The Driving Force: EN 13104 and the Legacy of Powered Axle Design

What was EN 13104?

EN 13104 was the specialized European Standard titled “Railway applications – Wheelsets and bogies – Powered axles – Design method.” Until its recent consolidation, it served as the definitive engineering guideline for calculating the dimensions and validating the structural integrity of powered axles (axles driven by a traction motor/gearbox) on railway vehicles.

Unlike free-rolling trailer axles, powered axles are subjected to additional torsional stresses and complex bending moments caused by traction torque and the weight of the transmission units (gearboxes, motors). EN 13104 defined the formulas to calculate these unique load cases, ensuring that the axle could withstand millions of operational cycles without fatigue failure.

The Transition to EN 13103-1

It is crucial to note that EN 13104 has been withdrawn and superseded. In an effort to simplify the standardization landscape, CEN merged the requirements for powered axles (formerly EN 13104) and non-powered axles (formerly EN 13103) into a single, unified document: EN 13103-1.

However, EN 13104 remains a vital reference for the maintenance, assessment, and refurbishment of the massive fleet of existing trains (“legacy fleet”) that were originally designed and certified under this standard.

Key Technical Calculations

The standard provided a step-by-step methodology for dimensioning an axle:

• Forces and Moments: It defined how to combine vertical static loads (train weight) with dynamic loads (track irregularities) and traction/braking forces.
• Material Properties: It specified the fatigue limits for standard steel grades like EA1N (defined in EN 13261), allowing engineers to determine the maximum permissible stress.
• Geometry: It offered guidelines for transitions and radii to reduce stress concentrations, particularly where the gearbox or brake discs are mounted.

Comparison: Powered vs. Non-Powered Axle Design

The distinction between the legacy standards highlights the added complexity of propulsion.