On Thursday, for the first time since the beginning of July, Regional Rail's fleet included the cars whose defective parts caused a scheduling nightmare this summer for rail commuters.

Four of SEPTA's Silverliner V cars returned to service on the Fox Chase Line Thursday morning. They were equipped with new equalizer beams replacing cracked parts that forced 120 cars out of service for safety reasons. And more beams are on the way. SEPTA officials provided a tour Thursday of the Bucks County metalworking business where replacement beams are being cut and prepared. The authority's general manager, Jeff Knueppel, said commuters should see a return to regular service by the beginning of October.

"I think it's been a very aggressive return-to-service schedule," he said, surrounded by dozens of newly painted black beams ready to be installed on railcars.

PennFab Inc., a Bensalem-based company, has cut 340 of the 480 equalizer beams needed to replace the flawed parts. The 380-pound, 9-foot-long beams are cut from plates of T1 high-strength steel with a white-hot plasma cutter, then are machined, tested, and painted. The company has been making 60 equalizer beams a week, said PennFab's president, Michael Mabin.

"We commit the entire resources to our company, and that's what makes it get done," he said.

The beams have feet from Hyundai Rotem attached at either end with pins and then are sent to Kinkisharyo International in Jersey City, where the beams are attached to trucks. The last step, attaching the repaired trucks under the Silverliner V cars, happens at SEPTA's Overbrook maintenance facility. The process, from factory to finished car, takes about 12 days, Knueppel said. He said he expected all 120 Silverliner cars to be back in service by mid-November.

PennFab and Kinkisharyo were selected by Hyundai Rotem and are being paid through that company, so no bidding process was required, though SEPTA provided input as to the selections, SEPTA officials said.

The process of making and installing the beams is happening much faster than usual because of the urgent need to get cars back on the rails, Mabin said. He used the schedule for obtaining steel as an example. Getting steel for this kind of manufacturing usually takes six to eight weeks, he said. This steel arrived from an Arkansas company 72 hours after an order was placed.

The July 4 weekend, a SEPTA inspector observed a listing train car, and the subsequent investigation revealed the cause:  equalizer beams in 115 of 120 Silverliner V's had cracks in them. The beams transfer the weight of the car to the vehicle's axles, and the strain of use caused cracks to develop where feet were welded to the ends of the beams. Officials have blamed a poor design and improper welding for the flaws in cars that had been in service for only three to six years.

SEPTA pulled all 120 of the Silverliner V cars almost immediately after discovering the cracks, which had the potential to cause a serious accident if allowed to get worse. But losing a third of its rail fleet has created problems for riders. Late and overcrowded trains have become the norm, and SEPTA estimates it has lost 10 percent to 20 percent of its rail passengers to other modes of travel. Before the Silverliner V cars failed, SEPTA was transporting about 65,000 people per weekday by Regional Rail.

Summer's unofficial end this weekend means returning students, an end to vacations, and more train riders. SEPTA anticipates a difficult September. It is creating express bus routes to supplement trains on the Chestnut Hill East, Chestnut Hill West, Fox Chase, Airport, Warminster, West Trenton, Lansdale/Doylestown, Manayunk/Norristown, and Media/Elwyn Lines. SEPTA also has boosted its fleet of leased cars to 48 vehicles, which should allow a return to normal schedule more than a month before all the Silverliner V cars receive new beams.

Although the exact cost of repairs per car was not provided, Hyundai Rotem, the South Korea-based company  that won the contract to construct the Silverliner V cars, has so far spent $2.7 million to fix the railcars, a company spokesman said Thursday.

Even though Hyundai Rotem is absorbing the repair costs, SEPTA is still taking a big financial hit. The transportation agency lost $2.7 million in revenue in July. That month it also spent $600,000 in leased railcars, an expense that is expected to increase to $1 million in September.  The express bus service will cost $100,000 a week.