Bearing problem led to broken axle in Sunday's LRT derailment

Sunday night's derailment of an LRT train in Ottawa was caused by a problem with an axle bearing, according to a memo sent Friday afternoon by the city's general manager of transportation, John Manconi.

Rail service on Confederation Line expected to resume Saturday

Crews walk along the Confederation Line in Ottawa on Aug. 9, 2021, one day after the derailment. The Transportation Safety Board of Canada is now investigating. (Alexander Behne/CBC)

Sunday night's derailment of an LRT train in Ottawa was caused by a problem with an axle bearing, according to a memo sent Friday afternoon by the city's general manager of transportation, John Manconi.

However, CBC sources with knowledge of the events say the bearing problem led to the axle actually breaking — a fact that is not in Manconi's memo to council and transit commission members.

After the memo was released, city officials told CBC that the axle had indeed broken, but clarified that it was actually the wheel that snapped off the axle.

The green bolt inside the axle bearing was loose for some reason, leading to a broken axle and the derailment. (Provided by the City of Ottawa)

An axle is the rod that connects a set of wheels on either side of a train car, and a bearing is a device installed at each end of the axle that helps the wheel spin without resistance. When a bearing, which is installed inside the axle, wears out, it can be lead to rumbling sounds and bumpy rides, and can cause problems with the axle.

According to the memo, which includes a photo of the bearing, "the sealed unit was taken apart and it was found that the green section of the bolt, which should be completely tightened, had a very small amount of movement, by fractions of a millimetre. This movement caused damage to the bearings inside the unit and wheel, which in turn lead to the axle coming off the track on Sunday evening."

The update goes on to say that the "root cause" was "the fault in the axle bearing assembly."

What the memo doesn't say is whether that loose bolt in the bearing was a manufacturing defect, or was caused in some way by the design of the rail system. The investigation into the issue continues.

The axle of an LRT train on Ottawa's Confederation Line came dislodged from the rail on Aug. 8, 2021, prompting an investigation by the Transportation Safety Board of Canada. (Alexander Behne/CBC)

LRT service to resume Saturday

Meanwhile, all trains are being inspected by Rideau Transit Maintenance (RTM) "to make sure everything is in working order and safe," according to Manconi, who added that all trains will undergo safety certification before going into service.

"As the investigation continues, RTM have implemented an inspection procedure that ensures the safe ongoing operation of trains," states the memo. "We have also confirmed with RTM and Alstom that these axle components are in use in other light rail transit vehicles around the world."

Service on the Confederation Line will resume at 6 a.m. Saturday with a "reduced number of trains running every 10 minutes," according the memo.

It's unclear how many trains will be in use, but "as more trains are cleared to return to service, the frequency and capacity of the line will be increased," Manconi writes in the memo.

"This reduced frequency will provide enough capacity to carry all customers without overcrowding. OC Transpo will have buses on standby at strategic locations across the alignment to assist should customer loads be higher than anticipated."

LRT train on track for days

A heavy-duty dolly or truck dummy, which can hold up wheels but doesn't have a motor, is used to move trains that aren't working, including when they have derailed.

But neither the city nor RTM had the equipment needed to move a disabled train, so it had to be brought in from another city. The dolly had to be tested in the yard before it was used on the main track. 

It took hours for the broken train to be slowly pushed the approximate 10 kilometres from Tunney's Pasture to the Belfast yard.

The train was accompanied by half a dozen people who walked alongside it in the hot, humid weather to make sure the light rail car didn't slip off the dolly. According to CBC sources, the train did come off the dolly — twice — and had to be replaced.