on curves By Anil Choudhary Sr ProfessorIRICEN Laying of Fanshaped Layout on Curves The turnouts are supposed to be laid on straight track as spacing are given according to ML as straight ID: 914449
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Slide1
Laying
of
Points and Crossings
on curves
By
Anil Choudhary
Sr Professor/IRICEN
Slide2Laying of Fan-shaped Layout on Curves
Slide3The turnouts are
supposed to be laid on straight
track as
spacing are given according to ML as straightBut it may be required to be laid on curve in field due to existing track geometry/constraints
Fan-shaped Layout on Curves
Slide4It may not be possible to insert liner at few sleepers.
(Photo)
Track circuiting may fail because of rail touching to insert.
Incorrect gauge.
Breakage of GFN liners.
Inadequate holding of CMS Xing.
(Photo)
At few places rail foot may even cut the inserts.
(Photo)
Breakage of
Pendrol
clip.
Inadequate toe load. (Photo)
Problems observed in Laying of
Fan-shaped Layouts on Curves
Slide5Modification Required in the Existing Layout
Change in spacing of sleepers to suit curved M/L track.
Pre-curving of stock and tongue rail to suit the curvature.
Slide6Re-spacing of sleeper
Sleeper are to be rotated by an angle
θ
m
(angle between tangent at SRJ and tangent on main line curve).
Slide7Curved main line track makes an angle of
θ
m
with the straight, sleepers are to be rotated by an angle of θm from the position given by RDSO drawings.In order to keep distance between SRJ to heel of crossing same, the sleepers are required to be rotated on the other than crossing side guage line
Modification Required
Slide8RDSO
’s Letter
No.CT
/PTX Dated 07-10-2005(Contrary flexure)As per codal provision 1 in 12 turnout of contrary flexure can be laid taking off from curved mainline. I in 8.5 can be Laid only if Lead curvature is of R>350mLaying of 1 in 12 T/o in contrary flexure taking off from curved main line (up to 5 degree) by adjusting the sleeper spacing can be laid. Feedback on performance may be send to RDSO.It is not possible to lay turnout of similar flexure on main line curve more than 1 degree, as degree of lead curve will be more than 5 degree.Accordingly spacing for contrary flexure for 2,3,4 and 5 degree issued. Also it says that minor grinding of liner may be required.
Slide9RDSO
’s Letter No.CT
/PTX Dated 17-08-2007
(Similar Flexure)Para 410(2) of IRPWM recommends minimum radius to be 350 m.IRSOD 2004 recommends not less than 218 m.So 1 in 12 might me existing in curve of upto 4 degree.Revised spacing given for similar flexure upto 4 Degree circulated accordingly
Slide10CS 143 of IRPWM 2004
Slide11Orientation of Sleeper in Fan Shaped Layout
Slide12X Area
- Change in spacing of sleeper in switch portion (ORS) is not possible because of pre-drilled hole in the switch.
Y Area
- The first sleepers in the lead is to be shifted by an amount equal to difference of inner/outer rail from SRJ to first sleeper in lead.Z Area (Crossing portion) Constant spacing to be retained.Z Area (After crossing ) ,the outer rail spacing shifted by an amount equal to difference of inner/outer rail in individual spacing.
Modification Required
Slide13Tables for
Laying of Fan-shaped
Layout on Curves
Slide14A SIDE
B SIDE
A SIDE
A SIDE
B SIDE
Slide15A SIDE
B SIDE
A SIDE
A SIDE
B SIDE
Slide16Slide17Slide18Slide19Slide20Slide21Slide22Slide23Slide24Slide25Slide26Slide27Slide28Slide29Slide30Slide31Slide32Tables for
Providing Pre-curving
Slide33Stock as well as tongue rail are to be given required pre-curving for good setting of point.
A table for checking and providing pre-curving for Similar flexure as well as Contrary flexure turnout on curves of various degrees have been prepared
(Not by RDSO)
.The different method to be followed for checking of pre-curving for Similar as well as Contrary flexure turnout has also been given by schematic diagram
Pre-curving of stock and tongue rail to suit curvature.
Slide34Slide35Table 1 - For 1 in 12 Turnout with similar flexure
Slide36stock
Slide37Table 2 - For Contrary flexure 1 in 12
stock
Slide38Table 3 - For Contrary flexure 1 in 8.5
Slide39Advantages and Field Experiences
All the liners could be fixed.
The cases of failure of track circuiting and cases of breakage of GFN liners drastically reduced.
The alignment as well as gauge on turnout improved.
Slide40While doing machine packing in crossing area, the cross level obtained under X-
ing
area were better.
The chances of rail cutting into inserts were almost eliminated.Because of the proper pre-curvature the housing of the tongue rail is improved, which reduced tongue rail wear.
Advantages and Field Experiences
The case of breakage of ERC was also reduced.
Check Rail to RDSO Drawing No RDSO/T-6076 on inside
in similar Flexure to Reduce wear (IRSOD-for 8 degree and above)
Slide41Thick web switch in curve
Slide42Thick web switch in curve Contd..
Slide43Slide44Slide45Thank You