US20160001796A1

US20160001796A1 - Truck and sideframe therefor

Info

Publication number: US20160001796A1
Application number: US14/771,579
Authority: US
Inventors: Jamal Hematian
Original assignee: National Steel Car Ltd
Current assignee: National Steel Car Ltd
Priority date: 2013-03-01
Filing date: 2014-02-27
Publication date: 2016-01-07
Also published as: MX2015011379A; CA2902956A1; RU2015137412A; AU2014223270A1; WO2014131117A1; CN105324289A; BR112015021066A2

Abstract

A railroad car truck includes a bolster mounted cross-wise between a pair of sideframes, with the sideframes supported on wheelsets. The bolster and the sideframes are steel castings. The interface between the sideframes and the wheelsets may include self-steering apparatus. Friction dampers are mounted at the interface between the bolster and the sideframes. The friction dampers have non-metallic friction surfaces that bear against the sideframe columns. The sideframe columns may be of a width for single dampers contact; double-damper side-by-side contact; or double-dampers separated by a land contact. The sideframe column bearing surfaces are permanent, and may be formed as part of the sideframe castings. The sideframes do not have removable, replaceable wear plates. Where double dampers are used, the damper edges may have both primary and secondary damper wedge angles.

Description

FIELD OF THE INVENTION

This invention relates to the field of rail road car trucks, and to sideframes for railroad car trucks.

BACKGROUND OF THE INVENTION

In railroad rolling stock trucks are used to support railroad car bodies during motion along railroad tracks. Commonly, in North America a rail road freight car truck may have a pair of side frames, or side frame assemblies, that seat upon wheelsets, and a truck bolster that extends crosswise between, and is resiliently mounted to, the side frames. The bolster may typically have a centerplate bowl located at mid-span. The car body may include a centerplate that seats in the centerplate bowl in a relationship that permits a vertical load from the car body to be passed into the truck bolster while also permitting rotational pivoting of the bolster relative to the car body such that the truck can turn and the rail road car can negotiate curves in the track.
As a first approximation, at the simplest level of analysis, the truck bolster may be considered to be a simply supported beam. The car body and lading may be idealized as a vertically downward point load applied at the mid-span center of the beam, there being a pair of reactions, also idealized as point loads, provided by the main spring groups acting upwardly at the beam ends. The main spring groups have upper seats on the undersides of the ends of the bolster, and lower seats on the tension member of the side frames. Truck bolsters may tend to have the general form of a beam having a top flange, a bottom flange, and shear webs extending between the top and bottom flanges. The bending moment in the truck bolster may tend to be greatest at mid span. Consequently, the beam may tend to be deepest in section at the mid span location. While welded or riveted truck bolsters are known, truck bolsters tend commonly to be castings, most typically steel castings.
Sideframes may also be considered as simply supported beams. The vertical loading imposed by the associated bolster is, more or less, a point load applied at the center of the beam, through the medium of a main spring group. That load is reacted at the ends of the beam, where the sideframe pedestals seat on the wheel bearings. The wheelsets ultimately carry the loading into the rails and roadbed.
There are four dynamic interfaces along the load path from the railroad car body to the rail. The first interface is between the car body and the truck bolster. There is a second interface between the end of the bolster and the sideframe. There is a third load transfer interface between the sideframe and the wheel bearing. There is a fourth load transfer interface between the wheel and the rail. At all of these interfaces relative motion is permitted in respect of at least one degree of freedom, and motion in at least one other degree of freedom is constrained.
The bolster and the sideframes are major structural elements of the railroad car, and must be of a robustness commensurate with their roles in supporting a car body and lading that may weigh on the order of 280,000 lbs. The bolster and sideframes tend to be steel castings, and, by their size and robust nature, those castings tend to be correspondingly heavy. It may also be borne in mind that these elements, like elements of railroad freight car trucks generally, are unprotected from weather for many years, at extremes of temperature from −50 C to +60 C, with only modest, and relatively infrequent, maintenance.

SUMMARY OF THE INVENTION

In an aspect of the invention there is a sideframe for a railroad car truck, the sideframe having a sideframe column defining a bearing surface for engagement with at least one non-metallic damper, the sideframe column bearing surface being free of removable wear plates.
In a feature of that aspect of the invention, the sideframe is a unitary casting. In another feature, the sideframe bearing surface has a width defining a bearing accommodation for more than one damper. In still another feature, the sideframe defines a bottom seat for a main spring group of the railroad car truck, and the bearing surface is wider than the bottom seat. In a further feature, a laterally outermost extremity of the bearing surface defines a gib engagement abutment operable to restrain lateral motion of a bolster of the railroad car truck. In another feature, the bearing surface defines a yaw motion moment couple reaction surface. In another feature, the bearing surface has an as-cast finish. In an alternate feature, the bearing surface has a machined finish. In a further feature, the sideframe has two said sideframe columns, each of said sideframe columns having a respective bearing surface that is free of removable wear plates, and wherein said respective bearing surfaces are planar, parallel, spaced apart and facing each other. In still another feature, the sideframe has a long axis, and the bearing surface lies substantially in a plane, and the plane being normal to the long axis.
In another feature, there is a combination of the sideframe having any combination of the aforesaid aspect and features, as may be, and a set of friction dampers, the set of friction dampers including at least a first damper having a non-metallic working surface, the non-metallic working surface being in a mating sliding relationship with the bearing surface. In another feature, the sideframe includes a pedestal seat, and the pedestal seat has a self-steering apparatus mounted thereto. In still another feature, the combination includes any permutation including at least two of the following: (a) the sideframe being a unitary casting; (b) the sideframe bearing surface having a width defining a bearing accommodation for more than one damper; (c) the sideframe defining a bottom seat for a main spring group of the railroad car truck, and the bearing surface being wider than the bottom seat; (d) a laterally outermost extremity of the bearing surface defining a gib engagement abutment operable to restrain lateral motion of a bolster of the railroad car truck; (e) the bearing surface defining a yaw motion moment couple reaction surface; (f) the sideframe has a long axis, and the bearing surface lying substantially in a plane, the plane being normal to the long axis; (g) the combination including a set of friction dampers, the set of friction dampers including at least a first damper having a non-metallic working surface, the non-metallic working surface being in a mating sliding relationship with the bearing surface; and (h) the sideframe including a pedestal seat, and the pedestal seat having a self-steering apparatus mounted thereto.
In another aspect of the invention, there is a sideframe casting for a railroad car truck, the sideframe casting defining a sideframe window, and the sideframe casting including at least a first sideframe column bordering the window, the first sideframe column including a first bearing surface oriented to work against a non-metallic damper member.
In a feature of that aspect of the invention there is a combination comprising the sideframe casting and at least a first friction damper having a first non-metallic damping member, the first friction damper being positioned to work slidingly against the first bearing surface. In another feature, there is a second friction damper having a second non-metallic damping member, the second friction damper being positioned to work slidingly against the first bearing surface, the second friction damper being located sideways relative to the first friction damper; the first and second friction dampers being biased to work against the first bearing surface; and the second friction damper being biased independently of the first friction damper. In a still further feature, the first and second friction dampers are spaced apart by a distance greater than a D5 spring diameter. In another feature, the casting includes a second sideframe column having a respective second bearing surface.
In another aspect of the invention, there is a three-piece railroad freight car truck having a bolster mounted cross-wise between a pair of first and second sideframes, the truck having non-metallic friction dampers mounted to work between the bolster and each of the sideframes, and the sideframes being free of removable wear plates.
In still another aspect of the invention, there is a railroad car truck, the railroad car truck being a three-piece truck having a bolster mounted cross-wise between a pair of first and second sideframes, the bolster having a first end associated with the first sideframe, and a second end associated with the second sideframe, the truck having non-metallic friction dampers mounted to work between the bolster and each of the sideframes, each of the sideframes having bearing surfaces against which respective ones of the non-metallic friction dampers work, the bearing surfaces being permanent portions of each the sideframe.
In a feature of that aspect of the invention the first sideframe is a casting. The casting defines a sideframe window, the window being bounded fore-and-aft by first and second sideframe columns. The bearing surfaces being integrally cast portions of the sideframe columns. In another feature, the truck includes wheelsets, the sideframes are mounted on the wheelsets, and the truck includes self-steering apparatus. In another feature, the bearing surfaces are as-cast. In an alternate feature, the bearing surfaces are machined, or ground, surfaces.
In another aspect of the invention there is a sideframe casting for a railroad car truck. The sideframe has a lengthwise axis. The sideframe casting defines a sideframe window, the casting including first and second opposed sideframe columns bordering the window. The first and second sideframe columns have respective first and second friction damper bearing surfaces of the casting. The first and second friction damper bearing surfaces face toward each other. The first and second friction damper bearing surfaces are parallel to each other and normal to the lengthwise axis. Each of the first and second bearing surfaces is wider than two D5 springs placed side-by-side. In a feature of that aspect of the invention, the first and second friction damper bearing surfaces are machined surfaces of the sideframe columns. In an alternate feature, the first and second bearing surfaces of said sideframe columns are as-cast.
These and other aspects and features of the invention may be understood with reference to the description which follows, and with the aid of the illustrations of a number of examples.

BRIEF DESCRIPTION OF THE FIGURES

The subject matter may be understood with reference to the accompanying figures provided by way of illustration of an exemplary embodiment, or embodiments, incorporating principles and aspects of the present invention, and in which:

FIG. 1 shows an isometric view of an example of an embodiment of a railroad car truck according to an aspect of the present invention;

FIG. 2 a is a perspective view, taken predominantly from the side, of a sideframe of the railroad car truck of FIG. 1;

FIG. 2 b is a view similar to that of FIG. 2 a showing the location of springs and dampers as installed relative to the sideframe of FIG. 2 a;

FIG. 2 c is a view similar to that of FIG. 2 b additionally showing a bolster as mounted to the sideframe of FIG. 2 b;

FIG. 3 a shows a perspective view from one end and above of a bolster such as that of FIG. 2 c;

FIG. 3 b shows a perspective view of the bolster of FIG. 3 a partially from below;

FIG. 4 a is a front view of a friction damper for a truck such as that of FIG. 1 a;

FIG. 4 b shows a side view of the damper of FIG. 4 a;

FIG. 4 c shows a top view of the damper of FIG. 4 a;

FIG. 4 d shows a cross-sectional view on the centerline of the damper of FIG. 4 a taken on section ‘4 d-4 d’ of FIG. 4 a;

FIG. 4 e is a front view of an alternate friction damper to that of FIG. 4 a;

FIG. 4 f shows a side view of the damper of FIG. 4 e;

FIG. 4 g shows a top view of the damper of FIG. 4 e;

FIG. 4 h shows a cross-sectional view on the centerline of the damper of FIG. 4 e taken on section ‘4 h-4 h’ of FIG. 4 e;

FIG. 5 shows an exploded isometric view of a bearing adapter to pedestal seat assembly for use in the truck of FIG. 1;

FIG. 6 a shows an exploded detail perspective view of a portion of an alternate embodiment of truck to that of FIG. 1;

FIG. 6 b shows an exploded detail perspective view of a portion of a further alternative embodiment of truck to that of FIG. 1;

FIG. 6 c shows a view from above of a further alternate arrangement to that of FIG. 1; and

FIG. 6 d shows a schematic representation of the elements of the truck of FIG. 6 c to illustrate the co-operative operation of those elements.

DETAILED DESCRIPTION

The description that follows, and the embodiments described therein, are provided by way of illustration of an example, or examples, of particular embodiments of the principles and aspects of the present invention. These examples are provided for the purposes of explanation, and not of limitation, of those principles and of the invention. In the description, like parts are marked throughout the specification and the drawings with the same respective reference numerals. The drawings may be taken as being to scale unless otherwise noted.
In terms of general orientation and directional nomenclature, for the rail road car truck described herein, the longitudinal direction is defined as being coincident with the rolling direction of the rail road car, or rail road car unit, when located on tangent (that is, straight) track. In the case of a rail road car having a center sill, the longitudinal direction is parallel to the center sill, and parallel to the side sills, if any. Unless otherwise noted, vertical, or upward and downward, are terms that use top of rail, TOR, as a datum. In the context of the truck as a whole, the term lateral, or laterally outboard, refers to a distance or orientation relative to the longitudinal centerline of the railroad car, or car unit, or of the centerline of the centerplate bowl of the truck. The term “longitudinally inboard”, or “longitudinally outboard” is a distance taken relative to a mid-span lateral section of the truck. Pitching motion is angular motion of a railcar unit about a horizontal axis perpendicular to the longitudinal direction. Yawing is angular motion about a vertical axis. Roll is angular motion about the longitudinal axis.
The description herein discusses railroad freight car trucks. In North America the most common form of freight car truck is the three-piece truck. The “three pieces” refer to a pair of first and second sideframes and a cross-wise extending bolster that extends between, and is resiliently sprung on, the sideframes. The sideframes themselves extend lengthwise and have pedestals, or seats, at either end to accommodate the bearings of wheelsets upon which the truck moves in rolling motion along railroad tracks in the customary manner. The spring groups between the sideframes and the bolster define a primary suspension. A three-piece truck is distinguished from an H-Frame, or rigid truck, such as is more commonly found in passenger equipment, and such as may have both a primary and a secondary suspension, namely a sprung bolster, and independent spring suspension at each of the wheels. In the context of a truck side-frame, the lengthwise dimension or lengthwise direction is the long axis of the sideframe, which, in normal operation, is parallel to the rail. It may be thought of as the x-axis or x-direction of the sideframe. The cross-wise, or transverse, or lateral, direction or dimension of the truck is the through thickness direction, which may be thought of as the y-axis or y-direction of the side frame. The up-and-down, or vertical, direction may be thought of as the z-axis or z-direction.
In the context of a truck bolster, when the car is stationary on straight, level track, the long, or longitudinal axis of the truck bolster tends to be oriented cross-wise to the longitudinal axis of the truck or of the railroad car more generally. In this description, the lengthwise axis of the bolster may be considered the x-axis of the bolster. The transverse direction of the bolster may be considered the direction of the fore-and-aft thickness of the bolster, relative to the rolling direction of the truck, and may be designated the y-axis. The up and down direction, which may be parallel to the axis of the axis of the centerplate pin, when installed, may be considered the vertical or z-direction.
Reference may be made herein to various plate sizes or standards of the Association of American Railroads, the AAR. Unless otherwise specified, those standards are to be interpreted as they were at the date of filing of this application, or if priority is claimed, then as of the earliest date of priority of any application in which the standard is identified, those standards being understood to read the same as they did on Feb. 1, 2013. Several AAR standard truck sizes are listed at page 711 in the 1997 Car & Locomotive Cyclopedia. As indicated, for a single unit rail car having two trucks, a “40 Ton” truck rating corresponds to a maximum gross car weight on rail (GRL) of 142,000 lbs. Similarly, “50 Ton” corresponds to 177,000 lbs., “70 Ton” corresponds to 220,000 lbs., “100 Ton” corresponds to 263,000 lbs., and “125 Ton” corresponds to 315,000 lbs. In each case the load limit per truck is then half the maximum gross car weight on rail. Two other types of truck are the “110 Ton” truck for railcars having a 286,000 lbs. GRL and the “70 Ton Special” low profile truck sometimes used for auto rack cars. Given that the truck described herein may tend to have both longitudinal and transverse axes of symmetry, a description of one half of an assembly may generally also be intended to describe the other half as well, allowing for differences between right hand and left hand parts.
This description refers, in part, to friction dampers, and damper seats for rail road car trucks, and to multiple friction damper systems. There are several types of damper arrangements, some being shown at pp. 715-716 of the 1997 Car and Locomotive Cyclopedia, those pages being incorporated herein by reference. Each of the arrangements of dampers shown at pp. 715 to 716 of the 1997 Car and Locomotive Cyclopedia can be modified to employ a four cornered, double damper arrangement of inner and outer dampers. In terms of general nomenclature, damper wedges tend to be mounted within an angled “bolster pocket” formed in an end of the truck bolster. In cross-section, each wedge may then have a generally triangular shape, one side of the triangle being, or having, a bearing face, a second side which might be termed the bottom, or base, forming a spring seat, and the third side being a sloped side or hypotenuse between the other two sides. The first side may tend to have a substantially planar bearing face for vertical sliding engagement against an opposed bearing face of one of the sideframe columns. The second face may not be a face, as such, but rather may have the form of a socket for receiving the upper end of one of the springs of a spring group. Although the third face, or hypotenuse, may appear to be generally planar, in some embodiments it may tend to have a slight crown, having a radius of curvature of perhaps 60″. The crown may extend along the slope and may also extend across the slope. The end faces of the wedges may be generally flat, and may have a coating, surface treatment, shim, or low friction pad to give a smooth sliding engagement with the sides of the bolster pocket, or with the adjacent side of another independently slidable damper wedge, as may be.
During railcar operation, the sideframe may tend to rotate, or pivot, through a small range of angular deflection about the end of the truck bolster (i.e., about the y-axis) to yield wheel load equalisation. The slight crown on the slope face of the damper may tend to accommodate this pivoting motion by allowing the damper to rock somewhat relative to the generally inclined face of the bolster pocket while the planar bearing face remains in planar contact with the wear plate of the sideframe column. Although, in some embodiments the slope face may have a slight crown, for the purposes of this description it will be described as the slope face or as the hypotenuse, and will be considered to be a substantially flat face as a general approximation.
In the terminology herein, wedges may have a primary angle α, being the included angle between (a) the sloped damper pocket face mounted to the truck bolster, and (b) the side frame column face, as seen looking from the end of the bolster toward the truck center. In some embodiments, a secondary angle β may be defined in the plane of angle α, namely a plane perpendicular to the vertical longitudinal plane of the (undeflected) side frame, tilted from the vertical at the primary angle. That is, this plane is parallel to the (undeflected) long axis of the truck bolster, and taken as if sighting along the back side (hypotenuse) of the damper. The secondary angle β is defined as the lateral rake angle seen when looking at the damper parallel to the plane of angle α. As the suspension works in response to track perturbations, the wedge forces acting on the secondary angle β may tend to urge the damper either inboard or outboard according to the angle chosen.
FIG. 1 a shows an example of a rail road car truck 20 that is intended to be generically representative of a wide range of three-piece freight car trucks. Truck 20 has a truck bolster 24 and first and second side frames 26. While truck 20 may be suitable for general purpose use, it may be optimized for carrying relatively low density, high value lading, such as automobiles or consumer products, for example, or for carrying denser semi-finished industrial goods, such as might be carried in rail road freight cars for transporting rolls of paper, or for carrying dense commodity materials be they coal, metallic ores, grain, potash, steel coils or other lading. Truck 20 is generally symmetrical about both its longitudinal and transverse, or lateral, centreline axes. Where reference is made to a sideframe, it will be understood that the truck has first and second sideframes, first and second spring groups, and so on.
Description of Sideframes
Side frames 26 may be metal castings, and may typically be steel castings. Each side frame 26 has a generally rectangular side frame window 28 that accommodates one of the ends 30 of the bolster 24. The upper boundary of window 28 is defined by the side frame arch, or compression member identified as top chord member 32, and the bottom of window 28 is defined by a tension member identified as bottom chord 34. The fore and aft vertical sides of window 28 are defined by a pair of first and second side frame columns 36. The ends of the tension member sweep up to meet the compression member. At each of the swept-up ends of side frame 26 there are side frame pedestal fittings, or pedestal seats 38. Each fitting 38 accommodates an upper fitting, which may be a rocker or a seat. This upper fitting, whichever it may be, is indicated generically as 40. Fitting 40 engages a mating fitting 42 of the upper surface of a bearing adapter 44. Bearing adapter 44 engages a bearing 46 mounted on one of the ends of one of the axles 48 of the truck adjacent to one of the wheels 50 of one of the wheelsets. A fitting 40 is located in each of the fore and aft pedestal fittings 38, the fittings 40 being longitudinally aligned.
The relationship of the mating fittings 40 and 42 is described at greater length below. The relationship of these fittings determines part of the overall relationship between an end of one of the axles of one of the wheelsets and the sideframe pedestal. That is, in determining the dynamic response of the truck suspension, the degrees of freedom of the mounting of the axle end in the sideframe pedestal involve a dynamic interface across an assembly of parts, such as may be termed a wheelset to sideframe interface assembly, that may include the bearing, the bearing adapter, an elastomeric pad, if used, a rocker, if used, and the pedestal seat mounted in the sideframe pedestal roof. To the extent bearing 46 has a single degree of freedom, namely rotation about the wheelshaft axis, analysis can be focused on the bearing to pedestal seat interface assembly, or on the bearing adapter to pedestal seat interface assembly, however termed. For the purposes of this description, items 40 and 42 are intended generically to represent the combination of features of a bearing adapter and pedestal seat assembly defining the interface between the roof of the sideframe pedestal and the bearing adapter, and the six degrees of freedom of motion at that interface, namely vertical, longitudinal and transverse translation (i.e., translation in the z, x, and y directions) and pitching, rolling, and yawing (i.e., rotational motion about the y, x, and z axes respectively) in response to dynamic inputs.
The bottom chord or tension member 34 of sideframe 26 may have a basket plate, or lower spring seat 52 rigidly mounted thereto. The lower ends of the springs of the entire spring group 54 seat in lower spring seat 52. Lower spring seat 52 may be laid out as a tray with an upturned rectangular peripheral lip. Spring seat 52 may have retainers 54 for engaging the springs of a spring set, or spring group, 56, whether internal bosses, or the peripheral lip, for discouraging the escape of the bottom ends of the springs. The spring group 56, is captured between the distal end 30 of bolster 24 and spring seat 52, being placed under compression by the weight of the rail car body and the loading that bears upon bolster 24 from the car body above. Although truck 20 employs a spring group in a 3×3 arrangement, this is intended to be generic, and to represent a range of variations. They may represent 3×5, 2×4, 3:2:3 or 2:3:2 arrangement, or some other, and may include a hydraulic snubber, or such other arrangement of springs may be appropriate for the given service for the railcar for which the truck is intended. Although truck 20 may be free of unsprung lateral cross-bracing, whether in the nature of a transom or lateral rods, in the event that truck 20 is taken to represent a “swing motion” truck with a transom or other cross bracing, the lower rocker platform of spring seat 52 may be mounted on a rocker, to permit lateral rocking relative to sideframe 26.
Sideframe columns 36 are shown in FIG. 2 a. It is known in earlier trucks to mount sacrificial wear plate members to sideframe columns. Wear plates are most typically secured by mechanical fasteners. As the name may suggest, wear plates may tend to wear. When worn, the wear plates are typically removed and replaced as may be required.
In the embodiment shown, sideframe 26 may be a unitary casting. In that embodiment, sideframe 26 has sideframe columns 36 that do not have removable wear plate members. That is, sideframe columns 36 are free of removable wear plates. Rather, sideframe column 36 has, or defines, a bearing surface 92 (i.e., a surface against which the friction damper wedges of the bolster bear in use) for engagement with the non-metallic damper, or dampers, such as damper wedges 64, 66, 63, 166, 168, as may be, that seat in the opposed bolster pocket, or bolster pockets, such as pockets 72, or as may be, of bolster 24, 162, for example. In one embodiment, bearing surface 92 is as-cast. In another embodiment, the casting may be a near-net-finish surface, and may be machined to a final flat surface. Machining may include grinding.
In the illustration of FIGS. 2 a, 2 b, and 2 c, bearing surface 92 can be seen to be wider than one damper, and is shown as being wide enough to accommodate, and provides an accommodation for, a pair of dampers, namely dampers 64, 66 located side-by-side laterally inboard and outboard, and spaced apart from each other. In the embodiment illustrated, the lateral spacing of dampers 64, 66 accommodates the width of an entire row of coil springs, namely the middle row of spring group 56. Bearing surface 92 also accommodates lateral and vertical relative motion of damper 64, 66 in their operating envelope as determined vertically by the range of spring travel from bottom out (i.e., solid compression of the springs) to full extension at maximum upward travel of bolster 24.
As may be noted, in the lateral, or y-direction, bearing surface 92 may be as wide as, or wider than, the width of the bottom seat 52 of the main spring group. In the embodiment illustrated, the laterally outermost edge or extremity of bearing surface 92 defines a gib engagement abutment that interacts with gib 88, and that is thereby operable to restrain lateral motion of bolster 24. As can be understood, particularly from the schematic presentation of FIG. 6 d, the width of bearing surface 92 to over-span the lateral spacing of dampers 64, 66 implies that bearing surface 92 defines a yaw motion moment couple reaction surface.
As may also be noted, side frame 24 has a long axis, running in the x-direction, or vertical plane in an x-z plane. Bearing surface 92 lies substantially in a plane, it being a y-z plane as illustrated, that y-z plane being normal to the long axis of side frame 24. As may be understood, it follows geometrically that bearing surface 92 of one sideframe column 36 may accordingly lie in a y-z plane that is parallel to, and spaced away from, bearing surface 92 of the opposed sideframe column 36. As installed, as shown in FIG. 2 b, for example, the set of friction dampers, for example wedges 64, 66, such as may have a non-metallic working surface, seat in the damper pockets. Their non-metallic working surfaces are then in mating sliding relationship with bearing surface 92.
The various features described may be in combination. The combination may include any permutation including at least two of (a) the sideframe being a unitary casting; (b) the sideframe bearing surface having a width defining a bearing accommodation for more than one damper; (c) the sideframe defining a bottom seat for a main spring group of the railroad car truck, and the bearing surface is wider than the bottom seat; (d) a laterally outermost extremity of the bearing surface defines a gib engagement abutment operable to restrain lateral motion of a bolster of the railroad car truck; (e) the bearing surface defines a yaw motion moment couple reaction surface; (f) the sideframe has a long axis, and the bearing surface lies substantially in a plane, that plane being normal to the long axis; (g) the combination includes a set of friction dampers, that set of friction dampers including at least a first damper having a non-metallic working surface, the non-metallic working surface being in a mating sliding relationship with the bearing surface; and (h) the sideframe includes a pedestal seat, and the pedestal seat has a self-steering apparatus mounted thereto.
The embodiment of FIGS. 2 a, 2 b and 2 c also illustrates a sideframe casting for a railroad car truck. The sideframe casting defining a sideframe window 28. The sideframe casting includes first and second spaced-apart sideframe columns 36 bordering window 28. The first sideframe column 36 has a first bearing surface 92 oriented to work against a non-metallic damper member, such as wedge 64, 66 or 63. As assembled in FIG. 2 c, there is a combination that includes the cast sideframe 26 and at least a first friction damper having a first non-metallic damping member, or surface, the friction damper, or dampers, being positioned to work slidingly against bearing surface 92. That combination may further comprising a second friction damper (e.g., damper 66, or a second of dampers 63) having a second non-metallic damping member, friction damper wedge 66 being positioned to work slidingly against bearing surface 92. The second friction damper wedge, 66, is located sideways relative to the first friction damper 64. The first and second friction dampers are biased, by their springs, 76, 78, to work against bearing surface 92. As understood from the independent presence of springs 76 and 78, the second friction damper wedge 66 is biased independently of the first friction damper wedge 64. Given the width of the intervening land 70, it can be understood that the first and second friction dampers are spaced apart by a distance greater than an AAR D5 spring diameter.
The embodiment of FIGS. 2 a, 2 b, and 2 c thus shows a three-piece railroad freight car truck having a bolster mounted cross-wise between a pair of first and second sideframes, the truck having non-metallic friction dampers mounted to work between the bolster and each of the sideframes, and in which the sideframes are free of removable wear plates.
Expressed differently, the embodiment of FIGS. 2 a, 2 b and 2 c shows a railroad car truck 20. Truck 20 is a three-piece truck having a bolster 24 mounted cross-wise between a pair of first and second sideframes 26. Bolster 26 has a first end associated with the first sideframe, and a second end associated with the second sideframe. Truck 20 has non-metallic friction dampers, e.g., be it damper wedges 64, 66, 63, etc., mounted to work between bolster 24 and each of sideframes 26. Each sideframe 26 has bearing surfaces 92 against which respective ones of the non-metallic friction dampers work. The bearing surfaces are permanent portions of each sideframe 26. In railroad car truck 20 the first sideframe 26 may be a casting. The casting defines a sideframe window 28. The window is bounded fore-and-aft by the first and second sideframe columns. The bearing surfaces 92 are integrally cast portions of sideframe columns 36. Truck 20 includes wheelsets 48, 50. Sideframes 26 are mounted on said wheelsets. Truck 20 may include self-steering apparatus.
FIGS. 2 a, 2 b, and 2 c show a casting in the form of sideframe 26 for railroad car truck 20. Sideframe 26 has a lengthwise axis. The casting of sideframe 26 defines a sideframe window 28. The casting includes first and second opposed sideframe columns 36 bordering window 28. Sideframe columns 36 have respective first and second friction damper bearing surfaces 92. The first and second friction damper bearing surfaces 92 of the respective sideframe columns 36 face toward each other. The first and second friction damper bearing surfaces 92 may be parallel to each other, and normal to the lengthwise axis of sideframe 26. Each of the first and second bearing surfaces 92 is wider than two D5 springs placed side-by-side.
Description of Bolster
Bolster 24 has the form of a beam that is deep in the middle, and shallow at its ends 30. Other than minor ancillary fittings, bolster 24 is symmetrical about the central longitudinal vertical plane of the bolster (i.e., cross-wise relative to the truck generally) and symmetrical about the vertical mid-span section of the bolster (i.e., the longitudinal plane of symmetry of the truck generally, coinciding with the railcar longitudinal center line). Bolster 24 is typically a monolithic steel casting to which side bearings, brake fittings, and so on are thereafter mounted.
FIGS. 3 a and 3 b show perspective views of bolster 24. Ends 30 define, on their undersides, upper spring seat 58 for the associated main spring group 56. Adjacent to upper spring seat 58, in the fore-and-aft direction of rolling motion of truck 20, bolster 24 has accommodations for doubled dampers. That is, it has a pair of first and second laterally spaced apart, inboard and outboard, bolster pockets 60, 62 on each face (i.e., for a total of 8 bolster pockets per bolster, 4 at each end). Pockets 60, 62 define accommodations for receiving damper wedges 64, 66. Pocket 60 is laterally inboard of pocket 62 relative to side frame 26 of truck 20 more generally. Bolster pockets 60, 62 accommodate fore and aft pairs of first and second, laterally inboard and laterally outboard friction damper wedges 64, 66 respectively. Bolster 24 includes a middle land 70 between pockets 60, 62, against which middle spring 68 may work. Middle land 70 is such as might be found in a spring group that is three (or more) coils wide (i.e., in the y-direction). The top ends of the central row of springs, 80, seat under the main central portion 82 of end 30 of bolster 24.
Each bolster pocket 60, 62 has an inclined face, or damper seat 72, that mates with a similarly inclined hypotenuse face 74 of the damper wedge, 64, 66. Wedge 64 sits over a first, inboard corner spring 76. Wedge 66 sits over a second, outboard corner spring 78. Thus wedges 64 and 66 are driven independently of each other. The compressive load in each of springs 76, 78 biases the respective angled faces 74 of wedges 64, 66 to ride against the corresponding angled faces of respective seats 72, which, in turn, imparts a horizontal bias of wedges 64, 66 against the sideframe column bearing surfaces 92. It may be understood that each corner spring 76 or 78 may be a single spring, or may include an outer spring and a nested inner spring.
Bolster 24 has inboard and outboard gibs 86, 88 respectively, that bound the lateral motion, i.e., sideways translation, of bolster 24 relative to sideframe columns 36. This motion allowance may be in the range of +/−1⅛ to 1¾ inches, and may be in the range of 1 3/16 to 1 9/16 inches, and can be set, for example, at 1½ inches or 1¼ inches of lateral travel to either side of a neutral, or centered, position when the sideframe is undeflected.
In the various embodiments of trucks herein, the gibs may be shown mounted to the bolster inboard and outboard of the bearing surfaces 92 on the side frame columns 36. In the embodiments shown herein, the clearance between the gibs and the side frames is desirably sufficient to permit a motion allowance of at least ¾ inches of lateral travel of the truck bolster relative to the wheels to either side of neutral. In some embodiments, it permits greater than 1 inch of travel to either side of neutral, and may permit travel in the range of about 1 or 1⅛ inches to about 1⅝ or 1 9/16 inches to either side of neutral.
Dampers 64, 66 may be arranged in first and second damper groups, mounted respectively at the first and second ends of bolster 24. Each damper group may include 4 dampers. Each of those dampers may be sprung independently of any other, and may be arranged in a four-cornered arrangement, namely with two dampers facing each sideframe, one being outboard of the other, each damper being individually sprung by one or another of the springs in spring group 56. The static compression of the springs under the weight of the car body (and lading) tends to act as a spring loading, or pre-loading, to bias the damper wedge, be it 64 or 66, to act along the sloped face 72 of the bolster pocket to force the friction surface against the mating, co-operating, opposed friction bearing surface of the facing sideframe column.
In operation, bolster 24 is able to pivot about the vertical, or z-axis, with respect to the body of the railroad car, or car unit, more generally, while the vertical load of the railroad car is carried into the bolster through the center plate bowl 74 and the side bearings. Bolster 24 can move up and down in the side frame windows 28 on the spring groups 56 in response to vertical perturbations. The vertical motion may tend to carry along friction dampers 64, 66 seated in the bolster pockets 60, 62 of bolster 24, causing friction dampers 64, 66 to ride against the side frame columns 36. Friction damping is provided when the vertical sliding faces 90 of the friction damper wedges 64, 66 ride up and down on the respective friction bearing surfaces 92 of the inwardly facing surfaces of sideframe columns 36. In this way the kinetic energy of the motion is, in some measure, converted through friction to heat. This friction may tend to damp out the motion of bolster 24 relative to sideframes 26.
Bolster 24 may be displaced laterally relative to the side frames in response to lateral perturbations, subject to the range of travel permitted by the bolster gibs 86, 88. When a lateral perturbation is passed to wheels 50 by the rails, rigid axles 48 may tend to cause both sideframes 26 to deflect in the same direction (the maximum extent of this excursion being limited by the flanges of the wheels). The reaction of sideframes 26 is to swing, like pendula, on the upper rockers defined by the relationship between fittings 40 and 42. The spring groups 56 and the sideways swinging, or rocking motion of side frames 26 may tend to resist this lateral motion. That is, the weight of the pendulum and the reactive force arising from the twisting of the springs may then tend to urge the sideframes back to their initial position. The tendency to oscillate harmonically laterally due to track perturbations may tend to be damped out by the friction of the dampers on the wear plates 92, and may tend to restore bolster 24 to an equilibrium position with the amplitude of the lateral rocking or swinging motion decreasing as the dampers work against the side frame column wear plates. When side-to-side leaning or rocking motion of the car body occurs, loads may be carried into truck bolster 24 at the side bearings mounted to the upper surface of bolster 24 from the engaging side bearing surfaces of the body bolster of the car body.
While bolster 24 may be used in trucks of various sizes and capacities, it may be that it may be employed in a truck of an AAR rated capacity of at least 70 Tons. Alternatively, it may be employed in trucks of at least 100 Tons rating. In the further alternative, it may be used in trucks having an AAR rating of either 110 Tons or 125 Tons. Expressed somewhat differently, bolster 24 may be rated to carry a central vertical load of at least 115,000 lbs. In another embodiment, bolster 24 may be rated to carry a vertical load of at least 130,000 lbs. In still another embodiment, bolster 24 may be rated to carry a load of at least 145,000 lbs.
As compared to a bolster with single dampers, such as may be mounted on the sideframe centerline as shown in FIG. 6 a, for example, the use of doubled dampers such as spaced apart pairs of dampers 64, 68 may tend to give a larger moment arm, as indicated by dimension “2M” in FIG. 6 b, for resisting parallelogram deformation of truck 20 more generally, for allowing the truck to flex resiliently, and then resiliently urging the truck back toward its neutral, or central, lowest energy condition at zero lateral displacement i.e., at its central equilibrium. Use of doubled dampers may yield a greater restorative “squaring” force to return the truck to a square orientation than for a single damper alone with the restorative bias, namely the squaring force, increasing with increasing deflection. That is, in parallelogram deformation, or lozenging, the differential compression of one diagonal pair of springs (e.g., inboard spring 76 and the diagonally opposite outboard spring 78 may be more pronouncedly compressed) relative to the other diagonal pair of springs tends to yield a restorative moment couple acting on the sideframe bearing plates. This moment couple tends to rotate the sideframe in a direction to square the truck, (that is, in a position in which the bolster is perpendicular, or “square”, to the sideframes). As such, the truck is able to flex, and when it flexes the dampers co-operate in acting as biased members working between the bolster and the side frames to resist parallelogram, or lozenging, deformation of the side frame relative to the truck bolster and to urge the truck back to the non-deflected position.
Whether two, three, or more coils wide, and whether employing a central land or no central land, bolster pockets may have both primary and secondary angles as illustrated in WO 2005/005219, whether they have or do not have wear inserts. Wear inserts may be mounted in pockets 60, 62 along the angled wedge face.
Damper Wedges
Referring to FIGS. 4 a-4 d, or the alternate embodiment of FIGS. 4 e-4 h, a damper wedge 64 or 66 is shown (or 63 in FIGS. 4 e-4 h), such as may be used in truck 20, or in any of the other double damper trucks described herein, such as may have mating bolster pockets. Damper wedges 64, 66 (and 63) in various embodiments may have both primary and secondary angles, and therefore be either left-handed or right-handed.
Wedge 64 has a body 120 (or 121 in FIGS. 4 e-4 h) that may be made by casting or by another suitable process. Body 120 may be made of steel or cast iron, and may be substantially hollow. Body 120 has a first, substantially planar platen portion 124 having a first face, namely vertical sliding face 90, for placement in a generally vertical orientation in opposition to the sideframe column bearing surface 92. Platen portion 124 has a non-metallic surface or lining formed thereon or mounted thereto, indicated as member 126. Member 126 may be a material, like a brake shoe lining, having specific friction properties when used in conjunction with material (e.g., cast steel) of the sideframe column bearing surface. For example, member 126 may be formed of a brake lining material, and the column bearing surface may be formed from an high-hardness steel. Such materials are understood to be available from Railway Friction Products Corporation of Laurinburg, N.C.
Body 120 may include a base portion 128 that may extend rearwardly from and generally perpendicularly to, platen portion 124. Base portion 128 may have a socket or relief 122 formed therein in a manner to form, roughly, the negative impression of an end of a spring coil, such as may receive a top end of a coil of a spring of a spring group, such as spring 76 or 78. Base portion 128 may join platen portion 124 at an intermediate height, such that a lower portion of platen portion 124 may depend downwardly therebeyond in the manner of a skirt. That skirt portion may include lugs or a corner, or wrap around portion formed to seat around the upper end portion of the respective spring.
Body 120 may also include a diagonal member in the nature of a sloped member 134. Sloped member 134 may have a first, or lower end extending from the distal end of base portion 128 and running upwardly and forwardly toward a junction with platen portion 124. In the embodiment of FIGS. 4 a-4 d, sloped member 134 may also have a socket or seat in the nature of a relief or rebate 136 formed therein for receiving a sliding face member 138 for engagement with the wear surface of the bolster pocket. Sloped member 134 (and face member 138) are inclined at a primary angle α. Sliding face member 138 may be an element of chosen, possibly relatively low, friction properties (when engaged with the bolster pocket wear plate), such as may include desired values of coefficients of static and dynamic friction. In one embodiment the coefficients of static and dynamic friction may be substantially equal, may be about 0.2 (+/−20%, or, more narrowly +/−10%), and may be substantially free of stick-slip behaviour.
In the embodiment of FIGS. 4 e-4 h sloped member 135 does not have an insert, such as member 138, but rather presents a metal face 139 to the mating inclined face of the bolster pocket. Metal face 139 may be slightly crowned, as seen in the cross-section of FIG. 4 e, (i.e., it is formed on a large radius of curvature arc) such as may accommodate relative pitching movement of the sideframes relative to the bolster.
For the embodiments discussed herein, primary angle α may tend to lie in the range of 35-55 degrees, possibly about 40-50 degrees. This same angle α is matched by the facing surface or seat 72 of the bolster pocket, be it 60 or 62. Wedges 64, 66 may also have a secondary angle β defining the inboard, (or outboard), rake of the sloped surface 134 of wedge 64 (or 66). The true rake angle can be seen by sighting along the plane of the sloped face and measuring the angle between the sloped face and the planar outboard face. The rake angle is the complement of the angle so measured. Where used, the rake angle may tend to be greater than 5 degrees, may lie in the range of 5 to 20 degrees, and is preferably about 10 to 15 degrees. A modest rake angle may be desirable.
When the truck suspension works in response to track perturbations, the damper wedges may tend to work in their pockets. The rake angles yield a component of force tending to bias the outboard face of outboard wedge 66 outboard against the opposing outboard face of bolster pocket 62. Similarly, the inboard face of wedge 64 may tend to be biased toward the inboard planar face of inboard bolster pocket 60. These inboard and outboard faces of the bolster pockets may be lined with a low friction surface pad. The left hand and right hand biases of the wedges may tend to keep them apart to yield the full moment arm distance intended, and, by keeping them against the planar facing walls, may tend to discourage twisting of the dampers in their respective pockets.
The foregoing assumes the context of trucks 20, having a spring group of three rows facing the sideframe columns. The restorative moment couple of a 4-cornered damper layout can also be explained in the context of a truck having a 2 row spring group arrangement facing the dampers, as in truck 120 of FIGS. 6 c and 6 d. For the purposes of conceptual visualization, the normal force on the friction face of any of the dampers can be taken as a pressure field whose effect can be approximated by a point load acting at the centroid of the pressure field and whose magnitude is equal to the integrated value of the pressure field over its area. The center of this distributed force, acting on the inboard friction face of wedge 64 against column 36 can be thought of as a point load offset transversely relative to the diagonally outboard friction face of wedge 66 against the opposite column 36 by a distance that is nominally twice dimension ‘L’ shown in the conceptual sketch of FIG. 6 d. In the example this distance, 2L, is about one full diameter of the large spring coils in the spring set. The restoring moment in such a case would be, conceptually, M_R=[(F₁+F₃)−(F₂+F₄)]L. This may be expressed M_R=4k_cTan(ε)Tan(θ)L, where θ is the primary angle of the damper (generally illustrated as α herein), and k_cis the vertical spring constant of the coil upon which the damper sits and is biased.
In the various arrangements of spring groups 2×4, 3×3, 3:2:3 or 3×5 group, dampers may be mounted over each of four corner positions. The portion of spring force acting under the damper wedges may be in the 25-50% range for springs of equal stiffness. If not of equal stiffness, the portion of spring force acting under the dampers may be in the range of perhaps 20% to 35%. The coil groups can be of unequal stiffness if inner coils are used in some springs and not in others, or if springs of differing spring constant are used.
Bearing surface 92 (FIG. 2 a) of sideframe 26 of truck 20 is significantly wider than the through-thickness of the sideframes more generally, as measured, for example, at the pedestals, and may tend to be wider than has been conventionally common. This additional width corresponds to the additional overall damper span width measured fully across the damper pairs, plus lateral travel as noted above, typically allowing 1½ (+/−) inches of lateral travel of the bolster relative to the sideframe to either side of the undeflected central position. That is, rather than having the width of one coil, plus allowance for travel, bearing surface 92 may have the width of three coils, plus allowance to accommodate 1½ (+/−) inches of travel to either side for a total, double amplitude travel of 3″ (+/−).
In the various truck embodiments described herein, there is a friction damping interface between the bolster and the sideframes. The bearing face of the motion calming, friction damping element may be obtained by treating the surface to yield desired co-efficients of static and dynamic friction whether by application of a surface coating, an insert, a pad, a brake shoe or brake lining, or other treatment. Such a shoe or lining may have a polymer based or composite matrix, loaded with a mixture of metal or other particles of materials to yield a specified friction performance. Shoes and linings may be obtained from clutch and brake lining suppliers. One firm that may be able to provide such materials is Railway Friction Products of Laurinburg N.C.; another may be Quadrant EPP USA Inc., of Reading Pa. In one embodiment, the material may be the same as that employed by the Standard Car Truck Company in the “Barber Twin Guard” (t.m.) damper wedge with polymer covers.
The vertical face of friction the damper wedges may have a bearing surface having a co-efficient of static friction, μ_s, and a co-efficient of dynamic or kinetic friction, μ_k, that may tend to exhibit little or no “stick-slip” behaviour when operating against the bearing surface of the sideframe column. In one embodiment, the coefficients of friction are within 10% of each other. In another embodiment the coefficients of friction are substantially equal and may be substantially free of stick-slip behaviour. The coefficients may vary with environmental conditions. For the purposes of this description, the friction coefficients will be taken as being considered on a dry day condition at 70 F. In one embodiment, when dry, the coefficients of friction may be in the range of 0.10 to 0.45, may be in the narrower range of 0.15 to 0.35, and may be about 0.30. The bonded pad may be a polymeric pad or coating. A low friction, or controlled friction pad or lining or coating 126 may also be employed on the sloped surface of the damper. In one embodiment that coating or lining or pad 126 may have coefficients of static and dynamic friction that are within 20%, or, more narrowly, 10% of each other. In another embodiment, the coefficients of static and dynamic friction are substantially equal. The co-efficient of dynamic friction may be in the range of 0.10 to 0.30, and may be about 0.20.
Truck performance may vary with the friction characteristics of the damper surfaces. Dampers have been used that have tended to employ friction surfaces in which the dynamic and static coefficients of friction may have been significantly different, yielding a stick-slip phenomenon that may not have been entirely advantageous. It may be advantageous to combine the feature of a self-steering capability with dampers that have a reduced tendency to stick-slip operation.
Description of Bearing Adapter
The rocking interface surface of the bearing adapter might have a crown, or a concave curvature, like a swing motion truck, by which a rolling contact on the rocker permits lateral swinging of the side frame. The bearing adapter to pedestal seat interface might also have a fore-and-aft curvature, whether a crown or a depression, and that, for a given vertical load, this crown or depression might tend to present a more or less linear resistance to deflection in the longitudinal direction, much as a spring or elastomeric pad might do.
For surfaces in rolling contact on a compound curved surface (i.e., having curvatures in two directions) as shown and described herein, the vertical stiffness may be approximated as infinite (i.e. very large as compared to other stiffnesses); the longitudinal stiffness in translation at the point of contact can also be taken as infinite, the assumption being that the surfaces do not slip; the lateral stiffness in translation at the point of contact can be taken as infinite, again, provided the surfaces do not slip. The rotational stiffness about the vertical axis may be taken as zero or approximately zero. By contrast, the angular stiffnesses about the longitudinal and transverse axes are non-trivial. The lateral angular stiffnesses may tend to determine the equivalent pendulum stiffnesses for the sideframe more generally.
The stiffness of a pendulum is directly proportional to the weight on the pendulum. A pendulum may tend to maintain a general proportionality between the weight borne by the wheel and the stiffness of the self-steering mechanism as the lading increases.
FIG. 5 shows an embodiment of bearing adapter and pedestal seat assembly. Bearing adapter 44 has an underside or lower portion, 144, formed to accommodate, and to seat upon, the round cylindrical external casing of bearing 46, that is itself mounted on the end of a shaft, namely an end of axle 48. Bearing 46 is a sealed roller bearing according to the applicable AAR standard for the given axle size, such as used in North America.
Bearing adapter 44 has an upper portion 146 that has a centrally located, upwardly protruding fitting in the nature of a male bearing adapter interface portion 148. A mating fitting, in the nature of a female rocker seat interface portion 150 is rigidly mounted within the roof 152 of the sideframe pedestal. The upper fitting 40, whichever type it may be, has a body that may be in the form of a plate 154 having, along its longitudinally extending, lateral margins a set of upwardly extending lugs or ears, or tangs separated by a notch, that bracket, and tightly engage lugs, thereby locating upper fitting 40 in position, with the back of the plate of fitting 40 abutting the flat, load transfer face of roof 152. Alternatively, upper fitting 40 may be formed as part of the sideframe casting (as shown), and may be machined to finished dimensions as may be appropriate. Upper fitting 40 may be a pedestal seat fitting with a hollowed out female bearing surface. When sideframes 26 are lowered over the wheel sets 50, the end reliefs, or channels 156 lying between the bearing adapter corner abutments 158 seat between the respective side frame pedestal jaws 154. With the sideframes in place, bearing adapter 44 is thus captured in position with the male and female portions of the adapter interface in mating engagement. Auxiliary centering members 155 seat in channels 156 between the end faces 157 of bearing adapter 44 and pedestal jaw thrust blocks or thrust lugs 159.
Male portion 148 (FIG. 5) has been formed to have a generally upwardly facing surface that has both a first curvature r₁to permit rocking in the longitudinal direction, and a second curvature r₂to permit rocking (i.e., swing motion of the sideframe) in the transverse direction. Similarly, in the general case, female portion 150 has a surface having a first radius of curvature R₁in the longitudinal direction, and a second radius of curvature R₂in the transverse direction. The engagement of r₁with R₁may tend to permit a rocking motion in the longitudinal direction, with resistance to rocking displacement being proportional to the weight on the wheel. That is to say, the resistance to angular deflection is proportional to weight rather than being a fixed spring constant. This may tend to yield passive self-steering in both the light car and fully laden conditions in which the magnitude of angular displacement of the axle is proportional to the restoring force, and may be linearly proportionate. The centered condition represents a local, minimum potential energy condition for the system. As the axle is urged to deflect by the force, the rocking motion may tend to raise the car, and thereby to increase its potential energy.
In general, the deflection may be measured either by the angular displacement of the axle centreline, θ₁, or by the angular displacement of the rocker contact point on radius r₁, as θ₂. Jaws 154 constrain the arcuate deflection of bearing adapter 44 to a limited range. A typical range might be about 3 degrees of arc. A typical maximum value of δ_longmay be about +/− 3/16″ to either side of the vertical, at rest, center line.
The rolling contact surface of the bearing has a local minimum energy condition when centered under the corresponding seat, and it is preferred that the mating rolling contact surface be given a radius that may tend to encourage self-centering of the male rolling contact element. That is to say, displacement from the minimum energy position (preferably the centered position) may tend to cause the vertical separation distance between the centerline of the wheelset axis (and hence the centreline of the axis of rotation of the bearing) to become more distantly spaced from the sideframe pedestal roof, since the rocking action may tend marginally to raise the end of the sideframe, thus increasing the stored potential energy in the system.
This can be expressed differently. In cylindrical polar co-ordinates, the long axis of the wheelset axle may be considered as the axial direction. There is a radial direction measured perpendicularly away from the axial direction, and there is an angular circumferential direction that is mutually perpendicular to both the axial direction, and the radial direction. There is a location on the rolling contact surface that is closer to the axis of rotation of the bearing than any other location. This defines the “rest” or local minimum potential energy equilibrium position. Since the radius of curvature of the rolling contact surface is greater than the radial length, L, between the axis of rotation of the bearing and the location of minimum radius, the radial distance, as a function of circumferential angle θ will increase to either side of the location of minimum radius (or, put alternatively, the location of minimum radial distance from the axis of rotation of the bearing lies between regions of greater radial distance). Thus the slope of the function r(θ), namely dr/dθ, is zero at the minimum point, and is such that r increases at an angular displacement away from the minimum point to either side of the location of minimum potential energy. Where the surface has compound curvature, both dr/dθ and dr/dL are zero at the minimum point, and are such that r increases to either side of the location of minimum energy to all sides of the location of minimum energy, and zero at that location. This may tend to be true whether the rolling contact surface on the bearing is a male surface or a female surface or a saddle, and whether the center of curvature lies below the center of rotation of the bearing, or above the rolling contact surfaces. The curvature of the rolling contact surface may be spherical, ellipsoidal, toroidal, paraboloid, parabolic or cylindrical. The rolling contact surface has a radius of curvature, or radii of curvature, if a compound curvature is employed, that is, or are, larger than the distance from the location of minimum distance from the axis of rotation, and the rolling contact surfaces are not concentric with the axis of rotation of the bearing.
Another way to express this is to note that there is a first location on the rolling contact surface of the bearing that lies radially closer to the axis of rotation of the bearing than any other location thereon. A first distance, L is defined between the axis of rotation, and that nearest location. The surface of the bearing and the surface of the pedestal seat each have a radius of curvature and mate in a male and female relationship, one radius of curvature being a male radius of curvature r₁, the other radius of curvature being a female radius of curvature, R₂, (whichever it may be). r₁is greater than L, R₂is greater than r₁, and L, r₁and R₂conform to the formula L⁻¹−(r₁ ⁻¹−R₂ ⁻¹)>0, the rocker surfaces being co-operable to permit self-steering.
FIGS. 6 a and 6 b
FIG. 6 a relates to a three piece truck 160, the relevant portions being shown in partial section and exploded view, keeping in mind the axes of symmetry of the truck about both the x and y axes. FIG. 6 b shows, by way of contrast, the same partially sectioned, exploded view of a truck having the elements of truck 20. Truck 160 has three major elements, those elements being a truck bolster 162, that is symmetrical about the truck longitudinal centreline, and a pair of first and second side frames, indicated as 164. Only one half of one side frame is shown given the symmetry of truck 160. The difference between the trucks of FIGS. 6 a and 6 b is that truck 160 is a single damper arrangement, i.e., with single-mounted fore-and- aft dampers 166, 168, as opposed to the double-damper, inboard and outboard four-cornered arrangement of FIG. 6 b. The sideframes have side frame columns 170 with respective bearing surfaces 172 against which the dampers work, surfaces 172 being formed as plates or plate-like sections or portions of the bolster casting itself, rather than as removable wear plates. It may be noted that a 3:2:3 spring arrangement is shown as 174, with the middle spring of each of the outboard columns of springs being mounted independently to drive a respective one of dampers 166, 168. A 3×3 or other spring arrangement could as easily be employed.
FIGS. 6 c and 6 d
FIGS. 6 c and 6 d relates to a three piece truck 200, again keeping in mind the axes of symmetry of the truck about both the x and y axes. Truck 200 has three major elements, those elements being a truck bolster 192, that is symmetrical about the truck longitudinal centreline, and a pair of first and second side frames, indicated as 194. Only one side frame is shown in FIG. 6 c given the symmetry of truck 200. Three piece truck 200 has a resilient suspension (a primary suspension) provided by a spring groups 195 trapped between each of the distal (i.e., transversely outboard) ends of truck bolster 192 and side frames 194. The embodiment of FIG. 6 c, is substantially similar to the embodiment of FIG. 2 b, differing by having spring groups 195 having two rows of springs 203, a transversely inboard row and a transversely outboard row, rather than three rows of springs as in truck 20. Each side frame assembly also has four friction damper wedges arranged in first and second pairs of transversely inboard and transversely outboard wedges 204, 205, 206 and 207 that engage the seats of the bolster in a four-cornered arrangement, and upon which the corner springs of the spring group 195 bear. In this instance there is no middle land between the inboard and outboard wedges. Each vertical sideframe column 196 has a wear surface formed as part of the sideframe casting, the difference between sideframe column 196 and sideframe column 36 being that sideframe column 196 has a friction wear surfaces of width corresponding to two rows of springs, plus lateral and vertical travel, rather than three rows.
It may be noted, as in document WO 2005/005219, there are several diameters of damper wedge “side springs” as they are sometimes called. The springs in an embodiment such as that of FIGS. 6 c and 6 d may be as much as 8½ inches in outside diameter. More customarily, damper springs may be up to the diameter of an AAR D5 spring, nominally 5½ inches. Side springs, or damper springs, however they may be termed, may also include inner springs nested within the main coils, and inner-inner springs nested within the inner coils, as may be.
Sloped Wedge Surface
Where damper wedges are employed, a generally low friction, or controlled friction pad or coating may also be employed on the sloped surface of the damper that engages the wear plate (if such is employed) of the bolster pocket where there may be a partially sliding, partially rocking dynamic interaction. In some embodiments the static and dynamic coefficients may be the same, or nearly the same, and may have little or no tendency to exhibit stick-slip behaviour, or may have a reduced stick-slip tendency as compared to cast iron on steel. Further, the use of brake linings, or inserts of cast materials having known friction properties may tend to permit the properties to be controlled within a narrower, more predictable and more repeatable range such as may yield a reasonable level of consistency in operation.
A damper may be provided with a friction specific treatment, whether by coating, pad or lining, on both the vertical friction face and the slope face. The coefficients of friction on the slope face need not be the same as on the friction face, although they may be. In one embodiment it may be that the coefficients of static and dynamic friction on the friction face may be about 0.3, and may be about equal to each other, while the coefficients of static and dynamic friction on the slope face may be about 0.2, and may be about equal to each other. In either case, whether on the vertical bearing face against the sideframe column, or on the sloped face in the bolster pocket, the present inventors consider it to be advantageous to avoid surface pairings that may tend to lead to galling, and stick-slip behaviour.
Combinations and Permutations
The present description recites many examples of dampers and bearing adapter arrangements. Not all of the features need be present at one time, and various optional combinations can be made. As such, the features of the embodiments of several of the various figures may be mixed and matched, without departing from the spirit or scope of the invention. For the purpose of avoiding redundant description, it will be understood that the various damper configurations can be used with spring groups of a 2×4, 3×3, 3:2:3, 2:3:2, 3×5 or other arrangement. Similarly, several variations of bearing to pedestal seat adapter interface arrangements have been described and illustrated. There are a large number of possible combinations and permutations of damper arrangements and bearing adapter arrangements. In that light, it may be understood that the various features can be combined, without further multiplication of drawings and description.
The various embodiments described herein may employ self-steering apparatus in combination with dampers that may tend to exhibit little or no stick-slip. They may employ a “Pennsy” pad, or other elastomeric pad arrangement, for providing self-steering. Alternatively, they may employ a bi-directional rocking apparatus which may include a rocker having a bearing surface formed on a compound curve as illustrated and described herein. Further still, the various embodiments described herein may employ a four cornered damper wedge arrangement, which may include bearing surfaces of a non-stick-slip nature, in combination with a self-steering apparatus, and in particular a bi-directional rocking self-steering apparatus, such as a compound curved rocker.
Various embodiments have been described in detail. Since changes in and or additions to the above-described examples may be made without departing from the nature, spirit or scope of the invention, the invention is not to be limited to those details but only to that of the claims, subject to purposive construction as required by law.

Claims

We claim:

1. A sideframe for a railroad car truck, said sideframe having a sideframe column defining a bearing surface for engagement with at least one non-metallic damper, said sideframe column bearing surface being free of removable wear plates.

2. The sideframe of claim 1 wherein said sideframe is a unitary casting.

3. The sideframe of claim 1 wherein said sideframe bearing surface has a width defining a bearing accommodation for more than one damper.

4. The sideframe of claim 3 wherein said sideframe defines a bottom seat for a main spring group of the railroad car truck, and the bearing surface is wider than the bottom seat.

5. The sideframe of claim 1 wherein a laterally outermost extremity of said bearing surface defines a gib engagement abutment operable to restrain lateral motion of a bolster of the railroad car truck.

6. The sideframe of claim 1 wherein said bearing surface defines a yaw motion moment couple reaction surface.

7. The sideframe of claim 1 wherein said bearing surface has an as-cast finish.

8. The sideframe of claim 1 wherein said bearing surface has a machined finish.

9. The sideframe of claim 1 wherein said sideframe has a long axis, and said bearing surface lies substantially in a plane, and said plane being normal to said long axis.

10. The sideframe of claim 1 wherein said sideframe has two said sideframe columns, each of said sideframe columns having a respective bearing surface that is free of removable wear plates, and wherein said respective bearing surfaces are planar, parallel, spaced apart and facing each other.

11. A combination of the sideframe of claim 1 and a set of friction dampers, said set of friction dampers including at least a first damper having a non-metallic working surface, said non-metallic working surface being in mating sliding relationship with said bearing surface.

12. The sideframe of claim 1 wherein said sideframe includes a pedestal seat, and said pedestal seat has a self-steering apparatus mounted thereto.

13. An apparatus comprising the sideframe of claim 1, wherein the apparatus includes any permutation including at least two of the following:

(a) said sideframe is a unitary casting;

(b) said sideframe bearing surface has a width defining a bearing accommodation for more than one damper;

(c) said sideframe defines a bottom seat for a main spring group of the railroad car truck, and the bearing surface is wider than the bottom seat;

(d) a laterally outermost extremity of said bearing surface defines a gib engagement abutment operable to restrain lateral motion of a bolster of the railroad car truck;

(e) said bearing surface defines a yaw motion moment couple reaction surface;

(f) said sideframe has a long axis, and said bearing surface lies substantially in a plane, said plane being normal to said long axis;

(g) the combination includes a set of friction dampers, said set of friction dampers including at least a first damper having a non-metallic working surface, said non-metallic working surface being in a mating sliding relationship with said bearing surface; and

(h) said sideframe includes a pedestal seat, and said pedestal seat has a self-steering apparatus mounted thereto.

14. A sideframe casting for a railroad car truck, said sideframe casting defining a sideframe window, and said sideframe casting including at least a first sideframe column bordering said window, said first sideframe column including a first bearing surface oriented to work against a non-metallic damper member.

15. A combination comprising the sideframe casting of claim 14 and at least a first friction damper having a first non-metallic damping member, said first friction damper being positioned to work slidingly against said first bearing surface.

16. The combination of claim 15 further comprising a second friction damper having a second non-metallic damping member, said second friction damper being positioned to work slidingly against said first bearing surface, said second friction damper being located sideways relative to said first friction damper; said first and second friction dampers being biased to work against said first bearing surface; and said second friction damper being biased independently of said first friction damper.

17. The combination of claim 16 wherein said first and second friction dampers are spaced apart by a distance greater than a D5 spring diameter.

18. The sideframe casting of claim 14 wherein said casting includes a second sideframe column having a respective second bearing surface.

19. A three-piece railroad freight car truck having a bolster mounted cross-wise between a pair of first and second sideframes, the truck having non-metallic friction dampers mounted to work between the bolster and each of the sideframes, and the sideframes being free of removable wear plates.

20. A railroad car truck, said railroad car truck being a three-piece truck having a bolster mounted cross-wise between a pair of first and second sideframes, said bolster having a first end associated with said first sideframe, and a second end associated with said second sideframe, said truck having non-metallic friction dampers mounted to work between said bolster and each of said sideframes, each of said sideframes having bearing surfaces against which respective ones of said non-metallic friction dampers work, said bearing surfaces being permanent portions of each said sideframe.

21. The railroad car truck of claim 19 wherein said first sideframe is a casting; said casting defines a sideframe window; said window being bounded fore-and-aft by first and second sideframe columns, and said bearing surfaces being integrally cast portions of said sideframe columns.

22. The railroad car truck of claim 19 wherein said truck includes wheelsets, said sideframes are mounted on said wheelsets, and said truck includes self-steering apparatus.

23. The railroad car truck claim 19 wherein said bearing surfaces are as-cast.

24. The railroad car truck claim 19 wherein said bearing surfaces are machined surfaces.

25. The railroad car truck claim 19 wherein said sideframe has a first said bearing surface and a second said bearing surface, said sideframe has a longitudinal axis, said longitudinal axis is normal to said first and second bearing surfaces, and said first and second bearing surfaces face each other and lie in parallel spaced apart planes.

26. A sideframe casting for a railroad car truck, said sideframe having a lengthwise axis, said sideframe casting defining a sideframe window, said casting including first and second opposed sideframe columns bordering said window; said first and second sideframe columns having respective first and second friction damper bearing surfaces of said casting; said first and second friction damper bearing surfaces facing toward each other; said first and second friction damper bearing surfaces being parallel to each other and normal to said lengthwise axis; and each of said first and second bearing surfaces being wider than two D5 springs placed side-by-side.

27. The sideframe casting of claim 26 wherein said first and second friction damper bearing surfaces are machined surfaces of said sideframe columns.

28. The sideframe casting of claim 26 wherein said first and second friction damper bearing surfaces of said sideframe columns are as-cast.