INSTRUCTIONS.

Superelevation or “Cant.”

Expansion of Rails.

Gauge and Checking of Curves.

W. W. GRIERSON,
Chief Engineer.

Paddington,
June, 1922.

SUPERELEVATION OR “CANT.”

To be given to the Outer Rail in Curves ranging from 6 to 200 Chains Radius.

Offset
(Length of
Cord 66 ft.)

Radius
of
Curve.

Minimum “Cant.”

Maximum “Cant.”

Outer rail
to be raised.

For a
maximum
speed of

Outer rail to
be raised.

For a
maximum
speed of

Inches.

Chains.

Inches.

miles per hr.

Inches.

miles per hr.

16½

6

3¾

20

6

25

10

10

3½

25

5⅛

30

6⅝

15

3⅜

30

4⅝

35

5

20

3½

35

5¾

45

4

25

2¾

35

4⅝

45

3¼

30

3

40

4¾

50

2¾

35

2⅝

40

4

50

2½

40

2¼

40

5⅛

60

2¼

45

2½

45

4½

60

2

50

2¼

45

5⅝

70

1⅝

60

1⅞

45

4⅝

70

1⅜

70

1⅝

45

4

70

1¼

80

1¾

50

3½

70

1⅛

90

1½

50

3⅛

70

1

100

1⅜

50

2¾

70

⅞

120

1⅛

50

2⅜

70

¾

140

1

50

2

70

⅝

160

⅞

50

1¾

70

½

200

¾

50

1⅜

70

The amount of “cant” to be given to a curve is governed by the speed at which trains run over it, and in no case must the raising of the outer rail in Running Lines be less than is given in the column headed “Minimum Cant,” except where necessary to meet special cases, as at switches, crossings and junctions. In curves on falling gradients where high speeds are run, the outer rail must be kept well up, while on rising gradients a lesser “cant,” but within the limits of the latter, must be given. On gradients on single lines the outer rail of curves must, as a rule, be raised to suit the speed of descending trains.

The superelevation must be gradually attained at the rate of 1 inch in each 66 feet length as the curve is approached, maintained uniformly over the whole length of the curve, and run out after passing the curve in the same way.

On reverse curves, or curves with very short pieces of straight between them, the “cant” must be made gradually on the curves commencing at the middle of the short piece of straight in the latter case.