In Indian Railways, the widening of the gauge (extra width) on curves is :
- AW = 13 (B + L) / R²
- BW = 26 (B + L)² / R
- CW = 13 (B + L)² / RCorrect
- DW = 13 (B + L)² / 2R
Solution
Concept
Extra gauge on curves
Formula
W = 13 (B + L)² / R (mm; B = rigid wheel base in m, L = lap of flange in cm, R = radius in m)
Step-by-step solution
1. On a curve a long rigid wheel base needs more gauge to negotiate the curve. 2. The empirical formula for Indian Railways: W = 13 (B + L)² / R.
Explanation
The extra width on curves depends on the rigid wheel base, the lap of the flange and the radius. The widening is inversely proportional to the radius and proportional to the square of (B + L).
Why the other options are wrong
The other forms put R² in the denominator, double the numerator constant or add a factor of 2 in the denominator, none of which is the standard formula.
Shortcut
W = 13 (B + L)² / R.
Common mistake
Putting R² in the denominator.
Correct answer: C) W = 13 (B + L)² / R