Note: Descriptions are shown in the official language in which they were submitted.
This invention relates to railroad car wheel
mountings and more particularly -to improved differ-
ential wheel and axle constructions.
Rail car differential wheel and axle con-
structions of various types have been disclosed in
the prior art and patents which relate to such con-
struction include: U. S. Patent 201,726, Watkeys,
March 26, 1878; U. S. Paten-t 237,906, Rhett,
February 15, 1881; U. S. Patent 1,292,663, Thomas,
January 2~, 1919; and U. S. Patent 1,316,087, Dowe,
September 16, 1919. These patents disclose various
differential wheel constructions for railroad cars in
which one of a pair of rail car wheels is press-
fitted onto an axial elongated sleeve rotatably
mounted on a rail car axle. In this manner, the
sleeve mounted wheel; is free to rotate about the
axle independently of another wheel which is press-
fitted directly adjacent the other end of the axle.
Among the drawbacks of these constructions are the
difficulty of bearing lubrication, the fretting of
the metal-to-metal bearing surfaces and the need for
specialized and costly axle constructions.
The assembly disclosed in U. S. Patent
3,321,232, Johnson, May 23, 1967, involves a com-
pletely separate short axle moun-ted onto -the end of a
longer axle. A full length hollow cylindrical axle
is supported on both ends by roller bearings and
the short axle is attached to
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one end of -the hollow axle. This arrangemen-t is
complicated and very costly.
It is the principal object of this invention
to provide differentia] railroad whee] and axle con-
structions which overcome the drawbacks of the prior
art.
It is another object of this invention to
provide a method for adapting conventional railroad
axles for use in differential wheel and axle combina-
tion which meet the standards of the Association ofAmerican Railroads (AAR).
It is a further object of this invention to
provide a differential wheel and axle construction
which relieves the stresses in the wheel-to-axle
interface and eliminates steel-to-steel surface rub-
bing contact subject to fretting.
It is still a further object of this inven-
tion to provide differential wheel and axle construc-
tions which overcome the problems of fretting corro-
sion, brinelling failure and which are capable ofresisting lateral forces caused by rail-on-wheel
thrust.
A construction in accordance with the
present invention includes a differential wheel mount-
ing for railroad cars which have a standard railroad
axle with a raised wheel seat portion adjacent at
least one end. There is provided a first wheel
fixedly mounted adjacent the other end of the axle and
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a second wheel having a hub rotatab]y mounted relative
to the axle on the raised whee], seat of the axle. The
second whee] moun-ting comprises a steel cylindrical
sleeve fitted about the raised wheel seat and having
an axial ]ength suhstantia]]y greater than the Lenyth
of the raised wheel seat to provide extensions inboard
and ou-tboard of the second wheel hub. Means are pro-
vided for retaining the sleeve in fixed axial relation
on the raised whee] seat. Wheel retaining flanges are
affixed to the inboard and outboard extensions of the
sleeve to provide thrust bearing surfaces for the hub
of the second wheel. The opposed annular surfaces of
the wheel hub, the retaining flanges and the inner
cylindrical bore of the hub and the outer bearing sur-
face of the s]eeve are oppositely surfaced with a
relatively hard corrosion and wear resistant metal and
with a nonmeta]lic, long wearing surface of a material
having a low coefficient of friction.
A method in accordance with the present
invention includes the steps of fitting over the
raised wheel seat of the axle, the wheel seat being
defined by outhoard and inboard fillets. A steel
sleeve having a collar portion at one end is adapted
to engage the outboard fille-t and has, at ,its inboard
end, a second collar engaged with the inboard fillet.
The collars retaining the sleeve are ln fixed axial
relatl n on the axle. A wheel having a hub portlon
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with a cylindrica] bore and annu]ar side faces :is
fitted onto the portion of the sleeve disposed about
the raised wheel seat. The bore has a non~metallic
liner bonded thereto of ]ow coefficient of fric-tion,
and the opposed portion of the s]eeve is surfaced with
a polished stainless steel surface. The side faces of
the hub are also surfaced with non-metal]ic washers of
low coefficient of friction. Inboard and outboard
pressure plates are mounted on the inner and outer
axial portions of the sleeve in fixed axial relation
thereon, with the pressure p]ates having annular side
faces of hard, polished stainless steel for thrust
bearing relationship with the side faces of the hub.
The above and other objects and advantages
of this invention will be more readily apparent from
the following description, read in conjunction with
accompanying drawings, in which:
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Fig. 1 is a cross-sectional elevational view of a
railroad car differential wheel and axle bearin~ construc-
tion of the type embodying this invention;
Fig. 2 is an outboard end elevational view on a
reduced scale, of the Fig. 1 embodiment;
Fig. 3 is a view similar to Fig. 2 showing the
opposite end of the bearing construction;
Fig. 4 is a partial cross-sectional ~iew similar to
Fig. 1 showing an alternative bearing construction, and
Fig. 5 is a view similar to Fig. 4 illustrating
another alternative bearing construction.
Reerring in detail to the drawing, in Fig. 1 is
shown a railroad wheel 6 which has annular hub portion 8
supported for rotation about an axle 10. The axle
includes a raised wheel seat portion 12 of substantially
greater diameter than that of the remainder of the axle.
The axle includes a curved shoulder or fillet 14 adjacent
its outboard end 16 and similar fillet 18 facing toward
the inboard portion 20 of the axle.
A metallic sleeve or spool 22 is fitted over the
enlarged wheel seat portion of the axle and includes, at
its outboard end, an annular rim or bead 24 of convex
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curvature adapted to mate with the concave fillet 14 in
surface-to-surface contact. The outer end portion of the
spool is externally thre~ded, as indicated at 26 and the
spool has a length substantially greater than the axial
length of the wheel seat portion 12 of the axle and the
inboard end of the spool is internally threaded, as shown
at 28.
A split collar 30 (Fig. 3) having two semicircular
halves 32 and 34 is fitted around the inboard portion of
the axle 10. The two hal~es may be fastened together by
bolts or other fasteners extending through threaded holes
36 which circumferentially span the mating surfaces of the
two halves to provide the split cylindrical collar 30. At
its inner end, the collar 3 is externally threaded to
screw-fit with the internally threaded spool 22~
At its outer end, disposed adjacent the wheel seat
12, the inner surface of the collar 30 is formed with an
annular radius portion 38 which engages the fillet 18 of
the shaft.
Disposed on the outer surface of the sleeve 22 is a
plate or flange which is welded onto the sleeve, as shown
in Fig. 1, and serves as an inboard retainer or pressure
plate 40 for the hub of the wheel 6. The plate 40
includes an inner, annular bearing surface 42 onto which a
stainless steel surface 45 is deposited preferably by a
plasma arc processO The inboard pressure plate incllldes
an inwardly ex~ending axial rim portion 4~ in wllich is
fitted a ring seal 46, w~lich may be an oil satura-ted felt
s~al ring.
An outboard pressure plate 48 is screw-fitted onto
the outboard end portion of the spool or sleeve 22. This
plate is internally threaded and also has an annular
stainless steel inner bearing surEace 50. The plate 48
also includes an axially extending rim portion 52 with a
! seal ring 54 carried therein. 'rhe outboard pressure plate
48, as shown in Fig. 2, includes a plurality o radially
extending, uniformly, circumferentially spaced threaded
bores 66 adapted to receive soft-nosed set screws ~not
shown) to secure the plate 48 in fixed position on tlle
sleeve 22 to produce the desired resisting torque.
The hub portion 8 of tlle wheel 6 which is generally
rectangular in cross-section includes annular surfaces
coated Wit]l wear resistant thrust washers having a low
coef~icient of friction, such as polytetrafluoethylene
marketed under the Trademark "TEFLON"* as indicated at 56
and 58. A cylindrical liner or sleeve oE T~FLON 60 is
also bonded to the axial bore of the wheel 6 and this low
fric~ion material is in contact with a stainless steel
* A trade mark of E. I. du Pont de Nemours
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surface 62 deposited by plasma arc process onto the outer
surface of the portion of sleeve 22 corresponding in
length to the TEFLON sleeve 60. The TEFLQN liners may be
fiber reinforced with a glass fiber matrix or the like~
With this construction, the wheel bearing is completely
sealed by the inner and outer pressure plates and by ring
seals 46 and 54. There is, moreover, an absence of metal-
to-me~al contact in the wheel bearing since both the axial
and radial surfaces of the wheel hub are TEFLON coated,
while the mating surfaces of the sleeve 22 and the pres-
sure plates are stainless steel coated by the plasma arc
process.
A number of alternate rubbing surfaces are consid-
ered acceptable~ such as a plasma arc deposited aluminum
alloy of the harder alloys, polished to a mirror finish
could be employed in place of the stainless steel. Oven-
sintered T~PLON derivatives, such as "RITON", may be
applied directly onto the outer surface of the sleeve 22
and the annular bearing surfaces 45 and 50 of the pressure
plates in place of the stainless steel surfacing.
Alternatively) the bore and annular side faces of
the wheel hub could be left as machined, ground and pol-
ished carbon steel bearing on oven-sintered T~FLON applied
to the outer surface of the sleeve 22 and the annular
faces of the inboard and outboard pressure plates.
By referring to Fig. 1, it will be recognized that
the load path for reaction to any lateral or transverse
load applied by a rail to the wheel 6 would be applied by
the wheel hub to the inboard or outboard pressure plates
40 or 48, depending upon the direction of the thrust. In
either case, the forces would be transmitted by the TEFLON
coating 56 or 58 on the wheel hub to the stainless steel
surfaces 45 or 50 of the respective pressure plates. Any
rubbing that occurs between these two surfaces is at a
very low coefficient of friction and this combination of
materials completely eliminates fretting and stick-slip
between these bearing surfaces. The spool 22 in turn
transmits that load into the axle itself primarily by the
annular surfaces 24 and 38 bearing against the fillets 14
and 38. Some of the load is transmitted to the raised
wheel seat 12 by the light press-fit of the sleeve 22
thereon.
In Fig. 4, an alternative embodiment of this inven-
tion is shown in which the split sleeve 30 of Figs~ 1 and
3 is replaced by a collar 70 of annular configuration.
The tubular collar 70 is Eitted onto the inboard end of
the axle 10 and is swaged so that its inner surface will
closely conform with the inboard fillet 18 of the raised
wheel seat 12. The collar 70 is of sufficient axial
length, on the order -of approximately six (6") inches, so
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that its external surface added to that of the raised
wheel seat will permit the axle sleeve or spool Z2 to be
simply press-fitted thereon with sufficient axial stabil-
ity to meet the standards of the Association of ~merican
Railroads (A.A.R.). This alternate construction may be
carried one step further by machining the outer surface of
the collar 70 to bring it to the same diameter as the
wheel seat 12. After press-fitting the sleeve 22 onto the
axle and collar 70, radially extending, circumferentially
spaced fasteners, such as set screws 72, may be used to
provide additional structure stability between the collar
70 and sleeve 22. It is important, however, that these
fasteners not be allowed to extend into contact with
axle 10.
In Fig. 5, another alternate embodiment is shown in
which the axle spool or sleeve 22 is provided with an
enlarged end portion. After fitting the sleeve 22 onto
the axle 1OJ the end portion of the sleeve is swaged in-
wardly so that its inner surface will conform with the
inboard fillet 18 of the axle 10. After swaging, the axle
spool is machined to provide a raised surface which is
then threaded, as shown at 74 in Fig. 5. An inboard pres-
sure plate 76 may be screw-fitted onto the sleeve 22 and
locked in place by set screws extending through a plural-
ity of circumferentially spaced, threaded, radial bores
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78. This embodiment is considered to be preferable for
large scale assembly line retrof:it of rail axles because
it provides the easiest attainment of perfect thread
gauge.
The Fig. 5 embodiment may also be modified somewhat
by omitting the screw threads 74 on the sleeve 22 and then
welding an inboard pressure plate to the inner end of the
sleeve in a manner similar to the end plate 40 of Fig. 1.
In the method embodying this invention, a steel
sleeve or spool is telescopically tilted onto the raised
wheel seat of a railroad car axle. The sleeve has an
axial length substantially greater in length than that of
the raised wheel seat. Pillets define the inboard and
outboard ends of the raised wheel seat and the sleeve
includes an annular collar portion which engages the out-
board fillet. The collar means carried by the sleeve
engage the inboard fille~ to retain the sleeve in fixed
axial relation on the axle. The hub of a railroad wheel
is then fitted onto that portion of the sleeve corres-
ponding to the raised wheel seat. The inner cylindrical
bearing surace of the hub and the riding surface of the
sleeve are oppositely surfaced with a non-metallic
material having a low coefficient of friction and a hard,
polished metallic surface. Inboard and outboard pressure
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plates fixedly mounted on the sleeve and then inner annu-
lar surfaces and the opposing outer annular surfaces of
the wheel hub are oppositely surfaced with non-metallic
material having a low coefficient of friction and a hard,
polished metallic surface. l'he pressure plates are each
provided with ring seals for completely sealing the wheel
bearing surfaces.
Having thus disclosed this invention, what is
claimed is:
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