Posted by wanswheel on Monday, August 29, Durant announced, one year ago, that he wanted one million of cross ties for immediate use, and three millions in two years, everybody laughed at the idea. Soon one party agreed to furnish a large lot, and another a lot, but they were bringing in cotton-wood, a species of timber like unto a pumpkin or a cucumber, which looked well enough, but had a reputation for not being reliable over night; but the resources of man are as endless as his desires are boundless. To make the latter available, an iron boiler a hundred feet long and five feet in diameter was brought into requisition.
Traditional track structure[ edit ] Railway track new showing traditional features of ballast, part of sleeper and fixing mechanisms Section through railway track and foundation showing the ballast and formation layers.
The layers are slightly sloped to help drainage. Sometimes there is a layer of rubber matting not shown to improve drainage, and to dampen sound and vibration. Notwithstanding modern technical developments, the overwhelmingly dominant track form worldwide consists of flat-bottom steel rails supported on timber or pre-stressed concrete sleepers, which are themselves laid on crushed stone ballast.
Most railroads with heavy traffic utilize continuously welded rails supported by sleepers attached via base plates that spread the load. A plastic or rubber pad is usually placed between the rail and the tie plate where concrete sleepers are used. The rail is usually held down to the sleeper with resilient fastenings, although cut spikes are widely used in North American practice.
For much of the 20th century, rail track used softwood timber sleepers and jointed rails, and a considerable extent of this track type remains on secondary and tertiary routes.
The rails were typically of flat bottom section fastened to the sleepers with dog spikes through a flat tie plate in North America and Australia, and typically of bullhead section carried in cast iron chairs in British and Irish practice. The London, Midland and Scottish Railway pioneered the conversion to flat-bottomed rail and the supposed advantage of bullhead rail - that the rail could be turned over and re-used when the top surface had become worn - turned out to be unworkable in practice because the underside was usually ruined by fretting from the chairs.
Jointed rails were used at first because contemporary technology did not offer any alternative. However, the intrinsic weakness in resisting vertical loading results in the ballast becoming depressed and a heavy maintenance workload is imposed to prevent unacceptable geometrical defects at the joints.
The joints also needed to be lubricated, and wear at the fishplate joint bar mating surfaces needed to be rectified by shimming. For this reason jointed track is not financially appropriate for heavily operated railroads.
Timber sleepers are of many available timbers, and are often treated with creosotecopper-chrome-arsenateor other wood preservative. Pre-stressed concrete sleepers are often used where timber is scarce and where tonnage or speeds are high.
Steel is used in some applications. The track ballast is customarily crushed stone, and the purpose of this is to support the sleepers and allow some adjustment of their position, while allowing free drainage.
Track of Singapore LRT Ballastless high-speed track in China A disadvantage of traditional track structures is the heavy demand for maintenance, particularly surfacing tamping and lining to restore the desired track geometry and smoothness of vehicle running.
Weakness of the subgrade and drainage deficiencies also lead to heavy maintenance costs.
This can be overcome by using ballastless track. In its simplest form this consists of a continuous slab of concrete like a highway structure with the rails supported directly on its upper surface using a resilient pad.
There are a number of proprietary systems, and variations include a continuous reinforced concrete slab, or alternatively the use of pre-cast pre-stressed concrete units laid on a base layer.
Many permutations of design have been put forward. However, ballastless track has a high initial cost, and in the case of existing railroads the upgrade to such requires closure of the route for a long period. Its whole-life cost can be lower because of the reduction in maintenance. Ballastless track is usually considered for new very high speed or very high loading routes, in short extensions that require additional strength e.
Some rubber-tyred metros use ballastless tracks. Ladder track utilizes sleepers aligned along the same direction as the rails with rung-like gauge restraining cross members.
Both ballasted and ballastless types exist. Rail[ edit ] Cross-sections of flat-bottomed railwhich can rest directly on the sleepers, and bullhead rail which sits in a chair not shown Main article: Rail profile Modern track typically uses hot-rolled steel with a profile of an asymmetrical rounded I-beam.
It took many decades to improve the quality of the materials, including the change from iron to steel.
The stronger the rails and the rest of the trackwork, the heavier and faster the trains the track can carry. Other profiles of rail include: According to the Railway Gazette the planned-but-cancelled kilometre rail line for the Baffinland Iron Mineon Baffin Islandwould have used older carbon steel alloys for its rails, instead of more modern, higher performance alloys, because modern alloy rails can become brittle at very low temperatures.
Hardwood such as jarrah and karri were better than softwoods such as fir. Early North American railroads used iron on top of wooden rails as an economy measure but gave up this method of construction after the iron came loose, began to curl and went into the floors of the coaches.
The iron strap rail coming through the floors of the coaches came to be referred to as "snake heads" by early railroaders. Speed limits in the United States rail Rail is graded by weight over a standard length.
Heavier rail can support greater axle loads and higher train speeds without sustaining damage than lighter rail, but at a greater cost.
The United Kingdom is in the process of transition from the imperial to metric rating of rail. The traditional method of joining the rails is to bolt them together using metal fishplates jointbars in the USproducing jointed track.
For more modern usage, particularly where higher speeds are required, the lengths of rail may be welded together to form continuous welded rail CWR.Nothing Like It in the World gives the account of an unprecedented feat of engineering, vision, and courage.
It is the story of the men who built the transcontinental railroad—the investors who risked their businesses and money; the enlightened politicians who understood its importance; the /5.
The Historical Guide to North American Railroads: Lines Abandoned or Merged Since by George H. Drury In the past seven decades the American railroad industry has undergone sweeping changes including a bewildering sucession of mergers.
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A comparison of North American and European railway systems – a critique and riposte Phil Mortimer & Dewan Md Zahurul Islam North American carload and carload blocks these are manip- There is no men-tion of what North America may learn from Europe in the Clausen and Voll  paper.
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