The discovery Wednesday of another broken coupler pin on one of Muni’s new train cars – a part already replaced once because of similar problems in April – left a key San Francisco official wondering about Muni’s request for rushed funding for 150 new cars.
"Obviously, this is hugely disappointing," said Supervisor Aaron Peskin, who also oversees the city’s transportation funding authority.
He said until this week, Muni had assured him that problems with doors, couplers and brakes had already been resolved in time for the agency to push for city funding for rushed production of 151 new cars. But the latest incident on the city’s current fleet of 68 cars has him wondering about those assurances.
"We are now back to square one. I want to know who knew what, when," Peskin said.
According to a memo from Muni director Julie Kirschbaum obtained by NBC Bay Area’s Investigative Unit, a Muni operator reported what she said felt like a constant slamming impact into the rear of a two-car train in service Wednesday morning.
She drove the K-Ingleside train to a nearby Muni yard, where an inspection confirmed that a shear pin – a key piece of the coupler system – had failed due to apparent fatigue.
On Monday, train maker Siemens alerted Muni that dozens of coupler shear pins it had sent to the city after the pin failure in April were themselves at risk of failing.
In fact, Kirschbaum told staff that Siemens could not vouch for the coupler pin safety beyond 120 days service because of what she called unexplained fatigue issues.
"They don’t last as long as they’re supposed to," Muni spokeswoman Erica Kato said Thursday, noting that while shear pins don’t actually bind trains together, they do act as a fail-safe during crashes by absorbing impact forces. They also link electrical systems between cars.
Muni got 30 new replacement pins on Thursday, Kato said, and expects 200 more Friday – with crews working to install the new pins as quickly as possible to limit passenger crowding and inconvenience.
"Rider impact should be very minimal as we head into early next week," she said. "We’ll continue to get pins until they re-engineer a better design."
But Peskin says the latest pin snafu makes him skeptical about Muni’s request to rush delivery on 150 new cars slated to be considered in January.
"This episode continues to be disappointing," he said. "We are going to ask the tough questions, we’re going to get answers and if this is not ready for prime time, we’re not going to fund it."