In railway engineering, what are the principal purposes served by coning of wheels on rolling stock (state the best comprehensive choice)?

Introduction / Context:
Coning of wheels refers to giving the tread of railway wheels a slight taper instead of making it perfectly cylindrical. This small geometric refinement has multiple functional advantages in track–vehicle interaction. The question tests whether you recognise that coning serves several related purposes in stability, guidance, and wear reduction.

Given Data / Assumptions:

• Wheel treads are coned (tapered), not flat.
• We are assessing benefits: lateral guidance, ride smoothness, and rail wear.
• Track is conventional with rails set to gauge and a small cant on curves.

Concept / Approach:
Because the tread is coned, a small lateral shift changes the effective rolling radius of the two wheels on an axle. The wheel that moves outward runs on a larger radius, and the inner wheel runs on a smaller radius. This self-steering effect helps the axle recentre itself, limits hunting, improves smoothness, and reduces flange–rail contact that would otherwise accelerate wear on the rail inner faces.

Step-by-Step Solution:
Identify purpose 1: lateral guidance. Coning creates a restoring tendency that resists uncontrolled side wander.Identify purpose 2: smooth running. Reduced flange impacts and better self-steering lower vibrations and ride harshness.Identify purpose 3: wear reduction. Less flange grinding on the gauge face decreases inner rail wear.Synthesis: since all three purposes are valid outcomes of coning, choose the combined option.

Verification / Alternative check:
Practical railway texts describe conicity as essential for stability at speed and curve negotiation, confirming all three advantages in standard track conditions.

Why Other Options Are Wrong:

• Prevent lateral movement of wheels: True but not the only benefit.
• Provide smooth running of trains: True but incomplete alone.
• Avoid excessive wear of inner faces of rails: True but not the sole reason for coning.

Common Pitfalls:
Assuming coning serves only one purpose; confusing coning with flange lubrication or with rail cant; overlooking the rolling radius differential principle.

Final Answer:
All the above.