Note: Descriptions are shown in the official language in which they were submitted.
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RAIL ROAD CAR TRUCK
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.
The sideframes carry forces to the sideframe pedestals. The pedestals seat on
bearing
adapters, whence forces are carried in turn into the bearings, the axle, the
wheels, and finally
into the tracks. The three piece truck relies upon a suspension in the form of
the spring
groups trapped in a "basket" between each of the ends of the truck bolster and
its associated
sideframe. For wheel load equalisation, a three piece truck uses one set of
springs, and the
side frames pivot about the ends of the truck bolster in a manner like a
walking beam. The
1980 Car & Locomotive Cyclopedia states at page 669 that the three piece truck
offers
"interchangeability, structural reliability and low first cost but does so at
the price of
mediocre ride quality and high cost in terms of car and track maintenance."
Ride quality can be judged on a number of different criteria. There is
longitudinal
ride quality, where, often, the limiting condition is the maximum expected
longitudinal
acceleration experienced during humping or flat switching, or slack run-in and
run-out.
There is vertical ride quality, for which vertical force transmission through
the suspension is
the key determinant. There is lateral ride quality, which relates to the
lateral response of the
suspension. There are also other phenomena to be considered, such as truck
hunting, the
ability of the truck to self steer, and, whatever the input perturbation may
be, the ability of
the truck to damp out undesirable motion. These phenomena tend to be inter-
related, and the
optimization of a suspension to deal with one phenomenon may yield a system
that may not
necessarily provide optimal performance in dealing with other phenomena.
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..
In terms of optimizing truck performance, it may generally be desirable to
obtain a
measure of self steering in the truck, desirable to avoid truck hunting, and
desirable to have a
relatively soft lateral and vertical response. It would be advantageous to be
able to obtain the
desirable relatively soft dynamic response to lateral and vertical
perturbations, to obtain a
measure of self steering, and yet to maintain resistance to lozenging (or
parallelogramming).
Lozenging, or parallelogramming, is non-square deformation of the truck
bolster relative to
the side frames of the truck as seen from above. It may also be desirable to
obtain a measure
of self-steering. Self steering may tend to be desirable since it may reduce
drag and may tend
to reduce wear to both the wheels and the track, and may give a smoother
overall ride.
In general, the lateral stiffness of the suspension may tend to reflect the
combined
lateral displacement of (a) the sideframe between (i) the bearing adapter and
(ii) the bottom
spring seat (that is, the sideframes may swing or rock laterally), 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 may
sometimes be estimated as being approximately half of the vertical spring
stiffness. Thus the
choice of vertical spring stiffness may strongly affect the lateral stiffness
of the suspension.
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.
It may be desirable to have springs of a given vertical stiffness to give
certain vertical
ride characteristics, and a different characteristic for lateral
perturbations. For example, a
softer lateral response through the main spring groups 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
(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.
For the purposes of rapid estimation of truck lateral stiffness, the following
formula
can be used:
ktruck = 2 x [ (ksideframe)-1 + (kspring shear)-1]-1
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where
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 = kx, a
lateral constant (for small angles) can be defined as kpendulum = 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 1/4
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". 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, namely the transom, frame brace, or
lateral
reinforcement rods, it may at the same time tend to be laterally relatively
soft.
One way to obtain a measure of passive self steering is to mount elastomeric
pads
between the pedestal seat and the bearing adapter. That is to say, when a
conventional truck
enters a curve, the leading outer wheel may tend to want to pull ahead
relative to the leading
inner wheel, and the inner wheel may then tend to want to slip, or skid,
somewhat. The
converse may tend to occur on the trailing axle. This tendency to slip or skid
may be reduced
somewhat if the axles are able to steer a bit, and thereby to conform to some
extent to the
curve. Elastomeric pads, sometimes manufactured by Lord Corp., have sometimes
been used
for this purpose, and may provide a resilient means for permitting some self
steering to take
place.
Considering the interface between the pedestal seat and the wheelsets at the
bearing
adapters, there are, potentially, six degrees of freedom, namely vertical,
longitudinal and
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transverse translation, and rotation about each of the vertical, longitudinal,
and lateral axes.
For the purposes of analysis, in the vertical direction the connection can be
approximated as
being nearly infinitely stiff. In the longitudinal direction, the stiffness
with an elastomeric
pad is a function of the shear modulus of the elastomer, the area of the
elastomer in plan
view, and the thickness of the elastomer. If the elastomer is of constant
thickness, and is
more or less flat, the lateral stiffness may tend to be roughly the same in
both longitudinal
and lateral shear. The pad may tend to have torsional compliance about the
vertical axis to
permit the typically relatively small angular deflection of steering.
Longitudinal cylindrical rockers have been employed to increase warp stiffness
by
compelling the fore and aft bearing adapter interfaces to swing in unison on a
common hinge
line. Where substantially cylindrical rockers of relatively close radii are
used, (that is, where
the radius of curvature of the rocker is relatively close to the radius of
curvature of the seat)
as for example in US Patent 5,544,591 of Armand Taillon, issued August 13,
1996, the
torsional stiffness about the vertical, or z, axis of the interface between
the bearing adapter
crown and the pedestal seat roof may be very high, such that it may tend to
provide resistance
to unsquaring relative movement between the wheelsets and side frames.
Summary of the Invention
In an aspect of the present invention, there is a rail road car truck that has
a self
steering capability and friction dampers in which the co-efficients of static
and dynamic
friction are substantially similar. It may include the added feature of
lateral rocking at the
sideframe pedestal to wheelset axle end interface. It may include self
steering proportional
to the weight carried by the truck. It may further have a longitudinal rocker
at the sideframe
to axle end interface. Further it may provide a swing motion truck with self
steering. It may
also provide a swing motion truck that has the combination of a swing motion
lateral rocker
and an elastomeric bearing adapter pad. In another feature, the truck may have
dampers
lying along the longitudinal centerline of the spring groups of the truck
suspensions. In
another feature, it may include dampers mounted in a four cornered
arrangement. In another
feature it may include dampers having modified friction surfaces on both the
friction bearing
face and on the obliquely angled face of the damper that seats in the bolster
pocket.
In another aspect of the invention, a three piece rail road car truck has a
truck bolster
mounted transversely between a pair of sideframes. The truck bolster has ends,
each of the ends
being resiliently mounted to a respective one of the sideframes. The truck has
a set of dampers
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mounted in a four cornered damper arrangement between each the bolster end and
its respective
sideframe. Each damper has a bearing surface mounted to work against a mating
surface at a
friction interface in a sliding relationship when the bolster moves relative
to the sideframes.
Each damper has a seat against which to mount a biasing device for urging the
bearing face
against the mating surface. The bearing surface of the damper has a dynamic co-
efficient of
friction and a static co-efficient of friction when working against the mating
surface. The static
and dynamic co-efficients of friction are of substantially similar magnitude.
In a further feature of that aspect of the invention, the co-efficients of
friction have
respective magnitudes within 10 % of each other. In another feature, the co-
efficients of friction
are substantially equal. In another feature the co-efficients of friction lie
in the range of 0.1 to
0.4. In still another feature, the co-efficients of friction lie in the range
0.2 to 0.35. In a further
feature, the co-efficients of friction are about 0.30 (+1- 10 %). In still
another feature, the
dampers each include a friction element mounted thereto, and the bearing
surface is a surface of
the friction element. In yet still another feature, the friction element is a
composite surface
element that includes a polymeric material.
In another feature of that aspect of the invention, the truck. is a self-
steering truck. In
another feature, the truck includes a bearing adapter to sideframe pedestal
interface that includes
a self-steering apparatus. In another feature, the self-steering apparatus
includes a rocker. In a
further feature, the truck includes a bearing adapter to sideframe pedestal
interface that includes
a self-steering apparatus having a force-deflection characteristic varying as
a function of vertical
load. In still another feature, the truck has a bearing adapter to sideframe
pedestal interface that
includes a bi-directional rocker operable to permit lateral rocking of the
sideframes and to
permit self-steering of the truck.
In another feature of that aspect of the invention, each damper has an oblique
face for
seating in a damper pocket of a truck bolster of a rail road car truck, the
bearing face is a
substantially vertical face for bearing against a mating sideframe column wear
surface, and, in
use, the seat is oriented to face substantially downwardly. In another
feature, the oblique face
has a surface treatment for encouraging sliding of the oblique face relative
to the damper pocket.
In still another feature, the oblique face has a static coefficient of
friction and a dynamic co-
efficient of friction, and the co-efficients of static and dynamic friction of
the oblique face are
substantially equal. In a further feature, the oblique face and the bearing
face both have sliding
surface elements, and both of the sliding surface elements are made from
materials having a
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polymeric component. In yet a further feature, the oblique face has a primary
angle relative to
the bearing surface, and a cross-wise secondary angle.
In another aspect of the invention, there is a three piece railroad car truck
having a
bolster transversely mounted between a pair of sideframes, and wheelsets
mounted to the
sideframes at wheelset to sideframe interface assemblies. The wheelset to
sideframe interface
assemblies are operable to permit self steering, and include apparatus
operable to urge the
wheelsets in a lengthwise direction relative to the sideframes to a minimum
potential energy
position relative to the sideframes. The self-steering apparatus has a force
deflection
characteristic that is a function of vertical load.
In a further aspect of the invention, there is a bearing adapter for a
railroad car truck.
The bearing adapter has a body for seating upon a bearing of a rail road truck
wheelset, and a
rocker member for mounting to the body. The rocker member has a rocking
surface, the
rocking surface facing away from the body when the rocker member is mounted to
the body,
and the rocker being made of a different material from the body.
In a further feature of that aspect, the rocker member is made from a tool
steel. In
another feature of that aspect of the invention, the rocker member is made
from a metal of a
grade used for the fabrication of ball bearings. In another feature, the body
is made of cast iron.
In another feature, the rocker member is a bi-directional rocker member. In
still another feature,
the rocking surface of the rocking member defines a portion of a spherical
surface.
In another aspect of the invention, there is a three piece railroad car truck
having rockers
for self steering. In still another aspect, there is a railroad car truck
having a sideframe, an axle
bearing, and a rocker mounted between the sideframe and the axle bearing. The
rocker has a
transverse axis to permit rocking of and the bearing lengthwise relative to
the sideframe.
In another aspect of the invention there is a three piece railroad car truck
having a bolster
mounted transversely to a pair of sideframes. The side frames have pedestal
fittings and
wheelsets mounted in the pedestal fittings. The pedestal fittings include
rockers. Each rocker
has a transverse axis to permit rocking in a lengthwise direction relative to
the sideframes.
In another aspect of the invention there is a three piece railroad car truck
having a truck
bolster mounted transversely to a pair of side frames, each sideframes has
fore and aft pedestal
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seat interface fittings, and a pair of wheelsets mounted to the pedestal seat
interface fittings. The
pedestal seat interface fittings include rockers operable to permit the truck
to self steer.
In another aspect of the invention there is a railroad car truck having a
sideframe, an axle
bearing, and a bi-directional rocker mounted between the sideframe and the
axle bearing. In
still another aspect of the invention, there is a railroad car truck having a
truck bolster mounted
transversely between a pair of sideframes, and wheelsets mounted to the
sideframes to permit
rolling operation of the truck along a set of rail road tracks. The truck
includes rocker elements
mounted between the sideframes and the wheelsets. The rocker elements are
operable to permit
lateral swinging of the sideframes and to permit self-steering of the truck.
In another aspect of the invention there is a railroad car truck having a pair
of
sideframes, a pair of wheelsets having ends for mounting to the sideframes,
and sideframe to
wheelset interface fittings. The sideframe to wheelset interface fittings
include rocking
members having a first degree of freedom permitting lateral swinging of the
sideframes relative
to the wheelsets, and a second degree of freedom permitting longitudinal
rocking of the
wheelset ends relative to the sideframes.
In another aspect of the invention there is a railroad car truck having
rockers formed on
a compound curvature, the rockers being operable to permit both a lateral
swinging motion in
the truck and self steering of the truck. In still another aspect of the
invention, there is a railroad
car truck having a pair of sideframes, a pair of wheelsets having ends for
mounting to the
sideframes, and sideframe to wheelset interface fittings. The sideframe to
wheelset interface
fittings include rocking members having a first degree of freedom permitting
lateral swinging of
the sideframes relative to the wheelsets, a second degree of freedom
permitting longitudinal
rocking of the wheelset ends relative to the sideframes. The wheelset to
sideframe interface
fittings being torsionally compliant about a predominantly vertical axis.
In aspect of the invention there is a swing motion rail road car truck
modified to include
rocking elements mounted to permit self-steering. In yet another aspect there
is a swing motion
rail road car truck having a transverse bolster sprung between a pair of side
frames, and a pair of
wheelsets mounted to the sideframes at wheelset to sideframe interface
fittings. The wheelset to
sideframe interface fittings include swing motion rockers and elastomeric
members mounted in
series with the swing motion rockers to permit the truck to self-steer.
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In another aspect of the invention, there is a rail road car truck having a
truck bolster
mounted transversely between a pair of sideframes, and wheelsets mounted to
the sideframes at
wheelset to sideframe interface fittings. The wheelset to sideframe interface
fittings include
rockers for permitting lateral swinging motion of the sideframes. The rockers
have a male
element and a mating female element. The male and female rocker elements are
engaged for
co-operative rocking operation. The female element has a radius of curvature
in the lateral
swinging direction of less than 25 inches. The wheelset to sideframe interface
fittings are also
operable to permit self steering.
In still another aspect of the invention there is a rail road car truck having
a truck bolster
mounted transversely between a pair of sideframes, and wheelsets mounted to
the sideframes at
wheelset to sideframe interface fittings. The wheelset to sideframe interface
fittings include
rockers for permitting lateral swinging motion of the sideframes. The rockers
have a male
element and a mating female element. The male and female rocker elements are
engaged for
co-operative rocking operation. The sideframe have an equivalent pendulum
length, Leg, when
mounted on the rocker, of greater than 6 inches. The wheelset to sideframe
interface fittings
include an elastomeric member mounted in series with the rockers to permit
self steering.
In yet another aspect of the invention there is a rail road car truck having a
truck bolster
mounted transversely between a pair of sideframes, and wheelsets mounted to
the sideframes at
wheelset to sideframe interface fittings. The wheelset to sideframe interface
fittings include
rockers for permitting self steering of the truck. The rockers have a male
element and a mating
female element. The male and female rocker elements are engaged for co-
operative rocking
operation, and the wheelset to sideframe interface fittings include an
elastomeric member
mounted in series with the rockers.
In still another aspect of the invention there is a rail road car truck having
a transverse
bolster sprung between twos sideframes, and wheelsets mounted to the
sideframes at wheelset to
sideframe interface fittings, the truck having a spring groups and dampers
seated in the bolster
and biased by the spring groups to ride against the sideframes. The spring
groups include a first
damper biasing spring upon which a first damper of the dampers seats. The
first damper biasing
spring has a coil diameter. The first damper has a width of more than 150 % of
the coil
diameter.
In another aspect of the invention there is a rail road car truck having a
bolster having
ends sprung from a pair of sideframes, and wheelsets mounted to the sideframes
at wheelset to
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_
sideframe interface fittings. The wheelset to sideframe interface fittings
include bi-directional
rocker fittings for permitting lateral swinging of the sideframes and for
permitting self steering
of the wheelsets. The truck has a four cornered arrangement of dampers mounted
at each end of
the bolster. In a further feature of that aspect of the invention the
interface fittings are
torsionally compliant about a predominantly vertical axis.
In another aspect there is a railroad car truck having a bolster transversly
mounted
between a pair of sideframes, and wheelsets mounted to the sideframes. The
railroad car truck
have a hi-directional longitudinal and lateral rocking interface between each
sideframe and
wheelset, and four cornered damper groups mounted between each sideframe and
the truck
bolster. In an additional feature of that aspect of the invention the rocking
interface is
torsionally compliant about a predominantly vertical axis. In another
additional feature, the
rocking interface is mounted in series with a torsionally compliant member.
In yet another aspect of the invention there is a self-steering rail road car
truck having a
transversely mounted bolster sprung between two sideframes, and wheelsets
mounted to the
sideframes. The sideframes are mounted to swing laterally relative to the
wheelsets. The truck
has friction dampers mounted between the bolster and the sideframes. The
friction dampers
have co-efficients of static friction and dynamic friction. The co-efficients
of static and dynamic
friction being substantially the same.
In still another aspect there is a self-steering rail road car truck having a
transversely
mounted bolster sprung between two sideframes, and wheelsets mounted to the
sideframes. The
sideframes are mounted to swing laterally relative to the wheelsets. The truck
has friction
dampers mounted between the bolster and the sideframes. The friction dampers
have co-
efficients of static friction and dynamic friction. The co-efficients of
static and dynamic friction
differ by less than 10 %. Expressed differently, the friction dampers having a
co-efficient of
static friction, us, and a co-efficient of dynamic friction, uk, and a ratio
of us/uk lies in the range
of 1.0 to 1.1. In another aspect of the invention, the truck has friction
dampers mounted
between the bolster and the sideframes in a sliding friction relationship that
is substantially free
of stick-slip behaviour. In another feature of that aspect of the invention
the friction dampers
include friction damper wedges having a first face for engaging one of the
sideframes, and a
second, sloped, face for engaging a bolster pocket. The sloped face is mounted
in the bolster
pocket in a sliding friction relationship that is substantially free of stick-
slip behaviour.
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In another aspect of the invention there is a self-steering rail road car
truck having a
bolster mounted between a pair of sideframes, and wheelsets mounted to the
sideframes for
rolling motion along railroad tracks. The wheelsets are mounted to the
sideframes at wheelset to
sideframe interface fittings. Those fittings are operable to permit lateral
rocking of the
sideframes. The truck has a set of friction dampers mounted between the
bolster and each of the
sideframes. The friction dampers have a first face in sliding friction
relationship with the
sideframes and a second face seated in a bolster pocket of the bolster. The
first face, when
operated in engagement with the sideframe, has a co-efficient of static
friction and a co-efficient
of dynamic friction, the co-efficients of static and dynamic friction of the
first face differing by
less than 10 %. The second face, when mounted within the bolster pocket, has a
co-efficient of
static friction, and a co-efficient of dynamic friction, and the co-efficients
of static and dynamic
friction of the second face differing by less than 10 %.
In yet another aspect of the invention there is a self-steering rail road car
truck having a
bolster mounted between a pair of sideframes, and wheelsets mounted to the
sideframes for
rolling motion along railroad tracks. The wheelsets are mounted to the
sideframes at wheelset to
sideframe interface fittings. The interface fittings are operable to permit
lateral rocking of the
sideframes. The truck has a set of friction dampers mounted between the
bolster and each of the
sideframes. The friction dampers have a first face in slidable friction
relationship with the
sideframes and a second face seated in a bolster pocket of the bolster. The
first face and the side
frame are co-operable and are in a substantially stick-slip free condition.
The second face and
the bolster pocket are also in a substantially stick-slip free condition.
In another aspect of the invention there is a rocker for a bearing adapter of
a rail road car
truck. The rocker has a rocking surface for rocking engagement with a mating
surface of a
pedestal seat of a sideframe of a railroad car truck. The rocking surface has
a compound
curvature to permit both lengthwise and sideways rocking. In a complementary
aspect of the
invention, there is a rocker for a pedestal seat of a sideframe of a rail road
car truck. The rocker
has a rocking surface for rocking engagement with a mating surface of a
bearing adapter of a
railroad car truck. The rocking surface has a compound curvature to permit
both lengthwise and
sideways rocking.
In an aspect of the invention there is a sideframe pedestal to axle bearing
interface
assembly for a three piece rail road car truck, the interface assembly having
fittings operable
to rock both laterally and longitudinally.
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In an additional feature of that aspect of the invention the assembly includes
mating
surfaces of compound curvature, the compound curvature including curvature in
both lateral
and horizontal directions. In another feature, the assembly includes at least
one rocker
element and a mating element, the rocker and mating elements being in point
contact with a
mating element, the element in point contact being movable in rolling point
contact with the
mating element. In still another feature, the element in point contact is
movable in rolling
point contact with the mating element both laterally and longitudinally. In
yet another
feature, the fittings include rockingly matable saddle surfaces.
In another feature, the fittings include a male surface having a first
compound
curvature and a mating female surface having a second compound curvature in
rocking
engagement with each other, and one of the surfaces includes at least a
spherical portion. In
a further feature, the fittings include a non-rocking central portion in at
least one direction.
In still another feature, relative to a vertical axis of rotation, rocking
motion of the fittings
longitudinally is torsionally de-coupled from rocking of the fittings
laterally. In a yet further
feature the fittings include a force transfer interface that is torsionally
compliant relative to
torsional moments about a vertical axis. In still another feature, the
assembly includes an
elastomeric member.
In another aspect of the invention, there is a swing motion three piece rail
road car
truck having a laterally extending truck bolster, a pair of longitudinally
extending sideframes
to which the truck bolster is resiliently mounted, and wheelsets to which the
side frames are
mounted. Damper groups are mounted between the bolster and each of the
sideframes. The
damper groups each have a four-cornered damper layout, and wheelset to
sideframe pedestal
interface assemblies operable to permit lateral swinging motion of the
sideframes and
longitudinal self-steering of the wheelsets.
In a further aspect there is a rail road car truck having a truck bolster
mounted
between sideframes, and wheelsets to which the sideframes are mounted, and
wheelset to
sideframe interface assemblies by which to mount the sideframes to the
wheelsets. The
sideframe to wheelset interface assemblies include rocking apparatus to permit
the
sideframes to swing laterally. The rocking apparatus includes first and second
surfaces in
rocking engagement. At least a portion of the first surface has a first radius
of curvature of
less than 30 inches. The sideframe to wheelset interface includes self
steering apparatus.
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In a feature of that aspect of the invention, the self steering apparatus has
a
substantially linear force deflection characteristic. In another feature, the
self steering
apparatus has a force-deflection characteristic that varies with vertical
loading of the
sideframe to wheelset interface assembly. In a further feature, the force-
deflection
characteristic varies linearly with vertical loading of the sideframe to
wheelset interface
assembly. In another feature, the self steering apparatus includes a rocking
element. In still
another feature, the rocking element includes a rocking member subject to
angular
displacement about an axis transverse to one of the sideframes.
In another feature, the self steering apparatus includes male and female
rocking
elements, and at least a portion of the male rocking element has a radius of
curvature of less
than 40 inches. In still another feature, the self steering apparatus includes
male and female
rocking elements, and at least a portion of the female rocking element has a
radius of
curvature of less than 60 inches. In still another feature the self steering
apparatus is self
centering. In a further feature, the self steering apparatus is biased toward
a central position.
In yet another feature, the self steering apparatus includes a resilient
member. In a
further feature of that further feature, the resilient member includes an
elastomeric element.
In another further feature, the resilient member is an elastomeric adapter pad
assembly. In
another feature, the resilient member is an elastomeric adapter assembly
having a lateral
force-displacement characteristic and a longitudinal force-displacement
characteristic, and
the longitudinal force-displacement characteristic is different from the
lateral force-
displacement characteristic. In another feature, the elastomeric adapter
assembly is stiffer in
lateral shear then in longitudinal shear. In again another feature, a rocker
element is mounted
above the elastomeric adapter pad assembly. In another feature, a rocker
element is mounted
directly upon the elastomeric adapter pad assembly. In a still further
feature, the elastomeric
adapter pad assembly includes and integral rocker member. In another feature,
the three
piece truck is a swing motion truck and the self steering apparatus includes
an elastomeric
bearing adapter pad.
In still another feature, the wheelsets have axles, and the axles have axes of
rotation,
and ends mounted beneath the sideframes, and, at one end of one of the axles,
the self
steering apparatus has a force deflection characteristic of at least one of
the characteristics
chosen from the set of force-deflection characteristic consisting of
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(a) a linear characteristic between 3000 lbs per inch and 10,000 pounds per
inch of
longitudinal deflection, measured at the axis of rotation at the end of the
axle when the self
steering apparatus bears one eighth of a vertical load of between 45,000 and
70,000 lbs.;
(b) a linear characteristic between 16,000 lbs per inch and 60,000 pounds per
inch of
longitudinal deflection, measured at the axis of rotation at the end of the
axle when the self
steering apparatus bears one eighth of a vertical load of between 263,000 and
315,000 lbs.;
and
(c) a linear characteristic between 0.3 and 2.0 lbs per inch of longitudinal
deflection,
measured at the axis of rotation at the end of the axle per pound of vertical
load passed into
the one end of the one axle.
In another aspect of the invention there is a three piece rail road freight
car truck
having self steering apparatus, wherein the passive steering apparatus
includes at least one
longitudinal rocker.
In yet another aspect of the invention, there is a three piece rail road
freight car truck
having passive self steering apparatus, the self steering apparatus having a
linear force-
deflection characteristic, and the force-deflection characteristic varying as
a function of
vertical loading of the truck.
In an additional feature of that aspect of the invention, the force-
displacement
characteristic varies linearly with vertical loading of the truck. In another
feature, the self
steering apparatus includes a rocker mechanism. In another feature, the rocker
mechanism is
displaceable from a minimum energy state under drag force applied to a wheel
of one of the
wheelsets. In still another feature, the force-deflection characteristic lies
in the range of
between about 0.4 lbs and 2.0 lbs per inch of deflection, measured at a center
of and end of
an axle of a wheelset of the truck per pound of vertical load passed into the
end of the axle of
the wheelset. In a further feature, the force deflection characteristic lies
in the range of 0.5 to
1.8 lbs per inch per pound of vertical load passed into the end of the axle of
the wheelset.
In yet another aspect of the invention there is a three piece rail road
freight car truck
having a transversely extending truck bolster, a pair of side frames mounted
at opposite ends
of the truck bolster, and resiliently connected thereto, and wheelsets. The
sideframes are
mounted to the wheelsets at sideframe to wheelset interface assemblies. At
least one of the
sideframe to wheelset interface assemblies is mounted between a first end of
an axle of one
of the wheelsets, and a first pedestal of a first of the sideframes. The
wheelset to sideframe
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interface assembly includes a first line contact rocker apparatus operable to
permit lateral
swinging of the first sideframe and a second line contact rocker apparatus
operable to permit
longitudinal displacement of the first end of the axle relative to the first
sideframe.
In a feature of that aspect of the invention, the first and second rocker
apparatus are
mounted in series with a torsionally compliant member, the torsionally
complaint member
being compliant to torsional moments applied about a vertical axis. In another
feature, a
torsionally compliant member is mounted between the first and second rocker
apparatus, the
torsionally compliant member being torsionally compliant about a vertical
axis.
In a further aspect of the invention, there is a bearing adapter for a three
piece rail
road freight car truck, the bearing adapter having a rocking contact surface
for rocking
engagement with a mating surface of a sideframe pedestal fitting, the rocking
contact surface
of the bearing adapter having a compound curvature.
In another feature of that aspect of the invention, the compound curvature is
formed
on a first male radius of curvature and a second male radius of curvature
oriented cross-wise
thereto. In another feature, the compound curvature is saddle shaped. In a
further feature,
the compound curvature is ellipsoidal. In a further feature, the curvature is
spherical.
In a still further aspect there is a railroad car truck having a laterally
extending truck
bolster. The truck bolster has first and second ends. First and second
longitudinally
extending sideframes are resiliently mounted at the first and second ends of
the bolster
respectively. The side frames are mounted on wheelsets at sideframe to
wheelset mounting
interface assemblies. A four cornered damper group is mounted between each end
of the
truck bolster and the respective side frame to which that end is mounted. The
sideframe to
wheelset mounting interface assemblies are torsionally compliant about a
vertical axis.
In a feature of that aspect of the invention, the truck is free of unsprung
lateral cross-
members between the sideframes. In another feature, the sideframes are mounted
to swing
laterally. In still another feature, the sideframe to wheelset mounting
interface assemblies
include self steering apparatus.
In another aspect of the invention, there is a railroad freight car truck
having wheelsets
mounted in a pair of sideframes, the sideframes having sideframe pedestals for
receiving the
wheelsets. The sideframe pedestals have sideframe pedestal jaws. The sideframe
pedestal jaws
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include sideframe pedestal jaw thrust blocks. The wheelsets have bearing
adapters mounted
thereto for installation between the jaws. The sideframe pedestals have
respective pedestal seat
members rockingly co-operable with the bearing adapter. The truck has members
mounted
intermediate the jaws and the bearing adapters for urging the bearing adapter
to a centered
position relative to the pedestal seat. In another aspect, there is a member
for placement
between the thrust lug of a railroad car sideframe pedestal jaw and the end
wall and corner
abutments of a bearing adapter, the member being operable to urge the bearing
adapter to an at
rest position relative to the sideframe.
These and other aspects and features of the invention may be understood with
reference to the detailed descriptions of the invention and the accompanying
illustrations as
set forth below.
Brief Description of the Figures
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 principles and aspects of the present invention,
and in which:
Figure la shows an isometric view of an example of an embodiment of a railroad
car
truck according to an aspect of the present invention;
Figure lb shows a side view of the railroad car truck of Figure la;
Figure le shows a top view of the railroad car truck of Figure la;
Figure id is a split view showing, in one half an end view of the truck of
Figure la,
and in the other half and a section taken level with the truck center;
Figure le shows a spring layout for the truck of Figurel a;
Figure if shows an isometric view of an alternate embodiment of railroad car
truck to
that of Figure la;
Figure lg shows a top view of the railroad car truck of Figure if;
Figure lh shows a side view of the railroad car truck of Figure lf;
Figure li shows an exploded view of a portion of a truck similar to that of
Figure if;
Figure lj is an exploded, sectioned view of an example of an alternate three
piece truck
to that of Figure la, having dampers mounted along the spring group
centerlines;
Figure lk shows a force schematic for four cornered damper arrangements
generally,
such as , for example, in the trucks of Figures la, if, li and Figure 14a;
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Figure 2a is an enlarged detail of a side view of a truck such as the truck of
Figure 1 b,
1 g, ii or lj taken at the sideframe pedestal to bearing adapter interface;
Figure 2b shows a lateral cross-section through the sideframe pedestal to
bearing
adapter interface of Figure 2a, taken at the wheelset axle centreline;
Figure 2c shows the cross-section of Figure 2b in a laterally deflected
condition;
Figure 2d is a longitudinal section of the pedestal seat to bearing adapter
interface of
Figure 2a, on the longitudinal plane of symmetry of the bearing adapter;
Figure 2e shows the longitudinal section of Figure 2d as longitudinally
deflected;
Figure 2f shows a top view of the detail of Figure 2a;
Figure 2g shows a staggered section of the bearing adapter of Figure 2a, on
section
lines '2g ¨ 2g' of Figure 2a;
Figure 3a shows a top view of an embodiment of bearing adapter and pedestal
seat
such as could be used in a side frame pedestal similar to that of Figure 2a,
with the seat inverted to reveal a female depression formed therein for
engagement with the bearing adapter;
Figure 3b shows a side view of the bearing adapter and seat of Figure 3a;
Figure 3c shows a longitudinal section of the bearing adapter of Figure 3a
taken on
section '3c ¨ 3c' of Figure 3d;
Figure 3d shows an end view of the bearing adapter and pedestal seat of Figure
3a;
Figure 3e shows a transverse section of the bearing adapter of Figure 3a,
taken on the
wheelset axle centreline;
Figure 3f shows a progression of longitudinal sectional profiles for the
bearing
adapter and seat of Figure 3a;
Figure 3g shows a progression of lateral sectional profiles for the bearing
adapter and
seat of Figure 3a;
Figure 3h is a section in the transverse plane of symmetry of a bearing
adapter and
pedestal seat pair like that of Figure 3e, with inverted rocker and seat
portions;
Figure 31 shows a cross-section on the longitudinal plane of symmetry of the
bearing
adapter and pedestal seat pair of Figure 3h;
Figure 4a shows an isometric view of an alternate embodiment of bearing
adapter and
pedestal seat to that of Figure 3a having a fully curved upper surface;
Figure 4b shows a side view of the bearing adapter and seat of Figure 4a;
Figure 4c shows an end view of the bearing adapter and seat of Figure 4a;
Figure 4d shows a cross-section of the bearing adapter and pedestal seat of
Figure 4a
taken on the longitudinal plane of symmetry;
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Figure 4e shows a cross-section of the bearing adapter and pedestal seat of
Figure 4a
taken on the transverse plane of symmetry;
Figure 5a shows a top view of an alternate bearing adapter and an inverted
view of
an alternate female pedestal seat to that of Figure 3a;
Figure 5b shows a longitudinal section of the bearing adapter of Figure 5a;
Figure 5c shows an end view of the bearing adapter and seat of Figure 5a;
Figure 6a shows an isometric view of a further embodiment of bearing adapter
and
seat combination to that of Figure 3a, in which the bearing adapter and
pedestal seat have saddle shaped engagement interfaces;
Figure 6b shows an end view of the bearing adapter and pedestal seat of Figure
6a;
Figure 6c shows a side view of the bearing adapter and pedestal seat of Figure
6a;
Figure 6d is a lateral section of the adapter and pedestal seat of Figure 6a;
Figure 6e is a longitudinal section of the adapter and pedestal seat of Figure
6a;
Figure 6f shows progressive longitudinal profiles for the bearing adapter and
pedestal
seat of Figure 6a;
Figure 6g shows progressive transverse profiles for the bearing adapter and
pedestal
seat of Figure 6f;
Figure 6h shows a transverse cross section of a bearing adapter and pedestal
seat pair
having an inverted interface to that of Figure 6a;
Figure 61 shows a longitudinal cross section for the bearing adapter and
pedestal seat
pair of Figure 6h;
Figure 7a shows an exploded side view of a further alternate bearing adapter
and seat
combination to that of Figure 3a, having a pair of cylindrical rocker
elements,
and a pivoted connection therebetween;
Figure 7b shows an exploded end view of the bearing adapter and seat of Figure
7a;
Figure 7c shows a cross-section of the bearing adapter and seat of Figure 7a,
as
assembled, taken on the longitudinal centreline thereof;
Figure 7d shows a cross-section of the bearing adapter and seat of Figure 7a,
as
assembled, taken on the transverse centreline thereof;
Figure 8a is an exploded end view of an alternate version of bearing adapter
and seat
assembly to that of Figure 7a having an elastomeric intermediate member;
Figure 8b shows an exploded side view of the assembly of Figure 8a;
Figure 9a is a side view of alternate assembly to that of Figure 3a or 6a,
employing
an elastomeric shear pad and a laterally swinging rocker;
Figure 9b shows a transverse cross-section of the assembly of Figure 9a, taken
on the
axle center line thereof;
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Figure 9c shows a cross section of the assembly of Figure 9a taken on the
longitudinal plane of symmetry of the bearing adapter;
Figure 9d shows a sectional view of the alternate assembly of Figure 9a, as
viewed
from above, taken on the staggered section indicated as '9d ¨ 9d';
Figure 9e shows an end view of an alternate rocker combination employing an
elastomeric pad;
Figure 9f shows a perspective view of an alternate pad combination to that of
Figure 9e;
Figure 10a is a view of a bearing adapter for use in the assembly of Figure
9a;
Figure 10b shows a top view of the bearing adapter of Figure 10a;
Figure 10c shows a longitudinal cross-section of the bearing adapter of Figure
10a;
Figure lla shows an isometric view of a pad adapter for the assembly of Figure
9a;
Figure lib shows a top view of the pad adapter of Figure 11a;
Figure 11c shows a side view of the pad adapter of Figure 11a;
Figure lid shows a half cross-section of the pad adapter of Figure 11a;
Figure lle shows an isometric view of a rocker for the pad adapter of Figure
11a;
Figure llf shows a top view of the rocker of Figure 11a;
Figure hg shows an end view of the rocker of Figure 11a;
Figure 12a shows an exploded isometric view of the assembly of Figure 12a;
Figure 12b shows an alternate embodiment of bearing adapter to pedestal seat
interface
to that of Figure 12a;
Figure 12c shows a sectional view of the assembly of Figure 12b; taken on a
longitudinal-vertical plane of symmetry thereof;
Figure 12d shows a stepped sectional view of a detail of the assembly of
Figure 12b
taken on 12d ¨ 12d' of Figure 12c;
Figure 12e shows an exploded view of another alternative embodiment of bearing
adapter to pedestal seat interface to that of Figure 12a;
Figure 12f shows an alternate style of wear plate for use in some embodiments
of the
bearing adapter to pedestal seat interface of, for example, Figure 12c;
Figure 12g shows a quartered isometric section the wear plate of Figure 12f as
installed;
Figure 13a shows an isometric view of a retainer pad of the assembly of Figure
12a,
taken from above, and in front of one corner;
Figure 13b is an isometric view from above and behind the retainer pad of
Figure 13a;
Figure 13c is a bottom view of the retainer pad of Figure 13a;
Figure 13d is a front view of the retainer pad of Figure 13a;
Figure 13e is a section on '13e ¨ 13e' of Figure 13d of the retainer pad of
Figure 13a;
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_
Figure 14a shows an isometric view of an alternate three piece truck to that
of Figure la;
Figure 14b shows a side view of the three piece truck of Figure 14a;
Figure 14c shows a top view of half of the three piece truck of Figure 14b;
Figure 14d shows a partial section of the truck of Figure 14b taken on `14d ¨
14d';
Figure 14e shows a partial isometric view of the truck bolster of the three
piece truck of
Figure 14a showing friction damper seats;
Figure 15a shows a side view of an alternate three piece truck to that of
Figure 14a;
Figure 15b shows a top view of half of the three piece truck of Figure 15a;
and
Figure 15c shows a partial section of the truck of Figure 15a taken on '15c ¨
15c';
Figure 15d shows an exploded isometric view of the bolster and side frame
assembly of
Figure 15a, in which horizontally acting springs drive constant force dampers;
Figure 15e shows an enlarged view of the side-by-side double damper
arrangement of
Figure 15d;
Figure 16a shows an alternate version of the bolster of Figure 14e, with a
double sized
damper pocket for seating a large single wedge having a welded insert;
Figure 16b shows an alternate dual wedge for a truck bolster like that of
Figure 16a;
Figure 17a shows an alternate bolster, similar to that of Figure 14a, with a
pair of spaced
apart bolster pockets, and inserts with primary and secondary wedge angles;
Figure 17b shows an alternate bolster, similar to that of Figure 17a, and
split wedges;
Figure 18a shows a bolster similar to that of Figure 14a, having a wedge
pocket having
primary and secondary angles and a split wedge arrangement for use therewith;
Figure 18b shows an alternate stepped single wedge for the bolster of Figure
18a;
Figure 18c is a view looking along a plane on the primary angle of the split
wedge of
Figure 18a relative to the bolster pocket;
Figure 18d is a view looking along a plane on the primary angle of the stepped
wedge of
Figure 18b relative to the bolster pocket;
Figure 19a shows an alternate bolster and wedge arrangement to that of Figure
17b,
having secondary wedge angles;
Figure 19b shows an alternate, split wedge arrangement for the bolster of
Figure 19a;
Figure 19c is a section of a stepped damper for use with a bolster as in
Figure 19a;
Figure 19d shows an alternate stepped damper to that of Figure 19c;
Figure 20a is a section of Figure 14b showing a replaceable side frame wear
plate;
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Figure 20b is a sectional view of the side frame of Figure 20a with the near
end of the
side frame sectioned, and the nearer wear plate removed to show the location
of
the wear plate of Figure 20a;
Figure 20c shows a compound bolster pocket for the bolster of Figure 20a;
Figure 20d is a side view detail of the bolster pocket of Figure 20c, as
installed;
Figure 20e shows an isometric detail of a split wedge version and a single
wedge version
of wedges for use in the compound bolster pocket of Figure 20c;
Figure 20f shows an alternate, stepped steeper angle profile for the primary
angle of the
wedge of the bolster pocket of Figure 20d;
Figure 20g shows a welded insert having a profile for mating engagement with
the
corresponding face of the bolster pocket of Figure 20d;
Figure 21a is a cross-section of an alternate damper such as may be used, for
example,
in the bolster of the trucks of Figures la, if, ii, lj and 14a;
Figure 21b shows an isometric view of the damper of Figure 21a with friction
modifying pads removed;
Figure 21c is a reverse view of a friction modifying pad of the damper of
Figure 21a;
Figure 22a is a front view of a friction damper for a truck such as that of
Figure la;
Figure 22b shows a side view of the damper of Figure 22a;
Figure 22c shows a rear view of the damper of Figure 22b;
Figure 22d shows a top view of the damper of Figure 22a;
Figure 22e shows a cross-sectional view on the centerline of the damper of
Figure 22a
taken on section '22e ¨ 22e' of Figure 22c;
Figure 22f shows a cross-section of the damper of Figure 22a taken on section
'22f ¨
22f of Figure 22e;
Figure 22g shows an isometric view of an alternate damper to that of Figure
22a having
a friction modifying side face pad; and
Figure 22h shows an isometric view of a further alternate damper to that of
Figure 22a,
having a "wrap-around" friction modifying pad.
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 principles of
the present invention. These examples are provided for the purposes of
explanation, and not
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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 and truck components. 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 (GWR) of 142,000 lbs. Similarly, "50 Ton"
corresponds
to 177,000 lbs., "70 Ton" corresponds to 220,000 lbs., "100 Ton" corresponds
to 263,000
lbs., and "125 Ton" corresponds to 315,000 lbs. In each case the load limit
per truck is then
half the maximum gross car weight on rail. Two other types of truck are the
"110 Ton" truck
for railcars having a 286,000 lbs. GWR and the "70 Ton Special" low profile
truck
sometimes used for auto rack cars. Given that the rail road car trucks
described herein tend to
have both longitudinal and transverse axes of symmetry, a description of one
half of an
assembly may generally also be intended to describe the other half as well,
allowing for
differences between right hand and left hand parts.
This application refers to friction dampers for rail road car trucks, and
multiple
friction damper systems. There are several types of damper arrangements, as
shown at pp.
715 - 716 of the /997 Car and Locomotive Cyclopedia. Double damper
arrangements are
shown and described in co-pending US Patent application, 10 / 210,797 entitled
"Rail Road
Freight Car With Damped
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Suspension", published as US Patent Application Publication No. US
2003/0041772
Al, on March 6, 2003. Each of the arrangements of dampers shown at pp. 715 to
716 of the
1997 Car and Locomotive Cyclopedia can be modified according to the principles
of the
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 dealing with friction dampers, there is discussion of damper wedges.
Several
variations of damper wedges are discussed herewithin. In terms of general
nomenclature, the
wedges tend to be mounted within an angled "bolster pocket" formed in an end
of the truck
bolster. In cross-section, each wedge may then have a generally triangular
shape, one side of
the triangle being, or having, a bearing face, a second side which might be
termed the
bottom, or base, forming a spring seat, and the third side being a sloped side
or hypotenuse
between the other two sides. The first side may tend to have a substantially
planar bearing
face for vertical sliding engagement against one of the sideframe columns. The
second face
may not be a face, as such, but rather may have the form of a socket for
receiving the upper
end of one of the springs of a spring group. Although the third face, or
hypotenuse, may
appear to be generally planar, it may tend to have a slight crown, having a
radius of curvature
of perhaps 60". The crown may extend along and across the slope. The end faces
of the
wedges may be generally flat, and may be provided with a coating, surface
treatment, shim,
or low friction pad to give a smooth sliding engagement with the sides of the
bolster pocket,
or with the adjacent side of another independently slidable damper wedge, as
may be.
The bearing face of the damper may tend to be planar, and may tend to be in
planar
contact with the mating surface of the sideframe column wear plate. During
railcar
operation, the sideframe may tend to rotate, or pivot, through a small range
of angular
deflection about the end of the truck bolster in the manner of a walking beam
to yield wheel
load equalisation. The slight crown on the slope face of the damper may tend
to
accommodate this pivoting motion by allowing the damper to rock somewhat
relative to the
generally inclined face of the bolster pocket while the planar bearing face
remains in planar
contact with the wear plate of the sideframe column. Although the slope face
may have a
slight crown, for the purposes of this description it will be described as the
slope face or as
the hypotenuse, and will be considered to be a substantially flat face as a
general
approximation.
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_
In the terminology herein, wedges have a primary angle a, namely the included
angle
between (a) the sloped damper pocket face mounted to the truck bolster, and
(b) the side
frame column face, as seen looking from the end of the bolster toward the
truck center. This
is the included angle described above. In some embodiments, a secondary angle
may be
defined in the plane of angle a, namely a plane perpendicular to the vertical
longitudinal
plane of the (undeflected) side frame, tilted from the vertical at the primary
angle. That is,
this plane is parallel to the (undeflected) long axis of the truck bolster,
and taken as if
sighting along the back side (hypotenuse) of the damper.
The secondary angle p is defined as the lateral rake angle seen when looking
at the
damper parallel to the plane of angle a. As the suspension works in response
to track
perturbations, the wedge forces acting on the secondary angle will tend to
urge the damper
either inboard or outboard according to the angle chosen. Inasmuch as the
tapered region of
the wedge may be quite thin in terms of vertical through-thickness, it may be
desirable to
step the sliding face of the wedge (and the co-operating face of the bolster
seat) into two or
more portions. This may be particularly so if the primary angle of the wedge
is large.
General Description of Truck Features
Figures la to le and if to li provide examples of trucks 20 and 22 embodying
an
aspect of the invention. Trucks 20 and 22 of Figures la and if may have the
same, or
generally similar, features and similar construction, although they may differ
in pendulum
length, spring stiffness, wheelbase, window width and height, and damping
arrangement.
That is, truck 20 of Figure la may tend to have a longer wheelbase (from 73
inches to 86
inches, possibly between 80 ¨ 84 inches for truck 20, as opposed to a
wheelbase of 63 ¨ 73
inches for truck 22), may tend to have a main spring group having a softer
vertical spring
rate, and a four cornered damper group that may have different primary and
secondary angles
on the damper wedges. While either truck may be suitable for a variety of
general purpose
uses, truck 20 may be optimized for use in rail road cars for carrying
relatively low density,
high value lading, such as automobiles or consumer products, for example,
whereas truck 22
may be optimized for carrying denser semi-finished industrial goods, such as
might be
carried in rail road freight cars for transporting rolls of paper, for
example. The various
features of the two truck types may be interchanged, and are intended to be
illustrative of a
wide range of truck types in which the present invention may be employed.
Notwithstanding
possible differences in size, generally similar features are given the same
part numbers.
Trucks 20 and 22 are symmetrical about both their longitudinal and transverse
centreline
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axes. 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.
Trucks 20 and 22 each have a truck bolster, identified as 24, and sideframes,
identified as 26. Each sideframe 26 has a generally rectangular window 28 that
accommodates one of the ends 30 of the bolster 24. The upper boundary of
window 28 is
defined by the sideframe arch, or compression member identified as top chord
member 32,
and the bottom of window 28 is defined by a tension member identified as
bottom chord 34.
The fore and aft vertical sides of window 28 are defined by sideframe columns
36.
The ends of the tension member sweep up to meet the compression member. At
each
of the swept-up ends of sideframe 26 there are sideframe pedestal fittings, or
pedestal seats
38. Each fitting 38 accommodates an upper fitting, which may be a rocker or a
seat, as
described and discussed below. This upper fitting, whichever it may be, is
indicated
generically as 40. Fitting 40 engages a mating fitting 42 of the upper surface
of a bearing
adapter 44. Bearing adapter 44 engages a bearing 46 mounted on one of the ends
of one of
the axles 48 of the truck adjacent one of the wheels 50. A fitting 40 is
located in each of the
fore and aft pedestal fittings 38, the fittings 40 being longitudinally
aligned such that the
sideframe can swing transversely relative to the rolling direction of the
truck.
The relationship of the mating fittings 40 and 42 is described at greater
length below.
The relationship of these fittings determines part of the overall relationship
between an end
of one of the axles of one of the wheelsets and the sideframe pedestal. That
is, in
determining the overall response, the degrees of freedom of the mounting of
the axle end in
the sideframe pedestal involve a dynamic interface across an assembly of
parts, such as may
be termed a wheelset to sideframe interface assembly, that may include the
bearing, the
bearing adapter, an elastomeric pad, if used, a rocker if used, and the
pedestal seat mounted
in the roof of the sideframe pedestal. Several different embodiments of this
wheelset to
sideframe interface assembly are described below. To the extent that the
bearing has a single
degree of freedom, namely rotation of the shaft about the lateral axis,
analysis of the
assembly can be focused on the bearing to pedestal seat interface assembly, or
on the bearing
adapter to pedestal seat interface assembly. For the purposes of this
description, items 40
and 42 are intended generically to represent the combination of features of a
bearing adapter
and pedestal seat assembly defining the interface between the roof of the
sideframe pedestal
and the bearing adapter, and the six degrees of freedom of motion at that
interface, namely
vertical, longitudinal and transverse translation (i.e., translation in the z,
x, and y directions)
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and pitching, rolling, and yawing (i.e., rotational motion about the y, x, and
z axes
respectively) in response to dynamic inputs. In general, this interface is
nearly infinitely stiff
in vertical translation.
Continuing with the general description of the trucks, the bottom chord or
tension
member of sideframe 26 may have a basket plate, or lower spring seat 52
rigidly mounted to
bottom chord 34, to give a rigid orientation relative to window 28, and to
sideframe 26 in
general. Although trucks 20 and 22 are free of unsprung lateral cross-bracing,
whether in the
nature of a transom or lateral rods, in the event that truck 20 or truck 22 is
taken to represent
a "swing motion" truck with a transom or other cross bracing, the lower rocker
platform of
spring seat 52 may be mounted on a rocker, to permit lateral rocking relative
to sideframe 26.
Spring seat 52 may have retainers for engaging the springs 54 of a spring set,
or spring
group, 56, whether internal bosses, or a peripheral lip for discouraging the
escape of the
bottom ends of the springs. The spring group, or spring set 56, is captured
between the distal
end 30 of bolster 24 and spring seat 52, being placed under compression by the
weight of the
rail car body and lading that bears upon bolster 24 from above.
Bolster 24 has double, inboard and outboard, bolster pockets 60, 62 on each
face of
the bolster at the outboard end (i.e., for a total of 8 bolster pockets per
bolster, 4 at each end).
Bolster pockets 60, 62 accommodate a pair of first and second, laterally
inboard and laterally
outboard friction damper wedges 64, 66 and 68, 70, respectively. Each bolster
pocket 60, 62
has an inclined face, or damper seat 72, that mates with a similarly inclined
hypotenuse face
74 of the damper wedge, 64, 66, 68 and 70. Wedges 64, 66 each sit over a
first, inboard
corner spring 76, 78, and wedges 68, 70 each sit over a second, outboard
corner spring 80,
82. Angled faces 74 of wedges 64, 66 and 68, 70 ride against the angled face
of seat 72.
A middle end spring 96 bears on the underside of a land 98 located
intermediate
bolster pockets 60 and 62. The top ends of the central row of springs, 100,
seat under the
main central portion 102 of the end of bolster 24. 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. Friction damping is provided by
damping wedges 64,
66 and 68, 70 (that seat in mating bolster pockets 60, 62 that have inclined
damper seats 72
when the vertical sliding faces 90 of the friction damper wedges 64, 66 and
68, 70 then ride
up and down on friction wear plates 92 mounted to the inwardly facing surfaces
of sideframe
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columns 36. In this way the kinetic energy of the motion is, in some measure,
converted
through friction to heat. This friction may tend to damp out the motion of the
bolster relative
to the sideframes.
When a lateral perturbation is passed to wheels 50 by the rails, rigid axles
48 may
tend to cause both sideframes 26 to deflect in the same direction. The
reaction of sideframes
26 is to swing, like pendula, on the upper rockers. The weight of the pendulum
and the
reactive force arising from the twisting of the springs may then tend to urge
the sideframes
back to their initial position. The tendency to oscillate harmonically due to
the track
perturbation may tend to be damped out by the friction of the dampers on the
wear plates 92.
As compared to a bolster with single dampers as shown in Figure 1j, for
example, the
use of spaced apart pairs of dampers 64, 68 may tend to give a larger moment
arm, as
indicated by dimension "2M" in Figure li, for resisting parallelogram
deformation of truck
20, 22 more generally. Use of doubled dampers this way may yield a greater
restorative
"squaring" force to return the truck to a square orientation than for a single
damper alone.
That is, in parallelogram deformation, or lozenging, the differential
compression of one
diagonal pair of springs (e.g., inboard spring 76 and outboard spring 82 may
be more
pronouncedly compressed) relative to the other diagonal pair of springs (e.g.,
inboard spring
78 and outboard spring 80 may be less pronouncedly compressed than springs 76
and 80)
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). 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.
The foregoing explanation has been given in the context of trucks 20 and 22,
each of
which has a spring group that has three rows facing the sideframe columns. The
restorative
moment couple of a four-cornered damper layout can also be explained in the
context of a
truck having a 2 row spring group arrangement facing the dampers, as in truck
400 of
Figures 14a to 14e. For the purposes of conceptual visualisation, the normal
force on the
friction face of any of the dampers can be taken as a pressure field whose
effect can be
approximated by a point load acting at the centroid of the pressure field and
whose
magnitude is equal to the integrated value of the pressure field over its
area. The center of
this distributed force, acting on the inboard friction face of wedge 440
against column 428
can be thought of as a point load offset transversely relative to the
diagonally outboard
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friction face of wedge 443 against column 430 by a distance that is notionally
twice
dimension `1,' shown in the conceptual sketch of Figure lk. In the example of
Figure 14a,
this distance, 2L, is about one full diameter of the large spring coils in the
spring set. The
restoring moment in such a case would be, conceptually, MR = [(F1 + F3) - (F2
+ F4)]L. As
indicated by the formulae on the conceptual sketch of Figure lk, the
difference between the
inboard and outboard forces on each side of the bolster is proportional to the
angle of
deflection E of the truck bolster relative to the side frame, and since the
normal forces due to
static deflection xo may tend to cancel out, MR = 41kcTan(E)Tan(0)L, where 0
is the primary
angle of the damper (generally illustrated as alpha herein), and kc is the
vertical spring
constant of the coil upon which the damper sits and is biased.
In the various arrangements of spring groups 2 x 4, 3 x 3, 3:2:3 or 3 x 5
group,
dampers may be mounted over each of four corner positions. The portion of
spring force
acting under the damper wedges may be in the 25 ¨ 50 % range for springs of
equal stiffness.
If not of equal stiffness, the portion of spring force acting under the
dampers may be in the
range of perhaps 20 % to 35 %. The coil groups can be of unequal stiffness if
inner coils are
used in some springs and not in others, or if springs of differing spring
constant are used.
In the view of the present inventors, it may be that an enhanced tendency to
encourage squareness at the bolster to sideframe interface (i.e., through the
use of four
cornered damper groups) may tend to reduce reliance on squareness at the
pedestal to
wheelset axle interface. This, in turn, may tend to provide an opportunity to
employ a
torsionally compliant (about the vertical axis) axle to pedestal interface
assembly, and to
permit a measure of self steering.
Bearing plate 92 (Figure la) is significantly wider than the through thickness
of the
sideframes more generally, as measured, for example, at the pedestals, and may
tend to be
wider than has been conventionally common. This additional width corresponds
to the
additional overall damper span width measured fully across the damper pairs,
plus lateral
travel as noted above, typically allowing 1 V2 (+/-) 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 92 has the
width of three coils,
plus allowance to accommodate 1 V2 (+/-) inches of travel to either side for a
total, double
amplitude travel of 3" (+/-). Bolster 24 has inboard and outboard gibs 106,
108 respectively,
that bound the lateral motion of bolster 24 relative to sideframe columns 36.
This motion
allowance may advantageously be in the range of +/- 1 1/8 to 1 3/4 in., and
may be in the range
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of 1 3/16 to 1 9/16 in., and can be set, for example, at 1 1/2 in. or 1 1/4
in. of lateral travel to
either side of a neutral, or centered, position when the sideframe is
undeflected.
The lower ends of the springs of the entire spring group, identified generally
as 58,
seat in lower spring seat 52. Lower spring seat 52 may be laid out as a tray
with an upturned
rectangular peripheral lip. Although truck 20 employs a spring group in a 5 x
3 arrangement,
and truck 22 employs a spring group in a 3 x 3 arrangement, this is intended
to be generic,
and to represent a range of variations. They may represent a 2 x 4
arrangement, a 3:2:3
arrangement, and may include a hydraulic snubber, or such other arrangement of
springs may
be appropriate for the given service for the railcar for which the truck is
intended.
Further, in typical friction damper wedges, the enclosed angle of the wedge
tends to
be somewhat less than 35 degrees measured from the vertical face to the sloped
face against
the bolster. As the wedge angle decreases toward 30 degrees, the tendency of
the wedge to
jam in place may tend to increase. Conventionally the wedge is driven by a
single spring in a
large group. The portion of the vertical spring force acting on the damper
wedges can be less
than 15 % of the group total. Damper wedges 64, 66 and 68, 70 may sit over the
coil
positions of 4/9 of a 3 rows x 3 columns spring group, which may account for
15 % to 35 %
of the overall spring rate of the group. In the embodiment of Figure 14b, it
may be 50 % of
the group total (i.e., 4 of 8 equal springs). There are three related
variables that are subject to
optimization, namely (a) the choice, and layout of the various springs, (i.e.,
general
arrangement of rows and columns), (b) the use (or not) of outer, inner, and
inner-inner coils,
use of side coils, whether outer and inner, and use of snubbers to determine
not only the
overall spring stiffness, but also the proportion of that stiffness to be
carried under the
dampers; and (c) the primary angle of the wedges. There are many possible
damper styles
and arrangements. In general, for the same proportion of vertical damping,
where a higher
proportion of the total spring stiffness is mounted under the dampers, the
corresponding
wedges 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
36). The use of
more springs, or more precisely, a greater portion of the overall spring
stiffness, under the
dampers, may permit the enclosed angle of wedges 440, 442 to be over 35
degrees. The
included angle may range from around 30 ¨ 35 degrees to perhaps as much as 60
¨ 65
degrees, with a more moderate range being in the range of 35 ¨ 45 degrees, or
thereabout.
The specific angle may tend to be a function of the specific spring
stiffnesses and spring
combinations actually employed.
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One way to encourage an increase in the hunting threshold may be 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 1/2",
giving a wheelbase
to track width ratio possibly as small as 1.12. At 6' ¨ 0" the ratio is
roughly 1.27. It may be
preferable to employ a wheelbase having a longer aspect ratio relative to the
track gauge.
In the case of truck 20, the size of the spring group may yield an opening
between the
vertical columns of sideframe more than 27 1/2 inches wide. Truck 20 may have
a greater
wheelbase length, indicated as WB (Figure 1c). WB may be greater than 73
inches, or, taken
as a ratio to the track gauge width, and may also be greater than 1.30 times
the track gauge
width. It may be greater than 80 inches, or more than 1.4 times the gauge
width, and in one
embodiment is greater than 1.5 times the track gauge width, being as great, or
greater than,
about 86 inches.
Rocker Description
The present inventors have noted that the rocking interface surface of the
bearing
adapter might have a crown, or a concave curvature, like a swing motion truck,
by which a
rolling contact on the rocker permits lateral swinging of the side frame. The
present
inventors have also noted, as shown and described herein, that the bearing
adapter to pedestal
seat interface might also have a fore-and-aft curvature, whether a crown or a
depression, and
that, if used as described by the inventors hereinbelow, this crown or
depression might tend
to present a more or less linear resistance to deflection in the longitudinal
direction, much as
a spring or elastomeric pad might do. The present inventors also note that it
may be
advantageous for the rockers to be self centering.
For surfaces in rolling contact on a compound curved surface (i.e., having
curvatures
in two directions) as shown and described by the present inventors
hereinbelow, the vertical
stiffness may again be approximated as infinite; the longitudinal stiffness in
translation at the
point of contact can also be taken as infinite, the assumption being that the
surfaces do not
slip; the lateral stiffness in translation at the point of contact can be
taken as infinite, again,
provided the surfaces do not slip. The rotational stiffness about the vertical
axis may be
taken as zero or approximately zero. By contrast, the angular stiffnesses
about the
longitudinal and transverse axes are non-trivial. The lateral angular
stiffnesses may tend to
determine the equivalent pendulum stiffnesses for the sideframe more
generally.
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Where a complex, two dimensional, curvature is used as suggested herein, the
torsional stiffness across the bearing adapter crown to pedestal seat roof
interface may be
taken as being zero, as noted above. Another observation of the present
inventors is that it is
desirable for the rockers to remain in rolling (i.e., static) contact, as
opposed to breaking free
and sliding, with resultant undesirable kinematic friction.
Where a truck already has an elastomeric bearing adapter pad, a fore-and-aft
rocker
may also be used to obtain as additional measure of self steering without
unduly softening
the lateral response of the bearing adapter to pedestal seat interface.
Alternatively,
depending on the properties and performance of the elastomeric pad, it may be
desirable to
employ a laterally swinging rocker as well as an elastomeric pad, such that a
measure of self
steering may be achieved with a side frame that rocks in the manner of a swing
motion truck.
The stiffness of a pendulum is directly proportional to the weight on the
pendulum.
Similarly, the drag on a rail car wheel, and the wear to the underlying track
structure is
proportional to the weight borne by the wheel. For this reason, the
desirability of self
steering may be greatest for a fully laden car, and a pendulum may tend to
maintain a general
proportionality between the amount of drag and the stiffness of the self-
steering mechanism.
Truck performance may vary with the friction characteristics of the bearing
surfaces
of the dampers used in the truck suspension. Conventional dampers have tended
to employ
dampers in which the dynamic and static co-efficients of friction may have
been significantly
different, yielding a stick-slip phenomenon that may not have been entirely
advantageous. In
the view of the present inventors it may be advantageous to combine the
feature of a self-
steering capability with dampers that have a reduced tendency to stick-slip
operation.
Furthermore, the present inventors have noted that while bearing adapters may
be
formed of relatively low cost materials, such as cast iron, where a rocker is
used as proposed
herein, it may be desirable to use an insert of a different material for the
rocker. The
inventors also propose that it may be desirable to employ a member that may
tend to center
the rocker on installation, and that may tend to perform an auxiliary
centering function to
tend to urge the rocker to operate from a desired minimum energy position.
Now considering the interface between the sideframe pedestal and the bearing
adapter,
the geometry and operation of an embodiment of bearing adapter and pedestal
seat assembly is
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first illustrated in the series of views of Figures 2a ¨ 2g. Bearing adapter
44 has a lower portion
112 that is formed to accommodate, and seat upon, bearing 46, that is itself
mounted on the end
of a shaft, namely an end of axle 48. Bearing adapter 44 has an upper portion
114 that has a
centrally located, upwardly protruding fitting in the nature of a male bearing
adapter interface
portion 116. A mating fitting, in the nature of a female rocker seat interface
portion 118 is
rigidly mounted within the roof 120 of the sideframe pedestal. To that end,
laterally extending
lugs 122 are mounted centrally with respect to pedestal roof 120. The upper
fitting 40,
whichever type it may be, has a body that is a plate having, along its
longitudinally extending,
lateral margins a set of upwardly extending lugs or ears, or tangs 124
separated by a notch, that
bracket, and tightly engage lugs 122, thereby locating upper fitting 40 in
position, with the back
of the plate 126 of fitting 40 abutting the flat, load transfer face of roof
120. In this instance,
upper fitting 40 is a pedestal seat fitting with a hollowed out female bearing
surface, namely
portion 118.
As shown in Figure 2g, when the sideframes are lowered over the wheel sets,
the end
reliefs, or channels 128 lying between corner abutments 132 seat between the
respective side
frame pedestal jaws 130. With the sideframes in place, bearing adapter 44 is
thus captured in
position with the male and female portions (116 and 118) of the adapter
interface in mating
engagement.
Male portion 116 (Figure 2d) has been formed to have a generally upwardly
facing
surface 142 that has both a first curvature n to permit rocking in the
longitudinal direction, and
a second curvature r2 (Figure 2c) to permit rocking (i.e. swing motion of the
sideframe) in the
transverse direction. Similarly, in the general case, female portion 118 has a
surface having a
first radius of curvature R1 in the longitudinal direction, and a second
radius of curvature R2 in
the transverse direction. The engagement of r1 with R1 tends to permit a
rocking motion in the
longitudinal direction when the wheel set exhibits a tendency to drag, with
rocking displacement
being generally linearly proportionate to the drag since wheel drag may be
proportional to
weight on the wheel. That is to say, the resistance to angular deflection is
proportional to weight
rather than being a fixed spring constant. This may tend to yield passive self-
steering in both
the light car and fully laden conditions. This relationship is shown in
Figures 2d and 2e. Figure
2d shows the centered, or at rest, non-deflected position of the longitudinal
rocking elements.
Figure 2e shows the rocking elements at their condition of maximum
longitudinal deflection.
Figure 2d represents a local, minimum potential energy condition for the
system. Figure 2e
represents a system in which the potential energy has been increased by virtue
of the work done
by drag force F acting longitudinally in the horizontal plane through the
center of the axle and
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bearing, CB. The present inventors have applied the following approximation
for this
longitudinal rocking motion:
F / along = klong = (W / L) [ [ (1 / L) / (1 /r1 ¨ 1 / Ri) ] ¨ 1]
Where:
'gong is the longitudinal constant of proportionality between longitudinal
force and
longitudinal deflection for the rocker.
F is a unit of longitudinal force, namely of drag on the wheel.
Olong is a unit of longitudinal deflection of the centreline of the axle.
W is the weight on the pendulum.
L is the distance from the centreline of the axle to the apex of male portion
116.
R1 is the longitudinal radius of curvature of the female hollow in the
pedestal seat 38.
r1 is the longitudinal radius of curvature of the crown of the male portion
116 on the
bearing adapter.
It will be noted that R1 is greater than r1 in this relationship, and (1 / L)
is greater than
[(1 / ri) ¨ (1 /R1)].
The limit of travel in the longitudinal direction is reached when the end face
134 of
bearing adapter 44 extending between corner abutments 132, comes into contact
with one or
other of the travel limiting abutment faces 136 of jaws 130. In the general
case, the deflection
can be characterized either by the angular displacement of the centreline of
the axle as 01, or by
the angular displacement of the contact point of the rocker on radius r1,
indicated as 02. End
face 134 of bearing adapter 44 is planar, and is relieved, or inclined, at an
angle TI from the
vertical. As shown in Figure 2g, abutment face 136 may have a round,
cylindrical arc, with the
major axis of the cylinder extending vertically. A typical maximum radius R3
for this surface is
34 inches. When bearing adapter 44 is fully deflected through angle It end
face 134 is intended
to meet abutment face 136 in line contact. When this occurs, further rocking
motion of the male
surface against the female surface is inhibited. Thus jaws 130 constrain the
arcuate deflection of
bearing adapter 44 to a limited range. A typical range for ii might be about 3
degrees of arc. A
typical maximum value of 8
-long may be about +/- 3/16" to either side of the vertical, at rest,
center line.
Similarly, as shown in Figures 2b and 2c, in the transverse direction, the
engagement of
r2 with R2 may tend to permit lateral rocking motion, in the manner of a swing
motion truck.
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Figure 2b shows a centered, at rest, minimum potential energy position of the
lateral rocking
system. Figure 2c shows the same system in a laterally deflected condition. In
this instance 82
is roughly (Lpendulum r2)Sir19, where, for small angles Sing, is approximately
equal to cp. The
present inventors have applied the following approximation for this condition,
for small angular
deflections:
kpeaduian, = (F2/62) = (W/Lpend.)[[ (1 Lpend.) ((1 RRocker) (1 / RSeat))1 + 1]
where:
kpendulum = the lateral stiffness of the pendulum
F2 = the force per unit of lateral deflection applied at the bottom spring
seat
82 = a unit of lateral deflection
W = the weight borne by the pendulum
Lpend.= the length of the pendulum, being the distance from the contact
surface of the
bearing adapter to the bottom of the pendulum at the spring seat
RRocker = r2 = the lateral radius of curvature of the rocker surface
RSeat = R2 = the lateral radius of curvature of the rocker seat
Where Rseat and RRocker are of similar magnitude, and are not unduly small
relative to
L, the pendulum may tend to have a relatively large lateral deflection
constant. It will be
noted that where Rseat is large as compared to L or RRocker, or both, and can
be approximated
as infinite (i.e., a flat surface), this formula simplifies to:
kpendulum = (Flateral Olateral) = (W Lpendulum){(Rcurvature Lpendulum) + 1]
where:
kpendulum = the lateral stiffness of the pendulum
Flateral = the force per unit of lateral deflection
Olateral = 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 number in the
denominator, and the design weight in the numerator yields a length,
effectively equivalent to
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a pendulum length if the entire lateral stiffness came from an equivalent
pendulum according
to Leg = W / klateral total
When a lateral force is applied at the centetplate of the truck bolster, a
reaction force is,
ultimately, provided at the meeting of the wheels with the rail. The lateral
force is transmitted
from the bolster into the main spring groups, and then into a lateral force in
the spring seats to
deflect the bottom of the pendulum. The reaction is carried to the bearing
adapter, and hence
into the top of the pendulum. The pendulum will then deflect until the weight
on the pendulum,
multiplied by the moment arm of the deflected pendulum is sufficient to
balance the moment of
the lateral moment couple acting on the pendulum.
It may be noted that this bearing adapter to pedestal seat interface assembly
is biased by
gravity acting on the pendulum toward a central, or "at rest" position, where
there is a local
minimum of the potential energy in the system. The fully deflected position
shown in Figure 2c
may correspond to a deflection from vertical of the order of rather less than
10 degrees (and
preferably less than 5 degrees) to either side of center, the actual maximum
being determined by
the spacing of gibbs 106 and 108 relative to plate 104. Although in the
general case R1 and R2
may be different such that the female surface is a section of the outside of a
torus, it may be
convenient, and desirable, for R1 and R2 to be the same, i.e., so that the
bearing surface of the
female fitting is formed as a portion of a spherical surface, having neither a
major nor a minor
axis, but merely being formed on a spherical radius. R1 and R2 give a self-
centering tendency.
That tendency may be quite gentle.
Further, and again in the general condition, the smallest of R1 and R2 may be
equal to or
larger than the largest of r1 and r2. If so, then the contact point may have
little, if any, ability to
transmit torsion acting about an axis normal to the point of contact, so the
lateral and
longitudinal rocking motions may tend to be torsionally de-coupled, and hence
it may be said
that relative to this degree of freedom (rotation about the vertical, or
substantially vertical axis)
the interface is torsionally compliant. For small angular deflections, the
torsional stiffness
about the normal axis at the contact point, this condition may sometimes be
satisfied even
where the smaller of the female radii is substantially less than the largest
male radius.
Although it is possible for r1 and r2 to be the same, such that the crowned
surface of the
bearing adapter (or the pedestal seat, if the relationship is inverted) is a
portion of a spherical
surface, in the general case r1 and r2 may be different, with r1 perhaps
tending to be larger,
possibly significantly larger, than r2. In the event that r1 and r2, are the
same, then R1 and R2
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need not be. In the general case, whether or not r1 and r2 are equal, then R1
and R2 may be the
same or different. Where r1 and r2 are different, the male fitting engagement
surface may be a
section of the surface of a torus. It may also be noted that, provided the
system may tend to
return to a local minimum energy state (i.e., that is self-restorative in
normal operation) in the
limit either or both of R1 and R2 may be infinitely large such that either a
cylindrical section is
formed or, when both are infinitely large, a planar surface may be formed. In
the further
alternative, it may be that r1 = r2, and R1 = R2.
Constant radii of curvature have been discussed thus far. While it may be
practical to
make mating male and female engagement surfaces with circular arcs and
constant radii of
curvature, alternate arcs may also be considered. For example, the surfaces
may be elliptic, or
may be parabolic. The surfaces may have a smaller radius of curvature in a
central portion to
give a generally softer lateral response for low amplitude perturbations (and
possibly relatively
high frequency), with a larger radius of curvature at greater lateral angular
deflection to provide
a stiffer response as the magnitude of deflection increases. Alternatively, in
the longitudinal
direction, there may be a central portion with a large radius of curvature to
yield a relatively stiff
response until the moment couple tending to cause passive self steering builds
up, and then a
smaller radius of curvature to ease self steering once a certain threshold has
been reached. The
arrangement of Figure 2a can be inverted, such that the female engagement
fitting portion may
be part of bearing adapter 44, and the male fitting may be mounted to the
pedestal roof 120.
The embodiment of bearing adapter to pedestal seat interface described above
and
shown in Figures 2a ¨ 2g, may tend to have very high stiffness in vertical
translation,
longitudinal translation, and transverse translation, to the extent that non-
slip, rolling contact is
maintained. To the extent that there is point contact between the compound
curvature surface of
the male portion and the female portion, and the smallest radius of curvature
of the female
portion is larger than the largest radius of curvature of the male portion,
the torsional resistance
to relative rotation about the vertical, or z axis may tend to be minimal, if
not zero, (i.e., it is
highly torsionally compliant) and, for the purposes of approximation,
torsional resistance may
be taken as being zero. There may tend to be little or no torsional moment
passed through the
bearing adapter interface. Rotation about the lateral and longitudinal axes of
rotation, namely
the x and y axes, is non-trivial, and may correspond to the equations provided
above.
The rocker surfaces herein may tend to be formed of a relatively hard
material, which
may be a metal or metal alloy material, such as a steel. Such materials may
have elastic
deformation at the location of rocking contact in a manner analogous to that
of journal or ball
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bearings. Nonetheless, the rockers may be taken as approximating the ideal
rolling point or line
contact (as may be) of infinitely stiff members. This is to be distinguished
from materials in
which deflection of an elastomeric element be it a pad, or block, of whatever
shape, may be
intended to determine a characteristic of the dynamic or static response of
the element.
In one embodiment the lateral rocking constant for a light car may be in the
range of
about 48,000 to 130,000 in-lbs per radian of angular deflection of the side
frame pendulum, or,
260,000 to 700,000 in-lbs per radian for a fully laded car, or more
generically, about 0.95 to 2.6
in-lbs per radian per pound of weight borne by the pendulum. Alternatively,
for a light (i.e.,
empty) car the stiffness of the pendulum may be in the range 3,200 to 15,000
lbs per inch, and
22,000 to 61,000 lbs per inch for a fully laden 110 ton truck, or, more
generically, in the range
of 0.06 to 0.160 lbs per inch of lateral deflection per pound weight borne by
the pendulum, as
measured at the bottom spring seat.
In one embodiment R1 = R2 = 15 inches, r1 = 8 ¨ 5/8 inches and r2 = 5". In
another
embodiment, R1 = R2 = 15 inches, and r1 = 10" and r2 = 8 ¨ 5/8" (+/-). In
another embodiment
= 8 5/8, r2 = 5", R1 = R2 = 12" in still another embodiment r1 = 12 Y2", r2 =
8 5/8 and R1 = R2
= 15". The radius of curvature of the male longitudinal rocker, r1, may be
less than 60 inches,
and may lie in the range of 5 to 40 inches, and may lie in the range of 8 to
20 inches, and may be
about 15 inches. R1 may be less than 100 inches, and may be in the range of 10
to 60 inches, or
in the narrower range of 12 to 40 inches, and may be in the range of 11/10 to
4 times the size of
r1. The radius of curvature of the male lateral rocker, r2, may be less than
about 25 or 30 in.,
being half, or less than half, of the 60 inch crown radius of bearing adapters
of trucks that might
not generally be considered to be "swing motion" trucks, and may lie in the
range of about 5 to
20 inches. r2 may lie in the range of about 8 to 16 inches, and may be about
10 inches. Where a
spherical male rocker is used on a spherical female cap, the male radius may
be in the range of
8 ¨ 10 in., and may be about 9 in.; the female radius may be in the range of
11 ¨ 13 in., and may
be about 12 in. Where a torus, or elliptical surface is employed, in one
embodiment the lateral
male radius may be about 7 in., the longitudinal male radius may be about 10
inches, the lateral
female radius may be about 12 in. and the longitudinal female radius may be
about 15 in.
Where a flat female rocker surface is used, and a male spherical surface is
used, the male radius
of curvature may be in the range of about 20 to about 50 in., and may lie in
the narrower range
of 30 to 40 in. Many combinations are possible, depending on loading, intended
use, and rocker
materials.
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Where line contact rocking motion is used, r2 may perhaps be somewhat smaller
than
otherwise, perhaps in the range of 3 to 10 inches, and perhaps being about 5
inches. R2 may be
less than 60 inches, and may be less than about 25 or 30 inches, then being
less than half the 60
inch crown radius noted above. Alternatively, R2 may lie in the range of 6 to
40 inches, and may
lie in the range of 5 to 15 inches in the case of rolling line contact. R2 may
be between 1 1/2 to 4
times as large as r2. In one embodiment R2 may be roughly twice as large as
r2, (+1- 20 %).
Figures 3a ¨ 3g
Figures 3a to 3g show and alternate bearing adapter 144 and pedestal seat 146
pair.
Bearing adapter 144 is substantially the same as bearing adapter 44, except
insofar as bearing
adapter 44 has a fully curved top surface 142, whereas bearing adapter 144 has
an upper surface
that has a flat central portion 148 between somewhat elevated side portions
150. The male
bearing surface portion 152 is located centrally on flat central portion 148,
and extends
upwardly therefrom. As with bearing adapter 44, bearing adapter 144 has first
and second radii
n and r2, formed in the longitudinal and transverse directions respectively,
such that the
upwardly protruding surface so formed is a toroidal surface. Pedestal seat 146
is substantially
similar to pedestal seat fitting 38. Pedestal seat 146 has a body having an
upper surface 154 that
seats in planar abutment against the downwardly facing surface of pedestal
roof 120, and
upwardly extending tangs 124 that engage lugs 122 as before.
While in the general sense, the female engagement fitting portion, namely the
hollow
depression 156 formed in the lower face of seat 146, is formed on longitudinal
and lateral radii
R1 and R2, as above, when these two radii are equal a spherical surface 158 is
formed, giving
the circular plan view of Figure 3a.
As the profiles of both the male and female surfaces are compound curves
(i.e., with
curvatures in both the x and y directions) Figures 3f and 3g, show a series of
profiles in each of
the longitudinal and transverse directions, at spaced intervals as indicated
in the top view
accompanying Figure 3f. These profiles are taken at the centreline, 20 %, 40
%, 60 %, 80 %,
and 100 % of the distance from the centreline to the edge of the curved
portion of the bearing
adapter or seat, as may be.
Figures 3h and 3i serve to illustrate that the male and female surfaces may be
inverted,
such that the female engagement surface 160 is formed on bearing adapter 162,
and the male
engagement surface 164 of seat 166. It is a matter of terminology which part
is actually the
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"seat", and which is the "rocker". Sometimes the seat may be assumed to be the
part that has
the larger radius, and which is usually thought of as being the stationary
reference, while the
rocker is taken to be the part with the smaller radius, that "rocks" on the
stationary seat.
However, this is not always so. At root, the relationship is of mating parts,
whether male or
female, and there is relative motion between the parts, or fittings, whether
the fittings are called
a "seat" or a "rocker". The fittings mate at a force transfer interface. The
force transfer interface
moves as the parts that co-operate to define the rocking interface rock on
each other, whichever
part may be, nominally, the male part or the female part. One of the mating
parts or surfaces, is
part of the bearing adapter, and another is part of the pedestal. There may be
only two mating
surfaces, or, as noted below in the context of the example of Figures 7a ¨ 7d,
there may be more
than two mating surfaces in the overall assembly defining the dynamic
interface between the
bearing adapter and the pedestal fitting, or pedestal seat, however it may be
called.
Figures 4a ¨ 4e
Figures 4a ¨ 4e show enlarged views of bearing adapter 44 and pedestal seat
fitting 38.
As can be seen, the compound curve, upwardly facing surface 142 runs fully to
terminate at the
end faces 134, and the side faces 170 of bearing adapter 44. The side faces
show the circularly
downwardly arched lower walls margins 172 of side faces 170 that seat about
bearings 46. In
all other respects, for the purposes of this description, bearing adapter 44
can be taken as being
the same as bearing adapter 144.
Figures 5a - 5c
Figures 5a ¨ 5c, show a conceptually similar bearing adapter and pedestal seat
combination to that of Figures 3a to 3g, but rather than having the interface
portions standing
proud of the remainder of the bearing adapter, the male portion 174 is sunken
into the top of the
bearing adapter, and the surrounding surface 176 is raised up. The mating
female portion 178
while retaining its hollowed out shape, stands proud of the surrounding
structure of the seat to
provide a corresponding mating surface. The longitudinally extending phantom
lines indicate
drain ports to discourage the collection of water.
Figures 6a - 6e
It may not be necessary for both female radii R1 and R2 to be on the same
fitting, or for
both male radii r1 and r2 to be on the same fitting. This is illustrated by
the saddle shaped
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-
fittings of Figures 6a to 6e. In these illustrations, a bearing adapter 180 is
of substantially the
same construction as bearing adapters 44 and 144, except insofar as bearing
adapter 180 has an
upper surface 192 that has a male fitting in the nature of a longitudinally
extending crown 182
with a laterally extending axis of rotation, for which the radius of curvature
is r1, and a female
fitting in the nature of a longitudinally extending trough 184 having a
lateral radius of curvature
R2. Similarly, pedestal fitting 186 mounted in roof 120 has a generally
downwardly facing
surface 194 that has a transversely extending trough 188 having a
longitudinally oriented radius
of curvature R1, for engagement with r1 of crown 182, and a longitudinally
running,
downwardly protruding crown 190 having a transverse radius of curvature r2 for
engagement
with R2 of trough 184. A progression of sectional profiles of these inter-
relating curvatures at
the 0%, 20%, 40%, 60%, 80% and 100% x and y locations is provided in Figures
6d and 6e. In
this embodiment, the smallest of R1 and R2 may again be equal to or larger
than the largest of r1
and r2.
As noted in the context of Figure 3a, in one sense the saddle shaped upper
surface 192
of bearing adapter 180 is both a seat and a rocker, being a seat in one
direction, and a rocker in
the other, as is the pedestal seat fitting. As noted above, the essence is
that there are two small
radii, and two large (or possibly even infinite) radii, and the surfaces form
a mating pair that
engage in rolling point contact in both the lateral and longitudinal
directions, with a central local
minimum potential energy position to which the assembly is biased to return.
It may also be noted, as shown in Figures 6h and 61, the saddle surfaces can
be inverted
such that whereas bearing adapter 180 has r1 and R2, bearing adapter 196 has
r2 and RI.
Similarly, whereas pedestal fitting 186 has r2 and R1, pedestal fitting 198
has r1 and R2- In
either case, the smallest of R1 and R2 may be larger than, or equal to, the
largest of r1 and r2,
and the mating opposed saddle surfaces, over the desired range of motion, may
tend to be
torsionally uncoupled as noted above in the context of bearing adapters 44 and
144.
Figures 7a ¨ 7d
It may be desired that the vertical forces transmitted from the pedestal roof
into the
bearing adapter be passed through line contact, rather than the bi-directional
rolling or rocking
point contact as in the assemblies of the embodiments of Figures 2a ¨ 2g, 3a ¨
3i, 4a ¨ 4e, 5a ¨
5c, and 6a ¨ 6g. In that case, it may be advantageous to employ an embodiment
of pedestal seat
to bearing adapter interface assembly having line contact rocker interfaces
such as represented
by the example shown in Figures 7a to 7d. In this instance a bearing adapter
200 has a
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hollowed out transverse cylindrical upper surface 202, acting as a female
engagement fitting
portion formed on radius R1. Surface 202 may be a round cylindrical section,
or it may be
parabolic, or other cylindrical section.
The corresponding pedestal seat fitting 204 may have a longitudinally
extending female
fitting, or trough, 206 having a cylindrical surface 208 formed on radius r1.
Again, fitting 204 is
cylindrical, and may be a round cylindrical section although, alternatively,
it could be parabolic,
elliptic, or some other shape for producing a rocking motion.
Trapped between bearing adapter 200 and pedestal seat fitting 204 is a rocker
member
210. Rocker member 210 has a first, or lower portion 212 having a protruding
male cylindrical
rocker surface 214 formed on a radius r1 for line contact engagement of
surface 202 of bearing
adapter 200 formed on radius R1, r1 being smaller than R1, and thus permitting
longitudinal
rocking to obtain passive self steering. As above, the resistance to rocking,
and hence to self
steering, may tend to be proportional to the weight on the rocker and hence
may give
proportional self steering when the car is either empty or loaded. Lower
portion 212 also has an
upper relief 216 that is preferably machined to a high level of flatness.
Lower portion 212 also
has a centrally located, integrally formed upwardly extending cylindrical stub
218 that stands
perpendicularly proud of surface 216. A bushing 220, which may be a press fit
bushing, mounts
on stub 218.
Rocker member 200 also has an upper portion 222 that has a second protruding
male
cylindrical rocker surface 224 formed on a radius r2 for line contact
engagement with the
cylindrical surface 208 of trough 206, formed on radius R2, thus permitting
lateral rocking of
sideframe 26. Upper portion 222 may have a lower relief 226 for placement in
opposition to
relief 216. Upper portion 222 has a centrally located blind bore 228 of a size
for tight fitting
engagement of bushing 220, such that a close tolerance, pivoting connection is
obtained that is
largely compliant to pivotal motion about the vertical, or z, axis of upper
portion 222 with
respect to lower portion 212. That is to say, the resistance to torsional
motion about the z-axis is
very small, and can be taken as zero for the purposes of analysis. To aid in
this, bearing 230
may be installed about stub 218 and bushing 220 and is placed between opposed
surfaces 206
and 216 to encourage relative rotational motion therebetween.
In this embodiment, stub 218 could be formed in upper portion 222, and bore
218
formed in lower portion 212, or, alternatively, bores 228 could be formed in
both upper portion
212 and lower portion 222, and a freely floating stub 218 and bushing 220
could be captured
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between them. It may be noted that the angular displacement about the z axis
of upper portions
222 relative to lower portion 212 may be quite small ¨ of the order of 1
degree of arc, and may
tend not to be even that large overly frequently.
Having described the rocking portions of the assembly of Figures 7a ¨ 7d,
there are a
number of additional features that may also be noted. First, bearing adapter
200 may have
longitudinally extending raised lateral abutment side walls 232 to discourage
lateral migration,
or escape of lower portion 212. Lower portion 212 may have non-galling,
relatively low co-
efficient of friction side wear shim stock members 234 trapped between the end
faces of lower
portion 212 and side walls 232. Bearing adapter 200 may also have a drain hole
formed therein,
possibly centrally, or placed at an angle. Similarly, pedestal seat fitting
204 may have laterally
extending depending end abutment walls 236 to discourage longitudinal
migration, or escape, of
upper portion 222. In a like manner to shim stock members 234, non-galling,
relatively low co-
efficient of friction end wear shim stock members 238 may be mounted between
the end faces
of upper portion 222 and end abutment walls 236.
In an alternative to the foregoing embodiment, the longitudinal cylindrical
trough could
be formed on the bearing adapter, and the lateral cylindrical trough could be
formed in the
pedestal seat, with corresponding changes in the entrapped rocker element.
Further, it is not
necessary that the male cylindrical portions be part of the entrapped rocker
element. Rather, one
of those male portions could be on the bearing adapter, and one of those male
portions could be
on the pedestal seat, with the corresponding female portions being formed on
the entrapped
rocker element. In the further alternative, the rocker element could include
one male element,
and one female element, having the male element formed on rit (or r2) being
located on the
bearing adapter, and the female element formed on R1 (or R2) being on the
underside of the
entrapped rocker element, and the male element formed on r2 (or r1) being
formed on the upper
surface of the entrapped rocker element, and the respective mating female
element formed on
radius R2 (or R1) being formed on the lower face of the pedestal seat. In the
still further
alternative, the rocker element could include one male element, and one female
element, having
the male element formed on r1 (or r2) being located on the pedestal seat, and
the female element
formed on R1 (or R2) being on the upper surface of the entrapped rocker
element, and the male
element formed on r2 (or r1) being formed on the lower surface of the
entrapped rocker element,
and the respective mating female element formed on radius R2 (or R1) being
formed on the
upper face of the bearing adapter. There are, in this regard, at least eight
possible combinations.
It is intended that the illustrations of Figures 7a ¨ 7d be understood to be
generically
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representative of all of these possible combinations, without requiring
further multiplication of
drawing views.
In this way the embodiment of Figures 7a ¨ 7d may tend to yield line contact
at the
force transfer interfaces, and yet rock in both the longitudinal and lateral
directions, with
compliance to torsion about the vertical axis. That is, the bearing adapter to
pedestal seat
interface assembly may tend to permit rotation about the longitudinal axis to
give lateral rocking
motion of the side frame; rotation about a transverse axis to give
longitudinal rocking motion;
and compliance to torsion about the vertical axis. It may tend to discourage
lateral translation,
and may tend to retain high stiffness in the vertical direction.
Figures 8a and 8b
The embodiment of Figures 8a and 8b is substantially similar to the embodiment
of
Figures 7a to 7d. However, rather than employing a pivot connection such as
the bore, stub,
bushing and bearing of Figures 7a ¨ 7d, a rocker element 244 is captured
between bearing
adapter 200 and pedestal seat 204. Rocker element 244 has a torsional
compliance element
made of a resilient material, identified as elastomeric member 246 bonded
between the opposed
faces of the upper 247 and lower 245 portions of rocker element 244.
Although Figures 8a and 8b show the laterally extending trough in bearing
adapter 200,
and the longitudinal trough in pedestal seat 204, it will be understood that
the same commentary
made concerning the possible alternate variations and combinations of the
features of the
example of Figures 7a to 7d also applies to the example of Figures 8a and 8b.
In general, while the torsional element may be between the two cylindrical
elements in a
manner tending torsionally to decouple them, it may be that the elastomeric
pad need not
necessarily be installed between the two cylindrical members. For example, the
rocker element
244 could be solid, and an elastomeric element could also be installed beneath
the top surface
of bearing adapter 200, or above the pedestal seat element, such that a
torsionally compliant
element is placed in series with the two rockers. This may tend to provide a
degree of angular
compliance in the connection.
The same general commentary may be made with regard to the pivotal connection
suggested above in connection with the example of Figures 7a to 7d. That is,
the top of the
bearing adapter could be pivotally mounted to the body of the bearing adapter
more generally,
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or the pedestal seat could be pivotally mounted to the pedestal roof, such
that, again, a
torsionally compliant element would be place in series with the two rockers.
However, as noted
above, the torsionally compliant element may be between the two rockers, such
that they may
tend to be torsionally de-coupled from each other.
In general, with regard to the embodiments of Figures 7a ¨ 7d, and 8a ¨ 8b,
provided
that the radii employed yield a physically appropriate combination tending
toward a local stable
minimum energy state, the male portion of the bearing adapter to pedestal seat
interface (with
the smaller radius of curvature) may be on either the bearing adapter or on
the pedestal seat, and
the mating female portion (with the larger radius of curvature) may be on the
other part,
whichever it may be. In that light, although a particular depiction may show a
male portion on a
bearing adapter, and a female fitting on the pedestal seat, these features
may, in general, be
reversed, without requiring a multiplicity of drawings to show all possible
permutations.
In general, provided that the radii employed yield a physically appropriate
combination
tending toward a local stable minimum energy state, the male portion of the
bearing adapter to
pedestal seat interface (with the smaller radius of curvature) may be on
either the bearing
adapter or on the pedestal seat, and the mating female portion (with the
larger radius of
curvature) may be on the other part, whichever it may be. In that light,
although a particular
depiction may show a male portion on a bearing adapter, and a female fitting
on the pedestal
seat, it is understood that these features can, in general, be reversed,
without requiring a
multiplicity of drawings to show all possible permutations.
Figures 9a to 9c
Figures 9a to 9c show the combination of a bearing adapter 250 with an
elastomeric
bearing adapter pad 252 and a rocker 254 and pedestal seat 256 to permit
lateral rocking of the
sideframe.
Bearing adapter 250 may be a commercially available part. Bearing adapter 250,
shown
in three additional views in Figures 10a ¨ 10c is substantially similar to
bearing adapter 44 (or
144) to the extent of its geometric features for engaging a bearing, but
differs therefrom in
having a more or less conventional upper surface. Upper surface 258 may be
flat, or may have a
large (roughly 60") radius crown 260, such as might have been used for
engaging a planar
pedestal seat surface. Crown 260 is split into two fore-and-aft portions, with
a laterally
extending central flat portion between them. Abreast of the central flat
portion, bearing adapter
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250 has a pair of laterally proud, outwardly facing lateral lands, 262 and
264, and, amidst those
lands, lateral lugs 266 that extend further still proud beyond lands 262 and
264.
Bearing adapter pad 252 may be a commercially available assembly such as may
be
manufactured by Lord Corporation of Erie Pennsylvania, or such as may be
identified as
Standard Car Truck Part Number SCT 5578. Bearing adapter pad 252 has a bearing
adapter
engagement member in the nature of a lower plate 268 whose bottom surface 270
is relieved to
seat over crown 260 in non-rocking engagement. Lateral and longitudinal
translation of bearing
adapter pad 252 is inhibited by an array of downwardly bent securement
locating lugs, or
fingers, or claws, in the nature of indexing members or tangs 272, two per
side in pairs located
to reach downwardly and bracket lugs 266 in close fitting engagement. The
bracketing
condition with respect to lugs 266 inhibits longitudinal motion between
bearing adapter pad 252
and bearing adapter 250. The laterally inside faces of tangs 272 closely
oppose the laterally
outwardly facing surfaces of lands 262 and 264, tending thereby to inhibit
lateral relative motion
of bearing adapter pad 252 relative to bearing adapter 250. Given that,
typically, 1/8 of the
weight of the rail road car body and lading may be passed through plate 268,
its vertical, lateral,
and longitudinal position relative to bearing adapter 250 can be taken as
fixed.
Bearing adapter pad 252 also has an upper plate, 274, that, in the case of a
retro-fit
installation of rocker 254 and seat 256, may have been used as a pedestal seat
engagement
member. In any case, upper plate 274 has the general shape of a longitudinally
extending
channel member, with a central, or back, portion, 276 and upwardly extending
left and right
hand leg portions 278, 280 adjoining the lateral margins of back portion 276.
Leg portions 278
may have a size and shape such as might have been suitable for mounting
directly to the
sideframe pedestal.
Between lower plate 268 and upper plate 274, bearing adapter pad 252 has a
bonded
resilient sandwich 280 that may include a first resilient layer, indicated as
lower elastomeric
layer 282 mounted directly to the upper surface of lower plate 268, an
intermediate stiffener
shear plate 284 bonded or molded to the upper surface of layer 282, and an
upper resilient layer,
indicated as upper elastomeric layer 286 bonded atop plate 284. The upper
surface of layer 286
may be bonded or molded to the lower surface of upper plate 274. Given that
the resilient layers
may be quite thin as compared to their length and breadth, the resultant
sandwich may tend to
have comparatively high vertical stiffness, comparatively high resistance to
torsion about the
longitudinal (x) and lateral (y) axes, comparatively low resistance to torsion
about the vertical
(z) axis (given the small angular displacements in any case), and non-trivial,
roughly equal
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resistance to shear in the x or y directions that may be in the range of
20,000 to 40,000 lbs per
inch, or more narrowly, about 30,000 lbs per inch for small deflections.
Bearing adapter pad
252 may tend to permit a measure of self steering to be obtained when the
elastomeric elements
are subjected to longitudinal shear forces.
Rocker 254 (seen in additional views lie, llf and 11g) has a body of
substantially
constant cross-section, having a lower surface 290 formed to sit in
substantially flat, non-
rocking engagement upon the upper surface of plate 274 of bearing adapter pad
252, and an
upper surface 292 formed to define a male rocker surface. Upper surface 292
may have a
continuously radius central portion 294 lying between adjacent tangential
portions 296 lying at a
constant slope angle. In one embodiment, the central portion may describe 4 ¨
6 degrees of arc
to either side of a central position, and may, in one embodiment have about 4-
V2 to 5 degrees. In
the terminology used above, this radius is "r2", the male radius of a lateral
rocker for permitting
lateral swinging motion of side frame 26. Where a bearing adapter with a crown
radius is
mounted under the resilient bearing adapter pad, the radius of rocker 254 is
less than the radius
of the crown, perhaps less than half the crown radius, and possibly being less
than 1/3 of the
crown radius. It may be formed on a radius of between 5 and 20 inches, or,
more narrowly, on a
radius of between 8 and 15 inches. Surface 292 could also be formed on a
parabolic profile, an
elliptic or hyperbolic profile, or some other profile to yield lateral
rocking.
Pedestal seat 256 (seen in Figures ha to 11d) has a body having a major
portion 300
that is substantially rectangular in plan view. When viewed from one end in
the longitudinal
direction, pedestal seat 256 has a generally channel shaped cross-section, in
which major portion
300 forms the back 302 and two longitudinally running legs 304, 306 extend
upwardly and
laterally outwardly from the lateral margins of major portion 300. Legs 304
and 306 have an
inner, or proximal portion 308 that extends upwardly and outwardly at an angle
from the lateral
margins of main portion 300, and an outer, or distal portion, or toe 310 that
extends from the
end of proximal portion 308 in a substantially vertical direction. The breadth
between the
opposed fingers of the channel section (i.e., between opposed toes 310)
corresponds to the width
of the sideframe pedestal roof 312, as shown in the cross-section of Figure
9b, with which legs
304 and 306 sit in close fitting, bracketing engagement. Legs 304 and 306 have
longitudinally
centrally located cut-outs, reliefs, rebates, or indexing features, identified
as notches 314.
Notches 314 seat in close fitting engagement about T-shaped lugs 316 (Figure
9b) that are
welded to the sideframe on either side of the pedestal roof. This engagement
establishes the
lateral and longitudinal position of pedestal seat 256 with respect to
sideframe 26.
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Pedestal seat 256 also has four laterally projecting comer lugs, or abutment
fittings 318,
whose longitudinally inwardly facing surfaces oppose the laterally extending
end-face surfaces
of the upturned legs 278 of upper plate 274 of bearing adapter pad 252. That
is, the corner
abutment fittings 318 on either lateral side of pedestal seat 256 bracket the
ends of the upturned
legs 278 of adapter pad 252 in close fitting engagement. This relationship
fixes the longitudinal
position of pedestal seat 256 relative to the upper plate of bearing adapter
pad 252.
Major portion 300 of pedestal seat 256 has a downwardly facing surface 300
that is
hollowed out to form a depression defining a female rocking engagement surface
302. This
surface is formed on a female radius (identified as R2 in concordance with
terminology used
herein above) that is quite substantially larger than the radius of central
portion 294 (Figure 110
of rocker 254, such that rocker 254 and pedestal seat 256 meet in rolling line
contact
engagement and permit sideframe 26 to swing laterally in a lateral rocking
relationship on
rocker 254. The arcuate profile of female rocking engagement surface 302 may
be such as to
encourage lateral self centering of rocker 254, and may have a radius of
curvature that varies
from a central region to adjacent regions, which may be tangential planar
regions. Where
pedestal seat 256 and rocker 254 are provided by way of retro-fit installation
above an adapter
having a crown radius, the radius of curvature of the pedestal seat may tend
to be less than or
equal to the crown radius. The central radius of curvature R2 of surface 302,
or the radius of
curvature generally if constant, may be in the range of 6 to 60 inches, is
preferably greater than
10 inches and less than 40 inches. It may be between 1 1 /1 0 to 4 times as
large as the rocker
radius of curvature r2. As noted elsewhere, the pedestal seat need not have
the female rocker
surface, and the rocker need not have the male rocker surface, but rather,
these surfaces could be
reversed, so that the male surface is on the pedestal seat, and the female
surface is on the rocker.
Particularly in the context of a retro-fit installation, there may be
relatively little clearance
between the upturned legs 278 of upper plate 274 and legs 304, 306 of pedestal
seat 256. This
distance is shown in Figure 9b as gap 'G', which is preferably sufficient
allowance for rocking
motion between the parts that rocking motion is bounded by the spacing of the
truck bolster gibs
106, 108.
By providing the combination of a lateral rocker and a shear pad, the
resultant assembly
may provide an anisotropic response at the bearing adapter to pedestal seat
assembly interface,
with a generally increased softness in the lateral direction, while permitting
a measure of self
steering. The example of Figure 9a may be provided as an original
installation, or may be
provided as a retrofit installation. In the case of a retrofit installation,
rocker 254 and pedestal
seat 256 may be installed between an existing elastomeric pad and an existing
pedestal seat, or
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may be installed in addition to a replacement elastomeric pad of lesser
through- thickness, such
that the overall height of the bearing adapter to pedestal seat interface may
remain roughly the
same as it was before the retrofit.
Figures 9e and 9f represent alternate embodiments of combinations of
elastomeric pads
and rockers. While the embodiment of Figure 9a showed an elastomeric sandwich
that had
roughly equivalent response to shear in the lateral and longitudinal
directions, this need not be
the general case. For example, in the embodiments of Figures 9e and 9f,
elastomeric bearing
adapter pad assemblies 320 and 331 have respective resilient elastomeric
laminates sandwiches,
indicated generally as 322 and 323 in which the stiffeners 326, 327 have
longitudinally
extending corrugations, or waves. In the longitudinal direction, the sandwich
may tend to react
in nearly pure shear, as before in the example of Figure 9a. However,
deflection in the lateral
direction now requires not only a shear component, but also a component normal
to the
elastomeric elements, in compressive or tensile stress, rather than, and in
addition to, shear.
This may tend to give a stiffer lateral response, and hence an anisotropic
response. An
anisotropic shear pad arrangement of this nature might have been used in the
embodiment of
Figure 9a, and a planar arrangement, as in the embodiment of Figure 9a could
be used in either
of the embodiments of Figures 9e, and 9f. Considering Figure 9e, both base
plate 328 and upper
plate 330 has a wavy contour corresponding to the wavy contour of sandwich 322
generally.
Rocker 332 has a lower surface of corresponding profile. Otherwise, this
embodiment is
substantially the same as the embodiment of Figure 9a.
Considering Figure 9f, an elastomeric bearing adapter pad assembly 321 has a
base plate
334 having a lower surface for seating in non-rocking relationship on a
bearing adapter, in the
same manner as bearing adapter pad assembly 252 sits upon bearing adapter 250.
The upper
surface 335 of base plate 334 has a corrugated or wavy contour, the
corrugations running
lengthwise, as discussed above. An elastomeric laminate of a first resilient
layer 336, an
internal stiffener plate 337, and a second resilient layer 338 are located
between base plate 334
and a correspondingly wavy undersurface of upper plate 340. Rather than being
a flat plate
upon which a further rocker plate is mounted, upper plate 340 has an upper
surface 342 having
an integrally formed rocker contour corresponding to that of the upper surface
of rocker 254.
Pedestal seat 344 then mounts directly to, and in lateral rocking relationship
with upper plate
340, without need for a separate rocker part. The combination of bearing
adapter pad 321 and
pedestal seat 342 may have interconnecting abutments 347 to prevent
longitudinal migration of
rocker surface 342 relative to the contoured downwardly facing surface 348 of
pedestal seat
344.
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Figures 12a
Figure 12a shows an alternate embodiment of wheelset to sideframe interface
assembly,
indicated most generally as 350. In this example it may be understood that the
pedestal region
of sideframe 351, as shown in Figure 12a, is substantially similar to those
shown in the
previous examples, and may be taken as being the same except insofar as may be
noted.
Similarly, bearing 352 may be taken as representing the location of the end of
a wheelset more
generally, with the wheelset to sideframe interface assembly including those
items, members or
elements that are mounted between bearing 352 and sideframe 351. Bearing
adapter 354 may
be generally similar to bearing adapter 44 or 144 in terms of its lower
structure for seating on
bearing 352. As with the bodies of the other bearing adapters described
herein, the body of
bearing adapter 354 may be a casting or a forging, or a machined part, and may
be made of a
material that may be a relatively low cost material, such as cast iron or
steel, and may be made
in generally the same manner as bearing adapters have been made heretofore.
Bearing adapter
354 may have a bi-directional rocker 353 employing a compound curvature of
first and second
radii of curvature according to one or another of the possible combinations of
male and female
radii of curvature discussed above. Bearing adapter 354 may differ from those
described above
in that the central body portion 355 of the adapter has been trimmed to be
shorter longitudinally,
and the inside spacing between the corner abutment portions has been widened
somewhat, to
accommodate the installation of an auxiliary centering device, or centering
member, or centrally
biased restoring member in the nature of, for example, elastomeric bumper
pads, such as those
identified as resilient pads, 356. Pads 356 may be considered a form of
restorative centering
element, and may also be termed "snubbers". A pedestal seat fitting having a
mating rocking
surface for permitting lateral and longitudinal rocking, is identified as 358.
As with the other
pedestal seat fittings shown and described herein, fitting 358 may be made of
a hard metal
material, which made be a grade of steel. The mating engagement of the rocking
surfaces may,
again, tend to be torsionally compliant as noted above.
Figure 12b
In Figure 12b, a bearing adapter 360 is substantially similar to bearing
adapter 354, but
differs in having a central recess, or socket, or accommodation, indicated
generally as 361 for
receiving an insert identified as a first, or lower, rocker member 362. As
with bearing adapter
354, the main, or central portion of the body 359 of bearing adapter 360 may
be of shorter
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longitudinal extent than might otherwise be the case, being truncated or
relieved to
accommodate resilient members 356.
Accommodation 361 may have a plan view form whose periphery may include one or
more keying, or indexing, features or fittings, of which cusps 363 may be
representative. Cusps
363 may receive mating keying, or indexing, features or fittings, of which
lobes 364 may be
taken as representative examples. Cusps 363 and lobes 364 may be such as may
fix the angular
orientation of the lower, or first, rocker member 362 such that the
appropriate radii of curvature
may be presented in each of the lateral and longitudinal directions. For
example cusps 363 may
be spaced unequally about the periphery of accommodation 361 (with lobes 364
being
correspondingly spaced about the periphery of the insert member 362) in a
specific spacing
arrangement to prevent installation in an incorrect orientation, (such as 90
degrees out of phase).
For example, one cusp may be spaced 80 degrees of arc about the periphery from
one
neighbouring cusp, and 100 degrees of arc from another neighbouring cusp, and
so on to form a
rectangular pattern. Many variations are possible.
While body 359 of bearing adapter 360 may be made of cast iron or steel, the
insert,
namely first rocker member 362, may be made of a different material. That
different material
may present a hardened metal rocker surface such as may have been manufactured
by a
different process. For example, the insert, member 362, may be made of a tool
steel, or of a
steel such as may be used in the manufacture of ball bearings. Furthermore,
upper surface 365
of insert member 362, which includes that portion that is in rocking
engagement with the mating
pedestal seat 368, may be machined or otherwise formed to a high degree of
smoothness, akin to
a ball bearing surface, and may be heat treated, to give a finished bearing
part.
Similarly, pedestal seat 368 may be made of a hardened material, such as a
tool steel or
a steel from which bearings are made, formed to a high level of smoothness,
and heat treated as
may be appropriate, having a surface formed to mate with surface 365 of rocker
member 362.
Alternatively, pedestal seat 368 may have an accommodation 367 and indicated
as an upper or
second rocker member 366 analogous to insert 362 and accommodation 361, with
keying or
indexing such as may tend to cause the parts to seat in the correct
orientation. Insert member
366 may be formed of a hard material in a manner similar to insert member 362.
and has a
downward facing rocking surface 357, which may be machined or otherwise formed
to a high
degree of smoothness, akin to a ball or roller bearing surface, and may be
heat treated, to give a
finished bearing part surface for mating, rocking engagement with surface 365.
Where rocker
member 362 has both male radii, and the female radii of curvature are both
infinite, such that the
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female surface is planar, a wear member having a planar surface such as spring
clip 369 may be
mounted in a sprung interference fit in the pedestal roof in lieu of pedestal
seat 368. In one
embodiment, spring clip 369 may be a clip on "Dyna-Clip" (t.m.) pedestal roof
wear plate such
as made by TransDyne Inc. Such a clip 369 is shown an isometric view in Figure
12f. Clip 369
is shown, as installed, in a quartered section isometric view in Figure 12g in
a position for
rocking engagement with a bearing adapter 349. While bearing adapter 349 does
not show an
insert, a bearing adapter such as bearing adapter 360 with an insert 364 may
be employed.
Figure 12e
Figure 12e shows an alternate embodiment of wheelset to sideframe interface
assembly,
indicated most generally as 370. Assembly 370 may include such elements as a
bearing adapter
371, a pair of resilient members 356, a rocking assembly that may include a
boot, resilient ring
or retainer, 372, a first rocker member 373, and a second rocker member 374. A
pedestal seat
may be provided to mount in the roof of the pedestal as described above, or
second rocker
member 374 may mount directly in the pedestal roof.
Bearing adapter 371 is generally similar to bearing adapter 44, 144 or 354 in
terms of its
lower structure for seating on bearing 352. The body of bearing adapter 371
may be a casting or
a forging, or a machined part, and may be made of a material that may be a
relatively low cost
material, such as cast iron or steel. Bearing adapter 371 may be provided with
a central recess,
or socket, or accommodation, indicated generally as 376, for receiving rocker
member 372 and
rocker member 373, and resilient ring 372. The ends of the main portion of the
body of bearing
adapter 371 may be of relatively short extent to accommodate resilient members
356.
Accommodation 376 may have the form of a circular opening, that may have a
radially
inwardly extending flange 377, whose upwardly facing surface 378 defines a
circumferential
land upon which to seat first rocker member 372. Flange 377 may also include
drain holes 378,
such as may be 4 holes formed on 90 degree centers, for example. Rocker member
372 has a
spherical engagement surface.
First rocker member 372 may include a thickened central portion, and a thinner
radially
distant peripheral portion, having a lower radial edge, or margin, or land,
for seating upon, and
for transferring vertical loads into, flange 377. In an alternate embodiment a
non-galling,
relatively soft annular gasket, or shim, whether made of a suitable brass,
bronze, copper, or
other material may be employed on flange 377 under the land. First rocker
member 372 may be
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made of a different material from the material from which the body of bearing
adapter 356 is
made more generally. That is to say, rocker member 372 may be made of a hard,
or hardened
material, such as a tool steel or a steel such as might be used in a bearing,
that may be finished
to a generally higher level of precision, and to a finer degree of surface
roughness than the body
of bearing adapter 356 more generally. Such a material may be suitable for
rolling contact
operation under high contact pressures.
Second rocker member 373 may be a disc of circular shape (when viewed in plan
view)
or other suitable shape for seating in pedestal seat 375, or, in the event
that a pedestal seat
member is not used, then formed directly to mate with the pedestal roof. First
rocker member
373 may have an upper, or rocker surface 374, having a profile such as may
give bi-directional
lateral and longitudinal rocking motion when used in conjunction with the
mating second, or
upper rocker member, 373. Second rocker member 373 may be made of a different
material
from the material from which the body of bearing adapter 371, or the pedestal
seat, is made
more generally. Second rocker member 373 may be made of a hard, or hardened
material, such
as a tool steel or a steel such as might be used in a bearing, that may be
finished to a generally
higher level of precision, and to a finer degree of surface roughness than the
body of bearing
adapter 371 more generally. Such a material may be suitable for rolling
contact operation under
high contact pressures, particularly as when operated in conjunction with
first rocker member
372. It may be noted that where an insert of dissimilar material is used, that
material may tend
to be rather more costly than the cast iron or relatively mild steel from
which bearing adapters
may otherwise tend to be made. Further still, an insert of this nature may
possibly be removed
and replaced, either on the basis of a scheduled rotation, or as the need may
arise.
Resilient member 372 may be made of a composite or polymeric material, such as
a
polyurethane. Resilient member 372 may also have apertures, or reliefs 373
such as may be
placed in a position for co-operation with corresponding to drain holes 378.
The wall height of
resilient member 372 may be such as to engage the periphery of sufficiently
tall that first rocker
member 372. Further, a portion of the radially outwardly facing peripheral
edge of the second,
upper, rocking member 374, may also lie within, or may be partially overlapped
by, and may
possibly slightly stretchingly engage, the upper margin of resilient member
372 in a close, or
interference, fit manner, such that a seal may tend to be formed to exclude
dirt or moisture. In
this way the assembly may tend to form a closed unit. In that regard, such
space as may be
formed between the first and second rockers 373, 374 may be packed with a
lubricant, such as a
lithium or other suitable grease.
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It may be desirable for the rocking assembly at the wheelset to sideframe
interface to
tend to maintain itself in a centered condition. As noted, the torsionally de-
coupled bi-
directional rocker arrangements disclosed herein may tend to have rocking
stiffnesses that are
proportional to the weight placed upon the rocker. When the rocker is
unloaded, in whole or in
part, it may be desirable for the rocker to be urged to a self centered
position without regard to
the actual weight on the rocker surfaces. The interface assembly may include
resilient members
356 that may seat between the longitudinal ends of bearing adapter 371 (and
pedestal seat 352)
and the pedestal jaw thrust blocks 380.
Figures 12c and 12d are provided to illustrate the spatial relationship of the
sandwich
formed by (a) the bearing adapter, such as, for example, bearing adapter 354;
(b) the centering
member, such as, for example, resilient members 356; and (c) the pedestal jaw
thrust blocks,
380. Ancillary details such as, for example, drain holes or phantom lines to
show hidden
features have been omitted from Figures 12c and 12d for clarity.
Figures 13a ¨ 13e
As shown in Figures 13a ¨ 13e, resilient members 356 may have the general
shape of a
channel, having a central, or back, or tranverse, or web portion 381, and a
pair of left and right
hand, flanking wing portions 382, 383. Wing portions 382 and 383 may tend to
have
downwardly and outwardly tending extremeties that may tend to have an arcuate
lower edge
such as may seat over the bearing casing. The inside width of wing portions
382 and 383 may
be such as to seat snugly about the sides of thrust blocks 380. A transversely
extending lobate
portion 385, running along the upper margin of web portion 381, may seat in a
radiused rebate
384 between the upper margin of thrust blocks 380 and the end of pedestal seat
354. The inner
lateral edge 386 of lobate portion 385 may tend to be chamfered, or relieved,
to accommodate,
and to seat next to, the end of pedestal seat 354.
Where a longitudinal rocking surface is used, and the truck is experiencing
reduced
wheel load, (such as may approach wheel lift), or where the car is operating
in the light car
condition, it may be helpful to employ an auxiliary restorative centering
element that may
include a biasing element tending to move the bearing adapter to a
longitudinally centered
position relative to the pedestal roof, and whose restorative tendency may be
independent of
the gravitational force experienced at the wheel. That is, when the bearing
adapter is under
less than full load, or is unloaded, it may be desirable to maintain a bias to
a central position.
Resilient members 356 described above may operate to urge such centering.
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When resilient member 356 is in place, bearing adapter 354 may tend to be
located
relative to jaws 380. As installed, the snubber (member 356) may seat about
the pedestal
jaw thrust lug in a slight interference fit, and may seat next to the bearing
adapter end wall
and between the bearing adapter corner abutments in a slight interference fit.
The snubber
may be sandwiched between, and may establish the spaced relative position of,
the thrust lug
and the bearing adapter and may provide an initial central positioning of the
mating rocker
elements as well as providing a restorative bias. Although bearing adapter 354
may still rock
relative to the sideframe, such rocking may tend to deform (typically, locally
compress) a
portion of member 356, and, being elastic, member 354 may tend to urge bearing
adapter 354
back to a central position, whether there is much weight on the rocking
elements or not.
Resilient member 354 may have a restorative force-deflection characteristic in
the longitudinal
direction that is substantially less stiff than the force deflection
characteristic of the fully loaded
longitudinal rocker (perhaps one to two orders of magnitude less), such that,
in a fully loaded
car condition, member 354 may tend not significantly to alter the rocking
behaviour. In one
embodiment member 354 may be made of a polyurethane having a Young's modulus
of some
6,500 p.s.i. In another embodiment the Young's modulus may be about 13,000
p.s.i. The
placement of resilient members 356 may tend to center the rocking elements
during installation.
In one embodiment, the force to deflect one of the snubbers may be less than
20 % of the
force to deflect the rocker a corresponding amount under the light car (i.e.,
unloaded)
condition, and may, for small deflections, have an equivalent force/deflection
curve slope
that may be less than 10 % of the force deflection characteristic of the
longitudinal rocker.
Figures 14a to 14e
Figures 14a to 14e relate to a three piece truck 400. Truck 400 has three
major
elements, those elements being a truck bolster 402, that is symmetrical about
the truck
longitudinal centreline, and a pair of first and second side frames, indicated
as 404. Only one
side frame is shown in Figure 14c given the symmetry of truck 400. Three piece
truck 400
has a resilient suspension (a primary suspension) provided by a spring groups
405 trapped
between each of the distal (i.e., transversely outboard) ends of truck bolster
402 and side
frames 404.
Truck bolster 402 is a rigid, fabricated beam having a first end for engaging
one side
frame assembly and a second end for engaging the other side frame assembly
(both ends
being indicated as 406). A center plate or center bowl 408 is located at the
truck center. An
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=
upper flange 410 extends between the two ends 404, being narrow at a central
waist and
flaring to a wider transversely outboard termination at ends 404. Truck
bolster 402 also has a
lower flange 412 and two fabricated webs 414 extending between upper flange
410 and
lower flange 412 to form an irregular, closed section box beam. Additional
webs 415 are
mounted between the distal portions of flanges 410 and 412 where bolster 402
engages one
of the spring groups 405. The transversely distal region of truck bolster 402
also has friction
damper seats 416, 418 for accommodating friction damper wedges.
Side frame 404 may be a casting having pedestal fittings 419 into which
bearing
adapters 420, bearings 421, and a pair of axles 422 mount. Each of axles 422
has a pair of
first and second wheels 423, 425 mounted to it in a spaced apart position
corresponding to
the width of the track gauge of the track upon which the rail car is to
operate. Side frame 404
also has a compression member, or upper beam member 424, a tension member, or
lower
beam member 426, and vertical side columns 428 and 430, each lying to one side
of a
vertical transverse plane bisecting truck 400 at the longitudinal station of
the truck center. A
generally rectangular opening is defined by the co-operation of the upper and
lower beam
members 424, 426 and vertical columns 428, 430, into which the distal end of
truck bolster
402 can be introduced. The distal end of truck bolster 402 can then move up
and down
relative to the side frame within this opening. Lower beam member 426 has a
bottom or
lower spring seat 432 upon which spring group 405 can seat. Similarly, an
upper spring seat
434 is provided by the underside of the distal portion of bolster 402 engages
the upper end of
spring group 405. As such, vertical movement of truck bolster 402 will tend to
increase or
decrease the compression of the springs in spring group 405.
In the embodiment of Figure 14a, spring group 405 has two rows of springs 436,
a
transversely inboard row and a transversely outboard row. In one embodiment
each row may
have four large (8 inch +/-) diameter coil springs giving vertical bounce
spring rate constant,
k, for group 405 of less than 10,000 lbs. / inch. In one embodiment this
spring rate constant
may be in the range of 6000 to 10,000 lbs. / in., and may be in the range of
7000 to 9500 lbs.
/ in, giving an overall vertical bounce spring rate for the truck of double
these values, perhaps
in the range of 14,000 to 18,500 lbs. / in for the truck. The spring array may
include nested
coils of outer springs, inner springs, and inner-inner springs depending on
the overall spring
rate desired for the group, and the apportionment of that stiffness. The
number of springs,
the number of inner and outer coils, and the spring rate of the various
springs can be varied.
The spring rates of the coils of the spring group add to give the spring rate
constant of the
group, typically being suited for the loading for which the truck is designed.
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Each side frame assembly also has four friction damper wedges arranged in
first and
second pairs of transversely inboard and transversely outboard wedges 440,
441,442 and 443
that engage the sockets, or seats 416, 418 in a four-cornered arrangement. The
corner springs
in spring group 405 bear upon a friction damper wedge 440, 441, 442 or 443.
Each of
vertical columns 428, 430 has a friction wear plate 450 having transversely
inboard and
transversely outboard regions against which the friction faces of wedges 440,
441, 442 and
443 can bear, respectively. Bolster gibs 451 and 453 lie inboard and outboard
of wear plate
450 respectively. Gibs 451 and 453 act to limit the lateral travel of bolster
402 relative to
side frame 404. The deadweight compression of the springs under the dampers
will tend to
yield a reaction force working on the bottom face of the wedge, trying to
drive the wedge
upward along the inclined face of the seat in the bolster, thus urging, or
biasing, the friction
face against the opposing portion of the friction face of the side frame
column. In one
embodiment, the springs chosen may have an undeflected length of 15 inches,
and a dead
weight deflection of about 3 inches.
As seen in the top view of Figure 14c, and in the schematic sketch of Figure
lk the
side-by-side friction dampers have a relatively wide averaged moment arm L to
resist
angular deflection of the side frame relative to the truck bolster in the
parallelogram mode.
This moment arm is significantly greater than the effective moment arm of a
single wedge
located on the spring group (and side frame) centre line. Further, the use of
independent
springs under each of the wedges means that whichever wedge is jammed in
tightly, there is
always a dedicated spring under that specific wedge to resist the deflection.
In contrast to
older designs, the overall damping face width is greater because it is sized
to be driven by
relatively larger diameter (e.g., 8 in +0 springs, as compared to the smaller
diameter of, for
example, AAR B 432 out or B 331 side springs, or smaller. Further, in having
two elements
side-by-side the effective width of the damper is doubled, and the effective
moment arm over
which the diagonally opposite dampers work to resist parallelogram deformation
of the truck
in hunting and curving greater than it would have been for a single damper.
In the illustration of Figure 14e, the damper seats are shown as being
segregated by a
partition 452. If a longitudinal vertical plane is drawn through truck 400
through the center
of partition 452, it can be seen that the inboard dampers lie to one side of
plane 454, and the
outboard dampers lie to the outboard side of the plane. In hunting then, the
normal force
from the damper working against the hunting will tend to act in a couple in
which the force
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on the friction bearing surface of the inboard pad will always be fully
inboard of the plane on
one end, and fully outboard on the other diagonal friction face.
In one embodiment, the size of the spring group embodiment of Figure 14b may
yield
a side frame window opening having a width between the vertical columns of
side frame 404
of roughly 33 inches. This is relatively large compared to existing spring
groups, being more
than 25 % greater in width. Truck 400 may have a correspondingly greater
wheelbase
length, indicated as WB. WB may be greater than 73 inches, or, taken as a
ratio to the track
gauge width, may be greater than 1.30 time the track gauge width. It may be
greater than 80
inches, or more than 1.4 times the gauge width, and in one embodiment is
greater than 1.5
times the track gauge width, being as great, or greater than, about 84 inches.
Similarly, the
side frame window may be wider than tall. The measurement across the wear
plate faces of
the side frame columns may be greater than 24", possibly in the ratio of
greater than 8:7 of
width to height, and possibly in the range of 28" or 32" or more, giving
ratios of greater than
4:3 and greater than 3:2. The spring seat may have lengthened dimensions to
correspond to
the width of the side frame window, and a transverse width of 15 V2 - 17" or
more.
Figures 15a, 15b and 15c
In Figures 15a, 15b and 15c, there is an alternate embodiment of three piece
truck,
identified as 460. Truck 460 employs constant force inboard and outboard, fore
and aft pairs
of friction dampers 466 mounted in the distal ends of truck bolster 468. In
this arrangement,
springs 470 are mounted horizontally in pockets in the distal ends of truck
bolster 468 and
urge, or bias, each of the friction dampers 466 against the corresponding
friction surfaces of
the vertical columns of the side frames. The spring force on friction damper
wedges 440,
441, 442 and 443 varies as a function of the vertical displacement of truck
bolster 402, since
they are driven by the vertical springs of spring group 405. By contrast, the
deflection of
springs 470 does not depend on vertical compression of the main spring group
472, but rather
is a function of an initial pre-load.
Figures 16a and 16b
Figures 16a and 16b show a partial isometric view of a truck bolster 480 that
is
generally similar to truck bolster 402 of Figure 14a, except insofar as
bolster pocket 482 does
not have a central partition like web 452, but rather has a continuous bay
extending across
the width of the underlying spring group, such as spring group 436. A single
wide damper
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wedge is indicated as 484. Damper 484 is of a width to be supported by, and to
be acted
upon, by two springs 486, 488 of the underlying spring group. In the event
that bolster 400
may tend to deflect to a non-perpendicular orientation relative to the
associated side frame, as
in the parallelogramming phenomenon, one side of wedge 484 may tend to be
squeezed more
tightly than the other, giving wedge 484 a tendency to twist in the pocket
about an axis of
rotation perpendicular to the angled face (i.e., the hypotenuse face) of the
wedge. This
twisting tendency may also tend to cause differential compression in springs
486, 488,
yielding a restoring moment both to the twisting of wedge 484 and to the non-
square
displacement of truck bolster 480 relative to the truck side frame. As there
may tend to be a
similar moment generated at the opposite spring pair at the opposite side
column of the side
frame, this may tend to enhance the self-squaring tendency of the truck more
generally.
Also included in Figure 16b is an alternate pair of damper wedges 490, 492.
This
dual wedge configuration can similarly seat in bolster pocket 482, and, in
this case, each
wedge 490, 492 sits over a separate spring. Wedges 490, 492 are vertically
slidable relative
to each other along the primary angle of the face of bolster pocket 482. When
the truck
moves to an out of square condition, differential displacement of wedges 490,
492 may tend
to result in differential compression of their associated springs, e.g., 484,
488 resulting in a
restoring moment as above.
The sliding motion described above may tend to cause wear on the moving
surfaces,
namely (a) the side frame columns, and (b) the angled surfaces of the bolster
pockets. To
alleviate, or ameliorate, this situation, consumable wear plates 494 can be
mounted in bolster
pocket 482 (with appropriate dimensional adjustments) as in Figure 16a. Wear
plates 494
can be smooth steel plates, possibly of a hardened, wear resistant alloy, or
may be made from
a non-metallic, or partially non-metallic, relatively low friction wear
resistant surface. Other
plates for engaging the friction surfaces of the dampers may be mounted to the
side frame
columns, and indicated by item 496 in Figure 15d.
For the purposes of the example of Figure 14a, it has been assumed that the
spring
group is two coils wide, and that the pocket is, correspondingly, also two
coils wide. The
spring group could be more than two coils wide. The bolster pocket is assumed
to have the
same width as the spring group, but could be less wide. In the embodiments of
Figures la,
if, 14a, and 16a, for example, the dampers are in four cornered arrangements
that are
symmetrical both about the center axis of the truck bolster and about a
longitudinal vertical
plane of the side frame.
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Thus far only primary wedge angles have been discussed. Figure 17a shows an
isometric view of an end portion of a truck bolster 510, generally similar to
bolster 402. As
with all of the truck bolsters shown and discussed herein, bolster 510 is
symmetrical about
the central longitudinal vertical plane of the bolster (i.e., cross-wise
relative to the truck
generally) and symmetrical about the vertical mid-span section of the bolster
(i.e., the
longitudinal plane of symmetry of the truck generally, coinciding with the
rail car
longitudinal center line). Bolster 510 has a pair of spaced apart bolster
pockets 512, 514 for
receiving damper wedges 516, 518. Pocket 512 is laterally inboard of pocket
514 relative to
the side frame of the truck more generally. Wear plate inserts 520, 522 are
mounted in
pockets 512, 514 along the angled wedge face.
As can be seen, wedges 516, 518 have a primary angle, a as measured between
vertical sliding face 524, (or 526, as may be) and the angled vertex 528 of
outboard face 530.
For the embodiments discussed herein, primary angle a may tend to lie in the
range of 35 ¨
55 degrees, possibly about 40 - 50 degrees. This same angle a is matched by
the facing
surface of the bolster pocket, be it 512 or 514.
A secondary angle p gives the inboard, (or outboard), rake of the sloped
surface of
wedge 516 (or 518). The true rake angle can be seen by sighting along plane of
the sloped
face and measuring the angle between the sloped face and the planar outboard
face 530. The
rake angle is the complement of the angle so measured. The rake angle may tend
to be
greater than 5 degrees, may lie in the range of 5 to 20 degrees, and is
preferably about 10 to
15 degrees. A modest rake angle may be desirable.
When the truck suspension works in response to track perturbations, the damper
wedges may tend to work in their pockets. The rake angles yield a component of
force
tending to bias the outboard face 530 of outboard wedge 518 outboard against
the opposing
outboard face of bolster pocket 514. Similarly, the inboard face of wedge 516
may tend to be
biased toward the inboard planar face of inboard bolster pocket 512. These
inboard and
outboard faces of the bolster pockets may be lined with a low friction surface
pad, indicated
generally as 532. The left hand and right hand biases of the wedges may tend
to keep them
apart to yield the full moment arm distance intended, and, by keeping them
against the planar
facing walls, may tend to discourage twisting of the dampers in the respective
pockets.
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Bolster 510 includes a middle land 534 between pockets 512, 514, against which
another spring 536 may work. Middle land 534 is such as might be found in a
spring group
that is three (or more) coils wide. However, whether two, three, or more coils
wide, and
whether employing a central land or no central land, bolster pockets can have
both primary
and secondary angles as illustrated in the example embodiment of Figure 18c,
with or
without wear inserts.
Where a central land, e.g., land 534, separates two damper pockets, the
opposing side
frame column wear plates need not be monolithic. That is, two wear plate
regions could be
provided, one opposite each of the inboard and outboard dampers, presenting
planar surfaces
against which the dampers can bear. The normal vectors of those regions may be
parallel,
the surfaces may be co-planar and perpendicular to the long axis of the side
frame, and may
present a clear, un-interrupted surface to the friction faces of the dampers.
Figure 17b shows a bolster 540 that is similar to bolster 510 except insofar
as bolster
pockets 542, 544 each accommodate a pair of split wedges 546, 548. Pockets
542, 544 each
have a pair of bearing surfaces 550, 552 that are inclined at both a primary
angle a and a
secondary angle p, the secondary angles of surfaces 550 and 552 being of
opposite hand to
yield the damper separating forces discussed above. Surfaces 550 and 552 are
also provided
with linings in the nature of relatively low friction wear plates 554, 556.
Each of pockets 542
and 544 accommodates a pair of split wedges 558, 560. Each pair of split
wedges seats over
a single spring 562. Another spring 564 bears against central land 566.
The example of Figure 18a shows a combination of a bolster 570 and biased
split
wedges 572, 574. Bolster 570 is the same as bolster 540 except insofar as
bolster pockets
576, 578 are stepped pockets in which the steps, e.g., items 580, 582, have
the same primary
angle a, and the same secondary angle 13, and are both biased in the same
direction, unlike
the symmetrical faces of the split wedges in Figure 8d, which are left and
right handed. Thus
the outboard pair of split wedges 584 has a first member 586 and a second
member 588 each
having primary angle a and secondary angle p, and are of the same hand such
that in use both
the first and second members will tend to be biased in the outboard direction
(i.e. toward the
distal end of bolster 570). Similarly, the inboard pair of split wedges has a
first member 592
and a second member 594 each having primary angle a, and secondary angle p,
except that
the sense of secondary angle it is in the opposite direction such that members
592 and 594
will both tend in use to be driven in the inboard direction (i.e., toward the
truck center).
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As shown in the partial sectional view of Figure 18c, a replaceable monolithic
stepped wear insert 596 is welded in the bolster pocket 580 (or 582 if
opposite hand, as the
case may be). Insert 596 has the same primary and secondary angles a and p as
the split
wedges it is to accommodate, namely 586, 588 (or, opposite hand, 592, 594).
When
installed, and working, the more outboard of the wedges, 588 (or, opposite
hand, the more
inboard of the wedges 592) has a vertical and longitudinally planar outboard
face 600 that
bears against a similarly planar outboard face 602 (or, opposite hand, inboard
face 604)
These faces are preferably prepared in a manner that yields a relatively low
friction sliding
interface between them. In that regard, a low friction pad may be mounted to
either surface,
preferably the outboard surface of pocket 580. The sloped face 606 of member
588 bears
against the opposing outboard land 610 of insert 596. The overall width of
outboard member
588 is greater than that of outboard land 610, such that the inboard planar
face of member
588 acts as an abutment face to fend inboard member 586 off of the surface of
the step 612 in
insert 596. In similar manner inboard, wedge member 586 has a hypotenuse face
614 that
bears against the inboard land portion 616 of insert 596. The total width of
bolster pocket
580 is greater than the combined width of wedge members, such that a gap is
provided
between the inboard (non-contacting) face of member 586 and the inboard planar
face of
pocket 580. The same relationship, but of opposite hand, exists between pocket
582 and
members 592, 594. A low friction pad, or surfacing, may be used at the
interface of
members 586, 588 (or 592, 594) to facilitate sliding motion of the one
relative to the other.
In this arrangement, working of the wedges, i.e., members 586, 588 against the
face
of insert 596 may tend to cause both members to move in one direction, namely
to their most
outboard position. Similarly, members 592 and 594 may tend to work to their
most inboard
positions. This may tend to maintain the wedge members in an untwisted
orientation, and
may also tend to maintain the moment arm of the restoring moment at its
largest value. In
the arrangement of Figures 18b and 18d, a single, stepped wedge 620 is used in
place of the
pair of split wedges e.g., members 586, 588. A corresponding wedge of opposite
hand is
used in the other bolster pocket.
In the embodiment of Figures 19a, a truck bolster 630 has welded bolster
pocket
inserts 632 and 634 of opposite hands welded into accommodations in its distal
end. In this
instance, each bolster pocket has an inboard portion 636 and an outboard
portion 638.
Inboard and outboard portions 636 and 638 share the same primary angle a, but
have
secondary angles 13 that are of opposite hand. Respective inboard and outboard
wedges are
indicated as 640 and 642, and each seats over a vertically oriented spring
644, 646. In this
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case bolster 630 is similar to bolster 480 of Figure 16a, to the extent that
the bolster pocket is
continuous ¨ there is no land separating the inner and outer portions of the
bolster pocket.
Bolster 630 is also similar to bolster 510 of Figure 17a, except that the
bolster pockets of
opposite hand are merged without an intervening land. In the further
alternative of Figure
19b, split wedge pairs 648, 650 (inboard) and 652, 654 (outboard) are employed
in place of
the single inboard and outboard wedges 640 and 642. In some instances the
primary angle of
the wedge may be steep enough that the thickness of section over the spring
might not be
overly great. In such a circumstance the wedge may be stepped in cross section
to yield the
desired thickness of section as show in the details of Figures 19c and 19d.
Figure 20a shows the placement of a low friction bearing pad for bolster 660
of
Figure 16a. Such a pad can be used at the interface between the friction
damper wedges of
any of the embodiments discussed herein. In Figure 20a, the truck bolster is
identified as
item 660 and the side frame is identified as item 662. Side frame 662 is
symmetrical about
the truck centerline, indicated as 664. Side frame 662 has side frame columns
668 that locate
between the inner and outer gibs 670, 672 of truck bolster 660. The spring
group is indicated
generally as 674, and has eight relatively large diameter springs arranged in
two rows, being
an inboard row and an outboard row. Each row has four springs in it. The four
central
springs 676, 677, 678, 679 seat directly under the bolster end. The end
springs of each row,
681, 682, 683, 684 seat under respective friction damper wedges 685, 686, 687,
688. Wear
plates 689, 690 are mounted to the wide, facing flanges 691, 692 of the side
frame columns,
668. As shown in Figure 20b, plates 689, 690 are mounted centrally relative to
the side
frames, beneath the juncture of the side frame arch 692 with the side frame
columns. The
lower longitudinal member of the side frame, bearing the spring seat, is
indicated as 694.
Referring now to Figure 20c and 20e, bolster 660 has a pair of left and right
hand,
welded-in bolster pocket assemblies 700, 701, each having a cast steel,
replaceable, welded-
in wedge pocket insert 702. Insert 702 has an inboard-biased portion 704, and
an outboard-
biased portion 705. Inboard end spring 682 (or 681) bears against an inboard-
biased split
wedge pair 706 having members 708, 709, and outboard end spring 684 (or 683)
bears
against an outboard- biased split wedge pair 710 having members 711, 712. As
suggested by
the names, the outboard-biased wedges will tend to seat in an outboard
position as the
suspension works, and the inboard-biased wedges will tend to seat in an
inboard position.
Each insert portion 704, 705 is split into a first part and a second part for
engaging,
respectively, the first and second members of a commonly biased split wedge
pair.
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Considering pair 706, inboard leading member 708 has an inboard planar face
714, that, in
use, is intended slidingly to contact the opposed vertically planar face of
the bolster pocket.
Leading member 708 has a bearing face 716 having primary angle a and secondary
angle p.
Trailing member 709 has a bearing face 717 also having primary angle a and
secondary
angle p, and, in addition, has a transition, or step, face 718 that has a
primary angle a and a
tertiary angle 9, where tertiary angle 9 is a rake angle tending to oppose the
direction of bias
of secondary angle p.
Insert 702 has a corresponding array of bearing surfaces having a primary
angle a,
and a secondary angle 13, with transition surfaces having tertiary angle 9 for
mating
engagement with the corresponding surfaces of the inboard and outboard split
wedge
members. As can be seen, a section taken through the bearing surface resembles
a chevron
with two unequal wings in which the face of the secondary angle p is
relatively broad and
shallow and the face associated with tertiary angle 9 is relatively narrow and
steep.
In Figure 20e, the sloped portions of split wedge members 711, 712 extend only
partially far enough to overlie a coil spring 716. In consequence, wedge
members 711 and
712 each have a base portion 717, 718 having a fore-and-aft dimension greater
than the
diameter of spring 716, and a width greater than half the diameter of spring
716. Each of
base portions 717, 718 has a downwardly proud, roughly semi-circular boss 720
for seating
in the top of the coil of spring 716. The upwardly angled portion 722, 723 of
each wedge
member 711, 712 extends upwardly of base portion 717, 718 to engage the
matingly angled
portions of insert 702.
In a further alternate embodiment, the split wedges may be replaced with
stepped
wedges 724 of similar compound profile, as shown in Figure 20f. In the event
that the
primary wedge angle a is relatively steep (i.e., greater than about 45 degrees
when measured
from the horizontal, or less than about 45 degrees when measured from the
vertical). Figure
20g shows a welded in insert 726 having a profile for mating engagement with
the
corresponding wedge faces.
Figures 15d and 15e show a bolster, side frame and damper arrangement having
dampers 730, 731 independently sprung on horizontally acting springs 732, 733
housed in
side-by-side pockets 734, 735 in the distal end of bolster 736. While only two
dampers are
shown, a pair of such dampers faces toward each of the opposed side frame
columns.
Dampers 730, 731 each include a block 738 and a consumable wear member 740,
the block
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and wear member having male and female indexing features 742 to maintain their
relative
position. Such an arrangement may permit the damper force to be independent of
the spring
compression in the main spring group. A removable grub screw fitting 744 is
provided in the
spring housing to permit the spring to be pre-loaded and held in place during
installation.
Figure lj shows an example of a three piece railroad car truck, shown
generally as 750.
Truck 750 has a truck bolster 752, and a pair of sideframes 754. The spring
groups of truck 750
are indicated as 756. Spring groups 756 are spring groups having three springs
758 (inboard
corner), 760 (center) and 762 (outboard corner) most closely adjacent to the
sideframe columns
754. A motion calming, kinematic energy dissipating element, in the nature of
a friction damper
764, 766 is mounted over each of central springs 760.
Friction damper 764, 766 has a substantially planar friction face 768 mounted
in facing,
planar opposition to, and for engagement with, a side frame wear member in the
nature of a
wear plate 770 mounted to sideframe column 754. The base of damper 764, 766
defines a
spring seat, or socket 772 into which the upper end of central spring 760
seats. Damper 764,
766 has a third face, being an inclined slope or hypotenuse face 774 for
mating engagement with
a sloped face 776 inside sloped bolster pocket 778. Compression of spring 760
under an end of
the truck bolster may tend to load damper 764 or 766, as may be, such that
friction face 768 is
biased against the opposing bearing face of the sideframe wear column, such as
780.
Truck 750 also has wheelsets whose bearings are mounted in the pedestal 784 at
either
ends of the side frames 754. Each of these pedestals may accommodate one or
another of the
sideframe to bearing adapter interface assemblies described above in the
context of Figures 2a ¨
12f and may thereby have a measure of self steering.
In this embodiment, face 768 of friction damper 764, 766 may have a bearing
surface
having a co-efficient of static friction, p,õ and a co-efficient of dynamic or
kinetic friction, 1.1 k.
that may tend to exhibit little or no "stick-slip" behaviour when operating
against the wear
surface of wear plate 770. In one embodiment, the coefficients of friction are
within 10 % of
each other. In another embodiment the co-efficients of friction are
substantially equal and may
be substantially free of stick-slip behaviour. In one embodiment, when dry,
the co-efficients of
friction may be in the range of 0.10 to 0.45, may be in the narrower range of
0.15 to 0.35, and
may be about 0.30. Friction damper 764, 766 may have a friction face coating,
or bonded pad
786 having these friction properties, and corresponding to those inserts or
pads described in the
context of Figures 21a- 21c, and Figures 22a ¨ 22h. Bonded pad 786 may be a
polymeric pad
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or coating. A low friction, or controlled friction pad or coating 788 may also
be employed on
the sloped surface of the damper. In one embodiment that coating or pad 788
may have co-
efficients of static and dynamic friction that are within 20 %, or, more
narrowly, 10 % of each
other. In another embodiment, the co-efficients of static and dynamic friction
are substantially
equal. The co-efficient of dynamic friction may be in the range of 0.10 to
0.30, and may be
about 0.20.
Friction Surfaces
It may be desirable for rail road car trucks to exhibit relatively low curving
resistance.
One AAR standard suggests a curving resistance of 0.4 lbs/(degree-ton) where
the "degree"
is the number of degrees of angular arc in a 100 ft section of track. It may
also be desirable
for a railroad car truck to possess a disinclination to exhibit "wheel lift"
in operation. Wheel
lift may occur, for example, on a curve where there is super cross-elevation,
and, at some
point along the super-elevated curve the outside rail has one or more downward
perturbations
that may cause the car to rock while going through the curve. One AAR standard
for this is
that, during a particular wheel lift test, the weight on any wheel in the
truck ought not to fall
below 10 % of the static wheel load.
In the view of the present inventors, wheel lift may tend to occur more easily
where
the dampers exhibit a "stick-slip" operation that may tend to be associated
with use of
dampers having distinctly different co-efficients of static and dynamic
friction. In that light,
dampers may be employed whose friction faces have linings, such as may be akin
to brake or
clutch linings that may tend not to exhibit the stick-slip phenomenon, or to
exhibit it only
mildly. Such a prepared bearing surface may also be formed of a cast alloy of
a suitable,
non-galling composition, or from a sintered powder metal composition. That is,
the bearing
surface may be formed of a composition having known co-efficients of static
and dynamic
friction. These co-efficients of friction may be within 10 % of each other. In
one
embodiment the co-efficients of static and dynamic friction may be
approximately equal.
The bodies of the damper wedges themselves may be made from a relatively
common
material, such as a mild steel or cast iron. The wedges may then be given wear
face members
in the nature of shoes, wear inserts or other wear members, which may be
intended to be
consumable items. Such an arrangement is shown in Figure 21 or 22a ¨ 22f.
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In Figure 21a, a damper wedge is shown generically as 800. The replaceable,
friction
modification consumable wear members are indicated as 802, 804. The wedges and
wear
members have mating male and female mechanical interlink features, such as the
cross-
shaped relief 803 formed in the primary angled and vertical faces of wedge 800
for mating
with the corresponding raised cross shaped features 805 of wear members 802,
804. Sliding
wear member 802 may be made of a material having specified friction
properties, and may be
obtained from a supplier of such materials as, for example, brake and clutch
linings and the
like, such as Railway Friction Products, above. The materials may include
materials that are
referred to as being non-metallic, low friction materials, and may include
UHMW polymers.
Although Figures 21a and 21c show consumable inserts in the nature of a wear
plates,
namely wear member 802, 804 the entire bolster pocket may be made as a
replaceable part,
as in Figure 16a. This bolster pocket may be a high precision casting, or may
include a
sintered powder metal assembly having suitable physical properties. The part
so formed may
then be welded into place in the end of the bolster, as at 506 indicated in
Figure 16a.
The underside of the wedges described herein, wedge 800 being typical in this
regard,
has a seat, or socket 807, for engaging the top end of the spring coil,
whichever spring it may
be, spring 562 being shown as typically representative. Socket 807 serves to
discourage the
top end of the spring from wandering away from the intended generally central
position
under the wedge. A bottom seat, or boss for discouraging lateral wandering of
the bottom
end of the spring is shown in Figure 14a as item 808.
It may be noted that wedge 800 has a primary angle, but does not have a
secondary
rake angle. In that regard, wedge 800 may be used as damper 764, 766 of truck
750 of
Figure 1j, for example, and may provide friction damping with little or no
"stick-slip"
behaviour, but rather friction damping for which the co-efficients of static
and dynamic
friction are equal, or only differ by a small (less than about 20%, perhaps
less than 10%)
difference. Wedge 800 may be used in truck 750 in conjunction with a bi-
directional bearing
adapter of any of the embodiments described herein. Wedge 800 may also be used
in a four
cornered damper arrangement, as in truck 20 or 22, for example, where wedges
may be
employed that do not use secondary angles.
Referring to Figures 22a ¨ 22e, a damper 810 is shown such as may be used in
truck
20, truck 22, or any of the other double damper trucks described herein, and
may be mounted
to engage an appropriately formed, mating bolster pocket. Damper 810 is
similar to damper
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800, but may include both primary and secondary angles. It may be noted that
damper 810
may, arbitrarily, be termed a right handed damper wedge, and that Figures 22a
¨ 22e are
intended to be generic such that it may be understood also to represent the
left handed, mirror
image of a mating damper with which damper 810 would form a matched pair.
Wedge 810 has a body 812 that may be made by casting or by another suitable
process. Body 812 may be made of steel or cast iron, and may be substantially
hollow.
Body 812 has a first, substantially planar platen portion 814 having a first
face for placement
in a generally vertical orientation in opposition to a sideframe bearing
surface, for example, a
wear plate mounted on a sideframe column. Platen portion 814 may have a
rebate, or relief,
or depression formed therein to receive a bearing member, indicated as member
816.
Member 816 may be a material having specific friction properties when used in
conjunction
with the sideframe column wear plate material. For example, member 816 may be
formed of
a brake lining material, and the column wear plate may be formed from a high
hardness steel.
Body 812 may also include a base portion 818 that may extend rearwardly from
and
generally perpendicularly to, platen portion 814. Base portion 818 may have a
relief 820
formed therein in a manner to form, roughly, the negative impression of an end
of a spring
coil, such as may receive a top end of a coil of a spring of a spring group,
such as spring 562.
Base portion 818 may join platen portion 814 at an intermediate height, such
that a lower
portion 821 of platen portion 814 may depend downwardly therebeyond in the
manner of a
skirt. That skirt portion may include a corner, or wrap around portion 822
formed to seat
around a portion of the spring.
Body 812 may also include a diagonal member in the nature of a sloped member
824.
Sloped member 824 may have a first, or lower end extending from the distal end
of base 818
and running upwardly and forwardly toward a junction with platen portion 814.
An upper
region 826 of platen portion 814 may extend upwardly beyond that point of
junction, such
that damper wedge 810 may have a footprint having a vertical extent somewhat
greater than
the vertical extent of sloped member 824. Sloped member 824 may also have a
socket or
seat in the nature of a relief or rebate 828 formed therein for receiving a
sliding face member
830 for engagement with the bolster pocket wear plate of the bolster pocket
into which
wedge 810 may seat. As may be seen sloped member 824 (and face member 830) are
inclined at a primary angle a, and a secondary angle P. Sliding face member
830 may be an
element of chosen, possibly relatively low, friction properties (when engaged
with the bolster
pocket wear plate), such as may include desired values of co-efficients of
static and dynamic
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friction. In one embodiment the co-efficients of static and dynamic friction
may be
substantially equal, may be about 0.2 (+1- 20 %, or, more narrowly +1- 10%),
and may be
substantially free of stick-slip behaviour.
In the alternative embodiment of Figure 22g, a damper wedge 832 is similar to
damper wedge 810, but, in addition to pads or inserts for providing modified
or controlled
friction properties on the friction face for engaging the sideframe column and
on the face for
engaging the slope of the bolster pocket, damper wedge 832 may have pads or
inserts such as
pad 834 on the side faces of the wedge for engaging the side faces of the
bolster pockets. In
this regard, it may be desirable for pad 834 to have low co-efficients of
friction, and to tend
to be free of stick slip behaviour. The friction materials may be cast or
bonded in place, and
may include mechanical interlocking features, such as shown in Figure 21a, or
bosses,
grooves, splines, or the like such as may be used for the same purpose.
Similarly, in the
alternative embodiment of Figure 22h, a damper wedge 836 is provided in which
the slope
face insert or pad, and the side wall insert or pad form a continuous, or
monolithic, element,
indicated as 838. The material of the pad or insert may, again, be cast in
place, and may
include mechanical interlock features. The materials may be the same as used
in the Barber
"Twin Guard" split wedge covering materials, and may be formed in the same
manner.
The present inventors consider the use of a controlled friction interface
between the
slope face and the inclined face of the bolster pocket, in which the
combination of wear plate
and friction member may tend to yield co-efficients of friction of known
properties to be
advantageous. It may be desirable for those co-efficients to be the same, or
nearly the same,
and for the combination chosen to have little or no tendency to exhibit stick-
slip behaviour,
or a reduced stick-slip tendency as compared to cast iron on steel. Further,
the use of brake
linings, or inserts of cast materials having known friction properties may
tend to permit the
properties to be controlled within a narrower, more predictable and more
repeatable range
such as may yield a reasonable level of consistency in operation.
In the various truck embodiments, there is a friction damping interface
between the
dampers, of whatever embodiment, and the mating opposed sideframe, of whatever
embodiment. It may be that either the sideframe column or the damper may have
a bearing
surface, either of which may be intended to be consumable, or replaceable, or
both. That is,
the sideframe column may have a sideframe column wear plate that may be bolted
in
position, and then welded in place. Such wear plates may be of a particular
material chosen
for its wear properties. The material may have a certain level of hardness; it
may yield
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desired co-efficients of static and dynamic friction when combined with a
mating material of
a damper friction face. If the wear plate is worn or broken, it may be removed
and replaced.
Similarly, the friction face of a mating damper may be consumable, as in the
nature of a
brake shoe or brake lining, the damper being removable and replaceable once
the friction
face is worn away. The damper friction face may be of a specifically chosen
material to
yield desired wear and friction co-efficient properties. Although the
sideframe column is
customarily the portion provided with a wear plate, the "wear plate" could be
on the face of
the damper, and the friction material, such as may be a brake lining or a
material analogous
thereto, may be mounted on the sideframe column.
In each of the damper to sideframe column arrangements shown and described,
the
bearing face of the motion calming, friction damping element may be treated to
yield a
desired co-efficient of static friction, and a desired co-efficient of dynamic
friction. This
treatment may include, whether by way of an insert or otherwise, a pad, a
coating, or the use
of a brake shoe or brake lining, such as may be obtained from a supplier of
such equipment
as clutch and brake linings and the like. One such supplier is Railway
Friction Products.
Such a brake shoe or lining may have a polymer based, or composite matrix
loaded with a
mixture of metal or other particles or materials such as may yield a specified
friction
performance. That friction surface may, when employed in combination with the
opposed
bearing surface, have a co-efficient of static friction, 14, and a co-
efficient of dynamic or kinetic
friction, lk. The coefficients may vary with environmental conditions. For the
purposes of this
description, the friction co-efficients will be taken as being considered on a
dry day condition at
70 F. In one embodiment, those coefficients of friction may be within 20 %,
or, more narrowly,
within 10 % of each other. In another embodiment the co-efficients of friction
are substantially
equal. In one embodiment, when dry, the co-efficients of friction may be in
the range of 0.15 to
0.45, may be in the narrower range of 0.20 to 0.35, and, in one embodiment,
may be about 0.30.
Ti one embodiment that coating, or pad, may, when employed in combination with
the opposed
bearing surface of the sideframe column, result in co-efficients of static and
dynamic friction at
the friction interface that are within 10 % of each other. In another
embodiment, the co-
efficients of static and dynamic friction are substantially equal.
Where damper wedges are employed, a generally low friction, or controlled
friction
pad or coating may also be employed on the sloped surface of the damper that
engages the wear
plate (if such is employed) of the bolster pocket where there may be a
partially sliding, partially
rocking dynamic interaction. The coating, or pad, or lining, may be a
polymeric element, or an
element having a polymeric of composite matrix loaded with suitable friction
materials. It may
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be obtained from a brake or clutch lining manufacturer, or the like. One such
firm that may be
able to provide such friction materials is Railway Friction Products of 13601
Laurinburg
Maxton Ai, Maxton NC. In one embodiment, the material may be the same as, or
similar to, the
material employed by the Standard Car Truck Company in the "Barber Twin Guard"
(t.m.)
damper wedge with polymer covers. In one embodiment the material may be that a
coating, or
pad, may, when employed in combination with the opposed bearing surface of the
sideframe
column, result in co-efficients of static and dynamic friction at the friction
interface that are
within 10 % of each other. In another embodiment, the co-efficients may be
substantially equal.
In another embodiment, the co-efficients of static and dynamic friction are
substantially equal.
The co-efficient of dynamic friction may be in the range of 0.15 to 0.30, and
in one embodiment
may be about 0.20.
A damper may be provided with a friction specific treatment, whether by
coating, pad or
lining, on both the friction face and the slope face. In such case the co-
efficients of friction on
the slope face need not be the same, although they may be. In one embodiment
it may be that
the co-efficients of static and dynamic friction on the friction face may be
about 0.3, and may be
about equal to each other, while the co-efficients of static and dynamic
friction on the slope face
may be about 0.2, and may be about equal to each other. In either case,
whether on the vertical
bearing face against the sideframe column, or on the sloped face in the
bolster pocket, the
present inventors consider it to be advantageous to avoid surface pairings
that may tend to lead
to galling, and tend to consider it advantageous to avoid stick-slip
behaviour.
Furthermore, the various embodiments described herein may employ self-steering
apparatus in combination with dampers that may tend to exhibit little or no
stick-slip. They
may employ a "Pennsy Adapter Plus", sometimes referred to simply as a "Pennsy"
pad, or
other elastomeric pad arrangement for providing self-steering. Alternatively,
they may
employ a bi-directional rocking apparatus, which may include a rocker having a
bearing
surface formed on a compound curve of which several examples have been
illustrated and
described herein.
Further still, the various embodiments described herein may employ a four
cornered
damper wedge arrangement, with bearing surfaces of a non-stick-slip nature, in
combination
with a self steering apparatus, and in particular a bi-directional rocking
self-steering
apparatus, such as a compound curved rocker.
Combinations and Permutations
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The present description recites many examples of dampers and bearing adapter
arrangements. Not all of the features need be present at one time, and various
optional
combinations can be made. As such, the features of the embodiments of several
of the
various figures may be mixed and matched, without departing from the spirit or
scope of the
invention. For the purpose of avoiding redundant description, it will be
understood that the
various damper configurations can be used with spring groups of a 2 X 4, 3 X
3, 3:2:3, 3 X 5
or other arrangement. Similarly, several variations of bearing to pedestal
seat adapter
interface arrangements have been described and illustrated. There are a large
number of
possible combinations and permutations of damper arrangements and bearing
adapter
arrangements. In that light, it may be understood that the various features
can be combined,
without further multiplication of drawings and description.
In the various embodiments of trucks herein, the gibs may be shown mounted to
the
bolster inboard and outboard of the wear plates on the side frame columns. In
the
embodiments shown herein, the clearance between the gibs and the side plates
is desirably
sufficient to permit a motion allowance of at least %" of lateral travel of
the truck bolster
relative to the wheels to either side of neutral, advantageously permits
greater than 1 inch of
travel to either side of neutral, and may permit travel in the range of about
1 or 1 ¨ 1/8" to
about 1 ¨ 5/8 or 1 ¨ 9/16" inches to either side of neutral.
The inventors presently favour embodiments having a combination of a bi-
directional
compound curvature rocker surface, a four cornered damper arrangement in which
the dampers
are provided with friction linings that may tend to exhibit little or no stick-
slip behaviour, and
may have a slope face with a relatively low friction bearing surface. However,
there are many
possible combinations and permutations of the features of the examples shown
herein. In
general it is thought that a self draining geometry may be preferable over one
in which a hollow
is formed and for which a drain hole may be required.
In each of the trucks shown and described herein, the overall ride quality may
depend
on the inter-relation of the spring group layout and physical properties, or
the damper layout
and properties, or both, in combination with the dynamic properties of the
bearing adapter to
pedestal seat interface assembly. It may be advantageous for the lateral
stiffness of the
sideframe acting as a pendulum to be less than the lateral stiffness of the
spring group in
shear. In rail road cars having 110 ton trucks, one embodiment may employ
trucks having
vertical spring group stiffnesses in the range of 16,000 lbs/inch to 36,000
lbs/inch in
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combination with an embodiment of bi-directional bearing adapter to pedestal
seat interface
assemblies as shown and described herein. In another embodiment, the vertical
stiffness of
the spring group may be less than 12,000 lbs./in per spring group, with a
horizontal shear
stiffness of less than 6000 lbs./in.
In either case, the sideframe pendulum may have 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, perhaps between 14 and 18 inches. The
equivalent length
Leg, may be in the range of 8 to 20 inches, depending on truck size and rocker
geometry.
Although truck 20 or 22 may be a 70 ton special, a 70 ton, 100 ton, 110 ton,
or 125 ton truck,
truck 20 or 22 may be a truck size having 33 inch diameter, or 36 or 38 inch
diameter wheels.
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
bottom spring seat,
may be less than the horizontal shear stiffness of the springs. The equivalent
lateral stiffness
of the sideframe ksideframe may be less than 6000 lbs./in. and may be between
about 3500 and
5500 lbs./in., and perhaps in the range of 3700 ¨ 4100 lbs./in. For example,
in one
embodiment a 2 x 4 spring group has 8 inch diameter springs having a total
vertical stiffness
of 9600 lbs./ in. per spring group and a corresponding lateral shear stiffness
kspring shear of
4800 lbs./in. The sideframe has a rigidly mounted lower spring seat. It may be
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 may be that the vertical spring stiffness per spring group lies
in the range of less
than 30,000 lbs./in., that it may be in the range of less than 20,000 lbs./in
and that it may
perhaps be in the range of 4,000 to 12000 lbs./in, and may be about 6000 to
10,000 lbs./in.
The twisting of the springs may have 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.
In the embodiments of trucks having 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. This value may be less than 1000 lbs./in., and
may be less than
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900 lbs./in. The portion of restoring force attributable to unequal
compression of the springs
may tend to be greater for a light car as opposed to a fully laden car.
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.
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 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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