Soo Line B-4 class

4 ft 8+1⁄2 in (1,435 mm)Driver dia.51 in (1,295 mm)WheelbaseLoco: 11 ft 6 in (3.51 m)Length58 ft 10+3⁄8 in (17.94 m)Width10 ft 5 in (3.18 m)Height15 ft 3+1⁄2 in (4.66 m)Axle load51,500 lb (23.4 tonnes)Loco weight151,000 lb (68.5 tonnes)Tender weight102,900 lb (46.7 tonnes)Fuel typeCoalFuel capacity16,000 lb (7.3 tonnes)Water cap.5,000 US gal (19,000 L; 4,200 imp gal)Boiler pressure180 lbf/in² (1.24 MPa)CylindersTwo, outsideCylinder size20 in × 26 in (508 mm × 660 mm)Valve gearWalschaerts

Performance figures
Tractive effort	31,200 lbf (138.78 kN)

Career
Operators	Minneapolis, St. Paul and Sault Ste. Marie Railway (Soo Line)
Class	B-4
Number in class	11
Numbers	344–354
Preserved	#346; #353
Disposition	Two preserved, of which one is operational

The Soo Line B-4 class were 0-6-0 steam locomotives constructed for the Minneapolis, St. Paul and Sault Ste. Marie Railway (Soo Line) by the American Locomotive Company. Six (#344–349) were built at their Schenectady plant in 1915, with a further five (#350–354) being constructed by their Brooks plant in Dunkirk, New York, in 1920.

They were the last, and largest design of purpose-built switch engines that the Soo Line owned, any heavier switching duties were performed by down-graded 2-8-0 freight engines. All were still on the active roster in May 1953,^[1] but all had been retired by the end December 1954 when the railroad completed its dieselization.

Two are preserved^[2] - #346 from the first batch, which is displayed at the Wheels Across the Prairie Museum at Tracy, Minnesota, as Dakota, Minnesota and Eastern #9, and #353 from the second batch, which is operational and gives free rides annually at the Western Minnesota Steam Thresher's Reunion, Rollag, Minnesota.