Tuesday, March 27, 2018

Special Layouts

1.Symmetrical Splits               2.Diamond Crossings          3.Scissors Cross over

SYMMETRICAL SPLITS:Centre line of crossing lies on the centre line of track Diamond Crossings:- The diamond crossing shall not be flatter than 1 in 8½. This restriction of angle of crossing is due to the fact, that while approaching to nose of obtuse crossing the wheel is not guided by check rail for a distance of 407mm in case of 1 in 8½ and 643mm in case of 1 in 12 crossing with 52kg rail. Longer gap increases the chances of wheels taking two roads.

• Formed when two tracks cross each other
1).If same gauge – rhombus
2).If different gauge – parallelogram
3.)If at right angle – square diamond
• Right angle diamond to be avoided
• Slip are laid to provide arrangement to divert vehicles from one track to
another
1).Single slip                                                                     2).Double slip
DEFICIENCY OF DIAMOND CROSSING
• While approaching the nose of obtuse crossing the wheel is not guided by check-rail for a certain length
• How to overcome :
– Top level of check rail is raised by 25 mm
– Flange way clearance is reduced from 44 mm to 41 mm (BG)
– Switch Diamond

1:8.5 B.G 52 Kg DIAMOND CROSSING ON PSC SLEEPERS

• Without slips : RT- 5362
• With Single Slips : RT- 5363
• With double slips : RT- 5364
• Obtuse crossing (CMS) : RT- 5265
• Acute crossings (CMS) : RT- 4867

Raised Check Rail

Two raised check rails are provided in an ordinary diamonds obtuse crossing to prevent the derailment during restarting of a halted vehicle at diamond crossing. The check rail is raised by 25mm by welding a mild steel plate of 1meter length.
Since the distance between throat of crossing to actual nose of point rail is double in an obtuse crossing as compared to an ordinary crossing this precaution is essentially to be taken in an ordinary diamond crossing. This problem is solved by provision of moveable switch diamond therefore raised check rails are not required in movable switch diamond and the angle of MSD crossing can be flatter than 1 in 8½ but these are not in use due to operating problems. In addition the flange way clearance at the throat of obtuse crossing is reduced from 44mm to 41mm in case of B.G. Since a plain diamond crossing does not have the facility of diverting movement from one track to another track, slips are provided in the diamond portion. Diamond crossing may be with single slips or double slips. In case of single slip diamond 2 sets of switches are used taking toe of crossing as SRJ and 4 sets of switches are used in case of double slip diamond.

DERAILING SWITCHES ON PSC SLEEPERS
• 1:8.5 BG 52 Kg :       RT- 5836 1:8.5       BG 60 Kg :        RT-6068
Nominated LH or RH according to location of tongue rail & not like direction of
T/out.

SCISSORS CROSS – OVER

• To enable transfer of vehicles from one track to other and vice-versa
• Provided where space does not permit provision of two separate cross overs.
• Consists of four pairs of switches. Six acute crossings, two obtuse crossings and check rails.

1:8.5 BG 60 Kg SCISSORS CROSS OVER ON PSC SLEEPERS

• Crossing assembly :  RT-6092 Acute LH         (CMS): RT- 6093
• Acute RH (CMS) :   RT-6096 Obtuse              (CMS) : RT-6099

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