Oldenburg P 4.2

The Oldenburg Class P 4.2 steam locomotives were German engines built for the Grand Duchy of Oldenburg State Railways (Großherzoglich Oldenburgische Staatseisenbahnen) between 1907 and 1909. They were based on the standard variant of the Prussian P 4.2, but there were a number of small differences such as a Ranafier steam dryer and, on three examples, a Lentz valve gear, a system widely used in Oldenburg. Production began in 1907 and eight engines were procured up to 1909.

Oldenburg P 4.2 DRG Class 36.12
Locomotive 190 Neptun (Hanomag 5410 of 1909)
Number(s)	GOE: 174–178, 188–190 DRG: 36 1251 - 36 1258
Quantity	8
Manufacturer	Hanomag
Year(s) of manufacture	1907–1909
Retired	1929
Wheel arrangement	4-4-0
Axle arrangement	2′B n2v
Track gauge	1,435 mm (4 ft 8 1⁄2 in)
Length over buffers	17,461 mm (57 ft 3 1⁄2 in)
Service weight	52.2 t (51.4 long tons; 57.5 short tons)
Adhesive weight	30.2 t (29.7 long tons; 33.3 short tons)
Axle load	15.1 t (14.9 long tons; 16.6 short tons)
Top speed	90 km/h (56 mph)
Indicated Power	427 kW (581 PS; 573 hp)
Driving wheel diameter	1,750 mm (68 7⁄8 in)
Leading wheel diameter	1,000 mm (39 3⁄8 in)
No. of cylinders	2
LP cylinder bore	680 mm (26 3⁄4 in)
HP cylinder bore	460 mm (18 1⁄8 in)
Piston stroke	600 mm (23 5⁄8 in)
Grate area	2.27 m2 (24.4 sq ft)
Evaporative heating area	119.35 m2 (1,284.7 sq ft)
Tender	pr 3 T 12 and 2′2′ T 20
Water capacity	16.0 m3 (3,500 imp gal; 4,200 US gal)

The engines taken over by the Deutsche Reichsbahn were grouped as DRG Class 36.12 given numbers 36 1251 to 36 1258.

The locomotives used tenders of the 3 T 12 or 2'2' T 20 classes.