Note: Descriptions are shown in the official language in which they were submitted.
AUTORACK RAILROAD CAR AND UNDERFRAME THEREFOR
Field of the Invention
This invention relates to the field of railroad freight cars, and, in
particular to the field
of railroad freight cars for carrying automotive vehicles, this kind of car
being referred to in
the industry as an "autorack" car.
Background
Modern autorack cars, which is to say autorack cars built since about 1980,
have
typically had the structure of a flat car underframe covered by a surface deck
for supporting
automotive vehicles. Since automobiles are, overall, very low density lading
as compared to
commodities such as coal, sand and gravel aggregate, grain or ores, the flat
car underframes
tend to be limited by allowable truck center spacing, rather than by the gross
weight on rail
limit. Currently, autorack cars are typically 89 or 90 ft long as measured
over the strikers and
as much as 66 ft between truck centers.
The autorack car underframes carry a housing that may tend to resemble a barn.
This
superstructure is typically referred to as the "rack" of the autorack. In
earlier eras the racks
were open. However, open racks invite theft and vandalism. Thus modern
autorack cars
include full side panels (which may have perforations to permit ventilation)
and fully closing
end doors, with the intention of discouraging thieves and vandals. Most
typically the housing
structure includes a series of vertical posts spaced along the sides of the
car, and one or two
additional decks spaced upwardly from the main deck, and upon which respective
second and
third layers of automotive vehicles may be transported. That is, the rack may
be a bi-level rack
(i.e., a single elevated deck spaced upwardly above the main deck of the
underframe) or a tri-
level rack (two upper decks rather than one). These decks are carried on some
kind of
framework of sideposts spaced along the car, with diagonal bracing or shear
web panels
between the posts, as may be. The cars tend to be as tall as permitted under
AAR Plate 'F',
namely 20' ¨ 2" maximum height above Top of Rail (TOR). This housing may tend
to have
gable ends, those ends being open to permit circus loading of the cars, i.e.,
sequential loading
of the automotive vehicles by driving in one end, and out the other on
arrival. Although other
kinds of doors are known, most typically radial arm doors are mounted at the
gable ends and
are movable between open and closed positions to govern loading and unloading
of the cars.
In at least one version of autorack, used for delivering highway tractors to
market, there are no
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additional elevated decks. The racks are typically replaced twice during the
economic life of
the autroack car underframe. That is, the old set of racks is removed from the
underframe and
replaced with a new set of racks.
The underframe traditionally provides resistance to vertical bending. Given
the great
length of span between the truck centers, the center sills of autorack car
bodies have tended to
be "fish bellied". That is, the center sill is relatively shallow at the ends
of the car at or adjacent
to the centerplates over the trucks (i.e., at the truck centers), and rather
deeper in the middle
between the trucks, perhaps with a downwadly bent, or curved, or deviated,
bottom flange. A
fish-belly center sill is therefore a fabricated sill in which the bottom
profile of the center sill
webs is not level, but rather defines the profile of the depth of the beam as
a function of
longitudinal position. The bottom flange, or bottom cover plate of the center
sill is not flat and
level, but rather follows the fish-belly profile. The bottom flange may be
formed of sections
of plate welded to the webs and butt-welded end to end. The sections of the
bottom flange
may not be co-planar. That is, the fish-belly causes a vertical slope
discontinuity. Where there
is an abrupt change in properties in the flange, there may also be a
corresponding discontinuity
in the stress field. In the general case, the predominant loading modes in the
bottom flange are
(i) longitudinal tension induced by bending, and (ii) longitudinal tension or
compression
induced by buff and draft loads.
The inside width of section of the center sill is typically 12 ¨ 7/8 inches.
The depth
over the centerplates, (i.e., corresponding to the depth of a standard draft
sill) is typically 12 ¨
16 inches. The depth in the fish-belly is typically about 22 inches, more or
less, at the mid-
span location between the trucks and along much of the distance along that
span between the
trucks. A conventional autorack center sill may thus tend to be rather heavy
and deep.
Summary of the Invention
In a first aspect of the invention there is an autorack railroad car. It has
an underframe
structure that includes a center sill. The center sill has a first end and a
second end. There is a
first deck for transporting automotive vehicles. The first deck is supported
by the center sill.
There is a first centerplate located closer to the first end of the center
sill than to the second
end thereof. There is a second center plate located closer to the second end
of the center sill
than to the first end thereof. The first center plate is seatable at a truck
center of a first truck.
The second center plate is seatable at a truck center of a second truck. The
center sill runs
continuously from the first centerplate to the second center plate. The center
sill has a first
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location, the first location being a mid-span location midway between the
first and second
center plates. The center sill has a first depth of section at the mid-span
location. The center
sill has a second depth of section at a second location away from mid-span
location. The
second depth of section is greater than is the first depth of section.
In a feature of that aspect of the invention, the center sill has a greater
second moment
of area in bending at the second location than at the first location. In
another feature, the center
sill includes a draft sill portion, the second depth of section is measured at
the draft sill portion;
and the first depth of section is less than 2/3 of the second depth of
section. In a further feature,
the center sill has a depth of section at the first location of not more than
12 inches. In still
another feature, the center sill has a depth of section at the first location
of not more than 8
inches. In still another feature, the center sill has a truck center distance
of not less than sixty
feet.
In yet another feature, the center sill has a top cover plate, a bottom
flange, and at least
one shear web extending therebetween; and at least one of (a) when the car is
unladen, the
bottom flange is substantially flat and horizontal over substantially the
entire distance between
truck centers; (b) the top flange at the first location is closer to TOR than
at the second location;
and (c) at least one of the shear webs is shallower at the first location than
at the second
location. In a further feature, the center sill satisfies any permutation,
including all of, of (a),
(b) and (c).
In still another feature, at the first location the underframe has a second
moment of area
in vertical bending less than 4000 inzi. In another feature, at the first
location the center sill has
a second moment of area of less than 750 inzi. In a further feature, the
second moment of area
of the center sill at the first location is less than 400 inzi. In another
feature, the autorack car
has first and second side sills running along respective first and second
laterally outboard
margins of the deck, the center sill has a top flange, a bottom flange, and
first and second webs
extending between the top flange and the bottom flange; and, at the first
location at least one
of: (a) the first side sill has a greater depth of section than the center
sill; and (b) the first side
sill has a lower flange and an upper flange, and, at the first location, the
bottom flange of the
center sill is carried at a height that is at least as high as the lower
flange of the first side sill.
In a further feature, the car includes a housing running lengthwise along the
car parallel to the
center sill and overspaning the deck. The housing has a first end and a second
end. The
housing has an accessway at one end thereof to permit the loading of vehicles.
The housing
includes a pair of first and second top chords upwardly distant from the deck.
The autorack
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railroad car includes shear connections between the top chords and the
underframe. In a still
further feature, the top chords and the center sill co-operate to define a
deep truss. The truss
has a neutral axis. In bending due to vertical load the center sill lies below
the neutral axis and
the top chords lie above the neutral axis.
In another aspect of the invention there is an autorack railroad car
underframe. It has
a length-wise running straight-through center sill, with a span of at least 60
feet between truck
centers. The center sill is free of a fish-belly bottom flange, and has at
least one of: (a) a mid-
span depth of section of less than 12 inches; (b) a mid-span second moment of
area of less than
750 in4; and (c) a mid-span cross-sectional area of less than 40 in2.
In a feature thereof, the underframe has first and second side sills running
lengthwise
along opposite margins thereof. Each of the side sills has a respective mid-
span cross-sectional
area and a mid-span depth of section. The mid-span depth of section of each of
the side sills
is at least as great as the mid-span depth of section of the center sill. In
another feature, the
underframe includes a first deck structure upon which automotive vehicles may
be conducted
lengthwise over the underframe. The first deck structure has a roadway surface
at one of the
truck centers that is carried at a first height above TOR. The first deck
structure has a roadway
surface at mid-span that is carried at a second height above TOR. The second
height is less
than the first height. The center sill has a top flange, a bottom flange, and
at least one shear
web extending therebetween. The top flange is closer to the bottom flange at
mid-span than at
either truck center. In another feature, the bottom flange is maintained at a
substantially
constant height relative to TOR between the truck centers.
In another aspect of the invention there is an autorack railroad car body unit
underframe. The underframe has a lengthwise running straight-through center
sill running
continuously from end to end of the car body unit. The center sill is carried
by railroad car
trucks in longitudinal rolling motion along railroad car tracks. The center
sill has a first end
and a second end. The center sill has a mid-span location mid-way between the
first end and
the second end. The center sill has a top flange, a bottom flange, and at
least one shear web
member extending therebetween. The center sill has a smaller depth of section
at the mid-span
location than at the first end.
In a feature of that aspect, the body unit underframe center sill top flange
is carried at
a lower height above Top of Rail at the mid-span location than at the first
end. In another
feature, the bottom flange is substantially flat from end to end of the center
sill. In a further
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feature, the top flange is closer in height to the bottom flange at the mid-
span location than at
the first end, and, when the underframe is unladen, the bottom flange is no
closer to Top of
Rail at the mid-span location than at the first end.
In another aspect of the invention, there is an underframe for an autorack
railroad car.
The underframe has a straight-through center sill, a first side sill, and a
second side sill, all
running in the same direction, the center sill is between the side sills. The
straight-through
center sill has a first end and a second end. Decking extends between the
center sill and the
first side sill, and between the center sill and the second side sill, the
decking providing a
roadway along which to conduct lading. At least the first end of the straight-
through center
sill is a draft sill. The draft sill has a draft sill depth. The center sill
has a mid-span portion
mid-way between the first and second ends. The mid-span portion has a mid-span
depth. The
first side sill has a depth. At least one of: (a) the mid-span depth is less
than the draft sill depth;
(b) the mid-span depth is less than the side sill depth; (c) the draft sill
depth is less than the
side sill depth; and (d) the mid-span portion of the center sill has a bottom
flange. The first
side sill has a bottom flange. The bottom flange of the mid-span portion of
the center sill is
carried more distantly from Top of Rail than is the bottom flange of the first
side sill.
In a further feature, the underframe conforms to any two of the foregoing (a),
(b), (c)
and (d). In a still further feature, the underframe has any three of (a), (b),
(c) and (d). In a yet
further feature the underframe has all of (a), (b), (c) and (d).
In still another aspect of the invention there is an autorack railroad car
body. The car
body has first and second ends. The car body has an underframe and a housing
structure over-
spanning the underframe. The housing structure includes a longitudinally
running array of
posts mounted along lateral margins of the underframe, longitudinally running
first and second
top chords surmounting the posts, a roof structure extending upwardly of, and
between, the
first and second top chords, side wall panels mounted between pairs of the
posts, the housing
having at least a first end through which to permit lengthwise loading of
vehicles. The
underframe includes a center sill, and a pair of first and second side sills.
The center sill and
the side sills run lengthwise along the car body. The first side sill is
spaced laterally to a first
side of the center sill, the second side sill is spaced laterally to a second
side of the center sill,
the center sill being between the first and second side sills. The underframe
has decking upon
which vehicles can be conducted lengthwise along the car body. The decking
extends between
the center sill and the first side sill, and extends between the center sill
and the second side sill.
The center sill includes at least one draft sill portion adjacent one end of
the car body, and a
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central portion. The central portion is located in a medial portion of the car
away from the first
end of the car body and away from the second end of the car body. Adjacent to
the draft sill,
the decking is carried at a first height relative to TOR. Adjacent to the
central portion of the
center sill the decking is carried at a second height relative to TOR. The
first height is greater
than the second height. The center sill has a first depth of section at the
draft sill. The center
sill has a second depth of section at the central portion thereof. The second
depth of section is
less than the first depth of section.
In another aspect of the invention there is a center sill for an autorack
railroad car. The
center sill has a top flange, a bottom flange, and first and second webs
extending between the
top flange and the bottom flange. The center sill has a first end, a second
end, and a medial
portion therebetween. The bottom flange is carried at a height relative to
TOR. The height is
constant over the length thereof. The center sill has a minimum depth of
section, hm, at a first
longitudinal station in the medial portion thereof.
In a further feature, the center sill has at least one truck center, the
center sill has a
depth of section at the truck center, hTc; and hm is less than hTc. In another
feature, the bottom
flange of the center sill is free of slope discontinuities in elevation
therealong. In still another
feature, the medial portion of the center sill is of constant cross-sectional
area. In still another
feature, the center sill is combined with decking mounted to cooperate
therewith and upon
which longitudinally to conduct lading. The decking extends laterally of the
center sill. The
decking is carried at a first height at the first end of the center sill, and
at a second height along
the medial portion thereof. The second height is less than the first height,
and, at the minimum
depth of section, hm, the top flange is carried at a height that is less than
the first height of the
decking. In a still further feature, the combination further includes a pair
of longitudinally
running laterally spaced apart first and second side sills. At the first
longitudinal station, the
first side sill has a depth of section that exceeds the depth of section hm.
In another feature,
the first side sill has an upper flange and a lower flange, the lower flange
is carried one of (a)
flush with; and (b) lower than, the bottom flange of the center sill. In still
another feature, the
upper flange of the first side sill is carried higher than the decking. In yet
another feature, the
upper flange of the first side sill is carried higher than the top flange of
the center sill over the
medial portion thereof.
In another aspect of the invention there is a center sill for an autorack
railroad car. The
center sill has a first end, a second end, and a medial portion between the
first and second ends.
The center sill has a top cover plate, a bottom cover plate, and a pair of
first and second laterally
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spaced apart webs extending between the top cover plate and the bottom cover
plate, the top
cover plate and the bottom cover plate defining respective top and bottom
flanges of the center
sill. At least one of the first and second ends includes a draft sill. The
draft sill has a maximum
depth of section, hd, at a first longitudinal station of the center sill. The
medial portion has a
minimum depth of section, hm, at a second longitudinal station of the center
sill distant from
the first longitudinal station. At the first longitudinal station the top
cover plate is carried at a
first height, hi relative to TOR. At the second longitudinal station the top
cover plate is carried
at a second height, h2, relative to TOR. hi is greater than h2; and hd is
greater than hm.
In a feature of that aspect of the invention, the center sill has at least one
truck center.
At the first truck center the top cover plate is carried at a height, hTc. hTc
is greater than hm;
hd is greater than hTc. In another feature, the bottom cover plate of the
center sill is free of
slope discontinuities in elevation. In still another feature, the bottom cover
plate is planar from
end to end longitudinally. In still another feature, the bottom flange of the
center sill is carried
at a constant height, hBF, throughout its length.
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.
Brief Description of the Figures
The description is accompanied by a set of illustrative Figures in which:
Figure la is a general arrangement, side view of an autorack railroad car
according to
an aspect of the invention;
Figure lb is an end view of the autorack railroad car of Figure la, without
trucks, and
with doors removed;
Figure lc is an isometric view of the autorack railroad freight car of Figure
la without
trucks; with housing side panels and roof panels removed to show internal
structure, and with the end portions of the mid-level deck removed;
Figure ld is a perspective view, from below, of one half of the autorack
railroad car
structure of Figure lc;
Figures 2a is a top view of the under-frame of the autorack railroad car
structure of
Figure lc;
Figure 2b is a side view of the underframe of the autorack railroad car of
Figure 2a;
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Figure 2c is an isometric view of one half of the underframe of Figure 2a on a
view
from one corner and above;
Figure 2d is an isometric view of one half of the underframe of Figure 2a on a
view
from one corner and below;
Figure 3a is an end view of the underframe of Figure 2a;
Figure 3b is an end view of a prior art underframe in comparison to that of
Figure 3a;
Figure 3c is an enlarged partial side view of the underframe of Figure 2b;
Figure 3d is an enlarged partial side view of the prior art underframe of
Figure 3b;
Figure 4a shows bending resistance properties of the center sill of the
underframe of
Figure 2a at the truck center;
Figure 4b shows bending resistance properties of the underframe of Figure 2a
at the
truck center;
Figure 4c shows bending resistance properties of the center sill of the
underframe of
Figure 2a at mid-span;
Figure 4d shows bending resistance properties of the underframe of Figure 2a
at mid-
span;
Figure 4e is a draft sill section on '4e' ¨ '4e' of Figure 3c; and
Figure 4f shows a cross-section of a prior art fish-belly center sill at mid-
section.
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,
aspects or features 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 noted
otherwise.
Where reference is made to a prior art structure, the prefix `P' before an
item number may be
understood as identifying prior art elements corresponding to the item of the
same number in
a presently described embodiment. For example 122 may pertain to a center sill
bottom flange
or bottom cover plate. P122 then corresponds to the prior art center sill
bottom flange or
bottom cover plate.
The terminology used in this specification is thought to be consistent with
the
customary and ordinary meanings of those terms as they would be understood by
a person of
ordinary skill in the railroad industry in North America. The Applicant
expressly excludes all
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interpretations that are inconsistent with this specification, and, in
particular, expressly
excludes any interpretation of the claims or the language used in this
specification such as may
be made in the USPTO, or in any other Patent Office, other than those
interpretations for which
express support can be demonstrated in this specification or in objective
evidence of record,
(for example, earlier publications by persons not employed by the USPTO or any
other Patent
Office), demonstrating how the terms are used and understood by persons of
ordinary skill in
the art, or by way of expert evidence of a person or persons of at least 10
years' experience in
the railroad industry in North America or in other former territories of the
British Empire and
Commonwealth.
In terms of general orientation and directional nomenclature, for railroad
cars described
herein the longitudinal direction is defined as being coincident with the
rolling direction of the
railroad car, or railroad car unit, when located on tangent (that is,
straight) track. In the case
of a railroad car having a center sill, be it a stub sill or a straight-
through center sill, the
longitudinal direction is parallel to the center sill, and parallel to the top
chords and side sills,
as may be. Unless otherwise noted, vertical, or upward and downward, are terms
that use top
of rail, TOR, as a datum. In the context of the car as a whole, the term
lateral, or laterally
outboard, or transverse, or transversely outboard refer to a distance or
orientation relative to
the longitudinal centerline of the railroad car, or car unit, or of the
centerline of a centerplate
at a truck center. The term "longitudinally inboard", or "longitudinally
outboard" is a distance
taken relative to a mid-span lateral section of the car, or car unit. Pitching
motion is angular
motion of a railcar unit about a horizontal or y axis perpendicular to the
longitudinal or x
direction. Yawing is angular motion about a vertical or z axis. Roll is
angular motion about
the longitudinal axis. Given that the railroad car described herein may tend
to have both
longitudinal and transverse axes of symmetry, a description of one half of the
car may generally
also be intended to describe the other half as well, allowing for differences
between right hand
and left hand parts. In this description, the abbreviation kpsi stands for
thousands of pounds
per square inch. To the extent that this specification or the accompanying
illustrations may
refer to standards of the Association of American Railroads (AAR), such as to
AAR plate sizes,
those references are to be understood as at the earliest date of priority to
which this application
is entitled.
It may by understood that persons of ordinary skill in the art are familiar
with the Rules
and Standards of the Association of American Railroads, which govern
interchange service in
North America. To the extent necessary or appropriate this specification is to
be interpreted
in a manner consistent with those Rules and Standards as they stood on the
date of priority of
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the earliest application from which this application claims priority, if any,
as if they formed
part of this specification.
Also for the purposes of the present discussion, it may be taken as a default
that the
underframe structure of the car is of all welded mild steel fabrication except
as otherwise
shown in the illustrations or indicated in the text. This need not necessarily
be the case. Other
materials, such as aluminum or stainless steel might be used. The upper rack
structure may
also be taken as being of steel fabrication, although, again, aluminum or
stainless steel might
be used, and the side web panels of the car, which may be made of mild steel,
stainless steel,
or aluminum might also be made from plastic composite material, which may be
reinforced
composite.
In Figures la ¨ id, an autorack railroad car is shown generally as 20. It has
an
underframe, or underframe assembly, indicated generally as 22, that is carried
upon railroad
car trucks 24 for rolling motion in a longitudinal or lengthwise direction
along railroad tracks.
Underframe 22 is surmounted by an overspanning housing structure indicated
generally as 26,
and which may be referred to as "the rack" or "racks" of the car. The ends of
housing structure
26 are open to permit loading and unloading of automotive vehicles. Ingress
and egress of
those vehicles is governed by a pair of end doors, 28, such as may be radial
arm doors movable
between open and closed positions.
Underframe 22 has a center sill 30. Center sill 30 is a "straight through"
center sill that
runs substantially entire length of the car between first and second ends 32,
34 at which strikers
35 are mounted. The main deck 50 extends to either side of the center sill to
the sides of the
car at side sills 42, 44. The term "straight through" is used in distinction
to stub center sills
such as used in, e.g., grain cars, where the center sill at each end of the
car is truncated inboard
of the center plate to leave a "stub", namely the center plate and draft sill
assembly. In a
straight through center sill, the center sill extends from one truck center to
the other. The
outboard portions of the center sill may be identified as the draft sills 38
in which the draft gear
and couplers are mounted. Draft sills 38 are extensions of center sill 30 that
extend
longitudinally outboard of (and often include) the truck center to the striker
35. Draft sills 38
may be cast assemblies to which the central portion 40 of center sill 30 is
connected, as by
welding. Alternatively, draft sills 38 may be fabricated structures that merge
into the fabricated
structure of central portion 40. Between each of the respective draft sills 38
and the central
portion 40 of center sill 30 there may be a transition region, indicted as 39.
In central portion
40, the bottom flange of the center sill is a single plate that forms a closed
box section with the
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center sill webs and the center sill top cover plate. Outboard of the truck
center the bottom
flange bifurcates into two toes that extend laterally sideways of the center
sill webs, leaving a
space therebetween by which to admit installation of the draft gear in the
draft pocket between
the webs.
Side sills 42, 44 run lengthwise along either side of underframe assembly 22,
and are
structurally connected to center sill 30 by an array of laterally extending
structural members
46 which may include cross-bearers 48 and cross-ties (not shown). A cross-
bearer is a beam
having a first end connected to the center sill at a connection that is
intended to be capable of
transmitting a bending moment, such that the cross-bearer is also a cantilever
that has its root,
or built-in end at the center sill. The second end or distal end or
transversely outboard end of
each cross-bearer is connected to the associated side sill running along that
side of the car. The
outboard connection may be a built-in connection or, perhaps more commonly, a
connection
that can be analysed as a pin joint. A cross tie is a laterally extending beam
member whose
ends are analysed as being simply supported pin connections that do not
transmit vertical load
bending moments. The ends of a cross-tie are typically at the center sill and
the respective side
sill. The side sills are themselves beams, typically of hollow or open
section, formed with an
upper flange, a lower flange, and a medial portion that functions as a web to
carry shear
between the upper and lower flanges. Side sills may sometimes have a somewhat
C-shaped
section, with the open part of the C facing toward the center sill and the
webs of the cross-
bearer and cross-ties extending into the C and forming a connection.
Main deck 50 typically extends across the car from side sill to side sill and
from end to
end of the car, and provides a driving pathway for wheeled vehicles, i.e., the
lading for this
kind of car. Main deck 50 is supported by side sills 42, 44, center sill 30,
and cross-bearers 48
and such cross-ties as may be, and may form the top flange of one or more of
them. In the
example illustrated, for example, main deck 50 forms, or is substantially
flush with the top
cover plate (i.e., top flange) of center sill 30, over most or all of its
length e.g., excluding draft
sills 38. The main deck may also form the top flange of the cross-bearers 48
and cross-ties (if
any). Main deck 50 may vary in elevation relative to Top of Rail, as described
below, but, in
general, may tend to meet side sills 42 and 44 at an intermediate height such
that top flange 52
of each side sill stands upwardly thereof, and the inner face of the
substantially upstanding web
or wall 54 of the side sill defines the outboard edge of the deck. The main
deck is open at the
ends (i.e., the curbs defined by the side sills only run along the sides) such
that wheeled vehicles
may be end-loaded. Each side sill also has a bottom flange 56. The side sill
outboard wall, or
web 54 may be kinked or slanted, and defines a vertical shear transfer web
between top flange
Date Recue/Date Received 2021-04-19
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52 and bottom flange 56. The side sill may be of open section (e.g., as a
formed C-channel or
regular or irregular shape) or closed section (e.g., a closed box-section),
but in either case wall
54 of the side sill functions as a shear web between top flange 52 and bottom
flange 56. Main
deck 50 may also have lengthwise-running stringers 58 located on the underside
of main deck
sheet 60 at the transverse location of the wheel trackways locally to
reinforce those areas of
the floor over which the vehicle wheels roll during loading and unloading of
the railroad car,
and which support the automobile lading during operation.
Looking at the underframe from underneath, the left hand and right hand end
sill
portions lying to either side of the bell-mouth 36 of draft sill 38 are
indicated as 62, 63. The
next longitudinally inboard left hand and right hand cross-members are shown
as 64, 65. The
next inboard cross-members, defining left hand and right hand portions of a
first lateral frame
66 (that is interrupted by draft sill 38), are indicated as 68, 69. Further
longitudinally inboard
is the main bolster, 70. Main bolster 70 is a stub bolster having laterally
extending left hand
and right hand stubs or arms, 71, 72, each of which has a side bearing pad 73,
backed up by a
bolster end web 74 and foot load spreading pad mounted to the underside of
main deck 50.
The center plate 76 is mounted at the intersection of center sill 30 and main
bolster 70. It may
be noted that main bolster 70 has longitudinally outboard and longitudinally
inboard webs 78,
79.
Still further inboard of main bolster 70 is a second lateral cross-member or
cross-bearer,
or frame 80 having left and right hand arms 82, 83 that extend between center
sill transition
region 39 and side sills 42, 44 respectively, there being an internal web (not
shown) within
transition section 39 providing web continuity across center sill 30. As can
be seen, the bottom
flanges 84 of arms 82, 83 may be flush, or substantially flush, with the
bottom flange of center
sill 30. Scab or backing plates may overlap the juncture between the frame
flange and center
sill flange junction, and may be welded all-around, this technique also being
used at the first
lateral frame and the first right and left hand cross-members, and elsewhere
in the car.
Still further inboard, extending laterally from central portion 40 of center
sill 30, is, or
are, a further cross-member or cross members in the form of cross-bearers 88,
90, 92. There
are internal webs (not shown) in central portion 40 providing lateral web
continuity across
center sill 30 of the webs of cross-bearers 88, 90, 92 respectively. Each of
cross-bearers 88,
90, 92 has a bottom flange 94 that may be flush with the bottom cover plate
(i.e., bottom flange)
of center sill 30. At the outboard, or distal, ends, each of cross-bearers 88,
90, 92 has a load
spreading web 96, and a web extension gusset 98. Load spreading web 96 extends
along the
Date Recue/Date Received 2021-04-19
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side sill laterally of each cross-bearer, and extends substantially vertically
between the toes of
the side sill section, and forms a locally closed box-section therewith having
web continuity
above and below main deck 50 at those locations. Web extension gusset 98
provides web
continuity in the plane of the web of each respective cross-bearer between
extension gusset 98
and outer wall 54 of side sill 42 (or 44), in effect forming a structural knee
in which gusset 98
has upper and lower flanges defined by main deck 50 and the cross-bearer
flange 94, and
laterally inboard and outboard flanges defined by members 54 and 96.
Looking at the framework of housing structure 26, housing structure 26
includes a
series of posts 100. There is an end framing structure, indicated as 102, that
extends upwardly
from the ends of the end sill, and which defines the shape of the gable end.
Next inboard is
"the first post", an upright side post 104 that runs between the side sill and
the top chord at the
station of the first lateral cross-members. Next inboard are posts 106,
mounted at the ends of
the first lateral frame (i.e., outboard of the truck center), and posts 108,
mounted at the ends of
the second lateral frame member. Posts 110 are mounted further inboard at the
ends of the
respective cross-bearers 88, 90, 92 that extend laterally of central portion
40 of center sill 30.
In the embodiment illustrated, there is no vertical post at the longitudinal
station of main bolster
70. Diagonal shear bracing 111, 112 is mounted between posts 108 and next
longitudinally
inboard posts 110. Longitudinally running top chords 114 run along, and tie
together, the tops
of all of posts 104, 106, 108, 110 and so on, as may be. The roof structure
116 is mounted atop
the top chords and restrains them in the lateral direction, and provide a
lateral shear connection
between the left and right hand side walls 117, 118 of the car. The roof
structure includes a
framework of lateral frames and longitudinal stringers (not shown). This
framework and the
stringer for a truss structure that cooperates with the truss structure of the
sidewall posts. The
framework may support one or more elevated decks, such as a second or mid-
level deck 107,
and a third or upper deck 109. The entire structure includes sidewall panels
119 that are
mounted between the various posts, and that may tend to act as shear panels
between those
posts and between the side sills and the respective top chords.
Center sill 30 has a cover plate, or top flange 120 (which, at some locations,
as noted
above, may be defined by main deck 50), a bottom cover plate or bottom flange
122, and left
and right hand vertical shear webs 124, 126. Over the truck centers, center
sill 30 has
respective truck center plates 76 that seat in the corresponding center plate
bowls of trucks 24.
Draft sill 38 may be fabricated as a welded assembly, or it may be an
integrally cast unit. For
autorack cars with, typically, a large longitudinal overhang, the draft sill
may tend to have a
bell-mouth as indicated at 36. The draft sill typically terminates at its
outboard end at a plate,
Date Recue/Date Received 2021-04-19
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that plate being striker 35. Inboard of striker 35 plate is a draft pocket,
indicated generally as
125 into which are mounted front and rear draft stops, draft gear, a yoke, and
a coupler. The
bottom of the draft sill is open, with laterally outwardly extending flanges,
or toes, as at 127,
128, the center being open to permit installation of the draft gear, and the
flanges having
mounting fittings for the coupler carrier plate in the usual manner.
Longitudinally outboard of
the center plate 76 the draft sill is, typically, AAR standard 12-7/8 inches
wide between inside
faces of the vertical shear webs at the draft gear, and typically 12 or more
inches deep from
the bottom surface of the bottom flanges to the top cover plate. For example,
the depth of the
draft sill at the bell-mouth, h132 as shown in Figure 3c may be of the order
of 17 ¨ 1/2 to 18
inches. The bottom flanges of the draft sill are usually carried about 28 ¨ 30
inches above
TOR. As a reference datum, the coupler centerline height above Top of Rail for
an unladen
car with new wheels is 34 ¨1/2 inches above TOR.
As noted, longitudinally inboard of the respective center plates 76 lies the
main or
central portion 40 of center sill 30. Along this portion, which extends
continuously to the far
end of car 20, bottom flange 122 is substantially horizontal when viewed at
any cross-section
in the y-z plane, from a viewpoint looking along the center sill. Furthermore,
as shown, bottom
flange 122 is substantially horizontal and flat in the lengthwise direction.
Further still, bottom
flange 122 is carried at the same height, or substantially the same height
relative to TOR from
striker to striker, as is symbolised by the constancy of that height, h122, in
the various views.
That is, as in the embodiment illustrated in Figure 3c, and in contrast to the
prior art
embodiment illustrated in Figure 3d, the height of the bottom flanges 127, 128
of draft sills 38
may be carried at the same height as the bottom cover plate 122 of center sill
30 at the truck
centers, at the same height in the center sill transition zone 39 immediately
longitudinally
inboard of the truck centers, and at the same height in the central, mid-span
portion 40 of center
sill 30 longitudinally inboard of transition 39. Mid-span portion 40 may be of
constant, or
substantially constant, cross-section, as in the embodiment illustrated. It
will be appreciated
that center sill 30 may have a slight camber in its unladen condition, such
that it may be flat
and horizontal when the car is fully laden, or the center sill bottom cover
plate 122 may vary
slightly in height. However, such variation, if any, is small, of the order of
2" or less, as
compared to the variation in a fish bellied sill. Expressed differently, even
if bottom cover
plate, or bottom flange, 122 is not perfectly level, it is free of upward and
downward kinks,
i.e., it is free of slope discontinuities in elevation.
For example, in a prior art fish-belly sill, in which the bottom flange is
identified as
P122 and the side webs are identified as P124, P126, the depth at mid-span may
be 22 inches
Date Recue/Date Received 2021-04-19
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or more. (In center sill 30, in some embodiments the corresponding mid-span
depth may be
about 7, 7 ¨ 1/4 or 7 1/2 inches or so). Thus the mid-span eccentricity of
the bottom cover plate
in the prior art example of Figure 3d and 4e, may be roughly 10 inches (i.e.,
22 ¨ 12). In the
embodiment illustrated, the eccentricity of the bottom cover plate may be
considered as zero,
and, in any case, less than 1/4, and more probably less than 1/10, of the
customary eccentricity
of the prior art sill. Expressed differently, whereas the eccentricity of the
bottom cover plate
of the prior art sill may be of the order of 5/6 of the draft sill depth, the
bottom cover plate
eccentricity of the embodiment shown and described is less than 1/6 of the
draft sill depth,
probably less than 1/12 of the draft sill depth, and may be substantially nil.
As may be noted, longitudinally inboard of the truck center, to the extent
that the top
cover plate of the center sill is defined by the main deck floor sheet 129,
and the height of main
deck floor sheet 129 relative to Top of Rail decreases, the overall depth of
center sill 30
between the top cover plate, i.e., the main deck sheet 129, and the bottom
cover plate 122, also
decreases. This is seen, for example, in the detailed view of Figure 3c, where
the end deck
portion 130 immediately inboard of striker 35 is carried lower than draft sill
top cover plate
132 in the region of bell-mouth 36, (that height, or depth to the center sill
bottom flange, being
indicated at hno) and longitudinally inboard to the location at which it
merges with the draft
sill cover plate at its downward tapered portion 133 longitudinally inboard of
the draft gear
(near frame 66). Inboard of the draft gear the floor elevation begins to
decrease, as indicated
in main deck first transition zone 134. In the embodiment illustrated,
transition zone 134 runs
from roughly the first lateral frame 66 adjacent to the rear draft stop to, or
just past, the truck
center. In the illustration shown, transition section 134 ends at an inboard
web 136 of main
bolster 70. Over the next adjacent portion 138, the deck sheet may be level,
i.e., carried at a
constant, or substantially constant, height (symbolised by local center sill
depth h138) from that
point longitudinally inboard to a longitudinal station clear of the maximum
excursion of the
truck. This distance may be 3 - 1/2 to 5 feet beyond the truck center. The
deck includes a
second transition portion 140 adjacent to portion 138, that second transition
portion 140
running for a modest distance of perhaps 1 ¨ 3 feet inboard to the minimum
height mid-span
level portion 142 of main deck 50. The change in elevation may be 2 ¨ 3
inches, or perhaps
1/6 to 1/4 of the draft sill depth.
In contrast to the prior art center sill, in which the mid-span section is
deeper than the
draft sill portion, in center sill 30 the mid-span portion depth is not
greater than the draft sill
portion depth at the draft gear (i.e., immediately inboard of the striker),
but, rather, may be the
same as, or less than, that depth longitudinally inboard of the truck center,
or, expressed
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differently, longitudinally inboard of the clearance limit of the truck. As
may also be noted,
and in contrast to the prior art fish-belly, the vertical depth of section
h142 of mid-span portion
40 (and, indeed, all of center sill 30) is less than the vertical overall
depth of section h42 of each
side sill 42, 44. In the center of mid-span portion 40 the center sill depth
is less than 3/5 of the
side sill depth. For a car with truck centers of over 65ft, this yields a
center sill mid-span depth
to truck center length aspect ratio of more than 1:85, and, in one embodiment
more than 1:100.
As may also be noted, it follows that the bottom flange, or extremity, 94 of
each cross-
bearer (or cross-tie) of car 20 is carried level from the side sill to the
center sill, at a height that
is maintained as high or higher than the bottom cover plate 122 of center sill
30. This may be
considered in contrast to the much deeper cross-bearer arms P88 and their
bottom flanges P94
in the prior art underframe shown. This may also be expressed differently. In
the prior art the
cross-bearers deepen toward the center sill in the deeper, central portion of
the car, as can be
seen from the downward and inward slope of bottom flange P94 and the deepening
section of
the web of cross-bearer arm P88. By contrast, the outboard tip or end of
bottom flange 94 of
cross-bearer 88 terminates at side sill 42 (or 44, as may be) and continues
inboard to center sill
30 at a level that is higher than the lowest extremity of side sill 42 (or
44), namely bottom
flange 56.
In the example shown,
1. At the truck centers, for the center sill webs and bottom flange
(i) the combined area of the center sill webs and bottom flange is about 20
sq. in.
(ii) the second moment of area in vertical bending is about 190 inzi.
(iii) the second moment of area in sideways bending is about 690 inzi.
(iv) the center sill depth is approximately 10 - 1/4 inches.
2. At the truck centers, for the underframe in total
(i) the combined area of the underframe is about 75 ¨ 80 sq.
in.
(ii) the second moment of area in vertical bending is about 1500 ¨ 1600
inzi.
(iii) the second moment of area in sideways bending is about 100,000 inzi.
(iv) the overall section depth is about 16.5 inches (being that of the side
sills).
3. At mid span, for the center sill webs and bottom flange
(i) combined area of center sill webs and bottom flange is about 15- 16 sq.
in.
(ii) the second moment of area in vertical bending is about 70 -
80 inzi.
Date Recue/Date Received 2021-04-19
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(iii) the second moment of area in sideways bending is about 470 - 480
inzi.
(iv) the center sill depth is approximately 8 - 1/8 inches.
4. At mid-span, for the underframe in total
(i) the combined area of the underframe is about 70 - 75 sq. in.
(ii) the second moment of area in vertical bending is about 1240 - 1250
inzi.
(iii) the second moment of area in sideways bending is about 95,000 inzi.
(iv) the overall section depth is about 16.5 inches (being that of the side
sills).
In the prior art example of Figure 4f, by contrast,
5. At mid-span, for the underframe in total
(i) the combined area of the underframe is about 88 - 89 sq.
in.
(ii) the area of the center sill flange and webs, alone, is about 30 ¨ 35
sq. in.
(iii) the second moment of area in vertical bending is about 8000 inzi.
(iv) the second moment of area in sideways bending is about 98,000 inzi.
(v) the overall section depth is about 30 ¨ 30 1/2 inches.
The center sill properties at the longitudinal station of the rear draft
stops, and shown
in Figure 4e, may be taken as a datum, and may be taken as being sufficiently
similar to the
prior art also to stand as a datum for prior art sectional properties at that
longitudinal station.
In the nomenclature used herein, the sectional properties of the center sill ¨
depth of section,
neutral axes, cross-sectional area, and second moment of area in flexure
(i.e., moment of
Inertia, I, and, correspondingly, flexural modulus El, where E is the Young's
modulus) are
discussed on the basis of the bottom flange taken in combination with the
center sill webs, and
will be understood as such in contrast to the sectional properties (i.e.,
depth of section, neutral
axes, cross-sectional area and second moment of area) of the car body
underframe 22 at the
corresponding section which are based on those same elements taken in
combination with the
side sills, center sill top cover plate (or top flange), deck sheeting, and
stringers, such as may
be. Reference to the area of the section is to the cross-sectional area of
metal, proportionate to
the weight of section per lineal foot (i.e., per running foot), rather than a
measure of enclosed
cross-sectional area. Taking for comparison the section in the middle of the
car, as shown in
Figures 4c and 4d, counting the cross-sectional area of the center sill webs,
124, 126 and the
bottom cover plate or bottom flange 122, there is a cross-sectional reduction
in area of the
center sill of roughly 1/5 (i.e., the area at mid span is less than 4/5 of the
datum cross-section),
or more, from the datum draft sill area of Figure 4e. In the prior art, as
symbolised by the fish-
Date Recue/Date Received 2021-04-19
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belly center sill of Figure 4f, the cross sectional area, depth, and second
moment of area in
resistance to vertical bending all increase from the datum to the center of
the car. By contrast,
in car 20, the sectional area, the depth of section, and the second moment of
area all decrease
when comparing the properties of the section at Figure 4f with the section at
Figures 4c and
4d. The properties at the mid-span longitudinal station of Figures 4c and 4d
are also a decrease
as compared to the properties at the truck center shown in Figures 4a and 4b.
This reduction
in section has a relatively small (less than 10%) effect on the Ixx second
moment of area of
total overall change in resistance to vertical bending once the racks (i.e.,
including the top
chords, posts, bracing, sheer panels and roof structure) have been installed.
As compared to the prior art fish belly, the reduction in center sill depth
may be of the
order of 2/5 or more in some embodiments, may be greater than half in other
embodiments,
and in some embodiments may be greater than 3/5.
As compared to the datum of Figure 4e, the reduction in depth of the center
sill may in
some embodiments be greater than 1/3, (i.e., the center section depth if less
than 2/3 of the
draft sill section depth) in other embodiments may be greater than 2/5, (i.e.,
the center section
minimum depth of section may be less than 3/5 of the draft sill depth of
section) and in still
other embodiments may be greater than 1/2. In one embodiment the reduction in
depth of
section may be as much as roughly ((17 - 7 1/2)/17), i.e., roughly 55%.
Similarly, as compared to the datum of Figure 4e, where the area of the draft
sill webs
and flange may be greater than 25 sq. in., the reduction in area to the mid-
span location in some
embodiments is greater than 1/5 (i.e., sectional area is less than 4/5 of
datum area), may in
some embodiments be greater than 1/4 (i.e., sectional area is less than 3/4 of
datum area), may in
other embodiments be greater than 1/3 (i.e., sectional area is less than 2/3
of datum area), and
may in one embodiment be approximately as much as 3/8 (i.e., the remaining
area is as little
as 5/8 of the datum area).
Unlike the prior art, the depth of section of central portion 40 of center
sill 30 of car 20
is less than the depth of section of the corresponding side sill at the same
mid-span longitudinal
station (e.g., the car central mid-section). Unlike the prior art fish-bellied
car, the cross-bearers
in the central portion of the car do not extend lower than the side sill
bottom flange, and the
flanges of those cross-bearers are carried substantially level with and flush
with, the bottom
cover plate of the center sill. The difference in second moment of area of the
underframe
section itself may be substantial. That is, as compared to the prior art datum
of about 8000 inzi,
Date Recue/Date Received 2021-04-19
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the embodiment shown and described may have less than half the second moment
of area, i.e.,
less than 4000 inzi. In one embodiment it is less than 2500 inzi, and may be
about 1500 ¨ 1600
inzi. This is not merely a quantitative change. Rather it is a qualitative
change. In the prior art
the center sill has a primacy of importance as the principle element of the
underframe. In the
car as shown and described, the reliance on the center sill is reduced as
compared to the side
sills, and greater reliance is placed on the housing superstructure. The
underframe as described
is manufactured, and the rack structure is mounted to the underframe
subsequently, either at
the location of fabrication of the underframe or at another location to which
the underframe
has been delivered. The underframe is not, by itself, intended to support the
vertical loads of
a fully-laded car.
When the replaceable rack structure of posts and braces and top chords is in
place, the
high longitudinal members act as chords of a truss more than 10 ft. distant
from the side sills.
This deep truss structure provides the car with the resistance to vertical
bending required when
carrying lading in service. As noted above, the underframe is intended to
define, and to be,
permanent structure of the autorack car, whereas the racks may have one third
the life of the
underframe. That is, the underframe may be provided with a first set of racks
when new, and
then with a further two sets of replacement racks during the lifetime of the
car.
Although the description provided herein is made in the context of the single
unit
autorack car shown in Figure la, it is also applicable to car unit bodies and
underframes of
individual body units of multiple-unit articulated autorack cars in which the
top flange of the
center sill cover plate, and the deck sheeting, descends to a diminished
height in the middle of
the car body, but is raised at the ends over the truck or trucks such as may
be, while the bottom
flange of the center sill is carried at a constant or substantially constant
height without being
kinked.
Further, although car 20 as shown is a tri-level car, (i.e., it has three
lading-transporting
decks, namely the main (or lower) deck, the middle deck and the top deck) it
could also have
the form of a bi-level car. It may be noted that a tri-level autorack car may
employ a so-called
low-profile truck with 28" diameter wheels and a reduced height center plate
bowl. The height
of the draft sill portion of the center sill is determined by the requirements
for interchange
service, namely that the center-line height of the coupler be 34 1/2 inches
above TOR for a new
unladen car with new wheels. In a tri-level car the top flange of the draft
sill is therefore higher
than the adjacent end deck over which vehicles are loaded by roughly 2 ¨ 4
inches. Further,
in a tri-level car the height of the center sill top flange is reduced between
the truck centers.
Date Recue/Date Received 2021-04-19
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Over that portion of the car, the top flange of the center sill may be defined
by the main deck
floor sheet.
In a bi-level car, (i.e., a car having a main deck and a single upper deck)
the trucks may
have the more common 33" diameter wheels, and may not be low-profile trucks.
In those cars
the end deck portion and the draft sill top flange may be carried flush with
each other. Further,
the top flange of the center sill may not have the dip, or depression, or
reduction in height
between the trucks found in the tri-level car. Rather the main deck, which may
define the top
flange of the center sill, may be carried at a constant, level (or
substantially level) height from
end to end of the car.
By making the center sill in the manner described, the center sill structure
may be
simplified, manufacture of that structure may be simplified, and the unladen
weight of the car
may be reduced. Any one of these things might be considered desirable. Given
that the
resistance to bending of the autorack car is greatly reduced unless a set of
racks is in place, the
underframe is not intended to carry lading or to operate in revenue service,
without a set of
racks installed.
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.
Date Recue/Date Received 2021-04-19
