Note: Descriptions are shown in the official language in which they were submitted.
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RAIL ROAD CAR TRUCK WITH BEARING ADAPTER AND METHOD
Field of the Invention
This invention relates to the field of rail road cars, and, more particularly,
to the
field of three piece rail road car trucks for rail road cars.
Background of the Invention
Rail road cars in North America commonly employ double axle swivelling trucks
known as "three piece trucks" to permit them to roll along a set of rails. The
three piece
terminology refers to a truck bolster and pair of first and second sideframes.
In a three
piece truck, the truck bolster extends cross-wise relative to the sideframes,
with the ends
of the truck bolster protruding through the sideframe windows. Forces are
transmitted
between the truck bolster and the sideframes by spring groups mounted in
spring seats in
the sideframes.
One general purpose of a resilient suspension system may tend to be to reduce
force transmission to the car body, and hence to the lading. This may apply to
very stiff
suspension systems, as suitable for use with coal and grain, as well as to
relatively soft
suspension systems such as may be desirable for more fragile goods, such as
rolls of
paper, automobiles, shipping containers fruit and vegetables, and white goods.
One determinant of overall ride quality is the dynamic response to lateral
perturbations. That is, when there is a lateral perturbation at track level,
the rigid steel
wheelsets of the truck may be pushed sideways relative to the car body.
Lateral
perturbations may arise for example from uneven track, or from passing over
switches or
from turnouts and other track geometry perturbations. When the train is moving
at speed,
the time duration of the input pulse due to the perturbation may be very
short.
The suspension system of the truck reacts to the lateral perturbation. It is
generally desirable for the force transmission to be relatively low. High
force
transmissibility, and corresponding high lateral acceleration, may tend not to
be
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advantageous for the lading. This is particularly so if the lading includes
relatively
fragile goods. In general, the lateral stiffness of the suspension reflects
the combined
displacement of (a) the sideframe between (i) the pedestal bearing adapter and
(ii) the
bottom spring seat (that is, the sideframes swing laterally as a pendulum with
the pedestal
bearing adapter being the top pivot point for the pendulum); and (b) the
lateral deflection
of the springs between (i) the lower spring seat in the sideframe and (ii) the
upper spring
mounting against the underside of the truck bolster, and (c) the moment and
the
associated transverse shear force between the (i) spring seat in the sideframe
and (ii) the
upper spring mounting against the underside of the truck bolster.
In a conventional rail road car truck, the lateral stiffness of the spring
groups is
sometimes estimated as being approximately 1/2 of the vertical spring
stiffness. Thus the
choice of vertical spring stiffness may strongly affect the lateral stiffness
of the
suspension. The vertical stiffness of the spring groups may tend to yield a
vertical
deflection at the releasable coupler from the light car (i.e., empty)
condition to the fully
laden condition of about 2 inches. For a conventional grain or coal car
subject to a
286,000 lbs., gross weight on rail limit, this may imply a dead sprung load of
some
50,000 lbs., and a live sprung load of some 220,000 lbs., yielding a spring
stiffness of 25
¨ 30,000 lbs./in., per spring group (there being, typically, two groups per
truck, and two
trucks per car). This may yield a lateral spring stiffness of 13 ¨ 16,000
lbs./in per spring
group. It should be noted that the numerical values given in this background
discussion
are approximations of ranges of values, and are provided for the purposes of
general
order-of-magnitude comparison, rather than as values of a specific truck.
The second component of stiffness relates to the lateral deflection of the
sideframe itself. In a conventional truck, the weight of the sprung load can
be idealized
as a point load applied at the center of the bottom spring seat. That load is
carried by the
sideframe to the pedestal seat mounted on the bearing adapter. The vertical
height
difference between these two points may be in the range of perhaps 12 to 18
inches,
depending on wheel size and sideframe geometry. For the general purposes of
this
description, for a truck having 36 inch wheels, 15 inches (+/-) might be taken
as a
roughly representative height.
The pedestal seat may typically have a flat surface that bears on an upwardly
crowned surface on the bearing adapter. The crown may typically have a radius
of
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curvature of about 60 inches, with the center of curvature lying below the
surface (i.e.,
the surface is concave downward).
When a lateral shear force is imposed on the springs, there is a reaction
force in
the bottom spring seat that will tend to deflect the sideframe, somewhat like
a pendulum.
When the sideframe takes on an angular deflection in one direction, the line
of contact of
the flat surface of the pedestal seat with the crowned surface of the bearing
adapter will
tend to move along the arc of the crown in the opposite direction. That is, if
the bottom
spring seat moves outboard, the line of contact will tend to move inboard.
This motion is
resisted by a moment couple due to the sprung weight of the car on the bottom
spring
seat, acting on a moment arm between (a) the line of action of gravity at the
spring seat
and (b) the line of contact of the crown of the bearing adapter. For a 286,000
lbs. car the
apparent stiffness of the sideframe may be of the order of 18,000 ¨ 25,000
lbs./in,
measured at the bottom spring seat. That is, the lateral stiffness of the
sideframe (i.e., the
pendulum action by itself) can be greater than the (already relatively high)
lateral
stiffness of the spring group in shear, and this apparent stiffness is
proportional to the
total sprung weight of the car (including lading). When taken as being
analogous to two
springs in series, the overall equivalent lateral spring stiffness may be of
the order of
8,000 lbs./in. to 10,000, per sideframe. A car designed for lesser weights may
have softer
apparent stiffness. This level of stiffness may not always yield as smooth a
ride as may
be desired.
There is another component of spring stiffness due to the unequal compression
of
the inside and outside portions of the spring group as the bottom spring seat
rotates
relative to the upper spring group mount under the bolster. This stiffness,
which is
additive to (that is, in parallel with) the stiffness of the sideframe, can be
significant, and
may be of the order of 3000 - 3500 lbs./in per spring group, depending on the
stiffness of
the springs and the layout of the group. Other second and third order effects
are
neglected for the purpose of this description. The total lateral stiffness for
one sideframe,
including the spring stiffness, the pendulum stiffness and the spring moment
stiffness, for
a S2HD 110 Ton truck may be about 9200 lbs/inch per side frame.
It has been observed that it may be preferable to have springs of a given
vertical
stiffness to give certain vertical ride characteristics, and a different
characteristic for
lateral perturbations. In particular, a softer lateral response may be desired
at high speed
(greater than about 50 m.p.h) and relatively low amplitude to address a truck
hunting
concern, while a different spring characteristic may be desirable to address a
low speed
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(roughly 10 ¨ 25 m.p.h) roll characteristic, particularly since the overall
suspension
system may have a roll mode resonance lying in the low speed regime.
An alternate type of three piece truck is the "swing motion" truck. One
example
of a swing motion truck is shown at page 716 in the 1980 Car and Locomotive
Cyclopedia (1980, Simmons-Boardman, Omaha). This illustration, with captions
removed, is the basis of Figures la, lb and lc, herein, labelled "Prior Art".
Since the
truck has both lateral and longitudinal axes of symmetry, the artist has only
shown half
portions of the major components of the truck. The particular example
illustrated is a
swing motion truck produced by National Castings Inc., more commonly referred
to as
"NACO". Another example of a NACO Swing Motion truck is shown at page 726 of
the
1997 Car and Locomotive Cyclopedia (1997, Simmons-Boardroom, Omaha). An
earlier
swing motion three piece truck is shown and described in US Patent 3,670,660
of Weber
et al., issued June 20, 1972.
In a swing motion truck, the sideframe is mounted as a "swing hanger" and acts
much like a pendulum. In contrast to the truck described above, the bearing
adapter has
an upwardly concave rocker bearing surface, having a radius of curvature of
perhaps 10
inches and a center of curvature lying above the bearing adapter. A pedestal
rocker seat
nests in the upwardly concave surface, and has itself an upwardly concave
surface that
engages the rocker bearing surface. The pedestal rocker seat has a radius of
curvature of
perhaps 5 inches, again with the center of curvature lying upwardly of the
rocker.
In this instance, the rocker seat is in dynamic rolling contact with the
surface of
the bearing adapter. The upper rocker assembly tends to act more like a hinge
than the
shallow crown of the bearing adapter described above. As such, the pendulum
may tend
to have a softer, perhaps much softer, response than the analogous
conventional
sideframe. Depending on the geometry of the rocker, this may yield a sideframe
resistance to lateral deflection in the order of 1/4 (or less) to about 1/2 of
what might
otherwise be typical. If combined in series with the spring group stiffness,
it can be seen
that the relative softness of the pendulum may tend to become the dominant
factor. To
some extent then, the lateral stiffness of the truck becomes less strongly
dependent on the
chosen vertical stiffness of the spring groups at least for small
displacements.
Furthermore, by providing a rocking lower spring seat, the swing motion truck
may tend
to reduce, or eliminate, the component of lateral stiffness that may tend to
arise because
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of unequal compression of the inboard and outboard members of the spring
groups, thus
further softening the lateral response.
In the truck of US Patent 3,670,660 the rocking of the lower spring seat is
limited
to a range of about 3 degrees to either side of center, and a transom extends
between the
sideframes, forming a rigid, unsprung, lateral connecting member between the
rocker
plates of the two sideframes. In this context, "unsprung" refers to the
transom being
mounted to a portion of the truck that is not resiliently isolated from the
rails by the main
spring groups.
When the three degree condition is reached, the rockers "lock-up" against the
side
frames, and the dominant lateral displacement characteristic is that of the
main spring
groups in shear, as illustrated and described by Weber. The lateral, unsprung,
sideframe
connecting member, namely the transom, has a stop that engages a downwardly
extending abutment on the bolster to limit lateral travel of the bolster
relative to the
sideframes. This use of a lateral connecting member is shown and described in
US Patent
3,461,814 of Weber, issued March 7, 1967. As noted in US Patent 3,670,660 the
use of a
spring plank had been known, and the use of an abutment at the level of the
spring plank
tended to permit the end of travel reaction to the truck bolster to be
transmitted from the
sideframes at a relatively low height, yielding a lower overturning moment on
the wheels
than if the end-of-travel force were transmitted through gibs on the truck
bolster from the
sideframe columns at a relatively greater height. The use of a spring plank in
this way
was considered advantageous.
In Canadian Patent 2,090,031, (issued April 15, 1997 to Weber et al.,) noting
the
advent of lighter weight, low deck cars, Weber et al., replaced the transom
with a lateral
rod assembly to provide a rigid, unsprung connection member between the
platforms of
the rockers of the lower spring seats. One type of car in which relative
lightness and a
low main deck has tended to be found is an Autorack car.
For the purposes of rapid estimation of truck lateral stiffness, the following
formula can be used:
ktruck ¨ 2 x I (ksideframeil + (kspring shearYirj
where
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ksideframe = [kpendulum kspring moment]
kspring shear = The lateral spring constant for the spring group
in shear.
kpendulum = The force required to deflect the pendulum per
unit of deflection,
as measured at the center of the bottom spring seat.
kspring moment = The force required to deflect the bottom spring seat per unit
of
sideways deflection against the twisting moment caused by the
unequal compression of the inboard and outboard springs.
In a pure pendulum, the relationship between weight and deflection is
approximately linear for small angles of deflection, such that, by analogy to
a spring in
which F = la, a lateral constant (for small angles) can be defined as k
pendulum W / L,
where k is the lateral constant, W is the weight, and L is the pendulum
length. Further,
for the purpose of rapid comparison of the lateral swinging of the sideframes,
an
approximation for an equivalent pendulum length for small angles of deflection
can be
defined as Leg = W / kpendulum- In this equation W represents the sprung
weight borne by
that sideframe, typically 'A of the total sprung weight for a symmetrical car.
For a
conventional truck, Leg may be of the order of about 3 or 4 inches. For a
swing motion
truck, Leg may be of the order of about 10 to 15 inches.
It is also possible to define the pendulum lateral stiffness (for small
angles) in
terms of the length of the pendu[um, the radius of curvature of the rocker,
and the design
weight carried by the pendulum according to the formula:
kpendulum = (FlateraliSlateral) = (W/Lpendulum)[(Rcurvature/Lpendulum) + 1]
where:
kpendulum = the lateral stiffness of the pendulum
Flitter& = the force per unit of lateral deflection
81atera1 = a unit of lateral deflection
W = the weight borne by the pendulum
Lpendulum = the length of the pendulum, being the vertical distance from the
contact
surface of the bearing adapter to the bottom spring seat
Rcurvature = the radius of curvature of the rocker surface
Following from this, if the pendulum stiffness is taken in series with the
lateral
spring stiffness, then the resultant overall lateral stiffness can be
obtained. Using this
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-.A9RAtiT ,xvr
d.r.RiVr=Wit-m.
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number in the denominator, and the design weight in the numerator yields a
length,
effectively equivalent to a pendulum length if the entire lateral stiffness
came from an
equivalent pendulum according to ',resultant W / klateral total
For a conventional truck with a 60 inch radius of curvature rocker, and stiff
suspension, this length, Lresultarrt may be of the order of 6 ¨ 8 inches, or
thereabout.
So that the present invention may better be understood by comparison, in the
prior
art illustration of Figures la, lb, and lc, a NACO swing motion truck is
identified
generally as A20. Inasmuch as the truck is symmetrical about the truck center
both from
side-to-side and lengthwise, the artist has shown only half of the bolster,
identified as
A22, and half of one of the sideframes, identified as A24.
In the customary manner, sideframe A24 has defined in it a generally
rectangular
window A26 that admits one of the ends of the bolster A28. The top boundary of
window A26 is defined by the sideframe arch, or compression member identified
as top
chord member A30, and the bottom of window A26 is defined by a tension member,
identified as bottom chord A32. The fore and aft vertical sides of window A26
are
defined by sideframe columns A34.
At the swept up ends of sideframe A24 there are sideframe pedestal fittings
A38
which each accommodate an upper rocker identified as a pedestal rocker seat
A40, that
engages the upper surface of a bearing adapter A42. Bearing adapter A42 itself
engages
a bearing mounted on one of the axles of the truck adjacent one of the wheels.
A rocker
seat A40 is located in each of the fore and aft pedestals, the rocker seats
being
longitudinally aligned such that the sideframe can swing transversely relative
to the
rolling direction of the truck A20 generally in what is referred to as a
"swing hanger"
arrangement.
The bottom chord of the sideframe includes pockets A44 in which a pair of fore
and aft lower rocker bearing seats A46 are mounted. The lower rocker seat A48
has a
pair of rounded, tapered ends or trunnions A50 that sit in the lower rocker
bearings A48,
and a medial platform A52. An array of four corner bosses A54 extend upwardly
from
platform A52.
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An unsprung, lateral, rigid connecting member in the nature of a spring plank,
or
transom A60 extends cross-wise between the sideframes in a spaced apart,
underslung,
relationship below truck bolster A22. Transom A60 has an end portion that has
an array
of four apertures A62 that pick up on bosses A54. A grouping, or set of
springs A64
seats on the end of the transom, the corner springs of the set locating above
bosses A54.
The spring group, or set A64, is captured between the distal end of bolster
A22
and the end portion of transom 460. Spring set A64 is placed under compression
by the
weight of the rail car body and lading that bears upon bolster A22 from above.
In
consequence of this loading, the end portion of transom A60, and hence the
spring set,
are carried by platform A54. The reaction force in the springs has a load path
that is
carried through the bottom rocker A70 (made up of trunnions A50 and lower
rocker
bearings A48) and into the sideframe A22 more generally.
Friction damping is provided by damping wedges A72 that seat in mating bolster
pockets A74. Bolster pockets A74 have inclined damper seats A76. The vertical
sliding
faces of the friction damper wedges then ride up an down on friction wear
plates A80
mounted to the inwardly facing surfaces of the sideframe columns.
The "swing motion" truck gets its name from the swinging motion of the
sideframe on the upper rockers when a lateral track perturbation is imposed on
the
wheels. The reaction of the sideframes is to swing, rather like pendula, on
the upper
rockers. When this occurs, the transom and the truck bolster tend to shift
sideways, with
the bottom spring seat platfoini rotating on the lower rocker.
The upper rockers are inserts, typically of a hardened material, whose
rocking, or
engaging, surface A80 has a radius of curvature of about 5 inches, with the
center of
curvature (when assembled) lying above the upper rockers (i.e., the surface is
upwardly
concave).
As noted above, one of the features of a swing motion truck is that while it
may
be quite stiff vertically, and while it may be resistant to parallelogram
deformation
because of the unsprung lateral connection member, it may at the same time
tend to be
laterally relatively soft.
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Summary of the Invention
In one aspect of the present invention there is a bearing adapter having an
upwardly facing crown for engaging a bearing surface mounted in the pedestal
seat of a
side frame of a three-piece railroad car truck. The upwardly facing crown has
a radius of
curvature of less the 30 inches.
In another feature of the invention, the upwardly facing crown has a radius of
curvature in the range of 3 to 24 inches. In another feature of the invention,
the upwardly
facing crown has a radius in the range of 4 to 15 inches. In another feature
of the
invention, the crown has a radius of curvature in the range of 4 to 10 inches.
In another
feature of the invention, the radius of curvature is in the range of 4 to 6
inches. In
another feature of the invention, the radius is in about 5 inches.
In another aspect of the invention, there is a method of retro-fitting a three
piece
rail road car truck comprising the steps of (a) removing an existing bearing
adapter; (b)
replacing the existing bearing adapter with a replacement bearing adapter
having an
upwardly facing crown for contacting an existing bearing seat, the crown of
the
replacement bearing adapter has a radius of curvature of less than 30 inches.
In an additional feature of the invention, the step of replacing the existing
bearing
adapter includes installing a replacement bearing adapter having a crown
radius of
curvature of less than 24 inches. In an additional feature of the invention,
the step of
replacing the existing bearing adapter includes installing a replacement
bearing adapter
having a crown radius of curvature of less than 15 inches. In an additional
feature of the
invention, the step of replacing the existing bearing adapter includes
installing a
replacement bearing adapter having a crown radius of curvature in the range of
3 to 10
inches. In an additional feature of the invention, the step of replacing the
existing bearing
adapter includes installing a replacement bearing adapter having a crown
radius of
curvature in the range of 4 to 6 inches. In an additional feature of the
invention, the step
of replacing the existing bearing adapter includes installing a replacement
bearing adapter
having a crown radius of curvature of about 5 inches.
In another additional feature, the method includes the step of widening the
lateral
travel range of the truck bolster relative to the sideframe. In another
additional feature of
the invention, the step of widening includes the step of removing at least one
existing gib,
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and installing one of (a) said gib and (b) a new replacement gib, in a
position allowing
greater lateral travel of said truck bolster than formerly.
In another additional feature, the method includes the step of widening the
lateral
travel range of the truck bolster relative to the side frame by removing
existing inboard
and outboard gibs, and installing new, more widely spaced inboard and outboard
gibs. In
another additional feature of the invention, the step of widening includes the
step of
allowing at least 1" travel to either side of a central position of said truck
bolster relative
to said side frame. In another additional feature of the invention, the step
of widening
includes the step of allowing at least 1 ¨ 1/4 inches of lateral travel to
either side of a
central position.
In another feature, the method includes the step of replacing the existing
truck
bolster with a new truck bolster having damper pockets arranged to peimit a
four-
cornered damper arrangement, and includes the step of providing four dampers
for said
four-cornered arrangement. In an additional feature, said method includes the
step of
widening the side frame column bearing surfaces to accommodate a four-cornered
damper arrangement.
In yet another additional feature, the truck is free of unsprung lateral
bracing
between the sideframes. In still another additional feature, the truck is free
of a transom.
In still yet another additional feature, each of the sideframes has a rigid
spring seat, and
respective groups of springs are mounted therein between the spring seat and a
respective
end of the truck bolster. In still another additional feature, each of the
friction dampers
are sprung on springs of the spring groups. In a further additional feature,
each of the
sideframes has a rocking spring seat. In still a further additional feature,
each of the
sideframes has an equivalent pendulum length, Leg, in the range of 6 to 15
inches.
In yet a further additional feature, a first spring group is mounted between
the first
end of the truck bolster and the first side frame. A second spring group is
mounted
between the second end of the truck bolster and the second side frame. Each of
the first
and second spring groups has a vertical spring rate constant k that is in the
range of
12,000 to 18,000 Lbs./in per group.
In another aspect of the invention there is a swing motion rail road car
truck. The
truck has a truck bolster having a first end and a second end and a pair of
first and second
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sideframes. Each of the sideframes accommodates an end of the truck bolster,
and has a
spring seat for receiving a spring group. The truck has a first spring group
and a second
spring group. The first spring group is mounted in the spring seat of the
first sideframe.
The second spring group is mounted in the spring seat of the second sideframe.
The
truck bolster is mounted cross-wise relative to the sideframes. The first end
of the truck
bolster is supported by the first spring group. The second end of the truck
bolster is
supported by the second spring group. The first and second sideframes each
have swing
hanger rocker mounts for engaging first and second axles. The rocker mounts
are
operable to permit cross-wise swinging motion of the sideframes. The truck is
free of
lateral cross-bracing between the sideframes. In an additional feature of that
aspect of the
invention, the spring seats are rigidly mounted to the sideframes.
In another additional feature, a set of biased members, operable to resist
parallelogram deformation of the truck, is mounted to act between each end of
the truck
bolster and the sideframe associated therewith. One of the sets of biased
members
includes first and second biased members. The first biased member is mounted
to act at a
laterally inboard location relative to the second biased member. In still
another additional
feature, each of the sets of biased members includes third and fourth biased
members.
The third biased member is mounted transversely inboard of the fourth biased
member.
In yet another additional feature, the biased members are friction dampers.
In still yet another additional feature, a set of friction dampers is mounted
to act
between each end of the truck bolster and the sideframe associated therewith.
One of the
sets of friction dampers includes first and second friction dampers. The first
friction
damper is mounted to act at a laterally inboard location relative to the
second friction
damper. In another additional feature, each of the sets of friction dampers
includes third
and fourth friction dampers. The third friction damper is mounted transversely
inboard of
the fourth friction damper. In a further additional feature, the friction
dampers are
individually biased by springs of the spring groups. In still a further
additional feature,
each of the side frames has an equivalent pendulum length Leg in the range of
6 to 15
inches. In yet a further additional feature, each of the spring groups has a
vertical spring
rate constant of less than 15,000 Lbs./in.
In still yet a further additional feature, a first set of friction dampers is
mounted to
act between the first end of the truck bolster and the first sideframe. A
second set of
friction dampers is mounted to act between the second end of the truck bolster
and the
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..
second sideframe. The first set of friction dampers includes at least four
individually
sprung friction dampers. In another additional feature, the friction dampers
are mounted
in a four corner arrangement. In yet another additional feature, the friction
dampers
include a first inboard friction damper, a second inboard friction damper, a
first outboard
friction damper and a second outboard friction damper. The first and second
inboard
friction dampers are mounted transversely inboard relative to the first and
second
outboard friction dampers.
In still yet another additional feature, each of the sideframes has a rigid
spring
seat, and respective groups of springs are mounted therein between the spring
seat and a
respective end of the truck bolster. In a further additional feature, each of
the friction
dampers are sprung on springs of the spring groups. In still a further
additional feature,
each of the sideframes has a rocking spring seat. In yet a further additional
feature, each
of the sideframes has an equivalent pendulum length, Leg, in the range of 6 to
15 inches.
In still yet a further additional feature, each of the first and second spring
groups has a
vertical spring rate constant k that is less than 15,000 Lbs./in per group.
Brief Description of The Illustrations
The principles of the invention may better be understood with reference to the
accompanying figures provided by way of illustration of an exemplary
embodiment, or
embodiments, incorporating those principles, and in which:
Figure la shows a prior art exploded partial view illustration of a swing
motion
truck based on the illustration shown at page 716 in the 1980 Car and
Locomotive Cyclopedia;
Figure lb shows a cross-sectional detail of an upper rocker assembly of the
truck
of Figure la;
Figure lc shows a cross-sectional detail of a lower rocker assembly of the
truck of
Figure la;
Figure 2a shows a swing motion truck as shown in Figure la, but lacking a
transom;
Figure 2b shows a sectional detail of an upper rocker assembly of the truck of
Figure 2a;
Figure 2c shows a cross-sectional detail of a bottom spring seat of the truck
of
Figure 2a;
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Figure 3a shows a swing motion truck having an upper rocker as in the swing
motion truck of Figure la, but having a rigid spring seat, and being free of
a transom;
Figure 3b shows a cross-sectional detail of the upper rocker assembly of the
truck
of Figure 3a;
Figure 4 shows a swing motion truck similar to that of Figure 3a, but having
doubled bolster pockets and wedges;
Figure 5a shows an isometric view of an assembled swing motion truck similar
to
that of Figure 3a, but having a different spring and damper arrangement;
Figure 5b shows a top view of the truck of Figure 5a showing a 2 x 4 spring
arrangement;
Figure 5c shows the damper arrangement of the truck of Figure 5a;
Figure 5d shows a side view of the truck of Figure 5a;
Figure 6a shows an alternate bearing adapter for a rail road car truck such as
that
of Figure 2a, 3a, 4, 5a or 7a (below);
Figure 6b shows a profile of the bearing adapter of Figure Ga;
Figure 6c shows an alternate profile for a bearing adapter as in Figure 6a;
Figure 6d chows a further alternate profile for a bearing adapter as shown in
Figure 6a;
Figure 6e shows an alternate installation of bearing adapter;
Figure 6f shows a general installation relationship of any of the bearing
adapter
embodiments of Figures 6a to 6e;
Figure 7a shows an isometric view of an alternate railroad car truck to that
of Figure
5a;
Figure 7b shows a side view of the three piece truck of Figure 7a;
Figure 7c shows a top view of the three piece truck of Figure 7a;
Figure 7d shows an end view of the three piece truck of Figure 7a;
Figure 7e shows a schematic of a spring layout for the truck of Figure 7a;
Figure 8 shows car types having trucks as described herein;
Figure 9 shows a different group of car types having trucks as described
herein;
DETAILED DESCRIPTION OF THE INVENTION
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
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principles 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 are not necessarily to scale
and in
some instances proportions may have been exaggerated in order more clearly to
depict
certain features of the invention.
In terms of general orientation and directional nomenclature, for each of the
rail
road car trucks 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. The term lateral, or laterally outboard, refers to a distance
or
orientation relative to the longitudinal centerline of the railroad car, or
car unit. 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 axis perpendicular to the longitudinal
direction. Yawing is
angular motion about a vertical axis. Roll is angular motion about the
longitudinal axis.
This description relates to rail car trucks. 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 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. A "110 Ton" truck is a term sometimes used
for a
truck having a maximum weight on rail of 286,000 lbs.
This application refers to friction dampers, and multiple friction damper
systems.
There are several types of damper arrangement as shown at pages 715 - 716 of
the 1997
Car and Locomotive Encyclopedia. Double damper arrangements are shown and
described in my co-pending US Patent application, filed contemporaneously
herewith and
entitled "Rail Road Freight Car With Damped Suspension". Each of the
arrangements of
dampers shown at pp. 715 to 716 of the 1997 Car and Locomotive
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Encyclopedia can be modified according to the principles of my aforesaid co-
pending
application for "Rail Road Freight Car With Damped Suspension" to employ a
four
cornered, double damper arrangement of inner and outer dampers.
In the example of Figure 2a and 2b, a truck embodying an aspect of the present
invention is indicated as 10. Truck 10 differs from truck A20 of Figure la
insofar as it is
free of a rigid, unsprung lateral connecting member in the nature of unsprung
cross-
bracing such as a frame brace of crossed-diagonal rods, lateral rods, or a
transom (such as
transom A60) running between the rocker plates of the bottom spring seats of
the
opposed sideframes. Further, truck 10 employs gibs 12 to define limits to the
lateral
range of travel of the truck bolster 14 relative to the sideframe 16. In other
respects,
including the sideframe geometry and upper and lower rocker assemblies, truck
10 is
intended to have generally similar features to truck A20, although it may
differ in size,
pendulum length, spring stiffness, wheelbase, window width and window height,
and
damping arrangement. The determination of these values and dimensions may
depend on
the service conditions under which the truck is to operate.
As with other trucks described herein, it will be understood that since truck
10
(and trucks 20, 120, and 220, described below) are symmetrical about both
their
longitudinal and transverse axes, the truck is shown in partial section. In
each case,
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.
In Figures 3a and 3b, for example, a truck embodying an aspect of the present
invention is identified generally as 20. Inasmuch as truck 20 is symmetrical
about the
truck center both from side-to-side and lengthwise, the bolster, identified as
22, and the
sideframes, identified as 24 are shown in part. Truck 20 differs from truck
A20 of the
prior art, described above, in that truck 20 has a rigid spring seat rather
than a lower
rocker as in truck A20, as described below, and is free of a rigid, unsprung
lateral
connection member such as an underslung transom A60, a frame brace, or
laterally
extending rods.
Sideframe 24 has a generally rectangular window 26 that accommodates one of
the ends 28 of the bolster 22. The upper boundary of window 26 is defined by
the
sideframe arch, or compression member identified as top chord member 30, and
the
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bottom of window 26 is defined by a tension member identified as bottom chord
32. The
fore and aft vertical sides of window 26 are defined by sideframe columns 34.
The ends of the tension member sweep up to meet the compression member. At
each of the swept-up ends of sideframe 24 there are sideframe pedestal
fittings 38. Each
fitting 38 accommodates an upper rocker identified as a pedestal rocker seat
40. Pedestal
rocker seat 40 engages the upper surface of a bearing adapter 42. Bearing
adapter 42
engages a bearing mounted on one of the axles of the truck adjacent one of the
wheels. A
rocker seat 40 is located in each of the fore and aft pedestal fittings 38,
the rocker seats
40 being longitudinally aligned such that the sideframe can swing transversely
relative to
the rolling direction of the truck in a "swing hanger" arrangement.
Bearing adapter 42 has a hollowed out recess 43 in its upper surface that
defines a
bearing surface 43 for receiving rocker seat 40. Bearing surface 43 is formed
on a radius
of curvature RI. The radius of curvature R1 is preferably in the range of less
than 25
inches, and is preferably in the range of 8 to 12 inches, and most preferably
about 10
inches with the center of curvature lying upwardly of the rocker seat. The
lower face of
rocker seat 40 is also formed on a circular arc, having a radius of curvature
R2 that is less
than the radius of curvature R1 of recess 43. R2 is preferably in the range of
V4 to 3/4 as
large as R1, and is preferably in the range of 3 ¨ 10 inches, and most
preferably 5 inches
when R1 is 10 inches, i.e., R2 is one half of R1. Given the relatively small
angular
displacement of the rocking motion of R2 relative to R1 (typically less than
+1- 10
degrees) the relationship is one of rolling contact, rather than sliding
contact.
The bottom chord or tension member of sideframe 24 has a basket plate, or
lower
spring seat 44 rigidly mounted to bottom chord 32, such that it has a rigid
orientation
relative to window 26, and to sideframe 24 in general. That is, in contrast to
the lower
rocker platform of the prior art swing motion truck A20 of Figure la, as
described above,
spring seat 44 is not mounted on a rocker, and does not rock relative to
sideframe 24.
Although spring seat 44 retains an array of bosses 46 for engaging the corner
elements
54, namely springs 54 and 55 (inboard), 56 and 57 (outboard) of a spring set
48, there is
no transom mounted between the bottom of the springs and seat 44. Seat 44 has
a
peripheral lip 52 for discouraging the escape of the bottom ends the of
springs.
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The spring group, or spring set 48, is captured between the distal end 28 of
bolster
22 and spring seat 44, being placed under compression by the weight of the
rail car body
and lading that bears upon bolster 22 from above.
Friction damping is provided by damping wedges 62 that seat in mating bolster
pockets 64 that have inclined damper seats 66. The vertical sliding faces 70
of the
friction damper wedges 62 then fide up and down on friction wear plates 72
mounted to
the inwardly facing surfaces of sideframe columns 34. Angled faces 74 of
wedges 62
ride against the angled face of seat 66. Bolster 22 has inboard and outboard
gibbs 76, 78
respectively, that bound the lateral motion of bolster 22 relative to
sideframe columns 34.
This motion allowance may advantageously be in the range of +/- 1 - 1/8 to 1 -
3/4
inches, and is most preferably in the range of 1 - 3/16 to 1 - 9/16 inches,
and can be set,
for example, at 1 - 1/2 inches or 1 - 1/4 inches of lateral travel to either
side of a neutral,
or centered, position when the sideframe is undeflected.
As in the prior art swing motion truck A20, a spring group of 8 springs in a
3:2:3
arrangement is used. Other configurations of spring groups could be used, such
as these
described below.
In the embodiment of Figure 4, a truck 120 is substantially similar to truck
20, but
differs insofar as truck 120 has a bolster 122 having double bolster pockets
124 126 on
each face of the bolster at the outboard end. Bolster pockets 124, 126
accommodate a
pair of first and second, laterally inboard and laterally outboard friction
damper wedges
128, 129 and 130, 131, respectively. Wedges 128, 129 each sit over a first,
inboard
comer spring 132, 133, and wedges 130, 131 each sit over a second, outboard
comer
spring 134, 135. In this four corner arrangement, each damper is individually
sprung by
one or another of the springs in the spring group. The static compression of
the springs
under the weight of the car body and lading tends to act as a spring loading
to bias the
damper to act along the slope of the bolster pocket to force the friction
surface against the
sideframe. As such, 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. A middle end spring 136 bears
on the
underside of a land 138 located intermediate bolster pockets 124 and 126. The
top ends
of the central row of springs, 140, seat under the main central portion 142 of
the end of
bolster 122.
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The lower ends of the springs of the entire spring group, identified generally
as
144, seat in the lower spring seat 146. Lower spring seat 146 has the layout
of a tray with
an upturned rectangular peripheral lip. Lower spring seat 146 is rigidly
mounted to the
lower chord 148 of sideframe 122. In this case, spring group 144 has a 3 rows
x 3
columns layout, rather than the 3:2:3 arrangement of truck 20. A 3 x 5 layout
as shown
in Figure 7e could be used, as could other alternate spring group layouts.
Truck 120 is
free of any rigid, unsprung lateral sideframe connection members such as
transom A60.
It will be noted that bearing plate 150 mounted to vertical sideframe columns
152
is significantly wider than the corresponding bearing plate 72 of truck 20 of
Figure 3a.
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 1 11/2
(+/-) 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, plate 150 has the width of three coils, plus allowance
to
accommodate 1 1/2 (+/-) inches of travel to either side. Plate 150 is
significantly wider
than the through thickness of the sideframes more generally, as measured, for
example, at
the pedestals.
Damper wedges 128 and 130 sit over 44 % (+/-) of the spring group i.e., 4/9 of
a 3
rows x 3 columns group as shown in Figure 4, whereas wedges 70 only sat over
2/8 of
the 3:2:3 group in Figure 3a. For the same proportion of vertical damping,
wedges 128
and 130 may tend to have a larger included angle (i.e., between the wedge
hypotenuse
and the vertical face for engaging the friction wear plates on the sideframe
columns 34.
For example, if the included angle of friction wedges 72 is about 35 degrees,
then,
assuming a similar overall spring group stiffness, and single coils, the
corresponding
angle of wedges 128 and 130 could advantageously be in the range of 50 ¨ 65
degrees, or
more preferably about 55 degrees.
In a 3 x 5 group such as group 276 of truck 270 of Figures 7a to 7f, for coils
of
equal stiffness, the wedge angle may tend to be in the 35 to 45 degree range,
with a
preferred value of about 40 degrees. The specific angle will be a function of
the specific
spring stiffnesses and spring combinations actually employed. Truck 270 has a
bolster
272, a side frame 274, a spring group 276, and a damper arrangement 278. The
spring
group has a 5 x 3 arrangement, with the dampers being in a spaced arrangement
generally
as shown in Figure 4, (i.e., a four cornered damper arrangement, where the
opposed
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bearing surfaces on the sideframe columns are planar and parallel) and having
a primary
damper angle that may tend to be somewhat sharper given the smaller proportion
of the
total spring group that works under the dampers (i.e., 4 / 15 as opposed to 4
/ 9 or 4 / 8,
subject to allowances for differences in coil stiffness).
In one embodiment of truck 270, such as might be used for an end truck of an
articulated rail road car, there may be a 5 x 3 spring group arrangement, the
spring group
including 11 coils each having a spring rate in the range of 550 ¨ 650 lb./in,
and most
preferably about 580 lb./in; and 4 springs (under the dampers, in a four
corner
arrangement) having a spring rate in the range of 450 ¨ 550 lb./in, most
preferably about
500 lb./in, for which the dampers are driven by 20 ¨ 25 % of the force of the
spring
group, preferably about 24 %. The dampers may have a primary angle of 35 - 45
deg.,
preferably about 40 deg. In this preferred end truck embodiment, the overall
group
vertical spring rate is in the range of 8,000 to 8,500 lb./in., in particular
about 8380 lb./in.
In another embodiment of truck 270, such as might be used in an internal truck
of
an articulated rail road car, there may be a 5 x 3 spring group arrangement in
which the
spring group may include 11 outer springs having a spring rate of about 550 ¨
650 lb./in.,
and most preferably about 580 lb./in; 4 springs (under the dampers, in a four
corner
arrangement) having a spring rate in the range of 550 ¨ 650 lb./in, and most
preferably
about 600 lb./in.; and six inner coils having a spring rate in the range of
250 ¨ 300 lb./in.,
most preferably about 280 lb./in. The overall spring rate for the 5 x 3 group
is in the
range of 10,000 ¨ 11,000 lb./in., and most preferably about 10,460 lb./in. The
dampers
are driven by about 20 ¨ 25 % of the total force of the spring group,
preferably about 23
%. The dampers have a primary angle in the range of 35 ¨ 35 degrees,
preferably about
40 degrees.
It will be appreciated that the values and ranges given for truck 270 depend
on the
expected empty weight of the railcar, the expected lading, the natural
frequency range to
be achieved, the amount of damping to be achieved, and so on, and may
accordingly vary
from the preferred ranges and values indicated above. In another embodiment,
the spring
group may be very stiff, as for carrying rolls of paper, and may seek to
provide a
relatively stiff vertical support while also providing a relatively soft
lateral response.
The use of spaced apart pairs of dampers 128, 130 may tend to give a larger
moment aim, as indicated by dimension "2M", for resisting parallelogram
defoiniation of
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truck 120 more generally as compared to trucks 20 or A20. Parallelogram
deforniation
may tend to occur, for example, during the "truck hunting" phenomenon that has
a
tendency to occur in higher speed operation.
Placement of doubled dampers in this way may tend to yield a greater
restorative
"squaring" force to return the truck to a square orientation than for a single
damper alone,
as in truck 20. That is, in parallelogram deformation, or lozenging, the
differential
compression of one diagonal pair of springs (e.g., inboard spring 132 and
outboard spring
135 may be more pronouncedly compressed) relative to the other diagonal pair
of springs
(e.g., inboard spring 133 and outboard spring 134 may be less pronouncedly
compressed
than springs 132 and 135) tends to yield a restorative moment couple acting on
the
sideframe wear 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) and thus may tend to discourage the lozenging or
parallelogramming,
noted by Weber.
Another embodiment of multiple damper truck 220 is shown in Figures 5a, 5b, 5c
and 5d. Truck 220 has a wheel set of four wheels 221 and two axles 223. Truck
220 is
substantially similar to truck 120, but differs insofar as truck 220 has a
bolster 222 having
single bolster pockets 225, 226 on opposites sides of the outboard end portion
of the
bolster, each being of enlarged width, such as double the width of the single
pockets
shown in Figure 3a, to accommodate a pair of first and second, inboard and
outboard
friction damper wedges 228, 230, (or 229, 231, opposite side) in side-by-side
independently displaceable sliding relationship relative not only to the seat
of the pocket,
but also with respect to each other. In this instance the spring group,
indicated as 232,
has a 2 rows x 4 columns layout, as seen most clearly in Figure 5b. Wedges
228, 230
each sit over a first corner spring 234, 236 and wedges 229, 231 each sit over
a second
corner spring 233, 235. The central 2 rows x 2 columns of the springs bear on
the
underside of a land 238 located in the main central portion of the end of
bolster 222
longitudinally intermediate bolster pockets 225 and 227.
For the purposes of this description the swivelling, 4 wheel, 2 axle truck 220
has
first and second sideframes 224 that can be taken as having the same upper
rocker
assembly as truck 120, and has a rigidly mounted lower spring seat 240, like
spring seat
144, but having a shape to suit the 2 rows x 4 columns spring layout rather
than the 3 x 3
layout of truck 120. It may also be noted that sideframe window 242 has
greater width
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between sideframe columns 244, 245 than window 126 between columns 128 to
accommodate the longer spring group footprint, and bolster 222 similarly has a
wider end
to sit over the spring group.
In this example, damper wedges 228, 230 and 229, 232 sit over 50 % of the
spring
group i.e., 4/8 namely springs 234, 236, 233, 235. For the same proportion of
vertical
damping as in truck 20, wedges 128 and 130 may tend to have a larger included
angle,
possibly about 60 degrees, although angles in the range of 45 to 70 degrees
could be
chosen depending on spring combinations and spring stiffnesses. Once again, in
a
warping condition, the somewhat wider damping region (the width of two full
coils plus
lateral travel of 1
(+/-)) of sideframe column wear plates 246, 247 lying between
inboard and outboard gibbs 248, 249, 250, 251 relative to truck 20 (a damper
width of
one coil with travel), sprung on individual springs (inboard and outboard in
truck 220, as
opposed to a single central coil in truck 20), may tend to generate a moment
couple to
give a restoring force working on a moment arm. This restoring force may tend
to urge
the sideframe back to a square orientation relative to the bolster, with
diagonally opposite
pairs of springs working as described above. In this instance, the springs
each work on a
moment arm distance corresponding to half of the distance between the centers
of the 2
rows of coils, rather than half the 3 coil distance shown in Figure 4.
One way to encourage an increase in the hunting threshold is to employ a truck
having a longer wheelbase, or one whose length is proportionately great
relative to its
width. For example, at present two axle truck wheelbases may generally range
from
about 5' ¨ 3" to 6' ¨ 0". However, the standard North American track gauge is
4' ¨ 8 Y2",
giving a wheelbase to track width ratio possibly as small as 1.12. At 6' ¨ 0"
the ratio is
roughly 1.27. It would be preferable to employ a wheelbase having a longer
aspect ratio
relative to the track gauge.
In the case of truck 220, the size of the spring group yields an opening
between
the vertical columns of sideframe of roughly 33 inches. This is relatively
large compared
to existing spring groups, being more than 25 % greater in width. In an
alternate 3 x 5
spring group arrangement, the opening between the sideframe columns is more
than 27 Y2
inches wide. Truck 220 also has a greater wheelbase length, indicated as WB.
WB is
advantageously greater than 73 inches, or, taken as a ratio to the track gauge
width, and is
also advantageously greater than 1.30 times the track gauge width. It is
preferably
greater than 80 inches, or more than 1.4 times the gauge width, and in one
embodiment is
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greater than 1.5 times the track gauge width, being as great, or greater than,
about 86
inches.
It will be understood that the features of the trucks of Figures 2a, 2b, 3a,
3b, 4,
5a, 5b, Sc, 5d and 7a to 7e are provided by way of illustration, and that the
features of the
various trucks can be combined in many different permutations and
combinations. That
is, a 2 x 4 spring group could also be used with a single wedge damper per
side.
Although a single wedge damper per side arrangement is shown in Figures 2a and
3a, a
double damper arrangement, as shown in Figures 4 and 5a is nonetheless
preferred as a
double damper arrangement may tend to provide enhanced squaring of the truck
and
resistance to hunting. A 3 x 3 or 3 x 5, or other arrangement spring set may
be used in
place of either a 3:2:3 or 2 x 4 spring set, with a corresponding adjustment
in spring seat
plate size and layout. Similarly, the trucks can use a wide sideframe window,
and
corresponding extra long wheel base, or a smaller window. Further, each of the
trucks
could employ a rocking bottom spring seat, as in Figure 2b, or a fixed bottom
spring seat,
as in Figure 3a, 4 or 5a.
When a lateral perturbation is passed to the wheels by the rails, the rigid
axles will
tend to cause both sideframes to deflect in the same direction. The reaction
of the
sideframes is to swing, rather like pendula, on the upper rockers. The
pendulum and the
twisted springs will tend to urge the sideframes back to their initial
position. The
tendency to oscillate harmonically due to the track perturbation will tend to
be damped
out by the friction of the dampers on the wear plates.
As before, the upper rocker seats are inserts, typically of a hardened
material,
whose rocking, or engaging surface 80 has a radius of curvature of about five
inches,
with the center of curvature (when assembled) lying above the upper rockers
(i.e., the
surface is upwardly concave).
In each of the trucks shown and described herein, for a fully laden car type,
the
lateral stiffness of the sideframe acting as a pendulum is less than the
lateral stiffness of
the spring group in shear. In one embodiment, the vertical stiffness of the
spring group is
less than 12,000 Lbs./in, with a horizontal shear stiffness of less than 6000
Lbs./in. The
pendulum has a vertical length measured (when undeflected) from the rolling
contact
interface at the upper rocker seat to the bottom spring seat of between 12 and
20 inches,
preferably between 14 and 18 inches. The equivalent length Leq, may be in the
range of 8
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to 20 inches, depending on truck size and rocker geometry, and is preferably
in the range
of 11 to 15 inches, and is most preferably between about 7 and 9 inches for 28
inch
wheels (70 ton "special"), between about 8 1/2 and 10 inches for 33 inch
wheels (70 ton),
9 1/ and 12 inches for 36 inch wheels (100 or 110 ton), and 11 and 13 1/2
inches for 38
inch wheels (125 ton). Although truck 120 or 220 may be a 70 ton special, a 70
ton, 100
ton, 110 ton, or 125 ton truck, it is preferred that truck 120 or 220 be a
truck size having
33 inch diameter, or even more preferably 36 or 38 inch diameter wheels.
In the trucks described herein according to the present invention, Lresultant,
as
defined above, is greater than 10 inches, is advantageously in the range of 15
to 25
inches, and is preferably between 18 and 22 inches, and most preferably close
to about 20
inches. In one particular embodiment it is about 19.6 inches, and in another
particular
embodiment it is about 19.8 inches.
In the trucks described herein, for their fully laden design condition which
may be
determined either according to the AAR limit for 70, 100, 110 or 125 ton
trucks, or,
where a lower intended lading is chosen, then in proportion to the vertical
sprung load
yielding 2 inches of vertical spring deflection in the spring groups, the
equivalent lateral
stiffness of the sideframe, being the ratio of force to lateral deflection
measured at the
and a corresponding lateral shear stiffness kspring shear of 4800 lbs./in. The
sideframe has a
rigidly mounted lower spring seat. It is used in a truck with 36 inch wheels.
In another
embodiment, a 3 x 5 group of 5 1/2 inch diameter springs is used, also having
a vertical
stiffness of about 9600 lbs./in. in a truck with 36 inch wheels. It is
intended that the
vertical spring stiffness per spring group be in the range of less than 30,000
lbs./in., that it
advantageously be in the range of less than 20,000 lbs./in and that it
preferably be in the
range of 4,000 to 12000 lbs./in, and most preferably be about 6000 to 10,000
lbs./in. The
twisting of the springs has a stiffness in the range of 750 to 1200 lbs./in.
and a vertical
shear stiffness in the range of 3500 to 5500 lbs./in. with an overall
sideframe stiffness in
the range of 2000 to 3500 lbs./in.
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In the embodiments of trucks in which there is a fixed bottom spring seat, the
truck may have a portion of stiffness, attributable to unequal compression of
the springs
equivalent to 600 to 1200 Lbs./in. of lateral deflection, when the lateral
deflection is
measured at the bottom of the spring seat on the sideframe. Preferably, this
value is less
than 1000 Lbs./in., and most preferably is less than 900 Lbs./in. The portion
of restoring
force attributable to unequal compression of the springs will tend to be
greater for a light
car as opposed to a fully laden car, i.e., a car laden in such a manner that
the truck is
approaching its nominal load limit, as set out in the 1997 Car and Locomotive
Cyclopedia at page 711.
The double damper arrangements shown above can also be varied to include any
of the four types of damper installation indicated at page 715 in the 1997 Car
and
Locomotive Cyclopedia, with appropriate structural changes for doubled
dampers, with
each damper being sprung on an individual spring. That is, while inclined
surface bolster
pockets and inclined wedges seated on the main springs have been shown and
described,
the friction blocks could be in a horizontal, spring biased installation in a
pocket in the
bolster itself, and seated on independent springs rather than the main
springs.
Alternatively, it is possible to mount friction wedges in the sideframes, in
either an
upward orientation or a downward orientation.
Reduced Radius of Curvature Bearing Adapter
Trucks A20, 10, 120, and 220 discussed thus far have been considered in the
context of trucks having the upper rocker, pedestal seat, and bearing adapter
rocker
geometry of a swing motion truck. However, a conventional, non-swing motion
truck
does not have the upper rocker arrangement of a swing motion truck as
indicated by
upper rocker 40 and bearing adapter 42. Rather, it may tend to have a planar
pedestal
seat bearing surface which makes rolling line contact with a downwardly
concave (i.e.,
crowned) bearing surface of a bearing adapter. The crowned surface may have a
radius
of curvature of some 60 inches, the center of curvature lying below the
surface. As noted
above, in a conventional three piece truck suspension the lateral spring
stiffness tends to
be strongly related to the vertical spring stiffness. A swing motion truck
alters this
relationship by introducing a relatively soft pendulum. The softness of the
pendulum
then becomes the dominant element of the lateral response, and is not directly
related to
the vertical stiffness of the springs.
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An aspect of the present invention is to use a bearing adapter having crown
having a smaller radius of curvature, such that the pendulum stiffness of the
sideframe is
preferably less than the shear stiffness of the spring group. That is, the
pendulum
stiffness is sufficiently low that the shear stiffness in the spring group is
no longer so
dominant in determining the lateral response of the truck.
Consider, trucks 120 and 220. This trucks have fixed bottom spring seats. In
an
alternative embodiment, trucks 120 and 220 may not have items 40 and 42. In an
alternative embodiment, these trucks may have the basics structure of a truck
such as a
Barber S2 HD truck, or other commercially available 3 piece truck for
interchange
service in North America, as opposed to a swing motion truck. In such a truck
there may
be a conventional spring group arrangement, such as any of the arrangements
shown at
pages 739 ¨ 746 of the 1997 Cyclopedia. The applicant also notes reference
pages 811 ¨
822 of the 1997 Cyclopedia which pertain to bearings. In general, the existing
spring
group arrangement may typically be a 3 x 3 arrangement, a 2:3:2 arrangement,
or a 3:2:3
arrangement. Such a truck would have a wheel base of 5' ¨ 3" to 6' ¨ 0", and
might
typically have an existing set of bearing adapters mounted to the bearings
located on the
ends of the two axles. An existing type of bearing adapter is shown at page
819 of the
1997 Cyclopedia. As is shown more clearly in the photograph at page 834 of the
1997
Cyclopedia, the bearing adapter has a bearing surface, or interface that is
split into two
portions separated by a central channel groove, or slot. The bearing interface
has a slight
crown. A very detailed illustration, of a bearing adapter is shown at page 682
of the 1980
Cyclopedia, in which the crown is indicated as having a 60 inch crown radius,
with a
tolerance that appears to be + 0", -20" in the half side view. The crown
radius is concave
downward ¨ i.e., the center of curvature lies below the surface.
The pedestal of the sideframe of the existing truck has a mating bearing face,
in
the nature of a machined flat surface for mating in line contact with the
crowned portions
of the bearing surface interface in rolling contact. A lateral force
transmitted into the
bottom spring seat may then tend to cause rolling motion between the crowned
interface
and flat surface.
The lateral motion of the existing sideframe is constrained by inboard and
outboard gibs that may allow roughly about 1/4", 3/8" or 'A" of lateral travel
either inboard
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or outboard of a central position. (that is, the total lateral travel may be
in the range of
twice those amounts, namely 1/2" to 1"). The bottom spring seat of this truck
does not
have a rocker, but is rigidly located on the lower sideframe member (i.e., the
tension
member).
Referring to Figures 6a to 6f, a truck employing bearing adapter 400 may
either
be constructed originally, or can be retrofit to a converted condition by a
number of steps.
One step is to remove the existing bearing adapter and replacing it with new
bearing
adapter 400 as shown in Figures 6a and 6b. New bearing adapter 400 can be
taken as
being the same as the old bearing adapter except insofar as the profile of the
crowned
interface of new bearing adapter 400 has a significantly reduced radius of
curvature R3.
That is, if made on a circular arc, the radius of curvature of arcuate
portions 402 and 404
of bearing adapter 400 may be in the range of less than 30". The radius of
curvature may
be in the range of 3 to 24 inches, in a narrower range of 3 to 12 inches,
advantageously in
the range of 4 to 8 inches, and preferably about 5". The curved crown portion
of bearing
adapter 400 merges into the surrounding generally planar portions 408 of the
upper
surface of bearing adapter 400 more generally.
A further alternate embodiment of bearing adapter profile is shown in Figure
6c.
In this instance bearing adapter 420 has a central portion 422 having a radius
of curvature
R4, which, like R3, is significantly less than 60". Adjacent to central
portion 422,
bearing adapter 420 has shoulder portions 424 and 426 having greater radii of
curvature
R5 than central portion 422, the edges of shoulder portions 424 and 426
merging with the
surrounding surface 428. The line of intersection of the shoulder regions lies
at an angle
01 (omega) from the vertical. In the region between + and ¨ Ell to either side
of the
central position, namely in the 02 region, the pendulum behaviour of the
sideframe may
tend to be governed by the first radius of curvature. Outside of that central
range, it will
tend to be governed by the radius of curvature of shoulder portions 424 and
426. This
may tend yield a two regime dynamic response to lateral input perturbations,
namely a
relatively soft, low amplitude portion central portion, and a stiffer, larger
amplitude
portion corresponding to the shoulders. In one embodiment the first region may
tend to
have a radius of curvature in the range of 3 to 10 inches, or more preferably
about 4 ¨ 6
inches, and most preferably about 5 inches, while the second region may have a
radius of
curvature in the range of 10 to 30 inches, or more preferably 12 to 20 inches,
and most
preferably about 15 inches. The size of the angle 01 may be such as to give a
lateral
deflection under the first regime of 3/4" to 1 ¨ 1/4" an inch, and preferably
about 1" to
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either side of a central position, when deflection is measured at the bottom
spring seat.
Alternatively, as measured by angle, the size of angle omega may be about 2¨
1/2 to about
4 degrees, and preferably about 3- 1/4 degrees.
In a further alternate embodiment of the invention, in Figure 6e, a bearing
adapter
440 may have a crown profile 442 for which one or more portions have a
continuously
changing radius of curvature R(e) (meaning R is a function of theta, the given
angle
from the vertical), from a minimum at the central rest position (i.e., at zero
degrees lateral
deflection) to a maximum at the point at which the side frame abuts one or
other of the
inboard or outboard gibs. For example, profile 442 may be in the form of a
downwardly
opening curve, for which the instantaneous radius of curvature is smallest,
perhaps in the
range of 3 ¨ 6 inches, at the central region, and larger to either side
thereof, ranging up to
perhaps 15 ¨ 20 inches at the edge of the zone of travel when the sideframe
abuts one or
other of the gibs.
The sideframe may tend to bottom out on the bolster gibs before the rolling
line of
contact runs off the arcuate surfaces. When this occurs, the truck bolster is
constrained
from further lateral motion relative to the side frames, and may then tend to
deflect in a
rocking motion on the main springs, depending on the mass carried, and on the
height of
the center of gravity of that mass, and the magnitude of the lateral input
perturbation at
track level., yielding a third possible, rocking, regime outside the first and
second
regimes corresponding to the radii of the first and second regions of the
arcuate crown
profile.
It may be that a particular material is preferred for fabrication of these
arcuate
surfaces. To that end, the arcuate bearing surface of the bearing adapter may
be
strengthened, or hardened, and a suitably strengthened or hardened seat may be
installed
in the sideframe pedestal. Alternatively, as shown in Figure 6e, any of the
various
embodiments of curved bearing surface of Figures 6a, 6c, or 6d may employ an
insert
462, as shown in bearing adapter 460, the insert being made of a similar
material to that
used for rockers and rocker seats in a swing motion truck.
Figure 6f, based on the illustration at page 819 of the 1997 Cyclopedia, shows
the
general installation position of the bearing adapter, be it 400, 420, 440, or
460, in the side
frame, indicated generically as 470, the pedestal mounting 472 having a flat
bearing
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surface 474. The bearing is indicated as 476. The axle is on which the bearing
is
mounted is indicated as 478.
Retro-Fit Gibs
To accommodate greater lateral movement, the truck, whether new or retro-fit,
may be provided with a gib arrangement allowing greater lateral travel as in
truck 120, or
220. That is, for a retro-fit truck, the existing gibs may be removed, and
replacement gibs
provided and installed on a wider spacing, corresponding to that shown for
trucks 120
and 220 above. While the desired range of gib spacing may be at least 1" inch
to either
side of an at rest centered position of the sideframe between the gibs, it is
preferred if the
gib spacing dimension be in the range of 1 ¨ 3/4" to 1 ¨ 3/4", preferably in
the range of 1 ¨
3/8" to 1 ¨ 5/8", and most preferably about 1 - '/2" to either side of the at
rest central
position. While it is preferable that the gib spacing be symmetrical relative
to the central,
at rest, position of the truck bolster relative to the sideframes, it is not
necessarily so.
That is, the outboard gib spacing may be slightly greater than the inboard gib
spacing,
perhaps by as much as 3/8".
Retro-Fit Damper Arrangement
The retro-fit truck may be provided with a 4 corner damper arrangement, as in
truck 120, 220. To that end, an existing bolster may be removed and replaced
with a
bolster originally manufactured with a four-corner bolster arrangement as in
truck 120, or
220, or, alternatively, the outboard end portions of the existing bolster may
be rebuilt
with inserts, each insert having a pair of spaced apart damper pockets, and
damper
wedges to seat above the corner springs of the spring group arrangement. As
will be
understood, where the same proportion of vertical damping force is desired as
before, the
angle of the damper wedges may be adjusted correspondingly to larger angles,
there
being a variety of possible damper arrangements, whether split dampers, or
dampers
having both primary and secondary angles, or combinations thereof.
Alternatively, the
springs in the spring group can be subject to a different selection of sizes
and a different
damper wedge angle to give the desired amount of damping.
Where a four-cornered damper arrangement is to be installed by retro-fit,
existing
side frame column wear plates may be removed, and replaced by corresponding
new,
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wider, side frame column wear plates of appropriate width to accommodate both
the
wider damper arrangement, and the lateral travel of the bolster relative to
the side frames.
A truck modified in this manner (or built as original equipment in this
manner)
may tend to be able to retain substantially the same, relatively stiff,
vertical spring
stiffness as it had before being modified, yet may have a significantly
softened lateral
response for which the dominant element of lateral stiffness is the softness
of the
pendulum. For a set of springs in a spring group having an overall vertical
spring rate of
about 25,000 lbs/inch (+/- 5,000 lbs/inch), and a radius of curvature on the
pendulum
surface of 5 inches, the effective lateral stiffness for a laden 286,000 lbs.,
box car, such as
may be used for carrying rolls of paper may be have a pendulum stiffness in
the range of
about 4,000 ¨ 6000 lbs/in of lateral deflection measured at the end of the
bolster, and
preferably in the range of about 5000 lbs/in or somewhat less than that.
Depending on
the actual value, this value may be roughly half of the value that might
otherwise have
been the case before modification of the truck.
Optionally, where the truck originally has a frame brace, that frame brace may
be
removed. If the truck originally had a transom, that transom may be removed.
The trucks of the foregoing embodiments may be used with relatively soft
vertical
spring rate spring groups, where the vertical spring rate of the group is less
than about
18,000 to 20,000 lbs. per inch, and possibly less than 12,000 lbs per inch,
such as might
tend to be suitable to give a softer ride for low density, high value goods
such as
automobiles, white goods, electronic equipment or other consumer goods more
generally.
Such a truck may be employed in the types of freight car shown in Figure 8,
namely an
autorack rail road car 280 (whether in single units or articulated); an
intermodal well car
282 (whether in single writs, as 282, or articulated as 284) , such as, for
example, a
double stack container carrying well car; a spine car for carrying highway
trailers 286
(whether as a single unit or articulated); an auto-parts box car or a box car
for consumer
merchandise 288; an intermodal flat car 290; or, more generally for any kind
of rail road
car with a relatively low density, fragile type of lading.
Alternatively, the trucks of the foregoing embodiments may be used with
stiffer
vertical spring rates, in the ranges above 20,000 lbs / in per spring group,
and more
strongly, in the range of greater than 25,000 lbs / in per spring group, such
as might be
used in freight cars 292 such as shown in Figure 9 for carrying general
merchandise or
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commodiites of greater density, including rail road freight car 294 for
carrying rolls of
paper, for which a relatively soft lateral response might still be desired.
In one embodiment, a truck, in particular a 110 Ton variation of truck 120 or
220,
may have a 3 x 3 or 3:2:3, or 2:3:2 spring group of relatively high vertical
stiffness (e.g.,
more than 20,000 lbs/ inch per spring group), a four cornered damper
arrangement, a
bearing adapter and side frame pedestal arrangement having a rolling contact
on a
relatively small radius of curvature (4 ¨ 6 inches), with gibs accordingly
spaced to permit
relatively generous lateral travel (e.g., the in the range of 1 to 1 ¨ 5/8
inches to either side
of a central rest position) of the truck bolster with respect to the
sideframes. Such a
truck may be intended for service in a paper carrying box car or an auto-parts
box car.
Parameter values for 5 different embodiments 110 Ton trucks having 3 x 3
spring group
arrangements with fixed side frame bottom seats and four cornered damper
layouts are
attached as appendix A hereto. The parameter values in these embodiments are
approximate, and may include values +/- 10% lesser or greater than the values
indicated.
The embodiments of trucks shown and described herein may vary in their
suitability
for different types of service. Truck performance can vary significantly based
on the
loading expected, the wheelbase, spring stiffnesses, spring layout, pendulum
geometry,
damper layout and damper geometry.
Various embodiments of the invention have now been described in detail. Since
changes in and or additions to the above-described best mode 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 by the appended claims.
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