French Railway Techniques PDF

CAMTECH/M/3 123 *************************************************** APPENDIX „E‟ Excerpts from “FRENCH RAILWAY TECHNIQUES” Special number no. 1/1978 The guiding of a Railway...

CAMTECH/M/3 123 *************************************************** APPENDIX „E‟ Excerpts from “FRENCH RAILWAY TECHNIQUES” Special number no. 1/1978 The guiding of a Railway vehicle, be it a power vehicle or a trailer, owes nothing to the flanges which are no more than block stops for exceptional situation : - abnormal running surface wear - cant excess or deficiency or - negotiations of switch and crossing work Normally it is ensured by the action of the VISCO elastic contact forces between the conical surfaces of the wheels, both solidly attached to the same axle, and the cylindrical surfaces of the rails. 2. If the cone angle is insufficient, the restoring forces towards the centre disappear and the moving wheelset bears permanently against one of the flanges, which is not designed for that. 3. If the angle is excessive, the restoring force if excessive, of short wave length, say 20 M or less. 4. With a concity, which according to calculation and experience should be about 1/40 or 0.025, the hunting A TECHNICAL GUIDE ON DERAILMENTS April ‘98 CAMTECH/M/3 124 wavelenghth is about 30 M, and the restoring force is sufficiently moderate to be easily controlled by the suspension. 5. Under these conditions, the contact between rail and wheel, far from sweeping the full clearance of from 18 to 20 mm between the wheel set and track, is confined to some 8 mm. 6. Within that width, the movement is in no way random but is determined by the track parameters, gauge, levelling, inclination of the wheels and the shape of the running surfaces; as between one day and another, a given TGV wheel set make contact with the rail in accordance with practically identical trajectories(rolling lines). 7. The oscillatory graph movements of the logic about its vertical axis are in harmony with its hunting movements and their angular amplitude does not excess 2.5 M. radius or about 10 minutes of arc. 8. All other things being equal, a definite limit is set to that ideal situation by the critical speed. A TECHNICAL GUIDE ON DERAILMENTS April ‘98 CAMTECH/M/3 125 GLOSSARY Ballast The material used as elastic cushion between sleepers and the top of formation is called ballast. Cant or Superelevation On curves, outer rail of the track is raised higher than the inner rail. This difference of level is called Super- elevation or cant Cant deficiency The difference between the cant necessary for the maximum permissible speed on a curve and actual cant provided. Cross level The relative difference in vertical levels measured at the top of the left and right rails at a given point on the track. Creep The longitudinal movement of rails in the track is called Creep. A TECHNICAL GUIDE ON DERAILMENTS April ‘98 CAMTECH/M/3 126 Deep flange When depth of the flange becomes more than 35 mm. Flange force Force generated by wheel flange during movement of wheel on the track. Formation Flat surface of earthwork on embankments or on cuttings for laying railway track is called Formation. Gauge The distance between two running edges of the rails. Gradient Amount of slope in longitudinal direction in a railway track is called gradient or grade. Hollow tyre Tyre hollowness exceeding 5 mm. A TECHNICAL GUIDE ON DERAILMENTS April ‘98 CAMTECH/M/3 127 Point & Crossing Assembly of components which enables the trains to move from one track to other is called Point & Crossing. Running edge of the rail The rail edge on which wheel flange contacts the rail. Sharp flange Flange worn out in such a way that radius at the tip of flange reduces below 5mm. Stock rail Rail of the main line track against which tongue rails fit. Switch Stock rail and its respective tongue rail form a switch. Tongue rail The tapered rails whose thicker end is known as Heel are fixed to the main track and the thinner end, known as Toe of the switch. A TECHNICAL GUIDE ON DERAILMENTS April ‘98 CAMTECH/M/3 128 Thin flange Flange thickness below 16mm. Throw of switch The distance through which the tongue rail moves at the toe of switch is called throw of switch. Its value on Indian railway is 114mm. Twist The rate of change of variation in cross level per meter. Transition of curve It is an easement of curve in which change of degree is uniform. Wheel base The distance between the two adjacent axles of a bogie is called wheel base. Wheel gauge The distance between the inner surface of flanges of left and right wheel mounted on an axle. A TECHNICAL GUIDE ON DERAILMENTS April ‘98