AREA recommendations reduced the relative weight of rail head down to 36%, while alternative profiles reduced head weight to 33% in heavier weight rails. Disadvantages of the narrower foot were overcome through use of tie plates. The trend was to increase rail height/foot-width ratio and strengthen the web. In 1909, the American Railway Association (or ARA) specified standard profiles for 10 lb/yd (4.96 kg/m) increments from 60 to 100 lb/yd (29.8 to 49.6 kg/m). ASCE 90 lb/yd (44.6 kg/m) profile was adequate but heavier weights were less satisfactory. Height of rail equaled width of foot for each ASCE tee-rail weight and the profiles specified fixed proportion of weight in head, web and foot of 42%, 21% and 37%, respectively. The American Society of Civil Engineers (or ASCE) specified rail profiles in 1893 for 5 lb/yd (2.5 kg/m) increments from 40 to 100 lb/yd (19.8 to 49.6 kg/m). New York Central System Dudley 127 lb/yd (63.0 kg/m) rail cross section Thermally hardened 75 kg/m (151 lb/yd) rails also have been used on heavy-duty railroads like Baikal–Amur Mainline, but have proven themselves deficient in operation and were mainly rejected in favor of 65 kg/m (131 lb/yd) rails. In the countries of former USSR 65 kg/m (131 lb/yd) rails and 75 kg/m (151 lb/yd) rails (not thermally hardened) are common. Rails are made in a large number of different sizes. (More specifically 1 kg/m = 2.0159 lb/yd.)Ĭommonly, in rail terminology pound is a metonym for the expression pounds per yard and hence a 132–pound rail means a rail of 132 pounds per yard. As a kilogram is approximately 2.2 lb and a metre is roughly 1.1 yards, the pounds-per-yard figure is almost exactly double the kilograms-per-metre figure. Weights are measured in pounds per yard ( imperial units are used in Canada, the United Kingdom and United States) or kilograms per metre (metric units are used in Australia and mainland Europe). The weight of a rail per length is an important factor in determining rail strength and hence axleloads and speeds. Two commonly used rail profiles: a heavily worn 50-kg/m profile and a new 60-kg/m profile Worn, heavy rail from a mainline is often reclaimed and downgraded for re-use on a branchline, siding or yard. Only a small number of rail sizes are made by steelworks at one time, so a railway must choose the nearest suitable size. Rails represent a substantial fraction of the cost of a railway line.
Minor flaws in the steel that may pose no problems in other applications can lead to broken rails and dangerous derailments when used on railway tracks.īy and large, the heavier the rails and the rest of the trackwork, the heavier and faster the trains these tracks can carry. It took many decades to improve the quality of the materials, including the change from iron to steel. Unlike some other uses of iron and steel, railway rails are subject to very high stresses and are made of very high quality steel. The head is profiled to resist wear and to give a good ride, and the foot profiled to suit the fixing system. All modern rails are hot rolled steel with a cross section (profile) approximate to an I-beam, but asymmetric about a horizontal axis (however see grooved rail below). The rail profile is the cross sectional shape of a railway rail, perpendicular to its length.Įarly rails were made of wood, cast iron or wrought iron. Section of the Translohr guidance rail (during the Clermont-Ferrand installation in 2006)
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