Patent Application
20100319567
The subject matter herein relates to locomotives, and, more particularly, to a system and method for modification of a baseline ballast arrangement of a locomotive.
A diesel-electric locomotive typically includes a diesel internal combustion engine coupled to drive a rotor of at least one traction alternator to produce alternating current (AC) electrical power. The traction alternator may be electrically coupled to power one or more electric traction motors mechanically coupled to apply torque to one or more axles of the locomotive. The traction motors may include AC motors operable with AC power, or direct current motors operable with direct current (DC) power. For DC motor operation, a rectifier may be provided to convert the AC power produced by the traction alternator to DC power for powering the DC motors.
AC-motor-equipped locomotives typically exhibit better performance and have higher reliability and lower maintenance than DC-motor-equipped locomotives. In addition, more responsive individual motor control may be provided in AC-motor-equipped locomotives, for example, via use of inverter-based motor control. However, DC-motor-equipped locomotives are relatively less expensive than comparable AC-motor-equipped locomotives. Thus, for certain hauling applications, such as when hauling relatively light freight and/or relatively short trains, it may be more cost efficient to use a DC-motor-equipped locomotive instead of an AC-motor-equipped locomotive.
For relatively heavy hauling applications, diesel-electric locomotives are typically configured to have two trucks including three powered axles per truck. Each axle of the truck is typically coupled, via a gear set, to a respective motor mounted in the truck near the axle. Each axle is mounted to the truck via a suspension assembly that typically includes one or more springs for transferring a respective portion of a locomotive weight (including a locomotive body weight and a locomotive truck weight) to the axle while allowing some degree of movement of the axle relative to the truck.
A locomotive body weight is typically configured to be about equally distributed between the two trucks. The locomotive weight is usually further configured to be symmetrically distributed among the axles of the trucks. For example, a conventional locomotive weighing 420,000 pounds is typically configured to equally distribute weight to the six axles of the locomotive, so that each axle supports a force of 420,000/6 pounds per axle, or 70,000 pounds per axle.
Locomotives are typically manufactured to distribute weight symmetrically to the trucks and then to the axles of the trucks so that relatively equal portions of the weight of the locomotive are distributed to the axles. Typically, the weight of the locomotive and the power rating of the locomotive determine a tractive effort capability rating of the locomotive that may be expressed as weight times a tractive effort rating. Accordingly, the weight applied to each of the axles times the tractive effort that can be applied to the axle determines a power capability of the corresponding axle. Consequently, the heavier a locomotive, the more tractive effort that it can generate at a certain speed. Additional weight, or ballast, may be added to a locomotive to bring it up to a desired overall weight for achieving a desired tractive effort capability rating. For example, due to manufacturing tolerances that may result in varying overall weights among locomotives built to a same specification, locomotives are commonly configured to be slightly lighter than required to meet a desired tractive effort rating, and then ballast is added to reach a desired overall weight capable of meeting the desired tractive effort rating.
Diesel engine powered locomotives represent a major capital expenditure for railroads, including both the initial purchase of a locomotive, but also the ongoing expense of maintaining and repairing the locomotive. In addition, hauling requirements may change over time for the railroad, so that a locomotive having a certain operating capability at a time of purchase may not meet the hauling needs of the railroad in the future. For example, a railroad looking to purchase a locomotive may only have minimal hauling needs that may be met by a relatively inexpensive low tractive effort capability locomotive, such as a DC powered locomotive having less hauling capability compared to a more expensive relatively high tractive effort locomotive, such as an AC powered locomotive. However, at some point in the useful life of the low tractive effort capability locomotive, hauling needs of the railroad may change, such that the low tractive effort capability locomotive may not be able to provide sufficient hauling capability. As a result, the railroad may need to purchase a more capable high tractive effort capability locomotive, thereby sacrificing a remaining useful life of the low tractive effort capability locomotive.
The inventors have recognized that by manufacturing one type of an item, instead of various different types of the item, a manufacturer may be able to reduce manufacturing costs by streamlining production lines. For example, a locomotive manufacturer may be able to reduce manufacturing costs by producing a single type of locomotive, such as a high tractive effort capability AC powered locomotive, instead of producing two types of locomotives, such as a high tractive effort capability AC powered locomotive and a low tractive effort capability DC powered locomotive. Thus, what is needed is a locomotive that, for example, may be easily reconfigured as operating requirements for the locomotive change over its life. There is also a continuing need to reduce manufacturing and equipment costs. Accordingly, the inventors have innovatively developed a reconfigurable locomotive that may be ballasted using less weight than typically required and may allow for elimination of a need for costly ballast altogether.
An example embodiment of the invention includes a system for modification of a baseline ballast arrangement of a locomotive (or other rail vehicle) having an overall tractive effort rating based on symmetrical distribution of weight and driving torque applied by the locomotive to the respective axles of the locomotive. The system includes a locomotive truck comprising a first axle and a second axle, the first axle of the truck uncoupled from a traction system of the locomotive, and the second axle of the truck coupled to the traction system of the locomotive, a first suspension assembly coupling the first axle to the truck configured to apply to the first axle a first portion of a locomotive weight; and a second suspension assembly coupling the second axle to the truck configured to apply to the second axle a second portion of the locomotive weight different from the first portion of the locomotive weight applied to the first axle so that the locomotive weight is asymmetrically distributed to the first axle and the second axle. The asymmetrical distribution is configured to allocate more weight to the second axle to transmit a corresponding incremental amount of tractive effort for a given amount of a driving torque applied to the second axle via the traction system of the locomotive, and further wherein an amount of locomotive weight allocated from the first axle to the second axle allows modification of a baseline ballast arrangement by reducing an amount of ballast in the baseline ballast arrangement corresponding to the amount of weight allocated from the first axle to the second axle. The first axle and the second axle comprise axles having substantially equal weight-carrying capability.
In another example embodiment, the invention includes a locomotive (or other rail vehicle) truck comprising a first axle, a second axle, and a third axle, the first axle of the truck uncoupled from a traction system of the locomotive, and the second axle and the third axle of the truck coupled to the traction system of the locomotive, a first suspension assembly coupling the first axle to the truck configured to apply to the first axle a first portion of a locomotive weight, a second suspension assembly coupling the second axle to the truck configured to apply to the second axle a second portion of the locomotive weight, and a third axle of the locomotive truck coupled to the traction system of the locomotive. The first axle, the second axle and the third axle comprise axles having substantially equal weight-carrying capability. The system also includes a third suspension assembly coupling the third axle to the truck configured to apply to the third axle a third portion of the locomotive weight; the second portion of the locomotive weight and the third portion of the locomotive weight applied to the respective second axle and third axle different from the first portion of the locomotive weight applied to the first axle so that the locomotive weight is asymmetrically distributed to the first axle, the second axle, and the third axle, wherein the asymmetrical distribution is configured to allocate more weight to the second axle and the third axle to transmit corresponding incremental amounts of tractive effort for a given amount of a driving torque applied to the second axle and the third axle via the traction system of the locomotive, and further wherein an amount of locomotive weight allocated from the first axle to the second axle and the third axle allows modification of a baseline ballast arrangement by reducing an amount of ballast in the baseline ballast arrangement corresponding to the amount of locomotive weight allocated from the first axle to the second axle and the third axle.
In another example embodiment, the invention includes a method for modification of a baseline ballast arrangement of a locomotive (or other rail vehicle) having an overall tractive effort rating based on symmetrical distribution of weight and driving torque applied by the locomotive to the respective axles of the locomotive. The method includes providing a locomotive truck comprising a first axle and a second axle, the first axle of the truck uncoupled from a traction system of the locomotive, and the second axle of the truck coupled to the traction system of the locomotive and coupling the first axle to the truck with a first suspension assembly configured to apply to the first axle a first portion of a locomotive weight. The method also includes uncoupling a first axle of the locomotive truck from a traction system of the locomotive and coupling the first axle to the truck with a first suspension assembly configured to apply to the first axle a first portion of a locomotive weight. The method also includes coupling the second axle to the truck with a second suspension assembly configured to apply to the second axle a second portion of the locomotive weight different from the first portion of the locomotive weight being applied to the first axle, so that the locomotive weight is asymmetrically distributed to the first axle and the second axle, wherein the asymmetrical distribution is configured to allocate more weight to the second axle to transmit a corresponding incremental amount of tractive effort for a given amount of a driving torque applied to the second axle via the traction system of the locomotive. The first axle and the second axle are chosen to have substantially equal weight-carrying capability. The method further includes modifying a baseline ballast arrangement of the locomotive by reducing an amount of ballast in the baseline ballast arrangement corresponding to an amount of weight allocated from the first axle to the second axle.
A more particular description of the invention briefly described above will be rendered by reference to specific embodiments thereof that are illustrated in the appended drawings. These drawings depict only typical embodiments of the invention and are not therefore to be considered to be limiting of its scope.
Reference will now be made in detail to the embodiments consistent with the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numerals are used throughout the drawings and refer to the same or like parts.
A static weight 30 of the locomotive 10, for example, including a locomotive body weight 31 and truck weights 32a, 32b, is supported by the axles 38a-38f of the trucks 26a-26b. Accordingly, the static weight 30 supported by any one axle may include a portion of the locomotive body weight 31 of the locomotive 10 supported by the truck to which the axle is coupled and the truck weight, e.g., truck weight 32a, 32b. The axles 38a-38f may be coupled to the trucks by 26a, 26b one or more suspension assemblies 40a-40f that may include one or more springs 42a-42f and/or shims 44a, 44b.
In an embodiment, each of the axles of the trucks has substantially the same weight/normal force capability. This means that all the axles have substantially equal weight-carrying capability, meaning equal but for standard manufacturing tolerances or nominal deviations, as will be readily understood by one skilled in the art. It will be appreciated that the total axle weight has both static and dynamic components, which in one example embodiment may combine to yield values on the order of approximately 120% of a nominal static weight. It will be appreciated that the magnitude of the static weight distribution achieved in accordance with aspects of the present invention will not require any structural modifications for the axles of the truck to accommodate the magnitude of the static weight distribution. This means that the axles are structurally the same, subject to standard manufacturing tolerances or nominal deviations, as will be readily understood by one skilled in the art.
In an aspect of the invention, one or more axles of trucks 26a, 26b, such as axles 38e, 38f, may be left un-powered in a baseline configuration. Consequently, the associated assemblies normally deployed with the un-powered axles, such as inverters, traction motors, and/or gear sets, may be absent in a baseline configuration. By reducing a number of traction components, users requiring a less tractive effort capable and/or less powerful locomotive may be able to save on the cost of purchasing such a locomotive compared to a locomotive having a full complement of traction components. Furthermore, manufacturers of such locomotives may save on production costs because they only need to produce one baseline locomotive design and simply add traction components and/or refrain for installing traction components to achieve a desired capability of a locomotive, instead of having to produce entirely different models having different capabilities. Spaces in the locomotive 10 normally occupied by components of the traction system 11, such as a space 41a in the truck 26a normally reserved for housing a traction assembly, and or a space 21a in the motor controller 20, normally reserved for an inverter, may be left vacant in a baseline locomotive design.
In an example embodiment, the invention includes a system for modification of a baseline ballast arrangement of a locomotive 10. The locomotive 10 may have an overall tractive effort rating based on symmetrical distribution of weight and driving torque applied by the locomotive 10 to the respective axles 38a-38f of the locomotive 10. The system includes a locomotive truck, e.g. truck 26a, for distributing weight asymmetrically to axles, e.g. a first axle 38a and a second axle 38e, of the truck 26a. Axle 38e of a locomotive truck 26a may be uncoupled from the traction system 11 of the locomotive 10 and a suspension assembly 40e may couple axle 38e to the truck 26a configured to apply to axle 38e a first portion 34b of the weight 30 of the locomotive 10. Accordingly, axle 38e may be configured to act as an un-powered, idler axle that functions to support portion 34b of the locomotive weight 30 in the absence of the traction system components normally needed to drive the axle 38e. Axle 38a of the locomotive truck 26a may be coupled to the traction system 11, and a suspension assembly 40a may couple the axle 38a to the truck 26a configured to apply to the axle 38a a second portion 34a of the weight 30. Portion 34b may be different from portion 34a of the weight 30 being applied to the axle 38a so that the locomotive weight 30 is asymmetrically distributed to axle 38e and axle 38a. Advantageously, this asymmetrical distribution of weight may be configured to allocate more weight to axle 38a effective to allow to transmit a corresponding incremental amount of tractive effort for a given amount of a driving torque applied to the axle 38a via the traction system 11 of the locomotive 10. Furthermore, an amount of weight allocated from axle 38e to axle 38a allows modification of a baseline ballast arrangement by reducing an amount of ballast in the baseline ballast arrangement corresponding to the amount of weight allocated from axle 38e to axle 38a.
By way of explanation, a ballasted locomotive weighing 420,000 pounds may typically be configured to equally distribute weight to six axles 38a-38f so that each axle 38a-38f supports a weight 34a-34f of 420,000/6 pounds per axle, or 70,000 pounds per axle. However, if two of the axles 38e, 38f are left un-powered as shown in the locomotive 10 of
Accordingly, in an embodiment of the invention depicted in
In an example embodiment for distributing weight asymmetrically to reduce a ballast requirement, suspension assembly 40a and suspension assembly 40e may comprise respective springs 42a, 42b having different characteristics that provided different weight loading responses. For example, the different characteristics may comprise different spring constants and/or different spring geometries. For example, spring 42a may comprise a stiffer spring constant than a spring constant of spring 42e. In another embodiment, the different spring geometry may include a different spring length in a direction of spring compression. For example, a length of spring 42a may be longer than a length of spring 42e. In another embodiment, suspension assembly 40a and suspension assembly 40e may include respective springs 42a, 42b having equivalent characteristics, wherein at least one of the suspension assembly 40a and suspension assembly 40e include a shim, e.g. shim 44a, for configuring the corresponding suspension assembly e.g. 42 to have a different characteristic than the other suspension assembly, e.g. 40e. For example, shim 44a may effectively shorten, or pre-compress, spring 42a so that more weight is allocated to axle 38a compared to an un-shimmed suspension assembly 40e including a spring 42e having an equivalent characteristic as spring 42a.
In yet another embodiment shown in
The examples below represent asymmetrical axle weight distribution in accordance with aspects of the present invention, where the values are listed in a descending numerical order regarding the magnitude of asymmetrical axle weight distribution. In a first example, the asymmetrical axle weight distribution may be represented by the following weight axle ratios, 74/60/74. It is believed that the ratios of the first example may approximate an upper bound that takes into account various considerations regarding the extent to which static weight can be practically shifted to the powered axles. These considerations may include rail forces, the impact on friction braking related wheel to rail adhesion required to avoid slides, as well as truck component stress.
In a second example, the asymmetrical axle weight distribution may be represented by the following weight axle ratios, 72/64/72. In a third example, the normalized asymmetrical axle weight distribution may be represented by the following weight axle ratios 70/68/70. It is believed that the distribution values of the third example may approximate a lower bound regarding static weight shifting of practical utility. It will be appreciated that the foregoing values (upon rounding) correspond to an example range from approximately 55%145% weight distribution to approximately 51%/49% distribution, where a second axle coupled to the traction system carries the larger percentage relative to a first axle uncoupled from the traction system. It will be appreciated that the foregoing values (upon rounding) in a three-way percentage distribution correspond to a range from approximately 33.6%, 32.7%, 33.6% to approximately 35.5%, 29.0%, 35.5%, where a second axle and a third axle coupled to the traction system carry the larger percentage values relative to a first axle uncoupled from the traction system, and where the first axle is positioned between the second and the third axles. The first axle comprises an axle similar in capacity to the second and third axles. For example, in the event the locomotive were to be reconfigured so that the first axle is coupled to the traction system of the locomotive, the first axle can accept and withstand tractive effort from the traction system of the locomotive.
In view of the foregoing considerations, it will be appreciated that the weight distribution achieved in accordance with aspects of the present invention represents a relatively slight weight distribution compared to a nominal weight normally carried by the axles, and as noted above, this means that all the axles have the same weight-carrying capability, subject to manufacturing tolerances or nominal deviations, as will be understood by one skilled in the art.
In another embodiment, suspension assemblies 40a, 40e and 40b, include respective springs 42a, 42e and 42b having different characteristics. The different characteristics may include different spring constants and/or different characteristics comprise different spring geometries. In another example embodiment, springs 42a, 42e and 42b may include equivalent characteristics, wherein at least one of the first suspension assemblies 40a, 40e and 40b include a shim, such as shim s 44a, 44b for configuring the corresponding suspension assembly to have a different characteristic than the other suspension assemblies.
In another example embodiment depicted in the flow diagram 48 of
The method may also include coupling 54 the axle 38a to the truck 26a with a second suspension assembly 40a configured to apply to axle 38a portion 34a of the locomotive weight 30 different from portion 34b of the locomotive weight 30 being applied to axle 38e so that the locomotive weight 30 is asymmetrically distributed to axle 38e and axle 38a. The asymmetrical distribution may be configured to allocate more of the locomotive weight to axle 38a to transmit a corresponding incremental amount of tractive effort for a given amount of a driving torque applied to axle 38a via the traction system 11 of the locomotive 10. The method may further include modifying 56 a baseline ballast arrangement of the locomotive 10 by reducing an amount of ballast e.g. 46, in the baseline ballast arrangement corresponding to an amount of locomotive weight allocated from the axle 38e to axle 38a. The method may also include coupling 58 a third axle, e.g. axle 38b of the locomotive truck 26a to the traction system 11 of the locomotive 10 and coupling 60 axle 38b to the truck 26a with a third suspension assembly configured to apply to axle 38b a third portion 34c of the weight 30 different from the first portion 34b of the weight 30 being applied to axle 38e.
While exemplary embodiments of the invention have been described with reference to an exemplary embodiment, it will be understood by those skilled in the art that various changes, omissions and/or additions may be made and equivalents may be substituted for elements thereof without departing from the spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.
This application is a continuation-in-part (CIP) application of U.S. patent application Ser. No. 11/833,858, filed on Aug. 3, 2007, which is herein incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11833858 | Aug 2007 | US |
| Child | 12869083 | US |
