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The minimum railway curve radius is the shortest allowable design radius for the centerline of railway tracks under a particular set of conditions. It has an important bearing on construction costs and operating costs and, in combination with superelevation (difference in elevation of the two rails) in the case of train tracks , determines the ...
The larger the degree of curvature, the sharper the curve is. Expressing the curve in this way allows surveyors to use estimation and simpler tools in curve measurement. This can be done by using a 62-foot (18.90 m) string line to be a chord to connect the arc at the gauge side of the reference rail.
The Hallade method, devised by Frenchman Emile Hallade, is a method used in track geometry for surveying, designing and setting out curves in railway track. [1] It involves measuring the offset of a string line from the outside of a curve at the central point of a chord. In reality, string is too thick to provide a clear reading and breaks ...
The design pattern for horizontal geometry is typically a sequence of straight line (i.e., a tangent) and curve (i.e. a circular arc) segments connected by transition curves. The degree of banking in railroad track is typically expressed as the difference in elevation of the two rails, commonly quantified and referred to as the superelevation.
As an example, a curve with an arc length of 600 units that has an overall sweep of 6 degrees is a 1-degree curve: For every 100 feet of arc, the bearing changes by 1 degree. The radius of such a curve is 5729.57795. If the chord definition is used, each 100-unit chord length will sweep 1 degree with a radius of 5729.651 units, and the chord of ...
For high-speed trains and in tighter curves that distance needs to be increased. The track spacing is also called the centre-to-centre spacing to differentiate it from the edge-to-centre spacing of a railway. These two values may be different depending on how signal masts are added to the overall track geometry.
Track lubrication on a reverse curve in an area prone to movement due to wet beds. Normally, passenger trains run above the balancing speed, and the difference between the balancing superelevation for the speed and curvature and the actual superelevation on the curve is known as unbalanced superelevation.
George Stephenson introduced the 1,435 mm (4 ft 8 + 1 ⁄ 2 in) gauge (including a belated extra 1 ⁄ 2 in (13 mm) of free movement to reduce binding on curves [16]) for the Liverpool and Manchester Railway, authorised in 1826 and opened 30 September 1830. The extra half inch was not regarded at first as very significant, and some early trains ...