Switch geometry on BG tracks: Recommended heel divergence (distance between the running face of stock rail and gauge face of tongue rail at the heel) for Indian Broad Gauge is closest to which value?

Introduction / Context:
Heel divergence is a key geometric parameter of a switch, affecting wheel guidance, fit-up, and compatibility with standard turnout components. Indian BG standards specify a nominal divergence at the heel to ensure interchangeability and safe operation.

Given Data / Assumptions:

• Standard BG turnouts (e.g., 1 in 8.5, 1 in 12) with standardized switch assemblies.
• Looking for typical recommended heel divergence dimension.

Concept / Approach:
Heel divergence is defined at the heel where the tongue rail ends and is connected to the switch rail via heel block/fastenings. The dimension is chosen to balance smooth entry, avoid excessive flangeway variation, and fit standard bearers and fittings. A common standard value is approximately 125 mm for Indian BG practice.

Step-by-Step Solution:
Identify the standard heel divergence used across BG switches.Confirm compatibility with standard bearers and switch plates.Select 125 mm as the recommended nominal value.

Verification / Alternative check:
Standard drawings for BG switches indicate heel divergence in this range, ensuring consistent fit and wheel guidance across turnout types.

Why Other Options Are Wrong:
100 mm, 119 mm: Below typical standard; may compromise fit and flangeway.135 mm, 155 mm: Larger than standard and could affect wheel guidance and component compatibility.

Common Pitfalls:

• Confusing heel divergence with switch opening at the toe.
• Using non-standard values that hinder interchangeability of components.

Final Answer:
125 mm