DC-to-AC rebuild
During the middle of May, Canadian National tested its first modified DC-to-AC rebuild on an ore train in northern Minnesota. This is the first step to replacing a fleet of older General Electric locomotives that were built over three decades ago and currently handle the majority of the region’s ore.
Canadian National’s Minnesota ore service is a high-tonnage, short-haul network from multiple mines around the Virginia, Minn., area, with finished taconite ore pellets hauled to ports on Lake Superior at Two Harbors and Duluth. Steep grades approaching 3% to the lake require the use of a non-standard straight air system on specially equipped locomotives and cars.
This straight air system, similar to using retainers on each freight car, is designed to hold a brake set and is controlled via an additional brake lever in the locomotive cab. This allows the engineer to release and recharge the automatic brake system while descending a grade. Canadian National has a small fleet of specially equipped C40-8s, SD40-2s, and SD40-3s modified with straight air that are captive to this region.
Back in 2021, Canadian National tested Norfolk Southern AC44C6Ms in Minnesota ore service prior to placing orders with Wabtec for its own DC-to-AC conversions. CN AC44C6M No. 3323 was the first to be equipped with straight air by Wabtec at its Erie, Pa., plant before moving to CN’s shop in Proctor, Minn., for additional work prior to its first test run.
To date, No. 3323 is the only AC44C6M modified, with only a single round trip from Proctor and back in ore service on May 19. On May 28, the locomotive led it first train from Proctor down to the dock at Duluth using the straight air system. Canadian National will continue to work out the bugs in the straight air system on this locomotive in the coming months, presumably before additional locomotives are converted.
Canadian National plans for a unit reduction on each loaded ore train when AC power is implemented. This will reduce the current three-unit C40-8 consist on loaded ore trains to two AC44C6Ms setup in a 1×1 distributed power setup on trains to and from Two Harbors.
