the bolster extends transversely or laterally to the tracks or rails. The bolster extends laterally through and between and is supported by the two spaced apart side frames. Each side frame typically defines a center opening and pedestal jaw openings on each side of the center opening. Each end of each bolster is typically supported by a spring group positioned in the center opening of the side frame and supported by the lower portion of the side frame that defines the center opening.
Each truck also typically includes two axles that support the side frames, four wheels, and four roller bearing assemblies respectively mounted on the ends of the axles. The truck further typically includes four bearing adapters respectively positioned on each roller bearing assembly in the respective pedestal jaw opening below the downwardly facing wall of the side frame that defines the top of the pedestal jaw opening. The wheel sets of the truck are thus received in bearing adapters placed in leading and trailing pedestal jaws in the side frames, so that axles of the wheel sets are generally parallel to each other. The bearing adapters permit relatively slight angular displacement of the axles. The spring sets or groups permit the bolster to move somewhat with respect to the side frame, about longitudinal or horizontal, vertical, and transverse axes (and combinations thereof).
Directions and orientations herein refer to the normal orientation of a railroad car in use. Thus, unless the context clearly requires otherwise, the “longitudinal” axis or direction is substantially parallel to straight tracks or rails and in the direction of movement of the railroad car on the track or rails in either direction. The “transverse” or “lateral” axis or direction is in a horizontal direction substantially perpendicular to the longitudinal axis and the straight tracks or rails. “Vertical” is the up-and-down direction, and “horizontal” is a plane parallel to the tracks or rails including the transverse and longitudinal axes. A truck is considered “square” when its wheels are aligned on parallel rails and the axles are parallel to each other and perpendicular to the side frames. The “leading” side of the truck means the first side of a truck of a railroad car to encounter a turn; and the “trailing” side is opposite the leading side.
Existing trucks do not fully address the ever increasing and expected future demands for freight railroad car truck performance in the railroad industry. More specifically, while the various current known and commercially available three piece truck configurations meet current Association of American Railroads (“AAR”) specifications, enhanced specifications are being developed by the AAR and it is expected that the current three piece truck configurations may not meet these new AAR specifications. These AAR enhanced specifications set forth or codify these continuing and ongoing demands in the railroad industry for improved freight railroad car truck performance to: (a) reduce railroad car component wear and damage such as wheel wear and damage; (b) reduce rolling resistance; (c) reduce fuel consumption; (d) reduce the need for and thus cost of railroad track or rail repair (including reducing the cost of rail and tie maintenance); (e) reduce truck hunting and improve high speed stability (“HSS”) for both empty and loaded railroad cars; and (f) improve curving performance for both empty and loaded railroad cars.
Ideally, on straight tracks or straight rails, a three piece truck with parallel side frames and parallel wheel set axles perpendicular to the side frames (i.e., a perfectly “square” truck) rolls without inducing lateral or transverse forces between the wheel tread and the rail. However, at higher speeds, even minor imperfections or perturbations in the tracks or rails or in the equipment can lead to a condition known as “hunting” that refers to a yawing or oscillating lateral movement of the wheel sets along the tracks or rails that causes the railroad car to move side-to-side on the tracks or rails. More than minor imperfections or perturbations in the tracks or rails or in the railroad car equipment or components can lead to greater truck hunting even at lower speeds. Hunting tends to increase wheel wear and damage, increase fuel consumption, increase the need for railroad track or rail repair, and decrease HSS. In certain instances, hunting has also led to derailments, damage to the lading, and damage to the freight railroad cars.
Curved railroad tracks or rails pose a different set of challenges for the standard three-piece truck. When a railroad car truck encounters a curve or turn, the distance traversed by the wheels on the outside of the curve is greater than the distance traversed by wheels on the inside of the curve, resulting in lateral and longitudinal forces between the respective wheels and the tracks or rails. These wheel forces often cause the wheel set to turn in a direction opposing the curve or turn. On trucks with insufficient rigidity, this can result in a condition variously known as “warping,” “lozenging,” “parallelogramming,” and/or “unsquaring,” wherein the side frames remain parallel, but one side frame moves forward with respect to the other side frame. This condition is referred to herein as warping for brevity.
Another known issue relates to various known three piece railroad truck suspensions that have side frames with flat rectangular surfaces against which friction wedges are pressed to produce frictional (i.e., Coulomb) damping to control vertical bounces and other oscillatory modes. Normally, significant clearance exists between the side frame's column face and nearby surfaces of the bolster to enable assembly and proper relative motion during use. This clearance is undesirable in that it enables the truck assembly to become warped or change shape from the intended parallel and perpendicular arrangement (i.e., to undergo warping).
Such warping (alone or in combination with hunting) can cause increased wear on the tracks or rails and railroad car truck components or equipment. Such warping (alone or in combination with hunting) also tends to increase rolling resistance that increases railroad car fuel consumption, decreases railroad car efficiency, and increases railroad engine pollution.
Accordingly, there is a need to meet these ongoing demands in the railroad industry for improved freight railroad car truck performance that reduces, inhibits, and/or minimizes warping.