Train wheel: Difference between revisions
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[[File:Flanged wheel.jpg|thumb|[[Flange]]d railway wheel]] |
[[File:Flanged wheel.jpg|thumb|[[Flange]]d railway wheel]] |
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[[File:Rollingstock axle.jpg|thumb|250px|Railroad car wheels are affixed to a straight axle, such that both wheels rotate in unison. This is called a [[Wheelset (rail transport)|wheelset]].]] |
[[File:Rollingstock axle.jpg|thumb|250px|Railroad car wheels are affixed to a straight axle, such that both wheels rotate in unison. This is called a [[Wheelset (rail transport)|wheelset]].]] |
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A '''train wheel''' or '''rail wheel''' is a type of [[wheel]] specially designed for use on [[Track (rail transport)|railway track]]s. A rolling component is typically pushed onto an [[axle]] and mounted directly on a [[Railroad car|railway carriage]] or [[locomotive]], or indirectly on a [[bogie]] (in the UK), also called a ''truck'' (in North America). Wheels are [[casting|cast]] or [[forging|forged]] and are heat-treated to have a specific hardness. New wheels are trued, using a [[lathe]], to a specific profile before being pressed onto an axle. All |
A '''train wheel''' or '''rail wheel''' is a type of [[wheel]] specially designed for use on [[Track (rail transport)|railway track]]s. A rolling component is typically pushed onto an [[axle]] and mounted directly on a [[Railroad car|railway carriage]] or [[locomotive]], or indirectly on a [[bogie]] (in the UK), also called a ''truck'' (in North America). Wheels are [[casting|cast]] or [[forging|forged]] and are heat-treated to have a specific hardness. New wheels are trued, using a [[lathe]], to a specific profile before being pressed onto an axle. All wheel profiles must be regularly checked to ensure proper [[wheel-rail interface|interaction between the wheel and the rail]]. Incorrectly trued, or worn out wheels increase [[rolling resistance]], reduce [[energy efficiency in transport|energy efficiency]] and may even cause a [[derailment]]. A railroad wheel typically consists of two main parts: the wheel itself, and the [[tire]] (or ''tyre'' in [[British English]]) around the outside. A rail tire is usually made from [[steel]], and is typically heated and pushed onto the wheel, where it remains firmly as it shrinks and cools. Monobloc wheels do not have encircling tires, while ''resilient rail wheels'' have a resilient material, such as [[rubber]], between the wheel and tire. |
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==Wheel geometry and flange== |
==Wheel geometry and flange== |
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==Wheels for road-rail vehicles== |
==Wheels for road-rail vehicles== |
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[[File: |
[[File:Land cruiser hyrail conversion.jpg|thumb|The small rail wheels fitted to road-rail vehicles allow them to be stored away when the vehicle is in road-going mode.]] |
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Wheels used for [[road-rail vehicle]]s are normally smaller than those found on other types of rolling stock (such as locomotives or carriages). This is because the wheel has to be stored clear of the ground when the vehicle is in road-going mode - Such wheels can be as small as {{convert|245|mm|in|2|abbr=on |
Wheels used for [[road-rail vehicle]]s are normally smaller than those found on other types of rolling stock (such as locomotives or carriages). This is because the wheel has to be stored clear of the ground when the vehicle is in road-going mode - Such wheels can be as small as {{convert|245|mm|in|2|abbr=on}} in diameter. In Australia, wheels for [[road-rail vehicle]]s should comply with the requirements of AS7514.4, which is the standard for infrastructure maintenance vehicle wheels. |
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==Tire== |
==Tire== |
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{{main|Railway tire}} |
{{main|Railway tire}} |
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The wheels of many rail vehicles, especially steam locomotives and older types of rolling stock are fitted with steel [[tire]]s (or |
The wheels of many rail vehicles, especially steam locomotives and older types of rolling stock, are fitted with steel [[tire]]s (or tyres in [[British English]], [[Australian English]] and others) to provide a replaceable wearing element on a costly wheel. |
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==Tire installation== |
==Tire installation== |
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[[Image: |
[[Image:Jack Delano - Retiring a locomotive driver wheel, Shopton, Iowa.jpg|thumb|250px|Steel tire on a [[steam locomotive]]'s driving wheel is heated with gas flames to expand and loosen it so it may be slipped over the wheel.]] |
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Replacing a whole wheel because of a worn contact surface is expensive, so older types of railway wheels were fitted with replaceable steel tires. The tire is a hoop of steel that is fitted around the steel wheel |
Replacing a whole wheel because of a worn contact surface is expensive, so older types of railway wheels were fitted with replaceable steel tires. The tire is a hoop of steel that is fitted around the steel wheel centre. The tire is machined with a shoulder on its outer face to locate it on the wheel centre, and a groove on the inside diameter of the flange face. |
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The inside diameter of the tire is machined to be slightly less than the diameter of the wheel |
The inside diameter of the tire is machined to be slightly less than the diameter of the wheel centre on which it is mounted, to give an interference fit. |
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The tire is fitted by heating to a controlled temperature, avoiding overheating. This causes the tire to expand. The wheel |
The tire is fitted by heating to a controlled temperature, avoiding overheating. This causes the tire to expand. The wheel centre, usually already mounted on the axle, is lowered into the tire which is flange-side-up. The tire cools, and the retaining ring (a shaped steel bar rolled into a hoop) is fitted into the groove. Hydraulically operated rolls [[swage]] the groove down onto the retaining ring. |
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The tire is primarily held in place by its [[interference fit]]. The shoulder on the outside and the retaining ring also keep the tire in place if the interference fit is lost. This is most often due to severe drag braking down a gradient, or due to an error in the machining. |
The tire is primarily held in place by its [[interference fit]]. The shoulder on the outside and the retaining ring also keep the tire in place if the interference fit is lost. This is most often due to severe drag braking down a gradient, or due to an error in the machining. |
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Removal of a worn tire is by machining out the retaining ring and heating the tire to relax the interference fit. |
Removal of a worn tire is by machining out the retaining ring and heating the tire to relax the interference fit. |
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Some steam locomotive wheels had tires bolted through the rim, or with a second smaller shoulder machined on the inside face of the tire. This shoulder was severely limited in size as it had to pass over the wheel |
Some steam locomotive wheels had tires bolted through the rim, or with a second smaller shoulder machined on the inside face of the tire. This shoulder was severely limited in size as it had to pass over the wheel centre for assembly. |
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Tires of different designs were fitted to wheels with wooden centers ([[Mansell wheel]]s in the UK) and to various other types. |
Tires of different designs were fitted to wheels with wooden centers ([[Mansell wheel]]s in the UK) and to various other types. |
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The use of tires is becoming obsolete. The |
The use of tires is becoming obsolete. The utilisation of traditional freight wagons was often so low that tires never needed renewal, so it was cheaper to fit a one-piece ("monoblock") wheel. Monoblock wheels are lighter and offer better integrity as there is no tire to come loose. Modern flow-line repair lines are disrupted by the inspection of the wheel centre once the tire is removed, possibly generating extra rectification work, and the need to make each tire fit its allocated wheel centre. Monoblock wheels are now more economical. |
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==Causes of damage== |
==Causes of damage== |
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The most usual cause of damage is drag braking on severe gradients. Because the brake blocks apply directly on the tire, it is heated up, relaxing the interference fit. It is not feasible to fit the tire with such a heavy interference as to eliminate this risk entirely, and the retaining ring will ensure that the tire can only rotate on the wheel center, maintaining its alignment. In rare instances |
The most usual cause of damage is drag braking on severe gradients. Because the brake blocks apply directly on the tire, it is heated up, relaxing the interference fit. It is not feasible to fit the tire with such a heavy interference as to eliminate this risk entirely, and the retaining ring will ensure that the tire can only rotate on the wheel center, maintaining its alignment. In rare instances the rotation could be so severe as to wear the retaining ring down till it breaks, which could result in derailment. |
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Severe braking or low adhesion may stop the rotation of the wheels while the vehicle is still moving, which can cause a [[flat spot]] on the tire and localized heat damage to the tire material. |
Severe braking or low adhesion may stop the rotation of the wheels while the vehicle is still moving, which can cause a [[flat spot]] on the tire and localized heat damage to the tire material. |
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Revision as of 20:33, 28 April 2020
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A train wheel or rail wheel is a type of wheel specially designed for use on railway tracks. A rolling component is typically pushed onto an axle and mounted directly on a railway carriage or locomotive, or indirectly on a bogie (in the UK), also called a truck (in North America). Wheels are cast or forged and are heat-treated to have a specific hardness. New wheels are trued, using a lathe, to a specific profile before being pressed onto an axle. All wheel profiles must be regularly checked to ensure proper interaction between the wheel and the rail. Incorrectly trued, or worn out wheels increase rolling resistance, reduce energy efficiency and may even cause a derailment. A railroad wheel typically consists of two main parts: the wheel itself, and the tire (or tyre in British English) around the outside. A rail tire is usually made from steel, and is typically heated and pushed onto the wheel, where it remains firmly as it shrinks and cools. Monobloc wheels do not have encircling tires, while resilient rail wheels have a resilient material, such as rubber, between the wheel and tire.
Wheel geometry and flange
Tram wheel flange (right)
Most train wheels have a conical geometry, which is the primary means of keeping the train's motion aligned with the track.[1] Train wheels have a flange on one side to keep the wheels, and hence the train, running on the rails when the limits of the geometry-based alignment are reached, e.g. due to some emergency or defect. See Hunting oscillation. Some wheels have a cylindrical geometry, where flanges are essential to keep the train on the rail track.
Wheel arrangement
Wheels for road-rail vehicles
Wheels used for road-rail vehicles are normally smaller than those found on other types of rolling stock (such as locomotives or carriages). This is because the wheel has to be stored clear of the ground when the vehicle is in road-going mode - Such wheels can be as small as 245 mm (9.65 in) in diameter. In Australia, wheels for road-rail vehicles should comply with the requirements of AS7514.4, which is the standard for infrastructure maintenance vehicle wheels.
Tire
The wheels of many rail vehicles, especially steam locomotives and older types of rolling stock, are fitted with steel tires (or tyres in British English, Australian English and others) to provide a replaceable wearing element on a costly wheel.
Tire installation
Replacing a whole wheel because of a worn contact surface is expensive, so older types of railway wheels were fitted with replaceable steel tires. The tire is a hoop of steel that is fitted around the steel wheel centre. The tire is machined with a shoulder on its outer face to locate it on the wheel centre, and a groove on the inside diameter of the flange face. The inside diameter of the tire is machined to be slightly less than the diameter of the wheel centre on which it is mounted, to give an interference fit.
The tire is fitted by heating to a controlled temperature, avoiding overheating. This causes the tire to expand. The wheel centre, usually already mounted on the axle, is lowered into the tire which is flange-side-up. The tire cools, and the retaining ring (a shaped steel bar rolled into a hoop) is fitted into the groove. Hydraulically operated rolls swage the groove down onto the retaining ring.
The tire is primarily held in place by its interference fit. The shoulder on the outside and the retaining ring also keep the tire in place if the interference fit is lost. This is most often due to severe drag braking down a gradient, or due to an error in the machining.
Removal of a worn tire is by machining out the retaining ring and heating the tire to relax the interference fit.
Some steam locomotive wheels had tires bolted through the rim, or with a second smaller shoulder machined on the inside face of the tire. This shoulder was severely limited in size as it had to pass over the wheel centre for assembly.
Tires of different designs were fitted to wheels with wooden centers (Mansell wheels in the UK) and to various other types.
The use of tires is becoming obsolete. The utilisation of traditional freight wagons was often so low that tires never needed renewal, so it was cheaper to fit a one-piece ("monoblock") wheel. Monoblock wheels are lighter and offer better integrity as there is no tire to come loose. Modern flow-line repair lines are disrupted by the inspection of the wheel centre once the tire is removed, possibly generating extra rectification work, and the need to make each tire fit its allocated wheel centre. Monoblock wheels are now more economical.
Causes of damage
The most usual cause of damage is drag braking on severe gradients. Because the brake blocks apply directly on the tire, it is heated up, relaxing the interference fit. It is not feasible to fit the tire with such a heavy interference as to eliminate this risk entirely, and the retaining ring will ensure that the tire can only rotate on the wheel center, maintaining its alignment. In rare instances the rotation could be so severe as to wear the retaining ring down till it breaks, which could result in derailment.
Severe braking or low adhesion may stop the rotation of the wheels while the vehicle is still moving, which can cause a flat spot on the tire and localized heat damage to the tire material.
Tires are reasonably thick, about 3 inches (76 mm), giving plenty of room for wear. Worn tires or tires with flats are re-profiled on a wheel lathe if there is sufficient thickness of material remaining.
See also
References
- ^ Liszewski, Andrew (15 March 2017). "The Reason Trains Have Angled Wheels Is Incredibly Clever". Gizmodo. Retrieved 14 March 2017.
ISO 1005 Parts 1-9 BS 5892 Parts 1-6 AS7414.4
External links
- "APTA PR-CS-RP-003-98 Recommended Practice for Developing a Clearance Diagram for Passenger Equipment 5.3.2.1 Design tolerances" (PDF). APTA.com. American Public Transportation Association. 1998-03-26. Retrieved 2015-01-17.
- Train wheels