Buffalo, Rochester, & Pittsburgh Class LL / Baltimore & Ohio KK Class 2-6-6-2 "Mallet Mogul" Locomotive

The B&O KK class locomotives consisted of three separate classes of 2-6-6-2 articulated steam locomotives. A total of 57 locomotives were in the three classes. The B&O acquired 55 of these when they took over the Buffalo, Rochester and Pittsburgh.

Class KK-1
The B&O converted these to a 4-4-6-2 arrangement for passenger service, and converted them back soon afterward. They were retired in 1953.

Class: KK-1 Overview 
Railroad: Baltimore & Ohio (B&O) 
Wheel arrangement: 2-6-6-2
Number in Class: 1 
Road Number: 7400 
Gauge: Standard gauge 4 ft ​8 1⁄2 in (1,435 mm)
Number Built: 1 
Builder: Baldwin 
Year Built: 1930 
Valve Gear: Walschaert 
Driver Wheelbase: 34.92 ft / (10.64 m)
Engine Wheelbase: 56 ft (17.07 m)
Overall Wheelbase (engine & tender): 104.41 ft (31.82 m) 
Axle Loading (Maximum Weight per Axle): 63,700 lbs (28,894 kg)
Weight on Drivers: 372,000 lbs (168,737 kg)
Engine Weight: 465,000 lbs (210,921 kg) 
Tender Loaded Weight: 273,000 lbs (123,831 kg)
Total Engine and Tender Weight: 738,000 lbs (334,752 kg)
Tender Water Capacity: 18,000 gals (68.18 ML) 
Tender Fuel Capacity (coal): 20 tons (18.20 MT)
Minimum weight of rail (calculated): 103 lb/yd (51.50 kg/m)
Driver Diameter: 70 in. (1,778 mm)
Boiler Pressure: 250 psi (17.20 kPa) 
High Pressure Cylinders (dia x stroke): 23" x 30" (584 mm x 762 mm) 
Low Pressure Cylinders (dia x stroke): 37" x 32" (940 mm x 813 mm)
Tractive Effort: 96,354 lbs (43705.49 kg)
Factor of Adhesion: 3.86 
Firebox Area: 866 sq ft (80.45 m2)
Grate Area: 92 sq ft (8.55 m2)
Evaporative Heating Surface: 6,543  sq ft (607.86 m2)
Superheating Surface: 1,666 sq ft (154.78 m2)
Combined Heating Surface: 8,209 sq ft (762.64 m2)

Class KK-2 
This locomotive was built to compare with No. 7400.

Class: KK-2 Overview

Railroad: Baltimore & Ohio (B&O) 
Wheel arrangement: 2-6-6-2
Number in Class: 1
Road Number: 7450
Gauge: Standard gauge 4 ft ​8 1⁄2 in (1,435 mm)
Number Built: 1
Builder: Baldwin
Year: 1930
Valve Gear: Walschaert
Driver Wheelbase: 12.17 ft  (3.71 m)
Engine Wheelbase: 55.67 ft (16.97 m)
Overall Wheelbase (engine & tender): 104.41 ft (31.82 m)
Axle Loading (Maximum Weight per Axle): 63,700 lbs (28,894 kg)
Weight on Drivers: 373,000 lbs (169,190 kg)
Engine Weight: 466,000 lbs (211,374 kg)
Tender Loaded Weight: 273,000 lbs (123,831 kg)
Total Engine and Tender Weight: 739,000 lbs (335,205 kg)
Tender Water Capacity: 18,000 gals (68.18 ML)
Tender Fuel Capacity (coal): 20 tons (18.20 MT)
Minimum weight of rail (calculated): 104 lb/yd (52 kg/m)
Driver Diameter: 70 in (1,778 mm)
Boiler Pressure: 250 psi (17.20 kPa)
High Pressure Cylinders (dia x stroke): 23" x 30" (584 mm x 762 mm)
Low Pressure Cylinders (dia x stroke):37" x 32" (940 mm x 813 mm)
Tractive Effort: 96,354 lbs (43705.49 kg)
Factor of Adhesion: 3.87
Firebox Area: 432 sq ft (40.52 m2)
Grate Area: 92.30 sq ft (8.58 m2)
Evaporative Heating Surface: 5,471 sq ft (508.46 m2)
Superheating Surface: 1,698 sq ft / (157.81 m2)
Combined Heating Surface: 7,169 sq ft / (666.27 m2)

Class LL / KK-4 
Built at Alco's Schenectady and Brooks works from 1914 to 1923, all 55 locomotives were delivered with 14" (356 mm) piston valves serving the high pressure cylinders and slide valves supplying the low pressure cylinders. All used Walschaert's valve gear except for Nos. 7526-7540, which came from Brooks. Those fifteen units were equipped with Southern valve gear. All were retired by 1951.

Class: LL (BR&P) and KK-4 (B&O) Overview

Railroad: Buffalo, Rochester, & Pittsburgh (BR&P), Baltimore & Ohio (B&O)
Wheel arrangement: 2-6-6-2
Number in Class: 55
Road Numbers: BR&P 700-754, B&O 7500-7554
Gauge: Standard gauge 4 ft ​8 1⁄2 in (1,435 mm)
Number Built: 55
Builder: Alco-Schenectady
Year Built: 1914
Valve Gear: Walschaert or Southern
Driver Wheelbase: 10.33 ft (3.15 m)
Engine Wheelbase: 49.66 ft (15.14 m)
Overall Wheelbase (engine & tender): 86.48 ft (26.36 m)
Axle Loading (Maximum Weight per Axle): 68,000 lbs (30,844 kg)
Weight on Drivers: 367,500 lbs (166,695 kg)
Engine Weight: 445,000 lbs (201,849 kg)
Tender Loaded Weight: 205,600 lbs (93,259 kg)
Total Engine and Tender Weight: 650,600 lbs (295,108 kg)
Tender Water Capacity: 12,000 gals (45.45 ml)
Tender Fuel Capacity (coal): 14 tons (12.70 mt)
Minimum weight of rail (calculated): 102 lb/yd (51 kg/m)
Driver Diameter: 57 in (1448 mm)
Boiler Pressure: 200 psi (13.80 kp)
High Pressure Cylinders (dia x stroke): 23.5" x 32" (597 mm x 813 mm)
Low Pressure Cylinders (dia x stroke): 37" x 32" (940 mm x 813 mm)
Tractive Effort: 75,112 lbs (34,070.27 kg)
Factor of Adhesion: 4.89
Firebox Area: 388 sq ft (36.05 m2)
Grate Area: 72.20 sq ft (6.71 m2)
Evaporative Heating Surface: 4,935 sq ft (458.47 m2)
Superheating Surface: 1,046 sq ft (97.18 m2)
Combined Heating Surface: 5,981 sq ft (555.65 m2)
See also:

2-6-6-2 Locomotives

USRA 2-6-6-2 Locomotives

Buffalo, Rochester & Pittsburgh

Baltimore & Ohio Railroad

Steam Locomotives

Baltimore & Ohio KK-1 Class 2-6-6-2 No. 7400.

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