(2) Curves can be designated by the radius in metres or by its degree. The angle subtended at the center by a chord of 30.5 metres, is the degree of the curve.
Curves shall be described invariably by the radius in metres. The level of inner rail of any curve is taken as reference level. Super elevation is provided by raising the outer rail. For reverse curves, however, stipulation as laid down in Para 408(3) shall apply.403. Gauge On Curves - The gauge on curve shall be to the following standards : -(1) On new lines and on lines where complete renewal or through sleeper renewal is carried out, the track should be laid to the following standards -
(2) Gauge on the wooden sleepered road however, need not be disturbed, if it is likely to cause spike killing of sleepers. Uniformity of the gauge should be stressed in all cases to get better track riding quality.
Graphs showing (i) maximum permissible speed for transitioned curves of different radii and equilibrium cant are appended in
The formula (a) and (b) are based on rate of change of cant and of cant deficiency of 35 mm. per second. The formula (c) is based on the maximum cant gradient of 1 in 720 or 1.4 mm. per metre. A curve of 600 metres radius has a limited transition of 40 metres length. Calculation of maximum permissible speed and superelevation is as follows :-
Where S = shift in centimetres. L & R being in metres.
Where Y = off-set from the straight in centimetres.
The original circular curve TC is tangential to the straight at T. The curve is shifted to ZY and TZ is the amount of shift. The transition curve MNP bisects the shift TZ at N. A typical example of working out maximum permissible speed on a curve, calculating the length of transition and detailed calculation of laying the transition are given in
(7) When realigning old curves, transition curves on approaches should invariably be provided. It should should be ensured that there is no change of grade over the transition. (i) L = 0.008 (C (ii) L = 0.008 (C Cant gradient should be within the permissible limits as stated in
In case No. 1 the level of one of the rails is maintained and the super elevation is run out in the other rail by lowering it over half the transition length and raising it to the required amount of cant over the remaining half portion of the transition
(c) the permissible speed on turn-outs taking off on the inside of the curve should be determined by taking into consideration the resultant radius of lead curve which will be sharper than the lead curve for turnouts taking off from the straight. 1 in 8-1/2 turn-outs should not be laid on inside of curves.
In case exceedence of the above limit is observed during an inspection, local adjustments may be resorted to in cases where the variation of versines between adjacent stations is only at few isolated locations, at the earliest possible. If more than 20% of the stations are having versine variation above the limits prescribed, complete realignment of the curve should be planned within a month.
Curve from km.........................................................................................to km..........................................
d = LG/R
Note - No. of Pages to be allotted for each curve. |
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