Patent Description:
Conventional rail wheels comprise a single component that is secured to an axle of a rail car utilizing an interference press fit at the wheel/axle interface. The process of securing the wheel to the axle requires a specialized press capable of forces over <NUM> tons (e.g., a specialized <NUM>-ton press) to remove and attach the wheel. The operation requires highly-specialized knowledge by the press operators to assure proper and safe fit of the wheel to the axle. A typical interference may be <NUM>-<NUM> inches. This press fit design has a high risk of damage to both the wheel during installation and removal. Therefore, any method to replace a wheel while eliminating removal of press fit components would be of great benefit to the vehicle operator.

In order to replace and/or repair a conventional rail wheel, the entire truck must be removed from the rail car and the axle/wheel assembly must be removed from the truck. Then it is possible to remove the wheel from the axle using press equipment. Indeed, as the current state of the art requires a large, factory-based press machine, it is not possible to change wheels in the field or on the rail. Instead, the current state of the art requires changing the wheels at the factory where the specialized press machine is available. As a result, the process to replace or repair a wheel of a rail car requires significant time out of service. Additionally, because conventional rail wheels comprise a single component, any damage to the wheel requires removing and potentially replacing the entire wheel in order to place the train back in service.

A wheel design that does not require removing and disassembling the truck (and the frame that holds the axles) when changing a wheel and that allows less than the entirety of the rail wheel to be removed and replaced when a wheel is damaged would be a significant improvement. <CIT> discloses a railway wheel, wherein a tire unit is fastened to a web plate integrated with a hub with bolts such that the tire unit is coupled to an outer side of the web plate. The web plate and the tire unit are coupled to each other by fastening the bolts horizontally. <CIT> discloses an air railway vehicle running gear comprising a hub, a running wheel, an axle, and a vehicle body connecting plate. Axle holes in the form of horizontal blind holes are respectively symmetrically formed in the two sides of the vehicle body connecting plate. The hub and the running wheel are installed at one end of the axle, and the other end of the axle is installed in the axle hole in an interference fit manner and is located through a step surface on the axle. A further rail wheel assembly is disclosed in <CIT>.

According to a first aspect of the invention, there is provided a rail wheel assembly as defined in claim <NUM>. According to a second aspect of the invention, there is provided a method for changing a tire of a railroad wheel assembly affixed to a railway vehicle, as defined in claim <NUM>. Aspects of this invention relate to a rail wheel assembly that allows a tire to be replaced without requiring disassembly of the rail vehicle or removal of components directly attached to the axle. In various embodiments, the rail wheel assembly comprises a center wheel hub and a tire configured to engage a rail. The center wheel hub is attached to an axle of a railway vehicle with an interference press fit and includes an outward facing stepped interface located at an outer edge of the center hub. The tire includes an inward facing stepped interface located at an inner edge of the tire. The outward facing stepped interface of the center hub is configured to receive the inward facing stepped interface of the tire. Each of the outward facing stepped interface on the center wheel hub and the inward facing stepped interface of the tire include a plurality of holes configured to receive bolts configured to secure the tire to the rail wheel assembly via the center wheel hub. In various embodiments, the outward facing stepped interface of the center hub interfaces directly with the inward facing stepped interface of the tire (i.e., without any components between the outward facing stepped interface and the inward facing stepped interface).

The two-piece rail wheel assembly described herein may serve a replacement for a one-piece solid steel wheel conventionally used on rail cars and other rail vehicles. Unlike conventional rail car wheels, however, the tire of the rail wheel assembly described herein may be removed and replaced without requiring removal of any of the components affixed directly to the axle. For example, in an in-board bearing configuration, a tire may be replaced on the rail wheel assembly described herein by simply lifting the rail car up, unbolting the tire from the center hub, sliding the tire off the axle, sliding a new tire on, bolting the new tire to the center hub, and lowering the rail car down onto the track. Unlike the process for removing conventional rail wheels, this process does not require using a press machine, detaching the truck assembly from the rail car, or detaching the wheelset (which includes at least the axle, gearbox, bearings, and wheels) from the truck. In order to replace a tire in an out-board bearing configuration using the rail wheel assembly described herein, the truck assembly will need to be detached from the rail car, and the wheelset removed from the truck assembly. However, unlike the process for removing conventional rail wheels in out-board bearing configurations, the rail wheel assembly described herein eliminates the need to use a press machine or remove any other components of the wheelset from axle, including the bearings, brake discs, gearbox, grounding system, and/or any other components of the wheelset. As such, the likelihood of these components being damaged or these components needing to be requalified or replaced is reduced.

These and other objects, features, and characteristics of the invention disclosed herein will become more apparent upon consideration of the following description and the appended claims with reference to the accompanying drawings, all of which form a part of this specification, wherein like reference numerals designate corresponding parts in the various figures.

The present invention is illustrated by way of example and not limited in the accompanying figures in which like reference numerals indicate similar elements and in which:.

These drawings are provided for purposes of illustration only and merely depict typical or example embodiments. These drawings are provided to facilitate the reader's understanding and shall not be considered limiting of the breadth, scope, or applicability of the disclosure. For clarity and ease of illustration, these drawings are not necessarily drawn to scale.

In the following description of various examples of the invention, reference is made to the accompanying drawings, which form a part hereof, and in which are shown by way of illustration various example structures, systems, and steps in which aspects of the invention may be practiced. It is to be understood that other specific arrangements of parts, structures, example devices, systems, and steps may be utilized, and structural and functional modifications may be made without departing from the scope of the present invention. Also, while the terms "top," "bottom," "front," "back," "side," and the like may be used in this specification to describe various example features and elements of the invention, these terms are used herein as a matter of convenience, e.g., based on the example orientations shown in the figures. Nothing in this specification should be construed as requiring a specific three-dimensional orientation of structures in order to fall within the scope of this invention.

The invention described herein relates to a two-piece railroad wheel assembly that allows a tire to be replaced without requiring disassembly of the rail vehicle or removal of components directly attached to the axle. While this wheel assembly is designed specifically for rail wheels on rail cars, this wheel assembly design and the corresponding methods described herein may be utilized with any transit system or railway vehicle that utilizes press-fit wheel/axle assemblies.

<FIG> and <FIG> depict a two-piece railroad wheel assembly <NUM> attached to an axle <NUM> of a rail car. Specifically, <FIG> depicts a perspective view of two-piece railroad wheel assembly <NUM> attached to an axle <NUM> of a rail car, and <FIG> depicts a perspective sectional view of two-piece railroad wheel assembly <NUM>. In various embodiments, two-piece railroad wheel assembly <NUM> may comprise a center hub <NUM>, a tire <NUM>, and/or one or more other components. In various embodiments, center hub <NUM> and tire <NUM> may be connected to form two-piece railroad wheel assembly <NUM>, which when attached to an axle of a rail car, may comprise a single wheel of the rail car. In various embodiments, center hub <NUM> and tire <NUM> may be bolted together via a stepped (or recessed) interface <NUM>. In various embodiments, the stepped or recessed interface <NUM> between center hub <NUM> and tire <NUM> may not allow shear stress in the lateral or load carrying direction on the bolts used to secure tire <NUM> to center hub <NUM>.

<FIG> depicts a front perspective view of center hub <NUM>, according to one or more aspects described herein. In various embodiments, center hub <NUM> may comprise an interior interface <NUM> and a front axial interface <NUM>. In various embodiments, front axial interface <NUM> of center hub <NUM> may include a plurality of holes <NUM>. As depicted in <FIG>, front axial interface <NUM> may comprise a recessed or stepped interface facing outward from center hub <NUM> (i.e., away from the center of the rail car) and located at an outer edge of center hub <NUM>. In various embodiments, center hub <NUM> may be configured to be permanently or semi-permanently attached to an axle of a rail car with an interference press fit (as is consistent with common practice for standard wheel designs). For example, center hub <NUM> may be slid onto an axle of a rail car and press fit to the axle at interior interface <NUM>. In various embodiments, center hub <NUM> may be configured to remain with an axle of a rail car for the life of the axle or until components inboard center hub <NUM> require removal from the axle for overhaul or replacement. In some embodiments, center hub <NUM> may be reinstalled on the axle and reused if in acceptable condition after being removed.

<FIG> depicts a rear perspective view of tire <NUM>, according to one or more aspects described herein. In various embodiments, tire <NUM> may comprise a rail interface <NUM> and a rear axial interface <NUM>. Rail interface <NUM> of tire <NUM> may be configured to engage a rail when tire is attached to a rail car via center hub <NUM>. In various embodiments, rear axial interface <NUM> of tire <NUM> may include a plurality of holes <NUM>. As depicted in <FIG>, rear axial interface <NUM> may comprise a recessed or stepped interface facing inward from tire <NUM> (i.e., toward the center of the rail car) and located at an inner edge of tire <NUM>. In various embodiments, an internal diameter of tire <NUM> is greater than an outer dimension of a bearing configured to attach a wheelset comprising two-piece railroad wheel assembly <NUM> to a truck assembly. Thus, an inner diameter of tire <NUM> is large enough for tire <NUM> to be slid off the axle without having to remove the bearing when used on a rail car having an out-board bearing configuration. In various embodiments, tire <NUM> may comprise a steel tire configured to interface with a rail in a similar manner to a conventional rail wheel.

<FIG> depict exploded perspective views of two-piece railroad wheel assembly <NUM>, which does not fall under the scope of the claimed invention. Specifically, <FIG> and <FIG> depict exploded perspective views of two-piece railroad wheel assembly <NUM> comprising center hub <NUM> and tire <NUM> bolted together via a stepped or recessed interface, and <FIG> depicts an exploded perspective view of two-piece railroad wheel assembly <NUM> comprising center hub <NUM> attached to axle <NUM> and tire <NUM> bolted to center hub <NUM> via a stepped or recessed interface, according to one or more aspects described herein. In various embodiments, features of center hub <NUM> must be aligned to corresponding features of tire <NUM> in order to attach tire <NUM> to axle <NUM> via center hub <NUM>. For example, front axial interface <NUM> of center hub <NUM> may be configured to receive rear axial interface <NUM> of tire <NUM>. When pressed together, front axial interface <NUM> of center hub <NUM> and rear axial interface <NUM> of tire <NUM> define stepped interface <NUM> as identified in <FIG>. In various embodiments, stepped interface <NUM> may provide circumferential alignment between center hub <NUM> and tire <NUM> and is capable of carrying vehicle forces in operation.

In various embodiments, front axial interface <NUM> of center hub <NUM> directly interfaces with rear axial interface <NUM> of tire <NUM>. In other words, front axial interface <NUM> of center hub <NUM> is flush against rear axial interface <NUM> of tire <NUM>. Any components, material, or space between front axial interface <NUM> of center hub <NUM> and rear axial interface <NUM> of tire <NUM> would cause tire <NUM> to move relative to center hub <NUM>, which would reduce the load carrying capacity of two-piece railroad wheel assembly <NUM> and the speed with which two-piece railroad wheel assembly <NUM> would be able to travel. For example, any components between center hub <NUM> and tire <NUM> would reduce the load carrying capacity and maximum speed of two-piece railroad wheel assembly <NUM> such that it would be suitable for use with freight cars or heavier passenger cars. As such, in various embodiments, center hub <NUM> interfaces directly with tire <NUM> (i.e., without any components between front axial interface <NUM> and rear axial interface <NUM>).

In some embodiments, stepped interface <NUM> may include a taper on corresponding horizontal portions of front axial interface <NUM> and rear axial interface <NUM> to ease mounting of tire <NUM> onto center hub <NUM>. In some embodiments, corrosion prevention features may be utilized in stepped interface <NUM> (i.e., between front axial interface <NUM> and rear axial interface <NUM>). For example, rust prevention features may be utilized in stepped interface <NUM> (i.e., between front axial interface <NUM> and rear axial interface <NUM>).

In various embodiments, the plurality of holes <NUM> on front axial interface <NUM> may align with the plurality of holes <NUM> on rear axial interface <NUM> to form a plurality of holes via which tire <NUM> may be bolted to center hub <NUM>. For example, bolts <NUM> may be inserted into the plurality of holes <NUM>, <NUM> and secured via nuts <NUM> on the opposite side to affix or "lock" tire <NUM> to axle <NUM> via center hub <NUM>. In various embodiments, bolts <NUM> may comprise screws, pins, and/or any other mechanical fastener that is known and used in the art, and nuts <NUM> may comprise any corresponding component known and used in the art that is configured to receive bolts <NUM>. In various embodiments, the nuts <NUM> may comprise self-contained locking nuts. In some embodiments, the nuts <NUM> may include multiple locking features for redundancy. For example, one or more individual nuts <NUM> may include slits in the side of the nuts <NUM> (one on each side) that force the nuts to bind on themselves when removed. The top part above the slit will not want to move where the part below the slit does. In some embodiments, the nuts <NUM> may include slits on each side of the nut that run the entire way through the nut. In some embodiments, the nuts <NUM> may be used in connection with a Belleville-style washer. A Belleville-style washer is a type of conical spring washer that spreads out as you tighten it and acts as a spring force to further lock bolts <NUM> in place using nuts <NUM>. In some embodiments, the combination of bolts <NUM> and nuts <NUM> may include a custom fastener specifically designed for use in two-piece railroad wheel assembly <NUM>. For example, in some embodiments, a no mare fastener may be used to further secure tire <NUM> to center hub <NUM> without marking either the tire <NUM> or center hub <NUM>.

In various embodiments, a plurality of bolts <NUM> may be utilized to secure tire <NUM> to center hub <NUM> via the plurality of holes <NUM>, <NUM>. The number of bolts <NUM> may range from two bolts to ten or even more bolts. In various embodiments, the plurality of holes <NUM>, <NUM> may be geometrically and even spaced around axle <NUM>. For example, twelve bolts <NUM> evenly spaced around the wheel may be utilized to secure tire <NUM> to center hub <NUM> via the plurality of holes <NUM>, <NUM>.

In various embodiments, bolts <NUM> may be configured to provide only clamping force between tire <NUM> and center hub <NUM> and not carry shear forces perpendicular to the bolt centerline. In some embodiments, one or more alignment/shear pins may be utilized in conjunction with bolts <NUM> and nuts <NUM> to secure tire <NUM> to center hub <NUM>. For example, in an example embodiment, one or more of the plurality of bolts <NUM> may be replaced with alignment/shear pins. The alignment/shear pins may be utilized to carry loads between center hub <NUM> and tire <NUM> to avoid shear forces on the bolts.

According to the invention, the two-piece railroad wheel assembly <NUM> includes one or more bolt retaining plates (also interchangeably referred to herein as "bolt retainers") positioned on the rear (or interior) side of center hub <NUM> and configured to hold two or more of bolts <NUM> in place. For example, <FIG> and <FIG> depict two-piece railroad wheel assembly <NUM> comprising bolt retainers <NUM>, according to one or more aspects described herein. Specifically, <FIG> depicts a rear perspective view of two-piece railroad wheel assembly <NUM> comprising bolt retainers <NUM>, and <FIG> depicts a rear perspective sectional view of two-piece railroad wheel assembly <NUM> comprising bolt retainers <NUM>, according to one or more aspects described herein. As depicted in <FIG> and <FIG>, bolt retainers <NUM> may comprise a plate that includes two holes configured to receive two or more bolts <NUM> prior to bolts <NUM> being inserted into holes <NUM> of center hub <NUM>. In some embodiments, each bolt <NUM> may be inserted into a bolt retainer <NUM> with at least one other bolt <NUM>, as depicted in <FIG> and <FIG>. Bolt retainers <NUM> may be configured to temporarily hold bolts <NUM> in position for assembly of the two-piece railroad wheel assembly <NUM>. For example, bolt retainers <NUM> may be configured to hold bolts <NUM> in position within the plurality of holes <NUM> of center hub <NUM> such that bolts <NUM> are aligned for receipt by the plurality of holes <NUM> of tire <NUM>. Bolt retainers <NUM> may be configured to prevent bolts <NUM> from rotating when attaching nuts <NUM> on the opposite side of two-piece railroad wheel assembly <NUM>. As such, bolt retainers <NUM> may eliminate the need for a wrench to screw a nut <NUM> onto a bolt <NUM>, which can reduce the time and difficulty associated with changing a tire <NUM> of two-piece railroad wheel assembly <NUM> as the rear (or interior) side of center hub <NUM> may be difficult to reach when center hub <NUM> is affixed to an axle <NUM>. Bolt retainers <NUM> may also be configured to lock bolts in places once tightened. In other words, bolt retainers <NUM> may be configured to prevent bolts <NUM> from coming loose during travel. In some embodiments, bolt retainers <NUM> may further eliminate the need to include features in wheel that would provide crack propagation point, as bolt retainers <NUM> prevent bolts <NUM> from contacting a side of center hub <NUM>.

<FIG> depicts a perspective view of an axle <NUM> of a rail car with a two-piece railroad wheel assembly <NUM> comprising a center hub <NUM> and a tire <NUM> attached to axle <NUM> on each side of the rail car, which does not fall under the scope of the claimed invention. As described herein, axle <NUM> may comprise a rail car axle. In various embodiments, two-piece railroad wheel assembly <NUM> is a replacement for one-piece solid steel wheels conventionally used on rail cars and other rail vehicles. However, two-piece railroad wheel assembly <NUM> may be compatible with all existing axle designs. Two-piece railroad wheel assembly <NUM> may also be utilized with any transit system that utilizes press-fit wheel/axle assemblies.

Utilizing a two-piece railroad wheel assembly <NUM> comprising a center hub <NUM> and a tire <NUM> may provide many benefits over prior art designs. For example, two-piece railroad wheel assembly <NUM> may allow replacement of tire <NUM> without the need for major disassembly of the rail vehicle. For example, in order to replace and/or repair a conventional rail wheel, the entire rail vehicle must first be moved to a maintenance facility and then lifted with a crane in order to detach the truck assembly. The truck assembly must then be moved to a maintenance stand where the wheelset (which includes the axle, gearbox, bearings, and wheels) is detached from the truck. As described herein, removing a conventional rail wheel requires the use of a large, factory-based press machine that cannot be used to remove the wheel if the wheel set is attached to the truck. The wheelset must then be moved to a wheel press facility wherein the wheels, journal bearings, brake discs, and gearbox are removed from the axle. As described herein, the components of conventional rail wheels are mounted to the axle with interference press fits. As such, disassembly places all the components of the wheelset at risk of damage.

Once disassembled, various components must be requalified or replaced per Association of American Railroads (AAR) requirements depending on whether the rail car has a in-board or out-board bearing configuration. Trucks are attached to axles at journal bearings. In an in-board bearing configuration, the journal bearings are located inside the wheels. In an out-board bearing configuration, the journal bearings are located outside the wheels. Because removing conventional rail wheels requires use of a press machine, and press machines require the wheelset be removed from the truck, the wheelset must be removed from the truck to replace a conventional rail wheel regardless of whether it is in an in-board or out-board bearing configuration. In an out-board bearing configuration (in which the bearing is located outside the wheels), the bearings must also be removed because conventional rail wheels cannot be slid over the bearing. According to AAR Manual of Standards and Recommended Practices, Section G-II, Sub-Section <NUM>. <NUM>, when a journal bearing is removed from an axle, the axle must be wet magnetic particle tested prior to remounting a bearing. AAR Manual of Standards and Recommended Practices, Section G-II, Sub-Section <NUM>. <NUM> further requires that any journal bearing that is removed from an axle for any reason be sent for reconditioning or replaced with a new bearing. As such, when removing a conventional rail wheel from an out-board bearing configuration (which is more common for freight cars and heavier passenger cars), the axles must also be requalified dimensionally and by magnetic particle inspection, and the bearings must be requalified or replaced. In some instances, the brake disc may also need to be requalified or replaced, and the gearbox may need to be rebuilt. Only once these components have been requalified, replaced, and/or rebuilt can the wheelset be reassembled with new wheels.

In order to reassemble the wheelset with new wheels, the wheels, journal bearings, brake discs, and gearbox must all be press fit on the axle. Similar to disassembly, reassembly of these interference fit components places each component at risk of damage. The reassembled wheelset must then be moved to a truck maintenance stand where the truck is rebuilt before being replaced under the vehicle. Before being replaced under the vehicle, however, the same extensive process performed for one wheelset must also be performed on its mate. Per AAR Manual of Standards and Recommended Practices, Section G-II, Sub-Section <NUM>. <NUM>, any time a single wheel is dismounted from an axle, it's mate must also be dismounted regardless of condition.

The process required to replace and/or repair a conventional rail wheel is both labor, cost, and time-intensive. Indeed, in addition to requiring a large, factory-based press machine and posing increased risk of damage to the wheelset and its components, the process to replace or repair a wheel of a rail car also requires significant time out of service. Unlike the labor, cost, and time-intensive process required to replace a conventional rail wheel, replacing tire <NUM> of two-piece railroad wheel assembly <NUM> does not require even removing or disassembling the truck assembly when two-piece railroad wheel assembly <NUM> is utilized in an in-board bearing configuration.

<FIG> illustrates an example of a process <NUM> for changing tire <NUM> of two-piece railroad wheel assembly <NUM> when utilized in an in-board bearing configuration, according to one or more aspects described herein. In an operation <NUM>, process <NUM> may include lifting the rail car on which two-piece railroad wheel assembly <NUM> is affixed to raise tire <NUM> off the track. In various embodiments, the rail car may be moved to a maintenance facility where the rail car is lifted. In an operation <NUM>, process <NUM> may include unbolting tire <NUM> from center hub <NUM> and removing tire <NUM> from axle <NUM>. In an in-board bearing configuration, tire <NUM> can be removed from the axle <NUM> once unbolted from center hub <NUM> without having to remove the wheelset from the truck because the frame of the truck is inside two-piece railroad wheel assembly <NUM>. In an operation <NUM>, process <NUM> may include sliding a new tire <NUM> onto axle <NUM> and bolting the new tire <NUM> to center hub <NUM>. In various embodiments, the hardware used to affix the old tire <NUM> to the center hub <NUM> (e.g., the bolts <NUM>, nuts <NUM>, and/or bolt retainers <NUM>) may disposed of and new hardware may be used to affix the new tire <NUM> to center hub <NUM>. In an operation <NUM>, process <NUM> may include repeating operation <NUM> and operation <NUM> for the two-piece railroad wheel assembly <NUM> on the opposite side of axle <NUM>. In various embodiments, each time a tire <NUM> is replaced, the tire <NUM> of the two-piece railroad wheel assembly <NUM> on the opposite side of the wheelset (or axle <NUM>) must also be replaced to ensure the wheel diameter is similar on opposite sides of the rail car. In an operation <NUM>, process <NUM> may include lowering the rail car back onto the track. Thus, unlike the process required to replace a conventional rail wheel in an in-board bearing configuration, replacing a tire <NUM> of a two-piece railroad wheel assembly <NUM> in an in-board bearing configuration does not require using a press machine, detaching the truck assembly from the rail car, or detaching the wheelset from the truck.

When used in an out-board bearing configuration, the process to replace tire <NUM> of two-piece railroad wheel assembly <NUM> also represents an improvement over the process to replace a conventional rail wheel in the same configuration. <FIG> illustrates an example of a process <NUM> for changing tire <NUM> of two-piece railroad wheel assembly <NUM> when utilized in an out-board bearing configuration, according to one or more aspects described herein. In an operation <NUM>, process <NUM> may include lifting the rail car high enough to detach the truck assembly from the rail car. In various embodiments, lifting the rail car high enough to detach the truck assembly may require moving the rail car to a maintenance facility and/or lifting the rail car using a crane or similar machine. In an operation <NUM>, process <NUM> may include removing the truck assembly from beneath the rail car and detaching the wheelset from the truck assembly. In some embodiments, detaching the wheelset from the truck assembly may require moving the truck assembly to a maintenance stand. In an operation <NUM>, process <NUM> may include unbolting tire <NUM> from center hub <NUM> and removing tire <NUM> from axle <NUM>. Unlike in an in-board bearing configuration, tire <NUM> cannot be removed from the axle <NUM> in an out-board bearing configuration without first removing the wheelset from the truck because the frame of the truck is outside the two-piece railroad wheel assembly <NUM> and would block removal of tire <NUM>. In an operation <NUM>, process <NUM> may include sliding a new tire <NUM> over the bearing and bolting the new tire <NUM> to center hub <NUM>. In various embodiments, the hardware used to affix the old tire <NUM> to the center hub <NUM> (e.g., the bolts <NUM>, nuts <NUM>, and/or bolt retainers <NUM>) may disposed of and new hardware may be used to affix the new tire <NUM> to center hub <NUM>. In an operation <NUM>, process <NUM> may include repeating operation <NUM> and operation <NUM> for the two-piece railroad wheel assembly <NUM> on the opposite side of axle <NUM>. In various embodiments, each time a tire <NUM> is replaced, the tire <NUM> of the two-piece railroad wheel assembly <NUM> on the opposite side of the wheelset (or axle <NUM>) must also be replaced to ensure the wheel diameter is similar on opposite sides of the rail car. In an operation <NUM>, process <NUM> may include reattaching the wheelset to the truck and replacing the truck assembly beneath the rail car. In an operation <NUM>, process <NUM> may include lowering the rail car back onto the track. Thus, unlike the process required to replace a conventional rail wheel in an out-board bearing configuration, replacing a tire <NUM> of a two-piece railroad wheel assembly <NUM> in an out-board bearing configuration does not require using a press machine or removing any other components of wheelset from axle <NUM> (including the bearings, brake discs, gearbox, grounding system, and/or any other components of the wheelset attached to axle <NUM>). As such, neither the axle nor any other components need to be tested or requalified, and no bearings need to be reconditioned or replaced when replacing tire <NUM> of two-piece railroad wheel assembly <NUM>.

Accordingly, in both in-board and out-board bearing configurations, two-piece railroad wheel assembly <NUM> represents an improvement over conventional rail wheels. Two-piece railroad wheel assembly <NUM> does not require special tools to remove or replace the wear surface on the wheel (i.e., tire <NUM>). Indeed, the large hydraulic press machine required to change a conventional rail wheel is not needed to change tire <NUM>. Two-piece railroad wheel assembly <NUM> also eliminates the need to remove certain components when removing and replacing tire <NUM>, including any components directly attached to axle <NUM>. As such, the risk of damage to axle <NUM> when replacing a wheel is reduced compared to common practices for replacing conventional interference press fit wheels. Indeed, when removing a conventional rail wheel, the axle itself is frequently gauged in the process, which often requires replacing the axle. By reducing the risk of damage to axle <NUM> and other components affixed to axle <NUM>, the two-piece railroad wheel assembly described herein reduces the number of scraped axles and other components, resulting in less steel consumed each time the wear surface of the wheel is renewed, which is good for the environment as it uses less energy to manufacture and machine. Also, as described above, if any components of a truck are removed from an axle (e.g., pressed on wheel, bearing, brake, or gearbox), the axle and bearings must be fully requalified per Association of American Railroads (AAR) requirements. For example, as provided above, AAR Manual of Standards and Recommended Practices, Section G-II, Sub-Section <NUM>. <NUM> currently states that if a journal bearing is removed from an axle for any reason, it must be sent for reconditioning or replaced with a new bearing. However, bearings have a performance life upwards of <NUM> times the life of a wheel. Thus, by allowing a wheel to be changed without having to recondition or replace bearings or other components, two-piece railroad wheel assembly <NUM> represent a significant operating cost advantage compared to prior art wheel designs by reducing labor cost, as well as by reducing the time the rail car spends out of service when replacing worn or damaged wheels.

Claim 1:
A rail wheel assembly (<NUM>) for a railway vehicle comprising:
a center wheel hub (<NUM>) attached to an axle (<NUM>) of a railway vehicle with an interference press fit, wherein the center wheel hub (<NUM>) includes an outward facing stepped interface (<NUM>) located at an outer edge of the center hub (<NUM>), the outward facing stepped interface (<NUM>) comprising a first set of holes (<NUM>); and
a tire (<NUM>) configured to engage a rail, wherein the tire (<NUM>) includes an inward facing stepped interface (<NUM>) located at an inner edge of the tire (<NUM>), the inward facing stepped interface (<NUM>) comprising a second set of holes (<NUM>);
wherein the outward facing stepped interface (<NUM>) of the center wheel hub (<NUM>) is configured to receive the inward facing stepped interface (<NUM>) of the tire (<NUM>),
wherein when the first set of holes (<NUM>) is aligned with the second set of holes (<NUM>), the first set of holes (<NUM>) and the second set of holes (<NUM>) are together configured to receive bolts (<NUM>) configured to secure the tire (<NUM>) to the center wheel hub (<NUM>), characterised in that,
the bolts (<NUM>) are configured to be inserted into the first set of holes (<NUM>) via an interior side of the outward facing stepped interface (<NUM>), wherein each bolt (<NUM>) is configured to be inserted into one of a set of bolt retaining plates (<NUM>) before being inserted into one of the first set of holes (<NUM>), wherein each bolt retaining plate (<NUM>) includes at least two holes configured to receive adjacent bolts (<NUM>), and
wherein the tire (<NUM>) is configured to be removed and replaced once secured to the center wheel hub (<NUM>) without requiring removal of any components affixed directly to the axle (<NUM>).