City has a 'final fix' for the LRT but hasn't ID'd root cause
Redesigned wheel hub called a permanent solution; no root cause identified
The makers of Ottawa's problem-plagued light rail transit system say they are working on a permanent solution for a recurring issue linked to a derailment — without identifying what's causing the train bearings to fail.
Alstom, the French train maker that designed the Citadis Spirit train to the city's specifications, and Rideau Transit Group (RTG), the consortium that built the Confederation Line, will now spend the next 12 to 18 months designing and testing a new wheel hub assembly.
"At last, we are working on the root problem and not just the issues that arise from it," Mayor Mark Sutcliffe told reporters on Monday.
"With a newly designed axle, we will no longer have the problems that we've been experiencing so far."
The city also introduced a timeline for restarting rail service, saying trains will be ready at the end of July, at the earliest.
But none of these steps come with a straightforward response to the question people have been asking for years: What caused a bearing to become loose enough to allow a wheel to break off its axle?
Engineers still diagnosing issue
The city has already finished inspecting the majority of its fleet for signs of additional wear on train bearings, or what general manager of transit services Renée Amilcar called a "symptom."
Now the city, RTG and Alstom are working to understand the "disease," or system problems that are allowing these problems to continue.
Glen Gower, chair of the transit commission, told CBC the wheels are clearly not built to meet the requirements of the system and are wearing out sooner than they should.
"They should last 1.2 million kilometres," he said. "That would be years of use for the trains, and they're failing much before that."
Patrick Dumond, a professor of mechanical engineering at the University of Ottawa, said the axle problem is not surprising as Ottawa's trains are required to hold 24,000 passengers per hour — a load more than twice that of a normal light rail system, and much closer to a subway.
"For some reason they decided to stay with the light rail configuration," he said. "But the trains did get bigger. They got longer. They got heavier."
Dumond said the size of the bearing cartridge stayed the same, which may have lead to more force being exerted.
Root cause analysis coming soon
Heavy loads, similar to the crowds leaving Bluesfest, have been tested in recent weeks to see if they're causing the unusual wear-and-tear.
Richard Holder, the city's director of engineering services, said none of the tests found conditions for "instantaneous failure" but suggested reliability may drop with "repetitive loads."
It's like a twist tie being bent and straightened over and over until it eventually breaks, Dumond explained.
While Dumond has no access to specific data, he said redesigning the wheel hub assembly makes sense.
Strengthening it by using better materials — as RTG and Alstom appear ready to do with their new axle hub assemblies — will allow the system to withstand more force.
Another issue raised in the LRT inquiry was the side-to-side force exerted on the wheel bearings as a train pushes around corners at high speed.
"If you're coming into a corner with a train that's way heavier than it should be, that first rail that comes into the corner," Dumond said, "you can imagine that you're putting almost all of that extra load onto that one wheel."
The city has also looked at potential track issues, adjusting restraining rails built to prevent derailments and adding lubrication to the top of the rails around the tightest curves.
- Axle bearings on Ottawa LRT might need to be redesigned
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Holder said the root cause analysis of the 2021 derailment should be released within the next few months, but teams are working on recommendations from the Transportation Safety Board and the National Research Council, which RTG hired to look into it.
"Based on their experience and everything they've seen, they have a very good idea of what the problem is now," he said, further extending the city's medical analogy. "They're just waiting for the blood work to come back."
Who pays for the fix?
The city plans to gradually resume service starting next Monday, but Amilcar said that timeline is contingent on the completed inspection of all bearings in the fleet, the French manufacturer's analysis of the failed hub assembly and a safety plan from Alstom and RTG.
"They're working on a redesign that will bring a final fix," Amilcar said. "In the meantime, for sure, we will need to continue to improve the current system to ensure we can safely continue to use the [light rail vehicles] as we have them now."
Specific plans to bolster maintenance will come in the next few days.
In the meantime, frustrated commuters will continue to rely on a replacement bus service that often lengthens their commute. The added service also relies on paying overtime to drivers.
But Gower said as long as the train is not running, the city will not have to pay the "millions of dollars per month" it usually provides to RTG for a functioning LRT.
The testing and the fix itself, meanwhile, will be fully covered by RTG and Alstom.
"I believe that one day we will have a safe, reliable light rail service for the people of Ottawa, for the passengers of OC Transpo, for the people who rely on public transit," Sutcliffe said.
"This work is bringing us closer to that day."
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