These locomotives were designed with 75" drivers, 26 x 32 cylinders, a 270 psi boiler pressure, a weight of 445,550 pounds and had a tractive effort of 66,000 pounds.
There are no survivors.
| Class | Qty | Road Numbers | Locomotive Weight | Year Built | Builder |
|---|---|---|---|---|---|
| N-20 | 10 | 4000-4009 | 344,500 lbs | 1926 | ALCO |
| N-20 | 8 | 4010-4017 | 342,000 lbs | 1928 | ALCO |
| N-20 | 3 | 4018-4020 | 338,700 lbs | 1930 | Soo |
Data from Soo 1942 Locomotive Diagrams supplied in August 2013 by Allen Stanley from his extensive Rail Data Exchange. See also Negative Order No. 1145, Lima Locomotive Works, Incorporated builder card supplied by Chris Hohl in his 3 January 2018 email pointing out the correct boiler pressure of 270 psi. Works numbers were 7753-7756 in January 1938.
Classic Northern from the late 1930s that carried its boiler and firebox on an frame that was integrally cast with both the cylinders and the air reservoirs. Piston valves measured a modest 12" (305 mm) in diameter. The Elesco Type E superheater included a dryer. In place of the commonly adopted feed water heaters, the O-20s used an Elesco Type SL-305 exhaust steam injector. The 1942 Soo diagram shows the combustion chamber, but doesn't show its heating surface area. The builder's card reported 47 sq ft (4.37 sq m) in arch tubes. Although the negative gave the engine weight as 445,550 lb (202,098 kg), later diagrams reflected greater weight on the trailing truck.
Drury (1993) says of these engines: "Assigned to fast Chicago-Twin Cities freight trains, [they] acquired a reputation for availability -- they were able to turn at the terminals and be on their way quickly." Each locomotive averaged 100,000 miles (161,000 km) per year.
Dieselization shortened the quartet's careers and all four were sold for scrap in December 1954.
| Principal Dimensions by Steve Llanso of Middle Run Media | |
|---|---|
| Class | O-20 |
| Locobase ID | 278 |
| Railroad | Minneapolis, St Paul & Sault Ste Marie (Soo) |
| Country | USA |
| Whyte | 4-8-4 |
| Number in Class | 4 |
| Road Numbers | 5000-5003 |
| Gauge | Std |
| Number Built | 4 |
| Builder | Lima |
| Year | 1938 |
| Valve Gear | Walschaert |
| Locomotive Length and Weight | |
| Driver Wheelbase (ft / m) | 19.75 / 6.02 |
| Engine Wheelbase (ft / m) | 46.75 / 14.25 |
| Ratio of driving wheelbase to overall engine wheelbase | 0.42 |
| Overall Wheelbase (engine & tender) (ft / m) | 87.79 / 26.76 |
| Axle Loading (Maximum Weight per Axle) (lbs / kg) | 65,900 / 29,892 |
| Weight on Drivers (lbs / kg) | 263,000 / 119,295 |
| Engine Weight (lbs / kg) | 453,500 / 205,704 |
| Tender Loaded Weight (lbs / kg) | 317,600 / 144,061 |
| Total Engine and Tender Weight (lbs / kg) | 771,100 / 349,765 |
| Tender Water Capacity (gals / ML) | 17,500 / 66.29 |
| Tender Fuel Capacity (oil/coal) (gals/tons / Liters/MT) | 24 / 22 |
| Minimum weight of rail (calculated) (lb/yd / kg/m) | 110 / 55 |
| Geometry Relating to Tractive Effort | |
| Driver Diameter (in / mm) | 75 / 1905 |
| Boiler Pressure (psi / kPa) | 270 / 1860 |
| High Pressure Cylinders (dia x stroke) (in / mm) | 26" x 32" / 660x813 |
| Tractive Effort (lbs / kg) | 66,194 / 30025.13 |
| Booster (lbs) | 13,400 |
| Factor of Adhesion (Weight on Drivers/Tractive Effort) | 3.97 |
| Heating Ability | |
| Tubes (number - dia) (in / mm) | 65 - 2.25" / 57 |
| Flues (number - dia) (in / mm) | 199 - 3.5" / 89 |
| Flue/Tube length (ft / m) | 21.50 / 6.55 |
| Firebox Area (sq ft / m2) | 423 / 39.30 |
| Grate Area (sq ft / m2) | 88.30 / 8.20 |
| Evaporative Heating Surface (sq ft / m2) | 5142 / 477.70 |
| Superheating Surface (sq ft / m2) | 2120 / 196.95 |
| Combined Heating Surface (sq ft / m2) | 7262 / 674.65 |
| Evaporative Heating Surface/Cylinder Volume | 261.55 |
| Computations Relating to Power Output (More Information) | |
| Robert LeMassena's Power Computation | 23,841 |
| Same as above plus superheater percentage | 30,755 |
| Same as above but substitute firebox area for grate area | 147,331 |
| Power L1 | 45,212 |
| Power MT | 1515.97 |