Bavarian AA I

The only AA I steam locomotive of the Royal Bavarian State Railways (Königlich Bayerische Staatsbahn) was built by the firm of Krauss in 1896. It had been designed by chief mechanical engineer, Richard von Helmholtz, as a 4-2-2-2 tender locomotive. The engine was largely based on the Bavarian B XI, but the driving and running gear was modified. The second coupled axle was replaced by a fixed carrying axle, and a dolly axle (Vorspannachse) added between the bogie and driving axle. This could be lowered by a pressure cylinder and was driven by an auxiliary engine with two cylinders. Despite her high maintenance requirement, she was economical to run due to her low steam consumption. In 1907 she was rebuilt after an accident into a 2'B h2 locomotive and redesignated as a Class P 2/4. She was taken over by the Deutsche Reichsbahn and run under operating number 36 861. She was the last Bavarian 4-4-0 locomotive to be retired in 1933.

Bavarian AA I later P 2/4 DRG Class 36.8
Number(s)	K.Bay.Sts.E.: 1400 DRG: 36 861
Quantity	1
Manufacturer	Krauss
Year(s) of manufacture	1896
Retired	1933
Wheel arrangement	4-2-2-2, later 4-4-0
Axle arrangement	2′aA1 n2v, later 2′B h2
Track gauge	1,435 mm (4 ft 8 1⁄2 in)
Length over buffers	16,570 mm (54 ft 4 1⁄4 in)
Service weight	51.7 t (50.9 long tons; 57.0 short tons)
Adhesive weight	29.8 t (29.3 long tons; 32.8 short tons)
Axle load	14.9 t (14.7 long tons; 16.4 short tons)
Top speed	90 km/h (56 mph)
Driving wheel diameter	1,870 mm (6 ft 1 5⁄8 in)
Leading wheel diameter	1,006 mm (3 ft 3 5⁄8 in)
No. of cylinders	2
Cylinder bore	490 mm (19 5⁄16 in)
Piston stroke	610 mm (24 in)
Boiler Overpressure	13 kgf/cm2 (1.27 MPa; 185 lbf/in2)
Grate area	2.26 m2 (24.3 sq ft)
Superheater area	26.85 m2 (289.0 sq ft)
Evaporative heating area	94.60 m2 (1,018.3 sq ft)
Tender	Bavarian 3 T 14.5
Water capacity	14.5 m3 (3,200 imp gal; 3,800 US gal)

The engine was equipped with a Bavarian 3 T 14.5 tender.