1 6 Widening of gauge on curves Extra
- Slides: 23
1. 6 - Widening of gauge on curves, Extra clearance on curves, Minimum length of straight between Reverse Curves. Total periods - 4 1
Gauge Widening on curves • The minimum clearance required to permit the vehicles to negotiate a curve with free curving motion depends on the Maximum rigid wheel base and the Degree of curve for a particular track gauge. • For minimum clearance, it is desirable to have 3 to 5 mm additional clearance to cater to the angularity assumed by the wheel set while negotiating the curve. 2
Gauge in curves • 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 Radius in Mts Gauge B. G ( 1676 mm ) Straight including curves of radius upto 350 m. and more -5 mm. to +3 mm. ( 1671 to 1679 mm ) For curves of radius less than 350 m Upto +10 mm. ( 1686 mm ) 3
Gauge in Curves • While it is desirable to maintain correct gauge, it may not be possible to maintain correct gauge due to age and condition of the sleeper. • It is good practice to work within the following tolerances of gauge, provided generally uniform gauge can be maintained over long lengths: Radius in Mts Gauge B. G ( 1676 mm ) On Straight - 6 mm. to +6 mm. ( 1670 to 1682 mm ) On curves with radius 440 m or more - 6 mm to +15 mm. ( 1670 to 1691 mm ) On curves with radius less than 440 m upto +20 mm. ( 1696 mm ) 4
Providing wide gauge sleepers • The normal PRC sleepers used in the straight have nominal gauge of 1673 mm. • Where the wider gauge is to be provided, special sleepers having wider nominal gauge shall be provided. • The extra widening of the gauge has to be introduced in the transition portion of the curve, and sleepers are also to be provided accordingly. • The gauge shall be changed from normal to the wider gauge in curve at the rate of 1/3 rd widening in each 1/ 3 rd length of transition. ( PSC sleepers on curves RDSO T-4183 to T 4186 ) 5
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• TABLE OF DIMENSIONS DRAWING N O. . PCS NO. . DESIRED GAUGE RDSO/T-4183 53/1 1675 ( + 2 ) RDSO/T-4184 53/2 1677 ( + 4 ) RDSO/T-4185 53/3 1679 ( + 6 ) RDSO/T-4186 53/4 1682 ( + 9 ) 7
• TABLE OF DIMENSIONS DRAWING N O. . PCS NO. . DESIRED GAUGE RDSO/T-4183 53/1 1675 ( + 2 ) RDSO/T-4184 53/2 1677 ( + 4 ) RDSO/T-4185 53/3 1679 ( + 6 ) RDSO/T-4186 53/4 1682 ( + 9 ) 8
• TABLE OF DIMENSIONS for check rail clearance of 75 mm with 60 kg Running rail and 52 kg check rail DRAWING NO. . PCS NO. . DESIRED GAUGE RDSO/T-4183 53/1 1675 ( + 2 ) RDSO/T-4184 53/2 1677 ( + 4 ) RDSO/T-4185 53/3 1679 ( + 6 ) RDSO/T-4186 53/4 1682 ( + 9 ) 9
Laying Sleepers in curves • On curved track, the sleepers are required to be laid radial to the curve. • To ensure this, the spacing should be correctly marked on outer rail and then the position can be transferred on the inner rail with the help of a ‘T’ square. 10
Extra Clearances on curves: Lean and Sway 11
CLEARANCE ON CURVES- LEAN L L = H*Ca/G H Ca H is the height of the structure or maximum height of vehicle whichever is less. G is track gauge as per SOD 12
ADDITIONAL ALLOWANCE DUE TO SWAY • Inside • ¼ of lean due to superelevation • Outside • Not to be considered if lean is there • We do not take advantage of the extra clearance given by lean away from outer side structures 13
Extra Clearances on Curves: Platforms and structures 14
Clearance On Curves- Effect of Chords 15
ADDITIONAL CLEARANCES ON CURVES CENTRE LINE OF COACH OVER THROW Vo BOGIE CENTRES 14. 7 85 2 Vo=14. 785 /8*R CENTRE LINE OF TRACK 16
ADDITIONAL CLEARANCES ON CURVES CENTRE LINE OF COACH OVER THROW Vo END THROW VE 14. 7 85 VE 21. 34 0 CENTRE LINE OF TRACK 2 2 =(21. 34 -14. 785 )/8*R 17
EXTRA CLEARANCE DUE TO CURVATURE • Platforms/ structures • Inside of curve • (VO+L+S-51) • Outside of curve • (VE-25)mm 18
Extra Clearances due to Curvatures • Between Adjacent Tracks VO + VE + 2 * (L/4) • In new works, if c/c track is 5300 mm, extra clearance is to be provided for curves beyond 5° only.
Extra Clearances on parallel curved tracks 20
Min. length of straight in REVERSE CURVES • For high speeds, in Group ‘A’ and ‘B’ routes, a straight with a minimum length of 50 m shall be kept between two transitions of reverse curves. • (i) On groups ‘A’ and ‘B’ routes on straights less than 50 metres between reverse curves should be eliminated by suitably extending the transition lengths. • In doing so, it should be ensured that the rate of change of cant and versine along the two transitions so extended is kept the same. • (ii) Whenever such straights between reverse curves can neither be eliminated nor the straight length increased to over 50 metres, speed in excess of 130 Kmph should not be permitted.
Example • Instructor to give an example to trainees to work out the extra clearances on Platform and ask them to workout themselves for different degree of curvature.
Thanks
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