Types Of Rails, Requirements And Length Of Rails
This Article Covers Types Of Rails Requirement Of An Ideal Rail And Length Of Rails One By One. Rails are the members of the track laid in two parallel lines to provide an unchanging, continuous, and level surface for the movement of trains. To be able to withstand stresses, they are made of high-carbon steel.
TYPES OF RAILS
Types Of Rails - DOUBLE HEADED RAIL - BULL HEADED RAIL - FLAT-FOOTED RAIL Double heading indicates the use of two locomotives at the front of a train, each operated individually by its own crew.
The rail section whose head dimensions are more than that of their foot called bullheaded rails. In this type of rail, the head made little thicker and stronger than the lower part by adding more metal to it. Bullheaded rails especially used for making points and crossings.
Rail sections having their foot rolled to flat are called flat-footed or Vignoles rails.
These Are Three Types Of Rails Commonly Used. FUNCTION OF RAILS Rails are similar to steel girders. They perform the following functions in a track:- - Rails provide a continuous and level surface for the movement of trains. - They provide a pathway which is smooth and has very little friction. The friction between the steel wheel and the steel rail is about one-fifth of the friction between the pneumatic tyre and a metalled road. - They serve as a lateral guide for the wheels. - And They bear the stresses developed due to vertical loads transmitted to them through axles and wheels of rolling stock as well as due to braking and thermal forces. - They carry out the function of transmitting the load to a large area of the formation through sleepers and the ballast REQUIREMENTS OF AN IDEAL RAIL SECTION The requirements of an ideal rail section are as follows: - The rail should have the most economical section consistent with strength, stiffness, and durability. - The centre of gravity of the rail section should preferably be very close to the mid-height of the rail so that the maximum tensile and compressive stresses are equal. - A rail primarily consists of a head, a web, and a foot, and there should be an economical and balanced distribution of metal in its various components so that each of them can fulfill its requirements properly. The requirements, as well as the main considerations, for the design of these rail components are as follows:- Head The head of the rail should have adequate depth to allow for vertical wear. The rail head should also be sufficiently wide so that not only is a wider running surface available, but also the rail has the desired lateral stiffness. Web The web should be sufficiently thick so as to withstand the stresses arising due to the loads bore by it, after allowing for normal corrosion. Foot The foot should be of sufficient thickness to be able to withstand vertical and horizontal forces after allowing for loss due to corrosion. The foot should be wide enough for stability against overturning. The design of the foot should be such that it can be economically and efficiently rolled. Fishing angles These must ensure proper transmission of loads from the rails to the fish plates. The fishing angles should be such that the tightening of the plate does not produce any excessive stress on the web of the rail. Height of the rail The height should be adequate so that the rail has sufficient vertical stiffness and strength as a beam. Weight of rails Though the weights of a rail and its section depend upon various considerations, the heaviest axle load that the rail has to carrv olavs the most important role. The following is the thumb rule for denning the maximum axle load with relation to the rail section:- Maximum axle load = 560 x sectional weight of rail in Ibs per yard or kg per metre For rails of 90 Ibs per yard, Maximum axle load = 560 x 90 Ibs = 50,400 Ibs or 22.5 tonnes For rails of 52 kg per m, Maximum axle load = 560 x 52 kg = 29.12 tonnes For rail of 60 kg per m, Maximum axle load for 60 kg/m rail = 560 x 60 kg = 33.60 tonnes Length of rails Theoretically, the longer is the rail, the lesser would be the number of joints and fittings required and the lesser the cost of construction and maintenance. Longer rails are economical and provide smooth and comfortable rides. The length of a rail is, however, restricted due to the following factors:- - Lack of facilities for transport of longer rails, particularly on curves - Difficulties in manufacturing very long rails - Difficulties in acquiring bigger expansion joints for long rails - Heavy internal thermal stresses in long rails Taking the above factors into consideration, Indian Railways has standardized a rail length of 13 m (previously 42 ft) for broad gauge and 12 m (previously 39 ft) for MG and NG tracks. Indian Railways is also planning to use 39 m, and even longer rails in its track system. Now 65 m/78 m long rails produced at SAIL, Bhilai and it planned to manufacture 130 m long rails. Thank You For Visiting... Also Check Video Tutorial Site KPSTRUCTURES.COM Stresses In Rigid Pavement Bituminous Mix Design Read the full article
