LRT wheel hub issues due to unexpected lateral loads: Alstom

Officials with Alstom are offering more details into the issues surrounding wheel hub assemblies on Ottawa’s light rail trains.

In a report presented to the City of Ottawa’s Transit Commission, the French train maker and subcontractor to Rideau Transit Group (RTG) said the biggest issue is higher than expected lateral loads on the wheel hubs during operation.

The wheel hub assemblies on the trains come pre-assembled, and after a train derailment in August 2021, it was revealed the culprit was a loose nut in those assemblies. Essentially, Alstom said high vibrations jarred the components loose over time, leading to the restraining nut unscrewing.

The finding is not something RTG and Alstom are in complete agreement about at this point.

“We may get to an agreement with Alstom on their theory but we’re not quite ready to go there yet,” said RTG president Nicolas Truchon. “We still have evidence that we need to review and discussions that we need to have.”

Meantime, with this information, Alstom said each axle is now being inspected after every 3,750 km of use, rather than the expected 800,000 km. There are other short-term mitigation measures in place like slower speeds at turns and rail line lubrification, which both RTG and Alstom say are helpful, but Alstom says the company has a more long-term plan.

Long-term solutions could include creating a tighter fit inside the assembly and applying a heat treatment to make the material more durable, but with prototypes, planning and testing, these wouldn’t be rolling out until 2026.

“At Alstom, we comletely understand the people’s frustration” said vice-president of rolling stock and components for Alstom in North America, David Van der Wee. “You deserve better. I want to encourage you that you have the full commitment of Alstom to be able to work very tightly with our partners to be able to bring the system back to what was promised and what is deserved.”

Another idea Alstom has recommended is changes to track infrastructure, but Truchon said that needs to be further assessed, as it would include a system shutdown.