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
Type and origin Builder Krauss Build date 1896 Total produced 1
Specifications Configuration: ​  • Whyte 4-2-2-2, later 4-4-0 Gauge 1,435 mm (4 ft 8+1⁄2 in) Leading dia. 1,006 mm (3 ft 3+5⁄8 in) Driver dia. 1,870 mm (6 ft 1+5⁄8 in) Length: ​  • Over beams 16,570 mm (54 ft 4+1⁄4 in) Axle load 14.9 t (14.7 long tons; 16.4 short tons) Adhesive weight 29.8 t (29.3 long tons; 32.8 short tons) Service weight 51.7 t (50.9 long tons; 57.0 short tons) Water cap. 14.5 m3 (3,200 imp gal; 3,800 US gal) Boiler pressure 13 kgf/cm2 (1.27 MPa; 185 lbf/in2) Heating surface:  • Firebox 2.26 m2 (24.3 sq ft)  • Evaporative 94.60 m2 (1,018.3 sq ft) Superheater: ​  • Heating area 26.85 m2 (289.0 sq ft) Cylinders 2 Cylinder size 490 mm (19+5⁄16 in) Piston stroke 610 mm (24 in)
Performance figures Maximum speed 90 km/h (56 mph)
Career Numbers K.Bay.Sts.E.: 1400 DRG: 36 861 Retired 1933

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